A systematic review of the factors affecting accuracy of SUV measurements. AJR Am J Roentgenol. 2010;195:310-320. [PMID: 20651185 DOI: 10.2214/ajr.10.4923]

Performance of PSMA-PET/CT as verified by bone biopsy for diagnosing osseous metastases of prostate cancer

OBJECTIVE

Prostate-specific membrane antigen (PSMA)-PET/CT has shown considerable promise in the evaluation of prostate cancer bone metastases; however, data utilizing a histopathologic reference standard in this setting are limited. We therefore sought to evaluate the diagnostic performance of PSMA-PET/CT using a consistent histopathologic gold standard in the form of bone biopsy.

MATERIALS AND METHODS

In this single-center, retrospective study, we identified 80 patients with prostate cancer who underwent CT-guided bone biopsy of a tracer-avid osseous lesion on PSMA-PET/CT performed with 18F-piflufolastat. Concordance between PET/CT and histopathology and the positive predictive value of PSMA-PET/CT were determined. Factors predictive of positive biopsies were also evaluated.

RESULTS

PSMA-PET/CT and bone biopsy results were concordant in 55/80 patients (69%), and the positive predictive value of PSMA-PET/CT for osseous metastasis of prostate cancer was 66% (53/80). Positive predictive values for spine, pelvis, and rib biopsies were 82% (23/28), 72% (18/25), and 26% (5/19), respectively. Peak SUV and its ratio to liver mean SUV were significantly higher in biopsy-positive lesions compared to biopsy-negative lesions. A threshold peak SUV to liver mean SUV ratio of 1.7 had a sensitivity of 61% and a specificity of 92% for a histopathologic diagnosis of metastatic prostate cancer.

CONCLUSION

PSMA-PET/CT has a moderately high histopathologic concordance and positive predictive value for the diagnosis of osseous metastatic disease in prostate cancer. Peak SUV is useful for distinguishing biopsy-positive from biopsy-negative lesions. In keeping with prior investigations, a majority of biopsied rib lesions were negative for metastatic prostate cancer.

Test-retest repeatability of quantitative organ and tissue uptake using 20-minute dynamic multiparametric whole-body [18F]FDG PET/CT in patients with type 2 diabetes

BACKGROUND

Recently developed dynamic whole-body PET/CT (D-WB PET/CT) protocols allow for measurements of potentially more precise metabolic parameters than the commonly used semiquantitative SUV. Most notable is the metabolic rate of FDG uptake (MRFDG), which reflects quantitative glucose uptake into tissues and organs. However, data on the reproducibility of MRFDG measurements are scarce, particularly in patients with perturbed glucose homeostasis such as type 2 diabetes. We therefore aimed to evaluate the test-retest repeatability of both MRFDG and SUV in these patients.

RESULTS

Fifteen participants (mean age 71 ± 7 years; 2 females) with type 2 diabetes underwent a short 20-minute [18F]FDG D-WB PET/CT after 6 h fasting on two consecutive days. Both SUV and MRFDG images were reconstructed from D-WB PET/CT data obtained 60-80 min post-injection of [18F]FDG. MRFDG and SUV data were measured in organs and tissues, and repeatability was assessed with Bland-Altman analysis, intraclass correlation coefficients (ICC), repeatability coefficients (RPC) and coefficients of variation (wCV). There was high repeatability of both SUVmean and MRFDG-mean in all measured organs (ICC range: 0.65-0.95 for SUVmean and 0.66-0.94 for MRFDG-mean). SUVmean generally demonstrated higher reliability (ICC) and lower variability (%RPC and %wCV) when compared to MRFDG-mean. However, MRFDG test-retest variation was < 19% in most analysed tissues, demonstrating that MRFDG may be used as a precise marker of treatment response.

CONCLUSION

This study demonstrates that MRFDG calculated from D-WB PET/CT exhibit high repeatability, comparable to SUVs across most organs in patients with type 2 diabetes.

Metabolic characterization and radiomics-based composite model for breast cancer immune microenvironment types using 18F-FDG PET/CT

PURPOSE

The intricateness of tumor immune microenvironment types (TIMTs) complicates identifying responders to immune checkpoint inhibitors (ICIs). Our purpose was to explore the metabolic characteristics of TIMTs in breast cancer using 18F-fluorodeoxyglucose (FDG) PET/CT and to establish radiomics-based predictive models for TIMTs.

METHODS

Consecutive 207 breast cancer patients (211 primary lesions), who underwent 18F-FDG PET/CT examination from Sep 2022 to Aug 2024 in our hospital, were retrospectively reviewed. The programmed death-ligand 1 (PD-L1) and tumor-infiltrating lymphocytes (TILs) were evaluated for TIMTs: TMIT-I (PD-L1-, TILs-), TMIT-II (PD-L1+, TILs+), TMIT-III (PD-L1-, TILs+), and TMIT-IV (PD-L1+, TILs-). The relationship between metabolic parameters (such as maximum standardized uptake value (SUVmax) and tumor-to-liver SUV ratio (TLR)) and TIMTs was analyzed. Then composite predictive models based on radiomics were further developed.

RESULTS

TIMT-II represented the highest proportion in HER2+ (14/22, 64%) and triple-negative (17/27, 63%) breast cancer. Most metabolic parameters (such as SUVmax and TLR) exhibited significant differences in TIMT-II vs. -I or TIMT-II vs. -III (P < 0.05). TLR (P = 0.03; OR: 1.1) and Nottingham grade (P = 0.006; OR: 3.1) were independent impact factors of TIMT-II. We further developed a composite model that integrated radiomics, metabolic parameter, and clinicopathological data, which demonstrated promising predictive efficacy for TIMT-II (AUC testing set = 0.86).

CONCLUSION

Metabolic differences existed among different TIMTs, with TIMT-II exhibiting markedly elevated metabolic characteristics. The composite model based on radiomics demonstrated high predictive efficacy for TIMT-II and has the potential to screen ICIs responders.

Impact of intraprostatic PSMA maximum standardised uptake value following prostatectomy: a systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis to assess the relationship between intraprostatic maximum standardised uptake value (SUVmax) of the dominant prostatic lesion as measured on preoperative prostate-specific membrane antigen (PSMA) positron emission tomography (PET) with radical prostatectomy International Society of Urological Pathology (ISUP) Grade Group, pathological tumour (pT) staging, and biochemical recurrence (BCR).

METHODS

Prostate-specific membrane antigen PET may offer non-invasive assessment of histopathological and oncological outcomes before definitive treatment. SUVmax of the dominant lesion has been explored as a prognostic biomarker. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, we performed reviews of digital libraries and databases and retrieved studies reporting SUVmax quantified on PSMA PET computed tomography or magnetic resonance imaging and subsequent radical prostatectomy ISUP Grade Group, pT stage, and BCR. Quality assessment was performed using Quality Assessment of Diagnostic Accuracy Studies-2 and Prediction model Risk of Bias Assessment tools. Random effects meta-analysis and meta-regression by ISUP Grade Group and pT2 vs pT3/4 stage was performed. This study was registered on the International Prospective Register of Systematic Reviews (PROSPERO: CRD42023408170).

EVIDENCE SYNTHESIS

After removing duplicates, 23 studies were included for review. Pooled SUVmax (95% confidence interval [CI]) increased monotonically with advancing ISUP Grade Group, with ISUP 1: 5.8 (95% CI 3.9-7.7), through to ISUP 5: 17.3 (95% CI 13.1-21.5). For pT2 disease, pooled SUVmax: 9.7 (95% CI 7.8-11.5) increasing to 13.8 (95% CI 10.9-16.7) for pT3/4 disease. Substantial inconsistency was noted (I2 >50%) for all subgroups. This was not attenuated by restricting analysis only to studies using [68Ga]Ga-PSMA-11. Narrative synthesis of six papers reporting BCR showed increasing SUVmax was associated with reduced time to BCR.

CONCLUSION

Preoperative intraprostatic PSMA SUVmax increases monotonically with higher ISUP Grade Group and pathological tumour stage. Higher SUVmax is associated with reduced BCR-free survival. However, the use of single SUVmax thresholds for clinical decision making is not recommended as variability between studies is high.

Enhancing 18F-FDG PET image quality and lesion diagnostic performance across different body mass index using the deep progressive learning reconstruction algorithm

BACKGROUND

As body mass index (BMI) increases, the quality of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG) positron emission tomography (PET) images reconstructed with ordered subset expectation maximization (OSEM) declines, negatively impacting lesion diagnostics. It is crucial to identify methods that ensure consistent diagnostic accuracy and maintain image quality. Deep progressive learning (DPL) algorithm, an Artificial Intelligence(AI)-based PET reconstruction technique, offers a promising solution.

METHODS

150 patients underwent 18F-FDG PET/CT scans and were categorized by BMI into underweight, normal, and overweight groups. PET images were reconstructed using both OSEM and DPL and their image quality was assessed both visually and quantitatively. Visual assessment employed a 5-point Likert scale to evaluate overall score, image sharpness, image noise, and diagnostic confidence. Quantitative assessment parameters included the background liver image-uniformity-index ([Formula: see text]) and signal-to-noise ratio ([Formula: see text]). Additionally, 466 identifiable lesions were categorized by size: sub-centimeter and larger. We compared maximum standard uptake value ([Formula: see text]), signal-to-background ratio ([Formula: see text]), [Formula: see text], contrast-to-background ratio ([Formula: see text]), and contrast-to-noise ratio ([Formula: see text]) of these lesions to evaluate the diagnostic performance of the DPL and OSEM algorithms across different lesion sizes and BMI categories.

RESULTS

DPL produced superior PET image quality compared to OSEM across all BMI groups. The visual quality of DPL showed a slight decline with increasing BMI, while OSEM exhibited a more significant decline. DPL maintained a stable [Formula: see text] across BMI increases, whereas OSEM exhibited increased noise. In the DPL group, quantitative image quality for overweight patients matched that of normal patients with minimal variance from underweight patients. In contrast, OSEM demonstrated significant declines in quantitative image quality with rising BMI. DPL yielded significantly higher contrast ([Formula: see text], [Formula: see text],[Formula: see text]) and [Formula: see text] than OSEM for all lesions across all BMI categories.

CONCLUSION

DPL consistently provided superior image quality and lesion diagnostic performance compared to OSEM across all BMI categories in 18F-FDG PET/CT scans. Therefore, we recommend using the DPL algorithm for 18F-FDG PET/CT image reconstruction in all BMI patients.

Prognostic 18F-flotufolastat PET parameters for outcome assessment of 177Lu-labeled PSMA-targeted radioligand therapy in metastatic castration-resistant prostate cancer

PURPOSE

This retrospective analysis evaluates baseline 18F-flotufolastat positron emission tomography (PET) parameters as prognostic parameters for treatment response and outcome in patients with metastatic castration-resistant prostate cancer (mCRPC) undergoing treatment with [177Lu]Lu-PSMA-I&T.

METHODS

A total of 188 mCRPC patients with baseline 18F-flotufolastat PET scans were included. Tumor lesions were semiautomatically delineated, with imaging parameters including volume-based and standardized uptake value (SUV)-based metrics. Outcome measures included prostate-specific antigen (PSA) response, PSA-progression-free survival (PSA-PFS), and overall survival (OS). Univariate and multivariate regression analyses assessed the impact of baseline imaging and pretherapeutic clinical parameters on outcome. Event time distributions were estimated with the Kaplan-Meier method, and groups were compared with log-rank tests.

RESULTS

Significant prognostic parameters for PSA response and PSA-PFS included log-transformed whole-body SUVmax (odds ratio (OR), 3.26, 95% confidence interval (CI), 2.01-5.55 and hazard ratio (HR), 0.51, 95% CI, 0.4-0.66; both p < 0.001) and prior chemotherapy (OR 0.3, 95% CI, 0.12-0.72 and HR 1.64, 95% CI, 1.07-2.58; p = 0.008 and p = 0.028, respectively). For OS, significant prognosticators were the following log-transformed parameters: number of lesions (HR 1.38, 95% CI, 1.24-1.53; p < 0.001), TTV (HR 1.27, 95% CI, 1.18-1.37; p < 0.001), and ITLV (HR 1.24, 95% CI, 1.16-1.33; p < 0.001), with log-transformed TTV (HR 1.15, 95% CI, 1.04-1.27; p = 0.008) remaining significant in multivariate analysis.

CONCLUSION

At baseline, SUV-based 18F-flotufolastat PET metrics (e.g., whole-body SUVmax) serve as significant positive prognosticators for short-term outcomes (PSA response and PSA-PFS). In contrast, volume-based metrics (e.g., TTV) are significant negative prognosticators for long-term outcome (OS), in mCRPC patients treated with [177Lu]Lu-PSMA-I&T.

Whole-body and site specific [18F]FDG uptake patterns on PET/CT have limited value in differentiating between polymyalgia rheumatica and other inflammatory diseases: two cohorts of treatment-naïve suspected polymyalgia rheumatica

BACKGROUND

It has been hypothesized that 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) positron emission tomography (PET) computed tomography (CT) can distinguish polymyalgia rheumatica (PMR) from non-PMR patients based on the [18F]FDG-uptake patterns. Nevertheless, a comprehensive assessment of whole-body [18F]FDG-patterns across all uptaking musculoskeletal sites, as well as site-specific [18F]FDG-uptake patterns, has not been conducted. Therefore, this study aimed to investigate both the overall whole-body [18F]FDG-uptake patterns and the specific uptake patterns at individual sites in patients suspected of having PMR.

METHODS

Two distinct cohorts of patients with suspected PMR from Denmark and the Netherlands were prospectively included, encompassing 66/27 and 36/21 PMR/non-PMR patients, respectively. The cohorts consisted of treatment-naïve patients, who underwent pre-treatment [18F]FDG-PET/CT scans. The [18F]FDG-uptake was then assessed across 34 different anatomical sites. Furthermore, the site-specific [18F]FDG-uptake pattern within each anatomical site was categorized according to its shape.

RESULTS

Patients with PMR were more likely than non-PMR patients to have bilateral [18F]FDG-uptake equal to or above liver compared at the ischial tuberosities (91%/41%), shoulder joints (86%/45%), hip joints (83%/52%), and along the lumbar spinal processes (70%/30%). However, a subgroup analysis comparing non-PMR patients with other inflammatory conditions to patients with PMR revealed that several non-PMR patients exhibited a similar whole-body [18F]FDG-uptake pattern. Furthermore, site-specific [18F]FDG-uptake patterns were similar in patients with PMR and non-PMR.

CONCLUSION

Assessing whole-body or site-specific [18F]FDG-uptake patterns does not improve the diagnostic accuracy in distinguishing PMR from other inflammatory diseases. Consequently, [18F]FDG-PET/CT should mainly be used to rule out a clinical diagnosis of PMR.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT04519580). Registered 17th of August 2020.

Prognostic [68Ga]Ga-PSMA-11 PET Biomarkers for [177Lu]Lu-PSMA Radioligand Therapy in Metastatic Castrate-Resistant Prostate Cancer (Asian Population Study)

AIMS

Gallium-68 (68Ga) prostate-specific membrane antigen (PSMA) ([68Ga]Ga-PSMA-11) directed PET/CT reflects PSMA expression at metastatic sites and can hence be a surrogate of lutetium-177 (177Lu) PSMA ([177Lu]Lu-PSMA) radiation delivery. This retrospective analysis aims to explore the association between quantitative baseline [68Ga]Ga-PSMA-11 PET imaging biomarkers and treatment outcomes in our Asian cohort.

METHODS

We included patients with progressive metastatic castrate-resistant prostate cancer (mCRPC) who received [177Lu]Lu-PSMA radioligand therapy at our institution. The association between baseline [68Ga]Ga-PSMA-11 PET parameters (SUVmax, SUVmean, total tumor volume [PSMA-TV], total lesion uptake [PSMA-TLU = PSMA-TV × SUVmean], and total lesion quotient [PSMA-TLQ = PSMA-TV / SUVmean]) and overall survival (OS), prostate specific antigen (PSA) progression free survival (PFS), PSA response, and toxicity were analyzed using univariate analysis. Optimal cut-points were also explored.

RESULTS

Between May 9, 2018 and October 7, 2024, 71 of 84 screened patients were eligible. The median whole-body SUVmean in our cohort was 8.04. Higher PSMA-TLQ and PSMA-TV (per 10-unit increment) were associated with shorter OS (HR 1.005; HR 1.005) and shorter PSA PFS (HR 1.005; HR 1.004). A higher PSMA-TLQ was also associated with poorer odds of PSA response (OR 0.994). Conversely, higher SUVmean was associated with longer PSA PFS (HR 0.911) and improved odds of PSA response (OR 1.34). Higher PSMA-TV (per 10-unit increment) and PSMA-TLU (per 100-unit increment) were associated with increased hematological toxicity (OR 1.008; OR 1.012).

CONCLUSION

PSMA-TLQ and PSMA-TV were negative prognostic markers and SUVmean was a positive prognostic marker among Asian patients with mCRPC who received [177Lu]Lu-PSMA radioligand therapy.

Comparison of 18F-FDG PET image quality and quantitative parameters between DPR and OSEM reconstruction algorithm in patients with lung cancer

OBJECTIVES

The present study aimed to investigate the influence of the deep progressive learning reconstruction (DPR) algorithm on the 18F-FDG PET image quality and quantitative parameters.

METHODS

In this retrospective study, data were collected from 55 healthy individuals and 184 patients with primary malignant pulmonary tumors who underwent 18F-FDG PET/CT examinations. PET data were reconstructed using the ordered subset expectation maximization (OSEM) and DPR algorithms. The influence of DPR algorithm on quantitative parameters was explored, including the SUVmax, SUVmean, standard deviation of SUV (SUVSD), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and tumor-to-background uptake ratio (TBR). Finally, the differences in image quality parameters, including signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), between the two reconstruction algorithms were evaluated.

RESULTS

DPR algorithm significantly reduced the SUVmax and SUVSD of background tissues (all, P < 0.001) compared to OSEM algorithm, while no statistical difference was observed in SUVmean between the two algorithms (all, P > 0.05). DPR algorithm notably increased the SUVmax, SUVmean, and TBR of lesions (all, P < 0.001) and reduced MTV (P = 0.005), with minimal differences in TLG noted between the reconstruction algorithms (P < 0.001). The percentage differences in SUVmax (P = 0.001), SUVmean (P = 0.005), and TBR (P = 0.001) between the two algorithms were significantly higher in solid nodules than in pure ground glass nodules (pGGNs). The ΔCNR between solid nodules (P = 0.031) and mixed ground glass nodules (P = 0.020) was greater than that between pGGNs. SNR and CNR obtained using the DPR algorithm were markedly improved compared to those determined using the OSEM algorithm (all, P < 0.001).

CONCLUSION

Under identical acquisition conditions, the DPR algorithm enhanced the accuracy of quantitative parameters in pulmonary lesions and potentially improved lesion detectability. The DPR algorithm increased image SNR and CNR compared to those obtained using the OSEM algorithm, significantly optimizing overall image quality. This advancement facilitated precise clinical diagnosis, underpinning its potential to significantly contribute to the field of medical imaging.

Increased rates of [18F]FDG accumulation in the brain in children could lead to a lower amount of [18F]FDG reaching other organs and tumors: Is a new SUV correction factor that considers [18F]FDG uptake of the brain in children necessary?

OBJECTIVE

[18F]FDG uptake in the livers and tumors of children is lower than that of adults. The brain exhibits intense physiological [18F]FDG uptake. In childhood, the ratio of brain weight to body height and the ratio of brain weight to body weight are higher than those of adults. We hypothesized that in children, most of the [18F]FDG would be retained in the brain, resulting in less [18F]FDG activity reaching other organs and tumor tissues.

METHODS

The [18F]FDG PET/CT images of 56 pediatric and 24 adult patients were evaluated retrospectively. Patients were divided into four age groups: 1) 3-7 years old, 2) 8-12 years old, 3) 13-17 years old, and 4) over 18 years old. Accumulated [18F]FDG activity in the brain, liver, and whole body (WB) was calculated using the manually drawn volumes of interest for all patients using NUKDOS software. Also, SUV normalized to total body weight (SUVbw) and SUV normalized to lean body mass (SUVlbm) of the liver were calculated using the NUKDOS software.

RESULTS

The mean [18F]FDG accumulation ratio of brain-to-WB was significantly higher in patients aged 3-7 years and 8-12 years than in adults. Brain/WB [18F]FDG activity ratio was lower in the 13-17 age group compared to the 3-7 age group (P = .0001). The accumulated [18F]FDG activity ratio of liver-to-WB in the 3-7 age group was significantly lower than in adults when comparing the four groups (P = .0001). The mean of liver SUVbw was statistically lower in the 3-7 and 8-12 age groups than in the 13-17 and adult groups. Patients aged 3-7 years had a significantly lower mean liver SUVlbm than those in the other age groups. The mean liver SUVlbm was also significantly lower in the 8-12 years and 13-17 years age groups than in adults. There was a negative correlation between blood glucose levels and the amount of [18F]FDG in the brain. However, no statistically significant correlation existed between blood glucose and age.

CONCLUSION

We showed that the [18F]FDG accumulation rate was higher in the brain and lower in the liver in the children when compared to adults. Our findings suggest that increased uptake of [18F]FDG in children's brains may lead to reduced activity reaching other organs and tumor tissue. To improve diagnostic accuracy, adapted SUV correction protocols can be developed for pediatric populations, considering age-related changes in [18F]FDG uptake ratio of the brain.

Meta-analysis of [18F]FDG-PET/CT in pulmonary sarcoidosis

BACKGROUND

18F-Fluorodeoxyglucose (FDG) PET/CT is emerging as a tool in the diagnosis and evaluation of pulmonary sarcoidosis, however, there is limited consensus regarding its diagnostic performance and prognostic value.

METHOD

A meta-analysis was conducted with PubMed, Science Direct, MEDLINE, Scopus, and CENTRAL databases searched up to and including September 2023. 1355 studies were screened, with seventeen (n = 708 patients) suitable based on their assessment of the diagnostic performance or prognostic value of FDG-PET/CT. Study quality was assessed using the QUADAS-2 tool. Forest plots of pooled sensitivity and specificity were generated to assess diagnostic performance. Pooled changes in SUVmax were correlated with changes in pulmonary function tests (PFT).

RESULTS

FDG-PET/CT in diagnosing suspected pulmonary sarcoidosis (six studies, n = 400) had a pooled sensitivity of 0.971 (95%CI 0.909-1.000, p = < 0.001) and specificity of 0.873 (95%CI 0.845-0.920)(one study, n = 169). Eleven studies for prognostic analysis (n = 308) indicated a pooled reduction in pulmonary SUVmax of 4.538 (95%CI 5.653-3.453, p = < 0.001) post-treatment. PFTs displayed improvement post-treatment with a percentage increase in predicted forced vital capacity (FVC) and diffusion capacity of the lung for carbon monoxide (DLCO) of 7.346% (95%CI 2.257-12.436, p = 0.005) and 3.464% (95%CI -0.205-7.132, p = 0.064), respectively. Reduction in SUVmax correlated significantly with FVC (r = 0.644, p < 0.001) and DLCO (r = 0.582, p < 0.001) improvement.

CONCLUSION

In cases of suspected pulmonary sarcoidosis, FDG-PET/CT demonstrated good diagnostic performance and correlated with functional health scores. FDG-PET/CT may help to guide immunosuppression in cases of complex sarcoidosis or where treatment rationalisation is needed.

CLINICAL RELEVANCE STATEMENT

FDG-PET/CT has demonstrated a high diagnostic performance in the evaluation of suspected pulmonary sarcoidosis with radiologically assessed disease activity correlating strongly with clinically derived pulmonary function tests.

KEY POINTS

In diagnosing pulmonary sarcoidosis, FDG-PET/CT had a sensitivity and specificity of 0.971 and 0.873, respectively. Disease activity, as determined by SUVmax, reduced following treatment in all the included studies. Reduction in SUVmax correlated with an improvement in functional vital capacity, Diffusion Capacity of the Lungs for Carbon Monoxide, and subjective health scoring systems.

Predictive value of 18F-fluorodeoxyglucose uptake for axillary lymph node metastasis in operable breast cancer: impact of molecular subtypes

OBJECTIVES

To evaluate the predictive value of standardized uptake value (SUV) in both primary tumors and axillary lymph nodes (ALNs) using FDG PET/CT for lymph node metastasis in breast cancer patients, and to assess the influence of molecular subtypes on this predictive performance.

METHODS

This retrospective study included 287 patients with invasive ductal carcinoma (IDC) who underwent FDG PET/CT prior to surgery between September 2016 and December 2019. The maximum standardized uptake value (SUVmax) of primary tumors (SUV-B) and ALNs (SUV-LN) were analyzed. Molecular subtypes were classified as hormone receptor-positive, HER2-positive, and triple-negative breast cancer (TNBC). Receiver operating characteristic (ROC) curve analysis was performed to assess and compare the diagnostic performance of SUV-B and SUV-LN for predicting ALN metastasis.

RESULTS

Among the 287 patients, 62 (21.6%) had confirmed ALN metastasis. The median SUV-LN was significantly higher in patients with metastasis compared to those without metastasis (1.5 vs. 0.9; P < 0.001). SUV-LN demonstrated good discriminative performance for ALN metastasis (AUC: 0.796), whereas SUV-B did not show significant predictive value (AUC: 0.536). The SUV_LN demonstrated significantly lower predictive performance for ALN metastasis in the hormone-positive group (AUC: 0.796) compared to the excellent discriminative performance in the HER2-positive (AUC: 0.923, P = 0.018) and TNBC (AUC: 0.940, P = 0.004) groups. Hormone receptor-positive tumors also exhibited lower FDG uptake in metastatic lymph nodes compared to HER2-positive and TNBC subtypes (P = 0.031).

CONCLUSION

FDG PET/CT SUV-LN effectively predicts ALN metastasis in HER2-positive and TNBC subtypes. Hormone receptor-positive breast cancers show lower FDG uptake in metastatic ALNs, reducing diagnostic accuracy. This finding may aid in selecting the most appropriate diagnostic modality based on tumor characteristics in the era of personalized medicine.

Novel PET-CT-MR Imaging Based Quantitative Technique for Accurate Assessment of Radiation Induced Injuries

Radiation-induced injuries (RIIs) are significant complications of radiation therapy used in cancer treatments and affect organs in a systemic fashion such as the heart, lungs, liver, and bone marrow. Such ionizing radiation leads to inflammation, fibrosis, and/or irreparable DNA damage, each of which can significantly impact patient's quality of life, underscoring the need for advanced diagnostic and imaging techniques. A novel combination of PET/Computed Tomography (CT) with Quantitative MR Imaging has emerged as a crucial tool for early diagnosis and timely evaluation of RIIs. This review focuses on the important role of quantitative PET-CT-MR imaging in diagnosing and monitoring RIIs.

Hypoxia Imaging in Lung Cancer: A PET-Based Narrative Review for Clinicians and Researchers

Background: Hypoxia plays a critical role in lung cancer progression and treatment resistance by contributing to aggressive tumor behavior and poor therapeutic response. Molecular imaging, particularly positron emission tomography (PET), has become an essential tool for noninvasive hypoxia detection, providing valuable insights into tumor biology and aiding in personalized treatment strategies. Objective: This narrative review explores recent advancements in PET imaging for detecting hypoxia in lung cancer, with a focus on the development, characteristics, and clinical applications of various radiotracers. Findings: Numerous PET-based hypoxia radiotracers have been investigated, each with distinct pharmacokinetics and imaging capabilities. Established tracers such as 18F-Fluoromisonidazole (18F-FMISO) remain widely used, while newer alternatives like 18F-Fluoroazomycin Arabinoside (18F-FAZA) and 18F-Flortanidazole (18F-HX4) demonstrate improved clearance and image contrast. Additionally, 64Cu-ATSM has gained attention for its rapid tumor uptake and hypoxia selectivity. The integration of PET with hybrid imaging modalities, such as PET/CT and PET/MRI, enhances the spatial resolution and functional interpretation, making hypoxia imaging a promising approach for guiding radiotherapy, chemotherapy, and targeted therapies. Conclusions: PET imaging of hypoxia offers significant potential in lung cancer diagnosis, treatment planning, and therapeutic response assessment. However, challenges remain, including tracer specificity, quantification variability, and standardization of imaging protocols. Future research should focus on developing next-generation radiotracers with enhanced specificity, optimizing imaging methodologies, and leveraging multimodal approaches to improve clinical utility and patient outcomes.

Mediastinal staging lymph node probability map in non-small cell lung cancer

BACKGROUND

Mediastinal lymph node (LN) staging is routinely performed using PET/CT and EBUS-TBNA. Promising predictive algorithms for lymph nodes have been reported for each technique, both individually and in combination. This study aims to develop a predictive algorithm that combines EBUS, PET/CT and clinical data to provide a probability of malignancy.

METHODS

A retrospective study was conducted on consecutive patients with non-small cell lung carcinoma staged using PET/CT and EBUS-TBNA. Lymph nodes were identified by level (N1, N2, and N3) and anatomical region (AR) (subcarinal, paratracheal, and hilar). A Standardized Uptake Value (SUV) was determined for each sampled LN. The ultrasound features collected included diameter in the short axis (DSA), morphology, border, echogenicity and the presence of the vascular hilum. A robust logistic regression model was used to construct an algorithm to estimate the probability of malignancy of the lymph node.

RESULTS

A total of 116 patients with a mean age of 66, 93% of whom were men, were included. 358 lymph nodes were evaluated, 51% of which exhibited adenocarcinoma and 35% were squamous, while 14% were classified as non-small-cell lung carcinoma. The model estimated the probability of malignancy for each lymph node using age, DSA, SUVmax, and AR. The Area Under the ROC curve, was 0.89. A user-friendly application was also developed ( https://ubidi.shinyapps.io/lymma/ .) CONCLUSIONS: The integration of patient clinical characteristics, EBUS features, and PET/CT findings may generate a pre-sampling malignancy probability map for each lymph node. The model requires prospective and external validation.

Multimodal feature-guided diffusion model for low-count PET image denoising

BACKGROUND

To minimize radiation exposure while obtaining high-quality Positron Emission Tomography (PET) images, various methods have been developed to derive standard-count PET (SPET) images from low-count PET (LPET) images. Although deep learning methods have enhanced LPET images, they rarely utilize the rich complementary information from MR images. Even when MR images are used, these methods typically employ early, intermediate, or late fusion strategies to merge features from different CNN streams, failing to fully exploit the complementary properties of multimodal fusion.

PURPOSE

In this study, we introduce a novel multimodal feature-guided diffusion model, termed MFG-Diff, designed for the denoising of LPET images with the full utilization of MRI.

METHODS

MFG-Diff replaces random Gaussian noise with LPET images and introduces a novel degradation operator to simulate the physical degradation processes of PET imaging. Besides, it uses a novel cross-modal guided restoration network to fully exploit the modality-specific features provided by the LPET and MR images and utilizes a multimodal feature fusion module employing cross-attention mechanisms and positional encoding at multiple feature levels for better feature fusion.

RESULTS

Under four counts (2.5%, 5.0%, 10%,  and 25%), the images generated by our proposed network showed superior performance compared to those produced by other networks in both qualitative and quantitative evaluations, as well as in statistical analysis. In particular, the peak-signal-to-noise ratio of the generated PET images improved by more than 20% under a 2.5% count, the structural similarity index improved by more than 16%, and the root mean square error reduced by nearly 50%. On the other hand, our generated PET images had significant correlation (Pearson correlation coefficient, 0.9924), consistency, and excellent quantitative evaluation results with the SPET images.

CONCLUSIONS

The proposed method outperformed existing state-of-the-art LPET denoising models and can be used to generate highly correlated and consistent SPET images obtained from LPET images.

Impact of Uptake Period on 18F-DCFPyL-PSMA PET/CT Maximum Standardised Uptake Value

BACKGROUND

The maximum standardised uptake value (SUVmax) can potentially be affected by the uptake period during PSMA PET imaging. The optimal image acquisition period for 2-(3-{1-carboxy-5-[(6-18F-fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (18F-DCFPyL)PSMA PET/CT is yet to be established. This study aims to evaluate the effect of the uptake period on the SUVmax in diagnosing localised, clinically significant prostate cancer using 18F-DCFPyL-PSMA PET/CT.

METHODS

Sixty biopsy-naive men with one or more PI-RADS 4 or 5 lesions of at least 10 mm on multiparametric MRI (mpMRI) were enrolled to undergo 18F-DCFPyL-PSMA PET/CT. SUVmax was prospectively measured following an uptake period of 60, 90 and 120 min post injection of 18F-DCFPyL-PSMA radiotracer. Concordance with biopsy results or final histopathology was recorded.

RESULTS

Mean absolute differences in SUVmax at 60 vs. 90, 60 vs. 120, and 90 vs. 120 min uptake periods were 3.23 (SD 4.76), 4.53 (SD 7.33), and 3.24 (SD 4.56), respectively. This represents a statistically significant systematic increase in SUVmax (p-value < 0.001) with increasing uptake period. The interval between the uptake period of 60 vs. 120 min represented the largest SUVmax change of 29.98%.

CONCLUSIONS

The SUVmax is a dynamic variable significantly affected by uptake period. Our study supports image acquisition at 120 min following injection of 18F-DCFPyL radiotracer. Further studies are needed to determine if this acquisition period can be applied to other Fluorine-18 based PSMA radiotracers.

Exploring the Flare Phenomenon in Patients with Castration-Resistant Prostate Cancer: Enzalutamide-Induced PSMA Upregulation Observed on PSMA PET

Androgen receptor-targeting agents, particularly enzalutamide, show promise in enhancing prostate cancer diagnostic and therapeutic strategies by modulating prostate-specific membrane antigen (PSMA). Methods: A retrospective clinical cohort study investigated 9 men with metastatic castration-resistant prostate cancer on enzalutamide. PSMA PET/CT scans were obtained before and after enzalutamide initiation to assess PSMA expression changes. Lesions and organs at risk were evaluated visually and semiquantitatively. The flare phenomenon was characterized by a significant increase (≥20%) in the SUVmax of existing lesions or the appearance of new PSMA-positive lesions. Results: Exposure to enzalutamide led to a significant PSMA expression increase in 56% of assessed lesions (n = 42), with new lesions detected in 1 patient (11%). PSMA expression in organs at risk remained largely unaffected, indicating a tumor-specific response. Conclusion: Enzalutamide induces PSMA upregulation in metastatic castration-resistant prostate cancer, potentially enhancing diagnostic and therapeutic strategies. Further exploration of the flare phenomenon's clinical implications is warranted.

Current insights on PSMA PET/CT in intermediate-risk prostate cancer: a literature review

The purpose of this systematic review was to evaluate the role of PSMA PET/CT in intermediate-risk prostate cancer (PCa) patients, to determine whether it could help improve treatment strategy and prognostic stratification. A systematic literature search up to May 2024 was conducted in the PubMed, Embase and Scopus databases. Articles with mixed risk patient populations, review articles, editorials, letters, comments, or case reports were excluded. The quality of the papers was assessed by using the CASP criteria. The literature search returned 1111 studies; however, 1105 articles were excluded, and therefore 6 full-text papers were retrieved for the final analysis. Three out of six papers focused on the utility of SUVmax in identifying high ISUP grade in patients with intermediate-risk PCa. The latest three papers discussed the controversial role of PSMA PET/CT in predicting the lymph node involvement, mainly in the case of favorable subset. PSMA PET has completely changed the management of patients with PCa; indeed its role is still undefined in patients with intermediate-risk disease. Future perspective is to investigate larger cohorts of intermediate-risk PCa patients, to fully recognize the added value offered by PSMA PET in this category of subjects.

Predictive Value of Preoperative Maximum Standardized Uptake Value (SUVmax) in Patients with Advanced Gastric Cancer

Background: This study aimed to investigate the clinical and prognostic significance of preoperative maximum standardized uptake value (SUVmax) and GLUT-1 expression in patients with advanced gastric cancer (AGC). Methods: Medical records of patients who were diagnosed with AGC between 2018 and 2020 at Zhongshan Hospital of Fudan University (Shanghai, China) were retrospectively analyzed. Finally, 182 patients were enrolled, and for each patient, SUVmax was calculated for the primary lesion on PET/CT prior to curative surgery. A total of 165 clinical tissue specimens were collected for immunohistochemical analysis of GLUT-1 expression. Results: A total of 182 patients were divided into two groups based on their SUVmax values. The low SUVmax group comprised 92 patients. Patients with low SUVmax tended to be younger and included a higher proportion of women, with their primary tumors typically smaller or in earlier TNM stages. The median follow-up time was 52 months. The 1-, 3-, and 5-year progression-free survival (PFS) rates were 90.7%, 71.4%, and 67.0%, respectively. Among them, 33 patients experienced recurrence and metastasis, and 40 ultimately died. Log-rank analysis revealed that the low SUVmax group exhibited superior progression-free survival (PFS) and overall survival (OS). Multivariate analysis indicated that, for AGC without preoperative treatment, later stage (stage III) was independently correlated with a higher risk of recurrence (HR = 3.049; 95%CI = 1.076-8.639; p = 0.036), while the low SUVmax group exhibited a reduced risk of recurrence and mortality compared with the high SUVmax group (HR = 0.565; 95%CI = 0.326-0.979; p = 0.042). Conclusions: The clinicopathological characteristics of patients with AGC with different SUVmax values appeared significantly different. Tumor stage and SUVmax were found as independent factors affecting postoperative recurrence and death of patients with AGC.

Methodology Development for Investigating Pathophysiological [18F]-FDG Muscle Uptake in Patients with Rheumatic Musculoskeletal Diseases

Objectives: This retrospective study explored the qualitative and quantitative assessment of F18-fluordeoxyglucose ([18F]-FDG) positron emission tomography and computed tomography (PET/CT) scans to assess pathophysiological muscle glucose uptake in patients with a rheumatic musculoskeletal disease (RMD). [18F]-FDG PET/CT detects metabolic activity via glucose uptake in tissues. This study aimed to determine the feasibility of quantitative assessment of [18F]-FDG uptake in muscles across three different RMDs compared to controls. Methods: In this study we analysed whole-body [18F]-FDG PET/CT scans from patients with rheumatoid arthritis (RA; n = 11), osteoarthritis (OA; n = 10), and idiopathic inflammatory myositis (IIM; n = 10), and non-RMD controls (n = 11), focusing on muscle-tracer uptake in specific muscle groups. Qualitative assessment visually identified regions with high [18F]-FDG uptake, followed by quantitative assessment using two methods: fixed volume-of-interest (VOI) and hotspot VOI. In the fixed VOI method, a VOI was placed in the respective muscle at a fixed position (50% height from proximal to distal end) on PET/CT images. In the hotspot VOI method, the VOI was placed at the site of the highest [18F]-FDG uptake observed during qualitative assessment. Standardised uptake values (SUVs) were determined for different muscle groups between RMDs and controls. Results: Qualitative assessment revealed a heterogenous uptake pattern of [18F]-FDG that was found in 93% of quadriceps and hamstring muscles, while other muscles displayed either heterogenous or homogenous patterns. A Bland-Altman analysis showed that the hotspot VOI method had a higher sensitivity in detecting differential [18F]-FDG uptake in muscles. Across all muscle groups, patients with IIM had the highest [18F]-FDG uptake, followed by patients with OA and RA, respectively. Conclusions: [18F]-FDG PET/CT enables qualitative and quantitative differentiation of muscle glucose uptake in patients with RA, OA, and IIM, at both individual muscle and patient group levels. The hotspot method and SUVpeak are recommended for quantitative assessment. High [18F]-FDG uptake in multiple muscle groups suggests pathophysiological glucose metabolism in RMD-affected muscles.

Clinical Pilot of a Deep Learning Elastic Registration Algorithm to Improve Misregistration Artifact and Image Quality on Routine Oncologic PET/CT

RATIONALE AND OBJECTIVES

Misregistration artifacts between the PET and attenuation correction CT (CTAC) exams can degrade image quality and cause diagnostic errors. Deep learning (DL)-warped elastic registration methods have been proposed to improve misregistration errors.

MATERIALS AND METHODS

30 patients undergoing routine oncologic examination (20 18F-FDG PET/CT and 10 64Cu-DOTATATE PET/CT) were retrospectively identified and compared using unmodified CTAC, and a DL-augmented spatial transformation CT attenuation map. Primary endpoints included differences in subjective image quality and standardized uptake values (SUV). Exams were randomized to reduce reader bias, and three radiologists rated image quality across six anatomic sites using a modified Likert scale. Measures of local bias and lesion SUV were also quantitatively evaluated.

RESULTS

The DL attenuation correction methods were associated with higher image quality and reduced misregistration artifacts (Mean 18F-FDG quality rating=3.5-3.8 for DL vs 3.2-3.5 for standard reconstruction (STD); Mean 64Cu-DOTATATE quality rating= 3.2-3.4 for DL vs 2.1-3.3; P < 0.05 for STD, for all except 64Cu-DOTATATE inferior spleen). Percent change in superior liver SUVmean for 18F-FDG and 64Cu-DOTATATE were 5.3 ± 4.9 and 8.2 ± 4.1%, respectively. Measures of signal-to-noise ratio were significantly improved for the DL over STD (Hepatopulmonary index (HPI) [18F-FDG] = 4.5 ± 1.2 vs 4.0 ± 1.1, P < 0.001; HPI [64Cu-DOTATATE] = 16.4 ± 16.9 vs 12.5 ± 5.5, P = 0.039).

CONCLUSION

Deep learning elastic registration for CT attenuation correction maps on routine oncology PET/CT decreases misregistration artifacts, with a greater impact on PET scans with longer acquisition times.

18F-FDOPA PET/CT in Oncology: Procedural Guideline by the Korean Society of Nuclear Medicine

This guideline outlines the use of 3,4-dihydroxy-6-18F-fluoro-L-phenylalanine positron emission tomography / computed tomography for the diagnosis and management of neuroendocrine tumors, brain tumors, and other tumorous conditions. It provides detailed recommendations on patient preparation, imaging procedures, and result interpretation. Based on international standards and adapted to local clinical practices, the guideline emphasizes safety, quality control, and the effective application of 3,4-dihydroxy-6-18F-fluoro-L-phenylalanine positron emission tomography / computed tomography for various tumors such as insulinomas, pheochromocytomas, and medullary thyroid carcinoma. It also addresses the use of premedication with carbidopa, fasting protocols, and optimal imaging techniques. The aim is to assist nuclear medicine professionals in delivering precise diagnoses, improving patient outcomes, and accommodating evolving medical knowledge and technology. This comprehensive document serves as a practical resource to enhance the accuracy, quality, and safety of 3,4-dihydroxy-6-18F-fluoro-L-phenylalanine positron emission tomography / computed tomography in oncology.

Optimization of Reconstruction Parameters for Discovery 710 Positron Emission Tomography/Computed Tomography

Aim

This study aimed to optimize the quantitative aspects of (18F) fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) imaging by investigating the impact of various reconstruction parameters on the recovery coefficients (RCs) using the NEMA image quality phantom. Specifically, the study aims to assess how different matrix sizes, iterations, subsets, and Gaussian postfilters affect the accuracy of standardized uptake value (SUV) quantification in (18F) FDG PET/CT imaging.

Materials and Methods

The study utilized the "Vue Point FX + Sharp IR" algorithm for PET image reconstruction, incorporating 3D-ordered subset expectation maximization (3D-OSEM), time-of-flight, and point spread function technologies. Various reconstruction parameters were explored, including two distinct matrix sizes, multiple iterations, subsets, and a wide range of Gaussian postfilters. The investigation focused on the impact of these parameters on RCs using the NEMA image quality phantom.

Results

The results of the study indicated that for accurate SUV quantification in spheres ≥17 mm, the 256 × 256 matrix size and mean SUV should be employed. Conversely, for spheres ≤13 mm, maximum SUV was found to be more suitable. The choice of postfiltering value was shown to have a significant impact on SUV quantification accuracy, particularly for small-sized spheres. In addition, a larger matrix size was found to partially mitigate the effects of Gibbs artifact and slightly enhance SUV quantification for the spheres of various sizes.

Conclusion

This study highlights the critical importance of optimizing PET reconstruction parameters in accordance with the guidelines set by European Association of Nuclear Medicine/EARL. By optimizing these parameters, the accuracy and reliability of SUV quantification in (18F) FDG PET imaging can be significantly enhanced, especially for small-sized spheres. This underscores the necessity of carefully considering reconstruction parameters to ensure precise and reliable quantitative measurements in PET/CT imaging.

Comparison of sedation and general anesthesia protocols for 18F-FDG-PET/CT studies in dogs and cats: Musculoskeletal uptake and radiation dose to workers

In veterinary medicine, PET/CT scans are generally performed with the patient under general anesthesia. The aim of this prospective crossover study was to compare the musculoskeletal uptake of 18F-FDG and radiation doses to workers during PET/CT studies of healthy dogs and cats between sedation and general anesthesia. Volume and maximal standard uptake values (SUVmax) values of abnormal 18F-FDG uptake in the skeletal musculature, presence of misregistration artifact, and radiation doses to workers for each PET/CT study were recorded. Sedation was associated with increased volume of 18F-FDG uptake in the musculature of the thoracic limbs (p = .01), cervical (p = .02), and thoracic (p = .03) spine. Increased volume and SUVmax of the musculature assessed altogether were associated with the lighter degree of sedation (p = .04 for both). A significant decrease in the odds of misregistration artifact was observed for anesthetized animals in comparison with sedated (OR: 0.0, 95% CI: 0.0-0.0, p = .01). Radiation doses to workers were significantly higher for sedation compared with general anesthesia (p = .01) and for the anesthesia technician compared with the nuclear medicine technologist (p = .01). Use of sedation for PET/CT studies in dogs and cats is feasible. However, it is associated with increased physiologic musculoskeletal uptake of 18F-FDG in the thoracic limbs, cervical, and thoracic spine, with increased frequency of misregistration artifact, and with increased radiation doses to workers. These limitations can be overcome by recognition of the uptake pattern and monitoring/rotation of the involved staff at institutions where a high caseload is expected.

Quantification of metabolic activity in the evaluation of cardiac sarcoidosis

Sarcoidosis is a systemic disorder characterized by non-necrotizing granulomatous inflammation and fibrosis affecting multiple organs, notably the lungs and lymph nodes. Cardiac sarcoidosis (CS), a subset of the disease predominantly involving the heart, significantly heightens the associated morbidity and mortality of sarcoidosis. Early detection of CS is crucial for optimal management. Positron emission tomography/computed tomography (PET/CT) using 18F-fluorodeoxyglucose (18F-FDG) has emerged as an important diagnostic, prognostic, and monitoring tool for CS. Guidelines emphasize a combined approach of visual interpretation and adjunctive quantitative metrics to enhance diagnostic accuracy and treatment monitoring. Various quantitative parameters including maximum standardized uptake value (SUVmax), coefficient of variation, and texture analysis show promise as auxiliary tools diagnosing and prognosticating CS. However, standardization and validation of these quantitative methods remain challenging due to inter-center variability and technological differences. Further validation through large-scale, multi-center studies is needed to optimize their use and better delineate their role in CS diagnosis, prognostication, and therapy monitoring.

Automated Supraclavicular Brown Adipose Tissue Segmentation in Computed Tomography Using nnU-Net: Integration with TotalSegmentator

BACKGROUND/OBJECTIVES

Brown adipose tissue (BAT) plays a crucial role in energy expenditure and thermoregulation and has thus garnered interest in the context of metabolic diseases. Segmentation in medical imaging is time-consuming and prone to inter- and intra-operator variability. This study aims to develop an automated BAT segmentation method using the nnU-Net deep learning framework, integrated into the TotalSegmentator software, and to evaluate its performance in a large cohort of patients with lymphoma.

METHODS

A 3D nnU-Net model was trained on the manually annotated BAT regions from 159 lymphoma patients' CT scans, employing a 5-fold cross-validation approach. An ensemble model was created using these folds to enhance segmentation performance. The model was tested on an independent cohort of 30 patients. The evaluation metrics included the DICE score and Hausdorff Distance (HD). Additionally, the mean standardized uptake value (SUV) in the BAT regions was analyzed in 7107 FDG PET/CT lymphoma studies to identify patterns in the BAT SUVs.

RESULTS

The ensemble model achieved a state-of-the-art average DICE score of 0.780 ± 0.077 and an HD of 29.0 ± 14.6 mm in the test set, outperforming the individual fold models. Automated BAT segmentation revealed significant differences in the BAT SUVs between the sexes, with higher values in women. The morning scans showed a higher BAT SUV compared to the afternoon scans, and seasonal variations were observed, with an increased uptake during the winter. The BAT SUVs decreased with age.

CONCLUSIONS

The proposed automated BAT segmentation tool demonstrates robust performance, reducing the need for manual annotation. The analysis of a large patient cohort confirms the known patterns of BAT SUVs, highlighting the method's potential for broader clinical and research applications.

Prediction of biochemical recurrence after radical prostatectomy from primary tumour characteristics

OBJECTIVES

To construct and externally calibrate a predictive model for early biochemical recurrence (BCR) after radical prostatectomy (RP) incorporating clinical and modern imaging characteristics of the primary tumour.

PATIENTS AND METHODS

Patients who underwent RP following multiparametric magnetic resonance imaging, prostate biopsy and prostate-specific membrane antigen-positron emission tomography/computed tomography (PSMA-PET/CT), from two centres in Australia and the Netherlands. The primary outcome was biochemical recurrence-free survival (BRFS), where BCR was defined as a rising PSA level of ≥0.2 ng/mL or initiation of postoperative treatment per clinician discretion. Proportional hazards models to predict time to event were developed in the Australian sample using relevant pre- and post-surgical parameters and primary tumour maximum standardised uptake value (SUVmax) on diagnostic PSMA-PET/CT. Calibration was assessed in an external dataset from the Netherlands with the same inclusion criteria.

RESULTS

Data from 846 patients were used to develop the models. Tumour SUVmax was associated with worse predicted 3-year BRFS for both pre- and post-surgical models. SUVmax change from 4 to 16 lessened the predicted 3-year BRFS from 66% to 42% for a patient aged 65 years with typical pre-surgical parameters (PSA level 8 ng/mL, Prostate Imaging-Reporting and Data System score 4/5 and biopsy Gleason score ≥4 + 5). Considering post-surgical variables, a patient with the same age and PSA level but pathological stage pT3a, RP Gleason score ≥4 + 5 and negative margins, SUVmax change from 4 to 16 lessened the predicted 3-year BRFS from 76% to 61%. Calibration on an external sample (n = 464) showed reasonable performance; however, a tendency to overestimate survival in patients with good prognostic factors was observed.

CONCLUSION

Tumour SUVmax on diagnostic PSMA-PET/CT has utility additional to commonly recognised variables for prediction of BRFS after RP.

Implications of the partial volume effect correction on the spatial quantification of hypoxia based on [18F]FMISO PET/CT data

PURPOSE

This study evaluates the impact of partial volume effect (PVE) correction on [18F]fluoromisonidazole (FMISO) PET images, focusing on the conversion of standardized uptake values (SUV) to partial oxygen pressure (pO2) and the subsequent determination of hypoxic tumor volume (HTV).

METHODS

FMISO PET images from 49 head and neck squamous cell carcinoma cases were retrospectively corrected for PVE and converted to pO2. A pO2 threshold of 10 mmHg was used to delineate the HTV (HTVpO2). Comparisons of pO2 distribution and HTVpO2 between corrected and uncorrected images were made, with pO2 distributions evaluated against published polarographic data. HTVpO2 was compared to HTV defined by the conventional tumor-to-muscle ratio (TMR) method (HTVTMR) in terms of volume and topography (DICE coefficient, Hausdorff distance, and center-of-gravity distance) across different TMR cutoff levels. The cutoff level where the segmentation results from both methods were most similar was identified (TMRbest).

RESULTS

The PVE correction led to decreased minimum pO2, increased HTVpO2 and the identification of more hypoxic cases (HTV > 0). The pO2 distribution demonstrated improved alignment with published polarographic data. At TMRbest 1.6, the center-of-gravity distance between HTVTMR and HTVpO2 demonstrated a low median at 1.5 mm, while the wide range (0.0 to 9.6 mm) indicated high interpatient variability. The shape of HTV exhibited considerable variation with DICE 0.74 (0.03 to 1.00) and Hausdorff distance 8.5 mm (2.0 to 42.8 mm).

CONCLUSIONS

PVE correction is recommended before converting SUV to pO2 for the spatially resolved quantification of hypoxia.

Multi-level tuberculosis of the spine identified by 18 F-FDG-PET/CT and concomitant urogenital tuberculosis: a case report from the spinal TB X cohort

BACKGROUND

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb) and typically infects the lungs. However, extrapulmonary forms of TB can be found in approximately 20% of cases. It is suggested, that up to 10% of extrapulmonary TB affects the musculoskeletal system, in which spinal elements (spinal tuberculosis, STB) are involved in approximately 50% of the cases. STB is a debilitating disease with nonspecific symptoms and diagnosis is often delayed for months to years. In our Spinal TB X Cohort, we aim to describe the clinical phenotype of STB using whole-body 18 F-fluorodeoxyglucose positron emission tomography computed tomography (PET/CT) and to identify a specific gene expression profile for the different stages of dissemination on PET/CT. Here we report on the first patient recruited into our cohort who underwent PET/CT before treatment initiation, at 6-months and at 12-months - time of TB treatment completion.

CASE PRESENTATION

A 27-year-old immunocompetent male presented with severe thoracolumbar back pain for 9 months with severe antalgic gait and night sweats. Magnetic resonance imaging (MRI) of the whole spine revealed multilevel spinal disease (T5/6, T11/12, L3/4) in keeping with STB. After informed consent and recruitment into the Spinal TB X Cohort, the patient underwent PET/CT as per protocol, which revealed isolated multilevel STB (T4-7, T11/12, L3/4) with no concomitant lung or urogenital lesion. However, sputum and urine were Xpert MTB/RIF Ultra positive and Mtb was cultured from the urine sample. CT-guided biopsy of the T11/12 lesion confirmed drug-sensitive Mtb on Xpert MTB/RIF Ultra and the patient was started on TB treatment according to local guidelines for 12 months. The 6-month follow-up PET/CT revealed new and existing spinal lesions with increased FDG-uptake despite significant improvement of clinical features and laboratory markers. After 9 months of treatment, the patient developed an acute urethral stricture, most likely due to urogenital TB, and a suprapubic catheter was inserted. The 12-month PET/CT showed significantly decreased PET/CT values of all lesions, however, significant persistent spinal inflammation was present at the end of TB treatment. Clinically, the patient was considered cured by the TB control program and currently awaits urethroplasty.

CONCLUSIONS

In our case, PET/CT emerged as a valuable imaging modality for the initial assessment, surpassing MRI by revealing more comprehensive extensive disease. Subsequent PET/CT scans at 6-month uncovered new lesions and increased inflammation in existing ones, while by the end of TB treatment, all lesions exhibited improvement. However, the interpretation of FDG avidity remains ambiguous, whether it correlates with active infection and viable Mtb. or fibro- and osteoblast activity indicative of the healing process. Additionally, the absence of extraspinal TB lesions on PET/CT despite positive microbiology from sputum and urine maybe explained by paucibacillary, subclinical infection of extraspinal organs. The Spinal TB X Cohort endeavours to shed light on whole-body imaging patterns at diagnosis, their evolution midway through TB treatment, and upon treatment completion. Ultimately, this study aims to advance our understanding of the biology of this complex disease.

Optimization of reconstruction in quantitative brain PET images: Benefits from PSF modeling and correction of edge artifacts

BACKGROUND

Modern PET reconstruction algorithms incorporate point-spread-function (PSF) correction to mitigate partial volume effect. However, PSF correction can introduce edge artifacts that lead to quantification errors. Consequently, current international guidelines advise against using PSF correction in brain PET reconstruction.

PURPOSE

We aimed to investigate PSF-induced quantification errors in recent digital PET systems and identify conditions that mitigate them. This study utilized brain PET imaging with alginate-based realistic phantoms, simulating lesion-to-background activity ratios of 10:1 and 2:1, with eleven reconstruction parameter sets.

METHODS

Phantoms were prepared using a commercial anthropomorphic head phantom and two homemade inserts. Each insert contained a homogeneous 18F-FDG alginate background with hot spheres of varying diameter (3, 4, 6, 8, 10, 12, and 15 mm). PET imaging was conducted on a digital PET-CT system Biograph Vision 600 (Siemens), with a 10 min scan duration. Imaging was performed with and without PSF correction, with 2, 4, 6, 12, 18, or 24 iterations in reconstruction, and with or without additional Gaussian postfiltering. We assessed the recovery coefficient (RC), contrast recovery coefficient (CRC), variability, and CRC-to-variability ratios for each sphere size and reconstruction parameter set.

RESULTS

PSF-corrected images of the 10:1 spheres exhibited a nonmonotonic CRC-to-sphere diameter relationship due to edge artifacts overshoot in the 10 mm-diameter sphere. In contrast, PSF images of the 2:1 spheres showed a monotonically increasing relationship. Non-PSF images of both phantoms showed an expected monotonically increasing CRC-to-sphere diameter relationship but with lower CRC values compared to PSF images. The nonmonotonic relationship observed with 10:1 spheres was mitigated by applying a 3-mm FWHM Gaussian postfiltering. For both phantoms, reconstructions with 6 iterations, PSF correction, and additional 3-mm FWHM Gaussian postfiltering demonstrated the highest CRC-to-variability ratios.

CONCLUSIONS

Our findings indicate that Gaussian postfiltering suppresses PSF artifacts. This parameter set corrected the nonmonotonic CRC-to-sphere diameter relationship and improved the CRC-to-variability ratio compared to non-PSF reconstructions. Therefore, to enhance lesion detectability without compromising quantification accuracy, PSF correction coupled with Gaussian postfiltering should be used in brain PET.

Biomarkers to Inform Prognosis and Treatment for Unresectable or Metastatic GEP-NENs

Importance

Evidence-based treatment decisions for advanced gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) require individualized patient-centered decision-making that accounts for patient and cancer characteristics.

Objective

To create an accessible guidance document to educate clinicians and patients on biomarkers informing prognosis and treatment in unresectable or metastatic GEP-NENs.

Methods

A multidisciplinary panel in-person workshop was convened to define methods. English language articles published from January 2016 to January 2023 in PubMed (MEDLINE) and relevant conference abstracts were reviewed to investigate prognostic and treatment-informing features in unresectable or metastatic GEP-NENs. Data from included studies were used to form evidence-based recommendations. Quality of evidence and strength of recommendations were determined using the Grading of Recommendations, Assessment, Development and Evaluations framework. Consensus was reached via electronic survey following a modified Delphi method.

Findings

A total of 131 publications were identified, including 8 systematic reviews and meta-analyses, 6 randomized clinical trials, 29 prospective studies, and 88 retrospective cohort studies. After 2 rounds of surveys, 24 recommendations and 5 good clinical practice statements were developed, with full consensus among panelists. Recommendations focused on tumor and functional imaging characteristics, blood-based biomarkers, and carcinoid heart disease. A single strong recommendation was made for symptomatic carcinoid syndrome informing treatment in midgut neuroendocrine tumors. Conditional recommendations were made to use grade, morphology, primary site, and urinary 5-hydroxyindoleacetic levels to inform treatment. The guidance document was endorsed by the Commonwealth Neuroendocrine Tumour Collaboration and the North American Neuroendocrine Tumor Society.

Conclusions and Relevance

The study results suggest that select factors have sufficient evidence to inform care in GEP-NENs, but the evidence for most biomarkers is weak. This article may help guide management and identify gaps for future research to advance personalized medicine and improve outcomes for patients with GEP-NENs.

Value of Semi-Quantitative Parameters of 68Ga-FAPI-04 PET/CT in Primary Malignant and Benign Diseases: A Comparison with 18F-FDG

Objectives: We compared the value of the semiquantitative parameters of 68Ga-labeled FAP inhibitor (68Ga-FAPI)-04 positron emission tomography/computed tomography (PET/CT) and 18F-fluorodeoxyglucose (18F-FDG) in diagnosing primary malignant and benign diseases. Materials and Methods: 18F-FDG and 68Ga-FAPI-04 PET/CT images of 80 patients were compared. Semiquantitative parameters, including maximum standardized uptake value (SUVmax), mean SUV (SUVmean), peak SUV (SUVpeak), peak SUV by lean body mass (SULpeak), metabolic tumor volume (or tumor volume of FAPI; FAPI-TV), and TLG (or total lesion activity of FAPI; FAPI-TLA), were automatically obtained using the IntelliSpace Portal image processing workstation with a threshold of 40% SUVmax. The liver blood pool was measured as the background, and the tumor-to-background ratio (TBRliver) was calculated. Results: In all malignant lesions, FAPI-TV and FAPI-TLA were higher in 68Ga-FAPI-04 PET/CT than in 18F-FDG. In the subgroup analysis, 68Ga-FAPI-04 had higher FAPI-TV and FAPI-TLA and lower SUVmax than 18F-FDG had in group A, including gynecological tumor, esophageal, and colorectal cancers. However, six semiquantitative parameters were higher in group B (the other malignant tumors). For the benign diseases, SUVmax, SUVmean, SUVpeak, and SULpeak were lower in 68Ga-FAPI-04 PET/CT than in 18F-FDG. 68Ga-FAPI-04 PET/CT showed a lower liver background and a higher TBRliver than 18F-FDG did. 68Ga-FAPI-04 PET/CT had higher accuracy, sensitivity, and specificity than 18F-FDG had. Conclusion: More accurate semiquantitative parameters and lower abdominal background in 68Ga-FAPI-04 PET/CT make it more competitive in the differential diagnosis of malignant and benign diseases than in 18F-FDG.

Whole-Body Multiparametric PET in Clinical Oncology: Current Status, Challenges, and Opportunities

The interpretation of clinical oncologic PET studies has historically used static reconstructions based on SUVs. SUVs and SUV-based images have important limitations, including dependence on uptake times and reduced conspicuity of tracer-avid lesions in organs with high background uptake. The acquisition of dynamic PET images enables additional PET reconstructions via Patlak modeling, which assumes that a tracer is irreversibly trapped by tissues of interest. The resulting multiparametric PET images capture a tracer's net trapping rate and apparent volume of distribution, separating the contributions of bound and free tracer fractions to the PET signal captured in the SUV. Potential benefits of multiparametric PET include higher quantitative stability, superior lesion conspicuity, and greater accuracy for differentiating malignant and benign lesions. However, the imaging protocols necessary for multiparametric PET are inherently more complex and time intensive, despite the recent introduction of automated or semiautomated scanner-based reconstruction packages. In this Review, we examine the current state of multiparametric PET in whole-body oncologic imaging. We summarize the Patlak method and relevant tracer kinetics, discuss clinical workflows and protocol considerations, and highlight clinical challenges and opportunities. We aim to help oncologic imagers make informed decisions about whether to implement multiparametric PET in their clinical practices.

Cardiac Neuroendocrine Tumor Metastases on 68Ga-DOTATATE PET/CT: Identification and Prognostic Significance

Neuroendocrine tumor (NET) metastases to the heart are found in 1%-4% of NET patients and have been reported primarily in the form of individual cases. We investigated the prevalence, clinical characteristics, imaging features, and outcomes of NET patients with cardiac metastases on 68Ga-DOTATATE PET/CT. Methods: 68Ga-DOTATATE PET/CT of 490 consecutive patients from a single institution were retrospectively reviewed for sites of metastases. The cumulative cardiovascular event rate and overall survival of patients with cardiac NET metastases (CNMs) were compared with those of a control group of metastatic NET patients without cardiac metastases. In patients with CNMs, the cardiac SUVmax with and without normalization to the myocardial background uptake was compared with a separate cohort of 11 patients with active cardiac sarcoidosis who underwent 68Ga-DOTATATE PET/CT for research purposes. Results: In total, 270 patients with metastatic NETs were identified, 9 (3.3%) of whom had CNMs. All 9 patients had grade 1-2 gastroenteropancreatic NETs, most commonly from the small intestine (7 patients). The control group consisted of 140 patients with metastatic grade 1-2 gastroenteropancreatic NETs. On Kaplan-Meier analysis, there was no significant difference in the risk of cardiovascular adverse events (P = 0.91 on log-rank test) or mortality (P = 0.83) between the metastatic NET patients with and without cardiac metastases. The degree of cardiac DOTATATE uptake was significantly higher in CNMs than in patients with cardiac sarcoidosis without overlap, in terms of both cardiac SUVmax (P = 0.027) and SUVmax-to-myocardial background ratio (P = 0.021). Conclusion: Routine 68Ga-DOTATATE PET/CT can be used to identify CNMs in 3% of patients with metastatic NETs. CNMs do not confer added cardiovascular or mortality risk. A distinguishing feature of CNMs is their high degree of DOTATATE uptake compared with focal myocardial inflammation.

Investigating the Impact of Voxel Size and Postfiltering on Quantitative Analysis of Positron Emission Tomography/Computed Tomography: A Phantom Study

Aim

This study aims to investigate the influence of voxel size and postfiltering on the quantification of standardized uptake value (SUV) in positron emission tomography/computed tomography (PET/CT) images.

Materials and Methods

National Electrical Manufacturers Association phantom with the spheres of different sizes were utilized to simulate the lesions. The phantom was scanned using a PET/CT scanner, and the acquired images were reconstructed using two different matrix sizes, (192 × 192) and (256 × 256), and a wide range of postfiltering values.

Results

The findings demonstrated that postfiltering significantly affected SUV measurements. The changes in postfiltering values can result in overestimation or underestimation of SUV values, highlighting the importance of carefully selecting appropriate filters. Increasing the matrix size improved SUVmax and SUVmean values, particularly for small-sized spheres. Smaller voxel reconstructions slightly reduced partial volume effects and partially enhanced SUV quantification.

Conclusions

Careful consideration of postfiltering values and matrix size selection can lead to better SUV quantification. These findings emphasize the need to optimize the reconstruction parameters to enhance the clinical utility of PET/CT in detecting and evaluating malignant lesions.

Role of Novel Quantitative Imaging Techniques in Hematological Malignancies

Hematological malignancies exhibit a widespread distribution, necessitating evaluation of disease activity over the entire body. In clinical practice, visual analysis and semiquantitative parameters are used to assess 18F-FDGPET/CT imaging, which solely represents measurements of disease activity from limited area and may not adequately reflect global disease assessment. An efficient method for assessing the global disease burden of hematological malignancies is to employ PET/computed tomography based novel quantitative parameters. In this article, we explored novel quantitative parameters on PET/CT imaging for assessing global disease burden and the potential role of artificial intelligence (AI) to determine these parameters in evaluation of hematological malignancies.

Clinical Performance Comparison of a Long Versus a Short Axial Field-of-View PET/CT Using EARL-Compliant Reconstructions

PURPOSE

To ensure comparable PET/CT image quality between or within centres, clinical inter-system performance comparisons following European Association of Nuclear Medicine Research Ltd. (EARL) guidelines is required. In this work the performance of the long axial field-of-view Biograph Vision Quadra is compared to its predecessor, the short axial field-of-view Biograph Vision.

PROCEDURES

To this aim, patients with suspected tumour lesions received a single weight-based (3 MBq/kg) 2-deoxy-2-[18F]fluoro-D-glucose injection and underwent routine clinical ( ∼ 15 min) scans on the Vision and 3-min scans on the Quadra in listmode in balanced order. Image quality (IQ), image noise (IN), and tumour demarcation (TD) were assessed visually by four nuclear medicine physicians using a 5-point Likert scale and semiquantitative analysis was performed using standardised uptake values (SUVs). Inter-reader agreement was tested using Wilcoxon's signed rank test and the SUVs were statistically compared using a paired t-test.

RESULTS

Twenty patients (mean age, 60 years ± 8.8 [standard deviation], 16 male) were enrolled. Inter-reader agreement ranged from good to very good for IQ and IN (0.62 ≤ W ≤ 0.81), and fair for TD (0.29 ≤ W ≤ 0.39). Furthermore, a significant difference was found for TD (p = 0.015) between the systems, showing improved TD for the Quadra.

CONCLUSION

This study demonstrates that the Quadra can be used in routine clinical practice with multiple PET/CT systems or in multicentre studies. This system provides comparable diagnostic image quality and semiquantitative accuracy, improved TD, and has the advantage of shorter scan durations.

Application of Dynamic [18F]FDG PET/CT Multiparametric Imaging Leads to an Improved Differentiation of Benign and Malignant Lung Lesions

PURPOSE

To evaluate the potential of whole-body dynamic (WBD) 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography ([18F]FDG PET/CT) multiparametric imaging in the differential diagnosis between benign and malignant lung lesions.

PROCEDURES

We retrospectively analyzed WBD PET/CT scans from patients with lung lesions performed between April 2020 and March 2023. Multiparametric images including standardized uptake value (SUV), metabolic rate (MRFDG) and distribution volume (DVFDG) were visually interpreted and compared. We adopted SUVmax, metabolic tumor volume (MTV) and total lesion glycolysis (TLG) for semi-quantitative analysis, MRmax and DVmax values for quantitative analysis. We also collected the patients' clinical characteristics. The variables above with P-value < 0.05 in the univariate analysis were entered into a multivariate logistic regression. The statistically significant metrics were plotted on receiver-operating characteristic (ROC) curves.

RESULTS

A total of 60 patients were included for data evaluation. We found that most malignant lesions showed high uptake on MRFDG and SUV images, and low or absent uptake on DVFDG images, while benign lesions showed low uptake on MRFDG images and high uptake on DVFDG images. Most malignant lesions showed a characteristic pattern of gradually increasing FDG uptake, whereas benign lesions presented an initial rise with rapid fall, then kept stable at a low level. The AUC values of MRmax and SUVmax are 0.874 (95% CI: 0.763-0.946) and 0.792 (95% CI: 0.667-0.886), respectively. DeLong's test showed the difference between the areas is statistically significant (P < 0.001).

CONCLUSIONS

Our study demonstrated that dynamic [18F]FDG PET/CT imaging based on the Patlak analysis was a more accurate method of distinguishing malignancies from benign lesions than conventional static PET/CT scans.

Imaging Modalities for Head and Neck Cancer: Present and Future

Several imaging modalities are utilized in the diagnosis, treatment, and surveillance of head and neck cancer. First-line imaging remains computed tomography (CT); however, MRI, PET with CT (PET/CT), and ultrasound are often used. In the last decade, several new imaging modalities have been developed that have the potential to improve early detection, modify treatment, decrease treatment morbidity, and augment surveillance. Among these, molecular imaging, lymph node mapping, and adjustments to endoscopic techniques are promising. The present review focuses on existing imaging, novel techniques, and the recent changes to imaging practices within the field.

Quantitative 68Ga-PSMA-11 PET and Clinical Outcomes in Metastatic Castration-resistant Prostate Cancer Following 177Lu-PSMA-617 (VISION Trial)

Background Lutetium 177 [177Lu]Lu-PSMA-617 (177Lu-PSMA-617) is a prostate-specific membrane antigen (PSMA)-targeted radioligand therapy for metastatic castration-resistant prostate cancer (mCRPC). Quantitative PSMA PET/CT analysis could provide information on 177Lu-PSMA-617 treatment benefits. Purpose To explore the association between quantitative baseline gallium 68 [68Ga]Ga-PSMA-11 (68Ga-PSMA-11) PET/CT parameters and treatment response and outcomes in the VISION trial. Materials and Methods This was an exploratory secondary analysis of the VISION trial. Eligible participants were randomized (June 2018 to October 2019) in a 2:1 ratio to 177Lu-PSMA-617 therapy (7.4 GBq every 6 weeks for up to six cycles) plus standard of care (SOC) or to SOC only. Baseline 68Ga-PSMA-11 PET parameters, including the mean and maximum standardized uptake value (SUVmean and SUVmax), PSMA-positive tumor volume, and tumor load, were extracted from five anatomic regions and the whole body. Associations of quantitative PET parameters with radiographic progression-free survival (rPFS), overall survival (OS), objective response rate, and prostate-specific antigen response were investigated using univariable and multivariable analyses (with treatment as the only other covariate). Outcomes were assessed in subgroups based on SUVmean quartiles. Results Quantitative PET parameters were well balanced between study arms for the 826 participants included. The median whole-body tumor SUVmean was 7.6 (IQR, 5.8-9.9). Whole-body tumor SUVmean was the best predictor of 177Lu-PSMA-617 efficacy, with a hazard ratio (HR) range of 0.86-1.43 for all outcomes (all P < .001). A 1-unit whole-body tumor SUVmean increase was associated with a 12% and 10% decrease in risk of an rPFS event and death, respectively. 177Lu-PSMA-617 plus SOC prolonged rPFS and OS in all SUVmean quartiles versus SOC only, with no identifiable optimum among participants receiving 177Lu-PSMA-617. Higher baseline PSMA-positive tumor volume and tumor load were associated with worse rPFS (HR range, 1.44-1.53 [P < .05] and 1.02-1.03 [P < .001], respectively) and OS (HR range, 1.36-2.12 [P < .006] and 1.04 [P < .001], respectively). Conclusion Baseline 68Ga-PSMA-11 PET/CT whole-body tumor SUVmean was the best predictor of 177Lu-PSMA-617 efficacy in participants in the VISION trial. Improvements in rPFS and OS with 177Lu-PSMA-617 plus SOC were greater among participants with higher whole-body tumor SUVmean, with evidence for benefit at all SUVmean levels. ClinicalTrials.gov identifier: NCT03511664 Published under a CC BY 4.0 license. Supplemental material is available for this article.

The pons as an optimal background reference region for spinal 18F-FET PET/MRI evaluation

BACKGROUND

This study aims to evaluate the effect of various background reference regions on spinal 18F-FET PET imaging, with a focus on distinguishing between spinal tumors and myelitis. To enhance diagnostic accuracy, we investigated the pons and several other spinal cord area as potential references, given the challenges in interpreting spinal PET results.

RESULTS

A retrospective analysis was conducted on 30 patients, 15 with cervical myelitis and 15 with cervical tumors, who underwent O-(2-[18F]-fluoroethyl)-L-tyrosine (FET) PET/MR imaging. The stability of uptake across four regions, including the pons, C2, C2-C7, and T1-T3, was compared. The standardized uptake value ratio (SUVR) was then evaluated using various background regions, and their effectiveness in differentiating between spinal tumors and myelitis was compared. Additionally, we correlated the SUVR values derived from these regions with the Ki-67 proliferation index in tumor patients. The study found no significant difference in SUVmax (U = 110, p = 0.93) and SUVmean (U = 89, p = 0.35) values at lesion sites between myelitis and tumor patients. The pons had the highest average uptake (p < 0.001) compared to the other three regions. However, its coefficient of variation (CV) was significantly lower than that of the C2-C7 (p < 0.0001) and T1-T3 segments (p < 0.05). The SUVRmax values, calculated using the regions of pons, C2-C7 and T1-T3, were found to significantly differentiate between tumors and myelitis (p < 0.05). However, only the pons-based SUVRmean was able to significantly distinguish between the two groups (p < 0.05). Additionally, the pons-based SUVRmax (r = 0.63, p = 0.013) and SUVRmean (r = 0.67, p = 0.007) demonstrated a significant positive correlation with the Ki-67 index.

CONCLUSIONS

This study suggests that the pons may be considered a suitable reference region for spinal 18F-FET PET imaging, which can improve the differentiation between spinal tumors and myelitis. The significant correlation between pons-based SUVR values and the Ki-67 index further highlights the potential of this approach in assessing tumor cell proliferation.

Comparison of digital and analog [68Ga]Ga-PSMA-11 PET/CT for detecting post-prostatectomy biochemical recurrence in prostate cancer patients: a prospective study

Digital positron emission tomography/computed tomography (PET/CT) has shown enhanced sensitivity and spatial resolution compared with analog PET/CT. The present study compared the diagnostic performance of digital and analog PET/CT with [68Ga]Ga-PSMA-11 in prostate cancer patients who experienced biochemical recurrence (BCR) after prostatectomy. Forty prostate cancer patients who experienced BCR, defined as serum prostate-specific antigen (PSA) concentrations exceeding 0.2 ng/mL after prostatectomy, were prospectively recruited. These patients were stratified into three groups based on their serum PSA levels. [68Ga]Ga-PSMA-11 was injected into each patient, and images were acquired using both analog and digital PET/CT scanners. Analog and digital PET/CT showed comparable lesion detection rate (71.8% vs. 74.4%), sensitivity (85.0% vs. 90.0%), and positive predictive value (PPV, 100.0% vs. 100.0%). However, digital PET/CT detected more lesions (139 vs. 111) and had higher maximum standardized uptake values (SUVmax, 14.3 vs. 10.3) and higher kappa index (0.657 vs. 0.502) than analog PET/CT, regardless of serum PSA levels. On both analog and digital PET/CT, lesion detection rates and interrater agreement increased with increasing serum PSA levels. Compared with analog PET/CT, digital PET/CT detected more lesions with a higher SUVmax and better interrater agreement in prostate cancer patients who experienced BCR after prostatectomy.

Clinical T2 N0 M0 Esophageal Cancer: Identifying Predictive Factors of Upstaging

BACKGROUND

Inaccuracy of clinical staging renders management of clinical T2 N0 M0 (cT2 N0 M0) esophageal cancer difficult. When an underlying advanced-stage disease is understaged to cT2 N0 M0, patients miss the opportunity to gain the potential benefits of neoadjuvant therapy. This study aimed to identify preoperative factors that predict underlying advanced-stage esophageal cancer.

METHODS

From 2000 to 2020, 1579 patients with esophageal cancer underwent esophagectomy. Sixty patients who underwent upfront surgery for cT2 N0 M0 esophageal cancer were included in this study. The median age was 62.5 years, and 78% (n = 47) of these patients were male. Radiologic, clinical, and endoscopic factors were evaluated as preoperative markers. The Fisher exact and the Wilcoxon rank sum tests were used for categoric and continuous variables, respectively. Random forest classification was used to identify preoperative factors for predicting upstaging and downstaging.

RESULTS

Of the 60 patients, 8 (13%) were found to have pathologic T2 N0 M0 esophageal cancer. Sixteen (27%) patients had cancer that was pathologically downstaged, and 36 (60%) had upstaged disease. Seven (19%) patients had upstaged cancer on the basis of the pathologic T stage, 14 (39%) had upstaging on the basis of the pathologic N stage, and 15 (42%) had upstaging on the basis of both T and N stages. Dysphagia (P = .003) and tumor maximum standardized uptake value (P = .048) were predictors of upstaging, with a combined predictive value of up to 75%.

CONCLUSIONS

The presence of dysphagia and of high maximum standardized uptake value (≥5) of the tumor is predictive of more advanced underlying disease for patients with cT2 N0 M0 esophageal cancer, and these patients should be considered for neoadjuvant therapy.

Can FDG-PET/CT imaging be used to predict decline in quality of life in interstitial lung disease? A prospective study of the relationship between FDG uptake and quality of life in a UK outpatient setting

BACKGROUND

18Fluorine-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) CT imaging has been used in many inflammatory and infectious conditions to differentiate areas of increased metabolic activity. FDG uptake differs between areas of normal lung parenchyma and interstitial lung disease (ILD).

OBJECTIVES

In this study, we investigated whether FDG-PET/CT parameters were associated with a change in the quality of life (QoL) in patients with ILD over 4 years of follow-up.

METHODS

Patients underwent PET-CT imaging at diagnosis and were followed up with annual QoL assessment using the St George's Respiratory Questionnaire (SGRQ) until death or 4 years of follow-up. Maximum standard uptake value (SUVmax) and Tissue-to-Background Ratio (TBR) were assessed against SGRQ overall and subscale scores.

RESULTS

193 patients (94 patients in the idiopathic pulmonary fibrosis (IPF) subgroup and 99 patients in the non-IPF subgroup) underwent baseline FDG-PET/CT imaging and QoL assessment. Weak-to-moderate correlation was observed between baseline SUVmax and SGRQ scores in both ILD subgroups. No relationship was observed between baseline SUVmax or TBR and change in SGRQ scores over 4 years of follow-up. In the IPF subgroup, surviving patients reported a decline in QoL at 4 years post diagnosis whereas an improvement in QoL was seen in surviving patients with non-IPF ILD.

CONCLUSIONS

Weak-to-moderate positive correlation between baseline SUVmax and SGRQ scores was observed in both ILD subgroups (IPF:rs=0.187, p=0.047, non-IPF: rs=0.320, p=0.001). However, baseline SUVmax and TBR were not associated with change in QoL in patients with IPF and non-IPF ILD over 4 years of follow-up. At 4 years post diagnosis, surviving patients with IPF reported declining QoL whereas improvement was seen in patients with ILD who did not have IPF.

The Association between the Body Mass Index, Chronic Obstructive Pulmonary Disease and SUV of the Non-Tumorous Lung in the Pretreatment [18F]FDG-PET/CT of Patients with Lung Cancer

Background: A debate persists on the prognostic value of the pre-therapeutic standardized uptake value (SUV) of non-tumorous lung tissue for the risk assessment of therapy-related pneumonitis, with most studies lacking significant correlation. However, the influence of patient comorbidities on the pre-therapeutic lung SUV has not yet been systematically evaluated. Thus, we aimed to elucidate the association between comorbidities, biological variables and lung SUVs in pre-therapeutic [18F]FDG-PET/CT. Methods: In this retrospective study, the pre-therapeutic SUV in [18F]FDG-PET/CT was measured in non-tumorous areas of both lobes of the lung. SUVMEAN, SUVMAX and SUV95 were compared to a multitude of patient characteristics and comorbidities with Spearman's correlation analysis, followed by a Bonferroni correction and multilinear regression. Results: In total, 240 patients with lung cancer were analyzed. An elevated BMI was significantly associated with increased SUVMAX (β = 0.037, p < 0.001), SUVMEAN (β = 0.017, p < 0.001) and SUV95 (β = 0.028, p < 0.001). Patients with chronic obstructive pulmonary disease (COPD) showed a significantly decreased SUVMAX (β = -0.156, p = 0.001), SUVMEAN (β = -0.107, p < 0.001) and SUV95 (β = -0.134, p < 0.001). Multiple other comorbidities did not show a significant correlation with the SUV of the non-tumorous lung. Conclusions: Failure to consider the influence of BMI and COPD on the pre-therapeutic SUV measurements may lead to an erroneous interpretation of the pre-therapeutic SUV and subsequent treatment decisions in patients with lung cancer.

Characterization of sacral chordoma and differential diagnosis from other sacral malignancy using [18F]FDG PET/CT

2-Deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) positron emission tomography (PET)/computed tomography (CT) is known to be a helpful imaging modality for sacral chordoma, but its detailed characteristics have not been fully described. The purpose of our study was to identify the [18F]FDG PET/CT imaging characteristics of sacral chordoma and compare them with other sacral malignancy. This retrospective study included patients who underwent [18F]FDG PET/CT because of a mass involving the sacrum. Investigated visual findings included visual score and distribution, and semiquantitative parameters measured included standardized uptake values (SUVmax, SUVpeak, SUVmean), tumor-to-liver ratio (TLR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and tumor size. Comparison studies and receiver operating characteristics (ROC) curve analysis were performed to differentiate between sacral chordoma and other sacral malignancy. Ten patients with sacral chordoma were finally included (M:F = 6:4, median age = 67 yr). On [18F]FDG PET/CT, sacral chordomas presented as a mass with minimal-moderate uptake with a usually heterogenous distribution. Compared with 12 patients with other sacral malignancies (M:F = 4:8, median age 42 yr), sacral chordoma showed a significantly lower TLR (median value 2.1 vs 6.3, P = .021). In ROC curve analysis, TLR showed the largest area under the curve (AUC) of 0.79 (cutoff ≤ 4.0; sensitivity 100.0%, specificity 58.3%; P = .004), and SUVmax showed the second largest AUC of 0.73 (cutoff ≤ 6.9; sensitivity 80.0%, specificity 66.7%; P = .034). [18F]FDG PET/CT of sacral chordoma showed minimal-moderate uptake. The TLR of [18F]FDG PET/CT was significantly lower than that of other sacral malignancy and was the most useful parameter for differentiating sacral chordoma, with the largest AUC. SUVmax could be another helpful semiquantitative parameter.

Correlation between breast cancer and background parenchymal uptake on 18F-fluorodeoxyglucose positron emission tomography

PURPOSE

This study aimed to investigate differences in background parenchymal uptake (BPU) between patients with and without breast cancer using 18F-fluorodeoxyglucose positron emission tomography.

METHODS

Female patients (n = 130, 62.9 ± 12.7 years) with newly diagnosed breast cancer and 50 healthy participants (59.6 ± 13.3 years) without breast cancer were retrospectively included. BPU was evaluated using the maximum standardized uptake value. Data on participant age, body mass index, blood glucose level, and menopausal status were collected from medical records. Breast density was evaluated using mammography. Logistic regression analysis and receiver operating characteristic curves were used to examine the correlation between breast cancer and various characteristic factors, including BPU.

RESULTS

The BPU of patients with breast cancer was significantly higher than that of controls (P < 0.001). The results of logistic regression analysis regarding the presence of breast cancer demonstrated that BPU and menopausal status showed higher odds ratios of 13.6 and 4.25, respectively. The area under the receiver operating characteristic curve for BPU was 0.751.

CONCLUSIONS

Patients with breast cancer showed higher 18F-fluorodeoxyglucose-BPU. Glucose metabolism of mammary glands may correlate with the development of breast cancer.

Activity quantification and dosimetry in radiopharmaceutical therapy with reference to 177Lutetium

Radiopharmaceutical therapy has been widely adopted owing primarily to the development of novel radiopharmaceuticals. To fully utilize the potential of these RPTs in the era of precision medicine, therapy must be optimized to the patient's tumor characteristics. The vastly disparate dosimetry methodologies need to be harmonized as the first step towards this. Multiple factors play a crucial role in the shift from empirical activity administration to patient-specific dosimetry-based administrations from RPT. Factors such as variable responses seen in patients with presumably similar clinical characteristics underscore the need to standardize and validate dosimetry calculations. These efforts combined with ongoing initiatives to streamline the dosimetry process facilitate the implementation of radiomolecular precision oncology. However, various challenges hinder the widespread adoption of personalized dosimetry-based activity administration, particularly when compared to the more convenient and resource-efficient approach of empiric activity administration. This review outlines the fundamental principles, procedures, and methodologies related to image activity quantification and dosimetry with a specific focus on 177Lutetium-based radiopharmaceuticals.

Comprehensive literature review of oral and intravenous contrast-enhanced PET/CT: a step forward?

The integration of diagnostic CT scans into PET/CT facilitates a comprehensive single examination, presenting potential advantages for patients seeking a thorough one-shot check-up. The introduction of iodinated contrast media during PET scanning raises theoretical concerns about potential interference with uptake quantification, due to the modification of tissue density on CT. Nevertheless, this impact appears generally insignificant for clinical use, compared to the intrinsic variability of standardized uptake values. On the other hand, with the growing indications of PET, especially 18F-FDG PET, contrast enhancement increases the diagnostic performances of the exam, and provides additional information. This improvement in performance achieved through contrast-enhanced PET/CT must be carefully evaluated considering the associated risks and side-effects stemming from the administration of iodinated contrast media. Within this article, we present a comprehensive literature review of contrast enhanced PET/CT, examining the potential impact of iodinated contrast media on quantification, additional side-effects and the pivotal clinically demonstrated benefits of an all-encompassing examination for patients. In conclusion, the clinical benefits of iodinated contrast media are mainly validated by the large diffusion in PET protocols. Contrary to positive oral contrast, which does not appear to offer any major advantage in patient management, intravenous iodine contrast media provides clinical benefits without significant artifact on images or quantification. However, studies on the benefit-risk balance for patients are still lacking.