False-positive uptake on 2-[¹⁸F]-fluoro-2-deoxy-D-glucose (FDG) positron-emission tomography/computed tomography (PET/CT) in oncological imaging

Examination of iatrogenic FDG accumulation after COVID-19 vaccination

PURPOSE

This study aimed to investigate the frequency of COVID-19 vaccine-induced reactive change and potential factors including blood type correlated with increased FDG uptake on positron emission tomography (PET)/computed tomography (CT).

MATERIALS AND METHODS

We evaluated 284 patients who underwent PET/CT between June and September 2021 and had a known history of COVID-19 vaccination. Information on the injection site, vaccine type, and adverse reactions was obtained. We visually assessed the presence or absence of accumulation in the axillary and supraclavicular lymph nodes and the deltoid muscles. We measured the maximum standardized uptake value (SUVmax) using semi-quantitative analysis.

RESULTS

Our study included 158 males and 126 females aged 16-94. The median time between vaccination and PET/CT was 9 and 42 days for patients who had received their first and second doses, respectively. We observed axillary lymph node accumulation, supraclavicular lymph node accumulation, and deltoid muscle accumulation in 98 (SUVmax 1.07-25.1), nine (SUVmax 2.28-14.5), and 33 cases (SUVmax 0.93-7.42), respectively. In cases with axillary lymph node (P = 0.0057) or deltoid muscle (P = 0.047) accumulation, the shorter the time since vaccination, the higher the FDG accumulation. Patients with axillary lymph node accumulation were significantly younger (P < 0.0001) and had a significantly higher frequency of adverse reactions such as fever (P < 0.0001) and myalgia (P = 0.002). No significant relationship was observed between blood type and the frequency of FDG accumulation. Logistic regression analysis also showed that age, gender, days since vaccination, and adverse reactions such as fever and myalgia were important factors for axillary lymph node accumulation.

CONCLUSION

Our study found that FDG accumulation in the axillary lymph nodes and deltoid muscle was higher within a shorter time after vaccination, and axillary lymph node accumulation was higher in young patients, females, and those with adverse reactions of fever and myalgia. No significant relationship was observed between blood type and the frequency of FDG accumulation. Confirming the vaccination status, time since vaccination, and the presence of adverse reactions before PET may reduce false positives.

Addressing positive multi-cancer early detection tests in head and neck Surgery: Experience with head and neck work up for high-risk referrals

OBJECTIVES

Blood-based multi-cancer early detection (MCED) tests are now commercially available. However, there are currently no consensus guidelines available for head and neck cancer (HNC) providers to direct work up or surveillance for patients with a positive MCED test. We seek to describe cases of patients with positive MCED tests suggesting HNC and provide insights for their evaluation.

METHODS

Retrospective chart review of patients referred to Otolaryngology with an MCED result suggesting HNC. Patients enrolled in prospective MCED clinical trials were excluded. Cancer diagnoses were confirmed via frozen-section pathology.

RESULTS

Five patients were included (mean age: 69.2 years, range 50-87; 4 male) with MCED-identified-high-risk for HNC or lymphoma. Only patient was symptomatic. After physical exam and follow-up head and neck imaging, circulating tumor HPV DNA testing, two patients were diagnosed with p16 + oropharyngeal squamous cell carcinomas and underwent appropriate therapy. A third patient had no evidence of head and neck cancer but was diagnosed with sarcoma of the thigh. The remaining two patients had no evidence of malignancy after in-depth workup.

CONCLUSIONS

In this retrospective study, 2 of 5 patients referred to Otolaryngology with a positive MCED result were diagnosed with HPV + oropharyngeal squamous cell carcinoma. We recommend that positive HNC MCED work up include thorough head and neck examination with flexible laryngoscopy and focused CT or MRI imaging. Given the potential for inaccurate MCED tissue of origin classification, PET/CT may be useful in specific situations. For a patient with no cancer identified, development of clear guidelines is warranted.

[18F]FDG-PET/CT-based risk stratification in women with locally advanced uterine cervical cancer

BACKGROUND

[18F]FDG-PET/CT is used for staging and treatment planning in patients with locally advanced cervical cancer (LACC). We studied if a PET-based prediction model could provide additional risk stratification beyond International Federation of Gynaecology and Obstetrics (FIGO) staging in our population with LACC to aid treatment decision making.

METHODS

In total, 183 patients with LACC treated with chemoradiation between 2013 and 2018 were included. Patients were treated according to FIGO 2009 and retrospectively reclassified according to FIGO 2018 staging system. After validation of an existing PET-based prediction model, the predicted recurrent free survival (RFS), disease specific survival (DSS) and overall survival (OS) at 1, 3, and 5 years, based on metabolic tumor volume (MTV), maximum standardized uptake value (SUVmax) and highest level of [18F]FDG-positive node was calculated. Then the observed survival was compared to the predicted survival. An area under the curve (AUC) close to or higher than 0.7 was considered adequate for accurate prediction. The Youden (J) index defined survival chance cutoff values for low and high risk groups.

RESULTS

All AUC values for the comparison between predicted and observed outcomes were > 0.7 except for 5-year RFS and for 5-year OS which were close to 0.7 (0.684 and 0.650 respectively). Cutoff values for low and high risk survival chance were 0.44 for the 3-year RFS and 0.47 for the 5-year OS. The FIGO 2009 system could not differentiate between the risk profiles. After reclassification according to FIGO 2018, all patients with stage IIIC2 and IVB fell in the high risk and almost all patients with stages IB2-IIIB and IVA in the low risk group. In patients with stage IIIC1 disease the FIGO stage cannot discriminate between the risk profiles.

CONCLUSIONS

Low and high risk patients with LACC can be identified with the PET-based prediction model. In particular patients with stage IIIC1 need additional risk stratification besides the FIGO 2018 staging. The Kidd model could be a useful tool to aid treatment decision making in these patients. Our results also support the choice of [18F]FDG-PET/CT imaging in patients with LACC.

False Liver Metastasis by Positron Emission Tomography/Computed Tomography Scan after Chemoradiotherapy for Esophageal Cancer-Potential Overstaged Pitfalls of Treatment

In patients with esophageal cancer undergoing neoadjuvant chemoradiotherapy (nCRT), subsequent restaging with F-18-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET-CT) can reveal the presence of interval metastases, such as liver metastases, in approximately 10% of cases. Nevertheless, it is not uncommon in clinical practice to observe focal FDG uptake in the liver that is not associated with liver metastases but rather with radiation-induced liver injury (RILI), which can result in the overstaging of the disease. Liver radiation damage is also a concern during distal esophageal cancer radiotherapy due to its proximity to the left liver lobe, typically included in the radiation field. Post-CRT, if FDG activity appears in the left or caudate liver lobes, a thorough investigation is needed to confirm or rule out distant metastases. The increased FDG uptake in liver lobes post-CRT often presents a diagnostic dilemma. Distinguishing between radiation-induced liver disease and metastasis is vital for appropriate patient management, necessitating a combination of imaging techniques and an understanding of the factors influencing the radiation response. Diagnosis involves identifying new foci of hepatic FDG avidity on PET/CT scans. Geographic regions of hypoattenuation on CT and well-demarcated regions with specific enhancement patterns on contrast-enhanced CT scans and MRI are characteristic of radiation-induced liver disease (RILD). Lack of mass effect on all three modalities (CT, MRI, PET) indicates RILD. Resolution of abnormalities on subsequent examinations also helps in diagnosing RILD. Moreover, it can also help to rule out occult metastases, thereby excluding those patients from further surgery who will not benefit from esophagectomy with curative intent.

Impact of positron-emission tomography on the surgical treatment of locoregionally recurrent colorectal cancer

BACKGROUND

The effect of positron emission tomography (PET) on the surgical treatment of locoregionally recurrent colorectal cancer (LRRCRC) remains unclear and warrants further investigation.

MATERIAL AND METHODS

A total of 193 patients with LRRCRC were identified from a prospectively maintained institutional database, of whom 134 LRRCRCs were deemed resectable and underwent resection with curative intent, whereas the remaining 59 LRRCRCs were unresectable. Patients with resectable LRRCRC were further classified according to whether recurrence was detected solely by PET (n = 35, PET-only group) or by a combination of computed tomography (CT)/magnetic resonance imaging (MRI) and PET (n = 99, CT/MRI/PET group). Clinicopathologic features, operative morbidity/mortality, and overall survival were compared between the patient groups based on long-term follow-up for at least 5 years.

RESULTS

Patients in the PET-only group tended to have less extensive organ resection (p = 0.0074), less blood loss (p < 0.0001), and shorter operation time and hospitalization (p < 0.0001), but surgical complication and readmission rates were not significantly different (p > 0.05) compared with the CT/MRI/PET group. Although the PET-only group had significantly higher R0 resection rate (80 % vs. 54.55 %, p = 0.0079), they also had a higher risk (17.14 % vs. 2.02 %, p = 0.0011) of sham operation. The estimated 5-year and 10-year survival rates significantly decreased in order (p < 0.0001) from PET-only (85.71 % and 57.98 %) and CT/MRI/PET (41.41 % and 15.93 %) to unresectable group of patients (16.95 % and 1.88 %). Subset analysis of the CT/MRI/PET group indicated that PET improved surgical decision-making because 24 (24.2 %) LRRCRCs that manifested on CT/MRI as equivocal lesions were later confirmed by PET as resectable recurrences, while 18 (19.4 %) LRRCRCs that manifested on CT/MRI as resectable lesions were later diagnosed by PET as more disseminated unresectable recurrences and precluded futile surgery.

CONCLUSION

PET alone can identify a subset (20.9 %) of LRRCRCs with less tumor burden for timely surgery; PET in combination with CT/MRI can better define the resectability of LRRCRCs. The positive impacts of PET can translate into better surgical outcomes, with enhanced safety and patient survival.

Can 18F-FDG PET/CT findings be used to predict orbital tumor histology?

PURPOSE

To investigate whether 18F-FDG PET/CT might be useful to predict the histology of various orbital tumors based on the maximum standard uptake value (SUVmax) and the OMSUV (orbital max SUV)/MLSUV (mean liver SUV) ratio.

PATIENTS AND METHODS

A retrospective single-center study was conducted between May 2019 and December 2020. Patients with an orbital mass who underwent preoperative 18F-FDG PET/CT followed by an orbital biopsy were included. Tumor histology was classified as follows: orbital inflammation, solid tumor, low-grade lymphoid tumor, and high-grade lymphoid tumor. Orbital tumors were also classified as indolent or aggressive. Data recorded included the orbital SUVmax, OMSUV/MLSUV ratio and additional extra-orbital SUV sites.

RESULTS

Forty-five patients (24 men) were included. There were 15 (33.3%), 14 (31.1%), 9 (20%), and 7 (15.5%) cases of orbital inflammation, solid tumor, low-grade lymphoid tumor, and high-grade lymphoid tumor, respectively. No correlation was found between the OMSUV/MLSUV ratio and orbital SUVmax and tumor histology (Z = -0.77, Z = -0.6, Z = -1.6, and Z = 0.94, all P > 0.05, respectively). No correlation was found between the OMSUV/MLSUV ratio (Z = -1.42, P > 0.05) and orbital SUVmax (Z = -0.82, P > 0.05) and tumor aggressiveness (indolent versus aggressive). Subgroup analyses showed that SUVmax was predictive of lymphoma aggressiveness (P = 0.05) and was able to distinguish orbital cancers (all lymphomas+solid tumors) from benign tumors (P = 0.02).

CONCLUSION

18F-FDG PET/CT could not be used to predict the underlying orbital tumor histology. However, more aggressive tumors, especially high-grade lymphomas and cancers, tended to have a higher orbital SUVmax compared to indolent lesions.

Staging of Cervical Cancer: A Practical Approach Using MRI and FDG PET

This review provides a practical approach to the imaging evaluation of patients with cervical cancer (CC), from initial diagnosis to restaging of recurrence, focusing on MRI and FDG PET. The primary updates to the International Federation of Gynecology and Obstetrics (FIGO) CC staging system, as well as these updates' relevance to clinical management, are discussed. The recent literature investigating the role of MRI and FDG PET in CC staging and image-guided brachytherapy is summarized. The utility of MRI and FDG PET in response assessment and posttreatment surveillance is described. Important findings on MRI and FDG PET that interpreting radiologists should recognize and report are illustrated. The essential elements of structured reports during various phases of CC management are outlined. Special considerations, including the role of imaging in patients desiring fertility-sparing management, differentiation of CC and endometrial cancer, and unusual CC histologies, are also described. Finally, future research directions including PET/MRI, novel PET tracers, and artificial intelligence applications are highlighted.

In vitro evaluation of (S)-2-amino-3-[3-(2-18F-fluoroethoxy)-4-iodophenyl]-2-methylpropanoic acid (18F-FIMP) as a positron emission tomography probe for imaging amino acid transporters

BACKGROUND

(S)-2-amino-3-[3-(2-¹⁸F-fluoroethoxy)-4-iodophenyl]-2-methylpropanoic acid (¹⁸F-FIMP) as a promising PET probe for imaging the tumor-specific L-type amino acid transporter (LAT) 1. Our previous study revealed that ¹⁸F-FIMP had a higher affinity for LAT1 than for LAT2 abundantly expressed even in normal cells. ¹⁸F-FIMP showed high accumulation in LAT1-positive tumor tissues and low accumulation in inflamed lesions in tumor-bearing mice. However, the affinity of ¹⁸F-FIMP for other amino acid transporters was not determined yet. Here, we aimed to determine whether ¹⁸F-FIMP has affinity for other tumor-related amino acid transporters, such as sodium- and chloride-dependent neutral and basic amino acid transporter B(0 +) (ATB^0,+), alanine serine cysteine transporter 2 (ASCT2), and cystine/glutamate transporter (xCT).

PROCEDURES

Cells overexpressing LAT1, ATB^0,+, ASCT2, or xCT were established by the transfection of expression vectors for LAT1, ATB^0,+, ASCT2, or xCT. Protein expression levels were determined by western blot and immunofluorescent analyses. Transport function was evaluated by a cell-based uptake assay using ¹⁸F-FIMP and ¹⁴C-labeled amino acids as substrates.

RESULTS

Intense signals were observed only for expression vector-transfected cells on western blot and immunofluorescent analyses. These signals were strongly reduced by gene-specific small interfering ribonucleic acid treatment. The uptake values for each ¹⁴C-labeled substrate were significantly higher in the transfected cells than in the mock-transfected cells and were significantly inhibited by the corresponding specific inhibitors. The ¹⁸F-FIMP uptake values were significantly higher in the LAT1- and ATB^0,+-overexpressing cells than in the corresponding mock cells, but no such increase was seen in the ASCT2- or xCT-overexpressing cells. These ¹⁸F-FIMP uptake values were significantly decreased by the specific inhibitors for LAT1- and ATB^0,+.

CONCLUSIONS

We demonstrated that ¹⁸F-FIMP has affinity not only for LAT1, but also for ATB^0,+. Our results may be helpful for understanding the mechanisms of the whole-body distribution and tumor accumulation of ¹⁸F-FIMP.

Can quantitative parameters of spectral computed tomography predict lymphatic metastasis in lung cancer? A systematic review and meta-analysis

BACKGROUND AND PURPOSE

This study evaluated the use of quantitative spectral computed tomography (CT) parameters to identify lymph node metastasis (LM) in lung cancer.

MATERIALS AND METHODS

Literature about LM in lung cancer diagnosed using spectral CT up to September 2022 was retrieved from the PubMed, EMBASE, Cochrane Library, Web of Science, Chinese National Knowledge Infrastructure, and Wanfang databases. The literature was strictly screened according to the inclusion and exclusion criteria. Data were extracted, quality assessment was performed, and heterogeneity was evaluated. The pooled sensitivity (SEN), specificity (SPE), positive likelihood ratio (+LR), -LR, and diagnostic odds ratio (DOR) for normalized iodine concentration (NIC) and spectral attenuation curve (λHU) were calculated. The subject receiver operating characteristic (SROC) curves were used, and the area under the curve (AUC) was calculated.

RESULTS

Eleven studies, including 1,290 cases, without obvious publication bias were enrolled. In eight articles, the pooled AUC of NIC in the arterial phase (AP) was 0.84 (SEN=0.85, SPE=0.74, +LR=3.3, -LR=0.20, DOR=16) while that of NIC in the venous phase (VP) was 0.82 (SEN=0.78, SPE=0.72). Additionally, the pooled AUC for λHU (AP) was 0.87 (SEN=0.74, SPE=0.84, +LR=4.5, -LR=0.31, DOR=15) and that for λHU (VP) was 0.81 (SEN=0.62, SPE=0.81). Lymph node (LN) short-axis diameter was ranked last, with a pooled AUC of 0.81 (SEN=0.69, SPE=0.79).

CONCLUSION

Spectral CT is a suitable noninvasive and cost-effective method for determining LM in lung cancer. Additionally, NIC and λHU in the AP have good discrimination ability than short-axis diameter, providing a valuable basis and reference for preoperative evaluation. (registration number INPLASY202290096).

Comparison of [18F]FIMP, [11C]MET, and [18F]FDG PET for early-phase assessment of radiotherapy response

Several limitations of [¹⁸F]FDG have been reported, such as nonspecific uptake of inflammation foci. Moreover, [¹¹C]MET has been found to accumulate in normal and inflammatory tissues as well as tumors. To increase specificity to tumor tissues, PET probes with tumor-specific molecular targets have been actively developed. [¹⁸F]FIMP was found to be highly accumulated in LAT1-positive tumors but not in inflamed tissue. The aim of this study was to explore whether [¹⁸F]FIMP can be used for the early-phase evaluation of radiotherapy accompanied by inflammation, and compare its effectiveness with those of [¹¹C]MET and [¹⁸F]FDG. Tumor uptake of [¹⁸F]FIMP decreased at day 1 after irradiation, and remained low until day 14. Comparatively, that of [¹⁸F]FDG initially decreased at day 3 but was transiently elevated at day 7 and then decreased again at day 10. Decreased tumor uptake of [¹¹C]MET was observed at day 10. In line with the uptake of [¹⁸F]FIMP, the ratio of Ki-67 immuno-positive cells in tumor tissues significantly decreased at day 1, 7, and 10 as compared with that in the control. These findings suggest that [¹⁸F]FIMP may be a PET probe involved in the early detection and prediction of radiotherapy efficacy, although further clarification is needed.

Updates in the management of unknown primary of the head and neck

Squamous cell carcinoma (SCC) from an unknown primary tumor (SCCUP) accounts for 2.0%–5.0% of all head and neck cancers. SCCUP presents as enlarged cervical lymph nodes without evidence of a primary tumor upon physical examination. Primary site detection is important to target treatment and avoid treatment-related morbidity. In this review, we discuss updates in SCCUP management. Diagnostic workup should focus on localization of the primary tumor in SCCUP. Initial workup centers on neck biopsy to confirm the presence of SCC. Given the increasing incidence of HPV-related SCC in the oropharynx, HPV testing is crucial. An HPV-positive status can localize the tumor to the oropharynx, a common site for occult tumors. Imaging includes neck CT and/or MRI, and PET/CT. After imaging, panendoscopy, palatine tonsillectomy or diagnostic transoral robotic surgery can facilitate high rates of primary tumor localization. Primary tumor localization influences treatments administered. SCCUP has traditionally been treated aggressively with large treatment fields to all potential disease sites, which can induce weight loss and swallowing dysfunction. As a result, primary localization can reduce radiation fields and provide possible de-escalation to primary surgical management. Advances in intensity-modulated radiation therapy and dose management also have the potential to improve functional outcomes in SCCUP patients. Given the improved prognosis associated with HPV-positive SCCs, HPV tumor status may also inform future treatment de-intensification to reduce treatment-related toxicity.

Combination of 18F-FDG PET/CT and convex probe endobronchial ultrasound elastography for intrathoracic malignant and benign lymph nodes prediction

Background

Positron emission tomography–computed tomography (PET/CT) and convex probe endobronchial ultrasound (CP-EBUS) elastography are important diagnostic methods in predicting intrathoracic lymph nodes (LNs) metastasis, but a joint analysis of the two examinations is still lacking. This study aimed to compare the diagnostic efficiency of the two methods and explore whether the combination can improve the diagnostic efficiency in differentiating intrathoracic benign LNs from malignant LNs.

Materials and Methods

LNs examined by EBUS-guided transbronchial needle aspiration (EBUS-TBNA) and PET/CT from March 2018 to June 2019 in Shanghai Chest Hospital were retrospectively analyzed as the model group. Four PET/CT parameters, namely, maximal standardized uptake value mean standardized uptake value (SUVmean), SUVmean, metabolic tumor volume (MTV), and tumor lesion glycolysis (TLG); four quantitative elastography indicators (stiff area ratio, mean hue value, RGB, and mean gray value); and the elastography grading score of targeted LNs were analyzed. A prediction model was constructed subsequently and the dataset from July to November 2019 was used to validate the diagnostic capability of the model.

Results

A total of 154 LNs from 135 patients and 53 LNs from 47 patients were enrolled in the model and validation groups, respectively. Mean hue value and grading score were independent malignancy predictors of elastography, as well as SUVmax and TLG of PET/CT. In model and validation groups, the combination of PET/CT and elastography demonstrated sensitivity, specificity, positive and negative predictive values, and accuracy for malignant LNs diagnosis of 85.87%, 88.71%, 91.86%, 80.88%, and 87.01%, and 94.44%, 76.47%, 89.47%, 86.67%, and 88.68%, respectively. Moreover, elastography had better diagnostic accuracies than PET/CT in both model and validation groups (85.71% vs. 79.22%, 86.79% vs. 75.47%).

Conclusion

EBUS elastography demonstrated better efficiency than PET/CT and the combination of the two methods had the best diagnostic efficacy in differentiating intrathoracic benign from malignant LNs, which may be helpful for clinical application.

First-in-human assessment of the novel LAT1 targeting PET probe 18F-FIMP

In the first-in-human PET study, we evaluated the biodistribution and tumor accumulation of the novel PET probe, (S)-2-amino-3-[3-(2-¹⁸F-fluoroethoxy)-4-iodophenyl]-2-methylpropanoic acid (¹⁸F-FIMP), which targets the tumor-related L-type amino acid transporter 1 (LAT1), and compared it with L-[methyl-¹¹C]methionine (¹¹C-MET) and 2-Deoxy-2-¹⁸F-fluoro-D-glucose (¹⁸F-FDG). ¹⁸F-FIMP biodistribution was revealed by whole-body and brain scans in 13 healthy controls. Tumor accumulation of ¹⁸F-FIMP was evaluated in 7 patients with a brain tumor, and compared with those of ¹¹C-MET and ¹⁸F-FDG. None of the subjects had significant problems due to probe administration, such as adverse effects or abnormal vital signs. ¹⁸F-FIMP was rapidly excreted from the kidneys to the urinary bladder. There was no characteristic physiological accumulation in healthy controls. ¹⁸F-FIMP PET resulted in extremely clear images in patients with suspected glioblastoma compared with ¹¹C-MET and ¹⁸F-FDG. ¹⁸F-FIMP could be a useful novel PET probe for LAT1-positive tumor imaging including glioblastoma.

Diffusion-weighted MRI-guided dose painting in patients with locoregionally advanced nasopharyngeal carcinoma treated with induction chemotherapy plus concurrent chemoradiotherapy: a randomized, controlled clinical trial

PURPOSES

We hypothesized that diffusion-weighted MRI (DWI)-guided dose-painting intensity modulated radiation therapy (DP-IMRT) is associated with improved local tumor control and survival in locoregionally advanced nasopharyngeal carcinoma (NPC). The purpose of this randomized study was to compare the efficacy and toxicity of DWI-guided DP-IMRT to conventional MRI-based IMRT in locoregional advanced NPC.

METHODS

A total of 260 NPC patients with stage III-IVa disease were randomly assigned in a 1:1 ratio to receive induction chemotherapy followed by chemoradiotherapy by DWI-guided DP-IMRT (group A, n = 130) or conventional MRI-based IMRT (group B, n = 130) in this prospective clinical trial. In group A, subvolume GTVnx-_DWI (gross tumor volume of nasopharynx in DWI) was defined as the areas within the GTV_nx (gross tumor volume of nasopharynx) with an apparent diffusion coefficient (ADC) below the mean ADC (ADC < mean) according to MRI before induction chemotherapy. The dose to GTVnx-_DWI was escalated to 75.2 Gy/32 Fx in patients with T1-2 disease and to 77.55 Gy/33 Fx in those with T3-4 disease in 2.35 Gy per fraction. In group B, PGTVnx was irradiated at 70.4-72.6 Gy/32-33 Fx in 2.2 Gy per fraction. This trial is registered with chictr.org.cn (number).

RESULTS

A total of 260 patients were included in the trial (130 patients in group A and 130 in group B). Complete response rates after chemoradiotherapy were 99.2% (129/130) and 93.8% (122/130) in groups A and B, respectively (P=0.042). At a median follow-up of 25 months, DWI-guided DP-IMRT was associated with improved 2-year disease-free survival (DFS, 93.6% [95% CI, 88.1% to 99.1%] vs. 87.5% [95% CI, 81.4% to 93.6%], P = 0.015), local recurrence-free survival (LRFS, 100% [95% CI, not applicable (NA)] vs. 91.3% [95% CI, 85.4% to 97.2%]), locoregional recurrence-free survival (LRRFS, 95.8% [95% CI, NA] vs. 91.3% [95% CI, 85.4% to 97.2%]), distant metastasis-free survival (DMFS, 97.8% [95% CI, NA] vs. 90.9% [95% CI, 85.8% to 96.0%]), and overall survival (OS, 100% [95% CI, NA] vs. 94.5% [95% CI, 89.2% to 99.8%]). There were 0 and 3 patients had local-only recurrences in group A and B, respectively. The most common site of first failure in each arm was distant organ failure. No statistically significant differences in acute and late toxic effects were observed. Multivariate analyses showed that dose painting (DWI-guided DP-IMRT vs conventional MRI-based IMRT without DP) was associated with DFS, LRFS, LRRFS and DMFS. EBV DNA level was associated with DFS and LRRFS.

CONCLUSIONS

DWI-guided DP-IMRT plus chemotherapy is associated with a disease-free survival benefit compared with conventional MRI-based IMRT among patients with locoregionally advanced NPC without increasing acute toxicity.

Lack of Clinical Utility of Labeled White Blood Cell Scintigraphy in Patients with Fever of Unknown Origin

Background

Labeled white blood cell scintigraphy (WBCS) has been used for over 40 years to localize an infection source in patients with fever of unknown origin (FUO). It continues to be in widespread use for such patients in modern times, despite the tremendous advances in modern radiological imaging and laboratory medicine.

Methods

We critically evaluated the clinical contribution of WBCS performed in 132 patients with FUO at 7 hospitals from mid-2015 to the end of 2019. For each patient, all radiographic and laboratory results and all electronic clinical notes were carefully evaluated as many days before and after the scan as necessary to arrive at a final diagnosis.

Results

Although 50 WBCS (38%) showed positive findings, the majority of these were false positive (FP). Of the 19 true-positive (TP) scans, most were already known or about to become known by tests already ordered at the time of the scan. Only 2 TP scans (1.5%) contributed to the final diagnosis, and these did so only indirectly. FP scans led to 7 unnecessary procedures.

Conclusions

In FUO patients for whom an infection source is not discovered following an appropriate radiographic and laboratory workup, WBCS is not a useful procedure.

Neuroinflammation and immunoregulation in glioblastoma and brain metastases: Recent developments in imaging approaches

Brain tumors and brain metastases induce changes in brain tissue remodeling that lead to immunosuppression and trigger an inflammatory response within the tumor microenvironment. These immune and inflammatory changes can influence invasion and metastasis. Other neuroinflammatory and necrotic lesions may occur in patients with brain cancer or brain metastases as sequelae from treatment with radiotherapy. Glioblastoma (GBM) is the most aggressive primary malignant brain cancer in adults. Imaging methods such as positron emission tomography (PET) and different magnetic resonance imaging (MRI) techniques are highly valuable for the diagnosis and therapeutic evaluation of GBM and other malignant brain tumors. However, differentiating between tumor tissue and inflamed brain tissue with imaging protocols remains a challenge. Here, we review recent advances in imaging methods that have helped to improve the specificity of primary tumor diagnosis versus evaluation of inflamed and necrotic brain lesions. We also comment on advances in differentiating metastasis from neuroinflammation processes. Recent advances include the radiosynthesis of ¹⁸ F-FIMP, an L-type amino acid transporter 1 (LAT1)-specific PET probe that allows clearer differentiation between tumor tissue and inflammation compared to previous probes, and the combination of different advanced imaging protocols with the inclusion of radiomics and machine learning algorithms.

Cancer cell metabolic plasticity in migration and metastasis

Metabolic reprogramming is a hallmark of cancer metastasis in which cancer cells manipulate their metabolic profile to meet the dynamic energetic requirements of the tumor microenvironment. Though cancer cell proliferation and migration through the extracellular matrix are key steps of cancer progression, they are not necessarily fueled by the same metabolites and energy production pathways. The two main metabolic pathways cancer cells use to derive energy from glucose, glycolysis and oxidative phosphorylation, are preferentially and plastically utilized by cancer cells depending on both their intrinsic metabolic properties and their surrounding environment. Mechanical factors in the microenvironment, such as collagen density, pore size, and alignment, and biochemical factors, such as oxygen and glucose availability, have been shown to influence both cell migration and glucose metabolism. As cancer cells have been identified as preferentially utilizing glycolysis or oxidative phosphorylation based on heterogeneous intrinsic or extrinsic factors, the relationship between cancer cell metabolism and metastatic potential is of recent interest. Here, we review current in vitro and in vivo findings in the context of cancer cell metabolism during migration and metastasis and extrapolate potential clinical applications of this work that could aid in diagnosing and tracking cancer progression in vivo by monitoring metabolism. We also review current progress in the development of a variety of metabolically targeted anti-metastatic drugs, both in clinical trials and approved for distribution, and highlight potential routes for incorporating our recent understanding of metabolic plasticity into therapeutic directions. By further understanding cancer cell energy production pathways and metabolic plasticity, more effective and successful clinical imaging and therapeutics can be developed to diagnose, target, and inhibit metastasis.

The impact of particulate electron paramagnetic resonance oxygen sensors on fluorodeoxyglucose imaging characteristics detected via positron emission tomography

During a first-in-humans clinical trial investigating electron paramagnetic resonance tumor oximetry, a patient injected with the particulate oxygen sensor Printex ink was found to have unexpected fluorodeoxyglucose (FDG) uptake in a dermal nodule via positron emission tomography (PET). This nodule co-localized with the Printex ink injection; biopsy of the area, due to concern for malignancy, revealed findings consistent with ink and an associated inflammatory reaction. Investigations were subsequently performed to assess the impact of oxygen sensors on FDG-PET/CT imaging. A retrospective analysis of three clinical tumor oximetry trials involving two oxygen sensors (charcoal particulates and LiNc-BuO microcrystals) in 22 patients was performed to evaluate FDG imaging characteristics. The impact of clinically used oxygen sensors (carbon black, charcoal particulates, LiNc-BuO microcrystals) on FDG-PET/CT imaging after implantation in rat muscle (n = 12) was investigated. The retrospective review revealed no other patients with FDG avidity associated with particulate sensors. The preclinical investigation found no injected oxygen sensor whose mean standard uptake values differed significantly from sham injections. The risk of a false-positive FDG-PET/CT scan due to oxygen sensors appears low. However, in the right clinical context the potential exists that an associated inflammatory reaction may confound interpretation.

FDG-Avid Lung Nodule Formation by the Use of Hemostatic Powder: A Potential Cause of False-Positive FDG PET/CT

ABSTRACT

FDG PET/CT is used in the diagnosis and follow-up of various malignant tumors and changes patient management in routine clinical practice. However, inflammatory, infectious, physiological, and technical causes and benign pathological conditions may lead to false-positive FDG uptake. We report a case of a 59-year-old man who was considered having a false-positive FDG-PET pulmonary nodular lesion in favor of metastasis, which was formed by the use of hemostatic powder.

18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging review of benign lesions of the thorax

2-deoxy-2-(Fluorine-18) fluoro-D-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) has been used exclusively to diagnose malignancies. However, increased ¹⁸F-FDG uptake is not always limited to malignant lesions. This imaging review demonstrates the physiological ¹⁸F-FDG uptake of normal structures in the thorax and illustrates many benign pathological lesions with standardized uptake value >2.5. These various conditions can be broadly categorized into three groups: infective lesions, active granulomatous diseases such as sarcoidosis, noninfectious/inflammatory, or proliferative conditions such as radiation pneumonitis, postlung transplant lymphoproliferative disorders, occupational pleuropulmonary complications, and postsurgical conditions, all of which can demonstrate varying degrees of ¹⁸F-FDG uptake on PET/CT based upon the degree of inflammatory activity. Familiarity of false-positive findings improves the PET/CT evaluation accuracy of benign lesions of the thorax. Radiation exposure and surgical history correlation along with imaging cross check evaluation of radiographs and magnetic resonance images for the anatomic location remains the mainstay of PET/CT characterization of positive findings.

[18F]FDG-PET or PET/CT in the evaluation of pelvic and para-aortic lymph nodes in patients with locally advanced cervical cancer: A systematic review of the literature

PURPOSE

Imaging is essential in detecting lymph node metastases for radiotherapy treatment planning in locally advanced cervical cancer (LACC). There are not many data on the performance of [¹⁸F]FDG-PET(CT) in showing lymph node metastases in LACC. We pooled sensitivity and specificity of [¹⁸F]FDG-PET(CT) for detecting pelvic and/or para-aortic lymph node metastases in patients with LACC. Also, the positive and negative posttest probabilities at high and low levels of prevalence were determined.

METHODS

MEDLINE and EMBASE searches were performed and quality characteristics assessed. Logit-sensitivity and logit-specificity estimates with corresponding standard errors were calculated. Summary estimates of sensitivity and specificity with corresponding 95% confidence intervals (CIs) were calculated by anti-logit transformation. Positive and negative likelihood ratios (LRs) were calculated from the mean logit-sensitivity and mean logit-specificity and the corresponding standard errors. The posttest probabilities were determined by Bayesian approach.

RESULTS

Twelve studies were included with a total of 778 patients aged 10-85 years. For pelvic nodes, summary estimates of sensitivity, specificity, LR+ and LR- were: 0.88 (95%CI: 0.40-0.99), 0.93 (95%CI: 0.85-0.97), 11.90 (95%CI: 5.32-26.62) and 0.13 (95%CI: 0.01-1.08). At the lowest prevalence of 0.15 the positive predictive value (PPV) and negative predictive value (NPV) were 0.68 and 0.98, at the highest prevalence of 0.65, 0.96 and 0.81. For the para-aortic nodes, the summary estimates of sensitivity, specificity LR+ and LR- were: 0.40 (95%CI: 0.18-0.66), 0.93 (95%CI: 0.91-0.95), 6.08 (95%CI: 2.90-12.78) and 0.64 (95%CI: 0.42-0.99), respectively. At the lowest prevalence of 0.17 the PPV and NPV were 0.55 and 0.88, at the highest prevalence of 0.50, 0.86 and 0.61.

CONCLUSION

The PPV and NPV of [¹⁸F]FDG-PET(CT) showing lymph node metastases in patients with LACC improves with higher prevalence. Prevalence and predictive values should be taken into account when determining therapeutic strategies based on [¹⁸F]FDG-PET(CT).

Applications of PET in Diagnosis and Prognosis of Leukemia

As a malignant hematopoietic stem cell disease, leukemia remains life-threatening due to its increasing incidence rate and mortality rate. Therefore, its early diagnosis and treatment play a very important role. In the present work, we systematically reviewed the current applications and future directions of positron emission tomography (PET) in patients with leukemia, especially ¹⁸F-FDG PET/CT. As a useful imaging approach, PET significantly contributes to the diagnosis and treatment of different types of leukemia, especially in the evaluation of extramedullary infiltration, monitoring of leukemia relapse, detection of Richter’s transformation (RT), and assessment of the inflammatory activity associated with acute graft versus host disease. Future investigations should be focused on the potential of PET/CT in the prediction of clinical outcomes in patients with leukemia and the utility of novel radiotracers.

Initial evaluation of (4S)-4-(3-[18F]fluoropropyl)-L-glutamate (FSPG) PET/CT imaging in patients with head and neck cancer, colorectal cancer, or non-Hodgkin lymphoma

Purpose

(4S)-4-(3-[¹⁸F]Fluoropropyl)-l-glutamic acid ([¹⁸F]FSPG) measures system x_C⁻ transporter activity and shows promise for oncologic imaging. We present data on tumor uptake of this radiopharmaceutical in human subjects with head and neck cancer (HNC), colorectal cancer (CRC), and non-Hodgkin lymphoma (NHL).

Methods

A total of 15 subjects with HNC (n = 5), CRC (n = 5), or NHL (n = 5) were recruited (mean age 66.2 years, range 44–87 years). 301.4 ± 28.1 MBq (8.1 ± 0.8 mCi) of [¹⁸F]FSPG was given intravenously to each subject, and 3 PET/CT scans were obtained 0–2 h post-injection. All subjects also had a positive [¹⁸F]FDG PET/CT scan within 1 month prior to the [¹⁸F]FSPG PET scan. Semi-quantitative and visual comparisons of the [¹⁸F]FSPG and [¹⁸F]FDG scans were performed.

Results

[¹⁸F]FSPG showed strong uptake in all but one HNC subject. The lack of surrounding brain uptake facilitated tumor delineation in the HNC patients. [¹⁸F]FSPG also showed tumor uptake in all CRC subjects, but variable uptake in the NHL subjects. While the absolute [¹⁸F]FDG SUV values were comparable or higher than [¹⁸F]FSPG, the tumor-to-background SUV ratios were greater with [¹⁸F]FSPG than [¹⁸F]FDG.

Conclusions

[¹⁸F]FSPG PET/CT showed promising results across 15 subjects with 3 different cancer types. Concordant visualization was mostly observed between [¹⁸F]FSPG and [¹⁸F]FDG PET/CT images, with some inter- and intra-individual uptake variability potentially reflecting differences in tumor biology. The tumor-to-background ratios were greater with [¹⁸F]FSPG than [¹⁸F]FDG in the cancer types evaluated. Future studies based on larger numbers of subjects and those with a wider array of primary and recurrent or metastatic tumors are planned to further evaluate the utility of this novel tracer.

Factors influencing incidental 18F-FDG uptake in the gallbladder in a large cohort of patients: A retrospective study

OBJECTIVES

This study aims to assess the incidence of incidental activity in the gallbladder and the factors that may contribute to it in a large cohort of patients undergoing ¹⁸F-fluorodeoxyglucose-PET/CT for cancer evaluation.

METHODS

8096 PET/CTs were retrospectively reviewed. Data pertaining to patient demographics and PET/CT parameters were collected. Patients' records were reviewed for gallbladder disorders for up to 3 years after the exam. The presence/absence of gallbladder uptake was visually assessed. Findings were classified as focal, diffuse increased and diffuse increased wall uptake, or no uptake. Volumetric measurements of the gallbladder and SUVmax of the gallbladder, liver and blood pool were measured. Chi-square and Student's t-test were used for statistical analysis.

RESULTS

54 cases (0.67%) of incidental gallbladder uptake were detected (uptake group). 162 exams without uptake were selected as control (no uptake group). The injection-to-scan interval, SUVmax of the liver and blood pool, and the gallbladder volume did not differ significantly between both groups. Higher blood glucose levels were observed in the uptake (109.9 ± 32.5) vs. no uptake group (97.4 ± 18) (p = 0.01), with levels >150 mg/dL more common in the uptake group (p = 0.004). The incidence of gallbladder disease within 3 years after imaging was higher for the uptake group (12/36) compared to the no uptake group (15/115) (p = 0.02). Diffuse increased wall uptake was more likely in the group who later developed a pathology (4/12) (p = 0.03).

CONCLUSION

Incidental gallbladder uptake in patients is independent of the injected FDG dose, injection-to-scan interval or gallbladder volume, but may be related to blood glucose level. There's a higher incidence of gallbladder pathology three years after the exam particularly in cases of diffuse increased wall uptake.

18F-FIMP: a LAT1-specific PET probe for discrimination between tumor tissue and inflammation

Positron emission tomography (PET) imaging can assist in the early-phase diagnostic and therapeutic evaluation of tumors. Here, we report the radiosynthesis, small animal PET imaging, and biological evaluation of a L-type amino acid transporter 1 (LAT1)-specific PET probe, ¹⁸F-FIMP. This probe demonstrates increased tumor specificity, compared to existing tumor-specific PET probes (¹⁸F-FET, ¹¹C-MET, and ¹⁸F-FDG). Evaluation of probes by in vivo PET imaging, ¹⁸F-FIMP showed intense accumulation in LAT1-positive tumor tissues, but not in inflamed lesions, whereas intense accumulation of ¹⁸F-FDG was observed in both tumor tissues and in inflamed lesions. Metabolite analysis showed that ¹⁸F-FIMP was stable in liver microsomes, and mice tissues (plasma, urine, liver, pancreas, and tumor). Investigation of the protein incorporation of ¹⁸F-FIMP showed that it was not incorporated into protein. Furthermore, the expected mean absorbed dose of ¹⁸F-FIMP in humans was comparable or slightly higher than that of ¹⁸F-FDG and indicated that ¹⁸F-FIMP may be a safe PET probe for use in humans. ¹⁸F-FIMP may provide improved specificity for tumor diagnosis, compared to ¹⁸F-FDG, ¹⁸F-FET, and ¹¹C-MET. This probe may be suitable for PET imaging for glioblastoma and the early-phase monitoring of cancer therapy outcomes.

Clinical impact of pre-treatment FDG-PET/CT staging of primary ovarian, fallopian tube, and peritoneal cancers in women

INTRODUCTION

To assess the clinical impact of preoperative fludeoxyglucose (FDG) with positron emission tomography (PET) and computed tomography (CT) in women with ovarian, fallopian tube, or peritoneal cancer with focus on consequences of added findings (AFs).

MATERIAL AND METHODS

FDG-PET/CT was implemented as a standard imaging modality for women with newly diagnosed ovarian, fallopian tube, or peritoneal cancer at our institution in 2008. After full implementation, all preoperative scans were reviewed and AFs were evaluated from January 2011 to December 2012. Decisions regarding further examination made at the first multidisciplinary team conference were recorded. Subsequent procedures were tracked via medical records, and the impact of AFs on additional examinations, delay, and change in treatment plans was evaluated.

RESULTS

Forty-four (21.1%) of 209 women presented with AFs. Further examination was performed in 35/44 (79.5%). Malignancy was identified in 15/35 (42.9%), revealing metastases from ovarian, fallopian tube, or peritoneal cancer in 11, a synchronous primary cancer in 3, and recurrence of a previous cancer in 1 woman. The ovarian, fallopian tube, or peritoneal cancer metastases were localized in the lungs, uterus, colon, vagina, and breasts. The remaining 20 AFs revealed 2 benign lesions and 1 pre-malignant lesion, whereas no abnormality was found in 17. Further examination of AFs resulted in a significant time delay until treatment start of median 4 days (range 1-83 days, P < 0.004).

CONCLUSIONS

Further examinations of AFs by FDG-PET/CT delayed time to start of treatment by median 4 days in women with newly diagnosed ovarian, fallopian tube, or peritoneal cancer in a contemporary institution with fast-track access to additional diagnostics. The clinical implications of this must be balanced against the gain of detecting unrecognized malignancy in 15 of 209 women (7.2%).

PET imaging of occult tumours by temporal integration of tumour-acidosis signals from pH-sensitive 64Cu-labelled polymers

Owing to the diversity of cancer types and the spatiotemporal heterogeneity of tumour signals, high-resolution imaging of occult malignancy is challenging. ¹⁸F-fluorodeoxyglucose positron emission tomography allows for near-universal cancer detection, yet in many clinical scenarios it is hampered by false positives. Here, we report a method for the amplification of imaging contrast in tumours via the temporal integration of the imaging signals triggered by tumour acidosis. This method exploits the catastrophic disassembly, at the acidic pH of the tumour milieu, of pH-sensitive positron-emitting neutral copolymer micelles into polycationic polymers, which are then internalized and retained by the cancer cells. Positron emission tomography imaging of the ⁶⁴Cu-labelled polymers detected small occult tumours (10-20 mm³) in the brain, head, neck and breast of mice at much higher contrast than ¹⁸F-fluorodeoxyglucose, ¹¹C-methionine and pH-insensitive ⁶⁴Cu-labelled nanoparticles. We also show that the pH-sensitive probes reduce false positive detection rates in a mouse model of non-cancerous lipopolysaccharide-induced inflammation. This macromolecular strategy for integrating tumour acidosis should enable improved cancer detection, surveillance and staging.

Diffusely Increased 18F-FDG Uptake in the Thyroid Gland and Risk of Thyroid Dysfunction: A Cohort Study

The impact of incidentally identified diffuse thyroid FDG uptake on ¹⁸F-FDG PET/CT scan on the incidence of thyroid dysfunction remains unclear. We examined the association of diffuse thyroid FDG uptake with the development of thyroid dysfunction. This cohort study involved 39,098 Korean adults who were free of malignancy and thyroid disease at baseline and underwent regular health checkup examinations including an ¹⁸F-FDG whole body PET/CT scan, thyroid-stimulating hormone and free thyroxine. The participants were annually or biennially followed for up to 5 years. A parametric proportional hazard model was used to estimate the adjusted hazard ratio (HR) and 95% confidence interval (CI). Diffuse thyroid uptake was positively associated with increased risk of thyroid dysfunction in both the cross-sectional and cohort studies. During 104,261.4 person-years of follow-up, 102 incident hypothyroidism cases and 172 hyperthyroidism cases were identified. Multivariable-adjusted HR (95% CI) for incident hypothyroidism or hyperthyroidism comparing diffuse thyroid uptake to no uptake were 15.72 (9.23–26.77) and 7.38 (4.23–12.87), respectively. In this large cohort, incidentally, identified diffuse thyroid uptake on ¹⁸F-FDG PET/CT was associated with increased risk of both prevalent and incident thyroid dysfunction. Therefore, baseline and follow-up evaluations in individuals with diffuse thyroid uptake may help identify individuals with thyroid dysfunction.

Colorectal Cancer:: Imaging Conundrums

Progressive technological advancements in imaging have significantly improved the preoperative sensitivity for the detection of very small foci of regionally- or hematogenously-metastatic colorectal cancer. Unfortunately, this information has not translated to continued linear gains in patient survival, and might even result in the false-positive upstaging of some cases: these are two conundrums in the imaging of colorectal cancer. Both conundrums might be resolved by the widespread use of real-time imaging guidance during operative procedures. This might open the way for the widespread use of fluorodeoxyglucose PET/CT for the initial staging of patients with colorectal cancer.

New pathogen-specific immunoPET/MR tracer for molecular imaging of a systemic bacterial infection

The specific and rapid detection of Enterobacteriaceae, the most frequent cause of gram-negative bacterial infections in humans, remains a major challenge. We developed a non-invasive method to rapidly detect systemic Yersinia enterocolitica infections using immunoPET (antibody-targeted positron emission tomography) with [64Cu]NODAGA-labeled Yersinia-specific polyclonal antibodies targeting the outer membrane protein YadA. In contrast to the tracer [18F]FDG, [64Cu]NODAGA-YadA uptake co-localized in a dose dependent manner with bacterial lesions of Yersinia-infected mice, as detected by magnetic resonance (MR) imaging. This was accompanied by elevated uptake of [64Cu]NODAGA-YadA in infected tissues, in ex vivo biodistribution studies, whereas reduced uptake was observed following blocking with unlabeled anti-YadA antibody. We show, for the first time, a bacteria-specific, antibody-based, in vivo imaging method for the diagnosis of a Gram-negative enterobacterial infection as a proof of concept, which may provide new insights into pathogen-host interactions.

Superiority of 68Ga-DOTATATE over 18F-FDG and anatomic imaging in the detection of succinate dehydrogenase mutation (SDHx )-related pheochromocytoma and paraganglioma in the pediatric population

PURPOSE

To evaluate and compare diagnostic performance of ⁶⁸Ga-DOTA(0)-Tyr(3)-octreotate (⁶⁸Ga-DOTATATE) with ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography-computed tomography (PET/CT) and anatomic imaging using computed tomography and/or magnetic resonance (CT/MR) imaging in detection of SDHx-related pheochromocytomas and paragangliomas (PPGLs) in pediatric patients.

METHODS

Nine pediatric patients (5:4, girls:boys; 14.6 ± 2.0 years) with an SDHx-related mutation (SDHB:SDHA:SDHD, n = 7:1:1) were included in this retrospective study. At the time of initial diagnosis, 7/9 patients had metastatic disease. They underwent CT/MR imaging along with PET/CT using ⁶⁸Ga-DOTATATE (n = 9), ¹⁸F-FDG (n = 8), and positron emission tomography-magnetic resonance imaging (PET/MR) using ¹⁸F-FDG (n = 1). In this manuscript, ¹⁸F-FDG PET/CT refers to both ¹⁸F-FDG PET/CT and ¹⁸F-FDG PET/MR. The per-lesion, per-region, and per-patient detection rates were compared and calculated for each of the imaging modalities. A composite of all functional and anatomic imaging studies served as the imaging comparator.

RESULTS

Eight out of nine patients were positive for PPGLs on the imaging studies that demonstrated 107 lesions in 22 anatomic regions on the imaging comparator. The per-lesion detection rates for ⁶⁸Ga-DOTATATE PET/CT, ¹⁸F-FDG PET/CT, and CT/MR imaging were 93.5% (95%CI, 87.0% to 97.3%); 79.4% (95%CI, 70.5% to 86.6%); and 73.8% (95%CI, 64.5% to 81.9%), respectively. The per-lesion detection rate for ⁶⁸Ga-DOTATATE PET/CT was significantly higher than that of ¹⁸F-FDG PET/CT (p = 0.001) or CT/MR imaging (p < 0.001). In all of the anatomic regions except abdomen, the per-lesion detection rates for ⁶⁸Ga-DOTATATE PET/CT was found to be equal or superior to ¹⁸F-FDG PET/CT, and CT/MR imaging. The per-region detection rate was 100% (95%CI, 84.6% to 100%) for ⁶⁸Ga-DOTATATE PET/CT and 90.9% (95%CI, 70.8% to 98.9%) for both ¹⁸F-FDG PET/CT and CT/MR imaging. The per-patient detection rates for ⁶⁸Ga-DOTATATE PET/CT, ¹⁸FDG PET/CT, and CT/MR imaging were all 100% (95%CI, 63.1% to 100%).

CONCLUSION

Our preliminary study demonstrates the superiority of ⁶⁸Ga-DOTATATE PET/CT in localization of SDHx-related PPGLs in pediatric population compared to ¹⁸F-FDG PET/CT and CT/MR imaging with the exception of abdominal (excluding adrenal and liver) lesions, and suggests that it might be considered as a first-line imaging modality in pediatric patients with SDHx-related PPGLs.

Impact of EBUS-TBNA on PET-CT Imaging of Mediastinal Nodes

BACKGROUND

Positron emission tomography-computed tomography (PET-CT) with fluorine-18-fluorodeoxyglucose has a high sensitivity in detecting malignancy in patients suspected of lung cancer but a low specificity as inflammatory reactions can also result in metabolic activity. Furthermore, it is assumed that invasive pulmonary procedures with biopsies from benign lesions can induce metabolic activity resulting in false-positive results. However, this hypothesis lacks solid evidence. We aimed to evaluate how often endobronchial ultrasound (EBUS) with biopsies from benign lesions are followed by false-positive results.

METHODS

Patients with suspected or proven lung cancer admitted for invasive pulmonary procedures in a 6-year period were retrospectively reviewed. Patients who had at least 1 nonmalignant mediastinal lymph node (MLN) biopsied 1 to 13 days before PET-CT were included. The number of false-positive and true-negative results shortly after EBUS biopsy of nonmalignant MLN was reviewed.

RESULTS

Of 1025 patients, 216 patients were referred for PET-CT 1 to 13 days after biopsy. Of these, 107 patients had at least 1 MLN biopsied. From a total of 198 biopsied MLNs, we found 62% without metabolic activity (benign) and 38% with metabolic activity. In 5% the metabolic activity could be explained by an infection or inflammatory disorder, in 15% no cytologic follow-up was available, in 1% malignancy was confirmed at follow-up, and in 3% the patients were not possible to follow-up. In the remaining 14%, no other reasonable explanation for the metabolic activity was found other than the biopsy.

CONCLUSIONS

EBUS with biopsy do not necessarily result in PET activity. Therefore, PET-positive results should always be taken seriously, even when PET is performed shortly after biopsies.

All That Glitters Is Not Gold" - A Case of an Occult Foreign Body in the Lung with Elevated 2-[18F]-Fluoro-2-deoxy-D-glucose (FDG) Uptake Mimicking Bronchogenic Carcinoma

Combined positron emission tomography/computed tomography (PET/CT) using the glucose analogue 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) has become the standard of care in oncological patients. However, due to the non-specific nature of FDG uptake, there are many physiological variants and benign pathological entities that also demonstrate augmented glucose metabolism, such as inflammatory and infective processes. Undiagnosed and retained foreign bodies (occult foreign bodies) in the lung can induce inflammatory reaction consisting of polymorphonuclear neutrophils, macrophages, and granulation tissue resulting in intense FDG uptake because of high metabolic activity and cell turnover. Here, we present a case of an occult foreign body imitating a tumor on PET/CT. 

Cat-Scratch Disease: A Pitfall for Lymphoma Evaluation by FDG-PET/CT

FDG-PET/CT is a standard of care in staging and response assessment of Hodgkin lymphoma. Hence, it is important to recognize pitfalls owing to the potential therapeutic impact. We report a case of a 29-year-old woman affected by stage III bulky Hodgkin lymphoma. The interim FDG-PET/CT showed a complete metabolic response. After three new cycles of chemotherapy, the patient showed fever and lymphadenopathy at clinic examination, PET/CT revealed several FDG uptakes at lymph nodes in inguinal and iliac region. Pathologic analyses, after biopsy and serologic examinations, led to the diagnosis of cat-scratch disease.

18F-FDG super bone marrow uptake: A highly potent indicator for the malignant infiltration

The present study was performed to investigate whether the markedly 2-deoxy-2-(fluorine-18) fluoro-D-glucose (F-FDG) uptake in the bone marrow (BM) is a presentation of malignant infiltration (MI).Super bone marrow uptake (super BMU) was used to name the markedly F-FDG uptake on BM, which was similar to or higher than that of the brain. From April 2008 to December 2015, 31 patients with such presentation were retrospectively reviewed. The F-FDG uptake was semiquantified using SUVmax and BM to cerebellum (BM/C) ratio. The origin of super BMU was diagnosed by pathology. Some blood parameters, as well as fever, were also collected and analyzed. For comparison, 106 patients with mildly and moderately uptake in BM and 20 healthy subjects were selected as the control group.Bone marrow MI was diagnosed in 93.5% (29/31) patients with super BMU, which mostly originated from acute leukemia and highly aggressive lymphoma. The super BMU group had markedly higher F-FDG uptake in the BM than those of mildly and moderately uptake, and the control subjects (all P = 0.000) and the BM/C ratio reached a high of 1.24 ± 0.36. The incidence of bone marrow MI in the super BMU group was markedly higher than that of mildly and moderately uptake (93.5% vs 36.8%, P = 0.000). Based on the receiver operating characteristic analysis, when cut-off values of BM/C and SUVmax were set at 0.835 and 6.560, the diagnostic specificity for bone marrow MI reached the high levels of 91.4% and 95.7%, respectively. In 15 patients with bone marrow MI, the extra-BM malignant lesions were simultaneously detected by F-FDG PET/CT. The liver and the nasal cavity involvements were only found in the patients with lymphoma, but not in those with leukemia. A decrease of leukocyte, hemoglobin, and platelet counts was noted in 48.4%, 86.2%, and 51.5% of patients with bone marrow MI, respectively.The present study revealed that super BMU was a highly potent indicator for the bone marrow MI.

Comparison of 11C-Methionine and 18F-FDG PET/CT for Staging and Follow-up of Pediatric Lymphoma

Methionine transport across plasma membranes occurs via the large amino acid transporter, which is overexpressed in malignant cells, leading to tracer accumulation within tumors. We investigated the uptake of ¹¹C-methionine (¹¹C-MET) in children and young adults with Hodgkin lymphoma (HL) or non-Hodgkin lymphoma (NHL) and compared the biodistribution of ¹¹C-MET PET/CT with that of ¹⁸F-FDG PET/CT. Methods: Conducted under an investigational new drug authorization, we prospectively enrolled patients with newly diagnosed HL (n = 19) and NHL (n = 2) onto the Institutional Review Board-approved investigation of ¹¹C-MET PET/CT. After a minimum 4-h fast, patients received 740 MBq/1.7 m² (maximum, 740 MBq [20 mCi/1.7 m²; maximum, 20 mCi]) of ¹¹C-methionine intravenously. PET/CT was performed 5 min after injection from the vertex to thighs at 3 min per bed position. In a separate session, patients received 5.5 MBq/kg (maximum, 485 MBq [0.15 mCi/kg; maximum, 12 mCi]) of ¹⁸F-FDG with imaging initiated approximately 1 h after radiopharmaceutical administration. All studies were reviewed by consensus of 2 senior imaging specialists. The presence of metabolic activity on baseline studies was compared among 17 nodal groups. Results: Eighteen patients (11 male; median age, 15.2 y; age range, 9.5-22.6 y) comprised the study cohort. All had paired ¹¹C-MET PET/CT and ¹⁸F-FDG PET/CT studies at diagnosis. At baseline, 3 nodal groups demonstrating discordant metabolic activity by both ¹⁸F-FDG PET/CT and ¹¹C-MET PET/CT were Waldeyer's ring, paraaortic region, and the liver. All others were found to have concordant metabolic activity. Normal intense ¹¹C-MET uptake in the pancreas and liver reduced sensitivity for disease detection in these regions. At follow-up, 14 of 15 study pairs had concordant results. Conclusion:¹¹C-MET uptake is elevated in most regions involved with lymphoma at diagnosis and follow-up. Its utility in the abdomen is limited by uptake in normal structures.

Pitfalls and Artifacts in the Use of PET/CT in Oncology Imaging

Accurate reporting of combined PET/CT imaging requires a thorough understanding of the normal and variant physiological distribution of tracers as well as common incidental findings and technical artifacts. We describe these pitfalls and artifacts, what action may help to mitigate them in clinical practice, and what further action may be appropriate. This review presents these in a region-based approach, in order to closely mimic clinical practice, and focuses on technical artifacts followed by a description of two commonly used oncologic tracers: FDG and choline.

18F-FDG-avid brunner gland hyperplasia

Brunner gland hyperplasia, a rare duodenal tumor, usually presents with benign features. A 68-year-old man with a history of anemia presented with a polypoid duodenal mass that was detected by CT and esophagogastroduodenoscopy. This mass showed high F-FDG avidity on PET/CT and was histopathologically confirmed as Brunner gland hyperplasia. We suggest that Brunner gland hyperplasia should be considered in the differential diagnosis of F-FDG-avid duodenal tumors.

Radiation dosimetry estimates of (18)F-alfatide II based on whole-body PET imaging of mice

We estimated the dosimetry of (18)F-alfatide II with the method established by MIRD based on biodistribution data of mice. Six mice (three females and three males) were scanned for 160min on an Inveon MicroPET/CT scanner after injection of (18)F-alfatide II via tail vein. Eight source organs were delineated on the CT images and their residence times calculated. The data was then converted to human using scaling factors based on organ and body weight. The absorbed doses for human and the resulting effective dose were computed by OLINDA 1.1 software. The highest absorbed doses was observed in urinary bladder wall (male 0.102mGy/MBq, female 0.147mGy/MBq); and the lowest one was detected in brain (male 0.0030mGy/MBq, female 0.0036). The total effective doses were 0.0127mSv/MBq for male and 0.0166 mSv/MBq for female, respectively. A 370-MBq injection of (18)F-alfatide II led to an estimated effective dose of 4.70mSv for male and 6.14mSv for female. The potential radiation burden associated with (18)F-alfatide II/PET imaging therefore is comparable to other PET examinations.

FDG PET/CT in infection and inflammation--current and emerging clinical applications

Integrated positron emission tomography/computed tomography (PET/CT) with the glucose analogue, 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG), is an evolving hybrid imaging technique in the evaluation of an important and diverse group of pathological conditions, which are characterised by infection and aseptic inflammation. With a rapidly expanding body of evidence, it is being increasingly recognised that, in addition to its established role in oncological imaging, FDG PET/CT also has clinical utility in suspected infection and inflammation. The technique can identify the source of infection or inflammation in a timely fashion ahead of morphological changes on conventional anatomical imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), map the extent and severity of disease, identify sites for tissue sampling, and assess therapy response. FDG PET/CT exhibits distinct advantages over traditional radionuclide imaging techniques in terms of shorter duration of examination, higher spatial resolution, non-invasive nature of acquisition, ability to perform quantitative analyses, and the provision of a synergistic combination of functional and anatomical imaging. With the use of illustrative clinico-radiological cases, this article discusses the current and emerging evidence for the use of FDG PET/CT in a broad spectrum of disorders, such as fever of unknown origin, sarcoidosis, large vessel vasculitis, musculoskeletal infections, joint prosthesis or implant-related complications, human immunodeficiency virus (HIV)-related infections, and miscellaneous indications, such as IgG4-related systemic disease. It will also briefly summarise the role of more novel tracers such as FDG-labelled leukocytes and gallium-68 PET tracers in this arena.

The added value of PET/Ce-CT/DW-MRI fusion in assessment of hepatic focal lesions: PET/Ce-CT/DW-MRI fusion in hepatic focal lesion

INTRODUCTION

The liver hosts a variety of benign and malignant tumors. Accurate diagnosis can be challenging in certain cases, especially in patients with a history of malignancy or in those with underlying liver pathology, such as cirrhosis.

OBJECTIVES

To evaluate the added clinical value of multi-modality liver imaging utilizing PET/Ce-CT/DW-MRI for characterization of hepatic focal lesions (HFL) and compare it with each diagnostic modality when interpreted alone.

METHODS

The study included 35 patients with HFL. They were 7 females & 28 males; their age ranged from 41 to 78years, all patients underwent PET/Ce-CT and DW-MRI scans. Ce-CT, PET and DW-MR images were reviewed independently, and then combined PET/Ce-CT, PET/DW-MRI and PET/Ce-CT/DW-MRI scans were analyzed. The results were correlated with histopathology or clinical/imaging follow-up.

RESULTS

The 35 patients had 98 focal lesions. Fifty-three lesions were finally diagnosed as primary hepatocellular carcinoma, 18 lesions were metastases, 7 lesions were lymphoma and 20 lesions were benign. On a patient based analysis; the sensitivity, specificity, PPV, NPV and accuracy were 100%, 67%, 94%, 100% and 94% for PET/Ce-CT compared to 97%, 83%, 97%, 83% and 94 % for DW-MRI, respectively. Combined PET/Ce-CT/DW-MR scans raise those parameters up to 100%. On a lesion based analysis; the sensitivity, specificity, PPV, NPV and accuracy were 94%, 75%, 94%, 75%, 90% for PET/Ce-CT compared to 94%, 95%, 99%, 97% and 94 % for DW-MRI, respectively. All these parameters were 100 % with PET/Ce-CT/DW-MRI.

CONCLUSIONS

The addition of DW-MRI to PET/Ce-CT is valuable in the characterization of hepatic focal lesions.

Novel imaging strategies for upper gastrointestinal tract cancers

Accurate pretherapeutic imaging is the cornerstone of all cancer treatment. Unfortunately, modern imaging modalities have several unsolved problems and limitations. The differentiation between inflammation and cancer infiltration, false positive and false negative findings as well as lack of confirming biopsies in suspected metastases may have serious negative consequences in cancer patients. This review describes some of these problems and challenges the use of conventional imaging by suggesting new combined strategies that include selective use of confirming biopsies and complementary methods to detect microscopic cancer dissemination.

PET-specific parameters and radiotracers in theoretical tumour modelling

The innovation of computational techniques serves as an important step toward optimized, patient-specific management of cancer. In particular, in silico simulation of tumour growth and treatment response may eventually yield accurate information on disease progression, enhance the quality of cancer treatment, and explain why certain therapies are effective where others are not. In silico modelling is demonstrated to considerably benefit from information obtainable with PET and PET/CT. In particular, models have successfully integrated tumour glucose metabolism, cell proliferation, and cell oxygenation from multiple tracers in order to simulate tumour behaviour. With the development of novel radiotracers to image additional tumour phenomena, such as pH and gene expression, the value of PET and PET/CT data for use in tumour models will continue to grow. In this work, the use of PET and PET/CT information in in silico tumour models is reviewed. The various parameters that can be obtained using PET and PET/CT are detailed, as well as the radiotracers that may be used for this purpose, their utility, and limitations. The biophysical measures used to quantify PET and PET/CT data are also described. Finally, a list of in silico models that incorporate PET and/or PET/CT data is provided and reviewed.

Clinical significance of patterns of incidental thyroid uptake at (18)F-FDG PET/CT

Incidental uptake of 2-[(18)F]-fluoro-2-deoxy-d-glucose ((18)F-FDG) in the thyroid gland is not uncommonly encountered in day-to-day practice of oncological (18)F-FDG positron-emission tomography/computed tomography (PET/CT). These are often felt to be "nuisance lesions" by referring clinicians and radiologists alike. However, recognition of the importance of different patterns of FDG uptake in the thyroid gland and knowledge of the possible underlying aetiologies are crucial in ensuring that patients are managed appropriately in the clinical context of their primary diagnosis, as the underlying pathological condition may be clinically important in a significant minority of such cases. This review describes the various patterns of (18)F-FDG uptake within the thyroid and discusses the clinical significance and possible impact on patient management. Incidental low-grade homogeneous diffuse increased thyroid (18)F-FDG uptake is usually seen in the patients with chronic thyroiditis, Grave's disease, and hypothyroidism. Thyroid function tests and antibody profiling are advised in these patients. Incidental focal (18)F-FDG thyroid uptake should raise the possibility of underlying malignancy. Ultrasound with or without fine-needle aspiration cytology is usually recommended for the evaluation of these lesions. Heterogeneous uptake with prominent focal uptake in the thyroid should be further evaluated to exclude malignancy.

Subdiaphragmatic gallstone mimicking hepatic malignancy on FDG PET/CT

A 70-year-old man underwent an FDG PET/CT for a possible primary liver malignancy or metastasis found on an abdominal MRI obtained as part of a workup for intermittent abdominal pain. The MRI showed an enhancing lesion at the dome of the right lobe of the liver. The lesion was FDG avid with a discrete central calcification. In conjunction with the patient's history of laparoscopic cholecystectomy 1 year prior, the findings were consistent with inflammation around a migrated subdiaphragmatic gallstone. One month after the scan, a CT-guided percutaneous biopsy of this lesion revealed chronic inflammatory cells with no evidence of malignancy.

Effects of intratumoral inflammatory process on 18F-FDG uptake: pathologic and comparative study with 18F-fluoro-α-methyltyrosine PET/CT in oral squamous cell carcinoma

The accurate depiction of both biologic and anatomic profiles of tumors has long been a challenge in PET imaging. An inflammation, which is innate in the carcinogenesis of oral squamous cell carcinoma (OSCC), frequently complicates the image analysis because of the limitations of (18)F-FDG and maximum standardized uptake values (SUV(max)). New PET parameters, metabolic tumor volume (MTV) and total lesion glycolysis (TLG), as well as (18)F-fluoro-α-methyltyrosine ((18)F-FAMT), a malignancy-specific amino acid-based PET radiotracer, are considered more comprehensive in tumor image analysis. Here, we showed the substantial effects of the intratumoral inflammatory process on (18)F-FDG uptake and further study the possibility of MTV and TLG to predict both tumor biology (proliferation activity) and anatomy (pathologic tumor volume).

METHODS

(18)F-FDG and (18)F-FAMT PET images from 25 OSCC patients were analyzed. SUV(max) on the tumor site was obtained. PET volume computerized-assisted reporting was used to generate a volume of interest to obtain MTV and TLG for (18)F-FDG and total lesion retention (TLR) for (18)F-FAMT. The whole tumor dissected from surgery was measured and sectioned for pathologic analysis of tumor inflammation grade and Ki-67 labeling index.

RESULTS

The high SUV(max) of (18)F-FDG was related to the high inflammation grade. The SUV(max )ratio of (18)F-FDG to (18)F-FAMT was higher in inflammatory tumors (P < 0.05) whereas the corresponding value in tumors with a low inflammation grade was kept low. All (18)F-FAMT parameters were correlated with Ki-67 labeling index (P < 0.01). Pathologic tumor volume predicted from MTV of (18)F-FAMT was more accurate (R = 0.90, bias = 3.4 ± 6.42 cm(3), 95% confidence interval = 0.77-6.09 cm(3)) than that of (18)F-FDG (R = 0.77, bias = 8.1 ± 11.17 cm(3), 95% confidence interval = 3.45-12.67 cm(3)).

CONCLUSION

(18)F-FDG uptake was overestimated by additional uptake related to the intratumoral inflammatory process, whereas (18)F-FAMT simply accumulated in tumors according to tumor activity as evaluated by Ki-67 labeling index in OSCC.

Ability of 18-fludeoxyglucose positron emission tomography/CT to detect incidental cancer

OBJECTIVE

To determine the prevalence and clinical features of pathologically proven incidental cancer (IC) detected by whole-body fluorine-18 fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)/CT, as well as the incidence of false-positive and false-negative results.

METHODS

We retrospectively reviewed reports derived from (18)F-FDG PET/CT images of 3079 consecutive patients with known or suspected malignancies for 3 years. Discrete focal uptake indicating IC was identified from reports as well as pathological or clinical diagnoses, and the clinical courses were investigated. The false-positive result was defined as uptake indicating IC but not pathologically confirmed as malignant during follow-up. The false-negative result was defined as pathologically proven IC detected by another modality at initial clinical work-up or diagnosed during the follow-up period.

RESULTS

We found (18)F-FDG uptake indicating IC in 6.7% of all patients, and IC was pathologically proven in 2.2% of all patients. The most common sites were the colon, lung and stomach. The median survival duration of patients with IC was 42 months. The results were false positive in 4.5% of all patients, and the results were false negative in 2.3% of all patients.

CONCLUSION

(18)F-FDG PET/CT is a valuable tool for detecting IC. The rates of false-positive and false-negative results are within acceptable range.

ADVANCES IN KNOWLEDGE

This is the first report to describe the survival of patients with IC, and the detailed features of false-negative results at actual clinical settings.

The clinical use of PET/CT in the evaluation of melanoma

Positron emission tomography combined with computed tomography (PET/CT) has emerged in the last decade as a dominant imaging modality used for staging, monitoring response and surveillance of various cancers, including melanoma. Using 2-deoxy-2-((18)F)fluoro-D-glucose ((18)F-FDG) as the radiopharmaceutical, PET/CT has demonstrated its efficacy and its utility in the management of patients with advanced melanoma. Nonetheless, challenges remain in the early stage evaluation of melanoma and in the development of novel radiotracers to better characterize lesions found on PET/CT. This chapter focuses on the advantages and limitations of this imaging modality in melanoma. We also detail and describe the approach to perform (18)F-FDG PET/CT, the methods to accurately quantify lesions, as well as the pearls/pitfalls of image interpretation. Finally, an overview of preclinical and investigational clinical radiopharmaceuticals is presented.