Factors affecting intrapatient liver and mediastinal blood pool ¹⁸F-FDG standardized uptake value changes during ABVD chemotherapy in Hodgkin's lymphoma

Reproducibility of [18F]FDG PET/CT liver SUV as reference or normalisation factor

INTRODUCTION

Although visual and quantitative assessments of [18F]FDG PET/CT studies typically rely on liver uptake value as a reference or normalisation factor, consensus or consistency in measuring [18F]FDG uptake is lacking. Therefore, we evaluate the variation of several liver standardised uptake value (SUV) measurements in lymphoma [18F]FDG PET/CT studies using different uptake metrics.

METHODS

PET/CT scans from 34 lymphoma patients were used to calculate SUVmaxliver, SUVpeakliver and SUVmeanliver as a function of (1) volume-of-interest (VOI) size, (2) location, (3) imaging time point and (4) as a function of total metabolic tumour volume (MTV). The impact of reconstruction protocol on liver uptake is studied on 15 baseline lymphoma patient scans. The effect of noise on liver SUV was assessed using full and 25% count images of 15 lymphoma scans.

RESULTS

Generally, SUVmaxliver and SUVpeakliver were 38% and 16% higher compared to SUVmeanliver. SUVmaxliver and SUVpeakliver increased up to 31% and 15% with VOI size while SUVmeanliver remained unchanged with the lowest variability for the largest VOI size. Liver uptake metrics were not affected by VOI location. Compared to baseline, liver uptake metrics were 15-18% and 9-18% higher at interim and EoT PET, respectively. SUVliver decreased with larger total MTVs. SUVmaxliver and SUVpeakliver were affected by reconstruction protocol up to 62%. SUVmax and SUVpeak moved 22% and 11% upward between full and 25% count images.

CONCLUSION

SUVmeanliver was most robust against VOI size, location, reconstruction protocol and image noise level, and is thus the most reproducible metric for liver uptake. The commonly recommended 3 cm diameter spherical VOI-based SUVmeanliver values were only slightly more variable than those seen with larger VOI sizes and are sufficient for SUVmeanliver measurements in future studies.

TRIAL REGISTRATION

EudraCT: 2006-005,174-42, 01-08-2008.

Radioembolization-Induced Changes in Hepatic [18F]FDG Metabolism in Non-Tumorous Liver Parenchyma

Background: [18F]FDG-PET/CT is increasingly used for response assessments after oncologic treatment. The known response criteria for [18F]FDG-PET/CT use healthy liver parenchyma as the reference standard. However, the [18F]FDG liver metabolism results may change as a result of the given therapy. The aim of this study was to assess changes in [18F]FDG liver metabolism after hepatic 90Y resin radioembolization. Methods: [18F]FDG-PET/CT scans prior to radioembolization and one and three months after radioembolization (consistent with the PERCIST comparability criteria), as well as 90Y-PET/CT scans, were analyzed using 3 cm VOIs. The FDG activity concentration and absorbed dose were measured. A linear mixed-effects logistic regression model and logistic mixed-effects model were used to assess the correlation between the FDG-activity concentration, absorbed dose, and biochemical changes. Results: The median SULVOI,liver at baseline was 1.8 (range = 1.2−2.8). The mean change in SULVOI,liver per month with an increase in time was 0.05 (95%CI 0.02−0.09) at p < 0.001. The median absorbed dose per VOI was 31.3 Gy (range = 0.1−82.3 Gy). The mean percent change in ΔSULVOI,liver for every Gy increase in the absorbed dose was −0.04 (95%CI −0.22−0.14) at p = 0.67. The SULblood and SULspleen results showed no increase. Conclusions: The [18F]FDG metabolism in the normal liver parenchyma is significantly but mildly increased after radioembolization, which can interfere with its use as a threshold for therapy response.

Intrapatient variability of 18F-FDG uptake in normal tissues

Objectives

To investigate the effect of serum glucose level and other confounding factors on the variability of maximum standardized uptake value (SUVmax) in normal tissues within the same patient on two separate occasions and to suggest an ideal reference tissue.

Materials and Methods

We retrospectively reviewed 334 18F-FDG PET/CT scans of 167 cancer patients including 38 diabetics. All patients had two studies, on average 152 ± 68 days apart. Ten matched volumes of interest were drawn on the brain, right tonsil, blood pool, heart, lung, liver, spleen, bone marrow, fat, and iliopsoas muscle opposite third lumber vertebra away from any pathological 18F-FDG uptake to calculate SUVmax.

Results

SUVmax of the lungs and heart were significantly different in the two studies (P = 0.003 and P = 0.024 respectively). Only the brain uptake showed a significant moderate negative correlation with the level of blood glucose in diabetic patients (r = −0.537, P = 0.001) in the first study, while the SUVmax of other tissues showed negligible or weak correlation with the level of blood glucose in both studies.

The liver showed significant moderate positive correlation with body mass index (BMI) in both studies (r = .416, P = <0.001 versus r = 0.453, P = <0.001, respectively), and blood pool activity showed significant moderate positive correlation with BMI in the first study only (r = 0.414, P = <0.001). The liver and blood pool activities showed significant moderate negative correlation with 18F-FDG uptake time in first study only (r = −0.405, P-value = <0.001; and r = −0.409, P-value = <0.001, respectively).

In the multivariate analysis, the liver showed a consistent effect of the injected 18F-FDG dose and uptake duration on its SUVmax on the two occasions. In comparison, spleen and muscle showed consistent effect only of the injected dose on the two occasions.

Conclusion

The liver, muscle, and splenic activities showed satisfactory test/retest stability and can be used as reference activities. The spleen and muscle appear to be more optimal reference than the liver, as it is only associated with the injected dose of 18F-FDG.

Detection of Splenic Tissue Using 99mTc-Labelled Denatured Red Blood Cells Scintigraphy—A Quantitative Single Center Analysis

Background: Red blood cells (RBC) scintigraphy can be used not only for detection of bleeding sites, but also of spleen tissue. However, there is no established quantitative readout. Therefore, we investigated uptake in suspected splenic lesions in direct quantitative correlation to sites of physiologic uptake in order to objectify the readout. Methods: 20 patients with Tc-99m-labelled RBC scintigraphy and SPECT/low-dose CT for assessment of suspected splenic tissue were included. Lesions were rated as vital splenic or non-splenic tissue, and uptake and physiologic uptake of bone marrow, pancreas, and spleen were then quantified using a volume-of-interest based approach. Hepatic uptake served as a reference. Results: The median uptake ratio was significantly higher in splenic (2.82 (range, 0.58–24.10), n = 47) compared to other lesions (0.49 (0.01–0.83), n = 7), p < 0.001, and 5 lesions were newly discovered. The median pancreatic uptake was 0.09 (range 0.03–0.67), bone marrow 0.17 (0.03–0.45), and orthotopic spleen 14.45 (3.04–29.82). Compared to orthotopic spleens, the pancreas showed lowest uptake (0.09 vs. 14.45, p = 0.004). Based on pancreatic uptake we defined a cutoff (0.75) to distinguish splenic from other tissues. Conclusion: As the uptake in extra-splenic regions is invariably low compared to splenules, it can be used as comparator for evaluating suspected splenic tissues.

Correlation between Reference Tissue Normalized 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Standardized Uptake Value Max of Nodal and Extranodal Sites in Lymphomas: An Empirical Study

Context:

Extranodal (EN) lymphomas involve sites other than lymph nodes (LNs), spleen, thymus, and the pharyngeal lymphatic ring. The highest standardized uptake value (SUV) max of the LN can aid in the diagnosis of EN site lymphomatous infiltrations over inflammation or infection especially when there are no contrast-enhanced computed tomography (CT) changes.

Aims:

The purpose of this study was to find the significance of correlation between absolute SUVmax and mediastinal blood pool (mbSUVmax) and liver (lvSUVmax) normalized SUVmax of EN sites and the most fluorodeoxyglucose (FDG) avid LN in patients with primary and secondary EN involvement in Non-Hodgkin's and Hodgkin's Lymphoma.

Settings and Design:

This was a retrospective study of 70 patients with histopathologically proven lymphoma in whom 18F-FDG positron emission tomography CT was performed for pretherapy staging.

Materials and Methods:

Images were used to detect EN sites of disease and SUVmax of mediastinal blood pool, liver, highest SUVmax LN, and highest SUVmax EN site were calculated.

Statistical Analysis Used:

Karl Pearson's coefficient of correlation (r) was used to correlate the highest SUV max of LN and EN site and corresponding highest blood pool corrected and liver corrected SUV max. In view of small sample size, t-test for paired samples at 5% and 10% significance was conducted to validate the findings. Two-tailed t-test for independent samples was also used to compare means of SUVmax values between data grouped according to gender and lymphoma subtype (Non-Hodgkin lymphoma and Hodgkin lymphoma).

Results:

r = 0.54 for the highest LN SUVmax-highest EN SUVmax values and on further validation by one- and two-tailed paired t-test at significance levels of 5% and 10%, P = 0.00052 and 0.00103 respectively which denoted significant positive and moderate correlation. r = 0.59 for highest LN lvSUVmax-highest EN vSUVmax and P = 0.00032 and 0.00065 showing positive and moderate correlation. r = 0 0.82 for highest LN mbSUVmax-highest EN mbSUVmax values and P = 0.00034 and 0.00068 revealing positive and strong correlation.

Conclusion:

Significant positive and strong correlation exists between nodal and EN mbsUVmax. This is stronger than the correlation between nodal and EN absolute SUVmax and lvSUVmax. Since normalization of lesion SUVmax to reference tissues reduces the variability of SUV, this can be a useful adjunct to determine whether high SUVmax of the EN site is due to lymphomatous infiltration.

Intrapatient repeatability of background 18F-FDG uptake on PET/CT

Background

Background activity is often used as a reference to assess tumor treatment response on positron emission tomography with 2-deoxy-2-[fluorine-18] fluoro-D-glucose integrated with computed tomography (18F-FDG PET/CT). Our objective was to find the preferred background by assessing the repeatability of its activity. The activity was expressed by a standardized uptake value normalized to lean body mass (SUL).

Methods

Patients who received repeat ¹⁸F-FDG PET/CT scans within 1 to 4 days were selected. The indications included cancer screening, tumor staging, or treatment response evaluation. Background SULs from the aortic blood pool (ABP), liver, and muscle were recorded. Intraclass correlation coefficients (ICCs), the coefficient of variation (CV), and Bland-Altman plots for repeated measures were used to evaluate the degree of repeatability between the two scans. Intrapatient variation in SULs and factors, including the blood glucose level (BGL), tracer uptake period, and dose, were calculated as relative changes between the two scans. A linear regression model was used to analyze all relative changes to identify the correlation between factors and SULs.

Results

Thirty patients were included. The SUL ICCs for the ABP, liver, and muscle were 0.65 (95% CI, 0.38-0.81), 0.47 (95% CI, 0.15-0.70), and 0.82 (95% CI, 0.65-0.91), respectively. The SUL coefficients of variation (CVs) were 9% for the ABP, 12% for the liver, and 10% for muscle. Similar results were obtained from the Bland-Altman plots. There was a positive correlation between the variations in the liver SUL and the BGL (b=0.60, P<0.01). A similar result was found between the variations in muscle SUL and the BGL (b=0.45, P<0.01). The variation in muscle SUL showed a positive correlation with the variation in the tracer uptake period (b=0.58, P<0.01).

Conclusions

The SUL of the liver is more sensitive to BGLs and, therefore, may not be suitable as a referential background. Activities within the ABP and muscle are more stable than those of the liver and should be used as the preferred background for sequential patient evaluation.

The effect of hypothyroidism on referential background metabolic activity on 18F-FDG PET/CT

Background

Background uptake activity is used as a reference to assess treatment response by positron emission tomography-computed tomography (PET/CT) with 2-deoxy-2-[F-18]fluoro- D-glucose (¹⁸F-FDG). Prior studies have reported decreased liver and increased muscle ¹⁸F-FDG uptake in patients with hyperthyroidism. We hypothesized that hyperthyroidism and hypothyroidism might have inverse effects on ¹⁸F-FDG uptake on PET/CT.

Methods

We recruited 36 patients with hypothyroidism and 36 age and gender-matched euthyroid participants. We recorded patient factors and background mean standardized uptake values normalized by lean body mass from the aortic blood pool, liver, and muscle. We compared the patient factors and background standardized uptake values normalized by lean body mass between hypothyroidism patients and the controls. We performed a multivariate analysis to determine the best predictors of the 3 different background standardized uptake values normalized by lean body mass.

Results

Patients with hypothyroidism had higher liver standardized uptake values normalized by lean body mass (1.77±0.33 vs. 1.58±0.26, P=0.009) and aortic blood-pool standardized uptake values normalized by lean body mass (1.21±0.22 vs. 1.11±0.20, P=0.040) than the controls. In contrast, the muscle standardized uptake value normalized by lean body mass (0.50±0.09 vs. 0.54±0.09, P=0.044) of the patients with hypothyroidism was lower than that of the controls. The serum level of thyroid-stimulating hormone was an independent predictor of liver standardized uptake values normalized by lean body mass (β=0.356, P<0.001) and blood-pool standardized uptake values normalized by lean body mass (β=0.288, P=0.001). The serum level of free triiodothyronine was an independent predictor of muscle standardized uptake values normalized by lean body mass (β=0.310, P=0.002).

Conclusions

PET/CT scans showed that hypothyroidism patients had increased liver and blood-pool ¹⁸F-FDG uptake and decreased skeletal muscle ¹⁸F-FDG uptake compared with euthyroid individuals. These alterations should be noted when a metabolic response to cancer treatment on PET/CT is determined.

High Basal Maximal Standardized Uptake Value (SUVmax) in Follicular Lymphoma Identifies Patients with a Low Risk of Long-Term Relapse

BACKGROUND

Despite that the unfavorable prognostic role of a high Total Metabolic Tumor Volume (TMTV) in Follicular Lymphoma has been demonstrated, the role of SUV_max alone at baseline PET/CT could have a different prognostic role.

PATIENTS AND METHODS

We performed a retrospective observational monocentric cohort study. All patients affected by FL who underwent a basal PET/CT were included. Two subgroups were identified and compared in terms of PFS and OS: (A) Basal SUV_max ≤ 6; and (B) Basal SUV_max > 6.

RESULTS

Ninety-four patients were included, 34 in group A (36.2%) and 60 in group B (63.8%). The PFS at two years was comparable in the two groups (97%). The five-year PFS was 73.5% for group A and 95% for group B (p 0.005). The five-year PFS in the whole cohort was 87.5%. A clear advantage was confirmed in group A in the absence of other risk factors. Patients with SUV_max ≤ 6 and no risk factors showed a 5-year PFS of 73% against 83% for patients with SUV_max > 6 and at least two risk factors.

CONCLUSION

A high FDG uptake favorably correlated with PFS. A low basal SUV_max reflected a higher rate of late relapse requiring a prolonged follow-up. The basal SUV_max is an approachable parameter with prognostic implications.

Age-related changes of standardized uptake values in the blood pool and liver: a decade-long retrospective study of the outcomes of 2,526 subjects

Background

Background activity on fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) is often used as a reference to assess a patient's response to tumor treatment. To produce a suitable background activity reference, we examined the variations in standardized uptake values (SUVs) in the blood pool and liver of a large multi-aged population.

Methods

A total of 2,526 subjects underwent ¹⁸F-FDG PET/CT examinations and were divided into 12 age groups. Pearson's partial correlation and multivariate regression analyses were performed to assess the associations between individual factors and SUVs of the blood pool and liver and to identify the factor that most influenced the SUVs. The mean SUVs across the age groups were also determined.

Results

Positive correlations were found between individual factors and SUVs. Age appeared to be the most important predictor of SUVs and was significantly associated with the blood pool SUV_max (ß=0.466, P=0.000), blood pool SUV_mean (ß=0.393, P=0.000), liver SUV_max (ß=0.347, P=0.000), and liver SUV_mean (ß=0.354, P=0.000). Blood pool and liver SUVs rose rapidly until the age of 20 and then showed a slow upward trend without reaching a plateau.

Conclusions

Age is an important factor that influences variations in the blood pool and liver SUVs. Our study clarified this understanding of age-related variations in SUVs and provided a normal range of blood pool and liver SUVs that may aid clinicians in evaluating tumors with greater accuracy.

The PET-Derived Tumor-to-Liver Standard Uptake Ratio (SUV TLR ) Is Superior to Tumor SUVmax in Predicting Tumor Response and Survival After Chemoradiotherapy in Patients With Locally Advanced Esophageal Cancer

Background: The maximum standardized uptake values (SUVmax) derived from ¹⁸F-fluorodeoxy-glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) have some well-known shortcomings in predicting treatment response and prognosis in oncology. The standardized SUVmax with an appropriate reference background may overcome this problem in some instances. This study explored the prognostic value of the tumor-to-liver SUVmax ratio (SUV_TLR) and the tumor-to-blood pool SUVmax ratio (SUV_TBR) in predicting the objective response (OR) and overall survival (OS) in patients with locally advanced esophageal cancer after concurrent chemoradiotherapy (CCRT).

Methods: We retrospectively analyzed 128 newly diagnosed esophageal squamous cell carcinoma (ESCC) patients who were treated with CCRT. The SUVmax of primary tumor, SUV_TLR, SUV_TBR and clinicopathologic features data were analyzed. Univariate and multivariate analyses were used to determine the predictors of tumor response. Survival analysis was performed using the Kaplan–Meier method and Cox proportional hazards model.

Results: Receiver operating characteristic (ROC) curve analysis demonstrated that SUV_TLR was superior to SUVmax and SUV_TBR in predicting treatment response. Univariate and multivariate analyses revealed that advanced tumor stage (hazard ratio [HR] = 9.67; 95% CI: 1.15-81.28; P = 0.037) and high SUV_TLR (HR = 21.92; 95% CI: 2.26-212.96; P = 0.008) were independent predictors of poor treatment response. Cox regression analysis showed that good clinical tumor response (p < 0.014, HR =0.501; 95% CI: 0.288–0.871) was a favorable independent predictive factor for OS, while an advanced tumor stage (p = 0.018, HR = 1.796; 95% CI: 1.107-2.915) and a high SUV_TLR (p < 0.002, HR = 2.660; 95% CI: 1.425–4.967) were prognostic factors for poor OS. The median OS of patients in the low SUV_TLR and high SUV_TLR groups was 13.47 vs. 19.30 months, respectively.

Conclusions: PET-derived SUV_TLR is superior to tumor SUVmax and SUV_TBR in predicting treatment response and overall survival in patients with ESCC undergoing CCRT. High SUV_TLR was an independent predictor of poor treatment response and shorter overall survival.

Improving the Prognostic Performance of SUVmax in 18F-Fluorodeoxyglucose Positron-Emission Tomography/Computed Tomography Using Tumor-to-Liver and Tumor-to-Blood Standard Uptake Ratio for Locally Advanced Cervical Cancer Treated with Concurrent Chemoradiotherapy

OBJECTIVE

We sought to evaluate whether the ¹⁸F-fluorodeoxyglucose uptake normalization of the primary tumor to both the liver and blood pool and lymph nodes to both the liver and blood pool can enhance the discrimination for prognosis prediction in patients with cervical cancer.

METHODS

A total of 156 patients with cervical cancer (International Federation of Gynecology and Obstetrics stages IIB-IV) treated with concurrent chemoradiotherapy (CCRT) were enrolled. The maximum standardized uptake value (SUV_max) of tumor (tSUV_max) and the lymph node (nSUV_max) divided by the SUV_mean of the liver (tumor-to-liver ratio (TLR) and node-to-liver (NLR)) and blood pool (tumor-to-blood ratio (TBR) and node-to-blood ratio (NBR)) were investigated. Univariate and multivariate analyses of disease-free survival (DFS) and overall survival (OS) were performed using clinical and metabolic parameters. A receiver operating characteristic curve analysis was performed to compare the accuracy of the metabolic parameters.

RESULTS

The multivariate analysis revealed that NLR (hazard ratio ((HR): 3.54; 95% confidence interval (CI): 1.53-8.19; p = 0.0032) and NBR (HR: 3.38; 95% CI: 1.02-11.19; p = 0.0457)) were independent prognostic factors for DFS, while TLR (HR: 4.16; 95% CI: 1.19-14.50; p = 0.0252), TBR (HR: 3.01; 95% CI: 1.04-8.70; p = 0.0415), NLR (HR: 4.84; 95% CI: 1.58-14.81; p = 0.0057), and NBR (HR: 6.87; 95% CI: 1.55-30.54; p = 0.0113) were significant prognostic factors for OS. The normalization of tSUV_max to the liver or blood pool enhanced the discrimination for prediction of recurrence (tSUV_max vs. TLR; p = 0.0056 and tSUV_max vs. TBR; p = 0.0099) and death (tSUV_max vs. TLR; p < 0.0001 and tSUV_max vs. TBR; p = 0.0001).

CONCLUSIONS

The normalization of tSUV_max was an independent prognostic factor and improved the discrimination for the prediction of tumor recurrence and death in patients with locally advanced cervical cancer treated with CCRT.

The Association Between Liver and Tumor [18F]FDG Uptake in Patients with Diffuse Large B Cell Lymphoma During Chemotherapy

PURPOSE

The aim of this study was to explore the association between liver, mediastinum and tumor 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) uptake during chemotherapy in diffuse large B cell lymphoma (DLBCL).

PROCEDURES

Nineteen patients with proven DLBCL underwent positron emission tomography (PET)/X-ray computed tomography scan at baseline, 1 week and 2 cycles after rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) therapy, and again after chemotherapy completion. The mean and maximal standardized uptake value (SUVmean and SUVmax) of the liver and mediastinum were measured and correlated with the tumor SUVmax, SUVsum, whole-body metabolic tumor volume (MTVwb), and total lesion glycolysis (TLG).

RESULTS

At baseline, both the liver and mediastinum SUVmean and SUVmax correlated inversely with the tumor MTVwb or TLG (p < 0.01 or 0.001). The liver SUVmean and SUVmax increased significantly after 1 week of R-CHOP therapy and remained at the high level until chemotherapy completion. The mediastinum SUVmean and SUVmax remained stable during chemotherapy. The tumor SUVmax, SUVsum, MTVwb, and TLG decreased significantly after 1 week of R-CHOP therapy. The change of the liver SUVmean correlated inversely with the change of tumor MTVwb and TLG after 1 week of chemotherapy (p < 0.05, respectively). The intersubject variability of liver and mediastinum [¹⁸F]FDG uptake ranged from 11 to 26 %.

CONCLUSIONS

The liver [¹⁸F]FDG uptake increased significantly after R-CHOP therapy. One of the possible reasons is the distribution of a greater fraction of the tracer to healthy tissues rather than tumor after effective chemotherapy. The variability of the liver [¹⁸F]FDG uptake during chemotherapy might affect the visual analysis of the interim PET scan and this needs to be confirmed in future studies with a large patient cohort. In addition, the intersubject variability of the liver and mediastinum [¹⁸F]FDG uptake should be considered.

Assessment of alteration in liver 18F-FDG uptake due to steatosis in lymphoma patients and its impact on the Deauville score

AIM

Our aim was (1) to evaluate the prevalence of steatosis in lymphoma patients and its evolution during treatment; (2) to evaluate the impact of hepatic steatosis on ¹⁸F-FDG liver uptake; and (3) to study how hepatic steatosis affects the Deauville score (DS) for discriminating between responders and non-responders.

METHODS

Over a 1-year period, 358 PET scans from 227 patients [122 diffuse large B cell lymphoma (DLBCL), 57 Hodgkin lymphoma (HL) and 48 Follicular lymphoma (FL)] referred for baseline (n = 143), interim (n = 79) and end-of-treatment (EoT, n = 136) PET scans were reviewed. Steatosis was diagnosed on the unenhanced CT part of PET/CT examinations using a cut-off value of 42 Hounsfield units (HU). EARL-compliant SUL_max were recorded on the liver and the tumour target lesion. DS were then computed.

RESULTS

Prevalence of steatosis at baseline, interim and EoT PET was 15/143 (10.5%), 6/79 (7.6%) and 16/136 (11.8%), respectively (p = 0.62).Ten out of 27 steatotic patients (37.0%) displayed a steatotic liver on all examinations. Six patients (22.2%) had a disappearance of hepatic steatosis during their time-course of treatment. Only one patient developed steatosis during his course of treatment. Liver SUL_max values were significantly lower in the steatosis versus non-steatotic groups of patients for interim (1.66 ± 0.36 versus 2.15 ± 0.27) and EoT (1.67 ± 0.29 versus 2.17 ± 0.30) PET. CT density was found to be an independent factor that correlated with liver SUL_max, while BMI, blood glucose level and the type of chemotherapy regimen were not. Using a method based on this correlation to correct liver SUL_max, all DS4 steatotic patients on interim (n = 1) and EoT (n = 2) PET moved to DS3.

CONCLUSIONS

Steatosis is actually a theoretical but not practical issue in most patients but should be recognised and corrected in appropriate cases, namely, for those patients scored DS4 with a percentage difference between the target lesion and the liver background lower than 30%.

Intra-patient Variability of FDG Standardized Uptake Values in Mediastinal Blood Pool, Liver, and Myocardium during R-CHOP Chemotherapy in Patients with Diffuse Large B-cell Lymphoma

PURPOSE

¹⁸F-fluorodeoxyglucose (FDG) PET/CT is useful for staging and evaluating treatment response in patients with diffuse large B-cell lymphoma (DLBCL). A five-point scale model using the mediastinal blood pool (MBP) and liver as references is a recommended method for interpreting treatment response. We evaluated the variability in standardized uptake values (SUVs) of the MBP, liver, and myocardium during chemotherapy in patients with DLBCL.

METHODS

We analyzed 60 patients with DLBCL who received rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) treatment and underwent baseline, interim, and final FDG PET/CT scans. The FDG uptakes of lymphoma lesions, MBP, liver, and myocardium were assessed, and changes in the MBP and liver SUV and possible associated factors were evaluated.

RESULTS

The SUV of the liver did not change significantly during the chemotherapy. However, the SUV_mean of MBP showed a significant change though the difference was small (p = 0.019). SUV_mean of MBP and liver at baseline and interim scans was significantly lower in patients with advanced Ann Arbor stage on diagnosis. The SUV_mean of the MBP and liver was negatively correlated with the volumetric index of lymphoma lesions in baseline scans (r = -0.547, p < 0.001; r = -0.502, p < 0.001). Positive myocardial FDG uptake was more frequently observed in interim and final scans than in the baseline scan, but there was no significant association between the MBP and liver uptake and myocardial uptake.

CONCLUSIONS

The SUV of the liver was not significantly changed during R-CHOP chemotherapy in patients with DLBCL, whereas the MBP SUV of the interim scan decreased slightly. However, the SUV of the reference organs may be affected by tumor burden, and this should be considered when assessing follow-up scans. Although myocardial FDG uptake was more frequently observed after R-CHOP chemotherapy, it did not affect the SUV of the MBP and liver.

Impact of PET/CT image reconstruction methods and liver uptake normalization strategies on quantitative image analysis

BACKGROUND

In oncological imaging using PET/CT, the standardized uptake value has become the most common parameter used to measure tracer accumulation. The aim of this analysis was to evaluate ultra high definition (UHD) and ordered subset expectation maximization (OSEM) PET/CT reconstructions for their potential impact on quantification.

PATIENTS AND METHODS

We analyzed 40 PET/CT scans of lung cancer patients who had undergone PET/CT. Standardized uptake values corrected for body weight (SUV) and lean body mass (SUL) were determined in the single hottest lesion in the lung and normalized to the liver for UHD and OSEM reconstruction. Quantitative uptake values and their normalized ratios for the two reconstruction settings were compared using the Wilcoxon test. The distribution of quantitative uptake values and their ratios in relation to the reconstruction method used were demonstrated in the form of frequency distribution curves, box-plots and scatter plots. The agreement between OSEM and UHD reconstructions was assessed through Bland-Altman analysis.

RESULTS

A significant difference was observed after OSEM and UHD reconstruction for SUV and SUL data tested (p < 0.0005 in all cases). The mean values of the ratios after OSEM and UHD reconstruction showed equally significant differences (p < 0.0005 in all cases). Bland-Altman analysis showed that the SUV and SUL and their normalized values were, on average, up to 60 % higher after UHD reconstruction as compared to OSEM reconstruction.

CONCLUSION

OSEM and HD reconstruction brought a significant difference for SUV and SUL, which remained constantly high after normalization to the liver, indicating that standardization of reconstruction and the use of comparable SUV measurements are crucial when using PET/CT.

Brain metabolic changes in Hodgkin disease patients following diagnosis and during the disease course: An 18F-FDG PET/CT study

The aim of the present study was to investigate brain glucose metabolism in patients with Hodgkin disease (HD) after diagnosis and during chemotherapy treatment. Following the administration of first-line doxorubicin, bleomycin, vinblastine and dacarbazine (ABVD) chemotherapy, 74 HD patients underwent ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography brain scans, both baseline (PET0) and interim (PET2) at the Department of Biomedicine and Prevention, University of Rome Tor Vergata (Rome, Italy). Fifty-seven patients were further evaluated 15±6 days after four additional cycles (PET6). Furthermore, a control group (CG) of 40 chemotherapy-naïve subjects was enrolled. Differences in brain ¹⁸F-FDG uptake between the CG, PET0, PET2 and PET6 scans were analyzed using statistical parametric mapping. Compared with the PET0 and CG scans, the PET2 scan demonstrated a higher metabolic activity in Brodmann area (BA) 39, and a metabolic reduction in BA 11 bilaterally and in left BA 32. All of these changes disappeared at PET6. The results of the present study indicate that ABVD chemotherapy has a limited impact on brain metabolism.

Initial staging of Hodgkin's disease: role of contrast-enhanced 18F FDG PET/CT

The objective of this study was to compare the diagnostic accuracy of positron emission tomography/low-dose computed tomography (PET/ldCT) versus the same technique implemented by contrast-enhanced computed tomography (ceCT) in staging Hodgkin's disease (HD).Forty patients (18 men and 22 women, mean age 30 ± 9.6) with biopsy-proven HD underwent a PET/ldCT study for initial staging including an unenhanced low-dose computed tomography for attenuation correction with positron emission tomography acquisition and a ceCT, performed at the end of the PET/ldCT scan, in the same exam session. A detailed datasheet was generated for illness locations for separate imaging modality comparison and then merged in order to compare the separate imaging method results (PET/ldCT and ceCT) versus merged results positron emission tomography/contrast-enhanced computed tomography (PET/ceCT). The nodal and extranodal lesions detected by each technique were then compared with follow-up data that served as the reference standard.No significant differences were found at staging between PET/ldCT and PET/ceCT in our series. One hundred and eighty four stations of nodal involvement have been found with no differences in both modalities. Extranodal involvement was identified in 26 sites by PET/ldCT and in 28 by PET/ceCT. We did not find significant differences concerning the stage (Ann Arbor).Our study shows a good concordance and conjunction between PET/ldCT and ceCT in both nodal and extranodal sites in the initial staging of HD, suggesting that PET/ldCT could suffice in most of these patients.

Do CSF levels of t-Tau, p-Tau and β₁₋₄₂ amyloid correlate with dopaminergic system impairment in patients with a clinical diagnosis of Parkinson disease? A ¹²³I-FP-CIT study in the early stages of the disease

PURPOSE

To investigate the relationships among cerebrospinal fluid (CSF) levels of t-Tau, p-Tau and Aβ₁₋₄₂ amyloid peptide and (123)I-FP-CIT uptake.

METHODS

The study included 58 subjects (31 men and 27 women, age 67 ± 9 years) with a clinical diagnosis of Parkinson disease diagnosed according to the United Kingdom Parkinson Disease Society Brain Bank criteria. All subjects underwent a CSF assay 28 ± 3 days before (123)I-FP-CIT SPECT scanning. The relationships were evaluated by means of linear regression analysis and Pearson correlation.

RESULTS

Striatal (123)I-FP-CIT was positively related to both t-Tau and p-Tau CSF values with low levels of t-Tau and p-Tau being related to a low uptake of (123)I-FP-CIT. In particular, differences with higher statistical significance were found for the striatum that is contralateral to theside mainly affected on clinical examination (P<0.001) [corrected].No significant relationships were found between Aβ₁₋₄₂ amyloid peptide and (123)I-FP-CIT binding.

CONCLUSION

The results of our study suggest that the presynaptic dopaminergic system is more involved in Parkinson disease patients with lower t-Tau and p-Tau CSF values while values of Aβ₁₋₄₂ amyloid peptide seems not to be related to nigrostriatal degeneration in our series.