Prognostic value of 18F-FDG PET/CT in patients with soft tissue sarcoma: comparisons between metabolic parameters

Objectives

To investigate the relationship between volume-based PET parameters and prognosis in patients with soft tissue sarcoma (STS).

Methods

We retrospectively reviewed 55 patients with pathologically proven STS who underwent pretreatment with ¹⁸?F-Fluorodeoxyglucose (¹⁸F-FDG) PET/CT. The maximum standardized uptake value (SUV_max), average SUV (SUV_avg), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of primary tumors were measured using a threshold SUV as liver activity for determining the boundary of tumors. Univariate and multivariate survival analyses for overall survival were performed according to the metabolic parameters and other clinical variables.

Results

Cancer-related death occurred in 19 of 55 patients (35 %) during the follow-up period (29?±?23 months). On univariate analysis, AJCC stage (stage IV vs. I-III, hazard ratio (HR)?=?2.837, p?=?0.028), necrosis (G2 vs. G0-G1, HR?=?3.890, p?=?0.004), SUV_max (1 unit - increase, HR?=?1.146, p?=?0.008), SUV_avg (1 unit - increase, HR?=?1.469, p?=?0.032) and treatment modality (non-surgical therapy vs. surgery, HR?=?4.467, p?=?0.002) were significant predictors for overall survival. On multivariate analyses, SUV_max (HR?=?1.274, p?=?0.015), treatment modality (HR?=?3.353, p?=?0.019) and necrosis (HR?=?5.985, p?=?0.006) were identified as significant independent prognostic factors associated with decreased overall survival.

Conclusions

The SUV_max of the primary tumor is a significant independent metabolic prognostic factor for overall survival in patients with STS. Volume-based PET parameters may not add prognostic information outside of the SUV_max.     

Anatomical and functional volume concordance between FDG PET,and T2 and diffusion-weighted MRI for cervical cancer: a hybrid PET/MR study

Purpose

To evaluate the concordance among ¹⁸F-FDG PET imaging, MR T2-weighted (T2-W) imaging and apparent diffusion coefficient (ADC) maps with diffusion-weighted (DW) imaging in cervical cancer using hybrid whole-body PET/MR.

Methods

This study prospectively included 35 patients with cervical cancer who underwent pretreatment ¹⁸F-FDG PET/MR imaging. ¹⁸F-FDG PET and MR images were fused using standard software. The percent of the maximum standardized uptake values (SUV_max) was used to contour tumours on PET images, and volumes were calculated automatically. Tumour volumes measured on T2-W and DW images were calculated with standard techniques of tumour area multiplied by the slice profile. Parametric statistics were used for data analysis.

Results

FDG PET tumour volumes calculated using SUV_max (14.30?±?4.70) and T2-W imaging volume (33.81?±?27.32 cm³) were similar (P?>?0.05) at 35 % and 40 % of SUV_max (32.91?±?18.90 cm³ and 27.56?±?17.19 cm³ respectively) and significantly correlated (P?<?0.001; r?=?0.735 and 0.766). The mean DW volume was 30.48?±?22.41 cm³. DW volumes were not significantly different from FDG PET volumes at either 35 % SUV_max or 40 % SUV_max or from T2-W imaging volumes (P?>?0.05). PET subvolumes with increasing SUV_max cut-off percentage showed an inverse change in mean ADC values on DW imaging (P?<?0.001, ANOVA).

Conclusion

Hybrid PET/MR showed strong volume concordance between FDG PET, and T2-W and DW imaging in cervical cancer. Cut-off at 35 % or 40 % of SUV_max is recommended for ¹⁸F-FDG PET/MR SUV-based tumour volume estimation. The linear tumour subvolume concordance between FDG PET and DW imaging demonstrates individual regional concordance of metabolic activity and cell density.     

Prediction of tumor differentiation using sequential PET/CT and MRI in patients with breast cancer

Objective

The aim of this study is to assess tumor differentiation using parameters from sequential positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) in patients with breast cancer.

Methods

This retrospective study included 78 patients with breast cancer. All patients underwent sequential PET/CT and MRI. For fluorodeoxyglucose (FDG)-PET image analysis, the maximum standardized uptake value (SUV_max) of FDG was assessed at both 1 and 2 h and metabolic tumor volume (MTV) and total lesion glycolysis (TLG). The kinetic analysis of dynamic contrast-enhanced MRI parameters was performed using dynamic enhancement curves. We assessed diffusion-weighted imaging (DWI)–MRI parameters regarding apparent diffusion coefficient (ADC) values. Histologic grades 1 and 2 were classified as low-grade, and grade 3 as high-grade tumor.

Results

Forty-five lesions of 78 patients were classified as histologic grade 3, while 26 and 7 lesions were grade 2 and grade 1, respectively. Patients with high-grade tumors showed significantly lower ADC-mean values than patients with low-grade tumors (0.99?±?0.19 vs.1.12?±?0.32, p?=?0.007). With respect to SUV_max1, MTV2.5, and TLG2.5, patients with high-grade tumors showed higher values than patients with low-grade tumors: SUV_max1 (7.92?±?4.5 vs.6.19?±?3.05, p?=?0.099), MTV2.5 (7.90?±?9.32 vs.4.38?±?5.10, p?=?0.095), and TLG2.5 (40.83?±?59.17 vs.19.66?±?26.08, p?=?0.082). However, other parameters did not reveal significant differences between low-grade and high-grade malignancies. In receiver-operating characteristic (ROC) curve analysis, ADC-mean values showed the highest area under the curve of 0.681 (95%CI 0.566–0.782) for assessing high-grade malignancy.

Conclusions

Lower ADC-mean values may predict the poor differentiation of breast cancer among diverse PET–MRI functional parameters.

     

Incidental pituitary uptake on whole-body 18F-FDG PET/CT: a multicentre study

Purpose

The purpose of this study was to determine the incidence of incidental pituitary uptake on whole-body ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and to investigate its clinical significance.

Methods

The files of 40,967 patients who underwent whole-body FDG PET/CT were retrospectively reviewed. Quantification of pituitary metabolic activity was obtained by using the maximum standardized uptake value (SUV_max). Hormone assays and pituitary MRIs were performed to assess pituitary lesions.

Results

Focally increased pituitary FDG uptake on PET/CT was found in 30 of 40,967 patients, accounting for an incidence of 0.073%. The mean SUV_max of 30 patients was 8.9?±?6.6 (range: 3.2–32.6). Histological diagnosis was obtained in three patients and included two growth hormone-secreting adenomas and one non-functioning adenoma. Hormone assays were performed on serum samples from 11 patients, 2 of whom were shown to have hypersecretion of pituitary hormone. MRI was performed on 19 patients. Abnormal MRI findings suggesting a pituitary mass were found in 18 of 19 cases (94.7%). The mean SUV_max calculated without correction for partial volume effect for macroadenomas was significantly higher than the SUV_max for microadenomas (11.5?±?8.4 vs 4.8?±?1.3; p?<?0.05). There were no cases diagnosed with metastasis to the pituitary gland during clinical follow-up.

Conclusion

Incidental pituitary FDG uptake was a very rare finding. Cases with incidental pituitary FDG uptake were diagnosed primarily with clinically non-functioning adenomas, and there were also a few functioning adenomas. Further evaluations, including hormone assays and pituitary MRI, are warranted when pituitary uptake is found on FDG PET/CT.     

Assessment of aortitis by semiquantitative analysis of 180-min 18F-FDG PET/CT acquisition images

Purpose

The aim of this study was to evaluate the contribution of semiquantitative analysis of 180-min ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT images for the assessment of aortitis in cases of suspected large vessel vasculitis (LVV) and to establish a threshold index for application in the clinical setting.

Methods

This prospective study included 43 patients (mean age 67.5?±?12.9?years) with suspicion of LVV (25 with a final diagnosis of aortitis). ¹⁸F-FDG PET/CT scan was acquired 180 min after injection of 7 MBq/kg of ¹⁸F-FDG. A semiquantitative analysis was performed calculating the aortic wall maximum standardized uptake value (SUV_max) (T), the lumen SUV_max (B) and the target to background ratio (TBR). These results were also compared with those obtained in a control population.

Results

The mean aortic wall SUV_max was 2.00?±?0.62 for patients with aortitis and 1.45?±?0.31 for patients without aortitis (p?p?max (0.997 vs 0.871). The highest sensitivity and specificity was obtained for a TBR of 1.34 (sensitivity 100 %, specificity 94.4 %).

Conclusion

Semiquantitative analysis of PET/CT images acquired 180 min after ¹⁸F-FDG injection and the TBR index of 1.34 show very high accuracy and, therefore, are strongly recommended for the diagnosis of aortitis in the clinical setting.     

Integrated 18F-FDG PET/perfusion CT for the monitoring of neoadjuvant chemoradiotherapy in rectal carcinoma: correlation with histopathology

Purpose

The aim of this study was to prospectively monitor changes in the flow-metabolic phenotype (ΔFMP) of rectal carcinoma (RC) after neoadjuvant chemoradiotherapy (CRT) and to evaluate whether ΔFMP of RC correlate with histopathological prognostic factors including response to CRT.

Methods

Sixteen patients with RC (12 men, mean age 60.7?±?12.8 years) underwent integrated ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/perfusion CT (PET/PCT), followed by neoadjuvant CRT and surgery. In 13 patients, PET/PCT was repeated after CRT. Perfusion [blood flow (BF), blood volume (BV), mean transit time (MTT)] and metabolic [maximum and mean standardized uptake values (SUV_max, SUV_mean)] parameters as well as the FMP (BF × SUV_max) were determined before and after CRT by two independent readers and correlated to histopathological prognostic factors of RC (microvessel density, necrosis index, regression index, vascular invasion) derived from resected specimens. The diagnostic performance of ΔFMP for prediction of treatment response was determined.

Results

FMP significantly decreased after CRT (p?<?0.001), exploiting higher changes after CRT as compared to changes of perfusion and metabolic parameters alone. Before CRT, no significant correlations were found between integrated PET/PCT and any of the histopathological parameters (all p?>?0.05). After CRT, BV and SUV_max correlated positively with the necrosis index (r?=?0.67/0.70), SUV_max with the invasion of blood vessels (r?=?0.62) and ΔFMP with the regression index (r?=?0.88; all p?<?0.05). ΔFMP showed high accuracy for prediction of histopathological response to CRT (AUC 0.955, 95 % confidence interval 0.833–1.000, p?<?0.01) using a cut-off value of ?75 %.

Conclusion

In RC, ΔFMP derived from integrated ¹⁸F-FDG PET/PCT is useful for monitoring the effects of neoadjuvant CRT and allows prediction of histopathological response to CRT.     

Quantitative assessment of atherosclerotic plaques on <Superscript>18</Superscript>F-FDG PET/MRI: comparison with a PET/CT hybrid system

Purpose

PET with ¹⁸F-FDG has the potential to assess vascular macrophage metabolism. ¹⁸F-FDG is most often used in combination with contrast-enhanced CT to localize increased metabolism to specific arterial lesions. Novel ¹⁸F-FDG PET/MRI hybrid imaging shows high potential for the combined evaluation of atherosclerotic plaques, due to the superior morphological conspicuity of plaque lesions. The purpose of this study was to evaluate the reliability and accuracy of ¹⁸F-FDG PET/MRI uptake quantification compared to PET/CT as a reference standard in patients with carotid atherosclerotic plaques.

Methods

The study group comprised 34 consecutive oncological patients with carotid plaques who underwent both PET/CT and PET/MRI with ¹⁸F-FDG on the same day. The presence of atherosclerotic plaques was confirmed by 3 T MRI scans. Maximum standardized uptake values (SUV_max) for carotid plaque lesions and the average SUV of the blood pool within the adjacent internal jugular vein were determined and target-to-blood ratios (TBRs, plaque to blood pool) were calculated.

Results

Atherosclerotic lesions with maximum colocalized focal FDG uptake were assessed in each patient. SUV_max values of carotid plaque lesions were significantly lower on PET/MRI than on PET/CT (2.3?±?0.6 vs. 3.1?±?0.6; P?<?0.01), but were significantly correlated between PET/CT and PET/MRI (Spearman’s r?=?0.67, P?<?0.01). In contrast, TBR_max values of plaque lesions were similar on PET/MRI and on PET/CT (2.2?±?0.3 vs. 2.2?±?0.3; P?=?0.4), and again were significantly correlated between PET/MRI and PET/CT (Spearman’s r?=?0.73, P?<?0.01). Considering the increasing trend in SUV_max and TBR_max values from early to delayed imaging time-points on PET/CT and PET/MRI, respectively, with continuous clearance of radioactivity from the blood, a slight underestimation of TBR_max values may also be expected with PET/MRI compared with PET/CT.

Conclusion

SUV_max and TBR_max values are widely accepted reference parameters for estimation of the radioactivity of atherosclerotic plaques on PET/CT. However, due to a systematic underestimation of SUV_max and TBR_max with PET/MRI, the optimal cut-off values indicating the presence of inflamed plaque tissue need to be newly defined for PET/MRI.

     

The role of early 18F-FDG PET/CT in prediction of progression-free survival after 90Y radioembolization: comparison with RECIST and tumour density criteria

Purpose

This study evaluated the ability of ¹⁸F-FDG PET/CT imaging to predict early response to ⁹⁰Y-radioembolization in comparison with contrast-enhanced CT (CECT) using RECIST and lesion density (Choi) criteria. Progression-free survival (PFS) in patients with liver metastases at 2?years and decline in tumour markers were the primary end-points of the study.

Methods

A total of 121 liver lesions were evaluated in 25 patients (14 men, 11 women) with liver-dominant metastatic colorectal cancer who underwent ¹⁸F-FDG PET/CT and CECT before and 6–8?weeks after treatment. Changes in SUV_max, tumour density measured in terms of Hounsfield units and the sum of the longest diameters (LD) were calculated for the target liver lesions in each patient. The patient responses to treatment were categorized using EORTC PET criteria, tumour density criteria (Hounsfield units) and RECIST, and were correlated with the responses of tumour markers and 2-year PFS using Kaplan-Meier plots and the log-rank test for comparison. Multivariate proportional hazards (Cox) regression analysis was performed to assess the effect of relevant prognostic factors on PFS.

Results

Using ¹⁸F-FDG PET/CT response criteria, 15 patients had a partial response (PR) and 10 patients had stable disease (SD), while using RECIST only 2 patients had a PR and 23 had SD. Two patients had a PR, 21 SD and 2 progressive disease using tumour density criteria. The mean changes in SUV_max, sum of the LDs and tumour density after treatment were 2.9?±?2.6, 7.3?±?14.4?mm and 1.9?±?13.18?HU, respectively. Patients who had a PR on ¹⁸F-FDG PET/CT had a mean decrease of 44.5?% in SUV_max compared to those with SD who had a decrease of only 10.3?%. The decreases in SUV_max and sum of the LDs were significant (p?p?p?>?0.1065). The responses on the ¹⁸F-FDG PET/CT studies were highly correlated with the responses of tumour markers (p?p?=?0.01 for CEA and p?=?0.02 for Ca19-9), while the responses on the CECT studies using both RECIST and tumour density criteria were not significantly correlated with the responses of tumour markers. The responses on ¹⁸F-FDG PET/CT studies also significantly predicted PFS (the median PFS in those with a PR was 12.0?months and in those with SD was 5?months, p?18F-FDG PET/CT studies and decreases in SUV_max of ≤2.0 were the strongest predictors of PFS.

Conclusion

Early response assessment to ⁹⁰Y-radioembolization using ¹⁸F-FDG PET/CT is superior to RECIST and tumour density, demonstrating a correlation with tumour markers and significantly predicting PFS in patients with liver metastases. This could enable early response-adapted treatment strategies to be employed.     

Diagnostic accuracy of 68Ga-DOTANOC PET/CT imaging in pheochromocytoma

Purpose

The purpose of the present study was to evaluate the diagnostic accuracy of ⁶⁸Ga-DOTANOC positron emission tomography (PET)/CT in patients with suspicion of pheochromocytoma.

Methods

Data of 62 patients [age 34.3?±?16.1 years, 14 with multiple endocrine neoplasia type 2 (MEN2)] with clinical/biochemical suspicion of pheochromocytoma and suspicious adrenal lesion on contrast CT (n?=?70), who had undergone ⁶⁸Ga-DOTANOC PET/CT, were retrospectively analyzed. PET/CT images were analyzed visually as well as semiquantitatively, with measurement of maximum standardized uptake value (SUV_max), SUV_mean, SUV_max/SUV_liver, and SUV_mean/SUV_liver. Results of PET/CT were compared with ¹³¹I-metaiodobenzylguanidine (MIBG) imaging, which was available in 40 patients (45 lesions). Histopathology and/or imaging/clinical/biochemical follow-up (minimum 6 months) was used as reference standard.

Results

The sensitivity, specificity, and accuracy of ⁶⁸Ga-DOTANOC PET/CT was 90.4, 85, and 88.7 %, respectively, on patient-based analysis and 92, 85, and 90 %, respectively, on lesion-based analysis. ⁶⁸Ga-DOTANOC PET/CT showed 100 % accuracy in patients with MEN2 syndrome and malignant pheochromocytoma. On direct comparison, lesion-based accuracy of ⁶⁸Ga-DOTANOC PET/CT for pheochromocytoma was significantly higher than ¹³¹I-MIBG imaging (91.1 vs 66.6 %, p?=?0.035). SUV_max was higher for pheochromocytomas than other adrenal lesions (p?=?0.005), MEN2-associated vs sporadic pheochromocytoma (p?=?0.012), but no difference was seen between benign vs malignant pheochromocytoma (p?=?0.269).

Conclusion

⁶⁸Ga-DOTANOC PET/CT shows high diagnostic accuracy in patients with suspicion of pheochromocytoma and is superior to ¹³¹I-MIBG imaging for this purpose. Best results of ⁶⁸Ga-DOTANOC PET/CT are seen in patients with MEN2-associated and malignant pheochromocytoma.     

Correlation between [18F]FDG PET/CT and volume perfusion CT in primary tumours and mediastinal lymph nodes of non-small-cell lung cancer

Purpose

The aim of this study was to investigate correlations between glucose metabolism as determined by [¹⁸F]FDG PET/CT and tumour perfusion as quantified by volume perfusion CT in primary tumours and mediastinal lymph nodes (MLN) of patients with non-small-cell lung cancer (NSCLC).

Methods

Enrolled in the study were 17 patients with NSCLC. [¹⁸F]FDG uptake was quantified in terms of SUV_max and SUV_avg. Blood flow (BF), blood volume (BV) and flow extraction product (K^trans) were determined as perfusion parameters. The correlations between the perfusion parameters and [¹⁸F]FDG uptake values were subsequently evaluated.

Results

For the primary tumours, no correlations were found between perfusion parameters and [¹⁸F]FDG uptake. In MLN, there were negative correlations between BF and SUV_avg (r?=??0.383), BV and SUV_avg (r?=??0.406), and BV and SUV_max (r?=??0.377), but not between BF and SUV_max, K^trans and SUV_avg, or K^trans and SUV_max. Additionally, in MLN with SUV_max >2.5 there were negative correlations between BF and SUV_avg (r?=??0.510), BV and SUV_avg (r?=??0.390), BF and SUV_max (r?=??0.536), as well as BV and SUV_max (r?=??0.346).

Conclusion

Perfusion and glucose metabolism seemed to be uncoupled in large primary tumours, but an inverse correlation was observed in MLN. This information may help improve therapy planning and response evaluation.     

Correlation of <Superscript>18</Superscript>F-FDG and <Superscript>11</Superscript>C-methionine uptake on PET/CT with Ki-67 immunohistochemistry in newly diagnosed intracranial meningiomas

Objective

We evaluated the uptake of 2-deoxy-2-¹⁸F-fluoro-d-glucose (FDG) and l-[methyl-¹¹C]-methionine (MET) in patients with newly diagnosed intracranial meningiomas and correlated the results with tumor proliferation.

Methods

Data from 22 patients with newly diagnosed intracranial meningioma (12 grade I and 10 grade II) who underwent both FDG and MET brain PET/CT studies were retrospectively analyzed. The PET images were evaluated by a qualitative method and semiquantitative analysis using standardized uptake value (SUV) (SUV_max and SUV_peak) and tumor-to-reference tissue ratio (T_max/N ratio and T_peak/N ratio). Proliferative activity as indicated by the Ki-67 index was estimated in tissue specimens.

Results

MET PET/CT showed a higher detection rate of meningioma than did FDG PET/CT (100 vs. 46%, respectively). The T_max/N ratio and T_peak/N ratio on MET PET/CT were significantly higher than those on FDG PET/CT (p?<?0.001 and p?<?0.001, respectively). There was a significant difference between grades I and II with respect to FDG SUVmax (p?=?0.003), FDG SUV_peak (p?=?0.003), FDG T_max/N ratio (p?=?0.02), FDG T_peak/N ratio (p?=?0.006), MET SUV_max (p?=?0.002), MET SUV_peak (p?=?0.002), MET T_max/N ratio (p?=?0.002), and MET T_peak/N ratio (p?=?0.002). There was a significant correlation between Ki-67 index and FDG PET/CT for SUV_max (p?=?0.02), SUV_peak (p?=?0.005), and T_peak/N ratio (p?=?0.05) and between Ki-67 index and MET PET/CT for SUV_max (p?=?0.004), SUV_peak (p?=?0.007), T_max/N ratio (p?=?0.002), and T_peak/N ratio (p?=?0.004).

Conclusion

MET PET/CT showed a high sensitivity compared with FDG PET/CT for detection of newly diagnosed WHO grades I and II intracranial meningiomas. Both FDG and MET uptake were found to be useful for evaluating tumor proliferation in meningiomas.

     

Evaluation of the PET component of simultaneous [18F]choline PET/MRI in prostate cancer: comparison with [18F]choline PET/CT

Purpose

The aim of this study was to evaluate the positron emission tomography (PET) component of [¹⁸F]choline PET/MRI and compare it with the PET component of [¹⁸F]choline PET/CT in patients with histologically proven prostate cancer and suspected recurrent prostate cancer.

Methods

Thirty-six patients were examined with simultaneous [¹⁸F]choline PET/MRI following combined [¹⁸F]choline PET/CT. Fifty-eight PET-positive lesions in PET/CT and PET/MRI were evaluated by measuring the maximum and mean standardized uptake values (SUV_max and SUV_mean) using volume of interest (VOI) analysis. A scoring system was applied to determine the quality of the PET images of both PET/CT and PET/MRI. Agreement between PET/CT and PET/MRI regarding SUV_max and SUV_mean was tested using Pearson’s product-moment correlation and Bland-Altman analysis.

Results

All PET-positive lesions that were visible on PET/CT were also detectable on PET/MRI. The quality of the PET images was comparable in both groups. Median SUV_max and SUV_mean of all lesions were significantly lower in PET/MRI than in PET/CT (5.2 vs 6.1, p?<?0.05 and 2.0 vs 2.6, p?<?0.001, respectively). Pearson’s product-moment correlation indicated highly significant correlations between SUV_max of PET/CT and PET/MRI (R?=?0.86, p?<?0.001) as well as between SUV_mean of PET/CT and PET/MRI (R?=?0.81, p?<?0.001). Bland-Altman analysis revealed lower and upper limits of agreement of ?2.77 to 3.64 between SUV_max of PET/CT vs PET/MRI and ?1.12 to +2.23 between SUV_mean of PET/CT vs PET/MRI.

Conclusion

PET image quality of PET/MRI was comparable to that of PET/CT. A highly significant correlation between SUV_max and SUV_mean was found. Both SUV_max and SUV_mean were significantly lower in [¹⁸F]choline PET/MRI than in [¹⁸F]choline PET/CT. Differences of SUV_max and SUV_mean might be caused by different techniques of attenuation correction. Furthermore, differences in biodistribution and biokinetics of [¹⁸F]choline between the subsequent examinations and in the respective organ systems have to be taken into account.     

Dual-time-point F-18 FDG PET/CT for evaluation in patients with malignant lymphoma

Objective

The aim of this study was to evaluate the usefulness of F-18 fluorodeoxyglucose (FDG) dual-time-point (DTP) positron emission tomography (PET)/computed tomography (CT) with semiquantitative analyses for the initial staging in patients with malignant lymphoma.

Methods

Forty-three patients had DTP PET/CT, with 60-min and 2-h scan [n?=?8, Hodgkin??s lymphoma (HL); n?=?12, indolent non-Hodgkin lymphoma (NHL); n?=?23, aggressive NHL].

Results

A total of 524 lesions were evaluated (406 lymph nodes and 118 extra-nodal lesions). The maximum standardized uptake value (SUV_max) on 2-h delayed scan (SUV₂) was significantly higher than those on 1-h early scan (SUV₁) for all groups (P?<?0.0001 for HL; P?<?0.0001 for indolent NHL; P?<?0.0001 for aggressive NHL). Significant differences were detected between HL and indolent NHL, between indolent NHL and the aggressive NHL for both SUV₁ and SUV₂ (each P?<?0.0001). No significant differences were detected between HL and aggressive NHL for both SUV₁ and SUV₂ (P?=?0.6891 for SUV₁; P?=?0.8828 for SUV₂); however, significant differences were detected for the retention index of SUV_max between these groups (P?=?0.0238).

Conclusions

DTP F-18 FDG PET/CT with a semiquantitative technique may have the potential to provide the more accurate diagnoses for the staging of malignant lymphoma and the more important role in predicting the histological grades of malignancy compared with single-time-point F-18 FDG-PET scan.     

Reevaluation of FDG-PET/CT in patients with hoarseness caused by vocal cord palsy

Objective

Vocal cord palsy (VCP) is a potential cause of hoarseness that results in decreasing mobility of the vocal cord. VCP can arise from a variety of causes; so, systematic screening is warranted for the management of patients with VCP. Asymmetrical fluorodeoxyglucose (FDG) uptake in vocal cords is a well-known feature in patients with VCP, but no detailed analysis has been performed. This study aimed at reevaluating the ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) for patients with VCP.

Methods

We retrospectively surveyed the results of FDG-PET/CT for 59 patients with VCP, compared to laryngoscopic findings. Quantitative analysis was performed using maximum standardized uptake value (SUV_max), and regions of interest were drawn over bilateral vocal cords as confirmed from the CT portion of PET/CT. Patients were divided into 3 groups: Group 1 (n?=?14), in which VCP was caused by the lesion of the laryngeal area; Group 2 (n?=?40), in which VCP was caused by the lesion on the root of the recurrent laryngeal nerve; and Group 3 (n?=?5), in which VCP was caused by the lesion from the vagal center to the proximal vagus nerve.

Results

For Group 1, higher FDG uptake in the paralyzed vocal cord was seen in 86?% of patients (mean SUV_max 8.1?±?5.3 vs. 2.3?±?0.4, paralyzed vs. non-paralyzed, respectively; P?<?0.002). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 79?% for Group 1. Group 2 showed dominant FDG uptake in the non-paralyzed vocal cord (mean SUV_max 2.1?±?0.9 vs. 1.5?±?0.4, non-paralyzed vs. paralyzed, respectively; P?<?0.001). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 93?% for Group 2. Group 3 showed no statistically significant difference in FDG accumulation between non-paralyzed and paralyzed vocal cords (mean SUV_max 1.8?±?0.3 vs. 1.7?±?0.3, non- paralyzed vs. paralyzed, respectively; P?=?0.30). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 60?% for Group 3.

Conclusions

FDG accumulation in the vocal cords is dependent on the lesion site causing VCP. In addition, FDG-PET/CT can contribute to identification of the lesion responsible for inducing VCP.     

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

Purpose

The aim of our study was to assess the intrapatient variability of 2-deoxy-2-(¹⁸F)-fluoro-D-glucose (¹⁸F-FDG) uptake in the liver and in the mediastinum among patients with Hodgkin’s lymphoma (HL) treated with doxorubicin (Adriamycin), bleomycin, vinblastine and dacarbazine (ABVD) chemotherapy (CHT).

Methods

The study included 68 patients (30 men, 38 women; mean age 32?±?11 years) with biopsy-proven HL. According to Ann Arbor criteria, 6 were stage I, 34 were stage II, 12 were stage 3 and 16 were stage 4. All of them underwent a baseline (PET0) and an interim (PET2) ¹⁸F-FDG whole-body positron emission tomography (PET)/CT. All patients were treated after PET0 with two ABVD cycles for 2 months that ended 15?±?5 days prior to the PET2 examination. All patients were further evaluated 15?±?6 days after four additional ABVD cycles (PET6). None of the patients presented a serum glucose level higher than 107 mg/dl. The mean and maximum standardized uptake values (SUV) of the liver and mediastinum were calculated using the same standard protocol for PET0, PET2 and PET6, respectively. Data were examined by means of the Wilcoxon matched pairs test and linear regression analysis.

Results

The main results of our study were an increased liver SUV_mean in PET2 (1.76?±?0.35) as compared with that of PET0 (1.57?±?0.31; p?<?0.0001) and PET6 (1.69?±?0.28; p?=?0.0407). The same results were obtained when considering liver SUV_max in PET2 (3.13?±?0.67) as compared with that of PET0 (2.82?±?0.64; p?<?0.0001) and PET6 (2.96?±?0.52; p?=?0.0105). No significant differences were obtained when comparing mediastinum SUV_mean and SUV_max in PET0, PET2 and PET6 (p?>?0.05). Another finding is a relationship in PET0 between liver SUV_mean and SUV_max with the stage, which was lower in those patients with advanced disease (r ²?=?0.1456 and p?=?0.0013 for SUV_mean and r ²?=?0.1277 and p?=?0.0028 for SUV_max).

Conclusion

The results of our study suggest that liver ¹⁸F-FDG uptake is variable in patients with HL during the CHT treatment and the disease course and should be considered carefully when used to define the response to therapy in the interim PET in HL.     

Comparison of lesion detection and quantitation of tracer uptake between PET from a simultaneously acquiring whole-body PET/MR hybrid scanner and PET from PET/CT

Purpose

PET/MR hybrid scanners have recently been introduced, but not yet validated. The aim of this study was to compare the PET components of a PET/CT hybrid system and of a simultaneous whole-body PET/MR hybrid system with regard to reproducibility of lesion detection and quantitation of tracer uptake.

Methods

A total of 46 patients underwent a whole-body PET/CT scan 1?h after injection and an average of 88?min later a second scan using a hybrid PET/MR system. The radioactive tracers used were ¹⁸F-deoxyglucose (FDG), ¹⁸F-ethylcholine (FEC) and ⁶⁸Ga-DOTATATE (Ga-DOTATATE). The PET images from PET/CT (PET_CT) and from PET/MR (PET_MR) were analysed for tracer-positive lesions. Regional tracer uptake in these foci was quantified using volumes of interest, and maximal and average standardized uptake values (SUV_max and SUV_avg, respectively) were calculated.

Results

Of the 46 patients, 43 were eligible for comparison and statistical analysis. All lesions except one identified by PET_CT were identified by PET_MR (99.2?%). In 38 patients (88.4?%), the same number of foci were identified by PET_CT and by PET_MR. In four patients, more lesions were identified by PET_MR than by PET_CT, in one patient PET_CT revealed an additional focus compared to PET_MR. The mean SUV_max and SUV_avg of all lesions determined by PET_MR were by 21?% and 11?% lower, respectively, than the values determined by PET_CT (p?<?0.05), and a strong correlation between these variables was identified (Spearman rho 0.835; p?<?0.01).

Conclusion

PET/MR showed equivalent performance in terms of qualitative lesion detection to PET/CT. The differences demonstrated in quantitation of tracer uptake between PET_CT and PET_MR were minor, but statistically significant. Nevertheless, a more detailed study of the quantitative accuracy of PET_MR and the factors governing it is needed to ultimately assess its accuracy in measuring tissue tracer concentrations.     

Functional imaging of head and neck squamous cell carcinoma with diffusion-weighted MRI and FDG PET/CT: quantitative analysis of ADC and SUV

Purpose

Head and neck squamous cell carcinoma (HNSCC) may cause a decreased apparent diffusion coefficient (ADC) on diffusion-weighted magnetic resonance imaging (DW MRI) and an increased standardized uptake value (SUV) on fluorodeoxyglucose (FDG) positron emission tomography (PET/CT). We analysed the reproducibility of ADC and SUV measurements in HNSCC and evaluated whether these biomarkers are correlated or independent.

Methods

This retrospective analysis of DW MRI and FDG PET/CT data series included 34 HNSCC in 33 consecutive patients. Two experienced readers measured tumour ADC and SUV values independently. Statistical comparison and correlation with histopathology was done. Intra- and inter-observer agreement for ADC and SUV measurements was assessed.

Results

Intraclass correlation coefficient (ICC) analysis showed almost perfect reproducibility (>0.90) for ADC_mean, ADC_min, SUV_max and SUV_mean values for intra-observer and inter-observer agreement. Mean ADC_mean and ADC_min in HNSCC were 1.05?±?0.34 × 10^?3?mm²/s and 0.65?±?0.29 × 10^?3?mm²/s, respectively. Mean SUV_mean and mean SUV_max were 7.61?±?3.87 and 12.8?±?5.0, respectively. Although statistically not significant, a trend towards higher SUV and lower ADC was observed with increasing tumour dedifferentiation. Pearson’s correlation analysis showed no significant correlation between ADC and SUV measurements (r ?0.103, ?0.051; p 0.552, 0.777).

Conclusion

Our data suggest that ADC and SUV values are reproducible and independent biomarkers in HNSCC.     

Diagnostic performance of 18F-fluorothymidine PET/CT for primary colorectal cancer and its lymph node metastasis: comparison with 18F-fluorodeoxyglucose PET/CT

Purpose

To examine the diagnostic performance of ¹⁸F-fluorothymidine (FLT) PET/CT in primary and metastatic lymph node colorectal cancer foci in comparison with ¹⁸F-fluorodeoxyglucose (FDG) PET/CT.

Methods

The study population comprised 28 patients with 30 newly diagnosed colorectal cancers who underwent surgical resection of the primary lesion and regional lymph nodes after both FLT and FDG PET/CT. The associations between SUVmax levels and pathological factors were evaluated using the Mann-Whitney U or Kruskal-Wallis test. Differences in diagnostic indexes for detecting nodal metastasis between the two tracers were estimated using the McNemar exact or χ ² test.

Results

All 30 primary cancers (43.0?±?20.0 mm, range 14 – 85 mm) were visualized by both tracers, but none of the FLT SUVmax values exceeded the FDG SUVmax values in any of the primary cancers (6.6?±?2.4 vs. 13.6?±?5.8, p?<?0.001). The sensitivity, specificity and accuracy for detecting nodal metastasis were 41 % (15/37), 98.8 % (493/499) and 94.8 % (508/536) for FDG PET/CT, and 32 % (12/37), 98.8 % (493/499) and 94.2 % (505/536) for FLT PET/CT, respectively. The sensitivity (p?=?0.45), specificity (p?=?0.68) and accuracy (p?=?0.58) were not different between the tracers. Nodal uptake of FLT and FDG was discordant in 7 (19 %) of 37 metastatic nodes. There were ten concordant true-positive nodes of which six showed higher FDG SUVmax and four showed higher FLT SUVmax, but the difference between FDG and FLT SUVmax was not significant (5.56?±?3.55 and 3.62?±?1.45, respectively; p?=?0.22).

Conclusion

FLT has the same potential as FDG in PET/CT for the diagnosis of primary and nodal foci of colorectal cancer despite significantly lower FLT uptake in primary foci.     

Dual-time-point [18F]-FDG PET/CT in the diagnostic evaluation of suspicious breast lesions

Purpose

The authors sought to evaluate whether the reacquisition of images 3 h after administration of radiotracer improves the sensitivity of fluorine-18 fluorodeoxyglucose positron emission tomography computed tomography ([¹⁸F]-FDG PET/CT) in patients with suspicious breast lesions.

Materials and methods

Forty-eight patients with 59 breast lesions underwent an [¹⁸F]-FDG PET/CT study in the prone position with a dual-time-point acquisition performed in the early phase 1 h after FDG administration (PET-1) and in the delayed phase 3 h after FDG administration (PET-2). Both examinations were evaluated qualitatively and semiquantitatively with calculation of the mean percentage variation of the standard uptake values (Δ% SUV_max) between PET-1 and PET-2. All lesions with an SUV_max ≥2.5 at PET-1 or a reduction in SUV between PET-1 and PET-2 were considered benign. The definitive histopathological diagnosis was available for all patients included in the study.

Results

The dual-time-point acquisition of [¹⁸F]-FDG PET/CT displayed an accuracy of 85% for lesions with an SUV_max ≥2.5 and/or positive Δ% SUV_max, with sensitivity and specificity values of 81% and 100% compared with 69%, 63% (both p<0.001) and 100% (p=n.s.), respectively, for the single-time-point acquisition. Malignant lesions showed an increase in FDG uptake between PET-1 and PET-2, with a Δ% SUV_max of 10±7 (p<0.04). In contrast, benign lesions showed a decrease in SUV between PET-1 and PET-2, with aΔ% SUV_max of ?21±7 (p<0.001).

Conclusions

The delayed repeat acquisition of PET images improves the accuracy of [¹⁸F]-FDG PET/CT in patients with suspicious breast lesions with respect to the single-time-point acquisition. In addition, malignant breast lesions displayed an increase in FDG uptake over time, whereas benign lesions showed a reduction. These variations in FDG uptake between PET-1 and PET-2 are a reliable parameter that can be used for differentiating between benign and malignant breast lesions.