Quantification accuracy of neuro-oncology PET data as a function of emission scan duration in PET/MR compared to PET/CT

ObjectivesTo evaluate and compare the effect of reduced acquisition time, as a surrogate of injected activity, on the PET quantification accuracy in PET/CT and PET/MR imaging.MethodsTwenty min ¹⁸F-FDG phantom measurements and 10 min ¹⁸F-FET brain scans were acquired in a Biograph-True-Point-True-View PET/CT (n = 8) and a Biograph mMR PET/MR (n = 16). Listmode data were repeatedly split into frames of 1 min to 10 min length and reconstructed using two different reconstruction settings of a 3D-OSEM algorithm: with post-filtering (“OSEM”), and without post-filtering but with resolution recovery (“PSF”). Recovery coefficients (RC_max, RC_A50) and standard uptake values (SUV_max, SUV_A50) were evaluated.ResultsRC_max (phantom) and SUV_max (patients) increased significantly when reducing the frame duration. Significantly lower deviations were observed for RC_A50 and SUV_A50, respectively, making them more appropriate to compare PET studies at different number of counts. No statistical significant differences were observed when using post-filtering and reducing the frame time to 4 min (RC_A50, reference 20 min, phantom) and to 3 min (SUV_A50, reference 10 min, patients).ConclusionsFor hybrid aminoacid brain imaging, frame duration (or injected activity) can potentially be reduced to 30% of the standard used in clinical routine without significant changes on the quantification accuracy of the PET images if adequate reconstruction settings and quantitative measures are used. Frame times below 4 min in the NEMA phantom are not advisable to obtain quantitative and reproducible measures.     

Clinically unrecognized pulmonary aspiration during gastrointestinal endoscopy with sedation: a potential pitfall interfering the performance of 18F-FDG PET for cancer screening

PurposeWe found several cases with unexpected pulmonary abnormalities on the ¹⁸F-FDG PET scan after the gastrointestinal endoscopy with sedation during a compact health check-up course, interfering the interpretations of ¹⁸F-FDG PET scan for cancer screening. The current studies aimed to analyze the incidence and the clinical relevance of this pulmonary finding.Materials and methodsFrom June to December 2009, 127 subjects undergoing the sequential gastrointestinal endoscopy with sedation and ¹⁸F-FDG PET scan within 48 h as part of routine health check-up were retrospectively enrolled in this study. The incidence of abnormal pulmonary findings and their SUV_max of FDG were calculated and correlated with the clinical manifestations.ResultsFive subjects had abnormal ¹⁸F-FDG PET findings but pulmonary symptoms were only found in 2. The SUV_max did not seem to reflect the severity of pulmonary symptoms or the need of intervention. Although the incidence of unrecognized pulmonary aspiration featuring inflammation detected by the ¹⁸F-FDG PET scan was high (3.94%, 5/127), the incidence of events needed intervention remained low (0.79%, 1/127), similar to those previously reported literatures.ConclusionsAlthough higher incidence of pulmonary aspiration in this study, it probably reflects the better sensitivity of ¹⁸F-FDG PET for inflammation. The low incidence of clinical events needed intervention may still reflect the safety of sedation used for gastrointestinal endoscopy. Proper arrangement of the sequential examinations if subjects need both gastrointestinal endoscopy with sedation and ¹⁸F-FDG PET is important to reduce the interference degrading the performance of ¹⁸F-FDG PET in cancer screening, diagnosis or staging.     

Clinical evaluation of whole-body oncologic PET with time-of-flight and point-spread function for the hybrid PET/MR system

PurposeHybrid positron emission tomography/magnetic resonance (PET/MR) imaging is a new multimodality imaging technology that can provide structural and functional information simultaneously. The aim of this study was to investigate the effects of the time-of-flight (TOF) and point-spread function (PSF) on small lesions observed in PET/MR images from clinical patient image sets.Materials and methodsThis study evaluated 54 small lesions in 14 patients who had undergone ¹⁸F-fluorodeoxyglucose (FDG) PET/MR. Lesions up to 30 mm in diameter were included. The PET data were reconstructed with a baseline ordered-subsets expectation-maximization (OSEM) algorithm, OSEM + PSF, OSEM + TOF and OSEM + TOF + PSF. PET image quality and small lesions were visually evaluated and scored by a 3-point scale. A quantitative analysis was then performed using the mean and maximum standardized uptake value (SUV) of the small lesions (SUV_mean and SUV_max). The lesions were divided into two groups according to the long-axis diameter and the location respectively and evaluated with each reconstruction algorithm. We also evaluated the background signal by analyzing the SUV_liver.ResultsOSEM + TOF + PSF provided the highest value and OSEM + TOF or PSF showed a higher value than OSEM for the visual assessment and quantitative analysis. The combination of TOF and PSF increased the SUV_mean by 26.6% and the SUV_max by 30.0%. The SUV_liverwas not influenced by PSF or TOF. For the OSEM + TOF + PSF model, the change in SUV_mean and SUV_max for lesions <10 mm in diameter was 31.9% and 35.8%, and 24.5% and 27.6% for lesions 10–30 mm in diameter, respectively. The abdominal lesions obtained the higher SUV than those of chest on the images with TOF and/or PSF.ConclusionApplication of TOF and PSF significantly increased the SUV of small lesions in hybrid PET/MR images, potentially improving small lesion detectability.     

Shorter-time dual-phase FDG PET/CT in characterizing solid or ground-glass nodules based on surgical results

ObjectivesWe compared the accuracy of shorter-time dual-phase ¹⁸F-FDG PET/CT in evaluating 94 different lung nodules classified as solid or ground-glass nodules (GGNs).Materials and MethodsEarly and delayed maximum standardized uptake values (SUV_max) as well as the retention index (RI) of each nodule were determined in 75 solid nodules and 19 GGNs.ResultsIn solid nodules, early SUV_max, delayed SUV_max, and RI were higher in malignant than in benign lesions. In GGNs, these values were not significantly lower in the malignant than in the benign lesions.ConclusionIn the patient group with solid nodules, shorter-time dual-phase ¹⁸F-FDG PET/CT could significantly differentiate the malignant from the benign ones.     

Opportunistic body composition evaluation in patients with esophageal adenocarcinoma: association of survival with 18F-FDG PET/CT muscle metrics

Objective

¹⁸F-FDG PET is widely used to accurately stage numerous types of cancers. Although ¹⁸F-FDG PET/CT features of tumors aid in predicting patient prognosis, there is increasing interest in mining additional quantitative body composition data that could improve the prognostic power of ¹⁸F-FDG PET/CT, without additional examination costs or radiation exposure. The aim of this study was to determine the association between overall survival and body composition metrics derived from routine clinical ¹⁸F-FDG PET/CT examinations.

Methods

Patients who received baseline ¹⁸F-FDG PET/CT imaging during workup for newly diagnosed esophageal adenocarcinoma (EAC) were included. From these studies, psoas cross-sectional area (CSA), muscle attenuation (MA), SUV_mean, and SUV_max were obtained. Correlation with overall survival was assessed using a Cox Proportional Hazards model, controlling for age, body mass index, ¹⁸F-FDG dose, glucose level, diabetes status, in-hospital status, and tumor stage.

Results

Among the 59 patients studied, psoas MA and SUV_max were found to be significant predictors of survival (HR 0.94, 95% CI 0.88–0.99, p?=?0.04, and HR 0.37, 95% CI 0.14–0.97, p?=?0.04, respectively) and remained independent predictors. Psoas CSA and SUV_mean did not significantly influence survival outcomes.

Conclusions

Characterization of psoas muscles as a surrogate marker for sarcopenia on baseline ¹⁸F-FDG PET/CT imaging is relatively easily obtained and may offer additional prognostic value in patients with EAC.

     

Pretreatment quantitative 18F-FDG PET/CT parameters as a predictor of survival in adenoid cystic carcinoma of the salivary glands

PurposeThe aim of this study was to determine the unique prognostic value of quantitative ¹⁸F-FDG PET/CT parameters to assess progression-free survival (PFS), distant metastasis-free survival (DMFS), and overall survival (OS) in patients with salivary gland adenoid cystic carcinoma (ACC).MethodsWe performed a retrospective study including 23 patients (15 men, 8 women; median age, 58 years; range, 21–91 years) with salivary gland ACC between January 2009 and October 2017 who underwent ¹⁸F-FDG PET/CT scan prior to treatment. Maximum, mean, peak, tumor-to-mediastinal blood pool and tumor-to-liver standardized uptake values (SUV_max, SUV_mean, SUV_peak, SUV_ratio[med] and SUV_ratio[liver]), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were obtained from ¹⁸F-FDG PET/CT. The prognostic value of quantitative ¹⁸F-FDG PET/CT parameters and other clinicopathological variables were evaluated utilizing the Cox proportional regression analysis.ResultsThe 3-year and 5-year OS for all the patients were 90.9%, and 62.3%, respectively. Log rank test determined that the SUV_ratio[med], SUV_ratio[liver], MTV and TLG were predictive factors of DMFS, PFS, and OS (p < 0.05), furthermore, SUV_max, minor salivary gland tumors and DM at initial diagnosis (M1 stage) were predictor for PFS; M1 stage and overall stage 3–4 predicted DMFS (all p < 0.05). Cox regression analyses confirmed that the higher SUV_ratio[med], SUV_ratio[liver], MTV, and TLG values predicted DMFS, PFS and OS independently, whereas SUV_max was an independent predictor of only PFS (p < 0.05).ConclusionsThe pretreatment metabolic ¹⁸F-FDG PET/CT parameters may reflect tumor aggressiveness in patients with salivary gland ACC and may potentially be utilized as a prognostic biomarker.     

Assessment of treatment response after lung stereotactic body radiotherapy using diffusion weighted magnetic resonance imaging and positron emission tomography: A pilot study

Background and purposeThere is no early predictor of treatment response after lung stereotactic body radiotherapy (SBRT). We conducted this pilot study to evaluate whether serial diffusion weighted magnetic resonance imaging (DW-MRI) or positron emission tomography (PET) could predict response after SBRT.Material and methodsEarly stage non-small cell lung cancer patients who received SBRT were eligible. DW-MRI and PET were undertaken pretreatment and every 3 months after SBRT in the first year. Patients with <1 year of follow-up were excluded from the analysis. The apparent diffusion coefficient (ADC) value and maximum standardized uptake value (SUV_max) of tumors were measured and compared between groups with or without local recurrence (LR).ResultsFifteen patients were enrolled and the data of 14 patients were analyzed. The median ADC value was significantly lower in patients with LR (n = 3) than in those without LR (n = 11) at 3 and 6 months (1.11 vs. 1.54 and 0.98 vs. 1.69 [×10⁻³ mm²/s]; p = 0.039 and 0.012, respectively) while there was no significant difference pretreatment and at 9 and 12 months after treatment. No significant difference was observed in the SUV_max at any time point.ConclusionsDW-MRI could be an early predictor of treatment response after lung SBRT.     

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.     

Synthesis and evaluation of 2-amino-5-(4-[18F]fluorophenyl)pent-4-ynoic acid ([18F]FPhPA): A novel 18F-labeled amino acid for oncologic PET imaging

Introduction¹⁸ F-labeled amino acids are important PET radiotracers for molecular imaging of cancer. This study describes synthesis and radiopharmacological evaluation of 2-amino-5-(4-[¹⁸ F]fluorophenyl)pent-4-ynoic acid ([¹⁸ F]FPhPA) as a novel amino acid radiotracer for oncologic imaging.Methods¹⁸ F]FPhPA was prepared using Pd-mediated Sonogashira cross-coupling reaction between 4-[¹⁸ F]fluoroiodobenzene ([¹⁸ F]FIB) and propargylglycine. The radiopharmacological profile of [¹⁸ F]FPhPA was evaluated in comparison with O-(2-[¹⁸ F]fluoroethyl)-L-tyrosine ([¹⁸ F]FET) using the murine breast cancer cell line EMT6 involving cellular uptake studies, radiotracer uptake competitive inhibition experiments and small animal PET imaging.Results¹⁸ F]FPhPA was prepared in 42 ± 10% decay-corrected radiochemical yield with high radiochemical purity >95% after semi-preparative HPLC purification. Cellular uptake of L-[¹⁸ F]FPhPA reached a maximum of 58 ± 14 % radioactivity/mg protein at 90 min. Lower uptake was observed for racemic and D-[¹⁸ F]FPhPA.Radiotracer uptake inhibition studies by synthetic and naturally occurring amino acids suggested that Na⁺-dependent system ASC, especially ASCT2, and Na⁺-independent system L are important amino acid transporters for [¹⁸ F]FPhPA uptake into EMT6 cells. Small animal PET studies demonstrated similar high tumor uptake of [¹⁸ F]FPhPA in EMT6 tumor-bearing mice compared to [¹⁸ F]FET reaching a maximum standardized uptake value (SUV) of 1.35 after 60 min p.i.. Muscle uptake of [¹⁸ F]FPhPA was higher (SUV_30min = 0.65) compared to [¹⁸ F]FET (SUV_30min = 0.40), whereas [¹⁸ F]FPhPA showed a more rapid uptake and clearance from the brain compared to [¹⁸ F]FET.ConclusionL-[¹⁸ F]FPhPA is the first ¹⁸ F-labeled amino acid prepared through Pd-mediated cross-coupling reaction.Advances in Knowledge and Implications for patient CareL-[¹⁸ F]FPhPA displayed promising properties as a novel amino acid radiotracer for molecular imaging of system ASC and system L amino acid transporters in cancer.     

Role of 18F-FDG PET/CT in the prediction of gastric cancer recurrence after curative surgical resection

Purpose

The study evaluated the role of preoperative ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in the prediction of recurrent gastric cancer after curative surgical resection.

Methods

A total of 271 patients with gastric cancer who underwent ¹⁸F-FDG PET/CT and subsequent curative surgical resection were enrolled. All patients underwent follow-up for cancer recurrence with a mean duration of 24?±?12?months. ¹⁸F-FDG PET/CT images were visually assessed and, in patients with positive ¹⁸F-FDG cancer uptake, the maximum standardized uptake value (SUV_max) of cancer lesions was measured. ¹⁸F-FDG PET/CT findings were tested as prognostic factors for cancer recurrence and compared with conventional prognostic factors. Furthermore, ¹⁸F-FDG PET/CT findings were assessed as prognostic factors according to histopathological subtypes.

Results

Of 271 patients, 47 (17?%) had a recurrent event. Positive ¹⁸F-FDG cancer uptake was shown in 149 patients (55?%). Tumour size, depth of invasion, presence of lymph node metastasis, positive ¹⁸F-FDG uptake and SUV_max were significantly associated with tumour recurrence in univariate analysis, while only depth of invasion, positive ¹⁸F-FDG uptake and SUV_max had significance in multivariate analysis. The 24-month recurrence-free survival rate was significantly higher in patients with negative ¹⁸F-FDG uptake (95?%) than in those with positive ¹⁸F-FDG uptake (74?%; p?18F-FDG uptake was a significant prognostic factor in patients with tubular adenocarcinoma (p?=?0.003) or poorly differentiated adenocarcinoma (p?=?0.0001). However, only marginal significance was shown in patients with signet-ring cell carcinoma and mucinous carcinoma (p?=?0.05).

Conclusion

¹⁸F-FDG uptake of gastric cancer is an independent and significant prognostic factor for tumour recurrence. ¹⁸F-FDG PET/CT could provide effective information on the prognosis after surgical resection of gastric cancer, especially in tubular adenocarcinoma and poorly differentiated adenocarcinoma.     

Hepatic steatosis is associated with increased hepatic FDG uptake

ObjectiveThe use of liver as a reference tissue for semi-quantification of tumour FDG uptake may not be valid in hepatic steatosis (HS). Previous studies on the relation between liver FDG uptake and HS have been contradictory probably because they ignored blood glucose (BG). Because hepatocyte and blood FDG concentrations equalize, liver FDG uptake parallels BG, which must therefore be considered when studying hepatic FDG uptake. We therefore re-examined the relation between HS and liver uptake taking BG into account.MethodsThis was a retrospective study of 304 patients undergoing routine PET/CT with imaging 60 min post-FDG. Average standard uptake value (SUV_ave), maximum SUV (SUV_max) and CT density (index of HS) were measured in a liver ROI. Blood pool SUV was based on the left ventricular cavity (SUV_LV). Correlations were assessed using least squares fitting of continuous data. Patients were also divided into BG subgroups (<4, 4–5, 5–6, 6–8, 8–10 and 10+ mmol/l).ResultsSUV_ave, SUV_max and SUV_LV displayed similar relations with BG. SUV_max/SUV_LV, but not SUV_ave/SUV_LV, correlated significantly with BG. SUV_max, but not SUV_ave, correlated inversely with CT density before and after adjusting for BG. SUV_max/SUV_ave correlated more strongly with CT density than SUV_max. CT density correlated inversely with SUV_max/SUV_LV but positively with SUV_ave/SUV_LV.ConclusionsHepatic SUV is more influenced by BG than by HS. Its relation with BG renders it unsuitable as a reference tissue. Nevertheless, hepatic fat does correlate positively with liver SUV, although this is seen only with SUV_max because SUV_ave is ‘diluted’ by hepatic fat.     

Antilipolytic drug boosts glucose metabolism in prostate cancer

IntroductionThe antilipolytic drug Acipimox reduces free fatty acid (FFA) levels in the blood stream. We examined the effect of reduced FFAs on glucose metabolism in androgen-dependent (CWR22Rv1) and androgen-independent (PC3) prostate cancer (PCa) xenografts.MethodsSubcutaneous tumors were produced in nude mice by injection of PC3 and CWR22Rv1 PCa cells. The mice were divided into two groups (Acipimox vs. controls). Acipimox (50 mg/kg) was administered by oral gavage 1 h before injection of tracers. 1 h after i.v. co-injection of 8.2 MBq (222 ± 6.0 μCi) ¹⁸ F-FDG and ~ 0.0037 MBq (0.1 μCi) ¹⁴C-acetate, ¹⁸ F-FDG imaging was performed using a small-animal PET scanner. Counting rates in reconstructed images were converted to activity concentrations. Quantification was obtained by region-of-interest analysis using dedicated software. The mice were euthanized, and blood samples and organs were harvested. ¹⁸ F radioactivity was measured in a calibrated γ-counter using a dynamic counting window and decay correction. ¹⁴C radioactivity was determined by liquid scintillation counting using external standard quench corrections. Counts were converted into activity, and percentage of the injected dose per gram (%ID/g) tissue was calculated.ResultsFDG biodistribution data in mice with PC3 xenografts demonstrated doubled average %ID/g tumor tissue after administration of Acipimox compared to controls (7.21 ± 1.93 vs. 3.59 ± 1.35, P = 0.02). Tumor-to-organ ratios were generally higher in mice treated with Acipimox. This was supported by PET imaging data, both semi-quantitatively (mean tumor FDG uptake) and visually (tumor-to-background ratios). In mice with CWR22Rv1 xenografts there was no effect of Acipimox on FDG uptake, either in biodistribution or PET imaging. ¹⁴C-acetate uptake was unaffected in PC3 and CWR22Rv1 xenografts.ConclusionsIn mice with PC3 PCa xenografts, acute administration of Acipimox increases tumor uptake of ¹⁸ F-FDG with general improvements in tumor-to-background ratios. Data indicate that administration of Acipimox prior to ¹⁸ F-FDG PET scans has potential to improve sensitivity and specificity in patients with castration-resistant advanced PCa.     

Evaluation of intratumoural heterogeneity on 18F-FDG PET/CT for characterization of peripheral nerve sheath tumours in neurofibromatosis type 1

Purpose

The aim of the study was to evaluate the potential usefulness of intratumoural tracer uptake heterogeneity on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT as compared to a cut-off maximum standardized uptake value (SUV_max) for characterization of peripheral nerve sheath tumours (PNSTs) in neurofibromatosis type 1 (NF1).

Methods

Fifty patients suffering from NF1 were examined by ¹⁸F-FDG PET/CT. Intralesional tracer uptake was analysed qualitatively and semi-quantitatively by measuring the mean and maximum SUV. Uptake heterogeneity was graded qualitatively using a three-point scale and semi-quantitatively by calculating an SUV-based heterogeneity index (HI_SUV). Cohen’s κ was used to determine inter- and intra-rater agreement. Histopathological evaluation and clinical as well as radiological follow-up examinations served as the reference standards.

Results

A highly significant correlation between the degree of intratumoural uptake heterogeneity on ¹⁸F-FDG PET and malignant transformation of PNSTs was observed (p?<?0.0001). Semi-quantitative HI_SUV was significantly higher in malignant PNSTs (MPNSTs) than in benign tumours (p?=?0.0002). Both intralesional heterogeneity and SUV_max could be used to identify malignant tumours with a sensitivity of 100 %. Cohen’s κ was 0.86 for inter-rater agreement and 0.88 for intra-rater agreement on heterogeneity.

Conclusion

MPNSTs in patients with NF1 demonstrate considerable intratumoural uptake heterogeneity on ¹⁸F-FDG PET/CT. Assessment of tumour heterogeneity is highly reproducible. Both tumour heterogeneity and a cut-off SUV_max may be used to sensitively identify malignant PNSTs, but the specificity is higher for the latter. A combination of both methods leads to a non-significant improvement in diagnostic performance.     

Influence of PET reconstruction technique and matrix size on qualitative and quantitative assessment of lung lesions on [18F]-FDG-PET: A prospective study in 37 cancer patients

PurposeTo evaluate the influence of point spread function (PSF)-based reconstruction and matrix size for PET on (1) lung lesion detection and (2) standardized uptake values (SUV).MethodsThis prospective study included oncological patients who underwent [18F]-FDG-PET/CT for staging. PET data were reconstructed with a 2D ordered subset expectation maximization (OSEM) algorithm, and a 2D PSF-based algorithm (TrueX), separately with two matrix sizes (168 × 168 and 336 × 336). The four PET reconstructions (TrueX-168; OSEM-168; TrueX-336; and OSEM-336) were read independently by two raters, and PET-positive lung lesions were recorded. Blinded to the PET findings, a third independent rater assessed lung lesions with diameters of >4 mm on CT. Subsequently, PET and CT were reviewed side-by side in consensus. Multi-factorial logistic regression analyses and two-way repeated measures analyses of variance (ANOVA) were performed.ResultsThirty-seven patients with 206 lung lesions were included. Lesion-based PET sensitivities differed significantly between reconstruction algorithms (P < 0.001) and between reconstruction matrices (P = 0.022). Sensitivities were 94.2% and 88.3% for TrueX-336; 88.3% and 85.9% for TrueX-168; 67.8% and 66.3% for OSEM-336; and 67.0% and 67.9% for OSEM-168; for rater 1 and rater 2, respectively. SUV_max and SUV_mean were significantly higher for images reconstructed with 336 × 336 matrices than for those reconstructed with 168 × 168 matrices (P < 0.001).ConclusionOur results demonstrate that PSF-based PET reconstruction, and, to a lesser degree, higher matrix size, improve detection of metabolically active lung lesions. However, PSF-based PET reconstructions and larger matrix sizes lead to higher SUVs, which may be a concern when PET data from different institutions are compared.     

A pilot study on lung cancer detection based on regional metabolic activity distribution in digital low-dose 18F-FDG PET

ObjectivesTo investigate the potential of automatic lung cancer detection on submillisievert dose ¹⁸F-fludeoxyglucose (¹⁸F-FDG) scans using different positron emission tomography (PET) parameters, as a primary step towards a potential new indication for ¹⁸F-FDG PET in lung cancer screening.MethodsWe performed a retrospective cohort analysis with 83 patients referred for ¹⁸F-FDG PET/CT, including of 34 patients with histology-proven lung cancer and 49 patients without lung disease. Aside clinical standard PET images (PET_100%) two additional low-dose PET reconstructions were generated, using only 15 s and 5 s of the 150 s list mode raw data of the full-dose PET, corresponding to 10% and 3.3% of the original ¹⁸F-FDG activity. The lungs were subdivided into three segments on each side, and each segment was classified as normal or containing cancer. The following standardized uptake values (SUVs) were extracted from PET per lung segment: SUV_mean, SUV_hot5, SUV_median, SUV_std and SUV_total. A multivariate linear regression model was used and cross-validated. The accuracy for lung cancer detection was tested with receiver operating characteristics analysis and T-statistics was used to calculate the weight of each parameter.ResultsThe T-statistics showed that SUV_std was the most important discriminative factor for lung cancer detection. The multivariate model achieved an area under the curve of 0.97 for full-dose PET, 0.85 for PET_10% with PET_3.3% reconstructions resulting in a still high sensitivity the PET_10% reconstruction of 80%.ConclusionThis pilot study indicates that segment-based, quantitative PET parameters of low-dose PET reconstructions could be used to automatically detect lung cancer with high sensitivity.Advances in knowledgeAutomated assessment of PET parameters in low-dose PET may aid for an early detection of lung cancer.     

Reproducibility of functional volume and activity concentration in 18F-FDG PET/CT of liver metastases in colorectal cancer

Purpose

Several studies showed potential for monitoring response to systemic therapy in metastatic colorectal cancer patients with ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET). Before ¹⁸F-FDG PET can be implemented for response evaluation the repeatability should be known. This study was performed to assess the magnitude of the changes in standardized uptake value (SUV), volume and total lesion glycolysis (TLG) in colorectal liver metastases and validate the biological basis of ¹⁸F-FDG PET in colorectal liver metastases.

Methods

Twenty patients scheduled for liver metastasectomy underwent two ¹⁸F-FDG PET scans within 1?week. Bland-Altman analysis was performed to assess repeatability of SUV_max, SUV_mean, volume and TLG. Tumours were delineated using an adaptive threshold method (PET_SBR) and a semiautomatic fuzzy locally adaptive Bayesian (FLAB) delineation method.

Results

Coefficient of repeatability of SUV_max and SUV_mean were ～39 and ～31?%, respectively, independent of the delineation method used and image reconstruction parameters. However, repeatability was worse in recently treated patients. The FLAB delineation method improved the repeatability of the volume and TLG measurements compared to PET_SBR, from coefficients of repeatability of over 85?% to 45?% and 57?% for volume and TLG, respectively. Glucose transporter 1 (GLUT1) expression correlated to the SUV_mean. Vascularity (CD34 expression) and tumour hypoxia (carbonic anhydrase IX expression) did not correlate with ¹⁸F-FDG PET parameters.

Conclusion

In conclusion, repeatability of SUV_mean and SUV_max was mainly affected by preceding systemic therapy. The repeatability of tumour volume and TLG could be improved using more advanced and robust delineation approaches such as FLAB, which is recommended when ¹⁸F-FDG PET is utilized for volume or TLG measurements. Improvement of repeatability of PET measurements, for instance by dynamic PET scanning protocols, is probably necessary to effectively use PET for early response monitoring.     

Comparison of L-type amino acid transporter 1 expression and L-[3-18F]-α-methyl tyrosine uptake in outcome of non-small cell lung cancer

Objectivel-Type amino acid transporter 1 (LAT1) has associated with tumor growth and poor outcome of patients with non-small cell lung cancer (NSCLC). l-[3-¹⁸F]-α-methyl tyrosine (¹⁸F-FAMT) is an amino acid tracer for positron emission tomography (PET) imaging, and ¹⁸F-FAMT uptake is mediated by LAT1. The purpose of this study is to compare the prognostic significance of ¹⁸F-FAMT uptake in the primary tumors with that of LAT1 expression in patients with NSCLC.MethodsFifty-nine patients with NSCLC were enrolled in this study. All patients underwent ¹⁸F-FAMT PET prior to resection of the tumor, and immunohistochemical staining of the resected tumors were performed to compare the ¹⁸F-FAMT uptake and LAT1 expression. Uptake of ¹⁸F-FAMT was evaluated using semiquantitative standardized uptake value (SUV_max), and the cutoff value was determined to discriminate patients with high SUV_max from those with low SUV_max. Expression of LAT1 was evaluated by the score of staining intensity through 1 to 4. SUV_max and LAT1 expression were compared according to the clinicopathological variables.ResultsThe best discriminative cutoff value of ¹⁸F-FAMT SUV_max within the primary tumors was 1.6. The high SUV_max (>1.6) in ¹⁸F-FAMT PET was significantly associated with male, and positive LAT1 expression was significantly associated with male and nonadenocarcinoma. In the univariate analysis, high SUV_max (>1.6) in ¹⁸F-FAMT PET and positive LAT1 expression were significant predictor of the poor outcome. Multivariate analysis confirmed that positive LAT1 expression was an independent and significant factor for predicting poor prognosis in NSCLC (P=.035).ConclusionLAT1 expression is a stronger prognostic factor than ¹⁸F-FAMT uptake in surgically resected NSCLC.     

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.

     

18F-FDG PET/CT and contrast-enhanced CT findings of pulmonary cryptococcosis

PurposePulmonary cryptococcosis is an uncommon cause of pulmonary nodules in non-AIDS patients. This study reports the ¹⁸F-fluorodeoxyglucose-positron emission tomography (¹⁸F-FDG PET/CT) and contrast-enhanced CT (CE-CT) findings of 42 patients with pulmonary cryptococcosis.Materials and methodsA retrospective review of the ¹⁸F-FDG PET/CT and CE-CT findings of 42 patients with histologically proven pulmonary cryptococcosis was conducted. All patients underwent PET/CT and CE-CT in the same session. The CT diagnosis was based on the location, morphological features, and enhancement of lesions. The PET/CT findings were recorded, and clinical data and surgical and histopathological findings were collected.ResultsThe results of the PET scans revealed that 37 (88%) of 42 patients showed higher FDG uptake, and 5 (12%) patients demonstrated lower FDG uptake than the mediastinal blood pool. The maximum standardized uptake value (SUV) of pulmonary cryptococcosis ranged from 1.4 to 13.0 (average: 5.7 ± 3.3, median 4.9). A single nodular pattern was the most prevalent pattern observed and was found in 29 (69%) patients. This pattern was followed by scattered nodular (n = 4, 10%), clustered nodular (n = 3, 7%), mass-like (n = 3, 7%), and bronchopneumonic (n = 3, 7%) patterns. The most frequent pattern of immunocompetent patients was the single nodular pattern (29 of 33, 88%). Immunocompromised patients most frequently pattern exhibited mass-like (3 of 9, 33%) and bronchopneumonic (3 of 9, 33%) patterns.ConclusionPulmonary cryptococcosis most commonly appears as single nodules in immunocompetent patients. Mass-like and bronchopneumonic patterns were common in immunocompromised patients. In 88% of patients, lung lesions showed high FDG uptake, thus mimicking a possible malignant condition.     

Evaluation of the antitumor effects of rilotumumab by PET imaging in a U-87 MG mouse xenograft model

IntroductionDysregulation of the hepatocyte growth factor (HGF)/MET pathway has been implicated in various cancers. Rilotumumab is an investigational, fully human monoclonal antibody that binds and neutralizes HGF. The purpose of this study was to evaluate the efficacy of rilotumumab in a U-87 MG mouse xenograft tumor model using ¹⁸ F-FDG and ¹⁸ F-FLT PET.MethodsU-87 MG tumor-bearing nude mice received rilotumumab or control IgG2. In the dose response study, increasing doses of rilotumumab (10, 30, 100, 300, or 500 μg) were administered, and mice were evaluated with ¹⁸ F-FDG PET at baseline and 7 days post-treatment. In the time course study, 300 μg of rilotumumab twice per week was used for the treatment, and mice were evaluated over 7 days using ¹⁸ F-FDG and ¹⁸ F-FLT PET.ResultsIn the dose response study, rilotumumab at doses of 300 and 500 μg was similarly effective against tumor growth. Treatment with 300 and 500 μg rilotumumab inhibited ¹⁸ F-FDG accumulation with significant decreases of ? 37% and ? 40% in the percent injected dose per gram of tissue (%ID/g), respectively. In the time course study, treatment with 300 μg rilotumumab inhibited ¹⁸ F-FDG and ¹⁸ F-FLT accumulation with a maximum %ID/g of ? 41% and ? 64%, respectively. No apparent differences between the use of either tracer to evaluate rilotumumab efficacy were observed.ConclusionsRilotumumab inhibited ¹⁸ F-FDG and ¹⁸ F-FLT accumulation as early as 2 and 4 days after treatment, respectively, in a mouse tumor model. Further studies to evaluate ¹⁸ F-FDG PET imaging as an early tumor response marker for rilotumumab are warranted. Rilotumumab is currently being tested in patients with MET-positive, advanced gastric and gastroesophageal cancer.