Description: Indirect revascularization is the most widely used treatment to induce angiogenesis in pediatric moyamoya disease (MMD). Molecular imaging methods targeted for angiogenesis have recently been developed. We performed angiogenesis imaging in indirect revascularization surgery for MMD to evaluate angiogenic activity and its correlation with treatment efficacy. Methods: Twelve patients with pediatric MMD were prospectively enrolled. Encephaloduroarteriosynangiosis surgery was conducted, and 68 Ga-Arg-Gly-Asp (RGD) PET was performed 3.7 ± 1.0 mo after surgery. Basal perfusion and stress perfusion (P Str ) in the middle cerebral artery territory were evaluated by acetazolamide-stress brain perfusion SPECT using statistical probabilistic anatomic mapping, at preoperative, early postoperative, and long-term follow-up states. Angiogenic activity was assessed on the images in terms of maximal uptake ratio, volume of increased uptake, and uptake-volume product. Results: Basal perfusion and P Str were significantly improved after surgery. Increased angiogenic activity was observed in the revascularized area, mainly around the bony flap. Angiogenic activity gradually decreased with time and significantly correlated with the postoperative time interval ( P = 0.0015 for maximal uptake ratio and 0.0069 for volume of increased uptake). It was estimated to normalize at 6.3 mo after surgery. Uptake-volume product was inversely correlated with P Str improvement at the early postoperative state ( r = –0.5960, P = 0.0409) and also weakly correlated with P Str improvement at long-term follow-up ( r = –0.5010, P = 0.1165). Conclusion: Angiogenesis PET imaging with 68 Ga-RGD was successfully used for the assessment of angiogenic activity in indirect revascularization surgery for MMD, and angiogenic activation measured at approximately 3.7 mo after surgery was inversely correlated with perfusion improvement. The assessment of angiogenic activity using 68 Ga-RGD PET is expected to be effective for evaluating the mechanism or efficacy of revascularization treatment.

Description: Attenuation correction (AC) with an ultrashort echo time (UTE) sequence has recently been used in combination with segmentation for cortical bone identification for brain PET/MR studies. The purpose of this study was to evaluate the quantification of 18 F-fluoropropyl-carbomethoxyiodophenylnortropane ( 18 F-FP-CIT) binding in brain PET/MR, particularly focusing on effects of UTE-based AC including bone segmentation. Methods: Sixteen patients with initially suspected parkinsonism were prospectively enrolled. An emission scan was acquired 110 min after 18 F-FP-CIT injection on a dedicated PET/MR scanner, immediately followed by another emission scan using a PET/CT scanner 120 min after the injection. A UTE-based attenuation map was used to classify the voxels into 3 tissues: bone, soft tissue, and air. All PET images were spatially normalized, and a specific-to-nonspecific dopamine transporter (DAT) binding ratio (BR) was calculated using statistical probabilistic anatomic mapping. The level of agreement was assessed with intraclass correlation coefficients (ICCs). Voxelwise comparison between PET images acquired from PET/MR and PET/CT was performed. We compared non–attenuation-corrected images to analyze UTE-based AC effects on DAT quantification. Results: BR in the putamen obtained from PET/MR and PET/CT showed low interequipment variability, whereas BR in the caudate nucleus showed significant variability (ICC = 0.967 and 0.682 for putamen and caudate nucleus, respectively). BR in the caudate nucleus was significantly underestimated by PET/MR, compared with PET/CT (mean difference of BR = 0.66, P 〈 0.0001). Voxelwise analysis revealed that PET/MR showed significantly low BR in the periventricular regions, which was caused by a misclassification of the ventricle as air on the attenuation map. We also compared non-AC images, revealing low interequipment variability even in the caudate nucleus (ICC = 0.937 and 0.832 for putamen and caudate nucleus, respectively). Conclusion: Our data demonstrate spatial bias of the DAT BR on 18 F-FP-CIT PET/MR. Voxelwise analysis and comparison to non-AC images identified the misclassification of ventricle as air to be the cause of bias. To obtain reliable quantification for brain PET/MR studies including 18 F-FP-CIT PET, alternative and more reliable segmentation strategies are required.

Description: PET is a potentially useful modality for response analysis and prognosis prediction in patients with high-grade non-Hodgkin lymphoma (NHL). The thymidine analog 3'-deoxy-3'- 18 F-fluorothymidine ( 18 F-FLT) was recently introduced as a new tracer. 18 F-FLT uptake correlates with tumor cell proliferation and is suggested to reflect early response to treatment. We performed a prospective study to evaluate the prognostic value of early interim 18 F-FLT PET in patients with NHL. Methods: Patients with untreated NHL were enrolled between 2005 and 2007. Among them, 61 pairs of 18 F-FLT PET images were obtained at baseline (pre), after 1 cycle of chemotherapy (interim), and at the end of all scheduled first-line chemotherapy (final). All 18 F-FLT PET scans were interpreted by quantitative methods (maximum standardized uptake value [SUVmax] and mean standardized uptake value [SUVmean]). Receiver-operating-characteristic curve analysis was performed to define 18 F-FLT PET positivity using a cutoff value predicting disease progression, relapse, or death. Survival outcome was measured by progression-free survival (PFS) and overall survival (OS) rates. Results: Receiver-operating-characteristic curve analysis of SUVmax for prediction of disease progression and death showed the highest area under the curve (AUC) in interim 18 F-FLT PET scans (AUC of 0.841 for PFS and 0.834 for OS, with a cutoff of 1.86; P 〈 0.001), compared with pre and final 18 F-FLT PET scans. The SUVmean in interim 18 F-FLT PET scans also showed better prediction (AUC of 0.842 for PFS and 0.824 for OS, with a cutoff value of 1.65; P 〈 0.001) than pre and final 18 F-FLT PET scans. Patients with an interim 18 F-FLT PET SUVmax more than 1.86, who were defined as the interim PET-positive group, were associated with worse 5-y PFS and OS rates than the interim PET-negative group (for PFS: 52.0% vs. 80.7%, respectively, and P 〈 0.001; for OS: 56.2% vs. 81.4%, respectively, and P 〈 0.001). By multivariable analysis, the prognostic value of interim 18 F-FLT PET positivity by SUVmax remained significant after adjustment with other prognostic factors (for PFS: hazard ratio, 7.82, 95% confidence interval, 1.65–36.96, and P = 0.009; for OS: hazard ratio, 5.55, 95% confidence interval, 1.47–33.77, and P = 0.014). Conclusion: In patients with aggressive NHL, early interim 18 F-FLT PET is a significant predictor of PFS and OS. Early 18 F-FLT PET imaging also has a potential to identify patients with delayed response and nonfavorable prognosis despite achieving a clinical complete response.

Description: 18 F-FDG PET is an effective method of predicting recurrence of hepatocellular carcinoma (HCC) after liver transplantation. We compared recently introduced metabolic and volumetric 18 F-FDG PET/CT indices with the current clinicopathologic predictors for ability to predict recurrence. Methods: In total, 110 HCC patients who underwent 18 F-FDG PET and liver transplantation were enrolled. On PET, SUVs and tumor-to-background ratios (TBRs) were measured as metabolic activity indices. Various metabolic tumor volumes and uptake-volume products (UVP) were also measured as volumetric indices. The ability of these indices and other clinicopathologic factors to predict recurrence was compared. Results: All metabolic and volumetric indices were significant for recurrence prediction on receiver-operating-characteristic curve analyses ( P 〈 0.001). On univariate survival analyses, all PET indices—as well as tumor size, tumor number, the Milan criteria, tumor grade, vascular invasion, and T-stage—were significant factors. However, on multivariate analyses, tumor size, tumor grade, maximum TBR, and UVP calculated by inferior vena cava activity were significant factors ( P = 0.004, 0.014, 0.009, and 0.021, respectively). When the Milan criteria and PET factors were included in the multivariate analysis, the Milan criteria ( P = 0.029), maximum TBR ( P 〈 0.001), and UVP ( P = 0.016) were significant. Conclusion: Volumetric and metabolic activity indices of 18 F-FDG PET are effective predictors of posttransplantation HCC recurrence. In addition to clinicopathologic factors, these indices need to be considered in the selection of candidates for liver transplantation.