A dosimetric treatment planning criterion for Child A patients without complete obstruction of the portal vein was developed.

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Purpose: Many centers aim to plan liver transarterial radioembolization (TARE) with dosimetry, even without CT-based attenuation correction (AC), or with unoptimized scatter correction (SC) methods. This work investigates the impact of presence vs absence of such corrections, and limited spatial resolution, on 3D dosimetry for TARE. Methods: Three voxelized phantoms were derived from CT images of real patients with different body sizes. Simulations of 99m Tc-SPECT projections were performed with the SIMIND code, assuming three activity distributions in the liver: uniform, inside a "liver's segment," or distributing multiple uptaking nodules ("nonuniform liver"), with a tumoral liver/healthy parenchyma ratio of 5:1. Projection data were reconstructed by a commercial workstation, with OSEM protocol not specifically optimized for dosimetry (spatial resolution of 12.6 mm), with/without SC (optimized, or with parameters predefined by the manufacturer; dual energy window), and with/without AC. Activity in voxels was calculated by a relative calibration, assuming identical microspheres and 99m Tc-SPECT counts spatial distribution. 3D dose distributions were calculated by convolution with lesions and healthy parenchyma from different reconstructions were compared with those obtained from the reference biodistribution (the "gold standard," GS), assessing differences for D95%, D70%, and D50% (i.e., minimum value of the absorbed dose to a percentage of the irradiated volume). γ tool analysis with tolerance of 3%/13 mm was used to evaluate the agreement between GS and simulated cases. The influence of deep-breathing was studied, blurring the reference biodistributions with a 3D anisotropic gaussian kernel, and performing the simulations once again. Results: Differences of the dosimetric indicators were noticeable in some cases, always negative for lesions and distributed around zero for parenchyma. Application of AC and SC reduced systematically the differences for lesions by 5%-14% for a liver segment, and by 7%-12% for a nonuniform liver. For parenchyma, the data trend was less clear, but the overall range of variability passed from −10%/40% for a liver segment, and −10%/20% for a nonuniform liver, to −13%/6% in both cases. Applying AC, SC with preset parameters gave similar results to optimized SC, as confirmed by γ tool analysis. Moreover, γ analysis confirmed that solely AC and SC are not sufficient to obtain accurate 3D dose distribution. With breathing, the accuracy worsened severely for all dosimetric indicators, above all for lesions: with AC and optimized SC, −38%/−13% in liver's segment, −61%/−40% in the nonuniform liver. For parenchyma, D50% resulted always less sensitive to breathing and sub-optimal correction methods (difference overall range: −7%/13%). Conclusions: Reconstruction protocol optimization, AC, SC, PVE and respiratory motion corrections should be implemented to obtain the best possible dosimetric accuracy. On the other side, thanks to the relative calibration, D50% inaccuracy for the healthy paren...

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Purpose To evaluate the prognostic role of pretreatment 18F-FDG PET/CT metabolic parameters in non-endemic Epstein-Barr Virus (EBV DNA)-related nasopharyngeal cancer (NPC) patients treated with curative intensity-modulated radiation therapy (IMRT) with or without chemotherapy (CHT). Materials/methods We retrospectively reviewed clinical data of 160 consecutive non-metastatic NPC patients who received IMRT with or without CHT. Forty-nine out of 160 patients that underwent whole body 18F-FDG PET/CT at our institution for disease staging with a minimum follow-up to 12 months were included in this study. We evaluated the relationship between maximum and mean standardized uptake values (SUVmax and SUVmean, respectively), metabolic tumor volume and total lesion glycolysis (TLG) of primary tumor and cervical lymph nodes with disease-free survival (DFS) and overall survival (OS). We also investigated the prognostic role of clinical variables such as age, disease stage, plasma EBV DNA load (copies/ml), gross tumor volume of primary tumor and lymph nodes. Results Median follow-up was 55 months. Two-and 5-year OS were 95.8% and 90.5%, respectively, while DFS was 83.4% at both time points. SUVmax of primary tumor ≥ 18.8 g/ml and primary tumor TLG ≥ 203.1 g were significant prognostic factors of worse OS. Furthermore, stages IVB and EBV DNA load ≥ 3493 copies/ml were significantly associated with lower DFS. No correlation was found between PET parameters and plasma EBV DNA load. Conclusion Even in a limited series, our data suggested that SUVmax, SUVmean and TLG of primary tumor could predict a poor outcome in NPC patients also in non-endemic area hypothesizing their use for refinement of prognostication.