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Purpose To compare the diagnostic performance of 18F-fluorodeoxyglucose-PET/MRI and MRI in the diagnosis of pelvic recurrence of rectal cancer. Methods All PET/MRIs of patients in the follow-up of rectal cancer performed between 2011 and 2018 at our institution were retrospectively reviewed. Recurrence was confirmed/excluded either by histopathology or imaging follow-up (> 4 months). Four groups of readers (groups 1/2: one radiologist each, groups 3/4: one radiologist/one nuclear medicine physician) independently interpreted MRI and PET/MRI. The likelihood of recurrence was scored on a 5-point-scale. Inter-reader agreement, sensitivity, specificity, PPV/NPV and accuracy were assessed. ROC curve analyses were performed. Results Fourty-one PET/MRIs of 40 patients (mean 61 years ± 10.9; 11 women, 29 men) were included. Sensitivity of PET/MRI in detecting recurrence was 94%, specificity 88%, PPV/NPV 97% and 78%, accuracy 93%. Sensitivity of MRI was 88%, specificity 75%, PPV/NPV 94% and 60%, accuracy 85%. ROC curve analyses showed an AUC of 0.97 for PET/MRI and 0.92 for MRI, but the difference was not statistically significant (p = 0.116). On MRI more cases were scored as equivocal (12% versus 5%). Inter-reader agreement was substantial for PET/MRI and MRI (0.723 and 0.656, respectively). Conclusion 18F-FDG-PET/MRI and MRI are accurate in the diagnosis of locally recurrent rectal cancer. Sensitivity, specificity, PPV, NPV and accuracy are comparable for both modalities, but PET/MRI increases readers’ confidence levels and reduces the number of equivocal cases. Graphic abstract

Purpose Preoperative hypertrophy induction of future liver remnant (FLR) reduces the risk of postoperative liver insufficiency after partial hepatectomy. One of the most commonly used methods to induce hypertrophy of FLR is portal vein embolization (PVE). Recent studies have shown that transarterial radioembolization (TARE) also induces hypertrophy of the contralateral liver lobe. The aim of our study was to evaluate contralateral hypertrophy after TARE versus after PVE taking into account the effect of cirrhosis. Methods Forty-nine patients undergoing PVE before hemihepatectomy and 24 patients with TARE as palliative treatment for liver malignancy were retrospectively included. Semi-automated volumetry of the FLR/contralateral liver lobe before and after intervention (20 to 65 days) was performed on CT or MRI, and the relative increase in volume was calculated. Cirrhosis was evaluated independently by two radiologists on CT/MRI, and interrater reliability was calculated. Results Hypertrophy after PVE was significantly more pronounced than after TARE (25.3% vs. 7.4%; p p = 0.002), whereas in patients with cirrhosis, the difference was not statistically significant (18.2% vs. 7.4%; p = 0.212). After PVE, hypertrophy in patients without cirrhosis was more pronounced than in patients with cirrhosis (25.9% vs. 18.2%; p = 0.203), while after TARE, hypertrophy was comparable in patients with and without cirrhosis (7.4% vs. 8.6%; p = 0.928). Conclusion TARE induces less pronounced hypertrophy of the FLR compared to PVE. Cirrhosis seems to be less of a limiting factor for hypertrophy after TARE, compared to PVE. Graphic abstract

Objectives The aim of the study was to evaluate the effect of bolus-tracking ROI positioning on coronary computed tomography angiography (CCTA) image quality. Methods In this retrospective monocentric study, all patients had undergone CCTA by step-and-shoot mode to rule out coronary artery disease within a cohort at intermediate risk. Two groups were formed, depending on ROI positioning (left atrium (LA) or ascending aorta (AA)). Each group contained 96 patients. To select pairs of patients, propensity score matching was used. Image quality with regard to coronary arteries as well as pulmonary arteries was evaluated using quantitative and qualitative scores. Results In terms of the coronary arteries, there was no significant difference between both groups using quantitative (SNR AA 14.92 vs. 15.46; p = 0.619 | SNR LM 19.80 vs. 20.30; p = 0.661 | SNR RCA 24.34 vs. 24.30; p = 0.767) or qualitative scores (4.25 vs. 4.29; p = 0.672), respectively. With regard to pulmonary arteries, we found significantly higher quantitative (SNR RPA 8.70 vs. 5.89; p < 0.001 | SNR LPA 9.06 vs. 6.25; p < 0.001) and qualitative scores (3.97 vs. 2.24; p < 0.001) for ROI positioning in the LA than for ROI positioning in the AA. Conclusions ROI positioning in the LA or the AA results in comparable image quality of CT coronary arteriography, while positioning in the LA leads to significantly higher image quality of the pulmonary arteries. These results support ROI positioning in the LA, which also facilitates triple-rule-out CT scanning. Key Points • ROI positioning in the left atrium or the ascending aorta leads to comparable image quality of the coronary arteries. • ROI positioning in the left atrium results in significantly higher image quality of the pulmonary arteries. • ROI positioning in the left atrium is feasible to perform triple-rule-out CTA.