Generating synthetic high-resolution spinal STIR and T1w images from T2w FSE and low-resolution axial Dixon.

OBJECTIVES: To generate sagittal T1-weighted fast spin echo (T1w FSE) and short tau inversion recovery (STIR) images from sagittal T2-weighted (T2w) FSE and axial T1w gradient echo Dixon technique (T1w-Dixon) sequences. MATERIALS AND METHODS: This retrospective study used three existing datasets: "Study of Health in Pomerania" (SHIP, 3142 subjects, 1.5 Tesla), "German National Cohort" (NAKO, 2000 subjects, 3 Tesla), and an internal dataset (157 patients 1.5/3 Tesla). We generated synthetic sagittal T1w FSE and STIR images from sagittal T2w FSE and low-resolution axial T1w-Dixon sequences based on two successively applied 3D Pix2Pix deep learning models. "Peak signal-to-noise ratio" (PSNR) and "structural similarity index metric" (SSIM) were used to evaluate the generated image quality on an ablations test. A Turing test, where seven radiologists rated 240 images as either natively acquired or generated, was evaluated using misclassification rate and Fleiss kappa interrater agreement. RESULTS: Including axial T1w-Dixon or T1w FSE images resulted in higher image quality in generated T1w FSE (PSNR = 26.942, SSIM = 0.965) and STIR (PSNR = 28.86, SSIM = 0.948) images compared to using only single T2w images as input (PSNR = 23.076/24.677 SSIM = 0.952/0.928). Radiologists had difficulty identifying generated images (misclassification rate: 0.39 ± 0.09 for T1w FSE, 0.42 ± 0.18 for STIR) and showed low interrater agreement on suspicious images (Fleiss kappa: 0.09 for T1w/STIR). CONCLUSIONS: Axial T1w-Dixon and sagittal T2w FSE images contain sufficient information to generate sagittal T1w FSE and STIR images. CLINICAL RELEVANCE STATEMENT: T1w fast spin echo and short tau inversion recovery can be retroactively added to existing datasets, saving MRI time and enabling retrospective analysis, such as evaluating bone marrow pathologies. KEY POINTS: Sagittal T2-weighted images alone were insufficient for differentiating fat and water and to generate T1-weighted images. Axial T1w Dixon technique, together with a T2-weighted sequence, produced realistic sagittal T1-weighted images. Our approach can be used to retrospectively generate STIR and T1-weighted fast spin echo sequences.

Prevalence and distribution of calcified nodules in carotid arteries in correlation with clinical symptoms.

PURPOSE: Calcified nodules ("CN") are responsible for up to 5% of coronary-infarcts and, therefore, classified as minor criteria of "vulnerable" atherosclerotic plaque. We sought to evaluate prevalence and distribution of CN in carotid arteries in correlation with clinical symptoms. METHODS: 178 consecutive patients with unilateral ischemic stroke and carotid plaques ≥2 mm by duplex ultrasound underwent a carotid-black-blood-3T-MRI with fat-saturated pre- and post-contrast T1w-, PDw-, T2w- and TOF images using dedicated surface-coils. CN were defined as distinct calcification with an irregular, protruding, and convex luminal surface. Prevalence of CN was determined in common carotid artery ("CCA") and internal carotid artery ("ICA") in consensus by two reviewers blinded to clinical information. RESULTS: Thirty seven CN in 28 arteries of 26 patients were identified. Prevalence of CN in CCA compared to ICA was slightly higher (59 vs. 41%), but nearly similar in 66 arteries with ≥30% compared to 290 arteries with <30% stenosis (9.1 vs. 7.6%) and in the artery ipsilateral versus contralateral to stroke (7.9 vs. 7.9%; P values n.s.). Prevalence of CN was significantly higher in 40 symptomatic arteries with ≥30% stenosis compared to asymptomatic 26 arteries (15.6 vs. 0%; P = 0.04). There was a significantly higher prevalence of hypercholesterolemia and hypertension in patients with CN (57.7 vs. 36.0 and 88.5 vs. 66.7%; P values <0.05). CONCLUSION: CN were found in 7.9% of arteries with carotid-plaques ≥2 mm by duplex-ultrasound; prevalence was significantly higher in symptomatic arteries with ≥30% stenosis compared to asymptomatic with <30% stenosis, suggesting that CN play a role in pathogenesis of ischemic stroke in a small subset of patients.

Bi-Centric Independent Validation of Outcome Prediction after Radioembolization of Primary and Secondary Liver Cancer.

BACKGROUND: Yttrium-90 radioembolization (RE) plays an important role in the treatment of liver malignancies. Optimal patient selection is crucial for an effective and safe treatment. In this study, we aim to validate the prognostic performance of a previously established random survival forest (RSF) with an external validation cohort from a different national center. Furthermore, we compare outcome prediction models with different established metrics. METHODS: A previously established RSF model, trained on a consecutive cohort of 366 patients who had received RE due to primary or secondary liver tumor at a national center (center 1), was used to predict the outcome of an independent consecutive cohort of 202 patients from a different national center (center 2) and vice versa. Prognostic performance was evaluated using the concordance index (C-index) and the integrated Brier score (IBS). The prognostic importance of designated baseline parameters was measured with the minimal depth concept, and the influence on the predicted outcome was analyzed with accumulated local effects plots. RSF values were compared to conventional cox proportional hazards models in terms of C-index and IBS. RESULTS: The established RSF model achieved a C-index of 0.67 for center 2, comparable to the results obtained for center 1, which it was trained on (0.66). The RSF model trained on center 2 achieved a C-index of 0.68 on center 2 data and 0.66 on center 1 data. CPH models showed comparable results on both cohorts, with C-index ranging from 0.68 to 0.72. IBS validation showed more differentiated results depending on which cohort was trained on and which cohort was predicted (range: 0.08 to 0.20). Baseline cholinesterase was the most important variable for survival prediction. CONCLUSION: The previously developed predictive RSF model was successfully validated with an independent external cohort. C-index and IBS are suitable metrics to compare outcome prediction models, with IBS showing more differentiated results. The findings corroborate that survival after RE is critically determined by functional hepatic reserve and thus baseline liver function should play a key role in patient selection.

Reduced Periprocedural Analgesia After Replacement of Water for Injection with Glucose 5% Solution as the Infusion Medium for 90Y-Resin Microspheres.

The primary aim of our study was to compare the need for periinterventional on-demand analgesia when water for injection (WFI) was replaced with glucose 5% (G5) for 90Y-resin microsphere administration. METHODS: Forty-one patients who received 77 radioembolization procedures with G5 (2014-2015) were retrospectively matched with 41 patients (77 radioembolization procedures) who received radioembolization with WFI (2011-2014) at our center. The need for on-demand pain medication was chosen as an objective and accessible measure of periprocedural pain experienced by patients. RESULTS: Patients were well matched according to sex, age, tumor type and involvement, and prior antiangiogenic therapies. Periinterventional analgesic requirements were significantly lower for radioembolization procedures performed with G5 than WFI: 5 of 77 (6.5%) versus 29 of 77 (37.7%), P ≤ 0,001, respectively. Early stasis (defined as slowed antegrade flow, before total vascular stasis) occurred in 12 of 154 (7.8%) radioembolization procedures overall and was not different (P ≤ 0.229) between the 2 groups (4/77 [5.2%] vs. 8/77 [10.4%]). CONCLUSION: Slow pulsatile administration of 90Y-resin microspheres with WFI is associated with a low rate of stasis. Replacement of WFI with G5 significantly reduces the need for periprocedural analgesia. These data favor the use G5 for 90Y-resin microsphere implantation in daily practice.