Prognostic value of single-subject grey matter networks in early multiple sclerosis.

The identification of prognostic markers in early multiple sclerosis (MS) is challenging and requires reliable measures that robustly predict future disease trajectories. Ideally, such measures should make inferences at the individual level to inform clinical decisions. This study investigated the prognostic value of longitudinal structural networks to predict 5-year Expanded Disability Status Scale (EDSS) progression in patients with relapsing-remitting MS (RRMS). We hypothesized that network measures, derived from MRI, outperform conventional MRI measurements at identifying patients at risk of developing disability progression. This longitudinal, multicentre study within the Magnetic Resonance Imaging in MS (MAGNIMS) network included 406 patients with RRMS (mean age = 35.7 ± 9.1 years) followed up for 5 years (mean follow-up = 5.0 ± 0.6 years). EDSS was determined to track disability accumulation. A group of 153 healthy subjects (mean age = 35.0 ± 10.1 years) with longitudinal MRI served as controls. All subjects underwent MRI at baseline and again 1 year after baseline. Grey matter atrophy over 1 year and white matter lesion load were determined. A single-subject brain network was reconstructed from T1-weighted scans based on grey matter atrophy measures derived from a statistical parameter mapping-based segmentation pipeline. Key topological measures, including network degree, global efficiency and transitivity, were calculated at single-subject level to quantify network properties related to EDSS progression. Areas under receiver operator characteristic (ROC) curves were constructed for grey matter atrophy and white matter lesion load, and the network measures and comparisons between ROC curves were conducted. The applied network analyses differentiated patients with RRMS who experience EDSS progression over 5 years through lower values for network degree [H(2) = 30.0, P < 0.001] and global efficiency [H(2) = 31.3, P < 0.001] from healthy controls but also from patients without progression. For transitivity, the comparisons showed no difference between the groups [H(2) = 1.5, P = 0.474]. Most notably, changes in network degree and global efficiency were detected independent of disease activity in the first year. The described network reorganization in patients experiencing EDSS progression was evident in the absence of grey matter atrophy. Network degree and global efficiency measurements demonstrated superiority of network measures in the ROC analyses over grey matter atrophy and white matter lesion load in predicting EDSS worsening (all P-values < 0.05). Our findings provide evidence that grey matter network reorganization over 1 year discloses relevant information about subsequent clinical worsening in RRMS. Early grey matter restructuring towards lower network efficiency predicts disability accumulation and outperforms conventional MRI predictors.

Ultrafast Brain MRI with Deep Learning Reconstruction for Suspected Acute Ischemic Stroke.

Background Deep learning (DL)-accelerated MRI can substantially reduce examination times. However, studies prospectively evaluating the diagnostic performance of DL-accelerated MRI reconstructions in acute suspected stroke are lacking. Purpose To investigate the interchangeability of DL-accelerated MRI with conventional MRI in patients with suspected acute ischemic stroke at 1.5 T. Materials and Methods In this prospective study, 211 participants with suspected acute stroke underwent clinically indicated MRI at 1.5 T between June 2022 and March 2023. For each participant, conventional MRI (including T1-weighted, T2-weighted, T2*-weighted, T2 fluid-attenuated inversion-recovery, and diffusion-weighted imaging; 14 minutes 18 seconds) and DL-accelerated MRI (same sequences; 3 minutes 4 seconds) were performed. The primary end point was the interchangeability between conventional and DL-accelerated MRI for acute ischemic infarction detection. Secondary end points were interchangeability regarding the affected vascular territory and clinically relevant secondary findings (eg, microbleeds, neoplasm). Three readers evaluated the overall occurrence of acute ischemic stroke, affected vascular territory, clinically relevant secondary findings, overall image quality, and diagnostic confidence. For acute ischemic lesions, size and signal intensities were assessed. The margin for interchangeability was chosen as 5%. For interrater agreement analysis and interrater reliability analysis, multirater Fleiss κ and the intraclass correlation coefficient, respectively, was determined. Results The study sample consisted of 211 participants (mean age, 65 years ± 16 [SD]); 123 male and 88 female). Acute ischemic stroke was confirmed in 79 participants. Interchangeability was demonstrated for all primary and secondary end points. No individual equivalence indexes (IEIs) exceeded the interchangeability margin of 5% (IEI, -0.002 [90% CI: -0.007, 0.004]). Almost perfect interrater agreement was observed (P > .91). DL-accelerated MRI provided higher overall image quality (P < .001) and diagnostic confidence (P < .001). The signal properties of acute ischemic infarctions were similar in both techniques and demonstrated good to excellent interrater reliability (intraclass correlation coefficient, ≥0.8). Conclusion Despite being four times faster, DL-accelerated brain MRI was interchangeable with conventional MRI for acute ischemic lesion detection. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Haller in this issue.

Concurrent inflammation-related brain reorganization in multiple sclerosis and depression.

BACKGROUND: Neuroinflammation affects brain tissue integrity in multiple sclerosis (MS) and may have a role in major depressive disorder (MDD). Whether advanced magnetic resonance imaging characteristics of the gray-to-white matter border serve as proxy of neuroinflammatory activity in MDD and MS remain unknown. METHODS: We included 684 participants (132 MDD patients with recurrent depressive episodes (RDE), 70 MDD patients with a single depressive episode (SDE), 222 MS patients without depressive symptoms (nMS), 58 MS patients with depressive symptoms (dMS), and 202 healthy controls (HC)). 3 T-T1w MRI-derived gray-to-white matter contrast (GWc) was used to reconstruct and characterize connectivity alterations of GWc-covariance networks by means of modularity, clustering coefficient, and degree. A cross-validated support vector machine was used to test the ability of GWc to stratify groups according to their depression symptoms, measured with BDI, at the single-subject level in MS and MDD independently. FINDINGS: MS and MDD patients showed increased modularity (ANOVA partial-η2 = 0.3) and clustering (partial-η2 = 0.1) compared to HC. In the subgroups, a linear trend analysis attested a gradient of modularity increases in the form: HC, dMS, nMS, SDE, and RDE (ANOVA partial-η2 = 0.28, p < 0.001) while this trend was less evident for clustering coefficient. Reduced morphological integrity (GWc) was seen in patients with increased depressive symptoms (partial-η2 = 0.42, P < 0.001) and was associated with depression scores across patient groups (r = -0.2, P < 0.001). Depressive symptoms in MS were robustly classified (88 %). CONCLUSIONS: Similar structural network alterations in MDD and MS exist, suggesting possible common inflammatory events like demyelination, neuroinflammation that are caught by GWc analyses. These alterations may vary depending on the severity of symptoms and in the case of MS may elucidate the occurrence of comorbid depression.

Gender differences in self-assessed performance and stress level during training of basic interventional radiology maneuvers.

OBJECTIVES: Gender differences have been reported to influence medical training. We investigated gender differences encountered during training in interventional radiology maneuvers. METHODS: Catheter handling was analyzed under standardized conditions in 64 participants naïve to endovascular procedures (26 women, 38 men). Objective (e.g., catheter pathway, catheter movements, required time) and subjective parameters (stress level) were recorded. The NASA-Task Load Index (NASA-TLX; 1-20 points) was used to assess participants' stress levels and perceived workload. RESULTS: In the easier tasks, no significant differences between male and female participants regarding catheter handling were observed. In the most complex task, female participants took themselves more time (688 ± 363 vs. 501 ± 230 s; p = 0.02), asked for help more frequently (n = 19 vs. n = 8) and earlier than men (203 ± 94 vs. 305 ± 142 s; p = 0.049), whereas men stood out by more agitated catheter handling (6.0 ± 1.8 vs. 4.8 ± 1.6 movements/s; p = 0.005). Overall, female participants perceived tasks to be more difficult (11.5 ± 4.2 vs. 9.6 ± 3.3; p = 0.016), perceived higher stress levels (8.9 ± 4.9 vs. 6.3 ± 4.4; p = 0.037), and rated their own performance lower (9.12 ± 3.3 vs. 11.3 ± 3.3; p = 0.009). However, female participants were able to correlate self-assessed with objective parameters correctly (r between -0.555 and -0.469; p = 0.004-0.018), whereas male participants failed to correctly rate their performance (p between 0.34 and 0.73). Stress levels correlated with objective parameters in males (r between 0.4 and 0.587; p < 0.005), but not in female participants. CONCLUSION: Perceived stress levels, self-evaluation skills, and catheter handling differ greatly between untrained male and female participants trying to solve interventional radiological tasks. These gender-specific differences should be considered in interventional radiology training. CLINICAL RELEVANCE STATEMENT: As psychological aspects may influence individual working strategies gender-specific differences in self-perception while learning interventional radiology maneuvers could be essential regarding success in teaching and treatment outcomes. KEY POINTS: • After performing standardized training, 38 male and 26 female volunteers showed significant differences regarding objective and self-assessed performance, as well as in perceived workload while performing simulated endovascular catheter maneuvers. • After solving simulated endovascular radiological tasks, female participants were able to self-assess their objective performance much more accurately than male participants. • Women took more time to solve simulated endovascular tasks and asked earlier and more frequently for help than men.

Deep Learning Reconstruction for Accelerated Spine MRI: Prospective Analysis of Interchangeability.

Background Deep learning (DL)-based MRI reconstructions can reduce examination times for turbo spin-echo (TSE) acquisitions. Studies that prospectively employ DL-based reconstructions of rapidly acquired, undersampled spine MRI are needed. Purpose To investigate the diagnostic interchangeability of an unrolled DL-reconstructed TSE (hereafter, TSEDL) T1- and T2-weighted acquisition method with standard TSE and to test their impact on acquisition time, image quality, and diagnostic confidence. Materials and Methods This prospective single-center study included participants with various spinal abnormalities who gave written consent from November 2020 to July 2021. Each participant underwent two MRI examinations: standard fully sampled T1- and T2-weighted TSE acquisitions (reference standard) and prospectively undersampled TSEDL acquisitions with threefold and fourfold acceleration. Image evaluation was performed by five readers. Interchangeability analysis and an image quality-based analysis were used to compare the TSE and TSEDL images. Acquisition time and diagnostic confidence were also compared. Interchangeability was tested using the individual equivalence index regarding various degenerative and nondegenerative entities, which were analyzed on each vertebra and defined as discordant clinical judgments of less than 5%. Interreader and intrareader agreement and concordance (κ and Kendall τ and W statistics) were computed and Wilcoxon and McNemar tests were used. Results Overall, 50 participants were evaluated (mean age, 46 years ± 18 [SD]; 26 men). The TSEDL method enabled up to a 70% reduction in total acquisition time (100 seconds for TSEDL vs 328 seconds for TSE, P < .001). All individual equivalence indexes were less than 4%. TSEDL acquisition was rated as having superior image noise by all readers (P < .001). No evidence of a difference was found between standard TSE and TSEDL regarding frequency of major findings, overall image quality, or diagnostic confidence. Conclusion The deep learning (DL)-reconstructed turbo spin-echo (TSE) method was found to be interchangeable with standard TSE for detecting various abnormalities of the spine at MRI. DL-reconstructed TSE acquisition provided excellent image quality, with a 70% reduction in examination time. German Clinical Trials Register no. DRKS00023278 © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Hallinan in this issue.

Free-breathing Arterial Spin Labeling MRI for the Detection of Pulmonary Embolism.

Background Arterial spin labeling (ASL) MRI can be used to assess organ perfusion but has yet to be implemented for perfusion evaluation of the lung. Purpose To evaluate pseudo-continuous ASL (PCASL) MRI for the detection of acute pulmonary embolism (PE) and its potential as an alternative to CT pulmonary angiography (CTPA). Materials and Methods Between November 2020 and November 2021, 97 patients (median age, 61 years; 48 women) with suspected PE were enrolled in this prospective study. PCASL MRI was performed within a 72-hour period following CTPA under free-breathing conditions and included three orthogonal planes. The pulmonary trunk was labeled during systole, and the image was acquired during diastole of the subsequent cardiac cycle. Additionally, multisection, coronal, balanced, steady-state free-precession imaging was carried out. Two radiologists blindly assessed overall image quality, artifacts, and diagnostic confidence (five-point Likert scale, 5 = best). Patients were categorized as positive or negative for PE, and a lobe-wise assessment in PCASL MRI and CTPA was conducted. Sensitivity and specificity were calculated on a patient level with the final clinical diagnosis serving as the reference standard. Interchangeability between MRI and CTPA was also tested with use of an individual equivalence index (IEI). Results PCASL MRI was performed successfully in all patients with high scores for image quality, artifact, and diagnostic confidence (κ ≥ .74). Of the 97 patients, 38 were positive for PE. PCASL MRI depicted PE correctly in 35 of 38 patients with three false-positive and three false-negative findings, resulting in a sensitivity of 35 of 38 patients (92% [95% CI: 79, 98]) and a specificity of 56 of 59 patients (95% [95% CI: 86, 99]). Interchangeability analysis revealed an IEI of 2.6% (95% CI: 1.2, 3.8). Conclusion Free-breathing pseudo-continuous arterial spin labeling MRI depicted abnormal lung perfusion caused by acute pulmonary embolism and may be useful as a contrast material-free alternative to CT pulmonary angiography for selected patients. German Clinical Trials Register no. DRKS00023599 © RSNA, 2023.

Prospective intraindividual comparison of a standard 2D TSE MRI protocol for ankle imaging and a deep learning-based 2D TSE MRI protocol with a scan time reduction of 48.

PURPOSE: Magnetic resonance imaging (MRI) scan time remains a limited and valuable resource. This study evaluates the diagnostic performance of a deep learning (DL)-based accelerated TSE study protocol compared to a standard TSE study protocol in ankle MRI. MATERIAL AND METHODS: Between October 2020 and July 2021 forty-seven patients were enrolled in this study for an intraindividual comparison of a standard TSE study protocol and a DL TSE study protocol either on a 1.5 T or a 3 T scanner. Two radiologists evaluated the examinations regarding structural pathologies and image quality categories (5-point-Likert-scale; 1 = "non diagnostic", 5 = "excellent"). RESULTS: Both readers showed almost perfect/perfect agreement of DL TSE with standard TSE in all analyzed structural pathologies (0.81-1.00) with a median "good" or "excellent" rating (4-5/5) in all image quality categories in both 1.5 T and 3 T MRI. The reduction of total acquisition time of DL TSE compared to standard TSE was 49% in 1.5 T and 48% in 3 T MRI to a total acquisition time of 5 min 41 s and 5 min 46 s. CONCLUSION: In ankle MRI the new DL-based accelerated TSE study protocol delivers high agreement with standard TSE and high image quality, while reducing the acquisition time by 48%.

Feasibility of an accelerated 2D-multi-contrast knee MRI protocol using deep-learning image reconstruction: a prospective intraindividual comparison with a standard MRI protocol.

OBJECTIVES: The aim of this study was to evaluate the image quality and diagnostic performance of a deep-learning (DL)-accelerated two-dimensional (2D) turbo spin echo (TSE) MRI of the knee at 1.5 and 3 T in clinical routine in comparison to standard MRI. MATERIAL AND METHODS: Sixty participants, who underwent knee MRI at 1.5 and 3 T between October/2020 and March/2021 with a protocol using standard 2D-TSE (TSES) and DL-accelerated 2D-TSE sequences (TSEDL), were enrolled in this prospective institutional review board-approved study. Three radiologists assessed the sequences regarding structural abnormalities and evaluated the images concerning overall image quality, artifacts, noise, sharpness, subjective signal-to-noise ratio, and diagnostic confidence using a Likert scale (1-5, 5 = best). RESULTS: Overall image quality for TSEDL was rated to be excellent (median 5, IQR 4-5), significantly higher compared to TSES (median 5, IQR 4 - 5, p < 0.05), showing significantly lower extents of noise and improved sharpness (p < 0.001). Inter- and intra-reader agreement was almost perfect (κ = 0.92-1.00) for the detection of internal derangement and substantial to almost perfect (κ = 0.58-0.98) for the assessment of cartilage defects. No difference was found concerning the detection of bone marrow edema and fractures. The diagnostic confidence of TSEDL was rated to be comparable to that of TSES (median 5, IQR 5-5, p > 0.05). Time of acquisition could be reduced to 6:11 min using TSEDL compared to 11:56 min for a protocol using TSES. CONCLUSION: TSEDL of the knee is clinically feasible, showing excellent image quality and equivalent diagnostic performance compared to TSES, reducing the acquisition time about 50%. KEY POINTS: • Deep-learning reconstructed TSE imaging is able to almost halve the acquisition time of a three-plane knee MRI with proton density and T1-weighted images, from 11:56 min to 6:11 min at 3 T. • Deep-learning reconstructed TSE imaging of the knee provided significant improvement of noise levels (p < 0.001), providing higher image quality (p < 0.05) compared to conventional TSE imaging. • Deep-learning reconstructed TSE imaging of the knee had similar diagnostic performance for internal derangement of the knee compared to standard TSE.

[Primary treatment of prostate cancer using 1.5 T MR-linear accelerator]. / Stellenwert des 1,5-T-MR-Linearbeschleunigers für die primäre Therapie des Prostatakarzinoms.

BACKGROUND: Hybrid devices of MR-scanners and linear accelerators (MR-Linacs) represent a new and promising extension of radiotherapeutic options for prostate cancer. The potential advantage of magnetic resonance imaging (MRI) over computed tomography (CT) for soft tissue contrast is well-known and leads to more consistent and smaller target volumes and improved normal tissue sparing. OBJECTIVES: This article presents an overview of clinical experience, indications, advantages and challenges of utilizing a 1.5 T MR-Linac in the setting of radiotherapy of prostate cancer. RESULTS: All current indications for radiotherapy of prostate cancer can be treated with an MR-Linac. The advantages include daily MR-based imaging in treatment position and daily adaption of the treatment plan on current anatomy (adaptive radiotherapy). Additionally, functional MRI sequences might be exploited to enhance treatment individualization and response assessment. Ultimately treatment on an MR-Linac might further increase the therapeutic window. The limitations of using MR-Linac include treatment complexity and the duration of each session. CONCLUSIONS: MR-Linacs expand the spectrum of radiotherapeutic options for prostate cancer. Increased precision can be reached with daily MRI-based target volume definition and plan adaption. Clinical studies are necessary to identify patient groups who would benefit most from radiotherapy on a MR-Linac.

Imaging Pulmonary Blood Flow Using Pseudocontinuous Arterial Spin Labeling (PCASL) With Balanced Steady-State Free-Precession (bSSFP) Readout at 1.5T.

BACKGROUND: Quantitative assessment of pulmonary blood flow and visualization of its temporal and spatial distribution without contrast media is of clinical significance. PURPOSE: To assess the potential of electrocardiogram (ECG)-triggered pseudocontinuous arterial spin labeling (PCASL) imaging with balanced steady-state free-precession (bSSFP) readout to measure lung perfusion under free-breathing (FB) conditions and to study temporal and spatial characteristics of pulmonary blood flow. STUDY TYPE: Prospective, observational. SUBJECTS: Fourteen volunteers; three patients with pulmonary embolism. FIELD STRENGTH/SEQUENCES: 1.5T, PCASL-bSSFP. ASSESSMENT: The pulmonary trunk was labeled during systole. The following examinations were performed: 1) FB and timed breath-hold (TBH) examinations with a postlabeling delay (PLD) of 1000 msec, and 2) TBH examinations with multiple PLDs (100-1500 msec). Scan-rescan measurements were performed in four volunteers and one patient. Images were registered and the perfusion was evaluated in large vessels, small vessels, and parenchyma. Mean structural similarity indices (MSSIM) was computed and time-to-peak (TTP) of parenchymal perfusion in multiple PLDs was evaluated. Image quality reading was performed with three independent blinded readers. STATISTICAL TESTS: Wilcoxon test to compare MSSIM, perfusion, and Likert scores. Spearman's correlation to correlate TTP and cardiac cycle duration. The repeatability coefficient (RC) and within-subject coefficient of variation (wCV) for scan-rescan measurements. Intraclass correlation coefficient (ICC) for interreader agreement. RESULTS: Image registration resulted in a significant (P < 0.05) increase of MSSIM. FB perfusion values were 6% higher than TBH (3.28 ± 1.09 vs. 3.10 ± 0.99 mL/min/mL). TTP was highly correlated with individuals' cardiac cycle duration (Spearman = 0.89, P < 0.001). RC and wCV were better for TBH than FB (0.13-0.19 vs. 0.47-1.54 mL/min/mL; 6-7 vs. 19-60%). Image quality was rated very good, with ICCs 0.71-0.89. DATA CONCLUSION: ECG-triggered PCASL-bSSFP imaging of the lung at 1.5T can provide very good image quality and quantitative perfusion maps even under FB. The course of labeled blood through the lung shows a strong dependence on the individuals' cardiac cycle duration. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 2 J. MAGN. RESON. IMAGING 2020;52:1767-1782.

Reduced scan range abdominopelvic CT in patients with suspected acute appendicitis - impact on diagnostic accuracy and effective radiation dose.

BACKGROUND: To evaluate a reduced range CT protocol in patients with suspected acute appendicitis as compared to standard abdominal CT regarding diagnostic performance, effective radiation dose and organ doses. METHODS: In this study, we retrospectively included 90 patients (43 female, mean age 56.7 ± 17 years) with suspected acute appendicitis who underwent CT of abdomen and pelvis. From those CTs, we reconstructed images with a reduced scan range from L1 to the the pubic symphysis. Full range and reduced range datasets were assessed by two radiologists for i) coverage of the Appendix, ii) presence/absence of appendicitis and iii) presence of differential diagnoses. Furthermore, effective radiation doses as well as organ doses were calculated using a commercially available dose management platform (Radimetrics, Bayer HealthCare). RESULTS: The Appendix was covered by the reduced range CT in all cases. In 66 patients CT confirmed the presence of appendicitis. In 14 patients, other relevant differential diagnoses were identified by CT, whereas in 10 patients no relevant findings were detected. Both readers identified all patients with appendicitis on both full and reduced range CT. For reduced range CT, total effective dose was 39% lower than for full range CT (reduced range: 4.5 [1.9-11.2] vs. full range: 7.4 [3.3-18.8] mSv; p ≤ 0.001). Notably, a remarkable reduction of organ dose in the female breasts by 97% (0.1 [0.1-0.6] vs. 3.8 [0.5-18.8] mSv; p ≤ 0.001) and in the testicles in males by 81% (3.4 [0.7-32.7] vs. 17.6 [5.4-52.9] mSv; p ≤ 0.001) was observed for reduced range CT compared to full range CT. CONCLUSIONS: In patients with suspected acute appendicitis, reduced range abdominopelvic CT results in a comparable diagnostic performance with a remarkable reduction of total effective radiation dose and organ doses (especially breast dose in female and testicle dose in male patients) as compared to full range CT.

Diagnostic Accuracy of Simulated Low-Dose Perfusion CT to Detect Cerebral Perfusion Impairment after Aneurysmal Subarachnoid Hemorrhage: A Retrospective Analysis.

Purpose To evaluate diagnostic accuracy of low-dose volume perfusion (VP) computed tomography (CT) compared with original VP CT regarding the detection of cerebral perfusion impairment after aneurysmal subarachnoid hemorrhage. Materials and Methods In this retrospective study, 85 patients (mean age, 59.6 years; 62 women) with aneurysmal subarachnoid hemorrhage and who were suspected of having cerebral vasospasm at unenhanced CT and VP CT (tube voltage, 80 kVp; tube current-time product, 180 mAs) were included, 37 of whom underwent digital subtraction angiography (DSA) within 6 hours. Low-dose VP CT data sets at tube current-time product of 72 mAs were retrospectively generated by validated realistic simulation. Perfusion maps were generated from both data sets and reviewed by two neuroradiologists for overall image quality, diagnostic confidence and presence and/or severity of perfusion impairment indicating vasospasm. An interventional neuroradiologist evaluated 16 vascular segments at DSA. Diagnostic accuracy of low-dose VP CT was calculated with original VP CT as reference standard. Agreement between findings of both data sets was assessed by using weighted Cohen κ and findings were correlated with DSA by using Spearman correlation. After quantitative volumetric analysis, lesion volumes were compared on both VP CT data sets. Results Low-dose VP CT yielded good ratings of image quality and diagnostic confidence and classified all patients correctly with high diagnostic accuracy (sensitivity, 99.0%; specificity, 99.5%) without significant differences regarding presence and/or severity of perfusion impairment between original and low-dose data sets (Z = -0.447; P = .655). Findings of both data sets correlated significantly with DSA (original, r = 0.671; low dose, r = 0.667). Lesion volume was comparable for both data sets (relative difference, 5.9% ± 5.1 [range, 0.2%-25.0%; median, 4.0%]) with strong correlation (r = 0.955). Conclusion The results suggest that radiation dose reduction to 40% of original dose levels (tube current-time product, 72 mAs) may be performed in VP CT imaging of patients with aneurysmal subarachnoid hemorrhage without compromising the diagnostic accuracy regarding detection of cerebral perfusion impairment indicating vasospasm. © RSNA, 2018 Online supplemental material is available for this article.

Cost-effectiveness of Endovascular Therapy for Acute Ischemic Stroke: A Systematic Review of the Impact of Patient Age.

Purpose To determine the impact of patient age on the cost-effectiveness of endovascular therapy (EVT) in addition to standard care (SC) in large-vessel-occlusion stroke for patients aged 50 to 100 years in the United States. Materials and Methods A decision-analytic Markov model was used to estimate direct and indirect lifetime costs and quality-adjusted life years (QALYs). Age-dependent input parameters were obtained from the literature. Deterministic and probabilistic sensitivity analysis for age at index stroke were used. The willingness-to-pay (WTP) was set to thresholds of $50 000, $100 000, and $150 000 per QALY. The study applied a U.S. setting for health care and societal perspectives. Incremental costs and effectiveness were derived from deterministic and probabilistic sensitivity analysis. Acceptability rates at different WTP thresholds were determined. Results EVT+SC was the dominant strategy in patients aged 50 to 79 years. The highest incremental effectiveness (2.61 QALYs) and cost-savings (health care perspective, $99 555; societal perspective, $146 385) were obtained in 50-year-old patients. In octogenarians (80-89 years), EVT+SC led to incremental QALYs at incremental costs with acceptability rates of more than 85%, more than 99%, and more than 99% at a WTP of $50 000, $100 000, and $150 000 per QALY, respectively. In nonagenarians (90-99 years), acceptability rates at a WTP of $50 000 per QALY dropped but stayed higher than 85% and higher than 95% at thresholds of $100 000 and $150 000 per QALY. Conclusion Using contemporary willingness-to-pay thresholds in the United States, endovascular therapy in addition to standard care reduces lifetime costs for patients up to 79 years of age and is cost-effective for patients aged 80 to 100 years.

Self-gated 4D-MRI of the liver: Initial clinical results of continuous multiphase imaging of hepatic enhancement.

PURPOSE: To evaluate the feasibility of a self-gated free-breathing volume-interpolated breath-hold examination (VIBE) sequence using compressed sensing (CS) for contrast-enhanced multiphase liver MRI. MATERIALS AND METHODS: We identified 23 patients who underwent multiphase gadobutrol-enhanced liver magnetic resonance imaging (MRI) using 1) a prototype free-breathing VIBE sequence with respiratory self-gating and CS (VIBECS ), and 2) a standard breath-hold VIBE (VIBESTD ) on the same 1.5T scanner at two timepoints. VIBECS was continuously acquired for 128 seconds and a time-series of 16 timepoints was jointly reconstructed from the dataset. The unenhanced, arterial, portal-venous, and venous timepoints with the best image quality were selected and compared to the corresponding VIBESTD series serving as reference. Image quality was assessed qualitatively (image quality, sharpness, lesion conspicuity, vessel contrast, noise, motion/other artifacts; two readers independently; 5-point Likert scale; 5 = excellent) and quantitatively (vessel contrast [VC], coefficient-of-variation [CV]) Statistics were performed using Wilcoxon-sign-rank (ordinal) and paired t-test (continuous variables). RESULTS: Image quality and lesion conspicuity revealed no significant differences between the sequences (P ≥ 0.3). VIBESTD showed a tendency to higher motion artifacts (P ≥ 0.07). Image sharpness significantly increased in VIBECS as compared to VIBESTD (P ≤ 0.03). Arterial phase vessel contrast appeared significantly lower in VIBECS than in VIBESTD (P = 0.04). VIBECS showed reconstruction artifacts not present in VIBESTD (P = 0.001). Image noise was significantly lower in VIBECS than in VIBESTD (P ≤ 0.004). Arterial phase VC was significantly lower in VIBECS than in VIBESTD (P = 0.01). CV revealed no differences between sequences (P = 0.7). CONCLUSION: VIBECS is feasible for continuous free-breathing contrast-enhanced multiphase liver MRI, providing similar image quality and lesion conspicuity as VIBESTD . LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:459-467.

Impact of dual-energy CT post-processing to differentiate venous thrombosis from iodine flux artefacts.

OBJECTIVES: To investigate the accuracy of dual-energy (DE) CT-based iodine maps (IM) and noise-optimised monoenergetic extrapolations (MEI+) at 40 keV for the detection and differentiation of venous thrombosis (VT) from iodine flux artefacts (IFA) in comparison to portal-venous phase CT (CTPV). METHODS: Ninety-nine patients were enrolled in this study. In all patients, VT or IFA was suspected on contrast-enhanced CT and confirmed by follow-up CT or colour-coded ultrasound. All examinations were performed on a third-generation dual-source CT system in DE mode during portal-venous phase. CTPV, IM and 40-keV MEI+ were reconstructed and independently evaluated by two radiologists for the presence/absence of VT and/or IFA. Diagnostic confidence was rated on a three-point scale (3 = high confidence). Quantitative parameters were obtained by calculating contrast-to-noise ratios (CNRs), iodine content and thrombus volume. Diagnostic accuracy was assessed by calculating receiver operating characteristics (ROC) of CNR. RESULTS: Diagnostic confidence was significantly higher for IM and MEI+ [both 3 (2-3)] compared to CTPV [2 (1-3); p ≤ 0.03]. ROC analysis revealed significantly higher AUC values and increased sensitivity for IM and MEI+ (AUC = 88%/sensitivity = 79.1% and 86%/73.1%) than for CTPV (75%/61.2%; p ≤ 0.01). Thrombus volume was significantly higher in MEI+ than in IM and CTPV (p < 0.001). CNR of thrombosis was significantly higher in IM [11.5 (8.5-14.5), p < 0.001) and MEI+ [10.9 (8.8-15.5), p < 0.001] than in CTPV [8.2 (5.8-11.4)]. Iodine quantification revealed significantly lower results in VT than in IFA [0.55 mg/ml (0.23-0.90) and 1.81 (1.60-2.12) mg/ml; p < 0.001]. CONCLUSIONS: IM and MEI+ 40 keV showed significantly higher diagnostic confidence and accuracy for the detection and differentiation of VT from IFA in comparison to CTPV. KEY POINTS: • Iodine maps and noise-optimised monoenergetic extrapolations at 40 keV increase diagnostic confidence and accuracy for the detection and differentiation of venous thrombosis from iodine flux artefacts. • Dual-energy post-processing can significantly increase contrast-to-noise ratio and the sensitivity for the diagnosis of venous thrombosis • Iodine load in venous thrombosis is significantly lower than in iodine flux artefacts.

Optimisation of window settings for traditional and noise-optimised virtual monoenergetic imaging in dual-energy computed tomography pulmonary angiography.

OBJECTIVES: To define optimal window settings for displaying virtual monoenergetic images (VMI) of dual-energy CT pulmonary angiography (DE-CTPA). METHODS: Forty-five patients who underwent clinically-indicated third-generation dual-source DE-CTPA were retrospectively evaluated. Standard linearly-blended (M_0.6), 70-keV traditional VMI (M70), and 40-keV noise-optimised VMI (M40+) reconstructions were analysed. For M70 and M40+ datasets, the subjectively best window setting (width and level, B-W/L) was independently determined by two observers and subsequently related with pulmonary artery attenuation to calculate separate optimised values (O-W/L) using linear regression. Subjective evaluation of image quality (IQ) between W/L settings were assessed by two additional readers. Repeated measures of variance were performed to compare W/L settings and IQ indices between M_0.6, M70, and M40+. RESULTS: B-W/L and O-W/L for M70 were 460/140 and 450/140, and were 1100/380 and 1070/380 for M40+, respectively, differing from standard DE-CTPA W/L settings (450/100). Highest subjective scores were observed for M40+ regarding vascular contrast, embolism demarcation, and overall IQ (all p<0.001). CONCLUSIONS: Application of O-W/L settings is beneficial to optimise subjective IQ of VMI reconstructions of DE-CTPA. A width slightly less than two times the pulmonary trunk attenuation and a level approximately of overall pulmonary vessel attenuation are recommended. KEY POINTS: • Application of standard window settings for VMI results in inferior image perception. • No significant differences between B-W/L and O-W/L for M70/M40+ were observed. • O-W/L for M70 were 450/140 and were 1070/380 for M40+. • Improved subjective IQ characteristics were observed for VMI displayed with O-W/L.

Evaluation of reduced-dose CT for acute non-traumatic abdominal pain: evaluation of diagnostic accuracy in comparison to standard-dose CT.

Background Patients with acute non-traumatic abdominal pain often undergo abdominal computed tomography (CT). However, abdominal CT is associated with high radiation exposure. Purpose To evaluate diagnostic performance of a reduced-dose 100 kVp CT protocol with advanced modeled iterative reconstruction as compared to a linearly blended 120 kVp protocol for assessment of acute, non-traumatic abdominal pain. Material and Methods Two radiologists assessed 100 kVp and linearly blended 120 kVp series of 112 consecutive patients with acute non-traumatic pain (onset < 48 h) regarding image quality, noise, and artifacts on a five-point Likert scale. Both radiologists assessed both series for abdominal pathologies and for diagnostic confidence. Both 100 kVp and linearly blended 120 kVp series were quantitatively evaluated regarding radiation dose and image noise. Comparative statistics and diagnostic accuracy was calculated using receiver operating curve (ROC) statistics, with final clinical diagnosis/clinical follow-up as reference standard. Results Image quality was high for both series without detectable significant differences ( P = 0.157). Image noise and artifacts were rated low for both series but significantly higher for 100 kVp ( P ≤ 0.021). Diagnostic accuracy was high for both series (120 kVp: area under the curve [AUC] = 0.950, sensitivity = 0.958, specificity = 0.941; 100 kVp: AUC ≥ 0.910, sensitivity ≥ 0.937, specificity = 0.882; P ≥ 0.516) with almost perfect inter-rater agreement (Kappa = 0.939). Diagnostic confidence was high for both dose levels without significant differences (100 kVp 5, range 4-5; 120 kVp 5, range 3-5; P = 0.134). The 100 kVp series yielded 26.1% lower radiation dose compared with the 120 kVp series (5.72 ± 2.23 mSv versus 7.75 ± 3.02 mSv, P < 0.001). Image noise was significantly higher in reduced-dose CT (13.3 ± 2.4 HU versus 10.6 ± 2.1 HU; P < 0.001). Conclusion Reduced-dose abdominal CT using 100 kVp yields excellent image quality and high diagnostic accuracy for the assessment of acute non-traumatic abdominal pain.

Transfer of stroke patients impairs eligibility for endovascular stroke treatment.

BACKGROUND: Many patients who are potentially eligible for endovascular stroke treatment (EST) receive intravenous rtPA in the closest stroke unit before being transferred to tertiary centres for EST. It has been shown that clinical outcome of transferred and EST-treated patients is comparable to that of patients with direct access to EST. We analysed clinical outcome of patients, who were transferred and eventually not treated due to clinical and/or radiological deterioration. METHODS: We retrospectively analysed our prospectively maintained stroke registry for patients who were transferred for stroke therapy. RESULTS: Four hundred twenty-two of 1208 patients (35.1%), who were admitted for acute reperfusion stroke therapy between 03/10 and 01/15 were eligible for EST. Ninety-one (7.5%) of these patients were admitted specifically for EST from remote hospitals. Favorable clinical outcome rates after 90 days (mRS≤2) were comparable between 63 transferred and 295 directly-admitted patients, who received EST (P=0.699). However, transferred patients, who were eligible for EST on initial admission, were less likely to receive EST after transfer (P<0.001): twenty-two of 91 patients (24.2%), who were transferred for EST, became ineligible during transfer due to infarct demarcation. Procedural times of treated and untreated transferred patients were comparable (P≥0.508). There was a trend towards worse clinical outcome in untreated patients, without reaching statistical significance (OR, 0.269; 95% CI, 0.55-1.324; P=0.119). CONCLUSIONS: EST should be provided directly whenever possible as one in four transferred stroke patients becomes ineligible for EST during transfer. If direct transfer is not possible, indication for EST should be re-assessed after transfer.

Diagnostic performance of different perfusion algorithms for the detection of angiographical spasm.

PURPOSE: To assess the diagnostic utility of different perfusion algorithms for the detection of angiographical terial spasm. METHOD: During a 2-year period, 45 datasets from 29 patients (54.2±10,75y, 20F) with suspected cerebral vasospasm after aneurysmal subarachnoid hemorrhage were included. Volume Perfusion CT (VPCT), Non-enhanced CT (NCT) and angiography were performed within 6hours post-ictus. Perfusion maps were generated using a maximum slope (MS) and a deconvolution-based approach (DC). Two blinded neuroradiologists independently evaluated MS and DC maps regarding vasospasm-related perfusion impairment on a 3-point Likert-scale (0=no impairment, 1=impairment affecting <50%, 2=impairment affecting >50% of vascular territory). A third independent neuroradiologist assessed angiography for presence and severity of arterial narrowing on a 3-point Likert scale (0=no narrowing, 1=narrowing affecting <50%, 2=narrowing affecting>50% of artery diameter). MS and DC perfusion maps were evaluated regarding diagnostic accuracy for angiographical arterial spasm with angiography as reference standard. Correlation analysis of angiography findings with both MS and DC perfusion maps was additionally performed. Furthermor, the agreement between MS and DC and inter-reader agreement was assessed. RESULTS: DC maps yielded significantly higher diagnostic accuracy than MS perfusion maps (DC:AUC=.870; MS:AUC=.805; P=0.007) with higher sensitivity for DC compared to MS (DC:sensitivity=.758; MS:sensitivity=.625). DC maps revealed stronger correlation with angiography than MS (DC: R=.788; MS: R=694;=<0.001). MS and DC showed substantial agreement (Kappa=.626). Regarding inter-reader analysis, (almost) perfect inter-reader agreement was observed for both MS and DC maps (Kappa≥981). CONCLUSION: DC yields significantly higher diagnostic accuracy for the detection of angiographic arterial spasm and higher correlation with angiographic findings compared to MS.