Impaired cerebral autoregulation and neurovascular coupling (NVC) contribute to delayed cerebral ischemia after subarachnoid hemorrhage (SAH). Retinal vessel analysis (RVA) allows non-invasive assessment of vessel dimension and NVC hereby demonstrating a predictive value in the context of various neurovascular diseases. Using RVA as a translational approach, we aimed to assess the retinal vessels in patients with SAH. RVA was performed prospectively in 24 patients with acute SAH (group A: day 5-14), in 11 patients 3 months after ictus (group B: day 90 ± 35), and in 35 age-matched healthy controls (group C). Data was acquired using a Retinal Vessel Analyzer (Imedos Systems UG, Jena) for examination of retinal vessel dimension and NVC using flicker-light excitation. Diameter of retinal vessels-central retinal arteriolar and venular equivalent-was significantly reduced in the acute phase (p < 0.001) with gradual improvement in group B (p < 0.05). Arterial NVC of group A was significantly impaired with diminished dilatation (p < 0.001) and reduced area under the curve (p < 0.01) when compared to group C. Group B showed persistent prolonged latency of arterial dilation (p < 0.05). Venous NVC was significantly delayed after SAH compared to group C (A p < 0.001; B p < 0.05). To our knowledge, this is the first clinical study to document retinal vasoconstriction and impairment of NVC in patients with SAH. Using non-invasive RVA as a translational approach, characteristic patterns of compromise were detected for the arterial and venous compartment of the neurovascular unit in a time-dependent fashion. Recruitment will continue to facilitate a correlation analysis with clinical course and outcome.

Objectives: To investigate if low-keV virtual monoenergetic images (VMI40keV) from abdominal spectral detector CT (SDCT)with reducedintravenous contrast media (RCM) provide abdominal assessment similar to conventionalimages with standard contrast media dose (SCM). Methods: 78 patients with abdominal SDCT were retrospectively included: 41 patients at risk for adverse reactions who received 44 RCM examinations with 50 ml and 37 patients who underwent 44 SCM examinations with 100 ml of contrast media and who were matched for effective body diameters. RCM, SCM images and RCM-VMI40keV were reconstructed.Attenuation and signal-to-noise-ratio (SNR) of liver, pancreas, kidneys, lymph nodes, aorta and portal vein were assessed ROI-based. Contrast-to-noise-ratios (CNR) of lymph nodes vs aorta/portal vein were calculated. Two readers assessed organ/vessel contrast,lymph node delineation, image noise and overall assessability using 4-point Likert scales. Results: RCMwere inferior to SCM in all quantitative/qualitative criteria. RCM-VMI40keV andSCM images showed similar lymph node attenuation (p = 0.83), while for all other ROIs, RCM-VMI40keV showed higher attenuation(p ≤ 0.05). SNR was comparable between RCM-VMI40keV and SCM images (p-range:0.23–0.99).CNR of lymph nodes was highest in RCM-VMI40keV (p ≤ 0.05). RCM-VMI40keV received equivalent or higher scores than SCM in all criteria except for organ contrast, overall assessability and image noise, where SCM were superior (p ≤ 0.05). However, RCM-VMI40keVreceived proper or excellent scores in 88.6/94.2/95.4% of the referring cases. Conclusions: VMI40keV counteract contrast deterioration in contrast media reducedabdominal SDCT, facilitating diagnostic assessment. Advances in knowledge: SDCT-derived VMI40keV provide adequate depiction of vessels, organs and lymph nodes even at notable contrast media reduction.

Purpose The aims of this study were to evaluate spectral detector CT (SDCT)–derived iodine concentration (IC) of lymph nodes diagnosed as metastatic and benign in prostate-specific membrane antigen (PSMA) PET/CT and to assess its potential use for lymph node assessment in prostate cancer. Patients and Methods Thirty-four prostate cancer patients were retrospectively included: 16 patients with and 18 without lymph node metastases as determined by PSMA PET/CT. Patients underwent PSMA PET/CT as well as portal venous phase abdominal SDCT for clinical cancer follow-up. Only scan pairs with a stable nodal status indicated by constant size as well as comparable prostate-specific antigen (PSA) levels were included. One hundred benign and 96 suspected metastatic lymph nodes were annotated and correlated between SDCT and PSMA PET/CT. Iodine concentration in SDCT-derived iodine maps and SUVmax in ultra-high definition reconstructions from PSMA PET/CT were acquired based on the region of interest. Results Metastatic lymph nodes as per PSMA PET/CT showed higher IC than nonmetastatic nodes (1.9 ± 0.6 mg/mL vs 1.5 ± 0.5 mg/mL, P < 0.05) resulting in an AUC of 0.72 and sensitivity/specificity of 81.3%/58.5%. The mean short axis diameter of metastatic lymph nodes was larger than that of nonmetastatic nodes (6.9 ± 3.6 mm vs 5.3 ± 1.3 mm; P < 0.05); a size threshold of 1 cm short axis diameter resulted in a sensitivity/specificity of 12.8%/99.0%. There was a significant yet weak positive correlation between SUVmax and IC (r s = 0.25; P < 0.001). Conclusions Spectral detector CT–derived IC was increased in lymph nodes diagnosed as metastatic in PSMA PET/CT yet showed considerable data overlap. The correlation between IC and SUVmax was weak, highlighting the role of PSMA PET/CT as important reference imaging modality for detection of lymph node metastases in prostate cancer patients.

Background MRI follow‐up is widely used for longitudinal assessment of astrocytoma, yet reading can be tedious and error‐prone, in particular when changes are subtle. Purpose/Hypothesis To determine the effect of automated, color‐coded coregistration (AC) of fluid attenuated inversion recovery (FLAIR) sequences on diagnostic accuracy, certainty, and reading time compared to conventional follow‐up MRI assessment of astrocytoma patients. Study Type Retrospective. Population In all, 41 patients with neuropathologically confirmed astrocytoma. Field Strength/Sequence 1.0–3.0T/FLAIR Assessment The presence or absence of tumor progression was determined based on FLAIR sequences, contrast‐enhanced T1 sequences, and clinical data. Three radiologists assessed 47 MRI study pairs in a conventional reading (CR) and in a second reading supported by AC after 6 weeks. Readers determined the presence/absence of tumor progression and indicated diagnostic certainty on a 5‐point Likert scale. Reading time was recorded by an independent assessor. Statistical Tests The Wilcoxon test was used to assess reading time and diagnostic certainty. Differences in diagnostic accuracy, sensitivity, and specificity were analyzed with the McNemar mid‐p test. Results Readers attained significantly higher overall sensitivity (0.86 vs. 0.75; P < 0.05) and diagnostic accuracy (0.84 vs. 0.73; P < 0.05) for detection of progressive nonenhancing tumor burden when using AC compared to CR. There was a strong trend towards higher specificity within the AC‐augmented reading, yet without statistical significance (0.83 vs. 0.71; P = 0.08). Sensitivity for unequivocal disease progression was similarly high in both approaches (AC: 0.94, CR: 0.92), while for marginal disease progressions, it was significantly higher in AC (AC: 0.78, CR: 0.58; P < 0.05). Reading time including application loading time was comparable (AC: 38.1 ± 16.8 sec, CR: 36.0 ± 18.9 s; P = 0.25). Data Conclusion Compared to CR, AC improves comparison of FLAIR signal hyperintensity at MRI follow‐up of astrocytoma patients, allowing for a significantly higher diagnostic accuracy, particularly for subtle disease progression at a comparable reading time. Evidence Level 3 Technical Efficacy Stage 6 J. Magn. Reson. Imaging 2020;52:1197–1206.