Reduced magnetic resonance angiography signal intensity in the middle cerebral artery ipsilateral to severe carotid stenosis may be a practical index of high oxygen extraction fraction

Objectives Angiographic “slow flow” in the middle cerebral artery (MCA), caused by carotid stenosis, may be associated with high oxygen extraction fraction (OEF). If the MCA slow flow is associated with a reduced relative signal intensity (rSI) of the MCA on MR angiography, the reduced rSI may be associated with a high OEF. We investigated whether the MCA slow flow ipsilateral to carotid stenosis was associated with a high OEF and aimed to create a practical index to estimate the high OEF. Methods We included patients who underwent digital subtraction angiography (DSA) and MRA between 2015 and 2019 to evaluate carotid stenosis. MCA slow flow by image count using DSA, MCA rSI, minimal luminal diameter (MLD) of the carotid artery, carotid artery stenosis rate (CASr), and whole-brain OEF (wb-OEF) was evaluated. When MCA slow flow was associated with a high wb-OEF, the determinants of MCA slow flow were identified, and their association with high wb-OEF was evaluated. Results One hundred and twenty-seven patients met our inclusion criteria. Angiographic MCA slow flow was associated with high wb-OEF. We identified MCA rSI and MLD as determinants of angiographic MCA slow flow. The upper limits of MCA rSI and MLD for angiographic MCA slow flow were 0.89 and 1.06 mm, respectively. The wb-OEF was higher in patients with an MCA rSI ≤ 0.89 and ipsilateral MLD ≤ 1.06 mm than patients without this combination. Conclusions The combination of reduced MCA rSI and ipsilateral narrow MLD is a straightforward index of high wb-OEF. Key Points • The whole-brain OEF in patients with angiographic slow flow in the MCA ipsilateral to high-grade carotid stenosis was higher than in patients without it. • Independent determinants of MCA slow flow were MCA relative signal intensity (rSI) on MRA or minimal luminal diameter (MLD) of the carotid stenosis. • The wb-OEF was higher in patients with an MCA rSI ≤ 0.89 and ipsilateral MLD ≤ 1.06 mm than patients without this combination.

Quantitative Flow Ratio Is Associated with Extent and Severity of Ischemia in Non-Culprit Lesions of Patients with Myocardial Infarction

Quantitative flow ratio (QFR) is a novel method to assess the relevance of coronary stenoses based only on angiographic projections. We could previously show that QFR is able to predict the hemodynamic relevance of non-culprit lesions in patients with myocardial infarction. However, it is still unclear whether QFR is also associated with the extent and severity of ischemia, which can effectively be assessed with imaging modalities such as cardiac magnetic resonance (CMR). Thus, our aim was to evaluate the associations of QFR with both extent and severity of ischemia. We retrospectively determined QFR in 182 non-culprit coronary lesions from 145 patients with previous myocardial infarction, and compared it with parameters assessing extent and severity of myocardial ischemia in staged CMR. Whereas ischemic burden in lesions with QFR > 0.80 was low (1.3 ± 5.5% in lesions with QFR ≥ 0.90; 1.8 ± 7.3% in lesions with QFR 0.81–0.89), there was a significant increase in ischemic burden in lesions with QFR ≤ 0.80 (16.6 ± 15.6%; p < 0.001 for QFR ≥ 0.90 vs. QFR ≤ 0.80). These data could be confirmed by other parameters assessing extent of ischemia. In addition, QFR was also associated with severity of ischemia, assessed by the relative signal intensity of ischemic areas. Finally, QFR predicts a clinically relevant ischemic burden ≥ 10% with good diagnostic accuracy (AUC 0.779, 95%-CI: 0.666–0.892, p < 0.001). QFR may be a feasible tool to identify not only the presence, but also extent and severity of myocardial ischemia in non-culprit lesions of patients with myocardial infarction.

MRI T2-Weighted Cochlear Intensity as a Predictor of Hearing Loss with Vestibular Schwannoma Patients

Objective It is difficult to predict how hearing loss will progress with vestibular schwannomas (VSs) and to determine the optimal time for hearing preservation interventions. This study investigated the relationship between cochlear intensity on T2-weighted magnetic resonance imaging and hearing loss in VS patients over time. Design Retrospective cohort study. Setting Single major academic center. Participants Patients with a diagnosis of VS from 2007 to 2018. Main Outcome Measures Pure tone average (PTA) and cochlear-to-pontine relative signal intensity (RSI) measured at two time points. Results Fifty patients were included in the final analysis. For both affected and unaffected ears, the trend in PTA increased from baseline to follow-up. For affected ears, the trend in RSI increased from baseline to follow-up, while for the unaffected ears RSI decreased. There was a significant positive correlation between the initial RSI value in the ipsilateral ear when compared with the change in PTA from baseline to follow-up (r = 0.28, p = 0.048). Conclusion There is a trend between initial RSI and how hearing changes in the affected ears of patients with VS. Additional studies are needed to explore how this relationship may be better used to predict hearing loss.

Anterior Knee Pain and Oedema-Like Changes of The Suprapatellar Fat Pad: Correlation of The Symptoms with MRI Findings

Objective: To evaluate the role of oedema like changes of the suprapatellar fat pad in the development of anterior knee pain. Methods: Total 156 knee MRIs of 150 patients from December 2015 to July 2019 were retrospectively evaluated by a radiologist with 13 years of MRI experience for the configuration of the suprapatellar fat pads. Population was divided into two groups according to referring physicians’ notes for presence of anterior knee pain. The study group consisted of the patients with complaints of anterior knee pain. The control group consisted of patients without anterior knee pain. Maximum craniocaudal, anteroposterior and oblique diameters and relative signal intensity indexes of the suprapatellar fat pads were measured and compared between the groups. Configurations of the fat pads were recorded (triangular shaped vs convex posterior bordered suprapatellar fat pads), and measurements of the triangular shaped and convex posterior bordered suprapatellar fat pads were compared. Student t test was used for statistical analysis. Statistically significant differences and correlations were defined as p<0.05. Results: The diameters and relative signal intensity indexes of the fat pads showed no significant difference between the groups (p=0.588, 0.744, 0.874 and 0.201, respectively). Anteroposterior and oblique diameters and relative signal intensity indexes of the suprapatellar fat pads were correlated with convex posterior border (p=0.001, 0.003 and 0.000, respectively). Conclusion: Oedema-like changes of the suprapatellar fat pad seen at knee MRIs are correlated with the configuration of the fat pad, but are rarely associated with anterior knee pain.

Does Hepatic Steatosis Influence the Detection Rate of Metastases in the Hepatobiliary Phase of Gadoxetic Acid-Enhanced MRI?

The aim of this exploratory study was to evaluate the influence of hepatic steatosis on the detection rate of metastases in gadoxetic acid-enhanced liver magnetic resonance imaging (MRI). A total of 50 patients who underwent gadoxetic acid-enhanced MRI (unenhanced T1w in- and opposed-phase, T2w fat sat, unenhanced 3D-T1w fat sat and 3-phase dynamic contrast-enhanced (uDP), 3D-T1w fat sat hepatobiliary phase (HP)) were retrospectively included. Two blinded observers (O1/O2) independently assessed the images to determine the detection rate in uDP and HP. The hepatic signal fat fraction (HSFF) was determined as the relative signal intensity reduction in liver parenchyma from in- to opposed-phase images. A total of 451 liver metastases were detected (O1/O2, n = 447/411). O1/O2 detected 10.9%/9.3% of lesions exclusively in uDP and 20.2%/15.5% exclusively in HP. Lesions detected exclusively in uDP were significantly associated with a larger HSFF (area under curve (AUC) of receiver operating characteristic (ROC) analysis, 0.93; p < 0.001; cutoff, 41.5%). The exclusively HP-positive lesions were significantly associated with a smaller diameter (ROC-AUC, 0.82; p < 0.001; cutoff, 5 mm) and a smaller HSFF (ROC-AUC, 0.61; p < 0.001; cutoff, 13.3%). Gadoxetic acid imaging has the advantage of detecting small occult metastatic liver lesions in the HP. However, using non-optimized standard fat-saturated 3D-T1w protocols, severe steatosis (HSFF > 30%) is a potential pitfall for the detection of metastases in HP.

Relative signal intensity on time-of-flight magnetic resonance angiography as a novel indicator of aggressive presentation of intracranial dural arteriovenous fistulas

Asymptomatic dural arteriovenous fistulas (DAVFs) with cortical venous reflux (CVR) are now more commonly encountered. However, patients with an incidental onset may have a less aggressive clinical course. It is desirable to explore methods and indicators to predict the clinical outcomes. This study investigates whether the relative signal intensity (rSI) of the draining vessels on the time-of-flight magnetic resonance angiography is related to clinical behavior in patients with intracranial DAVFs. We retrospectively reviewed 36 intracranial DAVFs. The patients were categorized as those with either aggressive-presentation or non-aggressive-presentation (n = 16 and 20, respectively). The rSIs of the shunt points, affected sinuses, and veins with CVR were compared between the two groups. The two groups were not significantly different in terms of rSIs of the shunt points and affected sinuses (p = 0.37 and 0.41, respectively). However, a significant positive correlation was observed in the rSI of the veins with CVR between the aggressive and non-aggressive behavior groups (p < 0.0001). The rSI of the veins with CVR could serve as a reliable indicator of aggressive behavior in intracranial DAVFs, and its optimal cutoff value was 1.63 with high sensitivity and specificity for predicting aggressive behavior (area under the curve, 0.909).

Lung MRI to predict lack of response to treatment in interstitial lung disease: initial observations on SSFSE/PROPELLER T2 mismatch

BackgroundHigh-resolution chest computed tomography (HRCT) signs of interstitial lung disease (ILD) are varied, some corresponding to irreparable parenchymal destruction and fibrosis, others representing potentially reversible changes, such as fine reticulation and ground-glass opacities (GGO). GGO frequently correspond to sites of active inflammation that may be responsive to steroids or immunosuppressive agents, but they might also represent intralobular interstitial fibrosis not resolved by current HRCT technique. Our aim was to investigate the ability of lung MRI to predict treatment response in individuals with ILD presenting with predominant GGO.MethodsIn this prospective cohort, 15 participants (4 male and 11 female) aged 38–84 years, presenting with ILD manifested as predominant GGO and referred for a new treatment regimen with a systemic glucocorticoid and/or an immunosuppressive agent, underwent 1.5 T lung MRI with breath-hold (SSFSE) and respiratory-gated (PROPELLER) T2-weighted pulse sequences, and with dynamic contrast-enhanced fat-suppressed T1-weighted pulse sequence (LAVA). Relative signal intensity on T2-weighted images and relative enhancement of lung lesions were compared to functional response in a dichotomous fashion (response versus non-response) with t test for independent samples. SSFSE/PROPELLER T2 mismatch was compared to response with Fisher’s exact test. Inter-rater agreement was evaluated with Cohen’s kappa coefficient. The primary endpoint for response was a greater than 10% increase in forced vital capacity in 10 weeks.ResultsResponders (4/15, 27%) and non-responders (11/15, 73%) showed similar relative signal intensity on T2-weighted images and relative enhancement measurements. SSFSE/PROPELLER T2 mismatch was able to discriminate responders from non-responders in 12 of 15 participants (80% accuracy, p = 0.026) for readers 1 and 2, and in 13 of 15 participants (87% accuracy, p = 0.011) for reader 3, with inter-rater agreement of 87% between readers 1 and 2 (Cohen’s kappa coefficient of 0.732) and 93% between readers 1/2 and 3 (Cohen’s kappa coefficient of 0.865).ConclusionsSSFSE-PROPELLER T2 mismatch was predictive of lack of response to treatment in this small group of ILD patients presenting with predominant GGO at HRCT.Key PointSSFSE/PROPELLER T2 mismatch may help predict lack of response to anti-inflammatory/immunosuppressive treatment in interstitial lung disease, with high accuracy and high inter-rater agreement.

GEOPHYSICAL MONITORING OF TECHNOGENIC HAZARDS ON ANTHROPOGENIC SOILS

Rock stability estimation tasks on anthropogenic soils require both preliminary survey and on-going real-time monitoring providing alerts on possible cave-in threats. Using VLF monitoring data incorporated into software-hardware geodynamical processes automated surveillance system allows to accomplish that task. Authors describe a unique method, based on Earth’s natural pulsed electro-magnetic field (ENPEMF) recording and make conclusions on the efficiency of the solutions ap-plied for hazardous geodynamic processes monitoring on anthropogenic soils. The principle of the method is to distinguish spatial variations of ENPEMF signal against diurnal oscillations and tech-nogenic signals. Correlation between relative signal intensity and stress-strained state of the rocks is experimentally demonstrated.

The usefulness of chemical-shift magnetic resonance imaging for the evaluation of osteoid osteoma

Objective: The purpose of this study was to determine whether chemical-shift magnetic resonance imaging (MRI) could be useful in the diagnosis of osteoid osteoma when clinical and radiological tumor features are inconclusive. Materials and Methods: This retrospective study included 17 patients who underwent chemical-shift MRI for the evaluation of osteoid osteoma. For all patients, two musculoskeletal radiologists independently recorded signal intensities on in-phase and out-of-phase images in the nidus of the tumor, in abnormal-intensity bone marrow surrounding the lesion, and in normal-appearing bone marrow. For each region, relative signal intensity ratios were calculated by dividing out-of-phase by in-phase values. Relative ratios > 1 were considered indicative of neoplastic lesions. Statistical analysis was carried out to analyze the sample. Inter-observer and intra-observer agreement for each imaging method were assessed using intraclass correlation coefficients according to the Fleiss method and a value > 0.65 was considered to indicate substantial agreement. Results: The mean relative signal intensity ratios were 1.2 (range, 0.9-1.4) for the nidus and 0.35 (range, 0.11-0.66) for the surrounding tissue; these values differed significantly from the relative signal-intensity ratios for normal-appearing bone marrow (p < 0.05). Conclusion: Chemical-shift MRI is useful for the diagnosis and evaluation of osteoid osteoma.

In vivo MRI detection of atherosclerosis in ApoE-deficient mice by using tenascin-C-targeted USPIO

Background Atherosclerosis is the main cause of cardiovascular and cerebrovascular diseases. Non-invasive molecular imaging to detect and characterize the plaques is essential for reducing life-threatening cardiovascular events. Purpose To investigate the possibility of the anti-tenascin-C-USPIO specific probe as a molecular marker of atherosclerotic plaques detected by 7.0-T magnetic resonance imaging (MRI). Material and Methods Twenty ApoE-/- mice fed with a high fat diet were used for detecting the aorta arch atherosclerotic plaques by 7.0-T MRI at 16 and 24 weeks. Ten mice in the targeted group were injected with anti-tenascin-C-USPIO and another ten in the control group were injected with pure USPIO (n = 5 each time point in each group). Histopathologic examination was used to evaluate the plaques and immunohistochemistry analysis was used to compare tenascin-C expression. Results The relative signal intensity (rSI) changes of the targeted group decreased more than those of the control group (16 weeks: −15.65 ± 0.78% vs. −3.43 ± 2.57%; 24 weeks: −26.38 ± 1.54% vs. −11.12 ± 1.60%, respectively; P < 0.05). Histopathological analyses demonstrated visible atherosclerotic plaques formation and development over time from 16 weeks to 24 weeks. Tenascin-C expression of the plaques at 24 weeks was higher than that at 16 weeks (0.22 ± 0.04 vs. 0.13 ± 0.02, P < 0.05). The MR images correlated well with the progression of atherosclerotic plaques. Conclusion Tenascin-C expression increased with the progression of atherosclerosis. Anti-tenascin-C-USPIO could provide a useful molecular imaging tool for detecting and monitoring atherosclerotic plaques by MRI.