Comparison of End-Expiration Versus End-Inspiration Breath-Holds With Respect to Respiratory Motion Artifacts on T1-Weighted Abdominal MRI.

OBJECTIVE. The purpose of this study was to compare respiratory motion artifact and diagnostic image quality between end-inspiration and end-expiration breath-holding techniques on unenhanced and contrast-enhanced axial T1-weighted MRI of the liver. MATERIALS AND METHODS. This retrospective observational study included 50 consecutive subjects undergoing axial T1-weighted liver MRI, with unenhanced images acquired with both end-inspiration and end-expiration breath-holding techniques, and with contrast-enhanced images acquired for 47 of the subjects with either the end-inspiration or the end-expiration breath-holding technique. Three radiologists performed blinded independent evaluations of each unenhanced sequence, contrast-enhanced sequence, and subtraction (contrast-enhanced minus unenhanced) image, using a scale ranging from 1 point (denoting nondiagnostic imaging) to 5 points (denoting no artifacts). Blinded side-by-side assessment of each pair of unenhanced sequences was also performed. Two-tailed Wilcoxon signed rank and Wilcoxon rank sum tests were used to assess statistical significance. RESULTS. A significant improvement in motion scores was noted for sequences acquired in end-expiration, compared with those acquired in end-inspiration, for unenhanced sequences (mean, 3.35 vs 2.80; p < 0.00001), contrast-enhanced sequences (mean, 4.02 vs 3.46; p = 0.0003), and subtraction images (mean, 3.67 vs 2.41; p < 0.00001). Severe degradation of image quality or nondiagnostic image quality was noted for 15% of unenhanced images (23/150), 0% of contrast-enhanced images, and 8% (5/63) of subtraction images acquired on end-expiration, whereas it was noted for 36% (54/150) of unenhanced images, 13% (10/78) of contrast-enhanced images, and 59% (46/78) of subtraction images acquired on end-inspiration. When side-by-side assessment of paired unenhanced sequences was performed, images acquired in end-expiration were significantly favored in 59% of paired sequences (88/150) (p < 0.00001), and no difference between images acquired with both breath-hold techniques was noted for 21% (32/150) of paired sequences. CONCLUSION. The end-expiration breath-holding technique leads to significant decreases in respiratory motion artifacts, compared with the end-inspiration technique, on unenhanced and contrast-enhanced T1-weighted liver MRI.

Free-breathing pediatric chest MRI: Performance of self-navigated golden-angle ordered conical ultrashort echo time acquisition.

PURPOSE: To assess the feasibility and performance of conical k-space trajectory free-breathing ultrashort echo time (UTE) chest magnetic resonance imaging (MRI) versus four-dimensional (4D) flow and effects of 50% data subsampling and soft-gated motion correction. MATERIALS AND METHODS: Thirty-two consecutive children who underwent both 4D flow and UTE ferumoxytol-enhanced chest MR (mean age: 5.4 years, range: 6 days to 15.7 years) in one 3T exam were recruited. From UTE k-space data, three image sets were reconstructed: 1) one with all data, 2) one using the first 50% of data, and 3) a final set with soft-gating motion correction, leveraging the signal magnitude immediately after each excitation. Two radiologists in blinded fashion independently scored image quality of anatomical landmarks on a 5-point scale. Ratings were compared using Wilcoxon rank-sum, Wilcoxon signed-ranks, and Kruskal-Wallis tests. Interobserver agreement was assessed with the intraclass correlation coefficient (ICC). RESULTS: For fully sampled UTE, mean scores for all structures were ≥4 (good-excellent). Full UTE surpassed 4D flow for lungs and airways (P < 0.001), with similar pulmonary artery (PA) quality (P = 0.62). 50% subsampling only slightly degraded all landmarks (P < 0.001), as did motion correction. Subsegmental PA visualization was possible in >93% scans for all techniques (P = 0.27). Interobserver agreement was excellent for combined scores (ICC = 0.83). CONCLUSION: High-quality free-breathing conical UTE chest MR is feasible, surpassing 4D flow for lungs and airways, with equivalent PA visualization. Data subsampling only mildly degraded images, favoring lesser scan times. Soft-gating motion correction overall did not improve image quality. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:200-209.

Susceptibility weighted imaging depicts retinal hemorrhages in abusive head trauma.

INTRODUCTION: This study aims to evaluate the capability of magnetic resonance imaging (MRI) susceptibility weighted images (SWI) in depicting retinal hemorrhages (RH) in abusive head trauma (AHT) compared to the gold standard dilated fundus exam (DFE). METHODS: This is a retrospective, single institution, observational study on 28 patients with suspected AHT, who had a DFE and also underwent brain MRI-SWI as part of routine diagnostic protocol. Main outcome measures involved evaluation of patients to determine whether the RH could be identified on standard and high-resolution SWI sequences. RESULTS: Of the 21 subjects with RH on DFE, 13 (62%) were identified by using a standard SWI sequence performed as part of brain MRI protocols. Of the 15 patients who also underwent an orbits SWI protocol, 12 (80%) were positive for RH. None of the seven patients without RH on of DFE had RH on either standard or high-resolution SWI. Compared with DFE, the MRI standard protocol showed a sensitivity of 75% which increased to 83% for the orbits SWI protocol. CONCLUSIONS: Our study suggests the usefulness of a tailored high-resolution orbits protocol to detect RH in AHT.

Imaging findings in primary central nervous system vasculitis.

Primary central nervous system vasculitis (PCNSV) is a rare primary vasculitis limited to the brain and spinal cord. It can affect any age group, but has a predilection for subjects aged 40 to 60 years without clear gender predominance. Clinical manifestations are nonspecific, including headache, non-focal neurological features and, less frequently, focal neurological signs. Brain biopsy is the diagnostic gold standard, but may be falsely negative when unaffected tissue is sampled. In addition, brain biopsy carries a small but significant risk of serious complications. Imaging procedures are a key part of the workup of PCNSV patients. They can be used to document the extent and type of lesions, to gauge response to treatment, and sometimes as surrogates for brain biopsy. Magnetic resonance is extremely sensitive but non-specific. The most common findings are multiple bilateral ischaemic lesions often involving white and grey matter. Conventional or magnetic resonance angiography (MRA) typically shows segmental narrowing and dilation in multiple cerebral arteries. However, atypical findings have also been described both with magnetic resonance and angiography. This review discusses the state-of-the-art of current imaging techniques in the workup of PCNSV patients and highlights future prospects.

Predictors of Cervical Vertebral and Carotid Artery Dissection During Blunt Trauma: Experience From a Level 1 Trauma Center.

BACKGROUND: The current data available to identify the factors associated with vertebral and carotid artery dissection in the trauma setting are conflicting, and further research is needed to accurately assess these predictors. METHODS: The data from 950 patients who had undergone neck computed tomography angiography (CTA) at a level 1 trauma center were analyzed. Of the 950 patients, 435 were included who had undergone neck CTA for blunt traumatic injuries. The mechanism of injury was classified as high or low impact according to the hospital criteria for trauma. Positive neurological signs included altered mental status (Glasgow coma scale score ≤15 than baseline) or focal neurological deficits. Fractures and dissections were radiologically confirmed. Multivariable logistic regression software was used to analyze the data. RESULTS: Of the 435 patients, 236 (54.25%) had experienced high-impact injuries, 124 (28.51%) had vertebral fractures (including 63 displaced fractures [50.81%]), and 180 (41.38%) had had positive neurological signs on presentation. Of the 435 patients, cervical carotid artery injury had been diagnosed in 9 (2.07%), and 18 patients (4.14%) had had a cervical vertebral artery injury (VAI). Carotid artery injuries did not have significant associations with positive neurological signs, age, sex, mechanism of injury, or vertebral fracture (P > 0.05 for all). Positive neurological signs and vertebral fractures were significant predictors for VAI (odds ratio, 3.19; P < 0.05; odds ratio, 9.81; P < 0.001, respectively). Age, sex, mechanism of injury, and displacement of the vertebral fracture were not significant predictors for VAI (P > 0.05 for all). CONCLUSIONS: Positive neurological signs and the presence of cervical vertebral fractures are significant predictors for VAI. All trauma patients with cervical spine fractures and/or positive neurological findings should be considered for surveillance imaging with neck CTA and/or magnetic resonance angiography for vascular injury screening.

Relation of Velocity-Time Integral of the Left Ventricular Outflow Tract to that of the Descending Thoracic Aorta and Usefulness of a Fixed Ratio for Internal Validation.

Measurement of left ventricular outflow tract velocity-time integral (LVOT VTI) is technician-, instrument-, and reader-dependent; variability is more common for pulsed-wave Doppler than continuous-wave Doppler. We hypothesize that in a population with normal cardiac structure and function, LVOT VTI is higher than VTI of the descending thoracic aorta (DTA) and this relation may be used clinically to validate the former. Furthermore, the DTA VTI could also be used to estimate LVOT. We retrospectively compared the LVOT VTI against VTI measured from DTA, abdominal aorta, and pulmonary artery among 108 healthy subjects. The ratio of LVOT VTI (n = 108) to DTA VTI (n = 108) was 1.27. There was a difference of 19.6% between LVOT VTI and DTA VTI with the former being higher. This percentage decrease in VTI from LVOT VTI to abdominal aortic (AA) VTI was directly proportional to the LVOT VTI. Similarly, there was a difference of 23.4% in the VTI values obtained from DTA and abdominal aorta. Moreover, there was a decrease of 40.4% when LVOT VTI was compared against AA VTI. The ratio of LVOT VTI to pulmonary VTI was 1.19. VTI values decrease in a linear fashion from the LVOT to abdominal aorta likely because of progressive decrease in circulating volume, and this change is not obscured by diminishing aortic diameter. Any deviation from this relation should be treated as abnormal and should prompt further investigation. Our findings support routine measurement of DTA VTI in clinical practice.