Initial experience with dual-layer detector spectral CT for diagnosis of blood or contrast after endovascular treatment for ischemic stroke.

PURPOSE: To determine whether spectral detector CT (SDCT) with a plain non-enhanced monochromatic CT, a water-weighted image after iodine removal, an iodine map, and Mono energetic images changes the diagnosis and classification of intracranial hemorrhage based on single energy CT after endovascular treatment (EVT) for ischemic stroke. METHODS: Two readers evaluated single energy and SD CT data collected from 63 patients within one week after EVT. They diagnosed ICH or contrast staining, and graded ICH according to the Heidelberg and Safe Implementation of Thrombolysis in Stroke-Monitoring Study (SITS-MOST) classification. Differences in diagnosis between single energy and SD CT were tested with Pearson's chi-squared test. Diagnostic values of single energy CT were calculated. Interrater agreement was based on Cohen's Kappa. RESULTS: When spectral data were added to single energy CT, the diagnosis of ICH changed in 8 CT scans (13%): in 4, the diagnosis of ICH was rejected and in 4, initially undetected ICH was diagnosed. In an additional 3 patients, the ICH grade was modified. CT alone had 88% sensitivity, 87% specificity, 88% positive diagnostic value, 87% negative diagnostic value, and 87% overall accuracy for ICH compared to SDCT. Interreader agreement on the presence of ICH was 0.84 (95% CI 0.51-0.86) for spectral CT and 0.84 (95% CI 0.73-0.97) for single energy CT. CONCLUSION: SD CT after endovascular treatment contributes to the distinction between intracranial hemorrhage and contrast staining.

Lumbar spinal canal dimensions measured intraoperatively after decompression are not properly rendered on early postoperative MRI.

BACKGROUND: In cases of lumbar spinal stenosis (LSS) treated with surgical decompression, a postoperative magnetic resonance imaging (MRI) is sometimes required. In the experience of the investigators of this study, the obtained decompression observed on early postoperative MRI tends to be disappointing compared to the decompression achieved intraoperatively. This raises the question of whether the early postoperative MRI, performed after lumbar decompression, is a fair representation of the 'real' decompression. This study investigated the correlation between intraoperative and postoperative measurements of the lumbar spinal canal. METHOD: Twenty patients with LSS underwent surgical decompression on a single level. The orthopaedic surgeon performed direct intraoperative measurements of width, length and height of the spinal canal. Preoperative supine MR images and postoperative prone and supine MR images were acquired. Two radiologists (R.B. and M.G.) measured width, length and height of the spinal canal on the preoperative and postoperative MRIs. Intraoperative measurements were compared to measurements on postoperative MRI in prone position (thus reproducing the intraoperative situation) to avoid positioning bias. Preoperative and postoperative measurements on MR images were also compared. In addition to this, postoperative measurements on supine and prone MR images were also compared. RESULTS: Interobserver reliability for MRI measurements by both radiologists was generally excellent (intraclass correlation coefficients ≥0.71). The postoperative spinal canal dimensions improved on both prone and supine MRI compared to the preoperative imaging (P < 0.05). Intraoperatively measured dimensions demonstrated a significantly greater height (difference 2.8 ± 3.3 [R.B.] and 1.9 ± 3.7 [M.G.]) and greater width (difference 2.1 ± 3.2 [R.B.] and 2.5 ± 2.7 [M.G.]) compared to postoperative MRI in the prone position (P < 0.05). Postoperative dural sac height was greater on the supine MRI compared to the prone MRI (P < 0.05). CONCLUSIONS: Surgical decompression of the spinal canal effectively decreases the compression of the dural sac. However, early postoperative MRI after lumbar decompression does not adequately represent the decompression achieved intraoperatively.

A feedback protocol improves the diagnostic performance of MR arthrography by experienced musculoskeletal radiologists in patients with traumatic anterior shoulder instability.

PURPOSE: To prospectively evaluate the diagnostic performance of magnetic-resonance-arthrography (MRA) by experienced musculoskeletal radiologists in patients with traumatic-anterior-shoulder-instability (TASI), after feedback protocol execution. MATERIALS AND METHODS: Forty-five surgically confirmed MRA's were used to enhance personal feedback, to discuss differences in outcome between MRA assessment and surgical findings and to fine-tune definition interpretation agreement of 7 different TASI-related lesions, between experienced musculoskeletal radiologists and experienced orthopaedic shoulder surgeons. After execution of the feedback protocol 20 new, surgically confirmed, MRA's were assessed by 2 experienced musculoskeletal radiologists using a seven-lesion standardized scoring form. Kappa coefficients, sensitivity, specificity, and differences in percentage agreement or correct diagnosis (p-value, McNemar's test) were calculated per lesion and overall per 7 lesion types to assess whether diagnostic reproducibility and accuracy was improved. RESULTS: Per 7 lesion types, the overall kappa and percentage of agreement, between the 2 radiologists, were dramatically increased in comparison with our former study (k=0.81 versus k=0.48 and 90.7% versus 78.2%, respectively). The overall sensitivity of radiologist 1 increased from 45.9% to 87.8%, the overall sensitivity of radiologist 2 increased from 63.5% to 79.6% and the overall specificity of radiologist 2 increased from 80.1% to 85.7%. Furthermore, the overall percentage of correct diagnosis of both radiologist was also exceedingly higher (85.7% and 83.6%) compared to our former study (74.4% and 74.8%). CONCLUSION: The implementation of our feedback protocol dramatically improved the reproducibility and accuracy of high field MRA by experienced musculoskeletal radiologist in patients with traumatic anterior shoulder instability.

Björk-Shiley convexoconcave valves: susceptibility artifacts at brain MR imaging and mechanical valve fractures.

PURPOSE: To assess the relationship between heart valve history and susceptibility artifacts at magnetic resonance (MR) imaging of the brain in patients with Björk-Shiley convexoconcave (BSCC) valves. MATERIALS AND METHODS: MR images of the brain were obtained in 58 patients with prosthetic heart valves: 20 patients had BSCC valve replacements, and 38 had other types of heart valves. Two experienced neuroradiologists determined the presence or absence of susceptibility artifacts in a consensus reading. Artifacts were defined as characteristic black spots that were visible on T2*-weighted gradient-echo MR images. The statuses of the 20 explanted BSCC valves-specifically, whether they were intact or had an outlet strut fracture (OSF) or a single-leg fracture (SLF)-had been determined earlier. Number of artifacts seen at brain MR imaging was correlated with explanted valve status, and differences were analyzed with nonparametric statistical tests. RESULTS: Significantly more patients with BSCC valves (17 [85%] of 20 patients) than patients with other types of prosthetic valves (18 [47%] of 38 patients) had susceptibility artifacts at MR imaging (P =.005). BSCC valve OSFs were associated with a significantly higher number of artifacts than were intact BSCC valves (P =.01). No significant relationship between SLF and number of artifacts was observed. CONCLUSION: Susceptibility artifacts at brain MR imaging are not restricted to patients with BSCC valves. These artifacts can be seen on images obtained in patients with various other types of fractured and intact prosthetic heart valves.

Black holes on MR images of the brain of patients with Björk-Shiley heart valves: additional observation in three cases.

We report the cases of three patients with Björk-Shiley convexo-concave heart valves with unusual black holes shown on cerebral MR images. For two patients, these findings were associated with fracture of the Björk-Shiley convexo-concave heart valve, and for the third, with worn surfaces on the heart valve. Susceptibility changes shown by MR imaging suggest the possibility that these black holes may be associated with microscopic metallic particles, although, the exact cause of these black holes remains undetermined.