Magnetic resonance imaging-related programmable ventriculoperitoneal shunt valve setting changes occur often.

PURPOSE: Patients with programmable ventriculoperitoneal (VP) shunt valves undergo multiple skull radiographs to evaluate for setting changes resulting from MRI. Our purpose was to determine the rates of inadvertent, MRI-related, programmable VP shunt valve setting changes. MATERIALS AND METHODS: In this retrospective cohort with a study period of January 2015-December 2018, we reviewed the pre- and post-MRI skull radiographs of patients with programmable VP shunts and collected the following data: Demographics, commercial type of the valve used, magnetic field strength of the MRI device used, and whether a setting change occurred. We used the chi-square test to identify variables associated with valve setting change. RESULTS: We identified 210 MRI exposure events in 156 patients, and an MRI-related valve setting change rate of 56.7%. The setting change rate was significantly higher with higher magnetic field strength (p = 0.03), and with Medtronic Strata™ valves compared to Codman Hakim™ valves (p < 0.0001). CONCLUSION: Inadvertent, MRI-related shunt valve setting changes are frequent with valves that lack a locking mechanism. Therefore, we suggest that when feasible, the clinicians could opt to manually reprogram the valves after the MRI to the preferred setting without the need for pre- and post-MRI radiographs. We believe that this protocol modification could help reduce ionizing radiation exposure and cost. Manufacturers may consider incorporating locking mechanisms into the design of such devices in order to reduce the unintended setting change rates.

Brain magnetic resonance imaging at 3 Tesla using BLADE compared with standard rectilinear data sampling.

OBJECTIVES: We sought to evaluate Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER; BLADE) data acquisition in comparison with standard k-space sampling techniques for axial and sagittal brain imaging at 3 T regarding imaging artifacts. MATERIAL AND METHODS: Forty patients who gave consent were included in a prospective comparison of standard and PROPELLER (BLADE) k-space sampling techniques. All examinations were performed at 3 T with comparison of standard T2-weighted fluid-attenuated inversion recovery (FLAIR) to PROPELLER T2-weighted FLAIR in the axial image orientation and standard T1-weighted gradient echo to PROPELLER T1-weighted FLAIR in the sagittal image orientation. Imaging protocols were matched for spatial resolution, with data evaluation performed by 2 experienced neuroradiologists. Image data were compared regarding various image artifacts and overall image quality. Reader agreement was assessed by Cohen's kappa statistics. RESULTS: PROPELLER T2-weighted axial data acquisition showed significantly less pulsation and Gibb's artifacts than the standard T2-weighted scan. Even without motion correction, the frequency of ghosting (motion) artifacts was substantially lower in the PROPELLER T2-weighted data and readers concordantly (kappa = 1) rated PROPELLER as better than or equal to the standard T2-weighted scan in the majority of cases (95%; P < 0.0001). In the comparison of sagittal T1-weighted data sets, readers showed only fair agreement (kappa = 0.24) and noted consistent wrap artifacts in PROPELLER T1-weighted FLAIR. CONCLUSION: PROPELLER (BLADE) brain magnetic resonance imaging is also applicable at 3 T. In addition to minimizing motion artifacts, the PROPELLER acquisition scheme reduces other magnetic resonance artifacts that would otherwise degrade scan quality.

T1-weighted imaging of the brain at 3 tesla using a 2-dimensional spoiled gradient echo technique.

RATIONALE AND OBJECTIVES: The objective of this study was to evaluate a 2-dimensional spoiled gradient echo (GRE) imaging approach using a very short in-phase TE for routine T1-weighted imaging of the brain at 3 T. MATERIALS AND METHODS: Patient examinations were compared from a 3 T magnetic resonance (MR) unit located immediately adjacent to a similarly equipped 1.5 T unit. Pre- and postcontrast T1-weighted images were evaluated and compared at 1.5 versus 3 T with a 2-dimensional (2-D) spin echo sequence used at 1.5 T and a 2-D GRE sequence at 3 T. The 2 MR systems used are from the same vendor, use similar 8-channel coils, and use identical gradients. The T1-weighted GRE sequence, used at 3 T, relies on a short TE (2.4 ms) to limit flow-related and susceptibility artifacts. Region-of-interest analysis was performed on 16 different sagittal patient examinations at both field strengths (32 total) and similarly on 10 different pre- and postcontrast axial examinations (40 total). Four blinded neuroradiologists also evaluated these studies. RESULTS: Using an off-midline sagittal slice depicting the caudate nucleus (signal-to-noise ratio [SNR] 163 +/- 28 vs. 70 +/- 7, 3 T vs. 1.5 T) and corona radiata (SNR 214 +/- 35 vs. 82 +/- 10), 3 T markedly outperformed 1.5 T in both SNR and contrast-to-noise ratio (CNR) (51 +/- 14 vs. 12 +/- 5). On axial imaging, despite a reduction in slice thickness (5 to 3 mm) and scan time (5 to 1 minute), there was no significant difference pre- or postcontrast in SNR and CNR comparing 3 and 1.5 T. On blinded film review, 3 T performed slightly better on sagittal scans than 1.5 T in regard to motion artifacts (reduced), gray-white matter differentiation, and overall image quality. On axial scans, 3 T performed markedly better in all 3 categories both pre- and postcontrast. In regard to overall image quality, 3 T was preferred 9:2 precontrast and 4:1 postcontrast. CONCLUSIONS: High-quality, thin-section (3-mm) T1-weighted imaging can be readily performed at 3 T using a short TE 2-D GRE technique. This approach offers superior SNR and CNR with reduced motion artifacts and scan time as compared with imaging at 1.5 T and is advocated for routine brain imaging at 3 T. It is robust (used in over 1500 patients to date) and does not experience significant specific absorption ratio limitations, poor tissue contrast, or accentuated motion artifacts like encountered with spin echo T1-weighted imaging at 3 T.

Methotrexate-induced toxic leukoencephalopathy.

Drug-induced leukoencephalopathy is a devastating adverse event that can cause significant morbidity and mortality. Risk factors include advanced age, administration of certain chemotherapies, presence of an Ommaya device, central nervous system malignancy, and most important, exposure to cranial radiation. A 73-year-old woman developed leukoencephalopathy 2 months after her last dose of intraventricular methotrexate. Although leukoencephalopathy is a severe adverse effect of the agent, her case is different because it occurred without prior exposure to cranial radiation.