Distribution of Hyperpolarized Xenon in the Brain Following Sensory Stimulation: Preliminary MRI Findings

In hyperpolarized xenon magnetic resonance imaging (HP 129Xe MRI), the inhaled spin-1/2 isotope of xenon gas is used to generate the MR signal. Because hyperpolarized xenon is an MR signal source with properties very different from those generated from water-protons, HP 129Xe MRI may yield structural and functional information not detectable by conventional proton-based MRI methods. Here we demonstrate the differential distribution of HP 129Xe in the cerebral cortex of the rat following a pain stimulus evoked in the animal's forepaw. Areas of higher HP 129Xe signal corresponded to those areas previously demonstrated by conventional functional MRI (fMRI) methods as being activated by a forepaw pain stimulus. The percent increase in HP 129Xe signal over baseline was 13–28%, and was detectable with a single set of pre and post stimulus images. Recent innovations in the production of highly polarized 129Xe should make feasible the emergence of HP 129Xe MRI as a viable adjunct method to conventional MRI for the study of brain function and disease

Temporal evolution of susceptibility artifacts from coiled aneurysms on MR angiography: an in vivo canine study

BACKGROUND AND PURPOSE: Intracranial aneurysms treated by coiling have a risk for recurrence, requiring surveillance imaging. MRA has emerged as an attractive technique for postcoiling aneurysm imaging. Previous research has evaluated MR imaging artifacts of the coil mass in vitro. Our aim in this study was to evaluate MR imaging artifacts of coiled aneurysms in vivo with time. MATERIALS AND METHODS: Four sidewall aneurysms were created in each of 4 dogs. Aneurysms were embolized receiving only 1 type of coils. After embolization, the animals were transferred to MR imaging, which included axial 3D TOF MRA (TEs, 3.5, 5, and 6.9 ms), phase-contrast MRA, and coronal CE-MRA. MR imaging studies were repeated at 1, 4, 6, 8, 14, and 28 weeks. We calculated an OEF: OEF = V(A)/V(CM), where the numerator represents the volume of the MR imaging artifacts and the denominator is the true volume of the coil mass measured by 3D RA. RESULTS: OEFs were largest immediately after embolization and showed a gradual decay until approximately 4 weeks, when there was stabilization of the size of the artifacts. By 4 weeks, there was mild coil compaction (average coil mass volume decrease of 7.8%); however, the OEFs decreased by 25% after 4 weeks (P \u3c .001). CONCLUSIONS: MR imaging susceptibility artifacts change with time, being maximal in the postembolization setting and decaying until 4 weeks. The clinical implications of this study are that baseline MRA for comparison with future imaging should be acquired at a minimum of 1 week after the procedure

Temporal artery biopsy for giant cell arteritisv : retrospective audit

Objectives Temporal artery biopsy (TAB) is performed in suspected cases of sight-threatening giant cell arteritis (GCA). We aimed to determine the feasibility of TAB in patients who are suspected of having GCA. Design, setting and participants A retrospective audit of all patients undergoing TAB at a single teaching hospital between 2005 and 2011, identified from the histopathology database. Main outcome measures (1) Clinical profile and biochemical criteria associated with positive histology. (2) Proportion of negative histology patients who were commenced on steroid therapy. Results One hundred and fifty-three TAB were performed (mean age 70.8 years, men:women = 3:2, 110 Caucasian: 43 Asian). Thirty-two biopsies were positive for GCA and 121 were negative. In total, 68 (61%) of 112 negative TAB patients were clinically diagnosed with GCA despite histological findings (P < 0.001). Nine out of 153 biopsies were non-arterial. Histologically positive TAB patients were of higher mean age (77.1 [95% CI 74.5–79.7] versus 69.1 [95% CI 66.7–71.6]; P < 0.001) and had a higher erythrocyte sedimentation rate (ESR) (60 [95% CI 46.1–73.9] versus 39.8 [95% CI 34.2–45.3]; P < 0.01)] than those with negative histology. Conclusions Raised ESR and higher age may be the most useful indicators of GCA. Many histologically negative individuals were nevertheless clinically diagnosed and managed as GCA