Evaluating Permeability Surface-Area Product as a Measure of Blood-Brain Barrier Permeability in a Murine Model.

BACKGROUND AND PURPOSE: Permeability surface-area product has been suggested as a marker for BBB permeability with potential applications in clinical care and research. However, few studies have demonstrated its correlation with actual quantitative measurements of BBB permeability. Our aim was to demonstrate the correlation of quantitative permeability surface-area product and BBB permeability in a murine model by histologic confirmation. MATERIALS AND METHODS: Coronal MR imaging was performed on mice treated with mannitol (n = 6) for disruption of the BBB and controls treated with saline (n = 5). Permeability surface-area product was determined by ROI placement and was compared between saline- and mannitol-treated mice. Correlation was made with contrast-enhancement measurements and immunohistologic-stained sections of tripeptidyl peptidase-1 distribution in mice treated with mannitol and saline followed by injection of a viral vector containing the CLN2 gene, which directs production of tripeptidyl peptidase-1. RESULTS: Significantly increased permeability surface-area product was seen in mannitol- compared with saline-treated mice in the whole brain (P = .008), MCA territory (P = .014), and mixed vascular territories (P = .008). These findings were compared with contrast-enhancement measurements of BBB permeability and were correlated with immunohistologic-stained sections demonstrating BBB permeability to a large vector. CONCLUSIONS: Permeability surface-area product is increased in situations with known disruptions of the BBB, as evidenced by immunologic staining of large-vector passage through the BBB and concordance with contrast-enhancement measurements in a murine model. Quantitative permeability surface-area product has potential as an imaging marker of BBB permeability.

Novel microcatheters for selective intra-arterial injection of fluid in the rat brain.

BACKGROUND AND PURPOSE: The internal carotid artery (ICA) in the rat has a single extracranial branch, which supplies the muscles of mastication. The rat ICA also has multiple intracranial branches including (from proximal to distal): multiple small perforating arteries which supply the hypothalamus and the anterior choroidal artery which supplies the choroid plexus and part of the basal ganglia. At the ICA terminus, the vessel bifurcates into the anterior and middle cerebral arteries. The purpose of this study was to demonstrate selective injection of ICA branches in the rat. MATERIALS AND METHODS: Microcatheters (mucath1 and mucath2) were fabricated by plugging the tip of 169-mum outer diameter polyimide tubing and perforating the sidewalls. A 450-mum polydimethyl-siloxane cylinder was affixed to the distal tip of mucath2 but not mucath1. We evaluated the territory of mucath1 injection ex vivo using magnetization-prepared rapid acquisition of gradient echo MR imaging of brain specimens injected at necropsy. Territories of mucath1 and mucath2 injection were evaluated in vivo with dynamic susceptibility-weighted contrast-enhanced MR imaging. The territory of mucath2 also was evaluated in vivo with fused static microPET/T1 MR images performed after [(18)F] fluorodeoxyglucose ((18)FDG) injection. We evaluated additional catheterized and injected animals at 48 hours using physical examination, T2 MR images, and postmortem brain histologic specimens. RESULTS: Gadolinium-diethylene-triamine pentaacetic acid (Gd-DTPA) and (18)FDG injected through mucath1 selectively opacified the ipsilateral cerebral hemisphere, with no contralateral opacification. Gd-DTPA injected through mucath2 selectively opacified the territories of the hypothalamic perforating arteries, and anterior choroidal artery. There was no iatrogenic complication 48 hours after 20- to 25-minute injections performed with mucath1 or mucath2. CONCLUSIONS: We have developed 2 microcatheters which can be placed in the ICA for selective injection of its branches. One microcatheter selectively injects the ipsilateral cerebral hemisphere. The other selectively injects only the hypothalamus and lateral thalamus.

Observer variability and applicability of BI-RADS terminology for breast MR imaging: invasive carcinomas as focal masses.

OBJECTIVE: The purpose of this study was to assess whether the descriptive terminology and final assessment categories of the Breast Imaging Reporting and Data System (BI-RADS) lexicon can be used for breast carcinomas detected on MR imaging and to assess the inter- and intraobserver variabilities in the use of the descriptors and final assessment categories. MATERIALS AND METHODS: In 82 patients, 101 masses, including 68 infiltrating carcinomas and 33 benign lesions, were interpreted independently by four radiologists and described by BI-RADS terminology with respect to mass shape and margin and BI-RADS final assessment categories. The enhancement pattern of the mass was also reported. In addition, two radiologists interpreted each case twice to evaluate intraobserver variability. The final case set for analysis was the 68 infiltrating carcinomas. RESULTS: Most of the infiltrating carcinomas were described as irregular, spiculated, and heterogeneously enhancing masses. The final impression of the 68 carcinomas was BI-RADS category 5 (highly suggestive of malignancy) in 41 (61%), category 4 (suspicious abnormality) in 24 (35%), and category 3 (probably benign) in three (4%). Enhancement pattern was heterogeneous in 40 (59%), homogeneous in 14 (21%), and rim in 14 (21%). Interobserver agreement was moderate for mass margin, shape, enhancement, and final assessment category. CONCLUSION: This study suggests that the mammographic BI-RADS lexicon with some modifications may be applied to describe the features of infiltrating carcinoma seen on breast MR imaging.