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Background: Recent advances in high-resolution (HR) magnetic resonance angiography (MRA) using ultrahigh-field systems enable direct visualization of the lenticulostriate arteries (LSAs), which had been hardly achieved by conventional MRA. Hence, by using HR-MRA at 7 T, we attempted to assess occlusive changes in the LSAs in patients with LSA territorial infarcts. Methods: We prospectively examined 34 consecutive patients with acute ischemic stroke in the LSA territory using a 7 T scanner. We measured the lengths of the relevant LSAs on HR-MRA and the diameters/volume of the infarcts and compared these between the patients with/without occlusive changes in the LSAs. Results: On HR-MRA, occlusion of the LSAs was observed in 19 (59%) of 32 patients who were eligible for the analyses. The curved/straight lengths of the LSAs in the patients with LSA occlusion (23.1-31.1/17.8-24.3 mm) were significantly shorter than in those without apparent LSA occlusion (25.8-39.5/24.0-30.4 mm) (P ¼ 0.027/0.003). The anteroposterior/ superoinferior diameters of the infarcts were significantly larger in the occluded-LSA group (14.5-21.4/14.9-22.2 mm) than in the intact-LSA group (

Objectives Tumor interiors are never homogeneous and in vivo visualization of intratumoral heterogeneity would be an innovation that contributes to improved cancer therapy. But, conventional nuclear medicine tests have failed to visualize heterogeneity in vivo because of limited spatial resolution. Recently developed single photon emission computed tomographic (SPECT) scanners dedicated for small animal imaging are of interest due to their excellent spatial resolution of\1 mm, but few studies have focused on the evaluation of intratumoral heterogeneity. We investigated the optimal conditions related to high resolution imaging of heterogeneous tumor interiors using a small animal SPECT scanner. MethodsThe conditions related to SPECT/CT visualization of heterogeneous tumor interiors were investigated using phantoms with 111 In and simulations of actual small animal imaging. The optimal conditions obtained were validated by in vivo imaging of sarcoma 180-bearing mice. Results Larger number of counts must be obtained within limited acquisition time to visualize tumor heterogeneity in vivo in animal imaging, compared to cases that simply detect tumors. At an acquisition time of 30 min, better image quality was obtained with pinhole apertures diameter of 1.4 mm than of 1.0 mm. The obtained best spatial resolution was 1.3 mm, it was acceptable for our purpose, though a little worse than the best possible performance of the scanner (1.0 mm). Additionally, the reconstruction parameters, such as noise suppression, voxel size, and iteration/subset number, needed to be optimized under the limited conditions and were different from those found under the ideal condition. The minimal radioactivity concentration for visualization of heterogeneous tumor interiors was estimated to be as high as 0.2-0.5 MBq/mL. Liposomes containing 111 In met this requirement and were administered to tumor-bearing mice. SPECT imaging successfully showed heterogeneous 111 In distribution within the tumors in vivo with good spatial resolution. A threshold of 0.2 MBq/g for clear visualization of tumor heterogeneity was validated. Autoradiograms obtained ex vivo of excised tumors confirmed that the in vivo SPECT images accurately depicted the heterogeneous intratumoral accumulation of liposomes. Conclusion Intratumoral heterogeneity was successfully visualized under the optimized conditions using a SPECT/ CT scanner.

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