Voxel-specific brain arterial input functions from dynamic susceptibility contrast MRI and blind deconvolution in a group of healthy males.

BACKGROUND: Arterial input functions may differ between brain regions due to delay and dispersion effects in the vascular supply network. Unless corrected for, these differences may degrade quantitative estimations of cerebral blood flow in dynamic susceptibility contrast magnetic resonance perfusion imaging (DSC-MRI). PURPOSE: To investigate in a healthy population (n=44) the properties of voxel-specific arterial input functions that were obtained using a recently published blind estimation approach. MATERIAL AND METHODS: The voxel-specific arterial input functions were qualitatively and quantitatively assessed, through visual inspection or by comparing time-to-peak (delays) and peak amplitude (dispersion) values between eight regions of the brain. Furthermore, they were compared to arterial input functions selected manually in the middle cerebral artery (MCA), where normally no delay or dispersion of the contrast agent was expected. RESULTS: The estimated voxel-specific arterial input functions varied between brain regions. Differences in delays and dispersion were larger within one brain region among all participants than between regions in one participant. A good correlation was typically found between the estimated voxel-specific arterial input functions and the manually selected arterial input functions in the MCA region. CONCLUSION: Given knowledge of neurovascular anatomy, the current blind approach seemingly produced reasonable estimates of voxel-specific arterial input functions. In addition to potentially reducing quantification errors in DSC-MRI, these user-independent voxel-specific arterial input functions could be useful for visualizing abnormal blood supply patterns in patients.

Imaging of experimental rat gliomas using a clinical MR scanner.

BACKGROUND: Studies of brain tumor development in experimental animal models have to date mostly been based on post-mortem histological examinations. The use of magnetic resonance imaging (MRI) may provide a non-invasive technique for studying tumor growth and treatment effects in such animal models. However, most of these studies have been performed on purpose-dedicated small bore magnetic resonance (MR) systems, of high cost and limited availability. The purpose of this study was thus to obtain high-resolution images of experimental gliomas in the rat brain, using a clinical 1.5 T MR scanner. METHODS: Anesthesized rats bearing BT4C brain tumors were positioned into a specially designed immobilizing device, and a small circular coil was positioned onto the skulls. Two T1 weighted series were acquired before and after subcutaneous contrast injections. A T2 weighted series was also obtained. The rats were then sacrified, the brains removed, and the histological tumor volumes were compared to the volumes obtained on MRI. RESULTS: There were visible tumors in 10 of 13 animals scanned on MR. The rim of the tumors were visualized on T1 weighted series without contrast. On T1 images with contrast, the tumors were seen as high signal intensity areas. The T2 weighted images showed peritumoral edema. No necrosis or cystic parts of the tumors were detected. There was a consistency between the MR and the histology findings, showing a high degree of correlation between the two volume determination methods. CONCLUSIONS: High-resolution images of experimental rat gliomas can be obtained using a clinical MR scanner and a commercially available RF coil. This MRI technique may also be expanded to extraneural rat tumor models, for studies of tumor development and treatment.