Cerebrovascular enhancement in spoiled GRASS (SPGR) images: comparison with spin-echo technique

The signals and artifacts in cerebral blood vessels were systematically studied using a new three-dimensional Fourier transform (3DFT) technique, spoiled gradient recalled acquisition in steady state (SPGR), with parameters optimized for T1-weighted brain imaging. Twenty consecutive patients referred for routine cranial MR imaging were prospectively studied before and after the intravenous administration of Gd-DTPA using both 3DFT SPGR and conventional 2DFT SE imaging. A significant difference between the two techniques was noted in regard to the appearance of cerebral blood vessels and the degree of vascular pulsation artifact. Precontrast SPGR images demonstrated high signal in all (100%) internal carotid arteries and in nearly all (85-95%) vertebral, basilar, and proximal posterior, middle, and anterior cerebral arteries. High signal was variably present (5-50%) in more distal arterial branches. High signal from venous structures was not seen except in the superior sagittal sinus, which was bright in 75% of cases. Postcontrast SPGR images reliably demonstrated uniform high signal in all (100%) major arterial branches, up to fourth-order branches in the middle cerebral artery, diminishing toward the vertex. All (100%) major deep and superficial venous structures were of uniformly high signal, diminishing slightly as they exited the skull base. Flow related artifacts were found to be significantly (p = 0.001) reduced in contrast enhanced SPGR compared to SE images. As implemented in this study, SPGR and SE images demonstrate significantly different patterns of vascular signal that must be recognized for the proper interpretation of MR images.