The natural history of unruptured cerebral aneurysm is not known; also unknown is the potential growth and rupture in any individual aneurysm. The authors have developed transluminal color-coded three-dimensional magnetic resonance angiography (MRA) obtained by a time-of-flight sequence to investigate the interaction between the intra-aneurysmal signal intensity distribution patterns and configuration of unruptured cerebral aneurysms. Transluminal color-coded images were reconstructed from volume data of source magnetic resonance angiography by using a parallel volume-rendering algorithm with transluminal imaging technique. By selecting a numerical threshold range from a signal intensity opacity chart of the three-dimensional volume-rendering dataset several areas of signal intensity were depicted, assigned different colors, and visualized transparently through the walls of parent arteries and an aneurysm. Patterns of signal intensity distribution were analyzed with three operated cases of an unruptured anterior communicating artery aneurysm and compared with the actual configurations observed at microneurosurgery. A little difference in marginal features of an aneurysm was observed; however, transluminal color-coded images visualized the complex signal intensity distribution within an aneurysm in conjunction with aneurysmal geometry. Transluminal color-coded three-dimensional magnetic resonance angiography can thus provide numerical analysis of the interaction between spatial signal intensity distribution patterns and aneurysmal configurations and may offer an alternative and practical method to investigate the patient-specific natural history of individual unruptured cerebral aneurysms.
Although diffusion-weighted (DW) magnetic resonance (MR) imaging can detect hyperacute ischemic parenchyma with high sensitivity, the ability of DW images to reveal subtle change in abnormal diffusion may be limited by the conventional visual evaluation. To overcome the limitation, we have developed a method of transparent color-coded three-dimensional (3D) DW MR imaging for the computer-aided numerical analysis of hyperacute ischemic stroke. The 3D images were reconstructed from volume data of source DW images by using a parallel volume-rendering algorithm with transluminal imaging technique. By selecting a threshold range from a signal intensity opacity chart of volume-rendering data set, several high signal intensity areas were depicted and assigned to different colors, transparently through contours of the brain. This imaging was applied in a case of a recanalized middle cerebral artery (M2) occlusion with partially reversible ischemic parenchyma accompanied by partial recovery from ischemic neurological deficit. Complex and dynamic change in hyperacute ischemic parenchyma, with regression of subtle high signal intensity areas and progression of ischemic parenchyma, was depicted three-dimensionally. Transparent color-coded 3D DW MR imaging may provide computer-aided numerical analysis of hyperacute ischemic stroke appearing as a high signal intensity area on the source DW images.
To investigate the angioarchitecture of cerebral aneurysms, we studied various opacity curves to select specific volume data of CT and MR angiograms from the opacity charts of CT density or MR signal intensity distribution. We developed the method of transluminal imaging of CT and MR angiograms; the vessels and aneurysms were depicted transluminally through spaces between the rings of the vessel walls. Two cases of unruptured cerebral aneurysms were studied by transluminal imaging of three-dimensional CT and MR angiograms. The technical aspects of transluminal imaging and characteristics of volume data, obtained by CT and MR angiograms, were discussed.
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