VIRTUAL CISTERNOSCOPY OF INTRACRANIAL VESSELS - A NOVEL VISUALIZATIONTECHNIQUE USING VIRTUAL-REALITY

This paper introduces a different visualization method which we call ' 'virtual cisternoscopy'' using 3D MRA data sets. Virtual cisternoscopy uses well known tools, such as perspective volume rendering (pVR), fl y-through techniques, and interactive visualization and combines them to a new approach featuring motion to resolve spatial relationships of intracranial vessels and vascular malformations. With a dedicated fli ght protocol extraluminal topography of intracranial arteries was anal yzed using pVR. For evaluation of difficult vascular malformations ext raluminal views are necessary. Therefore, movies of pVR views were pro duced simulating virtual tracks of neurosurgical flexible endoscopes, by flying around the intracranial vessels and vascular malformations w ithin the cisterns. Endoluminal views were acquired additionally for p recise evaluation of cases with complex vessel topography. Two healthy volunteers and three patients were examined. Comparing MIP and pVR im ages relevant advantages of pVR were found, such as depth information, perspective, lighting, and color. In contrast to MIP and source image s of the MRA data set, virtual cisternoscopy of an aneurysm of the lef t middle cerebral artery demonstrated clearly an early origin of an ar tery in the region of the aneurysm neck/sac. In this case only virtual cisternoscopy led to the correct therapeutical decision. In a newborn , the type of a vein of Galen aneurysmal malformation could only be ev aluated reliably by means of virtual cisternoscopy. The third case of a patient with a clipped aneurysm was evaluated more easily with virtu al cisternoscopy than with DSA. In conclusion, virtual cisternoscopy m ay improve the pretherapeutical visualization of intracranial vascular malformations. (C) 1998 Elsevier Science Inc.