ISSN:
1432-1084
Keywords:
Magnetic resonance angiography
;
Arteriovenous malformations
;
Radiosurgery
;
Image correlation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract In this methodological paper the authors report the stereotactic correlation of different magnetic resonance imaging (MRI) techniques [MR-angiography (MRA), MRI, blood bolus tagging (STAR), and functional MRI] in 10 patients with ce rebral arteriovenous malformations (AVM) and its application in precision radiotherapy planning. The patient's head was fixed in a stereotactic localization system that is usable at the MR and the linear accelerator installations. Byphantom measurements different materials (steel, aluminium, titanium, plastic, wood, ceramics) used for the stereotactic system were tested for mechanical stability and geometrical MR image distortion. All metallic stereotactic rings (closed rings made of massive metal) led to a more or less dramatic geometrical distortion and signal cancellation in the MR images. The best properties —nearly no distortion and high mechanical stability are provided by a ceramic ring. If necessary, the re-maining geometrical MR image distortion can be “corrected” reducing displacements to the size of a pixel) by cal culations based on modelling the distortion as a fourth-order two-dimensional polynomial. Using this method multimodality matching can be performed automatically as long as all images are acquired ill the same examination and the patient is sufficiently immobilized. Precise definition ol the target volume could be performed by the radiotherapist either directly in MR images or in calculated projecon MR angiograms obtained by a maximum-intensity projection algorithm. As a result, information about the hemodynamics of the AVM was provided by a three-dimensional (3D) phase-contrast flow measurement and a dynamic MRA with the STAR technique leading to an improved definition of the size of the nidus, the origin of the feeding arteries, and the pattern of the venous drainage. In addition functional MRI was performed in patients wit lesions close to the primary motor cortex area leading to an improved definition of structures at risk for high-dose application in radiosurgery. The differnet imaging techniques of MR provide a sensitive, noninvasive, 3D method for de fining target volume, critical structures, and for calculating dose distributions for radiosurgery of cerebral arteriovenous malformations, because dose calculation of radiosurgery at sufficient accuracy can be based on 3D MR data of the geometrical conformation of the patient's head.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00619950
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