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Federico Colombo, Carlo Cavedon, Paolo Francescon, Leopoldo Casentini, Umberto Fornezza, Lucio Castellan, Francesco Causin and Stefano Perini

Object. Radiosurgical treatment of a cerebral arteriovenous malformation (AVM) requires the precise definition of the nidus of the lesion in stereotactic space. This cannot be accomplished using simple stereotactic angiography, but requires a combination of stereotactic biplanar angiographic images and stereotactic contrast-enhanced computerized tomography (CT) scans. In the present study the authors describe a method in which three-dimensional (3D) rotational angiography is integrated into stereotactic space to aid treatment planning for radiosurgery.

Methods. Twenty patients harboring AVMs underwent treatment planning prior to linear accelerator radiosurgery. Planning involved the acquisition of two different data sets, one of which was obtained using the standard method (a combination of biplanar stereotactic angiography with stereotactic CT scanning), and the other, which was procured using a new technique (nonstereotactic 3D rotational angiography combined with stereotactic CT scanning by a procedure of image fusion).

The treatment plan that was developed using the new method was compared with that developed using the standard one. For each patient the number of isocenters and the dimension of selected collimators were the same, based on the information supplied in both methods. Target coordinates were modified in only five cases and by a limited amount (mean 0.7 mm, range 0.3–1 mm).

Conclusions. The new imaging modality offers an easier and more immediate interpretation of 3D data, while maintaining the same accuracy in target definition as that provided by the standard technique. Moreover, the new method has the advantage of using nonstereotactic 3D angiography, which can be performed at a different site and a different time with respect to the irradiation procedure.

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Federico Colombo, Carlo Cavedon, Leopoldo Casentini, Paolo Francescon, Francesco Causin and Vittore Pinna

Object

The authors describe a method that utilizes an image-guided robotic radiosurgical apparatus (the CyberKnife) for treatment of cerebral arteriovenous malformations (AVMs). This procedure required the development of an original technique that allows a high degree of automation.

Methods

Angiographic images were imported into the treatment planning software by coregistering CT and 3D rotational angiography. The nidus contour was delineated using the contouring tools of the treatment planning system. Functional MR imaging was employed for contouring critical cortical regions, such as the motor cortex and language areas. Once the radiation dose to be delivered to the target volume and dose constraints to critical structures were prescribed, the inverse treatment planning function determined the optimal treatment plan.

Results

A series of 279 patients with cerebral AVMs underwent CyberKnife radiosurgery. One transitory adverse effect of the radiation procedure was observed. Eight bleeding occurrences were noted before complete AVM obliteration. Of the 102 patients with follow-up > 36 months, 80 underwent angiographic evaluation. In this group, 65 patients (81.2%) showed complete angiographic obliteration of their AVM. In 8 more patients, complete angiographic obliteration was demonstrated by MR angiography only.

Conclusions

This is the first report describing a technique developed for CyberKnife radiosurgery of cerebral AVMs. The use of different imaging modalities for automatic delineation of the target and critical structures combined with the employment of the inverse treatment planning capability is the crucial point of the procedure. The procedure proved to be safe and efficient.