Stereotactic radiosurgery of intracranial arteriovenous malformations and the use of the K index in determining treatment dose

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The appropriate dose during stereotactic radiosurgery (SRS) of cerebral arteriovenous malformations (AVMs) remains a matter of debate. In the present study, the authors retrospectively evaluated the association of using a prescribed dose calculated utilizing the K index with the obliteration rate of cerebral AVMs after SRS.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The authors performed a retrospective analysis of the Cleveland Clinic SRS database. All patients undergoing Gamma Knife radiosurgery for cerebral AVMs from 1997 to 2010 were selected. Regression techniques and Kaplan-Meier analyses were used to investigate the effect of divergence from the optimal K index dose on the rate of AVM obliteration.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>In the study period 152 patients (mean age 43.6 years; 53.9% of treatments were performed in females) underwent 165 Gamma Knife radiosurgery treatments for AVMs. In a univariate analysis Spetzler-Martin grade (OR 0.63 [95% CI 0.42–0.93]), higher AVM score (OR 0.43 [95% CI 0.27–0.70]), larger AVM volume (OR 0.88 [95% CI 0.82–0.94]), and higher maximum diameter (OR 0.56 [95% CI 0.41–0.77]) were associated with a lower rate of AVM obliteration. Higher margin dose (OR 1.16 [95% CI 1.08–1.24]) and higher maximum dose (OR 1.08 [95% CI 1.04–1.13]) were associated with a higher obliteration rate. To further examine the effect of prescribed dose divergence from the calculated K index dose, cases were classified to groups depending on the AVM volume and dose variance from the ideal K index dose. Contingency tables and Kaplan-Meier curves were then created, and no significant differences in rates of obliteration were noted among the different groups.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Gamma Knife radiosurgery for cerebral AVMs remains an effective and safe treatment modality. Smaller AVMs may receive doses less than the calculated K index dose without an apparent effect on obliteration rates.</jats:p></jats:sec>

Stereotactic radiosurgery for pediatric patients with intracranial arteriovenous malformations: Variables that may affect obliteration time and probability

“…Examples of additional indexes include the Karlsson index (KI) [3,15,16] and the obliteration index (OPI) [3,7]. The main drawback of these two indexes is that both consider the minimum radiation dose as a variable.…”

“…The discrete variables analyzed to evaluate their influence on obliteration were the following: sex, previous hemorrhage, venous drainage, previous treatment, location (according to RBAS index), Spetzler-Martin scale, AVM dose equal/higher or lower than the dose based on the K index and treatment technique. The volume was separated into groups of patients with <2 cm 3 , 2-10 cm 3 , and >10 cm 3 [15]. The patient follow-up time was separated into three different groups; ≤3 years, 3-4 years, and >4years.…”

“…The K index dose has been defined as the optimal prescription dose when K index value is 27 and it was calculated as the product of the cube root of the AVM volume and 27 [15]. We calculated the deviation of the actual prescription dose and the K index dose as previously proposed by Missios et al [15].…”

“…We calculated the deviation of the actual prescription dose and the K index dose as previously proposed by Missios et al [15].…”

Quantification of hemodynamics of cerebral arteriovenous malformations after stereotactic radiosurgery using 4D flow magnetic resonance imaging

“…After SRS, the most common strategy to monitor AVMs includes posttreatment magnetic resonance imaging (MRI) repeated at regular intervals, usually at a minimum of 6 months posttreatment, to follow AVM resolution. Once complete resolution is visualized, angiography is performed to confirm obliteration of the AVM nidus 6–10 . Obliteration of AVM on digital subtraction angiography (DSA) is defined as absence of arteriovenous shunting or disappearance of AVM nidus and early draining veins 9,11–13 .…”