Nidus delineation and dosimetric comparison in arteriovenous malformation in stereotactic radiosurgery by using MRI and 3DCT angiography

Accurate delineation of target is key to any successful radiosurgery. C-arm Dyna CT/ 3DCT angiography (3DCTA) has the potential of improving the accuracy of nidus delineation in intracranial arteriovenous malformations (AVM) due to high temporo-spatial resolution of vessel architecture. Here, we present a comparison of nidus delineation and dosimetric parameters between digital 3DCTA and MRI. Ten consecutive patients treated for intracranial AVMs were included in this study. All patients underwent MRI/MRA, and 3DCTA and all images were co-registered. AVM were delineated using 3DCTA (GTV ) and contrast enhanced MRI/MRA (GTV ). Hausdorff distance (HD) matrices and dice similarity coefficient (DSC) matrices were analysed. Stereotactic radiosurgery plans were developed for both the volumes for all patients and statistical analysis were performed with T-test. Mean volumes of GTV and GTV were 1.771 cc (SD 1.794cc, range 0.124-4.191cc) and 2.183cc (SD 2.16cc, range 0.221-6.133cc), respectively. Significant deviation (p=0.018) was found when taking GTV as a primary and comparing it to GTV (MD=0.723cc±0.816cc). Similar result was observed with GTV as primary and GTV as secondary (MD=0.188cc, SD=0.193cc, p=0.024). Maximum HD was in the range of 1.71 to 7.44mm (mean=4.27mm, SD=1.56). For GTV based plans, significant deviation was found between GTV and GTV in dose coverage and the mean difference was 22.17% (SD 16.73). In GTV based plans, the mean CIRTOG deteriorated from 1.33 to 2.18 for GTV and GTV , respectively. Significant deviation was found in CI (0.005) and mean deviation was 0.86(SD=0.72) when comparing GTV and GTV . Highly significant (p=0.002) deviation was found in CI between GTV and GTV for GTV based plans with mean difference of 0.26(SD=0.4, for GTV =0.3, GTV =0.46). Nidus volume was significantly altered with the use of 3DCTA compared to that of MRA/MRI images. Multimodality imaging is crucial for accurate target delineation, and successful radiosurgical obliteration of nidus.