Nidus delineation and dosimetric comparison in arteriovenous malformation in stereotactic radiosurgery by using MRI...

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_3DCTA) and contrast enhanced MRI/MRA (GTV_MRI). 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_3DCTA and GTV_MRI 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_MRI as a primary and comparing it to GTV_3DCTA (MD=0.723cc±0.816cc). Similar result was observed with GTV_3DCTA as primary and GTV_MRI 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_3DCTA based plans, significant deviation was found between GTV_MRI and GTV_3DCTA in dose coverage and the mean difference was 22.17% (SD 16.73). In GTV_MRI based plans, the mean CIRTOG deteriorated from 1.33 to 2.18 for GTV_MRI and GTV_3DCTA, respectively. Significant deviation was found in CI_RTOG (0.005) and mean deviation was 0.86(SD=0.72) when comparing GTV_MRI and GTV_3DCTA. Highly significant (p=0.002) deviation was found in CI_Paddick between GTV_MRI and GTV_3DCTA for GTV_MRI based plans with mean difference of 0.26(SD=0.4, for GTV_MRI=0.3, GTV_3DCTA=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.