Morikawa M, Numaguchi Y, Rigamonti D, Kuroiwa T, Rothman M I, Zoarski G H, Simard J M, Eisenberg H, Amin P P
Department of Diagnostic Radiology, University of Maryland Medical System, Baltimore, MD, USA.
Int J Radiat Oncol Biol Phys. 1996 Feb 1;34(3):663-75. doi: 10.1016/0360-3016(95)02160-4.
To evaluate the initial changes within the nidus of arteriovenous malformations (AVMs) and to assess the reaction to the brain tissue surrounding AVMs after radiosurgery by serial magnetic resonance (MR) imaging.
Twenty-one patients, treated using 60Co gamma knife unit with cerebral AVMs, were retrospectively evaluated. Forty-seven follow-up MR images of the 21 patients were performed including 10 patients with two or more serial gadolinium enhanced studies (Gd-MR). Two or more sequential MR angiographies (MRA) were obtained in 13 patients. Three-dimensional (3D) time-of-flight MRA and two-dimensional (2D) phase contrast MRA were used in 13 patients for evaluating the flow changes of AVMs. The follow-up period after radiosurgery ranged from 3 to 30 months (average 10.8 months) and the interval time of MRI ranged from 34 days to 13 months (average 4.9 months).
Reduction of nidus size was observed in 14 of 21 patients (67%) between 4 to 13 months on spin echo (SE) images. Complete obliteration was observed on SE images in 4 of these 14 patients; three were confirmed by conventional angiography. New hyperintense areas surrounding the nidus on T2s-weighted images (T2WI) developed in 9 of the 14 patients who showed nidus reduction between 5 to 17 months after radiosurgery; in three patients, size of the hyperintense area started to decrease between 6 to 7 months after its appearance. Probable radiation necrosis of pons developed in one patient 26 months after radiosurgery. The irradiated area within the AVM nidus was significantly enhanced in 8 of the 10 patients who underwent Gd-MR. The degrees of enhancement within the nidus increased with time in 7 of the 10 patients. Overall, total enhancement of irradiated areas was observed in four of the 10 patients; in three of the four, the enhancement decreased in size and degree, indicating nidus reduction. In three patients who had a partial volume irradiation within the nidus, the enhancing areas corresponded with the exact portions of irradiated volume. The nidus reduction was observed in 7 of the 13 patients on MRA during 5 to 13 months after radiosurgery. MRA was more useful compared to SE images in four of the seven patients in evaluating the size change of AVM nidus, feeding arteries, and draining veins.
Magnetic resonance imaging and MRA were useful in assessing the progress of nidus reduction. T2-weighted imaging was sensitive to radiation-induced reaction in and around the AVM nidus. The enhancement within the AVM nidus on Gd-MR may represent the initial sign of nidus reduction and demonstrates the exact location of irradiation in the nidus. The changes of the enhancement pattern are presumed to represent the processes of nidus reduction and irradiated reaction within the AVM nidus.
通过系列磁共振（MR）成像评估动静脉畸形（AVM）病灶内的初始变化，并评估放射外科治疗后AVM周围脑组织的反应。
回顾性评估21例使用60Co伽玛刀治疗脑AVM的患者。对这21例患者进行了47次随访MR成像，其中10例患者进行了两次或更多次连续钆增强研究（Gd-MR）。13例患者获得了两次或更多次连续的磁共振血管造影（MRA）。13例患者使用三维（3D）时间飞跃MRA和二维（2D）相位对比MRA评估AVM的血流变化。放射外科治疗后的随访期为3至30个月（平均10.8个月），MRI的间隔时间为34天至13个月（平均4.9个月）。
21例患者中有14例（67%）在4至13个月的自旋回波（SE）图像上观察到病灶大小减小。在这14例患者中，有4例在SE图像上观察到完全闭塞；其中3例经传统血管造影证实。在放射外科治疗后5至17个月内病灶缩小的14例患者中，有9例在T2加权图像（T2WI）上病灶周围出现新的高信号区；3例患者高信号区在出现后6至7个月开始缩小。1例患者在放射外科治疗后26个月发生可能的脑桥放射性坏死。在接受Gd-MR的10例患者中，有8例AVM病灶内的照射区域明显强化。10例患者中有7例病灶内强化程度随时间增加。总体而言，10例患者中有4例观察到照射区域的总强化；其中4例中的3例强化大小和程度减小，表明病灶缩小。在3例病灶内进行部分体积照射的患者中，强化区域与照射体积的准确部位相对应。在放射外科治疗后5至13个月，13例患者中有7例在MRA上观察到病灶缩小。在评估AVM病灶、供血动脉和引流静脉的大小变化方面，MRA在7例患者中的4例中比SE图像更有用。
磁共振成像和MRA有助于评估病灶缩小的进展。T2加权成像对AVM病灶内及其周围的放射诱导反应敏感。Gd-MR上AVM病灶内的强化可能代表病灶缩小的初始迹象，并显示病灶内照射的确切位置。强化模式的变化推测代表AVM病灶内病灶缩小和照射反应的过程。
