Division of Neurosurgery, Shizuoka Cancer Center, Sunto, Japan.
J Neurooncol. 2010 Aug;99(1):81-8. doi: 10.1007/s11060-009-0106-z. Epub 2010 Jan 8.
After stereotactic radiosurgery (SRS) for brain metastases, delayed radiation effects with mass effect may occur from several months to years later, when tumors may also recur. Aggressive salvage treatment would be beneficial for patients with recurrence, but may be contraindicated for those with dominant radiation effect. Conventional magnetic resonance (MR) imaging does not provide sufficient information to differentiate delayed radiation effects from tumor recurrence. Positron emission tomography, MR spectroscopy, and other modalities sometimes may lead to false findings of tumor recurrence. We prospectively applied perfusion MR imaging for the management strategy after SRS because it gives microvascular information about the lesions. Twenty-eight lesions were enlarged on serial MR images in 27 patients 2-35 months (median: 11.8 months) after SRS for metastatic brain tumors. Each patient underwent MR perfusion imaging within a month after appearance of the growing enhanced lesion. To calculate the relative cerebral blood volume ratio (rCBV ratio), the regions of interest were located in the enhanced areas on the contrast-enhanced T1-weighted images and compared with the corresponding contralateral normal brain tissue. They were then followed-up with scheduled MR images with gadolinium enhancement at 1 to 2-month intervals afterward. Lesions which progressively increased in size on MR images were diagnosed as recurrences; lesions which disappeared or decreased in size were diagnosed as radiation necrosis. In addition, two lesions surgically removed were diagnosed by pathological examination. Follow-up MR images revealed that 21 of 28 lesions were radiation necrosis. Five lesions were diagnosed as recurrence on MR images, and the other two lesions were revealed as recurrence by pathological examination. An rCBV ratio of greater than 2.1 provided the best sensitivity and specificity for identifying recurrent metastatic tumors, at 100 and 95.2%, respectively. Perfusion MR imaging provides useful, less invasive and in-vivo information for management of growing lesions after SRS, and rCBV may be a valuable index for this diagnostic purpose.
立体定向放射外科（SRS）治疗脑转移瘤后，数月至数年后可能会出现迟发性放射性效应和占位效应，此时肿瘤也可能复发。对于复发的患者，积极的挽救性治疗将是有益的，但对于放射性效应为主的患者可能是禁忌的。常规磁共振（MR）成像不能提供足够的信息来区分迟发性放射性效应和肿瘤复发。正电子发射断层扫描（PET）、MR 波谱和其他方式有时可能导致肿瘤复发的假阳性结果。我们前瞻性地应用灌注磁共振成像来制定 SRS 后的治疗策略，因为它可以提供病变的微血管信息。27 例患者在 SRS 治疗转移性脑肿瘤后 2-35 个月（中位数：11.8 个月）的连续 MR 图像上发现 28 个病灶增大。每个患者在增强的病变出现后 1 个月内进行 MR 灌注成像。为了计算相对脑血容量比（rCBV 比），在对比增强 T1 加权图像上的增强区域放置感兴趣区，并与相应的对侧正常脑组织进行比较。然后，在随后的 1-2 个月的增强 MRI 随访中进行了定位。在 MR 图像上逐渐增大的病变被诊断为复发；病变消失或缩小的被诊断为放射性坏死。此外，通过手术切除的两个病变通过病理检查进行了诊断。随访 MR 图像显示 28 个病变中有 21 个为放射性坏死。5 个病变在 MR 图像上被诊断为复发，另外 2 个病变通过病理检查被诊断为复发。rCBV 比大于 2.1 对识别复发性转移性肿瘤具有最佳的敏感性和特异性，分别为 100%和 95.2%。灌注磁共振成像为 SRS 后生长病变的管理提供了有用的、微创的、体内信息，rCBV 可能是这一诊断目的的一个有价值的指标。
