Department for Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany.
Radiat Oncol. 2013 Mar 6;8:52. doi: 10.1186/1748-717X-8-52.
Structural follow-up magnetic resonance imaging (MRI) after stereotactic radiosurgery (SRS) for brain metastases frequently displays local changes in the area of applied irradiation, which are often difficult to interpret (e.g., local tumor recurrence, radiation-induced changes). The use of stereotactic biopsy for histological assessment of these changes has a high diagnostic accuracy and can be considered as method of choice. In order to solve this relevant clinical problem non-invasively, advanced MRI techniques and amino acid positron-emission-tomography (PET) are increasingly used.
We report the long-term follow-up of a patient who had been treated with linear accelerator based SRS for cerebral metastases of a lung cancer. Fifty-eight months after SRS, the differentiation of local recurrent brain metastasis from radiation-induced changes using structural MRI was difficult. For further differentiation, perfusion-weighted MRI (PWI), proton magnetic resonance spectroscopy (MRS), and (11)C-methyl-L-methionine (MET) PET was performed. Due to artifacts and technical limitations, PWI MRI and MRS findings were not conclusive. In contrast, MET PET findings were suggestive for radiation-induced changes. Finally, a stereotactic biopsy for histological assessment of these changes demonstrated clearly a radiation-induced necrosis and the absence of vital tumor.
The use of stereotactic biopsy for histological assessment of indistinguishable lesions on structural MRI after SRS for treatment of brain metastasis represents a highly reliable method to differentiate local tumor recurrence from radiation-induced changes. In this field, results of studies with both advanced MRI techniques and amino acid PET suggest encouraging results. However, artifacts and technical limitations (e.g., lesion size) are still a problem and comparative studies are needed to investigate the relationship, diagnostic performance, and complementary character of advanced MRI techniques and amino acid PET.
立体定向放射外科（SRS）治疗脑转移瘤后进行结构磁共振成像（MRI）随访时，经常会显示照射区域内的局部变化，这些变化通常难以解释（例如，局部肿瘤复发、放射性改变）。对这些变化进行立体定向活检以进行组织学评估具有很高的诊断准确性，可被视为首选方法。为了无创解决这一相关临床问题，越来越多地使用先进的 MRI 技术和氨基酸正电子发射断层扫描（PET）。
我们报告了一名肺癌脑转移患者接受直线加速器 SRS 治疗后的长期随访情况。在 SRS 后 58 个月，使用结构 MRI 区分局部复发性脑转移与放射性改变较为困难。为了进一步区分，进行了灌注加权 MRI（PWI）、质子磁共振波谱（MRS）和（11）C-甲基-L-蛋氨酸（MET）PET。由于伪影和技术限制，PWI MRI 和 MRS 的结果没有定论。相比之下，MET PET 的结果提示为放射性改变。最终，对这些变化进行了立体定向活检以进行组织学评估，结果清楚地显示为放射性坏死且无存活肿瘤。
对于 SRS 治疗脑转移瘤后结构 MRI 上无法区分的病变，使用立体定向活检进行组织学评估是一种非常可靠的方法，可区分局部肿瘤复发与放射性改变。在这一领域，使用先进 MRI 技术和氨基酸 PET 的研究结果表明有令人鼓舞的结果。然而，伪影和技术限制（例如，病变大小）仍然是一个问题，需要进行比较研究以调查先进 MRI 技术和氨基酸 PET 的关系、诊断性能和互补性。
