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目的评估扩散加权成像(DWI)在灌注加权成像(PWI)鉴别肿瘤进展和放射性坏死中的附加价值。方法回顾性分析连续16例因立体定向放射治疗术后肿瘤体积增大而接受脑转移瘤切除手术的病人。采用3种模式将ADC分层。测量每个层面上的ADC值及局部脑血容量(rCBV)最大值。比较放射性坏死和肿瘤进展病人的rCBV和ADC的分层模式。结果病理证实16例手术病人中9例为放射性坏死,7例为肿瘤进展。放射性坏死的病例(88.9%,肿瘤进展14.3%)的3层模式更多地表现为一种中间层ADC值最小的模式。如果以rCBV>2.6来区分放射性坏死和肿瘤进展,其敏感度是100%,但特异度是56%。如果根据这种ADC3层模式加上中度升高的rCBV(2.6~4.1)排除肿瘤进展,则敏感度和特异度均为100%。结论这种ADC的3层模式诊断放射性坏死的特异性很高。因此,结合ADC模式和rCBV可能在正确鉴别肿瘤进展和放射性坏死方面具有额外的价值。要点①MRI随访经常发现立体定向放射治疗后的增强病灶体积增大。②肿瘤坏死灶周围的炎症增加了rCBV,表现类似肿瘤的进展。③扩散加权MRI的ADC3层模式可提示放射性坏死。④rCBV和DWMRI的联合应用可准确鉴别放射性坏死和肿瘤进展。
Objective To assess the value of diffusion-weighted imaging (DWI) in perfusion-weighted imaging (PWI) to identify tumor progression and radiation necrosis. Methods A retrospective analysis of 16 consecutive patients who undergone tumor resection for brain metastases after stereotactic radiotherapy was performed. The ADC is layered in 3 modes. ADC values at each level and maximum local cerebral blood volume (rCBV) were measured. Hierarchical patterns of rCBV and ADC in patients with radiological necrosis and tumor progression were compared. Results The pathology confirmed that of the 16 surgical patients, 9 were radioactive necrosis and 7 were tumor progression. The 3-layer model for cases of radioactive necrosis (88.9%, tumor progression 14.3%) showed more as a mode with the lowest median ADC value. If rCBV> 2.6 is used to distinguish between radiological necrosis and tumor progression, the sensitivity is 100%, but the specificity is 56%. Sensitivity and specificity were both 100% if tumor progression was ruled out on the basis of this ADC3 model plus moderately elevated rCBV (2.6-4.1). Conclusion The 3-layer model of this ADC is highly specific for the diagnosis of radioactive necrosis. Therefore, binding to ADC patterns and rCBV may have additional value in correctly identifying tumor progression and radiation necrosis. Points ①MRI follow-up often found that stereotactic radiation therapy enhanced lesions increased volume. ② inflammation around the tumor necrosis increased rCBV, the performance of similar tumor progression. ③ diffusion-weighted MRI ADC3 layer model can prompt radiation necrosis. ④ rCBV and DWMRI combined application can accurately identify the radioactive necrosis and tumor progression.