Objective

To investigate whether a SPIO-labeling technique could enable MR visualization of the treatment margin after X-irradiation at a single dose of 30 Gy.

Materials and methods

Fifteen rats bearing N1-S1 hepatoma in either the left (group 1) or right (group 2) liver lobe were examined. Four hours after systemic SPIO administration, the left lobe was selectively irradiated at 30 Gy. Liver T2* maps were acquired 7 days later using a 9.4 T scanner. The livers were excised and examined histologically.

Results

The irradiated area showed T2*-weighted hypointensity with significantly shorter T2* values than those in the non-irradiated area (p < 0.001). Tumors in group 1 completely disappeared, whereas tumors in group 2 had grown outside the T2*-weighted hypointensity by up to ~ 2.3 times that at baseline. Group 1 showed significantly higher probability of tumor regression than group 2 (p = 0.048). Histologically, iron deposition was heavier in irradiated areas than in non-irradiated areas.

Discussion

Even at a single dose of 30 Gy, which is a slightly higher dose than can be used clinically in stereotactic body radiotherapy, MR visualization of the treatment margin was achieved, because tumors showed significant growth outside the T2*-hypointense areas. In contrast, tumors disappeared inside the T2*-hypointense areas.

中文翻译：

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肝脏肿瘤放射治疗的治疗边缘在 9.4 T 时在 SPIO 增强 MRI 上显示为 T2*-低信号区域。

客观的

研究 SPIO 标记技术是否可以在单剂量 30 Gy 的 X 辐射后实现治疗边缘的 MR 可视化。

材料和方法

检查了左侧（第 1 组）或右侧（第 2 组）肝叶中的 15 只携带 N1-S1 肝癌的大鼠。全身 SPIO 给药后 4 小时，左叶选择性照射 30 Gy。7 天后使用 9.4 T 扫描仪获取肝脏 T2* 图。切除肝脏并进行组织学检查。

结果

辐照区域显示 T2* 加权低信号，T2* 值明显短于未辐照区域 ( p  < 0.001)。第 1 组中的肿瘤完全消失，而第 2 组中的肿瘤在 T2* 加权低信号之外生长至基线时的约 2.3 倍。第 1 组的肿瘤消退概率显着高于第2 组（p  = 0.048）。在组织学上，辐照区域的铁沉积比非辐照区域重。

讨论

即使在 30 Gy 的单剂量下，这比临床上用于立体定向放射治疗的剂量略高，也实现了治疗边缘的 MR 可视化，因为肿瘤在 T2* 低信号区域外显示出显着的生长。相反，肿瘤在 T2*-低信号区域内消失。