Institute of Clinical Radiology and Nuclear Medicine, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany.
Strahlenther Onkol. 2012 Dec;188(12):1146-54. doi: 10.1007/s00066-012-0254-5. Epub 2012 Nov 1.
Adjuvant radiochemotherapy (RCHT) improves survival of patients with locally advanced gastric cancer. Conventional three-dimensional conformal radiotherapy (3D-CRT) results in ablative doses to a significant amount of the left kidney, while image-guided intensity-modulated radiotherapy (IG-IMRT) provides excellent target coverage with improved kidney sparing. Few long-term results on IMRT for gastric cancer, however, have been published. Functional magnetic resonance imaging (fMRI) at 3.0 T including blood oxygenation-level dependent (BOLD) imaging, diffusion-weighted imaging (DWI) and, for the first time, (23)Na imaging was used to evaluate renal status after radiotherapy with 3D-CRT or IG-IMRT.
Four disease-free patients (2 after 3D-CRT and 2 after IMRT; FU for all patients > 5 years) were included in this feasibility study. Morphological sequences, axial DWI images, 2D-gradient echo (GRE)-BOLD images, and (23)Na images were acquired. Mean values/standard deviations for ((23)Na), the apparent diffusion coefficient (ADC), and R2* values were calculated for the upper/middle/lower parts of both kidneys. Corticomedullary (23)Na-concentration gradients were determined.
Surprisingly, IG-IMRT patients showed no morphological alterations and no statistically significant differences of ADC and R2* values in all renal parts. Values for mean corticomedullary (23)Na-concentration matched those for healthy volunteers. Results were similar in 3D-CRT patients, except for the cranial part of the left kidney. This was atrophic and presented significantly reduced functional parameters (p = 0.001-p = 0.033). Reduced ADC values indicated reduced cell density and reduced extracellular space. Cortical and medullary R2* values of the left cranial kidney in the 3D-CRT group were higher, indicating more deoxygenated hemoglobin due to reduced blood flow/oxygenation. ((23)Na) of the renal cranial parts in the 3D-CRT group was significantly reduced, while the expected corticomedullary (23)Na-concentration gradient was partially conserved.
Functional MRI can assess postradiotherapeutic renal changes. As expected, marked morphological/functional effects were observed in high-dose areas (3D-CRT), while, unexpectedly, no alteration in kidney function was observed in IG-IMRT patients, supporting the hypothesis that reducing total/fractional dose to the renal parenchyma by IMRT is clinically beneficial.
辅助放化疗（RCHT）可提高局部晚期胃癌患者的生存率。传统的三维适形放疗（3D-CRT）会导致左肾大量受到消融剂量照射，而图像引导调强放疗（IG-IMRT）则可提供出色的靶区覆盖范围，并能更好地保护肾脏。然而，目前关于胃癌 IMRT 的长期结果报道较少。本研究首次使用 3.0T 功能磁共振成像（fMRI），包括血氧水平依赖（BOLD）成像、弥散加权成像（DWI）和（23）Na 成像，来评估 3D-CRT 或 IG-IMRT 放疗后肾脏的状况。
本研究纳入了 4 名无疾病患者（3D-CRT 后 2 例，IMRT 后 2 例；所有患者的随访时间均＞5 年）。采集了形态学序列、轴位 DWI 图像、二维梯度回波（GRE）-BOLD 图像和（23）Na 图像。计算了双侧肾脏上/中/下部分的（23）Na、表观扩散系数（ADC）和 R2*值的平均值/标准差。确定了皮质-髓质（23）Na 浓度梯度。
出乎意料的是，IG-IMRT 患者的肾脏形态没有改变，所有肾脏部位的 ADC 和 R2值也没有统计学上的显著差异。皮质-髓质（23）Na 浓度平均值与健康志愿者的结果相匹配。3D-CRT 患者的结果相似，除了左肾的颅侧部分。该部分出现萎缩，功能参数显著降低（p=0.001-p=0.033）。ADC 值降低表明细胞密度降低和细胞外空间减少。左肾颅侧的皮质和髓质 R2值在 3D-CRT 组中更高，表明由于血流/氧合减少，脱氧血红蛋白更多。3D-CRT 组肾颅侧部分的（23）Na 明显减少，而预期的皮质-髓质（23）Na 浓度梯度部分保留。
功能磁共振成像可评估放疗后的肾脏变化。如预期的那样，在高剂量区域（3D-CRT）观察到明显的形态/功能变化，而令人意外的是，IG-IMRT 患者的肾脏功能没有改变，这支持了通过 IMRT 减少肾脏实质的总剂量/分割剂量对临床有益的假设。
