Department of Radiation Oncology, Johns Hopkins University School of Medicine, 5255 Loughboro Road NW, Washington, DC, USA.
Department of Radiology, Stanford University, Stanford, CA, USA.
Radiat Oncol. 2024 Aug 6;19(1):105. doi: 10.1186/s13014-024-02499-2.
To evaluate the relationship between delivered radiation (RT) and post-RT inversion-recovery ultrashort-echo-time (IR-UTE) MRI signal-intensity (SI) in gynecologic cancer patients treated with high-dose-rate (HDR) brachytherapy (BT).
Seven patients underwent whole-pelvis RT (WPRT) followed by BT to the high-risk clinical target volume (HR-CTV). MR images were acquired at three time-points; pre-RT, post-WPRT/pre-BT, and 3-6 months post-BT. Diffuse-fibrosis (F) was imaged with a non-contrast dual-echo IR (inversion time [TI] = 60 ms) UTE research application, with image-subtraction of the later echo, only retaining the ultrashort-echo SI. Dense-fibrosis (F) imaging utilized single-echo Late-Gadolinium-Enhanced IR-UTE, acquired ∼ 15 min post-Gadavist injection. Resulting F and F SI were normalized to the corresponding gluteal-muscle SI. Images were deformably registered between time-points based on normal tissue anatomy. The remnant tumor at both time-points was segmented using multi-parametric MRI. Contours corresponding to the 50%, 100%, 150%, and 200% isodose lines (IDLs) of the prescription BT-dose were created. Mean F and F SI within (i) each IDL contour and (ii) the remnant tumor were calculated. Post-BT F and F SI were correlated with prescribed BT-dose. To determine the relationship between BT-dose and IR-UTE SI, the differences in the post-BT F across IDLs was determined using paired t-tests with Bonferroni correction.
F was higher in regions of higher dose for 6/7 patients, with mean ± SD values of 357 ± 103% and 331 ± 97% (p = .03) in the 100% and 50% IDL, respectively. F was higher in regions of higher dose in the responsive regions with mean ± SD values of 380 ± 122% and 356 ± 135% (p = .03) in the 150% and 50% IDL, respectively. Within the segmented remnant tumor, an increase in prescribed dose correlated with an increase in F post-BT (n = 5, r = .89, p = .04). Post-BT F inversely correlated (n = 7, r = -.83, p = .02) with prescribed BT-dose within the 100% IDL.
Results suggest that F SI 3-6 months post-BT is a sensitive measure of tissue response to heterogeneous BT radiation-dose. Future studies will validate whether F and F are accurate biomarkers of fibrotic radiation response.
评估在接受高剂量率（HDR）近距离放疗（BT）治疗的妇科癌症患者中，给予的放疗（RT）与放疗后反转恢复超短回波时间（IR-UTE）磁共振成像（MRI）信号强度（SI）之间的关系。
7 名患者接受全骨盆 RT（WPRT），随后对高危临床靶区（HR-CTV）进行 BT。在三个时间点采集 MR 图像：放疗前（pre-RT）、WPRT/BT 前（post-WPRT/pre-BT）和 BT 后 3-6 个月。弥散性纤维化（F）采用非对比双回波反转恢复 UTE 研究应用进行成像，使用后期回波的图像减影，仅保留超短回波 SI。致密纤维化（F）成像采用单回波晚期钆增强反转恢复 UTE，在注射加钆造影剂后约 15 分钟采集。得到的 F 和 F SI 与相应的臀肌 SI 进行归一化。基于正常组织解剖学，在时间点之间对图像进行可变形配准。在两个时间点使用多参数 MRI 对残留肿瘤进行分段。在相应的处方 BT 剂量的 50%、100%、150%和 200%等剂量线（IDL）处创建肿瘤轮廓。计算（i）每个 IDL 轮廓内和（ii）残留肿瘤内的 F 和 F SI。分析 BT 剂量与 post-BT 的 F 和 F SI 之间的相关性。为了确定 BT 剂量与 IR-UTE SI 之间的关系，使用配对 t 检验和 Bonferroni 校正确定了 post-BT F 在不同 IDL 之间的差异。
在 6/7 名患者中，在剂量较高的区域 F 更高，100%和 50% IDL 的平均（±SD）值分别为 357±103%和 331±97%（p=0.03）。在反应性区域，在剂量较高的区域 F 更高，150%和 50% IDL 的平均（±SD）值分别为 380±122%和 356±135%（p=0.03）。在分割的残留肿瘤内，随着处方剂量的增加，post-BT 的 F 增加（n=5，r=0.89，p=0.04）。在 100% IDL 内，post-BT F 与处方 BT 剂量呈负相关（n=7，r=-0.83，p=0.02）。
结果表明，BT 后 3-6 个月的 F SI 是反映组织对不均匀 BT 辐射剂量反应的敏感指标。未来的研究将验证 F 和 F 是否是纤维化辐射反应的准确生物标志物。
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