Wang Li, Ding Yao, Bruno Teresa L, Stafford R Jason, Lin Eric, Bathala Tharakeswara K, Sanders Jeremiah W, Ning Matthew S, Ma Jingfei, Klopp Ann H, Venkatesan Aradhana, Wang Jihong, Martirosyan Karen S, Frank Steven J
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Cancers (Basel). 2024 May 18;16(10):1922. doi: 10.3390/cancers16101922.
Magnetic resonance imaging (MRI) can facilitate accurate organ delineation and optimal dose distributions in high-dose-rate (HDR) MRI-Assisted Radiosurgery (MARS). Its use for this purpose has been limited by the lack of positive-contrast MRI markers that can clearly delineate the lumen of the HDR applicator and precisely show the path of the HDR source on T1- and T2-weighted MRI sequences. We investigated a novel MRI positive-contrast HDR brachytherapy or interventional radiotherapy line marker, C4:S, consisting of C4 (visible on T1-weighted images) complexed with saline. Longitudinal relaxation time (T1) and transverse relaxation time (T2) for C4:S were measured on a 1.5 T MRI scanner. High-density polyethylene (HDPE) tubing filled with C4:S as an HDR brachytherapy line marker was tested for visibility on T1- and T2-weighted MRI sequences in a tissue-equivalent female ultrasound training pelvis phantom. Relaxivity measurements indicated that C4:S solution had good T1-weighted contrast (relative to oil [fat] signal intensity) and good T2-weighted contrast (relative to water signal intensity) at both room temperature (relaxivity ratio > 1; r2/r1 = 1.43) and body temperature (relaxivity ratio > 1; r2/r1 = 1.38). These measurements were verified by the positive visualization of the C4:S (C4/saline 50:50) HDPE tube HDR brachytherapy line marker on both T1- and T2-weighted MRI sequences. Orientation did not affect the relaxivity of the C4:S contrast solution. C4:S encapsulated in HDPE tubing can be visualized as a positive line marker on both T1- and T2-weighted MRI sequences. MRI-guided HDR planning may be possible with these novel line markers for HDR MARS for several types of cancer.
磁共振成像（MRI）有助于在高剂量率（HDR）MRI辅助放射外科治疗（MARS）中实现准确的器官轮廓描绘和优化剂量分布。其在此方面的应用一直受到缺乏阳性对比MRI标记物的限制，这些标记物无法在T1加权和T2加权MRI序列上清晰勾勒出HDR施源器的管腔并精确显示HDR源的路径。我们研究了一种新型的MRI阳性对比HDR近距离放射治疗或介入放射治疗线标记物C4:S，它由与盐水络合的C4（在T1加权图像上可见）组成。在1.5 T MRI扫描仪上测量了C4:S的纵向弛豫时间（T1）和横向弛豫时间（T2）。将填充有C4:S作为HDR近距离放射治疗线标记物的高密度聚乙烯（HDPE）管，在组织等效的女性超声训练盆腔模型中进行T1加权和T2加权MRI序列上的可视性测试。弛豫率测量表明，C4:S溶液在室温（弛豫率比>1；r2/r1 = 1.43）和体温（弛豫率比>1；r2/r1 = 1.38）下均具有良好的T1加权对比度（相对于油[脂肪]信号强度）和良好的T2加权对比度（相对于水信号强度）。通过在T1加权和T2加权MRI序列上对C4:S（C4/盐水50:50）HDPE管HDR近距离放射治疗线标记物的阳性可视化验证了这些测量结果。方向不影响C4:S对比溶液的弛豫率。封装在HDPE管中的C4:S可在T1加权和T2加权MRI序列上可视化为阳性线标记物。对于几种类型的癌症，使用这些新型线标记物进行HDR MARS的MRI引导HDR计划可能是可行的。
