Brigham and Women's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA.
Brigham and Women's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA.
Brachytherapy. 2022 Jul-Aug;21(4):501-510. doi: 10.1016/j.brachy.2022.01.003. Epub 2022 Mar 22.
A pointwise encoding time reduction with radial acquisition (PETRA) sequence was optimized to detect empty catheters in interstitial (HDR) brachytherapy with clinically acceptable spatial accuracy for the first time. Image quality and catheter detectability were assessed in phantoms, and the feasibility of PETRA's clinical implementation was assessed on a gynecological cancer patient.
Empty catheters embedded in a gelatin phantom displayed positive signal on PETRA and more accurate cross-sections than on clinically employed T2-weighted sequences, differing by 0.4 mm on average from their nominal 2 mm diameter. PETRA presented minimal susceptibility differences and a symmetric metal artifact, contrary to the clinical sequences. The PETRA-CT catheter tip position differences assessed by a treatment planning system (TPS) were < 1 mm. PETRA also detected an interstitial template with empty catheters penetrating a poultry phantom and fused very well with CT. Interstitial catheter positional difference between PETRA and CT images was < 1 mm on average, increasing with distance from isocenter. All interstitial catheters and the employed interstitial template were detected on PETRA images of an endometrial adenocarcinoma patient. Empty needles were traceable using a TPS, with higher spatial resolution and more favorable contrast than on T2-weighted images used for contouring. A treatment plan could be produced by combining information from PETRA for catheter detection and from T2-weighted images for tumor and organs delineation.
PETRA detected successfully and accurately interstitial catheters in phantoms. Its first clinical implementation shows a potential for MR-only treatment planning in interstitial HDR brachytherapy.
首次利用基于径向采集的点编码时间缩短（PETRA）序列优化检测间质（HDR）近距离治疗中排空的导管，空间定位精度达到临床可接受水平。我们在体模中评估了图像质量和导管可探测性，并在一名妇科癌症患者中评估了 PETRA 临床应用的可行性。
嵌入明胶体模中的空导管在 PETRA 上显示出阳性信号，且比临床应用的 T2 加权序列更准确的横断面，平均直径相差 0.4 毫米。与临床序列相比，PETRA 显示出最小的磁化率差异和对称的金属伪影。治疗计划系统（TPS）评估的 PETRA-CT 导管尖端位置差异<1 毫米。PETRA 还检测到一个带有穿透家禽体模的空导管的间质模板，并与 CT 很好地融合。PETRA 和 CT 图像的间质导管位置差异平均<1 毫米，从等中心距离增加。在一名子宫内膜腺癌患者的 PETRA 图像中，所有间质导管和使用的间质模板均被检测到。TPS 可追踪空针，空间分辨率更高，与用于勾画的 T2 加权图像相比对比度更好。通过结合来自 PETRA 的导管检测信息和来自 T2 加权图像的肿瘤和器官勾画信息，可以生成治疗计划。
PETRA 成功且准确地检测了体模中的间质导管。其首次临床应用表明，在间质 HDR 近距离治疗中，仅使用磁共振成像（MRI）进行治疗计划具有潜力。
