Department of Radiation Oncology and Molecular Radiation Science, Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland.
Division of Biostatistics and Bioinformatics, Sidney Kimmel Comprehensive Cancer Center, Baltimore, Maryland.
Pract Radiat Oncol. 2019 May;9(3):e307-e313. doi: 10.1016/j.prro.2019.01.005. Epub 2019 Jan 23.
To evaluate the precision of 2 low-dose cone (LD) beam computed tomography (CBCT) protocols to align to bone and soft tissue for pediatric patients receiving image guided radiation therapy (IGRT) to the abdomen and pelvis.
Image-quality evaluation was done for 858 CBCT scans from 46 pediatric patients treated with IGRT from January 2015 to December 2017. The evaluations guided the development of 2 significantly dose-reduced protocols, LD-CBCT1 and a further dose-reduced LD-CBCT2. Representative scans from LD-CBCT1 and LD-CBCT2 from 8 patients with at least 1 CBCT scan from both protocols were registered separately to a bone and soft-tissue landmark on the simulation computed tomography scan. Eighteen identical blinded random offsets were applied to each patient's LD-CBCT1 and LD-CBCT2 from a starting registration that was then realigned using rigid registration. The residual offset between the baseline registration and the final registration attempt was calculated and analyzed using a 1-sided, 1 sample t test to evaluate whether LD-CBCT1, delivering a higher dose, was superior to the lower-dose LD-CBCT2 for bone and soft-tissue alignment.
In comparing 288 registrations with a bone landmark across 8 patients, no difference was found in the vector magnitude offsets using LD-CBCT 1 (mean [x¯], 0.73 mm; standard deviation [σ], 0.39 mm) and LD-CBCT2 (x¯, 0.74 mm; σ, 0.40 mm; P = .425). Comparing 216 registrations with a soft-tissue landmark across 6 patients, alignment using LD-CBCT2 (x¯, 1.55 mm; σ, 1.08 mm) resulted in larger differences in the vector magnitude of the offsets compared with LD-CBCT1 (x¯, 1.37 mm; σ, 0.74 mm; P = .049).
Clinics treating pediatric patients should consider implementing a protocol mirroring LD-CBCT2 for abdomen and pelvis IGRT bone alignment. Further evaluation of the precision of LD-CBCTs for soft-tissue alignment is necessary.
评估 2 种低剂量锥形束 CT（CBCT）协议在引导儿童患者接受腹部和骨盆图像引导放疗（IGRT）时，在骨和软组织配准方面的精度。
对 2015 年 1 月至 2017 年 12 月期间接受 IGRT 的 46 例儿科患者的 858 次 CBCT 扫描进行了图像质量评估。这些评估指导了 2 种显著降低剂量的协议的开发，即 LD-CBCT1 和进一步降低剂量的 LD-CBCT2。从这两种方案中，各选择 8 例患者中至少有 1 次 CBCT 扫描的代表性扫描，分别注册到模拟 CT 扫描上的骨和软组织标志。对每位患者的 LD-CBCT1 和 LD-CBCT2 从初始注册应用 18 个相同的、随机的、单侧、1 样本 t 检验的偏移量，然后使用刚性注册进行重新对齐。计算和分析基线注册和最终注册尝试之间的残余偏移量，以评估在骨和软组织配准方面，提供更高剂量的 LD-CBCT1 是否优于低剂量的 LD-CBCT2。
在比较 8 例患者的 288 个骨标志注册时，使用 LD-CBCT1（均值[x¯]，0.73mm；标准差[σ]，0.39mm）和 LD-CBCT2（x¯，0.74mm；σ，0.40mm；P=0.425）的矢量幅度偏移量无差异。在比较 6 例患者的 216 个软组织标志注册时，与 LD-CBCT1（x¯，1.37mm；σ，0.74mm）相比，使用 LD-CBCT2（x¯，1.55mm；σ，1.08mm）导致偏移量的矢量幅度差异更大（P=0.049）。
治疗儿科患者的临床医生应考虑为腹部和骨盆 IGRT 骨配准实施类似于 LD-CBCT2 的方案。有必要进一步评估 LD-CBCT 在软组织配准方面的精度。
