Johns Hopkins University, Baltimore, MD 21210, United States.
Med Image Anal. 2012 Apr;16(3):731-43. doi: 10.1016/j.media.2010.07.011. Epub 2010 Aug 14.
Brachytherapy (radioactive seed insertion) has emerged as one of the most effective treatment options for patients with prostate cancer, with the added benefit of a convenient outpatient procedure. The main limitation in contemporary brachytherapy is faulty seed placement, predominantly due to the presence of intra-operative edema (tissue expansion). Though currently not available, the capability to intra-operatively monitor the seed distribution, can make a significant improvement in cancer control. We present such a system here.
Intra-operative measurement of edema in prostate brachytherapy requires localization of inserted radioactive seeds relative to the prostate. Seeds were reconstructed using a typical non-isocentric C-arm, and exported to a commercial brachytherapy treatment planning system. Technical obstacles for 3D reconstruction on a non-isocentric C-arm include pose-dependent C-arm calibration; distortion correction; pose estimation of C-arm images; seed reconstruction; and C-arm to TRUS registration.
In precision-machined hard phantoms with 40-100 seeds and soft tissue phantoms with 45-87 seeds, we correctly reconstructed the seed implant shape with an average 3D precision of 0.35 mm and 0.24 mm, respectively. In a DoD Phase-1 clinical trial on six patients with 48-82 planned seeds, we achieved intra-operative monitoring of seed distribution and dosimetry, correcting for dose inhomogeneities by inserting an average of over four additional seeds in the six enrolled patients (minimum 1; maximum 9). Additionally, in each patient, the system automatically detected intra-operative seed migration induced due to edema (mean 3.84 mm, STD 2.13 mm, Max 16.19 mm).
The proposed system is the first of a kind that makes intra-operative detection of edema (and subsequent re-optimization) possible on any typical non-isocentric C-arm, at negligible additional cost to the existing clinical installation. It achieves a significantly more homogeneous seed distribution, and has the potential to affect a paradigm shift in clinical practice. Large scale studies and commercialization are currently underway.
近距离放射治疗(放射性种子插入)已成为治疗前列腺癌患者的最有效治疗方法之一,其附加优势是便利的门诊程序。当代近距离放射治疗的主要限制是种子位置不当,主要是由于术中水肿(组织扩张)的存在。尽管目前尚不可用,但能够术中监测种子分布,可以显著提高癌症控制效果。我们在此介绍这样的系统。
前列腺近距离放射治疗术中测量水肿需要将插入的放射性种子相对于前列腺进行定位。使用典型的非等中心 C 臂对种子进行重建,并将其输出到商业近距离放射治疗计划系统。在非等中心 C 臂上进行 3D 重建的技术障碍包括:依赖于体位的 C 臂校准;失真校正;C 臂图像的体位估计;种子重建;以及 C 臂到 TRUS 配准。
在具有 40-100 颗种子的精密加工硬体模和具有 45-87 颗种子的软组织体模中,我们正确重建了种子植入物的形状,平均 3D 精度分别为 0.35 毫米和 0.24 毫米。在一项针对六名患者(计划种植 48-82 颗种子)的国防部第一阶段临床试验中,我们实现了种子分布和剂量学的术中监测,并通过在六名入组患者中平均插入超过四颗额外的种子(最少 1 颗;最多 9 颗)来纠正剂量不均匀性。此外,在每个患者中,系统自动检测到由于水肿引起的术中种子迁移(平均 3.84 毫米,标准差 2.13 毫米,最大 16.19 毫米)。
所提出的系统是第一种能够在任何典型的非等中心 C 臂上进行术中检测水肿(并随后进行重新优化)的系统,对现有临床设备的额外成本可忽略不计。它实现了更均匀的种子分布,并有可能影响临床实践的范式转变。目前正在进行大规模研究和商业化。