Department of Medical Biophysics, The University of Western Ontario, London, Canada, N6A 3K7.
Department of Medical Imaging, The University of Western Ontario, London, Canada, N6A 3K7.
Med Phys. 2018 Mar;45(3):1018-1028. doi: 10.1002/mp.12769. Epub 2018 Feb 16.
Magnetic resonance imaging (MRI)-targeted, three-dimensional (3D) transrectal ultrasound (TRUS)-guided prostate biopsy aims to reduce the 21-47% false-negative rate of clinical two-dimensional (2D) TRUS-guided systematic biopsy, but continues to yield false-negative results. This may be improved via needle target optimization, accounting for guidance system errors and image registration errors. As an initial step toward the goal of optimized prostate biopsy targeting, we investigated how needle delivery error impacts tumor sampling probability for two targeting strategies.
We obtained MRI and 3D TRUS images from 49 patients. A radiologist and radiology resident assessed these MR images and contoured 81 suspicious regions, yielding tumor surfaces that were registered to 3D TRUS. The biopsy system's root-mean-squared needle delivery error (RMSE) and systematic error were modeled using an isotropic 3D Gaussian distribution. We investigated two different prostate tumor-targeting strategies using (a) the tumor's centroid and (b) a ring in the lateral-elevational plane. For each simulation, targets were spaced at equal arc lengths on a ring with radius equal to the systematic error magnitude. A total of 1000 biopsy simulations were conducted for each tumor, with RMSE and systematic error magnitudes ranging from 1 to 6 mm. The difference in median tumor sampling probability and probability of obtaining a 50% core involvement was determined for ring vs centroid targeting.
Our simulation results indicate that ring targeting outperformed centroid targeting in situations where systematic error exceeds RMSE. In these instances, we observed statistically significant differences showing 1-32% improvement in sampling probability due to ring targeting. Likewise, we observed statistically significant differences showing 1-39% improvement in 50% core involvement probability due to ring targeting.
Our results suggest that the optimal targeting scheme for prostate biopsy depends on the relative levels of systematic and random errors in the system. Where systematic error dominates, a ring-targeting scheme may yield improved probability of tumor sampling. The findings presented in this paper may be used to aid in target selection strategies for clinicians performing targeted prostate biopsies on any MRI targeted, 3D TRUS-guided biopsy system and could support earlier diagnosis of prostate cancer while it remains localized to the gland and curable.
磁共振成像（MRI）靶向、三维（3D）经直肠超声（TRUS）引导的前列腺活检旨在降低临床二维（2D）TRUS 引导系统活检的 21%至 47%的假阴性率，但仍会出现假阴性结果。通过优化针的靶向，可以改善这种情况，从而考虑到引导系统误差和图像配准误差。作为优化前列腺活检靶向目标的初始步骤，我们研究了两种靶向策略下针输送误差如何影响肿瘤采样概率。
我们从 49 名患者中获得了 MRI 和 3D TRUS 图像。一名放射科医生和一名放射科住院医师评估了这些 MRI 图像，并描绘了 81 个可疑区域，生成了与 3D TRUS 相对应的肿瘤表面。使用各向同性 3D 高斯分布对活检系统的均方根针输送误差（RMSE）和系统误差进行建模。我们使用（a）肿瘤的质心和（b）侧位平面中的环，研究了两种不同的前列腺肿瘤靶向策略。对于每种模拟，在半径等于系统误差大小的环上以相等的弧长间隔目标。对于每个肿瘤，共进行了 1000 次活检模拟，RMSE 和系统误差大小范围为 1 至 6 毫米。对于环与质心靶向，确定了肿瘤采样概率中位数和获得 50%核心受累概率的差异。
我们的模拟结果表明，在系统误差超过 RMSE 的情况下，环靶向优于质心靶向。在这些情况下，我们观察到由于环靶向而导致采样概率提高 1%至 32%的具有统计学意义的差异。同样，我们观察到由于环靶向而导致 50%核心受累概率提高 1%至 39%的具有统计学意义的差异。
我们的结果表明，前列腺活检的最佳靶向方案取决于系统中系统误差和随机误差的相对水平。在系统误差占主导地位的情况下，环靶向方案可能会提高肿瘤采样的概率。本文提出的研究结果可用于辅助执行任何 MRI 靶向、3D TRUS 引导活检系统的靶向前列腺活检的临床医生选择目标策略，并支持在癌症仍局限于腺体且可治愈时更早地诊断前列腺癌。
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