Rohrbach Daniel, Wodlinger Brian, Wen Jerrold, Mamou Jonathan, Feleppa Ernest
Lizzi Center for Biomedical Engineering, Riverside Research, New York, NY 10038, USA.
Exact Imaging, Markham, Ontario, Canada.
Ultrasound Med Biol. 2018 Jul;44(7):1341-1354. doi: 10.1016/j.ultrasmedbio.2018.02.014. Epub 2018 Apr 4.
Currently, biopsies guided by transrectal ultrasound (TRUS) are the only method for definitive diagnosis of prostate cancer. Studies by our group suggest that quantitative ultrasound (QUS) could provide a more sensitive means of targeting biopsies and directing focal treatments to cancer-suspicious regions in the prostate. Previous studies have utilized ultrasound signals at typical clinical frequencies, i.e., in the 6-MHz range. In the present study, a 29-MHz, TRUS, micro-ultrasound system and transducer (ExactVu micro-ultrasound, Exact Imaging, Markham, Canada) was used to acquire radio frequency data from 163 patients immediately before 12-core biopsy procedures, comprising 1956 cores. These retrospective data are a subset of data acquired in an ongoing, multisite, 2000-patient, randomized, clinical trial (clinicaltrials.gov NCT02079025). Spectrum-based QUS estimates of effective scatter diameter (ESD), effective acoustic concentration (EAC), midband (M), intercept (I) and slope (S) as well as envelope statistics employing a Nakagami distribution were used to train linear discriminant classifiers (LDCs) and support vector machines (SVMs). Classifier performance was assessed using area-under-the-curve (AUC) values obtained from receiver operating characteristic (ROC) analyses with 10-fold cross validation. A combination of ESD and EAC parameters resulted in an AUC value of 0.77 using a LDC. When Nakagami-µ or prostate-specific antigen (PSA) values were added as features, the AUC value increased to 0.79. SVM produced an AUC value of 0.77, using a combination of envelope and spectral QUS estimates. The best classification produced an AUC value of 0.81 using an LDC when combining envelope statistics, PSA, ESD and EAC. In a previous study, B-mode-based scoring and evaluation using the PRI-MUS protocol produced a maximal AUC value of 0.74 for higher Gleason-score values (GS >7) when read by an expert. Our initial results with AUC values of 0.81 are very encouraging for developing a new, predominantly user-independent, prostate-cancer, risk-assessing tool.
目前，经直肠超声（TRUS）引导下的活检是前列腺癌确诊的唯一方法。我们团队的研究表明，定量超声（QUS）可以提供一种更敏感的方法来靶向活检，并将局部治疗引导至前列腺中可疑癌症的区域。以往的研究使用的是典型临床频率（即6兆赫兹范围内）的超声信号。在本研究中，使用了一个29兆赫兹的TRUS微型超声系统和换能器（ExactVu微型超声，Exact Imaging，加拿大万锦市），在12针活检程序前立即从163名患者身上采集射频数据，共1956针。这些回顾性数据是一项正在进行的、多中心、2000例患者的随机临床试验（clinicaltrials.gov NCT02079025）所采集数据的一个子集。基于频谱的QUS对有效散射直径（ESD）、有效声浓度（EAC）、中频（M）、截距（I）和斜率（S）的估计，以及采用 Nakagami分布的包络统计量，用于训练线性判别分类器（LDC）和支持向量机（SVM）。使用通过10倍交叉验证的接收器操作特征（ROC）分析获得的曲线下面积（AUC）值来评估分类器性能。使用LDC时，ESD和EAC参数的组合产生的AUC值为0.77。当添加Nakagami-µ或前列腺特异性抗原（PSA）值作为特征时，AUC值增加到0.79。使用包络和频谱QUS估计值的组合，SVM产生的AUC值为0.77。当结合包络统计量、PSA、ESD和EAC时，使用LDC进行的最佳分类产生的AUC值为0.81。在之前的一项研究中，由专家解读时，基于B模式并使用PRI-MUS协议进行评分和评估，对于较高Gleason评分值（GS>7）产生的最大AUC值为0.74。我们最初得到的AUC值为0.81的结果对于开发一种新的、主要独立于用户的前列腺癌风险评估工具非常令人鼓舞。
