Laboratory Lisa, University of Angers, Angers, France.
IEEE Trans Med Imaging. 2012 Oct;31(10):1875-88. doi: 10.1109/TMI.2012.2205267. Epub 2012 Jun 19.
Many numerical observers have been proposed in the framework of task-based approach for medical image quality assessment. However, the existing numerical observers are still limited in diagnostic tasks: the detection task has been largely studied, while the localization task concerning one signal has been little studied and the localization of multiple signals has not been studied yet. In addition, most existing numerical observers need a priori knowledge about all the parameters of the underdetection signals, while only a few of them need at least two signal parameters. In this paper, we propose a novel numerical observer called the perceptually relevant channelized joint observer (PCJO), which cannot only detect but also localize multiple signals with unknown amplitude, orientation, size and location. We validated the PCJO for predicting human observer task performance by conducting a clinically relevant free-response subjective experiment in which six radiologists (including two experts) had to detect and localize multiple sclerosis (MS) lesions on magnetic resonance (MR) images. By using the jackknife alternative free-response operating characteristic (JAFROC) as the figure of merit (FOM), the detection-localization task performance of the PCJO was evaluated and then compared to that of the radiologists and two other numerical observers--channelized hotelling observer (CHO) and Goossenss CHO for detecting asymmetrical signals with random orientations. Overall, the results show that the PCJO performance was closer to that of the experts than to that of the other radiologists. The JAFROC1 FOMs of the PCJO (around 0.75) are not significantly different from those of the two experts (0.7672 and 0.7110), while the JAFROC1 FOMs of the numerical observers mentioned above (always over 0.84) outperform those of the experts. This indicates that the PCJO is a promising method for predicting radiologists' performance in the joint detection-localization task.
许多基于任务的医学图像质量评估方法框架中都提出了许多数值观测器。然而，现有的数值观测器在诊断任务中仍然存在局限性：检测任务得到了广泛研究，而有关单个信号的定位任务研究较少，多个信号的定位尚未研究。此外，大多数现有的数值观测器需要对所有检测信号的参数都有先验知识，而只有少数几个需要至少两个信号参数。在本文中，我们提出了一种称为感知相关通道联合观测器（PCJO）的新型数值观测器，它不仅可以检测，还可以定位具有未知幅度、方向、大小和位置的多个信号。我们通过进行一项具有临床相关性的自由响应主观实验来验证 PCJO 对预测人类观察者任务性能的能力，在该实验中，六名放射科医生（包括两名专家）必须在磁共振（MR）图像上检测和定位多发性硬化症（MS）病变。通过使用刀切替代自由响应操作特性（JAFROC）作为衡量标准（FOM），评估了 PCJO 的检测-定位任务性能，然后将其与放射科医生和其他两个数值观测器（通道化霍特林观测器（CHO）和 Goossenss CHO）的性能进行了比较，用于检测具有随机方向的不对称信号。总体而言，结果表明 PCJO 的性能比其他放射科医生更接近专家的表现。PCJO 的 JAFROC1 FOM（约 0.75）与两位专家的 FOM（0.7672 和 0.7110）没有显著差异，而上述数值观测器的 JAFROC1 FOM（始终高于 0.84）则优于专家的 FOM。这表明 PCJO 是预测放射科医生在联合检测-定位任务中表现的一种很有前途的方法。
