Shiga Tohru, Morimoto Yuichi, Kubo Naoki, Katoh Norio, Katoh Chietsugu, Takeuchi Wataru, Usui Reiko, Hirata Kenji, Kojima Shinichi, Umegaki Kikuo, Shirato Hiroki, Tamaki Nagara
Department of Nuclear Medicine, School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan.
J Nucl Med. 2009 Jan;50(1):148-55. doi: 10.2967/jnumed.108.054833. Epub 2008 Dec 17.
An autoradiography method revealed intratumoral inhomogeneity in various solid tumors. It is becoming increasingly important to estimate intratumoral inhomogeneity. However, with low spatial resolution and high scatter noise, it is difficult to detect intratumoral inhomogeneity in clinical settings. We developed a new PET system with CdTe semiconductor detectors to provide images with high spatial resolution and low scatter noise. Both phantom images and patients' images were analyzed to evaluate intratumoral inhomogeneity.
This study was performed with a cold spot phantom that had 6-mm-diameter cold sphenoid defects, a dual-cylinder phantom with an adjusted concentration of 1:2, and an "H"-shaped hot phantom. These were surrounded with water. Phantom images and (18)F-FDG PET images of patients with nasopharyngeal cancer were compared with conventional bismuth germanate PET images. Profile curves for the phantoms were measured as peak-to-valley ratios to define contrast. Intratumoral inhomogeneity and tumor edge sharpness were evaluated on the images of the patients.
The contrast obtained with the semiconductor PET scanner (1.53) was 28% higher than that obtained with the conventional scanner (1.20) for the 6-mm-diameter cold sphenoid phantom. The contrast obtained with the semiconductor PET scanner (1.43) was 27% higher than that obtained with the conventional scanner (1.13) for the dual-cylinder phantom. Similarly, the 2-mm cold region between 1-mm hot rods was identified only by the new PET scanner and not by the conventional scanner. The new PET scanner identified intratumoral inhomogeneity in more detail than the conventional scanner in 6 of 10 patients. The tumor edge was sharper on the images obtained with the new PET scanner than on those obtained with the conventional scanner.
These phantom and clinical studies suggested that this new PET scanner has the potential for better identification of intratumoral inhomogeneity, probably because of its high spatial resolution and low scatter noise.
放射自显影方法揭示了各种实体瘤内的肿瘤内不均匀性。估计肿瘤内不均匀性变得越来越重要。然而，由于空间分辨率低和散射噪声高，在临床环境中难以检测肿瘤内不均匀性。我们开发了一种带有碲化镉半导体探测器的新型PET系统，以提供具有高空间分辨率和低散射噪声的图像。对体模图像和患者图像进行分析，以评估肿瘤内不均匀性。
本研究使用了具有6毫米直径冷蝶鞍缺损的冷区体模、浓度调整为1:2的双圆柱体体模和“H”形热体模。这些体模周围均为水。将这些体模图像和鼻咽癌患者的（18）F-FDG PET图像与传统的锗酸铋PET图像进行比较。测量体模的轮廓曲线作为峰谷比来定义对比度。在患者图像上评估肿瘤内不均匀性和肿瘤边缘清晰度。
对于直径6毫米的冷蝶鞍体模，半导体PET扫描仪获得的对比度（1.53）比传统扫描仪（1.20）高28%。对于双圆柱体体模，半导体PET扫描仪获得的对比度（1.43）比传统扫描仪（1.13）高27%。同样，仅新型PET扫描仪能识别1毫米热棒之间2毫米的冷区，而传统扫描仪无法识别。新型PET扫描仪比传统扫描仪更详细地识别了10例患者中6例的肿瘤内不均匀性。新型PET扫描仪获得的图像上肿瘤边缘比传统扫描仪获得的图像更清晰。
这些体模和临床研究表明，这种新型PET扫描仪有可能更好地识别肿瘤内不均匀性，这可能是由于其高空间分辨率和低散射噪声。
