Inui Yoshitaka, Ichihara Takashi, Uno Masaki, Ishiguro Masanobu, Ito Kengo, Kato Katsuhiko, Sakuma Hajime, Okazawa Hidehiko, Toyama Hiroshi
Department of Radiology, Fujita Health University School of Medicine, 1-98, Dengakugakubo, Kutsukake, Toyoake, Aichi, 470-1192, Japan.
Faculty of Radiological Technology, Fujita Health University School of Health Sciences, 1-98, Dengakugakubo, Kutsukake, Toyoake, Aichi, 470-1192, Japan.
Ann Nucl Med. 2018 Jun;32(5):311-318. doi: 10.1007/s12149-018-1248-x. Epub 2018 Mar 19.
Statistical image analysis of brain SPECT images has improved diagnostic accuracy for brain disorders. However, the results of statistical analysis vary depending on the institution even when they use a common normal database (NDB), due to different intrinsic spatial resolutions or correction methods. The present study aimed to evaluate the correction of spatial resolution differences between equipment and examine the differences in skull bone attenuation to construct a common NDB for use in multicenter settings.
The proposed acquisition and processing protocols were those routinely used at each participating center with additional triple energy window (TEW) scatter correction (SC) and computed tomography (CT) based attenuation correction (CTAC). A multicenter phantom study was conducted on six imaging systems in five centers, with either single photon emission computed tomography (SPECT) or SPECT/CT, and two brain phantoms. The gray/white matter I-123 activity ratio in the brain phantoms was 4, and they were enclosed in either an artificial adult male skull, 1300 Hounsfield units (HU), a female skull, 850 HU, or an acrylic cover. The cut-off frequency of the Butterworth filters was adjusted so that the spatial resolution was unified to a 17.9 mm full width at half maximum (FWHM), that of the lowest resolution system. The gray-to-white matter count ratios were measured from SPECT images and compared with the actual activity ratio. In addition, mean, standard deviation and coefficient of variation images were calculated after normalization and anatomical standardization to evaluate the variability of the NDB.
The gray-to-white matter count ratio error without SC and attenuation correction (AC) was significantly larger for higher bone densities (p < 0.05). The count ratio error with TEW and CTAC was approximately 5% regardless of bone density. After adjustment of the spatial resolution in the SPECT images, the variability of the NDB decreased and was comparable to that of the NDB without correction.
The proposed protocol showed potential for constructing an appropriate common NDB from SPECT images with SC, AC and spatial resolution compensation.
脑单光子发射计算机断层扫描（SPECT）图像的统计图像分析提高了脑部疾病的诊断准确性。然而，即使使用共同的正常数据库（NDB），由于内在空间分辨率或校正方法不同，统计分析结果在不同机构间仍存在差异。本研究旨在评估设备间空间分辨率差异的校正，并检查颅骨衰减差异，以构建适用于多中心环境的共同NDB。
拟采用的采集和处理方案是各参与中心常规使用的方案，并额外进行三能窗（TEW）散射校正（SC）和基于计算机断层扫描（CT）的衰减校正（CTAC）。在五个中心的六个成像系统上进行了多中心体模研究，这些系统包括单光子发射计算机断层扫描（SPECT）或SPECT/CT，以及两个脑体模。脑体模中灰质/白质碘-123活度比为4，它们被包裹在人工成年男性颅骨（1300亨氏单位[HU]）、女性颅骨（850 HU）或丙烯酸外壳中。调整巴特沃斯滤波器的截止频率，使空间分辨率统一到最低分辨率系统的17.9毫米半高宽（FWHM）。从SPECT图像测量灰质与白质计数比，并与实际活度比进行比较。此外，在归一化和解剖标准化后计算均值、标准差和变异系数图像，以评估NDB的变异性。
对于较高骨密度，无SC和衰减校正（AC）时灰质与白质计数比误差显著更大（p < 0.05）。无论骨密度如何，TEW和CTAC时的计数比误差约为5%。在调整SPECT图像的空间分辨率后，NDB的变异性降低，与未校正的NDB相当。
所提出的方案显示了通过SC、AC和空间分辨率补偿从SPECT图像构建合适的共同NDB的潜力。
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