Takahashi Yasuyuki, Murase Kenya, Mochizuki Teruhito, Higashino Hiroshi, Sugawara Yoshifumi, Kinda Akiyoshi
Department of Medical Engineering, Division of Allied Health Sciences, Osaka University Graduate School of Medicine.
Ann Nucl Med. 2004 Apr;18(2):137-43. doi: 10.1007/BF02985104.
One of the main factors contributing to the accuracy of attenuation correction for SPECT imaging using transmission computed tomography (TCT) with an external gamma-ray source is the radionuclide count. To reduce deterioration of TCT images due to inadequate radionuclide counts, a correction method, segmented attenuation correction (SAC), in which TCT data are transformed into several components (segments) such as water, lungs and spine, providing a satisfactory attenuation correction map with less counts, has been developed. The purpose of this study was to examine the usefulness of SAC for myocardial SPECT with attenuation correction.
A myocardial phantom filled with Tc-99m was scanned with a triple headed SPECT system, equipped with one cardiac fan beam collimator for TCT and two parallel hole collimators for ECT. As an external gamma-ray source for TCT, 740 MBq of Tc-99m was also used. Since Tc-99m was also used for ECT, the TCT and ECT data were acquired separately. To make radionuclide counts, the TCT data were acquired in the sequential repetition mode, in which a 3-min-rotation was repeated 7 times followed by a 10-min-rotation 4 times (a total of 61 minutes). The TCT data were reconstructed by adding some of these rotations to make TCT maps with various radionuclide counts. Three types of SAC were used: (a) 1-segment SAC in which the body structure was regarded as water, (b) 2-segment SAC, in which the body structure was regarded as water and lungs, and (c) 3-segment SAC, in which the body structure was regarded as water, lungs and spine. We compared corrected images obtained with non-segmentation methods, and with 1- to 3-segment SACs. We also investigated the influence of radionuclide counts of TCT (3, 6, 9, 12, 15, 18, 21, 31, 41, 51, 61 min acquisition) on the accuracy of the attenuation correction.
Either 1-segment or 2-segment SAC was sufficient to correct the attenuation. When non-segmentation TCT attenuation methods were used, rotations of at least 31 minutes were required to obtain sufficiently large counts for TCT. When the 3-segment SAC was used, the minimal acquisition time for a satisfactory TCT map was 7 min.
The 3-segment SAC was effective for attenuation correction, requiring fewer counts (about 1/5 of the value for non-segmentation TCT), or less radiation for TCT.
使用外部伽马射线源的透射计算机断层扫描（TCT）进行单光子发射计算机断层扫描（SPECT）成像时，影响衰减校正准确性的主要因素之一是放射性核素计数。为减少因放射性核素计数不足导致的TCT图像质量下降，已开发出一种校正方法，即分段衰减校正（SAC），该方法将TCT数据转换为水、肺和脊柱等几个成分（段），从而以较少的计数提供令人满意的衰减校正图。本研究的目的是检验SAC在心肌SPECT衰减校正中的实用性。
用一个配备有用于TCT的心脏扇形束准直器和两个用于ECT的平行孔准直器的三头SPECT系统对填充有锝-99m的心肌模型进行扫描。作为TCT的外部伽马射线源，也使用了740MBq的锝-99m。由于锝-99m也用于ECT，因此TCT和ECT数据是分别采集的。为了进行放射性核素计数，TCT数据以顺序重复模式采集，即3分钟旋转重复7次，随后10分钟旋转重复4次（共61分钟）。通过添加这些旋转中的一些来重建TCT数据，以生成具有不同放射性核素计数的TCT图。使用了三种类型的SAC：（a）将身体结构视为水的1段SAC，（b）将身体结构视为水和肺的2段SAC，以及（c）将身体结构视为水、肺和脊柱的3段SAC。我们比较了用非分段方法以及1至3段SAC获得的校正图像。我们还研究了TCT的放射性核素计数（采集3、6、9、12、15、18、21、31、41、51、61分钟）对衰减校正准确性的影响。
1段或2段SAC足以校正衰减。当使用非分段TCT衰减方法时，至少需要31分钟的旋转才能获得足够多的TCT计数。当使用3段SAC时，获得令人满意的TCT图的最短采集时间为7分钟。
3段SAC对衰减校正有效，所需计数较少（约为非分段TCT值的1/5），或TCT所需辐射较少。
Zotero 插件