Chouraqui P, Livschitz S, Sharir T, Wainer N, Wilk M, Moalem I, Baron J
The Heart Institute, Chaim Sheba Medical Center, Tel Hashomer, and The Sackler School of Medicine, Tel Aviv University, Israel.
J Nucl Cardiol. 1998 Jul-Aug;5(4):369-77. doi: 10.1016/s1071-3581(98)90142-8.
Image artifacts caused by nonuniform photon attenuation are a source of error in interpretation of images during myocardial perfusion single photon emission computed tomography (SPECT). A newly introduced attenuation correction method was evaluated for improvement in image homogeneity during 201Tl SPECT. The method was assessed with a cardiac phantom and in examinations of 42 patients (29 men) with a low likelihood of coronary disease.
Simultaneous transmission-emission SPECT was performed with a moving collimated 153Gd line source synchronized with a moving electronic acquisition window for transmission imaging and a novel variable-width electronic exclusion window for emission imaging designed to avoid transmission-to-emission cross talk. The resulting uncorrected and corrected polar maps were analyzed visually and divided into 31 segments for quantitative analysis. Visual analysis of the color-coded mean polar maps showed clear improvement in homogeneity after correction among the phantom, male patients, female patients, and 42 patients combined at stress and redistribution. The male and female mean polar maps showed very little differences in regional count distribution after correction. Quantitative analysis of the mean polar maps showed the following mean segmental counts (%SD) before and after attenuation correction: phantom 88 (9) to 90 (7.5), P = .00005; men at stress 83 (10) to 88 (6), P = .0007, and at redistribution 84 (8) to 88 (6), P = .01; women at stress 86 (7) to 90 (5), P = .0002, and at redistribution 87 (5) to 88 (7), P = .3; patients combined at stress 84 (8) to 88 (6), P = .0004, and at redistribution 85 (7) to 87 (7), P = .03. Inferior/anterior count ratio for men at stress increased after correction from 0.82 to 0.99 and septal/lateral count ratio from 0.94 to 1.02. Inferior/anterior count ratio for men at redistribution increased from 0.86 to 1.06 and septal/lateral count ratio from 0.97 to 1.04. Inferior/anterior count ratio for women at stress increased from 0.95 to 1.03 and septal/lateral count ratio from 0.93 to 1.00. Inferior/anterior count ratio for women at redistribution increased from 1.04 to 1.10, and septal/lateral count ratio decreased from 1.02 to 1.00.
Improvement in image homogeneity was demonstrated with this attenuation correction method with a cardiac phantom and for patients with low likelihood of coronary artery disease. The slight relative increase in inferior wall counts at redistribution was most likely caused by scatter from the relatively higher liver activity compared with the situation during stress and emphasizes the need for scatter correction. The close similarity in count distribution for the mean male and female polar maps supports use of a sex-independent normal database for quantitative analysis. The reduced variation in corrected images from patient to patient implies increased accuracy for detection of myocardial defects.
在心肌灌注单光子发射计算机断层扫描（SPECT）过程中，由光子衰减不均匀引起的图像伪影是图像解读误差的一个来源。对一种新引入的衰减校正方法进行了评估，以改善铊-201 SPECT期间的图像均匀性。该方法在心脏模型以及42例冠心病可能性较低的患者（29名男性）检查中进行了评估。
采用同步传输-发射SPECT，使用与移动电子采集窗口同步的移动准直153钆线源进行传输成像，并采用一种新型可变宽度电子排除窗口进行发射成像，以避免传输-发射串扰。对所得的未校正和校正后的极坐标图进行视觉分析，并将其分为31个节段进行定量分析。对彩色编码的平均极坐标图的视觉分析显示，在校正后，模型、男性患者、女性患者以及42例患者在负荷和再分布时的图像均匀性均有明显改善。校正后，男性和女性的平均极坐标图在区域计数分布上差异很小。对平均极坐标图的定量分析显示，衰减校正前后的平均节段计数（%标准差）如下：模型，88（9）至90（7.5），P = 0.00005；男性负荷时，83（10）至88（6），P = 0.0007，再分布时，84（8）至88（6），P = 0.01；女性负荷时，86（7）至90（5），P = 0.0002，再分布时，87（5）至88（7），P = 0.3；患者负荷时合并，84（8）至88（6），P = 0.0004，再分布时，85（7）至87（7），P = 于0.03。男性负荷时下壁/前壁计数比校正后从0.82增加到0.99，间隔/侧壁计数比从0.94增加到1.02。男性再分布时下壁/前壁计数比从0.86增加到1.06，间隔/侧壁计数比从0.97增加到1.04。女性负荷时下壁/前壁计数比从0.95增加到1.03，间隔/侧壁计数比从0.93增加到1.00。女性再分布时下壁/前壁计数比从1.04增加到1.10，间隔/侧壁计数比从1.02降低到1.00。
这种衰减校正方法在心脏模型以及冠心病可能性较低的患者中显示出图像均匀性的改善。再分布时下壁计数的轻微相对增加最可能是由于与负荷时相比肝脏活性相对较高导致的散射所致，这强调了散射校正的必要性。男性和女性平均极坐标图计数分布的密切相似性支持使用与性别无关的正常数据库进行定量分析。患者间校正后图像变化的减少意味着心肌缺损检测的准确性提高。
