Hashizume Kengo, Ichikawa Yasutaka, Tomita Yoya, Sakuma Hajime
Central Division of Radiology, Mie University Hospital, 2-174 Edobashi, Tsu, Mie 514-8507, Japan.
Department of Radiology, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507, Japan.
Phys Med. 2022 Dec;104:18-22. doi: 10.1016/j.ejmp.2022.10.022. Epub 2022 Nov 7.
To evaluate the effect of computed tomography (CT) tube voltage and CT density for CT-based attenuation correction (CTAC) on quantification of tracer uptake in single photon emission computed tomography (SPECT)/CT.
A cylindrical phantom contained 7 cylinders with diameter of 30 mm. The central cylinder and background part were filled with 17 kBq/ml of Tc-pertechnetate solution. Of the remaining 6 cylinders, one cylinder was filled with water and 5 cylinders were filled with each own different concentration of KHPO solution (120, 275, 450, 666, and 960 mg/cm) to simulate different bone densities. The 6 cylinders also contained Tc-pertechnetate solution with the same radioactivity concentration (207 kBq/ml). CT scans were performed with 4 different tube voltages of 80, 100, 120, and 140 kVp for CTAC. The radioactivity concentration in the 6 cylinders were measured on the SPECT images processed with 4 different attenuation coefficient maps derived from each tube voltage of CT images.
Compared with the water cylinder without KHPO solution, the measured radioactivity of the highest density cylinder (KHPO solution concentration: 960 mg/cm) was found to be overestimated by 3.3 % and 4.3 %, respectively, when the tube voltage was 120 kVp and 140 kVp (p = 0.022). The use of low-tube voltage, such as 80 kVp, has improved the quantitative accuracy of bone SPECT/CT.
SPECT quantitative evaluation of tracers in high-density objects tends to overestimate as tube voltage for CTAC increases. However, the overestimation in quantitative SPECT/CT evaluation in simulated bone area is less than 5% at most.
评估计算机断层扫描（CT）管电压及CT密度用于基于CT的衰减校正（CTAC）对单光子发射计算机断层扫描（SPECT）/CT中示踪剂摄取定量的影响。
一个圆柱形模体包含7个直径为30毫米的圆柱体。中央圆柱体和背景部分填充有17 kBq/ml的高锝酸盐溶液。其余6个圆柱体中，一个圆柱体填充水，5个圆柱体分别填充不同浓度的KHPO溶液（120、275、450、666和960 mg/cm）以模拟不同骨密度。这6个圆柱体也含有放射性浓度相同（207 kBq/ml）的高锝酸盐溶液。针对CTAC，采用80、100、120和140 kVp这4种不同管电压进行CT扫描。在由CT图像的各管电压得出的4种不同衰减系数图处理后的SPECT图像上测量这6个圆柱体中的放射性浓度。
与未含KHPO溶液的水圆柱体相比，当管电压为120 kVp和140 kVp时，最高密度圆柱体（KHPO溶液浓度：960 mg/cm）的测量放射性分别被高估了3.3%和4.3%（p = 0.022）。使用低管电压，如80 kVp，提高了骨SPECT/CT的定量准确性。
随着用于CTAC的管电压增加，高密度物体中示踪剂的SPECT定量评估往往会高估。然而，在模拟骨区域的SPECT/CT定量评估中，高估最多不超过5%。
