Sharma Punit, Sharma Shekhar, Ballal Sanjana, Bal Chandrasekhar, Malhotra Arun, Kumar Rakesh
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Nucl Med Commun. 2012 Sep;33(9):926-32. doi: 10.1097/MNM.0b013e328355b6d5.
To assess the patient radiation dose during routine clinical single-photon emission computed tomography-computed tomography (SPECT-CT) and measure the increase as compared with SPECT alone.
Data pertaining to 357 consecutive patients who had undergone radioisotope imaging along with SPECT-CT of a selected volume were retrospectively evaluated. Dose of the injected radiopharmaceutical (MBq) was noted, and the effective dose (mSv) was calculated as per International Commission on Radiological Protection (ICRP) guidelines. The volume-weighted computed tomography dose index (CTDIvol) and dose length product of the CT were also assessed using standard phantoms. The effective dose (mSv) due to CT was calculated as the product of dose length product and a conversion factor depending on the region of investigation, using ICRP guidelines. The dose due to CT was compared among different investigations. The increase in effective dose was calculated as CT dose expressed as a percentage of radiopharmaceutical dose.
The per-patient CT effective dose for different studies varied between 0.06 and 11.9 mSv. The mean CT effective dose was lowest for 99mTc-ethylene cysteine dimer brain SPECT-CT (0.9 ± 0.7) and highest for 99mTc-methylene diphosphonate bone SPECT-CT (4.2 ± 2.8). The increase in radiation dose (SPECT-CT vs. SPECT) varied widely (2.3-666.4% for 99mTc-tracers and 0.02-96.2% for 131I-tracers). However, the effective dose of CT in SPECT-CT was less than the values reported for conventional CT examinations of the same regions.
Addition of CT to nuclear medicine imaging in the form of SPECT-CT increases the radiation dose to the patient, with the effective dose due to CT exceeding the effective dose of RP in many instances. Hence, appropriate utilization and optimization of the protocols of SPECT-CT is needed to maximize benefit to patients.
评估常规临床单光子发射计算机断层扫描 - 计算机断层扫描（SPECT - CT）期间患者的辐射剂量，并测量与单独的SPECT相比剂量的增加情况。
回顾性评估了357例连续接受放射性核素成像及选定部位SPECT - CT检查患者的数据。记录注入放射性药物的剂量（MBq），并根据国际放射防护委员会（ICRP）指南计算有效剂量（mSv）。还使用标准体模评估了CT的体积加权计算机断层扫描剂量指数（CTDIvol）和剂量长度乘积。根据ICRP指南，将CT产生的有效剂量（mSv）计算为剂量长度乘积与取决于检查部位的转换因子的乘积。比较不同检查中CT产生的剂量。将有效剂量的增加计算为CT剂量占放射性药物剂量的百分比。
不同研究中每位患者的CT有效剂量在0.06至11.9 mSv之间变化。99mTc - 乙烯半胱氨酸二聚体脑SPECT - CT的平均CT有效剂量最低（0.9±0.7），99mTc - 亚甲基二膦酸盐骨SPECT - CT的平均CT有效剂量最高（4.2±2.8）。辐射剂量的增加（SPECT - CT与SPECT相比）差异很大（99mTc示踪剂为2.3 - 666.4%，131I示踪剂为0.02 - 96.2%）。然而，SPECT - CT中CT的有效剂量低于相同部位传统CT检查报告的值。
以SPECT - CT形式在核医学成像中添加CT会增加患者的辐射剂量，在许多情况下CT产生的有效剂量超过放射性药物的有效剂量。因此，需要合理利用和优化SPECT - CT方案，以使患者受益最大化。
