Centre for Research and Development, Uppsala University/Region Gävleborg, 801 88, Gävle, Sweden.
Department of Surgical Science, Uppsala University, 751 85, Uppsala, Sweden.
Eur Radiol. 2019 Aug;29(8):4315-4323. doi: 10.1007/s00330-018-5849-5. Epub 2018 Dec 17.
To evaluate the effect of patient size on radiation dose for standard CT (SD-CT), ultra-low-dose CT (ULD-CT) and two-view digital radiography (DR).
Dosimeters were distributed within the lungs of chest phantoms representing males of 65 kg and 82 kg (body mass indices 23 and 29). In contrast to SD-CT and DR which include automatic exposure control (AEC), the ULD scan employs a fixed mAs value. The phantoms were exposed to SD, ULD and DR while recording lung doses. Projected dose data were calculated from the phantoms. The resulting exposure settings were used in Monte Carlo programs to determine the effective dose for a standard-sized (BMI 24.2) adult male (170 cm/70 kg) and female (160 cm/59 kg). Patients previously examined by both ULD- and SD-CT were identified to determine post hoc size-specific dose estimates (SSDEs).
ULD-CT dose was inversely related to patient size; average lung doses summarised in terms of patient size BMI are 5.2/8.1 (SD-CT), 0.56/0.35 (ULD-CT) and 0.05/0.13 mGy (DR), while the effective doses for these techniques on a standard-sized male were 2.9, 0.16 and 0.03 mSv and 2.3, 0.247 and 0.024 mSv for a standard-sized female respectively. SSDEs for 15 patients (averages: BMI 26, range 18-37) averaged 5.5 mGy (3.6-10) for SD-CT and 0.35 mGy (0.42-0.27) for ULD-CT.
The effective doses for a standard-sized male and female examined by ULD-CT are (respectively) ~ 6%/~ 11% of SD-CT and ~ 5/~ 10 times higher than DR. ULD-CT gave a lower radiation dosage to larger patients than DR. AEC is warranted in ULD-CT for improved dose consistency.
• For standard-sized patients, ULD-CT dose level is ~ 6%/~ 11% of SD-CT, and ~ 5/~ 10 times higher than DR. For larger patients, ULD-CT is currently being used clinically at lower dose levels than DR. • Using ULD-CT should greatly reduce the risk of late effects from ionising radiation. • AEC in ULD-CT is desirable for increased consistency in patient dose.
评估患者体型对标准 CT（SD-CT）、超低剂量 CT（ULD-CT）和双视图数字射线照相术（DR）辐射剂量的影响。
将剂量计分布在代表 65 公斤和 82 公斤男性（体重指数 23 和 29）的胸部体模的肺部内。与包括自动曝光控制（AEC）的 SD-CT 和 DR 不同，ULD 扫描采用固定的 mAs 值。对 SD、ULD 和 DR 进行曝光，同时记录肺部剂量。从体模中计算出投影剂量数据。将得到的曝光设置用于蒙特卡罗程序，以确定标准体型（BMI 24.2）成年男性（170cm/70kg）和女性（160cm/59kg）的有效剂量。确定了先前接受 ULD-和 SD-CT 检查的患者的特定大小剂量估计值（SSDE）。
ULD-CT 剂量与患者体型呈反比；以患者体型 BMI 表示的平均肺部剂量分别为 5.2/8.1（SD-CT）、0.56/0.35（ULD-CT）和 0.05/0.13mGy（DR），而这些技术对标准体型男性的有效剂量分别为 2.9、0.16 和 0.03mSv 和 2.3、0.247 和 0.024mSv 为标准体型女性。15 名患者的 SSDE 平均值（BMI 26，范围 18-37）分别为 5.5mGy（3.6-10）用于 SD-CT 和 0.35mGy（0.42-0.27）用于 ULD-CT。
接受 ULD-CT 检查的标准体型男性和女性的有效剂量分别为 SD-CT 的6%/11%，而 DR 的~5 倍/10 倍。ULD-CT 给体型较大的患者带来的辐射剂量低于 DR。ULD-CT 中需要使用 AEC 以提高剂量一致性。
对于标准体型患者，ULD-CT 剂量水平约为 SD-CT 的6%/11%，是 DR 的~5 倍/10 倍。对于体型较大的患者，ULD-CT 目前在临床上以低于 DR 的剂量水平使用。
使用 ULD-CT 可大大降低电离辐射引起的晚期效应的风险。
ULD-CT 中需要 AEC，以提高患者剂量的一致性。
