Meng Huanna, Sun Qingting, Fan Yihan, Zhao Yuhao, Wang Jing, Wang Lingling, Liang Baohui
School of Medical Imaging, Bengbu Medical University, 2600 Donghai Road, Bengbu 233000, People's Republic of China.
Department of Radiology, The First Affiliated Hospital of Bengbu Medical University, No. 287 Changhuai Road, Bengbu Anhui 233004, People's Republic of China.
J Radiol Prot. 2025 Sep 22;45(3). doi: 10.1088/1361-6498/ae064f.
This study aimed to evaluate the influence of three reference baselines-specifically, supraorbitometal baseline (SOML), orbitometal baseline (OMBL), and Reid's baseline (RBL) on size-specific dose estimate (SSDE) in head computed tomography (CT), addressing limitations of conventional dose metrics that neglect baseline-dependent anatomical variations. Experiments were performed on a GE LightSpeed VCT scanner. The positioning of the head phantom corresponding to the SOML, OMBL, and RBL baselines was achieved by tilting the CT gantry and elevating the phantom. Using automatic tube current modulation, 48 imaging datasets were acquired through both axial and helical scans. Thermoluminescent dosimeters (TLDs) were employed to measure the eye lens dose. The SSDE() was calculated for each slice, with the central slice SSDE values denoted as SSDEcen. The volume-averaged SSDE (SSDEgro) was derived by weighted integration of the former, enabling comparative analysis of radiation dose parameters across groups. In both axial and helical scanning modes, the SOML group demonstrated lower CTDI(), SSDEcen, and SSDEgro compared to the OMBL and RBL group. When the gantry tilted along SOML, SSDEgro values reduced by 20.67% (vs. RBL-phantom elevation) to 32.19% (vs. OMBL-gantry tilt). Within a single scan, SSDEgro values were consistently less than the corresponding CTDI(), with a maximum reduction of 10.71%. Additionally, TLD measurements revealed that the eye lens radiation dose varied between 47.48 and 87.91 mGy, with the lowest dose (47.48 mGy) achieved in SOML-based axial scans using gantry tilt. This study demonstrates that the choice of reference baseline influences SSDE values in head CT imaging. Furthermore, SSDE effectively corrects the overestimation of the actual radiation dose by CTDI. Based on the findings, we recommend adopting the SOML as the reference baseline in clinical practice, which reduces radiation exposure during head CT examinations and optimises ocular radiation protection.
本研究旨在评估三种参考基线，即眶上金属基线（SOML）、眶金属基线（OMBL）和里德基线（RBL）对头部计算机断层扫描（CT）中特定尺寸剂量估计（SSDE）的影响，以解决传统剂量指标忽视基线相关解剖变异的局限性。实验在GE LightSpeed VCT扫描仪上进行。通过倾斜CT机架和抬高体模实现头部体模对应SOML、OMBL和RBL基线的定位。使用自动管电流调制，通过轴向和螺旋扫描获取了48个成像数据集。采用热释光剂量计（TLD）测量晶状体剂量。计算每个层面的SSDE()，中心层面的SSDE值记为SSDEcen。通过对前者进行加权积分得出体积平均SSDE（SSDEgro），从而能够对各组的辐射剂量参数进行比较分析。在轴向和螺旋扫描模式下，与OMBL和RBL组相比，SOML组的CTDI()、SSDEcen和SSDEgro均较低。当机架沿SOML倾斜时，SSDEgro值降低了20.67%（与RBL-体模抬高相比）至32.19%（与OMBL-机架倾斜相比）。在单次扫描中，SSDEgro值始终小于相应的CTDI()，最大降低了10.71%。此外，TLD测量显示晶状体辐射剂量在47.48至87.91 mGy之间变化，在基于SOML的轴向扫描中使用机架倾斜时获得了最低剂量（47.48 mGy）。本研究表明，参考基线的选择会影响头部CT成像中的SSDE值。此外，SSDE有效地纠正了CTDI对实际辐射剂量的高估。基于这些发现，我们建议在临床实践中采用SOML作为参考基线，这可减少头部CT检查期间的辐射暴露并优化眼部辐射防护。
