Buckley Jarryd G, Wilkinson Dean, Malaroda Alessandra, Metcalfe Peter
School of Physics, Centre for Medical and Radiation Physics, University of Wollongong, Wollongong, Australia.
Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, Australia.
J Appl Clin Med Phys. 2018 Jan;19(1):174-183. doi: 10.1002/acm2.12239. Epub 2017 Dec 19.
Four methodologies were evaluated for quantifying kilovoltage cone-beam computed tomography (CBCT) dose: the Cone-Beam Dose Index (CBDI), IAEA Report 5 recommended methodology (IAEA), the AAPM Task Group 111 methodology (TG111), and the current dose metric; the Computed Tomography Dose Index (CTDI) on two commercial Varian cone-beam CT imaging systems; the Clinac iX On-Board Imager (OBI); and the TrueBeam X-ray Imaging system (XI). The TG111 methodology measured the highest overall dose (21.199 ± 0.035 mGy OBI and 22.420 ± 0.002 XI for pelvis imaging) due to the full scatter of the TG111 phantom and was within 5% of CTDI measurements taken using a full scatter TG111 phantom and 30-cm film strips. CBDI measured the second highest overall dose, within 10% of the TG111, with IAEA measuring the third highest dose. For head CBCT protocols, CBDI measured the highest dose, followed by IAEA. The CTDI method measured lowest across all scan modes highlighting its limitations for CBCT dosimetry. The XI imaging system delivered lower doses for head and thorax scan modes and similar doses to the OBI system for pelvis scan modes due to additional beam hardening filtration in the XI system. The TG111 method measured the highest dose in the center of a CBCT scan during image guidance procedures; however, CBDI provided a good approximation to TG111 with existing CTDI equipment and may be more applicable clinically.
对四种用于量化千伏级锥形束计算机断层扫描（CBCT）剂量的方法进行了评估：锥形束剂量指数（CBDI）、国际原子能机构（IAEA）报告5推荐的方法（IAEA）、医学物理师协会（AAPM）任务组111方法（TG111）以及当前剂量指标；计算机断层扫描剂量指数（CTDI），在两台瓦里安商用锥形束CT成像系统上进行测量；直线加速器iX机载成像仪（OBI）；以及真体束X射线成像系统（XI）。由于TG111体模的全散射，TG111方法测量的总体剂量最高（骨盆成像时，OBI为21.199±0.035 mGy，XI为22.420±0.002），并且与使用全散射TG111体模和30厘米胶片条进行的CTDI测量值相差在5%以内。CBDI测量的总体剂量第二高，在TG111的10%以内，IAEA测量的剂量排第三。对于头部CBCT协议，CBDI测量的剂量最高，其次是IAEA。CTDI方法在所有扫描模式下测量的剂量最低，凸显了其在CBCT剂量测定方面的局限性。由于XI系统中额外的束硬化过滤，XI成像系统在头部和胸部扫描模式下的剂量较低，在骨盆扫描模式下的剂量与OBI系统相似。在图像引导程序期间，TG111方法在CBCT扫描中心测量的剂量最高；然而，使用现有的CTDI设备，CBDI能很好地近似TG111，并且可能在临床上更适用。
