From the Departments of Radiology.
Orthopedics, Boston Children's Hospital, Harvard Medical School, Boston, MA.
Invest Radiol. 2023 Mar 1;58(3):190-198. doi: 10.1097/RLI.0000000000000920. Epub 2022 Aug 28.
Hip displacement is the second most common orthopedic problem affecting children with cerebral palsy (CP). Routine radiographic hip surveillance typically involves an anteroposterior (AP) pelvis radiograph. Unfortunately, this imaging protocol is limited by its projectional technique and the positioning challenges in children with CP. Alternatively, hip low-dose computed tomography (LDCT) has been advocated as a more accurate strategy for imaging surveillance as it provides biofidelic details of the hip that is independent of patient positioning. However, the tradeoff is the (presumed) higher radiation dose to the patient. The goal of this study is to estimate patient-specific radiation doses of hip LDCTs and AP pelvis radiographs in CP patients, and perform an intrapatient dose comparison.
A search of our imaging database was performed to identify children with CP who underwent hip LDCT and AP pelvis radiograph within 6 months of each other. The LDCTs were performed using weight-adjusted kVp and tube current modulation, whereas the radiographs were obtained with age-/size-adjusted kVp/mAs. The patient-specific organ and effective doses for LDCT were estimated by matching the patients to a nonreference pediatric phantom library from the National Cancer Institute Dosimetry System for Computed Tomography database with Monte Carlo-based dosimetry. The patient-specific organ and effective doses for radiograph were estimated using the National Cancer Institute Dosimetry System for Radiography and Fluoroscopy with Monte Carlo-based dose calculation. Dose conversion k-factors of dose area product for radiography and dose length product for LDCT were adapted, and the estimation results were compared with patient-specific dosimetry.
Our study cohort consisted of 70 paired imaging studies from 67 children (age, 9.1 ± 3.3 years). The patient-specific and dose length product-based effective doses for LDCT were 0.42 ± 0.21 mSv and 0.59 ± 0.28 mSv, respectively. The patient-specific and dose area product-based effective doses for radiography were 0.14 ± 0.09 mSv and 0.08 ± 0.06 mSv, respectively.
The radiation dose for a hip LDCT is ~4 times higher than pelvis radiograph, but it is still very low and poses minimal risk to the patient.
髋关节位移是影响脑瘫（CP）儿童的第二大常见骨科问题。常规放射性髋关节监测通常包括前后位（AP）骨盆 X 光片。不幸的是，这种成像方案受到其投影技术和 CP 儿童定位挑战的限制。相反，髋关节低剂量计算机断层扫描（LDCT）已被提倡作为一种更准确的成像监测策略，因为它提供了与患者定位无关的髋关节逼真细节。然而，权衡是对患者的（假定）更高的辐射剂量。本研究的目的是估计 CP 患者髋关节 LDCT 和 AP 骨盆 X 光片的患者特异性辐射剂量，并进行患者内剂量比较。
对我们的成像数据库进行了搜索，以确定在彼此 6 个月内接受髋关节 LDCT 和 AP 骨盆 X 光片的 CP 患儿。LDCT 采用体重调整的 kVp 和管电流调制，而 X 光片则采用年龄/大小调整的 kVp/mAs 获得。通过将患者与国家癌症研究所计算机断层摄影剂量系统中的非参考儿科体模库进行匹配，使用基于蒙特卡罗的剂量测量来估计 LDCT 的患者特异性器官和有效剂量。通过使用基于蒙特卡罗的剂量计算的国家癌症研究所放射摄影和透视剂量系统来估计 X 光片的患者特异性器官和有效剂量。对放射摄影的剂量面积乘积和 LDCT 的剂量长度乘积的转换 k 因子进行了改编，并将估算结果与患者特异性剂量进行了比较。
我们的研究队列由 67 名儿童的 70 对成像研究组成（年龄，9.1 ± 3.3 岁）。LDCT 的患者特异性和剂量长度乘积的有效剂量分别为 0.42 ± 0.21 mSv 和 0.59 ± 0.28 mSv。放射摄影的患者特异性和剂量面积乘积的有效剂量分别为 0.14 ± 0.09 mSv 和 0.08 ± 0.06 mSv。
髋关节 LDCT 的辐射剂量是骨盆 X 光片的 4 倍左右，但仍然非常低，对患者的风险很小。
