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使用瓦里安 OBI 1.3 和 1.4 CBCT 系统的吸收剂量和剂量率。

Absorbed dose and dose rate using the Varian OBI 1.3 and 1.4 CBCT system.

机构信息

Sahlgrenska University Hospital, Deptartment of Medical Physics and Biomedical Engineering, Göteborg, Sweden.

出版信息

J Appl Clin Med Phys. 2010 Jan 28;11(1):3085. doi: 10.1120/jacmp.v11i1.3085.

Abstract

According to published data, the absorbed dose used for a CBCT image acquisition with Varian OBI v1.3 can be as high as 100 mGy. In 2008 Varian released a new OBI version (v1.4), which promised to reduce the imaging dose. In this study, absorbed doses used for CBCT image acquisitions with the default irradiation techniques of Varian OBI v1.3 and v1.4 are measured. TLDs are used to derive dose distributions at three planes inside an anthropomorphic phantom. In addition, point doses and dose profiles inside a 'stack' of three CTDI body phantoms are measured using a new solid state detector, the CT Dose Profiler. With the CT Dose Profiler, the individual pulses from the X-ray tube are also studied. To verify the absorbed dose measured with the CT Dose Profiler, it is compared to TLD. The image quality is evaluated using a Catphan phantom. For OBI v1.3, doses measured in transverse planes of the Alderson phantom range between 64 mGy and 144 mGy. The average dose is around 100 mGy. For OBI v1.4, doses measured in transverse planes of the Alderson phantom range between 1 mGy and 51 mGy. Mean doses range between 3-35 mGy depending on CBCT mode. CT Dose Profiler data agree with TLD measurements in a CTDI phantom within the uncertainty of the TLD measurements (estimated SD +/- 10%). Instantaneous dose rate at the periphery of the phantom can be higher than 20 mGy/s, which is 10 times the dose rate at the center. The spatial resolution in v1.4 is not as high as in v1.3. In conclusion, measurements show that the imaging doses for default modes in Varian OBI v1.4 CBCT system are significantly lower than in v1.3. The CT Dose Profiler is proven fast and accurate for CBCT applications.

摘要

根据已发表的数据,瓦里安 OBI v1.3 进行锥形束 CT 图像采集时的吸收剂量高达 100 mGy。2008 年,瓦里安发布了新的 OBI 版本(v1.4),承诺降低成像剂量。在这项研究中,测量了瓦里安 OBI v1.3 和 v1.4 中默认照射技术进行 CBCT 图像采集时的吸收剂量。使用 TLD 测量体模内三个平面的剂量分布。此外,使用新的固态探测器 CT 剂量分布仪测量三个 CTDI 体模“堆叠”内的点剂量和剂量分布。使用 CT 剂量分布仪还研究了 X 射线管的单个脉冲。为了验证 CT 剂量分布仪测量的吸收剂量,将其与 TLD 进行了比较。使用 Catphan 体模评估图像质量。对于 OBI v1.3,在 Alderson 体模的横断面上测量的剂量在 64 mGy 到 144 mGy 之间。平均剂量约为 100 mGy。对于 OBI v1.4,在 Alderson 体模的横断面上测量的剂量在 1 mGy 到 51 mGy 之间。取决于 CBCT 模式,平均剂量在 3 到 35 mGy 之间。在 CTDI 体模中,CT 剂量分布仪数据与 TLD 测量值在 TLD 测量值的不确定度范围内一致(估计标准偏差 +/- 10%)。体模边缘的瞬时剂量率可能高于 20 mGy/s,是中心剂量率的 10 倍。v1.4 的空间分辨率不如 v1.3 高。总之,测量结果表明,瓦里安 OBI v1.4 CBCT 系统中默认模式的成像剂量明显低于 v1.3。CT 剂量分布仪已被证明在 CBCT 应用中快速且准确。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/3539/5719770/e68a63691ce9/ACM2-11-229-g001.jpg

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