Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Dec;45(4):1183-1191.
doi: 10.1007/s13246-022-01186-4. Epub 2022 Oct 31.

SIZE-specific dose estimate for lower-limb CT

Masanao Kobayashi  1 , Yusei Nishihara  2 , Tomonobu Haba  3 , Yuta Matsunaga  4 , Yasuki Asada  3 , Shigeki Kobayashi  3
Affiliations

SIZE-specific dose estimate for lower-limb CT

Masanao Kobayashi et al. Phys Eng Sci Med. 2022 Dec.

Abstract

The Computed Tomography Dose Index (CTDI) is an indicator for dose management in computed tomography (CT), but has limited use for patient dosimetry. To evaluate the patient dose, the size-specific dose estimate (SSDE), reported by the American Association of Physics in Medicine task groups 204, 220, and 293, must be calculated by the CTDIvol(z) displayed on the CT console, and the conversion factor f(D(z)) from the effective diameter (DEff) or water equivalent diameter (Dw). However, no reports have verified the appropriateness of using the 320-mm diameter phantom for dose assessment in CT examinations involving the lower limbs. Therefore, we validated a new method for evaluating the SSDE(z) of the lower limbs, using two 160-mm diameter phantoms instead of the 320-mm diameter phantom. The CTDIvol(z) obtained from Monte Carlo (MC) simulation study was reliable because they were almost the same as obtained in a dosimetry study. The conversion factor f (D (zl.l.)) for the lower limbs was evaluated based on the CTDIvol(z) obtained by MC simulation performed using two polymethyl methacrylate cylinder phantoms of 160-mm diameter. The MC simulation was performed by the International Commission on Radiological Protection publication 135 reference adult phantom and was used to evaluate the absorbed dose of the pelvis, thighs, knees, and ankles. The dose showing the greatest difference was the thighs, which was 8.3 mGy (16%) lower than the absorbed dose. Thus, the SSDE (zl.l.) could be estimated from the [Formula: see text] displayed on the CT scanner console.

Keywords: CT; Monte Carlo simulation; Patient dose; Size-specific dose estimate.

PubMed Disclaimer

References

    1. Food and Drug Administration. Diagnostic x-ray systems and their major components. 1984; United States FDA Code of Federal Regulations, 21 CFR 1020.33, US Nuclear Regulatory Commission, US Govt. (Washington DC: FDA).
    1. International Electrotechnical Commission. International Standard. Medical Electrical Equipment–Part 2–44: Particular Requirements for the Safety of X-ray Equipment for Computed Tomography. 2009; IEC 60601–2–44 Ed3 Amendment 1. (Geneva, Switzerland: IEC).
    1. International Commission on Radiological Protection. The 2007 Recommendations of the International Commission on Radiological Protection. Ann ICRP. 37 (2–4) 2007; ICRP Publication no. 103.
    1. McCollough CH, Leng S, Yu L, Cody DD, Boone JM, McNitt-Gray MF (2011) CT dose index and patient dose: they are not the same thing. Radiology 259:311–316. https://doi.org/10.1148/radiol.11101800 - DOI
    1. American Association of Physicists in Medicine. Size-Specific Dose Estimates (SSDE) in Pediatric and Adult Body CT Examinations. AAPM Task Group 204 2011; AAPM Report no. 204.