PMID- 31081175 OWN - NLM STAT- MEDLINE DCOM- 20191218 LR - 20231012 IS - 1526-9914 (Electronic) IS - 1526-9914 (Linking) VI - 20 IP - 6 DP - 2019 Jun TI - Tolerance levels of mass density for CT number calibration in photon radiation therapy. PG - 45-52 LID - 10.1002/acm2.12601 [doi] AB - Computed tomography (CT) data are required to calculate the dose distribution in a patient's body. Generally, there are two CT number calibration methods for commercial radiotherapy treatment planning system (RTPS), namely CT number-relative electron density calibration (CT-RED calibration) and CT number-mass density calibration (CT-MD calibration). In a previous study, the tolerance levels of CT-RED calibration were established for each tissue type. The tolerance levels were established when the relative dose error to local dose reached 2%. However, the tolerance levels of CT-MD calibration are not established yet. We established the tolerance levels of CT-MD calibration based on the tolerance levels of CT-RED calibration. In order to convert mass density (MD) to relative electron density (RED), the conversion factors were determined with adult reference computational phantom data available in the International Commission on Radiological Protection publication 110 (ICRP-110). In order to validate the practicability of the conversion factor, the relative dose error and the dose linearity were validated with multiple RTPSes and dose calculation algorithms for two groups, namely, CT-RED calibration and CT-MD calibration. The tolerance levels of CT-MD calibration were determined from the tolerance levels of CT-RED calibration with conversion factors. The converted RED from MD was compared with actual RED calculated from ICRP-110. The conversion error was within +/-0.01 for most standard organs. It was assumed that the conversion error was sufficiently small. The relative dose error difference for two groups was less than 0.3% for each tissue type. Therefore, the tolerance levels for CT-MD calibration were determined from the tolerance levels of CT-RED calibration with the conversion factors. The MD tolerance levels for lung, adipose/muscle, and cartilage/spongy-bone corresponded to +/-0.044, +/-0.022, and +/-0.045 g/cm(3) , respectively. The tolerance levels were useful in terms of approving the CT-MD calibration table for clinical use. CI - (c) 2019 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine. FAU - Nakao, Minoru AU - Nakao M AD - Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan. AD - Department of Radiation Oncology, Institute of Biomedical & Health Science, Hiroshima University, Hiroshima, Japan. FAU - Ozawa, Shuichi AU - Ozawa S AD - Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan. AD - Department of Radiation Oncology, Institute of Biomedical & Health Science, Hiroshima University, Hiroshima, Japan. FAU - Yogo, Katsunori AU - Yogo K AD - Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Japan. FAU - Miura, Hideharu AU - Miura H AD - Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan. AD - Department of Radiation Oncology, Institute of Biomedical & Health Science, Hiroshima University, Hiroshima, Japan. FAU - Yamada, Kiyoshi AU - Yamada K AD - Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan. FAU - Hosono, Fumika AU - Hosono F AD - Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan. FAU - Hayata, Masahiro AU - Hayata M AD - Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan. FAU - Miki, Kentaro AU - Miki K AD - Department of Radiation Oncology, Institute of Biomedical & Health Science, Hiroshima University, Hiroshima, Japan. FAU - Nakashima, Takeo AU - Nakashima T AD - Radiation Therapy Section, Department of Clinical Support, Hiroshima University Hospital, Hiroshima, Japan. FAU - Ochi, Yusuke AU - Ochi Y AD - Radiation Therapy Section, Department of Clinical Support, Hiroshima University Hospital, Hiroshima, Japan. FAU - Kawahara, Daisuke AU - Kawahara D AD - Radiation Therapy Section, Department of Clinical Support, Hiroshima University Hospital, Hiroshima, Japan. FAU - Morimoto, Yoshiharu AU - Morimoto Y AD - Department of Radiology, Hiroshima Prefectural Hospital, Hiroshima, Japan. FAU - Yoshizaki, Toru AU - Yoshizaki T AD - Radiation Therapy Department, Hiroshima City Hiroshima Citizens Hospital, Hiroshima, Japan. FAU - Nozaki, Hiroshige AU - Nozaki H AD - Division of Radiology, Hiroshima Red Cross Hospital & Atomic-bomb Survivors Hospital, Hiroshima, Japan. FAU - Habara, Kosaku AU - Habara K AD - Division of Radiology, Hiroshima Red Cross Hospital & Atomic-bomb Survivors Hospital, Hiroshima, Japan. FAU - Nagata, Yasushi AU - Nagata Y AD - Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan. AD - Department of Radiation Oncology, Institute of Biomedical & Health Science, Hiroshima University, Hiroshima, Japan. LA - eng PT - Journal Article DEP - 20190513 PL - United States TA - J Appl Clin Med Phys JT - Journal of applied clinical medical physics JID - 101089176 SB - IM MH - *Algorithms MH - Calibration MH - Humans MH - Image Processing, Computer-Assisted/methods MH - Organs at Risk/radiation effects MH - *Phantoms, Imaging MH - Photons/*therapeutic use MH - *Radiation Protection MH - Radiotherapy Dosage MH - Radiotherapy Planning, Computer-Assisted/*methods MH - Tomography, X-Ray Computed/*methods PMC - PMC6560312 OTO - NOTNLM OT - CT number calibration OT - mass density OT - photon radiation therapy OT - radiation treatment planning OT - tolerance level COIS- The authors declare no conflict of interest. EDAT- 2019/05/14 06:00 MHDA- 2019/12/19 06:00 PMCR- 2019/05/13 CRDT- 2019/05/14 06:00 PHST- 2018/10/21 00:00 [received] PHST- 2019/03/22 00:00 [revised] PHST- 2019/04/10 00:00 [accepted] PHST- 2019/05/14 06:00 [pubmed] PHST- 2019/12/19 06:00 [medline] PHST- 2019/05/14 06:00 [entrez] PHST- 2019/05/13 00:00 [pmc-release] AID - ACM212601 [pii] AID - 10.1002/acm2.12601 [doi] PST - ppublish SO - J Appl Clin Med Phys. 2019 Jun;20(6):45-52. doi: 10.1002/acm2.12601. Epub 2019 May 13.