Cynthia McCollough, Donovan M Bakalyar, Maryam Bostani, Samuel Brady, Kristen Boedeker, John M Boone, H Heather Chen-Mayer, Olav I Christianson, Shuai Leng, Baojun Li, Michael F McNitt-Gray, Roy A Nilsen, Mark P Supanich, Jia Wang
{"title":"Use of Water Equivalent Diameter for Calculating Patient Size and Size-Specific Dose Estimates (SSDE) in CT: The Report of AAPM Task Group 220.","authors":"Cynthia McCollough, Donovan M Bakalyar, Maryam Bostani, Samuel Brady, Kristen Boedeker, John M Boone, H Heather Chen-Mayer, Olav I Christianson, Shuai Leng, Baojun Li, Michael F McNitt-Gray, Roy A Nilsen, Mark P Supanich, Jia Wang","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":91432,"journal":{"name":"AAPM report","volume":"2014 ","pages":"6-23"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4991550/pdf/nihms-766038.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34325627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. McCollough, D. Bakalyar, M. Bostani, S. Brady, Kristen L Boedeker, J. Boone, H. Chen-Mayer, O. Christianson, S. Leng, Baojun Li, M. McNitt-Gray, R. Nilsen, M. Supanich, Jia Wang
Volume computed tomography dose index (CTDIvol) and dose length product (DLP) values are frequently used to represent radiation doses from a CT scan. The limitation of CTDIvol and DLP is that they are surrogates for patient dose, providing information about the scanner output for only a very specific standardized condition [1]. The dose received by a patient depends on both patient size and scanner output. Turner et al. showed that using CTDIvol as a normalization factor, organ dose estimates can be obtained for a specific patient size [2], and that the relationship to patient size was consistent across scanner models [3]. Their results showed a promising approach to estimating size-dependent, scanner-specific, and exam-specific organ doses based on patient size and the CTDIvol reported by the scanner. Hence, obtaining accurate information about patient size is crucial to estimating patient dose in CT. Report 204 from the American Association of Physicists in Medicine (AAPM) described the use of a size metric that involved the physical dimensions of the patient (anteroposterior [AP], lateral, AP+lateral, or effective diameter), in combination with scanner output (CTDIvol), to determine size-specific dose estimates (SSDE) from CT scanning [4]. Patient dimension can be determined using physical or electronic tools. Physical devices, such as the calipers that were frequently used in radiography before the routine use of phototiming, may be used to measure patient thickness in the AP or lateral directions. Alternatively, electronic measurement tools can be used to measure physical dimensions from either the CT localizer radiograph or an axial CT image. The conversion factors used to calculate SSDE from CTDIvol reported in AAPM Report 204 were derived from experimental and Monte Carlo data and normalized to patient size in terms of water- or tissue-equivalent materials. For the task of calculating SSDE, geometric size was used as a surrogate for a patient's x-ray attenuation. However, x-ray attenuation is the fundamental physical parameter affecting the absorption of x-rays and is thus more relevant than geometric patient size in determining the radiation dose absorbed by the patient. For example, regions of the thorax and abdomen could have the same external physical dimensions. However, because the lungs are less dense and of different composition than abdominal tissue, the thorax would attenuate fewer x-ray photons than would the abdomen. For the same scanner output (CTDIvol), the thorax region would experience a higher radiation fluence and, hence, have a higher absorbed dose than an abdominal region having the same geometric dimensions. While CT operators can measure a patient's AP or lateral width, they currently have no practical way to measure attenuation. Both a CT localizer radiograph and CT projection data are measurements of the integrated x-ray attenuation along a ray path, and a CT image is a cross-sectional map of the linear atten
{"title":"Use of Water Equivalent Diameter for Calculating Patient Size and Size-Specific Dose Estimates (SSDE) in CT: The Report of AAPM Task Group 220.","authors":"C. McCollough, D. Bakalyar, M. Bostani, S. Brady, Kristen L Boedeker, J. Boone, H. Chen-Mayer, O. Christianson, S. Leng, Baojun Li, M. McNitt-Gray, R. Nilsen, M. Supanich, Jia Wang","doi":"10.37206/146","DOIUrl":"https://doi.org/10.37206/146","url":null,"abstract":"Volume computed tomography dose index (CTDIvol) and dose length product (DLP) values are frequently used to represent radiation doses from a CT scan. The limitation of CTDIvol and DLP is that they are surrogates for patient dose, providing information about the scanner output for only a very specific standardized condition [1]. The dose received by a patient depends on both patient size and scanner output. Turner et al. showed that using CTDIvol as a normalization factor, organ dose estimates can be obtained for a specific patient size [2], and that the relationship to patient size was consistent across scanner models [3]. Their results showed a promising approach to estimating size-dependent, scanner-specific, and exam-specific organ doses based on patient size and the CTDIvol reported by the scanner. Hence, obtaining accurate information about patient size is crucial to estimating patient dose in CT. \u0000 \u0000Report 204 from the American Association of Physicists in Medicine (AAPM) described the use of a size metric that involved the physical dimensions of the patient (anteroposterior [AP], lateral, AP+lateral, or effective diameter), in combination with scanner output (CTDIvol), to determine size-specific dose estimates (SSDE) from CT scanning [4]. Patient dimension can be determined using physical or electronic tools. Physical devices, such as the calipers that were frequently used in radiography before the routine use of phototiming, may be used to measure patient thickness in the AP or lateral directions. Alternatively, electronic measurement tools can be used to measure physical dimensions from either the CT localizer radiograph or an axial CT image. The conversion factors used to calculate SSDE from CTDIvol reported in AAPM Report 204 were derived from experimental and Monte Carlo data and normalized to patient size in terms of water- or tissue-equivalent materials. \u0000 \u0000For the task of calculating SSDE, geometric size was used as a surrogate for a patient's x-ray attenuation. However, x-ray attenuation is the fundamental physical parameter affecting the absorption of x-rays and is thus more relevant than geometric patient size in determining the radiation dose absorbed by the patient. For example, regions of the thorax and abdomen could have the same external physical dimensions. However, because the lungs are less dense and of different composition than abdominal tissue, the thorax would attenuate fewer x-ray photons than would the abdomen. For the same scanner output (CTDIvol), the thorax region would experience a higher radiation fluence and, hence, have a higher absorbed dose than an abdominal region having the same geometric dimensions. While CT operators can measure a patient's AP or lateral width, they currently have no practical way to measure attenuation. Both a CT localizer radiograph and CT projection data are measurements of the integrated x-ray attenuation along a ray path, and a CT image is a cross-sectional map of the linear atten","PeriodicalId":91432,"journal":{"name":"AAPM report","volume":"2014 1","pages":"6-23"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70024550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：