Size-specific dose estimates for chest, abdominal, and pelvic CT: Effect of intrapatient variability in water-equivalent diameter

Shuai Leng, Maria Shiung, Xinhui Duan, Lifeng Yu, Yi Zhang, Cynthia H McCollough

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Purpose: To develop software to automatically calculate size-specific dose estimates (SSDEs) and to assess the effect of variations in water-equivalent diameter (D<inf>w</inf>) along the z-axis on SSDE for computed tomographic (CT) examinations of the torso. Materials and Methods: In this institutional review board-approved, HIPAA-compliant, retrospective study, a software program was used to calculate D<inf>w</inf> at each image position in 102 consecutive CT examinations of the combined chest, abdomen, and pelvis. SSDE was calculated by multiplying the size-dependent conversion factor and volume CT dose index (CTDI<inf>vol</inf>) at each image position. The variations in D<inf>w</inf> along the z-axis were determined for six hypothetical scanning ranges: chest alone; abdomen alone; pelvis alone; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis. Mean SSDE was calculated in two ways: (a) from the SSDE at each position and (b) from the mean CTDI<inf>vol</inf> over each scan range and the conversion factor corresponding to D<inf>w</inf> at the middle of the scan range. Linear regression analysis was performed to determine the correlation between SSDE values calculated in these two ways. Results: Across patients, for scan ranges 1-6, the mean of the difference between maximal and minimal D<inf>w</inf> within a given patient was 5.2, 4.9, 2.5, 6.0, 5.6, and 6.5 cm, respectively. The mean SSDE values calculated by using the two methods were in close agreement, with root mean square differences of 0.9, 0.5, 0.5, 1.4, 1.0, and 1.1 mGy or 6%, 3%, 2%, 9%, 4%, and 6%, for the scan ranges of chest; abdomen; pelvis; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis, respectively. Conclusion: Using the mean CTDI<inf>vol</inf> from the whole scan range and D<inf>w</inf> from the image at the center of the scan range provided an easily obtained estimate of SSDE for the whole scan range that agreed well with values from an image-by-image approach, with a root mean square difference less than 1.4 mGy (9%).

Original languageEnglish (US)
Pages (from-to)184-190
Number of pages7
JournalRadiology
Volume276
Issue number1
DOIs
StatePublished - Jul 1 2015

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Abdomen
Thorax
Pelvis
Water
Software
Health Insurance Portability and Accountability Act
Torso
Research Ethics Committees
Linear Models
Retrospective Studies
Regression Analysis

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

Cite this

Size-specific dose estimates for chest, abdominal, and pelvic CT : Effect of intrapatient variability in water-equivalent diameter. / Leng, Shuai; Shiung, Maria; Duan, Xinhui; Yu, Lifeng; Zhang, Yi; McCollough, Cynthia H.

In: Radiology, Vol. 276, No. 1, 01.07.2015, p. 184-190.

Research output: Contribution to journalArticle

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title = "Size-specific dose estimates for chest, abdominal, and pelvic CT: Effect of intrapatient variability in water-equivalent diameter",
abstract = "Purpose: To develop software to automatically calculate size-specific dose estimates (SSDEs) and to assess the effect of variations in water-equivalent diameter (Dw) along the z-axis on SSDE for computed tomographic (CT) examinations of the torso. Materials and Methods: In this institutional review board-approved, HIPAA-compliant, retrospective study, a software program was used to calculate Dw at each image position in 102 consecutive CT examinations of the combined chest, abdomen, and pelvis. SSDE was calculated by multiplying the size-dependent conversion factor and volume CT dose index (CTDIvol) at each image position. The variations in Dw along the z-axis were determined for six hypothetical scanning ranges: chest alone; abdomen alone; pelvis alone; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis. Mean SSDE was calculated in two ways: (a) from the SSDE at each position and (b) from the mean CTDIvol over each scan range and the conversion factor corresponding to Dw at the middle of the scan range. Linear regression analysis was performed to determine the correlation between SSDE values calculated in these two ways. Results: Across patients, for scan ranges 1-6, the mean of the difference between maximal and minimal Dw within a given patient was 5.2, 4.9, 2.5, 6.0, 5.6, and 6.5 cm, respectively. The mean SSDE values calculated by using the two methods were in close agreement, with root mean square differences of 0.9, 0.5, 0.5, 1.4, 1.0, and 1.1 mGy or 6{\%}, 3{\%}, 2{\%}, 9{\%}, 4{\%}, and 6{\%}, for the scan ranges of chest; abdomen; pelvis; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis, respectively. Conclusion: Using the mean CTDIvol from the whole scan range and Dw from the image at the center of the scan range provided an easily obtained estimate of SSDE for the whole scan range that agreed well with values from an image-by-image approach, with a root mean square difference less than 1.4 mGy (9{\%}).",
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T1 - Size-specific dose estimates for chest, abdominal, and pelvic CT

T2 - Effect of intrapatient variability in water-equivalent diameter

AU - Leng, Shuai

AU - Shiung, Maria

AU - Duan, Xinhui

AU - Yu, Lifeng

AU - Zhang, Yi

AU - McCollough, Cynthia H

PY - 2015/7/1

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N2 - Purpose: To develop software to automatically calculate size-specific dose estimates (SSDEs) and to assess the effect of variations in water-equivalent diameter (Dw) along the z-axis on SSDE for computed tomographic (CT) examinations of the torso. Materials and Methods: In this institutional review board-approved, HIPAA-compliant, retrospective study, a software program was used to calculate Dw at each image position in 102 consecutive CT examinations of the combined chest, abdomen, and pelvis. SSDE was calculated by multiplying the size-dependent conversion factor and volume CT dose index (CTDIvol) at each image position. The variations in Dw along the z-axis were determined for six hypothetical scanning ranges: chest alone; abdomen alone; pelvis alone; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis. Mean SSDE was calculated in two ways: (a) from the SSDE at each position and (b) from the mean CTDIvol over each scan range and the conversion factor corresponding to Dw at the middle of the scan range. Linear regression analysis was performed to determine the correlation between SSDE values calculated in these two ways. Results: Across patients, for scan ranges 1-6, the mean of the difference between maximal and minimal Dw within a given patient was 5.2, 4.9, 2.5, 6.0, 5.6, and 6.5 cm, respectively. The mean SSDE values calculated by using the two methods were in close agreement, with root mean square differences of 0.9, 0.5, 0.5, 1.4, 1.0, and 1.1 mGy or 6%, 3%, 2%, 9%, 4%, and 6%, for the scan ranges of chest; abdomen; pelvis; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis, respectively. Conclusion: Using the mean CTDIvol from the whole scan range and Dw from the image at the center of the scan range provided an easily obtained estimate of SSDE for the whole scan range that agreed well with values from an image-by-image approach, with a root mean square difference less than 1.4 mGy (9%).

AB - Purpose: To develop software to automatically calculate size-specific dose estimates (SSDEs) and to assess the effect of variations in water-equivalent diameter (Dw) along the z-axis on SSDE for computed tomographic (CT) examinations of the torso. Materials and Methods: In this institutional review board-approved, HIPAA-compliant, retrospective study, a software program was used to calculate Dw at each image position in 102 consecutive CT examinations of the combined chest, abdomen, and pelvis. SSDE was calculated by multiplying the size-dependent conversion factor and volume CT dose index (CTDIvol) at each image position. The variations in Dw along the z-axis were determined for six hypothetical scanning ranges: chest alone; abdomen alone; pelvis alone; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis. Mean SSDE was calculated in two ways: (a) from the SSDE at each position and (b) from the mean CTDIvol over each scan range and the conversion factor corresponding to Dw at the middle of the scan range. Linear regression analysis was performed to determine the correlation between SSDE values calculated in these two ways. Results: Across patients, for scan ranges 1-6, the mean of the difference between maximal and minimal Dw within a given patient was 5.2, 4.9, 2.5, 6.0, 5.6, and 6.5 cm, respectively. The mean SSDE values calculated by using the two methods were in close agreement, with root mean square differences of 0.9, 0.5, 0.5, 1.4, 1.0, and 1.1 mGy or 6%, 3%, 2%, 9%, 4%, and 6%, for the scan ranges of chest; abdomen; pelvis; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis, respectively. Conclusion: Using the mean CTDIvol from the whole scan range and Dw from the image at the center of the scan range provided an easily obtained estimate of SSDE for the whole scan range that agreed well with values from an image-by-image approach, with a root mean square difference less than 1.4 mGy (9%).

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