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Estimating fetal dose from tube current-modulated (TCM) and fixed tube current (FTC) abdominal/pelvis CT examinations.
Med Phys. 2019 Jun; 46(6):2729-2743.MP

Abstract

PURPOSE

The purpose of this work was to estimate scanner-independent CTDIvol -to-fetal-dose coefficients for tube current-modulated (TCM) and fixed tube current (FTC) computed tomography (CT) examinations of pregnant patients of various gestational ages undergoing abdominal/pelvic CT examinations.

METHODS

For 24 pregnant patients of gestational age from <5 to 36 weeks who underwent clinically indicated CT examinations, voxelized models of maternal and fetal (or embryo) anatomy were created from abdominal/pelvic image data. Absolute fetal dose (Dfetus) was estimated using Monte Carlo (MC) simulations of helical scans covering the abdomen and pelvis for TCM and FTC scans. Estimated TCM schemes were generated for each patient model using a validated method that accounts for patient attenuation and scanner output limits for one scanner model and were incorporated into MC simulations. FTC scans were also simulated for each patient model with multidetector row CT scanners from four manufacturers. Normalized fetal dose estimates, nDfetus , was obtained by dividing Dfetus from the MC simulations by CTDIvol . Patient size was described using water equivalent diameter (Dw) measured at the three-dimensional geometric centroid of the fetus. Fetal depth (DEf) was measured from the anterior skin surface to the anterior part of the fetus. nDfetus and Dw were correlated using an exponential model to develop equations for fetal dose conversion coefficients for TCM and FTC abdominal/pelvic CT examinations. Additionally, bivariate linear regression was performed to analyze the correlation of nDfetus with Dw and fetal depth (DEf). For one scanner model, nDfetus from TCM was compared to FTC and the size-specific dose estimate (SSDE) conversion coefficients (f-factors) from American Association of Physicists in Medicine (AAPM) Report 204. nDfetus from FTC simulations was averaged across all scanners for each patient (n D fetus ¯) . n D fetus ¯ was then compared with SSDE f-factors and correlated with Dw using an exponential model and with Dw and DEf using a bivariate linear model.

RESULTS

For TCM, the coefficient of determination (R2) of nDfetus and Dw was observed to be 0.73 using an exponential model. Using the bivariate linear model with Dw and DEf , an R2 of 0.78 was observed. For the TCM technology modeled, TCM yielded nDfetus values that were on average 6% and 17% higher relative to FTC and SSDE f-factors, respectively. For FTC, the R2 of n D fetus ¯ with respect to Dw was observed to be 0.64 using an exponential model. Using the bivariate linear model, an R2 of 0.75 was observed for n D fetus ¯ with respect to Dw and DEf . A mean difference of 0.4% was observed between n D fetus ¯ and SSDE f-factors.

CONCLUSION

Good correlations were observed for nDfetus from TCM and FTC scans using either an exponential model with Dw or a bivariate linear model with both Dw and DEf . These results indicate that fetal dose from abdomen/pelvis CT examinations of pregnant patients of various gestational ages may be reasonably estimated with models that include (a) scanner-reported CTDIvol and (b) Dw as a patient size metric, in addition to (c) DEf if available. These results also suggest that SSDE f-factors may provide a reasonable (within ±25%) estimate of nDfetus for TCM and FTC abdomen/pelvis CT exams.

Authors+Show Affiliations

Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.Canon Medical Systems USA, Inc., Tustin, CA, 92780, USA.Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

30893477

Citation

Hardy, Anthony J., et al. "Estimating Fetal Dose From Tube Current-modulated (TCM) and Fixed Tube Current (FTC) Abdominal/pelvis CT Examinations." Medical Physics, vol. 46, no. 6, 2019, pp. 2729-2743.
Hardy AJ, Angel E, Bostani M, et al. Estimating fetal dose from tube current-modulated (TCM) and fixed tube current (FTC) abdominal/pelvis CT examinations. Med Phys. 2019;46(6):2729-2743.
Hardy, A. J., Angel, E., Bostani, M., Cagnon, C., & McNitt-Gray, M. (2019). Estimating fetal dose from tube current-modulated (TCM) and fixed tube current (FTC) abdominal/pelvis CT examinations. Medical Physics, 46(6), 2729-2743. https://doi.org/10.1002/mp.13499
Hardy AJ, et al. Estimating Fetal Dose From Tube Current-modulated (TCM) and Fixed Tube Current (FTC) Abdominal/pelvis CT Examinations. Med Phys. 2019;46(6):2729-2743. PubMed PMID: 30893477.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Estimating fetal dose from tube current-modulated (TCM) and fixed tube current (FTC) abdominal/pelvis CT examinations. AU - Hardy,Anthony J, AU - Angel,Erin, AU - Bostani,Maryam, AU - Cagnon,Chris, AU - McNitt-Gray,Michael, Y1 - 2019/04/24/ PY - 2018/10/16/received PY - 2019/03/12/revised PY - 2019/03/13/accepted PY - 2020/06/01/pmc-release PY - 2019/3/21/pubmed PY - 2019/11/23/medline PY - 2019/3/21/entrez KW - Monte Carlo simulations KW - computed tomography KW - conceptus dose KW - embryo dose KW - fetal dose KW - radiation dose KW - tube current modulation SP - 2729 EP - 2743 JF - Medical physics JO - Med Phys VL - 46 IS - 6 N2 - PURPOSE: The purpose of this work was to estimate scanner-independent CTDIvol -to-fetal-dose coefficients for tube current-modulated (TCM) and fixed tube current (FTC) computed tomography (CT) examinations of pregnant patients of various gestational ages undergoing abdominal/pelvic CT examinations. METHODS: For 24 pregnant patients of gestational age from <5 to 36 weeks who underwent clinically indicated CT examinations, voxelized models of maternal and fetal (or embryo) anatomy were created from abdominal/pelvic image data. Absolute fetal dose (Dfetus) was estimated using Monte Carlo (MC) simulations of helical scans covering the abdomen and pelvis for TCM and FTC scans. Estimated TCM schemes were generated for each patient model using a validated method that accounts for patient attenuation and scanner output limits for one scanner model and were incorporated into MC simulations. FTC scans were also simulated for each patient model with multidetector row CT scanners from four manufacturers. Normalized fetal dose estimates, nDfetus , was obtained by dividing Dfetus from the MC simulations by CTDIvol . Patient size was described using water equivalent diameter (Dw) measured at the three-dimensional geometric centroid of the fetus. Fetal depth (DEf) was measured from the anterior skin surface to the anterior part of the fetus. nDfetus and Dw were correlated using an exponential model to develop equations for fetal dose conversion coefficients for TCM and FTC abdominal/pelvic CT examinations. Additionally, bivariate linear regression was performed to analyze the correlation of nDfetus with Dw and fetal depth (DEf). For one scanner model, nDfetus from TCM was compared to FTC and the size-specific dose estimate (SSDE) conversion coefficients (f-factors) from American Association of Physicists in Medicine (AAPM) Report 204. nDfetus from FTC simulations was averaged across all scanners for each patient (n D fetus ¯) . n D fetus ¯ was then compared with SSDE f-factors and correlated with Dw using an exponential model and with Dw and DEf using a bivariate linear model. RESULTS: For TCM, the coefficient of determination (R2) of nDfetus and Dw was observed to be 0.73 using an exponential model. Using the bivariate linear model with Dw and DEf , an R2 of 0.78 was observed. For the TCM technology modeled, TCM yielded nDfetus values that were on average 6% and 17% higher relative to FTC and SSDE f-factors, respectively. For FTC, the R2 of n D fetus ¯ with respect to Dw was observed to be 0.64 using an exponential model. Using the bivariate linear model, an R2 of 0.75 was observed for n D fetus ¯ with respect to Dw and DEf . A mean difference of 0.4% was observed between n D fetus ¯ and SSDE f-factors. CONCLUSION: Good correlations were observed for nDfetus from TCM and FTC scans using either an exponential model with Dw or a bivariate linear model with both Dw and DEf . These results indicate that fetal dose from abdomen/pelvis CT examinations of pregnant patients of various gestational ages may be reasonably estimated with models that include (a) scanner-reported CTDIvol and (b) Dw as a patient size metric, in addition to (c) DEf if available. These results also suggest that SSDE f-factors may provide a reasonable (within ±25%) estimate of nDfetus for TCM and FTC abdomen/pelvis CT exams. SN - 2473-4209 UR - https://www.unboundmedicine.com/medline/citation/30893477/Estimating_fetal_dose_from_tube_current_modulated__TCM__and_fixed_tube_current__FTC__abdominal/pelvis_CT_examinations_ L2 - https://doi.org/10.1002/mp.13499 DB - PRIME DP - Unbound Medicine ER -