PMID- 30893477 OWN - NLM STAT- MEDLINE DCOM- 20191122 LR - 20221113 IS - 2473-4209 (Electronic) IS - 0094-2405 (Print) IS - 0094-2405 (Linking) VI - 46 IP - 6 DP - 2019 Jun TI - Estimating fetal dose from tube current-modulated (TCM) and fixed tube current (FTC) abdominal/pelvis CT examinations. PG - 2729-2743 LID - 10.1002/mp.13499 [doi] AB - PURPOSE: The purpose of this work was to estimate scanner-independent CTDI(vol) -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 (D(fetus) ) 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, nD(fetus) , was obtained by dividing D(fetus) from the MC simulations by CTDI(vol) . Patient size was described using water equivalent diameter (D(w) ) measured at the three-dimensional geometric centroid of the fetus. Fetal depth (DE(f) ) was measured from the anterior skin surface to the anterior part of the fetus. nD(fetus) and D(w) 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 nD(fetus) with D(w) and fetal depth (DE(f) ). For one scanner model, nD(fetus) 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. nD(fetus) from FTC simulations was averaged across all scanners for each patient (nDfetus ) . nDfetus was then compared with SSDE f-factors and correlated with D(w) using an exponential model and with D(w) and DE(f) using a bivariate linear model. RESULTS: For TCM, the coefficient of determination (R(2) ) of nD(fetus) and D(w) was observed to be 0.73 using an exponential model. Using the bivariate linear model with D(w) and DE(f) , an R(2) of 0.78 was observed. For the TCM technology modeled, TCM yielded nD(fetus) values that were on average 6% and 17% higher relative to FTC and SSDE f-factors, respectively. For FTC, the R(2) of nDfetus with respect to D(w) was observed to be 0.64 using an exponential model. Using the bivariate linear model, an R(2) of 0.75 was observed for nDfetus with respect to D(w) and DE(f) . A mean difference of 0.4% was observed between nDfetus and SSDE f-factors. CONCLUSION: Good correlations were observed for nD(fetus) from TCM and FTC scans using either an exponential model with D(w) or a bivariate linear model with both D(w) and DE(f) . 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 CTDI(vol) and (b) D(w) as a patient size metric, in addition to (c) DE(f) if available. These results also suggest that SSDE f-factors may provide a reasonable (within +/-25%) estimate of nD(fetus) for TCM and FTC abdomen/pelvis CT exams. CI - (c) 2019 American Association of Physicists in Medicine. FAU - Hardy, Anthony J AU - Hardy AJ AD - Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. AD - Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. FAU - Angel, Erin AU - Angel E AD - Canon Medical Systems USA, Inc., Tustin, CA, 92780, USA. FAU - Bostani, Maryam AU - Bostani M AD - Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. AD - Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. FAU - Cagnon, Chris AU - Cagnon C AD - Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. AD - Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. FAU - McNitt-Gray, Michael AU - McNitt-Gray M AD - Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. AD - Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90024, USA. LA - eng GR - T32 EB002101/EB/NIBIB NIH HHS/United States GR - T32-EB002101/GF/NIH HHS/United States PT - Journal Article DEP - 20190424 PL - United States TA - Med Phys JT - Medical physics JID - 0425746 SB - IM MH - Abdomen/*diagnostic imaging MH - Electric Conductivity MH - Female MH - Fetus/*radiation effects MH - Humans MH - Monte Carlo Method MH - Pelvis/*diagnostic imaging MH - Pregnancy MH - *Radiation Dosage MH - Radiometry MH - Tomography, X-Ray Computed/*adverse effects PMC - PMC6561795 MID - NIHMS1018779 OTO - NOTNLM OT - Monte Carlo simulations OT - computed tomography OT - conceptus dose OT - embryo dose OT - fetal dose OT - radiation dose OT - tube current modulation EDAT- 2019/03/21 06:00 MHDA- 2019/11/23 06:00 PMCR- 2020/06/01 CRDT- 2019/03/21 06:00 PHST- 2018/10/16 00:00 [received] PHST- 2019/03/12 00:00 [revised] PHST- 2019/03/13 00:00 [accepted] PHST- 2019/03/21 06:00 [pubmed] PHST- 2019/11/23 06:00 [medline] PHST- 2019/03/21 06:00 [entrez] PHST- 2020/06/01 00:00 [pmc-release] AID - MP13499 [pii] AID - 10.1002/mp.13499 [doi] PST - ppublish SO - Med Phys. 2019 Jun;46(6):2729-2743. doi: 10.1002/mp.13499. Epub 2019 Apr 24.