Radiation Dose to the Fetus from Body MDCT During Early Gestation

Hurwitz, Lynne M.; Yoshizumi, Terry T.; Reiman, Robert E.; Goodman, Philip C.; Paulson, Erik K.; Frush, Donald P.; Toncheva, Greta; Nguyen, Giao; Barnes, Lottie

doi:10.2214/ajr.04.1915

Cited by 223 publications

(148 citation statements)

References 23 publications

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“…Besides, the embryo/fetal dose from CTPA studies has been reported to be 0.06-0.23 mGy during the third trimester of pregnancy (26), which agrees with our findings of 0.05-0.28 mGy. Discordantly, Hurwittz et al (27) reported an embryo/fetal dose of 0.24-0.66 mGy from CTPA studies performed on pregnant patients with suspected PE during the first trimester. The considerable difference between these results and our data for the first trimester, that is, 0.05-0.16 mGy, may be attributed to the considerably higher exposure settings used in the study by Hurwitz et al, that is, 140 kV-300 mAs.…”

Section: Discussionmentioning

confidence: 87%

Perfusion Scintigraphy Versus 256-Slice CT Angiography in Pregnant Patients Suspected of Pulmonary Embolism: Comparison of Radiation Risks

et al. 2014

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One aim of the current study was to determine normalized dose data for maternal radiosensitive organs and embryo/fetus from 256-slice CT pulmonary angiography (CTPA) performed on pregnant patients suspected of having pulmonary embolism. A second aim was to provide reliable maternal and fetal doses and associated radiation cancer risk estimates from 256-slice CTPA and lung perfusion scintigraphy (LPS) for comparison. Methods: Mathematic anthropomorphic phantoms were generated to simulate the average woman at early pregnancy and at the third, sixth, and ninth months of gestation. In each phantom, 0-3 additional 1.5-cm-thick fat tissue layers were added to derive 4 phantoms representing pregnant women with different body sizes. Monte Carlo methods were used to simulate low-dose 256-slice CTPA exposures on each of the 16 generated phantoms. Normalized organ and embryo/fetal dose data were derived for exposures at 80, 100, and 120 kV. Maternal effective dose and embryo/fetal dose from 256-slice CTPA and associated lifetime attributable risks of radiation cancer were determined for different body sizes and gestational stages and compared with corresponding data from LPS. Results: For an average-sized pregnant patient at the first trimester, the 256-slice CTPA exposure resulted in a maternal effective dose of 1 mSv and an embryo/fetal dose of 0.05 mGy. However, maternal effective dose considerably increased with body size, whereas embryo/fetal dose increased with both body size and gestational stage. Compared with LPS, low-dose CTPA to an averagesized pregnant patient resulted in a 30% higher maternal effective dose but a 3.4-6 times lower embryo/fetal dose. Nevertheless, LPS was associated with less aggregated radiation risk for an average-sized pregnant patient, with the difference from CTPA being increased further for larger patients. Conclusion: Compared with CTPA performed with a modern wide-area CT scanner, LPS remains comparatively more dose-efficient.

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Section: Discussionmentioning

confidence: 87%

Perfusion Scintigraphy Versus 256-Slice CT Angiography in Pregnant Patients Suspected of Pulmonary Embolism: Comparison of Radiation Risks

et al. 2014

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“…More recently, Hurwitz et al (3) estimated fetal dose by using physical measurements from internal dosimeters in an anthropomorphic phantom that was modified to represent a newly pregnant patient and a patient who was 3 months pregnant.…”

Section: Iagnostic Computed Tomographicmentioning

confidence: 99%

Radiation Dose to the Fetus for Pregnant Patients Undergoing Multidetector CT Imaging: Monte Carlo Simulations Estimating Fetal Dose for a Range of Gestational Age and Patient Size

Angel¹,

Wellnitz²,

Goodsitt³

et al. 2008

Radiology

131

135

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Purpose:To use Monte Carlo simulations of a current-technology multidetector computed tomographic (CT) scanner to investigate fetal radiation dose resulting from an abdominal and pelvic examination for a range of actual patient anatomies that include variation in gestational age and maternal size. Materials and Methods:Institutional review board approval was obtained for this HIPAA-compliant retrospective study. Twenty-four models of maternal and fetal anatomy were created from image data from pregnant patients who had previously undergone clinically indicated CT examination. Gestational age ranged from less than 5 weeks to 36 weeks. Simulated helical scans of the abdominal and pelvic region were performed, and a normalized dose (in milligrays per 100 mAs) was calculated for each fetus. Stepwise multiple linear regression was performed to analyze the correlation of dose with gestational age and anatomic measurements of maternal size and fetal location. Results were compared with several existing fetal dose estimation methods. Results:Normalized fetal dose estimates from the Monte Carlo simulations ranged from 7.3 to 14.3 mGy/100 mAs, with an average of 10.8 mGy/100 mAs. Previous methods yielded values of 10 -14 mGy/100 mAs. The correlation between gestational age and fetal dose was not significant (P ϭ .543). Normalized fetal dose decreased linearly with increasing patient perimeter (R 2 ϭ 0.681, P Ͻ .001), and a two-factor model with patient perimeter and fetal depth demonstrated a strong correlation with fetal dose (R 2 ϭ 0.799, P Ͻ .002). Conclusion:A method for the estimation of fetal dose from models of actual patient anatomy that represented a range of gestational age and patient size was developed. Fetal dose correlated with maternal perimeter and varied more than previously recognized. This correlation improves when maternal size and fetal depth are combined. Note: This copy is for your personal, non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, use the Radiology Reprints form at the end of this article. D iagnostic computed tomographic(CT) imaging is sometimes necessary in a pregnant patient. When a radiologist needs to decide if the diagnostic benefits will outweigh the risks of radiation, it is important to have a reasonably accurate estimate of the radiation dose that the conceptus (fetus or embryo) will receive. Furthermore, in cases in which pregnancy is discovered during or after CT examination, the patient and/or physician may request an estimate of the radiation dose received by the conceptus. For the remainder of this article, the term fetus will be used to refer to either an embryo or a fetus and will therefore be used to describe a conceptus at any gestational age.It is not known definitively how much radiation dose a fetus receives during CT examination, because this cannot be measured directly. Some methods to estimate fetal dose exist, but these estimates are limited by their simplifying assumptions. Existing fetal dose estimation m...

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“…Hurwitz et al 9 estimated radiation dose to the female breast from 16-slice MDCT helical examinations using metal-oxidesemiconductor field-effect transistors ͑MOSFETs͒ in an anthropomorphic phantom. In separate efforts, Hurwitz et al 10 and Jaffe et al 11 developed methods to determine fetal radiation doses resulting from 16-slice MDCT using direct measurements of radiation-absorbed dose in an anthropomorphic phantom designed to simulate a gravid woman. More recently, Deak et al 12 estimated typical doses by calculating the energy deposition in a CTDI and anthropomorphic phantom using a collection of TLDs.…”

Section: Introductionmentioning

confidence: 99%

Variability of surface and center position radiation dose in MDCT: Monte Carlo simulations using CTDI and anthropomorphic phantoms

Zhang

Savandi²,

DeMarco

et al. 2009

Medical Physics

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The larger coverage afforded by wider z-axis beams in multidetector CT ͑MDCT͒ creates larger cone angles and greater beam divergence, which results in substantial surface dose variation for helical and contiguous axial scans. This study evaluates the variation of absorbed radiation dose in both cylindrical and anthropomorphic phantoms when performing helical or contiguous axial scans. The approach used here was to perform Monte Carlo simulations of a 64 slice MDCT. Simulations were performed with different radiation profiles ͑simulated beam widths͒ for a given collimation setting ͑nominal beam width͒ and for different pitch values and tube start angles. The magnitude of variation at the surface was evaluated under four different conditions: ͑a͒ a homogeneous CTDI phantom with different combinations of pitch and simulated beam widths, ͑b͒ a heterogeneous anthropomorphic phantom with one measured beam collimation and various pitch values, ͑c͒ a homogeneous CTDI phantom with fixed beam collimation and pitch, but with different tube start angles, and ͑d͒ pitch values that should minimize variations of surface dose-evaluated for both homogeneous and heterogeneous phantoms. For the CTDI phantom simulations, peripheral dose patterns showed variation with percent ripple as high as 65% when pitch is 1.5 and simulated beam width is equal to the nominal collimation. For the anterior surface dose on an anthropomorphic phantom, the percent ripple was as high as 40% when the pitch is 1.5 and simulated beam width is equal to the measured beam width. Low pitch values were shown to cause beam overlaps which created new peaks. Different x-ray tube start angles create shifts of the peripheral dose profiles. The start angle simulations showed that for a given table position, the surface dose could vary dramatically with minimum values that were 40% of the peak when all conditions are held constant except for the start angle. The last group of simulations showed that an "ideal" pitch value can be determined which reduces surface dose variations, but this pitch value must take into account the measured beam width. These results reveal the complexity of estimating surface dose and demonstrate a range of dose variability at surface positions for both homogeneous cylindrical and heterogeneous anthropomorphic phantoms. These findings have potential implications for small-sized dosimeter measurements in phantoms, such as with TLDs or small Farmer chambers.

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Radiation Dose to the Fetus from Body MDCT During Early Gestation

Cited by 223 publications

References 23 publications

Perfusion Scintigraphy Versus 256-Slice CT Angiography in Pregnant Patients Suspected of Pulmonary Embolism: Comparison of Radiation Risks

Perfusion Scintigraphy Versus 256-Slice CT Angiography in Pregnant Patients Suspected of Pulmonary Embolism: Comparison of Radiation Risks

Radiation Dose to the Fetus for Pregnant Patients Undergoing Multidetector CT Imaging: Monte Carlo Simulations Estimating Fetal Dose for a Range of Gestational Age and Patient Size

Variability of surface and center position radiation dose in MDCT: Monte Carlo simulations using CTDI and anthropomorphic phantoms

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