Radiation Dose to the Conceptus from Multidetector CT during Early Gestation: A Method That Allows for Variations in Maternal Body Size and Conceptus Position

Abstract

Purpose:To develop a method for estimating the radiation dose to the conceptus from multidetector computed tomography (CT) of the abdomen and pelvis in pregnant patients during the fi rst 7 weeks of gestation. Materials and Methods:This study was approved by the institutional review board and informed consent was obtained. A CT simulation software package was used to (a) develop voxelized models on the basis of image data from 117 nonpregnant patients who underwent abdominal and pelvic multidetector CT and (b) calculate dose at a position of the uterus assumed to be the position of the conceptus in case of pregnancy during the fi rst 7 weeks of gestation. Regression analysis was carried out to establish the relationship among conceptus dose, patient body size, and distance from the conceptus to the anterior skin surface. Results:Normalized conceptus doses calculated by using the software package ranged from 0.335 to 0.785 mGy per absorbed dose to air. Conceptus dose showed a signifi cant correlation with maternal body size and conceptus depth ( R 2 = 0.793, P , .001). A multivariable correlation of conceptus dose normalized to the free-in-air CT dose index (CTDI F ) with conceptus depth and patient perimeter was produced for estimating conceptus dose from abdominal and pelvic multidetector CT. Conceptus dose data provided for a specifi c scanner can be applied to other scanners by using correction factors based on ratios between the weighted CT dose index and CTDI F , resulting in inaccuracies in the estimation of conceptus dose of less than 12%. Conclusion:The radiation dose to the conceptus from abdominal and pelvic multidetector CT can be estimated with a method that allows for variations in maternal body size and conceptus position.q RSNA, 2010

Foetal Radiation Dose During Prophylactic Occlusion Balloon Placement for Morbidly Adherent Placenta

“…Furthermore, DAP-normalised doses show a decrease as BMI increases. Damilakis found a statistically significant relationship between normalised foetal dose and maternal body size and between normalised foetal dose and skin-to-foetal distance [32].…”

“…Mathematical phantoms simulating pregnancy during all trimesters of gestation have been used with the Monte Carlo N-particle program MCNP to estimate foetal dose [29]. In the later stages of pregnancy and especially during the 3rd trimester, foetal size and depth become crucial in estimating foetal dose [30][31][32]. It has been shown [30] that in the second and third trimester, the normalised conceptus dose may be 2.3 and 3.3 times greater, respectively, in comparison with that of the first trimester.…”

Computed Tomography Organ dose determination using ImPACT simulation software: Our findings in South-West Nigeria

“…These phantoms are usually cut into sections, which contain holes for the position of dosimeters. [26][27][28][29] More so, recent studies have estimated organ dose through the use of cadavers (postmortem studies). [30,31] The aim of this study was to first estimate each organ mean dose in: head (brain and eye lens), chest (lungs, breast, thyroid and heart), abdomen (stomach and liver) and pelvis (bladder and uterus), using the imPACT dose simulation software, to compare similar organ dose among the 7 CT units if they vary significantly, to determine range of percentage mean dose difference for this study and related study and to generally compare mean organ doses with international studies who used similar software and other methods (TLD and postmortem studies).…”

Abdominal CT during pregnancy: a phantom study on the effect of patient centring on conceptus radiation dose and image quality

“…On the contrary, a possible miscentring of the pregnant patient few centimeters (3 cm) above the gantry isocenter delivers roughly the same radiation dose to the conceptus compared to that at the isocenter with improved image quality. Several methods have been reported on the estimation of conceptus radiation dose in pregnant patients who are refered for CT examinations [7][8][9][10][11][12][13]. In these methods, pregnant patients are assumed to be correctly positioned at the isocenter.…”

“…The estimation of conceptus radiation dose is essential to determine radiogenic risks to the unborn child and inform the expectant mother [5,6]. Several studies have been published on conceptus radiation dose from CT examinations during pregnancy [7][8][9][10][11][12][13]. For the pregnant patient who needs CT, the most important element is to optimize the examination and keep conceptus radiation dose as low as reasonably achievable.…”