Relationships between physical dose quantities and patient dose in CT.
ABSTRACT Patient dose in CT is usually expressed in terms of organ dose and effective dose. The latter is used as a measure of the stochastic risk. Determination of these doses by measurements or calculations can be time-consuming. We investigated the efficacy of physical dose quantities to describe the organ dose and effective dose. For various CT examinations of the head, neck and trunk, organ doses and effective doses were determined using conversion factors. Dose free-in-air on the axis of rotation (Dair) and weighted computed tomography dose index (CTDIw) were compared with the absorbed doses of organs which are located totally within the body region examined. Dose-length product (DLP) was compared with the effective dose. The ratio of the organ dose to CTDIw was 1.37 (0.87-1.79) mSv mGy-1. DLP showed a significant correlation with the effective dose (p < 0.005). The average ratio of effective dose to DLP was 0.28 x 10(-2) mSv (mGy cm)-1 for CT of the head, 0.62 x 10(-2) mSv (mGy cm)-1 for CT of the neck and 1.90 x 10(-2) mSv (mGy cm)-1 for CT of the trunk. CTDIw and DLP can be used for estimating the organ dose and effective dose associated with CT examinations of the head, neck and trunk.
SourceAvailable from: Mark F McEntee[Show abstract] [Hide abstract]
ABSTRACT: Objectives To evaluate visual grading characteristics (VGC) and ordinal regression analysis during head CT optimisation as a potential alternative to visual grading assessment (VGA), traditionally employed to score anatomical visualisation. Methods Patient images (n = 66) were obtained using current and optimised imaging protocols from two CT suites: a 16- slice scanner at the national Maltese centre for trauma and a 64-slice scanner in a private centre. Local resident radiologists (n = 6) performed VGA followed by VGC and ordinal regres- sion analysis. Results VGC alone indicated that optimised protocols had similar image quality as current protocols. Ordinal logistic regression analysis provided an in-depth evaluation, criterion by criterion allowing the selective implementation of the protocols. The local radiology review panel supported the implementation of optimised protocols for brain CT examina- tions (including trauma) in one centre, achieving radiation dose reductions ranging from 24 % to 36 %. In the second centre a 29 % reduction in radiation dose was achieved for follow-up cases. Conclusions The combined use of VGC and ordinal logistic regression analysis led to clinical decisions being taken on theimplementation of the optimised protocols. This improved method of image quality analysis provided the evidence to support imaging protocol optimisation, resulting in significant radiation dose savings. Main Messages • There is need for scientifically based image quality evaluation during CT optimisation. • VGC and ordinal regression analysis in combination led to better informed clinical decisions. • VGC and ordinal regression analysis led to dose reductions without compromising diagnostic efficacy.12/2014; DOI:10.1007/s13244-014-0374-9
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ABSTRACT: Computed Tomography (CT) procedures constitute the 5% of the total diagnostic radiology and provide more than the 40% of the total dose. Patient dose depends on many factors; most of them depend on the way the procedure is performed. All around the world, there is a growing interest in studying patient dose in CT procedures in order to optimize them. If the patient is pregnant, conceptus absorbed dose can be high and radiation risks during pregnancy are well established. Uruguay has 35 CT scanners and 70.000 procedures are performed per year in a total population of 3.1 million people. However, neither patient nor conceptus doses in CT procedures have still been evaluated. The main objective of this paper is to estimate fetus/embryo absorbed doses in abdomen-pelvis CT procedures in order to make radiologists and technicians realize their responsibility in CT procedures performance, especially in pregnant and females of childbearing age. The investigation was performed in the Radiology Department of the University Hospital "Dr. Manuel Quintela". A 41 patient sample was taken to know average technical parameters used in abdomen and abdomen-pelvis CT procedures. Methods considering CT Dose Index (CTDI) in the centre of a head phantom were applied to estimate fetus absorbed dose. Results were 22 mGy in abdomen-pelvis procedure and 3 mGy in abdomen procedure. Real values may be higher if the procedures are performed with and without contrast media (barium or iodine). Results make necessary the establishing of a radiation protection protocol of the handling of pregnant patients and females of childbearing age. For this, it is essential that radiologists and technicians receive specific education in CT radiation protection.
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ABSTRACT: In this study measured patient exposure dose for purpose exposure area and peripheral critical organs by using optically stimulated luminescence dosimeters (OSLDs) from computed tomography (CT), based on the measurement results, we predicted the radiobiological effects, and would like to advised ways of reduction strategies. In order to experiment, OSLDs received calibration factor were attached at left and right lens, thyroid, field center, and sexual gland in human body standard phantom that is recommended in ICRP, and we simulated exposure dose of patients in same condition that equal exposure condition according to examination area. Average calibration factor of OSLDs were . In case of left and right lens, equivalent dose was measure in 50.49 mGy in skull examination, 0.24 mGy in chest, under standard value in abdomen, lumbar spine and pelvis. In case of thyroid, equivalent dose was measured in 10.89 mGy in skull examination, 7.75 mGy in chest, 0.06 mGy in abdomen, under standard value in lumber spine and pelvis. In case of sexual gland, equivalent dose was measured in 21.98 mGy, 2.37 mGy in lumber spine, 6.29 mGy in abdomen, under standard value in skull examination. Reduction strategies about diagnosis reference level (DRL) in CT examination needed fair interpretation and institutional support recommending international organization. So, we met validity for minimize exposure of patients, systematize influence about exposure dose of patients and minimize unnecessary exposure of tissue.04/2013; 7(2). DOI:10.7742/jksr.2013.7.2.121