Effective Dose Conversion Research Articles

Use of secondary air kerma from dose area product and fluoroscopy time for preventive effective dose estimation in interventional radiology procedures for staff

Introduction: interventional radiology workers are potentially exposed to high levels of ionizing radiation, therefore preventive dose estimation is mandatory for the correct risk classification of staff. Effective dose (ED) is a radiation protection quantity strictly related to the secondary air kerma (K S), using appropriate multiplicative conversion factors (ICRP 106). The aim of this work is to evaluate the accuracy of K S estimated from physically measurable quantities such as dose-area product (DAP) or fluoroscopy time (FT). Methods: radiological units (n = 4) were characterized in terms of primary beam air kerma and DAP-meter response, consequently defining a DAP-meter correction factor (CF) for each unit. K S, scattered from an anthropomorphic phantom and measured by a digital multimeter, was then compared with the value estimated from DAP and FT. Different combinations of tube voltages, field sizes, current and scattering angles were used to simulate the variation of working conditions. Further measurements were performed to estimate the couch transmission factor for different phantom placements on the operational couch, defining a CF as the mean transmission factor. Results: when no CFs were applied, the measured K S showed a median percentage difference of between 33.8% and 115.7% with respect to K S evaluated from DAP, and between −46.3% and 101.8% for K S evaluated from FT. By contrast, when previously defined CFs were applied to the evaluated K S, the median percentage difference between the measured K S and the value evaluated from DAP ranged from between −7.94% and 15.0%, and between −66.2% and 17.2% for that evaluated from FT. Conclusion: when appropriate CF are applied, the preventive ED estimation from the median DAP value seems to be more conservative and easier to obtain with respect to the one obtained from the FT value. Further measurements should be performed with a personal dosimeter during routine activities to assess the proper K S to ED conversion factor.

Development of CT Effective Dose Conversion Factors from Clinical CT Examinations in the Republic of Korea

The aim of this study was to determine the conversion factors for the effective dose (ED) per dose length product (DLP) for various computed tomography (CT) protocols based on the 2007 recommendations of the International Commission on Radiological Protection (ICRP). CT dose data from 369 CT scanners and 13,625 patients were collected through a nationwide survey. Data from 3793 patients with a difference in height within 5% of computational human phantoms were selected to calculate ED and DLP. The anatomical CT scan ranges for 11 scan protocols (adult-10, pediatric-1) were determined by experts, and scan lengths were obtained by matching scan ranges to computational phantoms. ED and DLP were calculated using the NCICT program. For each CT protocol, ED/DLP conversion factors were calculated from ED and DLP. Estimated ED conversion factors were 0.00172, 0.00751, 0.00858, 0.01843, 0.01103, 0.02532, 0.01794, 0.02811, 0.02815, 0.02175, 0.00626, 0.00458, 0.00308, and 0.00233 mSv∙mGy−1∙cm−1 for the adult brain, intra-cranial angiography, C-spine, L-spine, neck, chest, abdomen and pelvis, coronary angiography, calcium scoring, aortography, and CT examinations of pediatric brain of <2 years, 4–6 years, 9–11 years, and 13–15 years, respectively. We determined ED conversion factors for 11 CT protocols using CT data obtained from a nationwide survey in Korea and Monte Carlo-based dose calculations.

Computed Tomography Dose in Paediatric Care: Simple Dose Estimation Using Dose Length Product Conversion Coefficients.

BackgroundThe use of multislice computed tomography (MSCT) is increasing worldwide; at the same time, there is a growing awareness of the future risk of cancer associated with greater exposure to radiation. Therefore, there is a need for an accessible method of effective dose estimation. This study aims to estimate the effective doses (EDs) of a variety of paediatric computed tomography (CT) examinations in five age groups using recently published age- and region-specific dose length products (DLPs) as effective dose conversion coefficients.MethodsA retrospective review was performed over a 12-month period. Patients were assigned to one of five age groups: neonatal, 1-, 5-, 10- and 15-years-old. Age- and region-specific conversion coefficients were applied to the DLP data displayed on the CT console in order to estimate the ED.ResultsOver the 12-month period, there were a total of 283 CT scans, 211 of which were selected for study. The ED estimates for plain CT brain scans in neonatal, 1-, 5-, 10- and 15-yearolds were 2.5, 1.5, 1.4, 1.3 and 0.8 mSv, respectively. For the corresponding CT abdominal scans, the results were 18.8, 12.9, 7.8, 8.6 and 7.5 mSv; these were the highest values recorded. High-resolution CT (HRCT) temporal scans showed EDs of 2.9, 1.8, 1.5 and 1.1 mSv in 1-, 5-, 10- and 15-years-old, respectively. CT scans of the helical thorax had an estimated ED of 4.8, 4.2 and 7.0 mSv in 5-, 10- and 15-years-old, respectively.ConclusionAn inverse relationship between age and effective dose was demonstrated in CT scans of the brain and abdomen/pelvis. In general, our study showed lower overall EDs compared to other centres.

Radiation dosimetry of the α4β2 nicotinic receptor ligand (+)-[18F]flubatine, comparing preclinical PET/MRI and PET/CT to first-in-human PET/CT results.

BackgroundBoth enantiomers of [18F]flubatine are new radioligands for neuroimaging of α4β2 nicotinic acetylcholine receptors with positron emission tomography (PET) exhibiting promising pharmacokinetics which makes them attractive for different clinical questions. In a previous preclinical study, the main advantage of (+)-[18F]flubatine compared to (−)-[18F]flubatine was its higher binding affinity suggesting that (+)-[18F]flubatine might be able to detect also slight reductions of α4β2 nAChRs and could be more sensitive than (−)-[18F]flubatine in early stages of Alzheimer’s disease. To support the clinical translation, we investigated a fully image-based internal dosimetry approach for (+)-[18F]flubatine, comparing mouse data collected on a preclinical PET/MRI system to piglet and first-in-human data acquired on a clinical PET/CT system. Time-activity curves (TACs) were obtained from the three species, the animal data extrapolated to human scale, exponentially fitted and the organ doses (OD), and effective dose (ED) calculated with OLINDA.ResultsThe excreting organs (urinary bladder, kidneys, and liver) receive the highest organ doses in all species. Hence, a renal/hepatobiliary excretion pathway can be assumed. In addition, the ED conversion factors of 12.1 μSv/MBq (mice), 14.3 μSv/MBq (piglets), and 23.0 μSv/MBq (humans) were calculated which are well within the order of magnitude as known from other 18F-labeled radiotracers.ConclusionsAlthough both enantiomers of [18F]flubatine exhibit different binding kinetics in the brain due to the respective affinities, the effective dose revealed no enantiomer-specific differences among the investigated species. The preclinical dosimetry and biodistribution of (+)-[18F]flubatine was shown and the feasibility of a dose assessment based on image data acquired on a small animal PET/MR and a clinical PET/CT was demonstrated. Additionally, the first-in-human study confirmed the tolerability of the radiation risk of (+)-[18F]flubatine imaging which is well within the range as caused by other 18F-labeled tracers. However, as shown in previous studies, the ED in humans is underestimated by up to 50 % using preclinical imaging for internal dosimetry. This fact needs to be considered when applying for first-in-human studies based on preclinical biokinetic data scaled to human anatomy.Electronic supplementary materialThe online version of this article (doi:10.1186/s40658-016-0160-5) contains supplementary material, which is available to authorized users.

Estimation of Radiation Dose Received in Knee Joint x-ray Examination

Abstract Background: Diagnostic X-ray examinations play an important role in the health care of the population. These examinations may involve significant irradiation of the patient and probably represent the largest manufactured source of radiation exposure for the population. Purpose: This study performed to assess the effective dose (ED) received in lumbosacral radiographic examination in order to analyze effective dose distributions among radiological departments under study. Materials and Methods: The study was performed in Khartoum teaching hospital, covering two x-ray units and a sample of 50 patients. The following parameters were recorded age, weight, height, body mass index (BMI) derived from weight (kg) and (height (m)) and exposure factors. The dose was measured for knee joint x-rays examination. For effective dose calculation, the entrance surface dose (ESD) values were estimated from the x-ray tube output parameters for knee joint AP and lateral examinations. The ED values were then calculated from the obtained ESD values using IAEA calculation methods. Effective doses were then calculated from energy imparted using ED conversion factors proposed by IAEA. Results: The results of ED values calculated showed that patient exposure were within the normal range of exposure. The mean ED values calculated were 2.49 +0.03 and 5.60 + 0.22 for knee joint AP and lateral examinations, respectively. Conclusion: Further studies are recommended with more number of patients and using more two modalities for comparison.

Estimates of effective dose for CT scans of the lower extremities.

To determine the dose-length product (DLP)-effective dose (ED) (DLP/ED) conversion coefficient (k) tables for the lower extremities that can be used for calculating ED. Dose calculations were performed on standard phantoms using a validated Monte Carlo calculation tool. Calculations were performed to obtain ED values for tube voltages from 80 kV to 140 kV in steps of 20 kV for the following examinations: hip (femur), knee, ankle, and computed tomographic (CT) angiography of the lower extremities. Values of the DLP were calculated by multiplying measured CT dose index values by the scan length; k values resulted as the quotients of the ED and DLP values. DLP/ED coefficients averaged over the range of voltage values and their standard deviations were determined for the given lower-extremity CT examinations for all age groups and for both sexes. Coefficients depend strongly on the phantom age and size, but little on the kilovolt value. In the case of the newborn, for example, k values were 0.0612, 0.0046, 0.0014, and 0.047 for hip, knee, ankle, and CT angiography, respectively, while in the case of the adult, these respective values were 0.0110, 0.0004, 0.0002, and 0.0062. A substantial difference up to 20% between coefficients in male and female phantoms was observed for CT angiographic examination. DLP/ED conversion coefficients are provided for lower extremities and allow estimation of ED for commonly used clinical musculoskeletal CT and CT angiographic protocols.

Accuracy of Effective Dose Estimation in Personal Dosimetry

The purpose of this study was three-fold: (1) to measure the transmission properties of various lead shielding materials, (2) to benchmark the accuracy of commercial film badge readings, and (3) to compare the accuracy of effective dose (ED) conversion factors (CF) of the U.S. Nuclear Regulatory Commission methods to the MOSFET method. The transmission properties of lead aprons and the accuracy of film badges were studied using an ion chamber and monitor. ED was determined using an adult male anthropomorphic phantom that was loaded with 20 diagnostic MOSFET detectors and scanned with a whole body CT protocol at 80, 100, and 120 kVp. One commercial film badge was placed at the collar and one at the waist. Individual organ doses and waist badge readings were corrected for lead apron attenuation. ED was computed using ICRP 103 tissue weighting factors, and ED CFs were calculated by taking the ratio of ED and badge reading. The measured single badge CFs were 0.01 (±14.9%), 0.02 (±9.49%), and 0.04 (±15.7%) for 80, 100, and 120 kVp, respectively. Current regulatory ED CF for the single badge method is 0.3; for the double-badge system, they are 0.04 (collar) and 1.5 (under lead apron at the waist). The double-badge system provides a better coefficient for the collar at 0.04; however, exposure readings under the apron are usually negligible to zero. Based on these findings, the authors recommend the use of ED CF of 0.01 for the single badge system from 80 kVp (effective energy 50.4 keV) data.

Radiation dose from 3D rotational X-ray imaging: organ and effective dose with conversion factors

The purpose of this study was to measure organ doses and the effective dose (ED) using a three-dimensional rotational X-ray (3D-RX) system and to determine the ED conversion factor from the dose area product (DAP) for skull, spine and biliary protocols. A commercial 3D-RX imaging system was used to simulate the protocols with the adult female anthropomorphic phantom. Twenty MOSFET detectors were used to measure the absorbed doses at various organ locations. The ED was calculated for each protocol and the corresponding DAP was obtained. The skin dose was the highest for all the protocols. The second highest organ doses were those of the brain for the skull, the intestine for the spine and the kidney for the biliary protocol. The ED was 0.4-0.9, 4.2-8.4 and 3.2-4.6 mSv, and the ED conversion factor was 0.06-0.09, 0.18-0.31 and 0.13-0.23 mSv Gy(-1) cm(-2) for each protocol, respectively. This data may be used to estimate the patient ED for those protocols in the 3D-RX.

TH-E-211-03: DLP to Effective Dose Conversion Factors for CT Based on ICRP 103

Purpose: ICRP report 103 updated tissue weighting factors for effective dose (ED) calculation. To determine the effective dose from CT scans, DLP‐to‐ ED conversion factors are needed. The purpose of this study was to determine such conversion factors for 7 models of scanners available in our practice. Methods: We used the IMPACT CT Patient dosimetry calculator to determine the DLP‐to‐ED conversion factors for brain, chest, abdomen‐ pelvis (abd/p) and chest‐abdomen‐pelvis (CAP) CT scans. A radiologist identified the beginning and end locations of each scan. The study included two 64‐slice scanners(GE LightSpeed VCT, Siemends Somatom Definition), two 16‐slice scanners(GE LightSpeed 16 and Toshiba Aquillion), two 4‐slice scanners(GE HiSpeed QX/I, Toshiba Asteion) and one two‐slice scanner(GE Nx/I 2). 120 kVp was used for all calculations with maximum collimation for each scanner, ranging from 20–40 mm. We calculated the DLP‐to‐ED factors for each scanner in addition to their average and standard deviation. For the sake comparison, we determined conversion factors based on ICRP 103 and ICRP 60. Results: In units of uSv/mGy cm, the average conversion factors for brain, chest, abd/p and CAP were 2.60, 19.9, 16.3 and 17.8, respectively. Their standard deviations were 0.15, 0.93, 1.14 and 0.90, respectively. The maximum deviations from the mean ranged from 10% to 12 % and were exhibited mostly by 2‐ and 4‐ slice scanners. The ratio of conversion factors based on ICRP 103 to those based on ICRP 60 ranged from 0.91 to 1.22. Conclusions: DLP‐to‐E conversion factors for brain, chest, abd/p and CAP scans were determined for several CTscanners based on ICRP 103. The conversion factors for each scanner or their overall average can be used to determine the effective dose.

Fluence to absorbed dose, effective dose and gray equivalent conversion coefficients for iron nuclei from 10 MeV to 1 TeV, calculated using Monte Carlo radiation transport code MCNPX 2.7.A

Conversion coefficients have been calculated for fluence-to-absorbed dose, fluence-to-effective dose and fluence-to-gray equivalent for isotropic exposure of an adult male and an adult female to (56)Fe(26+) in the energy range of 10 MeV to 1 TeV (0.01-1000 GeV). The coefficients were calculated using Monte Carlo transport code MCNPX 2.7.A and BodyBuilder 1.3 anthropomorphic phantoms modified to allow calculation of effective dose using tissues and tissue weighting factors from either the 1990 or 2007 recommendations of the International Commission on Radiological Protection (ICRP) and gray equivalent to selected tissues as recommended by the National Council on Radiation Protection and Measurements. Calculations using ICRP 2007 recommendations result in fluence-to-effective dose conversion coefficients that are almost identical at most energies to those calculated using ICRP 1990 recommendations.

Calculations of Effective Dose and Ambient Dose Equivalent Conversion Coefficients for High Energy Photons

The conversion coefficients from photon fluence to ambient dose equivalent, H* (10) and effective doses were calculated for photons up to 10 GeV. A Monte Carlo code EGS4 was used for these calculations and secondary particle transports were considered. The calculated ambient dose equivalents were compared to the calculated effective doses. The comparison shows that the ambient dose equivalents at 1 cm depth, H* (10) underestimate the effective doses at the energy above 5MeV. H* (10) is not suitable operational quantity since it does not provide reasonable estimation of effective dose. It is difficult to define the operational quantity which can be consistently used for photons from low energy to high energy above 10 MeV. Instead of operational quantities, the maximum effective dose in various irradiation geometries can be used for shielding design calculations.

Radiation burden to paediatric patients due to micturating cystourethrography examinations in a Dutch children's hospital.

Micturating cystourethrography (MCU) examinations of paediatric patients in a major Dutch children's hospital (JKZ) were evaluated to generate quantitative information on effective dose (E). A standard examination involves three radiographs plus fluoroscopy. Observed total dose-area product (DAP) for 84 children increased, on average, with increasing age class from 0.2 to 2.2 Gy cm2. In 11 cases, separate DAP per view was measured; enabling determination, per view, of organ (CF) and effective (CE) dose conversion factors, i.e. dose per unit of DAP. Monte Carlo simulation of photon transport in male and female mathematical phantoms was applied for newborn, 1 year, 5 year, 10 year and 15-year-old patients, and interpolated for other ages. CE per view decreases with increasing age class, yielding about a factor of 10 difference between the extremes of the range. Female values are usually some 20-30% above male ones. CE for one of the views appeared to be representative for the complete examination and was used to estimate total E for each patient. Averaged per age class, E remains approximately constant at 0.3-0.4 mSv, although a tendency to increase with increasing age exists, for females in particular. Within an age class, individual patients may differ in E by a factor of two up to six. Stomach, lower large intestine, bladder wall, liver and ovaries receive relatively high doses. Compared with published data and DAP measured in a few other Dutch hospitals, the radiation burden of MCU is low at the JKZ. This indicates a good degree of optimization with respect to radiation protection (e.g. modern equipment, increased tube voltage, fast film-screen combination).