Calculation Of Effective Dose Research Articles

Spatial distribution of radon concentration and risk evaluation through consumption of groundwater in the District of Kotli, Azad Jammu and Kashmir

Radon (222Rn) is naturally readily water-soluble, posing a cancer risk to the exposed community. Human exposure in the community may occur via 222Rn intake in drinking water. Groundwater is used for drinking and other domestic purposes in the region. Higher concentrations of 222Rn in groundwater have been reported near Kotli district, Azad Jammu, and Kashmir. This investigation aimed to measure 222Rn concentrations in groundwater and evaluate the associated risk assessment for children and adults in the Kotli district. 222Rn concentrations were measured in randomly collected groundwater samples of Kotli (n = 25) and Sehnsa (n = 15) towns in the Kotli district using the portable Radon Detector (RAD7, Durridge Company, United States of America). Among the studied areas, the Sehnsa showed a higher average 222Rn concentration (7.6 ± 0.2 Bq/L) in groundwater compared to Kotli (6.0 ± 1.9 Bq/L). The average concentrations of 222Rn were found within the recommended limit (11.1 Bq/L) of the United States Environmental Protection Agency (USEPA), except for 10% of sampling sites. 222Rn concentrations were used for the calculation of total effective dose for ingestion and inhalation pathways (EwTotal) values for infants (24.5 ± 7.5 and 30.7 ± 0.9 μSv/a), children (18.1 ± 5.5 and 23.5 ± 0.7 μSv/a), and adults (18.1 ± 5.5 and 22.7 ± 0.3 μSv/a) in the Kotli and Sehnsa, respectively. This study noted that EwTotal and estimated lifetime cancer risk (ELCR) values were found within the World Health Organization (WHO) and European Commission (EU) acceptable limits (<100 μ Sv/a and 0.1 × 10−3).

Risk Factors for Radiotherapy Failure in the Treatment of Spinal Metastases.

Retrospective cohort study. To build a predictive model for risk factors for failure of radiation therapy, hypothesizing a higher SINS would correlate with failure. Patients with spinal metastasis being treated with radiation at a tertiary care academic center between September 2014 and October 2018 were identified. The primary outcome measure was radiation therapy failure as defined by persistent pain, need for re-irradiation, or surgical intervention. Risk factors were primary tumor type, Karnofsky and ECOG scores, time to treatment, biologically effective dose (BED) calculations using α/β ratio = 10, and radiation modality. A logistic regression was used to construct a prediction model for radiation therapy failure. One hundred and seventy patients were included. Median follow up was 91.5days. Forty-three patients failed radiation therapy. Of those patients, 10 required repeat radiation and 7 underwent surgery. Thirty-six patients reported no pain relief, including some that required re-irradiation and surgery. Total SINS score for those who failed reduction therapy was <7 for 27 patients (62.8%), between 7-12 for 14 patients (32.6%), and >12 for 2 patients (4.6%). In the final prediction model, BED (OR .451 for BED > 43 compared to BED ≤ 43; P = .174), Karnofksy score (OR .736 for every 10 unit increase in Karnofksy score; P = .008), and gender (OR 2.147 for male compared to female; P = .053) are associated with risk of radiation failure (AUC .695). A statistically significant association between SINS score and radiation therapy failure was not found. In the multivariable model, BED ≤ 43, lower Karnofksy score, and male gender are predictive for radiotherapy failure. SINS score was among the candidate risk factors included in multivariable model building procedure, but it was not selected in the final model. Prognostic level III.

Estimation of radiation dose due to thoron and progeny inhalation in high background natural radiation area of Odisha, India

Abstract Results of the preliminary measurements of indoor radon, thoron and progeny concentrations showed very high values of thoron concentrations in the eastern coastal region of Odisha, India. Therefore, measurements of thoron and its progeny concentrations were extended to a larger number of houses in this area for the assessment of the radiation dose received by the public. The measured values of thoron concentrations were used for the calculation of annual effective doses. The estimated values of the annual effective dose due to thoron exposure were observed in the range of 0.2–14.7 mSv. The estimated radiation doses responsible for thoron exposure were observed considerably high in the region. The results obtained are compared with those obtained in other studies performed so far in the study area and a review of different studies involving different measurement techniques is presented in the paper. The results of this study support the preliminary studies showing high values of thoron levels in the study area.

Calculation of effective dose of phenylephrine bolus for treatment of post-spinal hypotension in pre-eclamptic patients undergoing caesarean section – a non-randomised controlled trial

BackgroundPatients with pre-eclampsia require smaller vasopressor doses compared with those with normotension for management of post-spinal hypotension during caesarean section. However, the literature has little evidence as to the phenylephrine dose required for patients with pre-eclampsia. MethodsFifty patients, with either pre-eclampsia or normotension, and developing post-spinal hypotension during caesarean section under spinal anaesthesia, were studied. Women in both groups did not receive prophylactic vasopressors. The first patient in each group received phenylephrine 50 µg to treat the first episode of hypotension, defined as fall of systolic blood pressure ≥20% from baseline or an absolute value <100 mmHg. If hypotension was corrected within one minute it was considered a ‘success’. The doses for the subsequent patients were determined by responses to all previous patients, according to a variation of Narayana’s rule for the up-down sequential allocation method. ResultsThe 95% effective dose (ED95) and 50% effective dose (ED50) of phenylephrine was 41.7 µg (95% CI 33.8 to 49.6 µg) and 29.1 µg (95% CI 26.0 to 32.2 µg) respectively in the pre-eclampsia group, and 64.9 µg (95% CI 54.1 to 75.7 µg) and 47.3 µg (95% CI 39.7 to 54.9 µg) respectively in the normotensive group. The proportionate reduction in phenylephrine dose ranged from 33% (95% CI 18 to 44%) to 40% (95% CI 19 to 52%). ConclusionPatients with pre-eclampsia may need a 33% to 40% reduction in the first phenylephrine bolus dose, compared with patients with normotension, for the treatment of the first episode of post-spinal hypotension.

Report on the PET/CT Image-Based Radiation Dosimetry of [18F]FDHT in Women, a Validated Imaging Agent with New Applications for Evaluation of Androgen Receptor Status in Women with Metastatic Breast Cancer.

In a prospective clinical trial, [18F]fluoro-5α-dihydrotestosterone ([18F]FDHT), the radiolabeled analog of the androgen dihydrotestosterone, was used as a PET/CT imaging agent for invivo assessment of metastatic androgen receptor-positive breast cancer in postmenopausal women. To our knowledge, this article presents the first report of PET/CT image-based radiation dosimetry of [18F]FDHT in women. Methods: [18F]FDHT PET/CT imaging was performed on a cohort of 11 women at baseline before the start of therapy and at 2 additional time points during selective androgen receptor modulator (SARM) therapy for androgen receptor-positive breast cancer. Volumes of interest (VOIs) were placed over the whole body and within source organs seen on the PET/CT images, and the time-integrated activity coefficients of [18F]FDHT were derived. The time-integrated activity coefficients for the urinary bladder were calculated using the dynamic urinary bladder model in OLINDA/EXM software, with biologic half-life for urinary excretion derived from VOI measurements of the whole body in postvoid PET/CT images. The time-integrated activity coefficients for all other organs were calculated from VOI measurements in the organs and the physical half-life of 18F. Organ dose and effective dose calculations were then performed using MIRDcalc, version 1.1. Results: At baseline before SARM therapy, the effective dose for [18F]FDHT in women was calculated as 0.020 ± 0.0005 mSv/MBq, and the urinary bladder was the organ at risk, with an average absorbed dose of 0.074 ± 0.011 mGy/MBq. Statistically significant decreases in liver SUV or uptake of [18F]FDHT were found at the 2 additional time points on SARM therapy (linear mixed model, P < 0.05). Likewise, absorbed dose to the liver also decreased by a small but statistically significant amount at the 2 additional time points (linear mixed model, P < 0.05). Neighboring abdominal organs of the gallbladder wall, stomach, pancreas, and adrenals also showed statistically significant decreases in absorbed dose (linear mixed model, P < 0.05). The urinary bladder wall remained the organ at risk at all time points. Absorbed dose to the urinary bladder wall did not show statistically significant changes from baseline at any of the time points (linear mixed model, P ≥ 0.05). Effective dose also did not show statistically significant changes from baseline (linear mixed model, P ≥ 0.05). Conclusion: Effective dose for [18F]FDHT in women before SARM therapy was calculated as 0.020 ± 0.0005 mSv/MBq. The urinary bladder wall was the organ at risk, with an absorbed dose of 0.074 ± 0.011 mGy/MBq.

Image quality and radiation dose in spinal surgery: a comparison of three imaging systems in phantom.

Using optimal settings for x-ray scans is crucial for obtaining three-dimensional images of high quality while keeping the patient dose low. Our work compares dose and image quality (IQ) of three intraoperative imaging systems [O-arm cone-beam computed tomography (CBCT), ClarifEye C-arm CBCT, and Airo computed tomography] used for spinal surgery. Patients of 70, 90, and 110kg were simulated with an anthropomorphic phantom by adding tissue-equivalent material. Titanium inserts were placed in the phantom spine for reproducing metal artifacts in the images. Organ dose was measured with thermo-luminescent dosimeters for effective dose () calculation. Subjective IQ was assessed by ranking the images acquired with the manufacturer-defined imaging protocols. Objective IQ was assessed with a customized Catphan phantom. The ClarifEye protocols resulted in the lowest ranging from 1.4 to 5.1mSv according to phantom size and protocol. The highest was measured for the high-definition protocol of O-arm ( 2.2 to 9mSv) providing the best subjective IQ for imaging of the spine without titanium inserts. For the images with metal, the best IQ was obtained with ClarifEye. Airo ( 5.5 to 8.4mSv) was ranked with the lowest IQ for images without metal while the rank improved for images with metal. Airo images had better uniformity, noise, and contrast sensitivity compared with CBCTs but worse high-contrast resolution. The values of these parameters were comparable between the CBCT systems. Both CBCT systems provided better IQ compared with Airo for navigation of lumbar spinal surgery for the original phantom. Metal artifacts particularly affect O-arm images decreasing the subjective IQ. The high spatial resolution of CBCT systems resulted in a relevant parameter for the visibility of anatomical features important for spine navigation. Low dose protocols were enough to obtain a clinically acceptable contrast-to-noise ratio in the bones.

Current Status of TRIPOLI-4® Monte Carlo Radiation Transport Code on Adult and Pediatric Computational Phantoms for Radiation Dosimetry Study

TRIPOLI-4® is a general-purpose Monte Carlo radiation transport code developed by the Service d’Études des Réacteurs et de Mathématiques Appliquées at CEA-Saclay. It uses continuous-energy nuclear data to simulate neutron, photon, electron, and positron transport in fields like radiation shielding, reactor physics, and nuclear criticality safety. To study radiation protection dosimetry in human tissues and organs, male and female adult computational phantoms from the Medical Internal Radiation Dose–Oak Ridge National Laboratory phantoms family and the International Commission on Radiological Protection (ICRP) publication 110 were recently modeled and calculated using the geometry options of TRIPOLI-4. To easily use the ICRP 110 voxel-based phantoms in different exposure scenarios, a newly developed phantom option is available in TRIPOLI-4 and its display tool T4G. This new phantom option is helpful for modeling one or more phantoms and for improving calculation performance in real irradiation environments. The 2020 published pediatric computational reference phantoms are accessible from ICRP publication 143. Male and female pediatric phantoms are also verified with the new T4G tool and TRIPOLI-4 code. This paper reports on recent works using TRIPOLI-4 on adult and pediatric computational phantoms. The modeling methods of stylized and voxel-based phantoms, the graphic displays of modeled phantoms with T4G, and the verification procedures for single-phantom and two-phantom application cases are presented. Validation for external and internal dosimetry calculations has been performed. Calculation results on organ dose S values for nuclear medicine applications are presented for single female and single male voxel phantoms using 131I and 177Lu radiation sources. Effective dose calculations for two-phantom cases using 99mTc and 18F sources are compared with traditional H*(10) calculations from nuclear medicine patient to patient caregiver.

New skeletal dose coefficients of the ICRP-110 reference phantoms for idealized external fields to photons and neutrons using dose response functions (DRFs)

The International Commission on Radiological Protection (ICRP) Publication 116 was released to provide a comprehensive dataset of the dose coefficients (DCs) for external exposures produced with the adult reference voxel phantoms of ICRP Publication 110. Although an advanced skeletal dosimetry method for photons and neutrons using fluence-to-dose response functions (DRFs) was introduced in ICRP Publication 116, the ICRP-116 skeletal DCs were calculated by using the simple method conventionally used (i.e., doses to red bone marrow and endosteum approximated by doses to spongiosa and/or medullary cavities). In the present study, the photon and neutron DRFs were used to produce skeletal DCs of the ICRP-110 reference phantoms, which were then compared with the ICRP-116 DCs. For photons, there were significant differences by up to ∼2.8 times especially at energies <0.3 MeV. For neutrons, the differences were generally small over the entire energy region (mostly <20%). The general impact of the DRF-based skeletal DCs on the effective dose calculations was negligibly small, supporting the validity of the ICRP-116 effective DCs despite their skeletal DCs derived from the simple method. Meanwhile, we believe that the DRF-based skeletal DCs could be beneficial in better estimates of skeletal doses of individuals for risk assessments.

Radiation detriment estimation: on the possibility of effective dose usage to assess the number of years of the healthy life lost

The Russian Law “On Radiation Safety of the Population” defines the effective dose as “the amount of exposure to ionizing radiation used as a measure of the risk of long-term consequences of human’s body exposure…” In turn, the Russian “Radiation Safety Standards” (RSS 99/2009) establish a procedure for assessing the health risk, associated with exposure to low doses, for two types of harmful effects (oncological diseases and hereditary effects) and two age and sex groups (“whole population” and “adults”) by multiplying corresponding linear risk coefficients per effective dose. At the same time, these documents do not impose restrictions on the risk assessment procedure, without excluding the use of any other risk indicators or risk assessment for other sex and age groups of the population. The value of radiation detriment to health, calculated by the method described in RSS 99/2009 to characterize the risk, as a unit of measurement, uses the fatal oncological disease caused by exposure to ionizing radiation, weighted by the number of years of life lost, or weighted by the severity of non-fatal cancer. Currently, mortality-based health measures are considered insufficiently informative characteristics of the impact of external factors on population health. Such indicators are poorly suited for a comparative analysis of risks, especially taking into account the different distribution of negative consequences over time. The paper presents an applied approach to expand the application of the radiation risk assessment methodology, without making significant changes to the established practice of radiation protection. The possibility of using the DALY value (disability-adjusted life years) as an measure of radiation risk is being considered; the expediency of changing approaches to calculating the effective dose (by using different values of weighting factors for tissues and organs during effective dose calculation for different age and sex groups of the population) and the possible scope of the proposed approaches to risk assessment in practice are discussed; an approach is proposed for calculating the DALY value using the effective dose and the corresponding risk factors (DALY×Sv-1).

СТАТИСТИЧЕСКИЙ АНАЛИЗ ДОЗ ВНУТРЕННЕГО ОБЛУЧЕНИЯ НАСЕЛЕНИЯ ЛУНИНЕЦКОГО РАЙОНА БРЕСТСКОЙ ОБЛАСТИ ЗА 2015–2019 ГОДЫ

We formed the database which included the main identification indicators about people living in the 137Cs-contaminated territory (Luninets district, Brest region). The calculation and assessment of annual effective doses from internal exposure was carried out based on the results of 58809 measurements. We were using the human radiation spectrometer (HRS) to make measurements in the formed cohort during 5 years (from 2015 till 2019). We found that internal exposure doses are the sum of two distributions. 83.3% of HRS measurements form the main mode of the bimodal distribution. It is close to the normal distribution and different in gender and age features of internal exposure dose formation. The second mode of data distribution is different in significantly higher values of the internal doses and some other parameters like a sex and age.

Conservation of pyramidal tract in radiosurgery for brain metastases of lung adenocarcinoma: Three-dimensional analysis of biologically effective dose

BackgroundGamma knife surgery (GKS) for brain metastases (BMs) adjacent to the pyramidal tract (PT) is still a challenge to conduct. PT visualization and biologically effective dose (BED) calculation on a voxel-by-voxel basis may provide data to establish clinically safe values. We aimed to assess the relationship of parameters extracted from the BED-volume histogram with outcomes of PT after GKS-treating target (adjacent BM of lung adenocarcinoma). MethodsWe formed BED-volume histograms for 672 BMs in a retrospective cohort, using 3-dimensional (3D) coordinate values of PT, target, and each iso-centre to calculate the 3D BED distribution in a 200 × 200 × 200 matrix. PT conservation failure (PTCF) was judged clinically and radiologically and classified as lesion progression and radionecrosis. Cox proportional hazards models were used to analyse 3D BED parameters. Internal validation of models was performed by bootstrapping. ResultsThere were 116 (17.3 %) subjects with PTCF in the cohort, of which 74 (11.0 %) and 42 (6.3 %) were caused by lesion progression and radionecrosis, respectively. Multivariate analysis showed that DLesion_min BED and DLesion_90% BED significantly predicted lesion progression (P <.001). DPT_Max BED and VPT_ BED40 significantly predicted radionecrosis (P <.001). The model predicting PTCF showed fair discrimination and calibration of DLesion_min BED + DLesion_90% BED and DPT_Max BED + VPT_ BED40. ConclusionsThe conservation of PT in GKS for BMs of lung adenocarcinoma depends on the combination of PT-tolerated BED and target effective control BED. Therefore, a BED-volume histogram with a 3D BED algorithm is proposed to assess plan quality.

Activity concentration and annual effective dose assessments of radon in SCCs with different mineral additives

This study was conducted to investigate the hypothesis that radon gas emanation which is harmful to human health may occur more than standard values in Self-Compacting Concrete (SCC) which has a higher amount of dust material than conventional concretes. The SCCs with 5 %, 12.5 %, and 20 % fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBFS) as well as control concretes without mineral additives were placed closed glass environments with dimensions of 150×150×150 mm; average radon activity concentrations (ARACs) were measured passive method by CR-39 nuclear trace detectors after 7–14-21–28-56–90 and 120 days. Radioactivity analyses including annual effective equivalent dose (AEED) calculation of the concretes were also done. The ARAC values of SCCs increased significantly along with the increase of FA and decreased significantly with the increase of SF. So that the ARAC value (131.56 Bq/m3) of SCC with 20 % FA increased 2.40-fold when compared to the control concrete; however, the ARAC value (14.22 Bq/m3) of SCCs containing 20 % SF was found 4.5-fold lower than the control concrete. 5 % of the concretes containing GGBFS reduced the radon gas emanation; however, the rates of 12.5 % and 20 % increased the emanation. The highest AEEDs for each mineral additive type were 7-day samples including 20 % of FA (8.00 mSv/year), 5 % of GGBFS (3.17 mSv/year) and 5 % of SF (2.16 mSv/year). 12.5 % and 20 % FA-added SCCs emit radon gas above the limit levels. The results have confirmed the hypotheses of the present research depending on the mineral additive type and rate.

Radiation Dose Optimization Based on Saudi National Diagnostic Reference Levels and Effective Dose Calculation for Computed Tomography Imaging: A Unicentral Cohort Study

Few studies have reviewed the reduction of doses in Computed tomography (CT), while various diagnostic procedures use ionizing radiation to explore the optimal dose estimate using multiple exposure quantities, including milliampere-seconds, kilovoltage peak, and pitch factors while controlling the CT dose index volume (CTDIvol) and dose length product (DLP). Therefore, we considered optimizing CT protocols to reduce radiation and organ doses during head, chest, abdominal, and pelvic CT examinations. For establishing institutional diagnostic reference levels as a benchmark to correlate with national diagnostic reference levels (NDRLs) in KSA conforming to international guidelines for radiation exposure, 3000 adult-patients underwent imaging of organs. Dose parameters were obtained using Monte Carlo software and adjusted using the Siemens Teamplay™ software. CTDIvol, DLP, and effective dose were 40.67 ± 3.8, 757 ± 63.2, and 1.74 ± 0.19, for head; 14.9 ± 1.38, 547 ± 42.9, and 7.27 ± 0.95 for chest; and 16.84 ± 1.45, 658 ± 53.4, and 10.2 ± 0.66 for abdomen/pelvis, respectively. The NDRL post-optimization comparison showed adequate CT exposure. Head CT parameters required additional optimization to match the NDRL. Therefore, calculations were repeated to assess radiation doses. In conclusion, doses could be substantially minimized by selecting parameters per clinical indication of the study, patient size, and examined body region. Additional dose reduction to superficial organs requires a shielding material.

PHSPP04 Presentation Time: 3:00 PM: The Impact of Sublethal Damage Repair on Biological Dose for a Stepping-Source Brachytherapy Delivery in a Single-Fraction Prostate Treatment

<h3>Purpose</h3> Single-fraction (1-fx) ¹⁹²Ir prostate high-dose-rate (HDR) brachytherapy prescriptions of 19-20 Gy were derived using the biologically effective dose (BED) calculation in its simplified traditional (BED_T) form, BED_T=nd(1+d/α/β). This form of BED, while extremely convenient, was an approximation predicated on instantaneous delivery and may not be an appropriate assumption in certain key scenarios: protracted delivery times (> 15 minutes), high dose/fx (> 5 Gy), late-reacting tissues (low α/β), and/or rapid sublethal damage repair half-time (< 2x delivery time). As these are all characteristic of 1-fx prostate HDR brachytherapy, the aim of this study was to examine the difference between BED_T and BED by development of a computational framework that can perform patient-specific high-resolution volumetric BED calculations that explicitly consider the effects of dose protraction and the unique temporal sequences arising from the stepping-source delivery. <h3>Materials and Methods</h3> The Lea-Catcheside dose protraction factor, g, was calculated to modify the multi-track term of the linear-quadratic model, such that BED=nd(1+gd/α/β). BED_T corresponds to the special situation where g=1. For calculations, α/β=3.0 Gy and characteristic sublethal damage repair half-time of 0.27 hours were drawn from AAPM TG-137 radiobiological values, with assumed mono-exponential repair kinetics. For the stepping-source form of dose protraction factor, g_ss, a script was developed to sequentially calculate the dose rates as a function of time, for each voxel in the calculation grid, from all individual dwell positions based on position and angular orientation extracted from a plan DICOM file using an AAPM TG-43/43U dose-rate calculation methodology. Together with the temporal ordering of dwell positions extracted from DICOM, the script provided a matrix of g_ss values on a voxel-by-voxel basis with 1.0 × 1.0 × 1.0 mm³ resolution. A second form of the dose protraction factor g₀, a commonly-used factor in LDR brachytherapy, was also calculated which approximated the entire delivery as time-averaged uniform dose-rate. BED_T (g=1) was then compared to BED calculated with actual values of g₀ and g_ss values. <h3>Results</h3> The DICOM files from a previously-treated patient with representative dose characteristics were imported into our script: a prescription of 19 Gy in 1-fx, 140 active dwell positions in 17 channels, and delivery time of 2076.1 seconds based on 17500 U (4.3 Ci) source strength. An axial slice showing a color wash of the BED (Gy₃) ranging from 139.3-519.0 Gy₃ (physical dose: 19-38 Gy in 1-fx) is shown for g=1 (BED_T), g₀, and g_ss in Figure 1 which demonstrated significant differences. The nominal BED_T was 139.3 Gy, which was reduced by 31% using g₀ and, depending on location, reduced between 20-31% using g_ss. The portion of the PTV covered by 139.3 Gy₃ prescription was 95.9%, 59.6% and 65.7% using g=1 (BED_T), g₀, and g_ss, respectively. Using g=1 (BED_T), g₀, and g_ss, 90% of the PTV was covered by 159.4 Gy₃, 110.4 Gy₃, and 112.9 Gy₃, respectively. <h3>Conclusions</h3> A custom script, capable of recalculating BED on a voxel-by-voxel level with proper accounting of sublethal damage repair arising from protracted dose delivery was developed. Significant differences in BED (∼30%) were shown for 1-fx prostate HDR brachytherapy. Two other general trends emerged in this study: 1) g₀, while simple, provided a lower bound to volumetric g_ss values. 2) Voxels closer to an activated dwell position were more resistant to dose protraction effects in an effect we attribute to effective delivery time: the time in which the dose-rate was significantly elevated (>2 orders of magnitude).

Updated National Diagnostic Reference Levels and Achievable Doses for CT Protocols: A National Survey of Korean Hospitals.

Background: In 2021, the Korean government proposed a new CT diagnostic reference level. This study performed a nationwide survey and developed new DRLs and AD for 13 common CT examinations. We compared other countries’ DRLs for CT examinations. Methods: This study investigated the CTDIvol and DLP of the 12 types of CT protocols for adults and brain CT protocol for pediatrics. A total of 7829 CT examinations were performed using 225 scanners. We defined the DRLs values in the distribution of radiation exposure levels to determine the nationwide patient dose and distribution status of the dose. Results: This study showed that the new Korean national CT DRLs are slightly higher or similar to those of previous surveys and are similar or lower than those of other countries. In some protocols, although the DLP value increased, the CTDIvol decreased; therefore, it can be concluded that the patient’s dose in CT examinations was well managed. Conclusions: The new CT DRLs were slightly higher than or similar to that of the previous survey and were evaluated to be similar or lower than CT DRLs of other countries. These DRLs will be used for radiation optimization and effective dose calculation for an individual.

Incorporation of micro-CT-based detailed bone models into ICRP adult mesh-type reference computational phantoms

Objective. The red bone marrow (RBM) and bone endosteum (BE), which are required for effective dose calculation, are macroscopically modeled in the reference phantoms of the international commission on radiological protection (ICRP) due to their microscopic and complex histology. In the present study, the detailed bone models were developed to simplify the dose calculation process for skeletal dosimetry. Approach. The detailed bone models were developed based on the bone models developed at the University of Florida. A new method was used to update the definition of BE region by storing the BE location indices using virtual sub-voxels. The detailed bone models were then installed in the spongiosa regions of the ICRP mesh-type reference computational phantoms (MRCPs) via the parallel geometry feature of the Geant4 code. Main results. Comparing the results between the detailed-bone-installed MRCPs and the original MRCPs with the absorbed dose to spongiosa and fluence-to-dose response function (DRF)-based methods, the DRF-based method showed much smaller but still significant differences. Compared with the values given in ICRP Publications 116 and 133, the differences were very large (i.e. several orders of magnitudes), due mainly to the anatomical improvement of the skeletal system in the MRCPs; that is, spongiosa and medullary cavity are fully enclosed by cortical bone in the MRCPs but not in the ICRP-110 phantoms. Significance. The detailed bone models enable the direct calculation of the absorbed doses to the RBM and BE, simplifying the dose calculation process and potentially improving the consistency and accuracy of skeletal dosimetry.

Effective doses in chest and abdominal radiography following the ICRP recommendations of 1991 and 2007 in a regional hospital.

Background: In 2007, the International Commission for Radiological Protection (ICRP), published a new set of tissues and tissue weighting factors as recommendations in the ICRP publication 103. This altered the parameters contributing to the calculation of effective dose, which is normally used as a single indicator of risk. Purpose: To assess the effect of the 2007 review of tissue weighting factors on measured doses in a clinical setting, using patient doses for chest (CXR) and abdominal (AXR) radiography. Materials &amp; Methods: Patient entrance surface doses(ESD) obtained in a dose audit for chest (CXR) and abdomen (AXR) examinations with Harshaw type Lithium Fluoride thermoluminescent dosemeters (LiF-TLD 100) were used in a Monte Carlo calculation software, XDOSE, developed by the National Radiation Protection Board (NRPB) to calculate organ doses. Effective doses (E mSv) were calculated with both the ICRP 1991 and 2007 recommendations of tissue weighting factors. A 2-sample t-statistic was used to test for differences between the results for both recommendations. Tests were at the 95% confidence interval. Results: The mean effective doses for CXR were found to be 0.04 (range 0.019 to 0.092) mSv and 0.03 (range 0.011 to 0.069) mSv for the 1991 and 2007 recommendations, respectively. Mean abdominal effective dose values were 0.78 (range 0.16 to 2.98) mSv for the 1991 wƮ factors, and 0.49 (range 0.099 to 1.97) mSv for the 2007 recommended factors. The mean percentage difference between the effective doses calculated with wƮ recommendations of 1991 and 2007 respectively came to 1.7 ± 0.6 % with a range between 0.8 and 3.3 % for CXR (p &lt; 0.05) and 35.9 ± 5.6 with a range of 20.8 to 42.3%, for AXR (p = 0.05). Conclusion: Effective doses showed statistically significant differences between the values calculated from the 1991 and 2007 wƮ values for chest radiography. There is however, insufficient evidence to accept a difference for the abdominal effective doses. Wider studies are required to confirm this result.

New thyroid models for ICRP pediatric mesh-type reference computational phantoms

As part of the ICRP Task Group 103 project, we developed ten thyroid models for the pediatric mesh-type reference computational phantoms (MRCPs). The thyroid is not only a radiosensitive target organ needed for effective dose calculation but an important source region particularly for radioactive iodines. The thyroid models for the pediatric MRCPs were constructed by converting those of the pediatric voxel-type reference computational phantoms (VRCPs) in ICRP Publication 143 to a high-quality mesh format, faithfully maintaining their original topology. At the same time, we improved several anatomical parameters of the thyroid models for the pediatric MRCPs, including the mass, overlying tissue thickness, location, and isthmus dimensions. Absorbed doses to the thyroid for the pediatric MRCPs for photon external exposures were calculated and compared with those of the pediatric VRCPs, finding that the differences between the MRCPs and VRCPs were not significant except for very low energies (<0.03 MeV). Specific absorbed fractions (target ← thyroid) for photon internal exposures were also compared, where significant differences were frequently observed especially for the target organs/tissues close to the thyroid (e.g., a factor of ∼1.2–∼327 for the thymus as a target) due mainly to anatomical improvement of the MRCP thyroid models.

Evaluation of radiation exposure for patients undergoing computed tomography perfusion procedure for acute ischemic stroke

Computed tomography perfusion (CTP) is contrast-enhanced dynamic imaging of the brain utilized to assess the blood flow volume and transmit time to the brain's parenchyma. Stroke is the world's second greatest cause of mortality, accounting for 11% of all deaths, and a major cause of disability. Previous studies reported a high radiation dose per procedure with an eye lens equivalent dose (mGy) ranging from 81.0 mGy to 348.0 mGy. This study's objective is to evaluate patients exposure during CTP procedures. Materials and methods. Three hundred twenty patients with ischemic stroke underwent CTP were examined at King Fahad Medical City (KFMC). The imaging protocol consists of plain CT, CT angiography (CTA), CTP, Angiography. The volume CT Dose Index (CTDIvol, mGy) and dose length product (DLP, mGy.cm) were registered from the PACS system. The effective dose calculation (E, mSv) was extrapolated using computer software. For the CTP procedure, the mean and range of DLP (mGy.cm) for the complete procedure, CT brain, CTA, CTA digital subtraction angiography (DSA), and CTP were 1045 (105–3072), 843 (277–1530), 470.5 (210–1356), 238.8 (105–439), 2712(2012–3072) examinations, respectively. The mean and range of the effective dose (mSv) and CTDIvol (mGy) were 13.2 (10.6–17.1), 80.5 (6.11–256), in that order. The patients' doses showed wide variation due to the selection of multiple phases of acquisition and exposure factors. The dose is higher than most previous studies. Radiation dose optimization is recommended by establishing diagnostic reference level (DRL), proper CT machine setting, and increasing operators' awareness regarding radiation risks.

Organs’ absorbed dose and comparison of different methods for effective dose calculation in computed tomography of parathyroid glands

Objective. To estimate organs’ absorbed dose from the two-phase CT of parathyroid glands, effective dose (ED) based on three different methods, and compare the dose values with those reported by other published protocols. Methods. Volumetric computed tomography dose index (CTDIvol), dose length product (DLP), and the corresponding scan length during each phase of a parathyroid protocol were recorded, for seventy-six patients. One k-factor, and two different k-factors for the neck and chest area were used to estimate the ED from DLP. A Monte Carlo software, VirtualDoseCT, was also used for the estimation of organs’ absorbed dose and ED. Results. Two-phase parathyroid CT resulted in a mean ED of 3.93 mSv, 4.29 mSv and 4.21 mSv according to the one k-factor, two k-factors, and VirtualDoseCT methods, respectively. The two k-factors method resulted in a slight overestimation of 1.9% in total ED compared to VirtualDoseCT. No statistically significant difference was found in ED values between these methods (Wilcoxon test, p > 0.05), except for female patients in the pre-contrast phase. The organs inside the scanning field of view (SFOV) received the following doses: thymus 23.3 mGy, lungs 11.5 mGy, oesophagus 9.2 mGy, thyroid 6.9 mGy, and breast 6.3 mGy. The ED and organs’ dose (OD) values were significantly lower in the pre-contrast than in the arterial phase (Wilcoxon test, p < 0.001). A statistically significant difference was observed between male and female patients for the pre-contrast phase (Mann-Whitney test, p < 0.05), regarding the ED values obtained with the two k-factors method and VirtualDoseCT software. Conclusions. The two k-factors method could be applied for the ED estimation in clinical practice, if appropriate software is not available. An extensive range of ED values derived from the literature, mainly depending on the acquisition protocol parameters and the estimation method.