Estimation Of Effective Dose Research Articles

Re-evaluation of pediatric 18F-FDG dosimetry: Cristy–Eckerman versus UF/NCI hybrid computational phantoms

Because of the concerns associated with radiation exposure at a young age, there is an increased interest in pediatric absorbed dose estimates for imaging agents. Almost all reported pediatric absorbed dose estimates, however, have been determined using adult pharmacokinetic data with radionuclide S values that take into account the anatomical differences between adults and children based upon the older Cristy–Eckerman (C–E) stylized phantoms. In this work, we use pediatric model-derived pharmacokinetics to compare absorbed dose and effective dose estimates for 18F-FDG in pediatric patients using S values generated from two different geometries of computational phantoms. Time-integrated activity coefficients of 18F-FDG in brain, lungs, heart wall, kidneys and liver, retrospectively, calculated from 35 pediatric patients at the Boston’s Children Hospital were used. The absorbed dose calculation was performed in accordance with the Medical Internal Radiation Dose method using S values generated from the University of Florida/National Cancer Institute (UF/NCI) hybrid phantoms, as well as those from C–E stylized computational phantoms. The effective dose was computed using tissue-weighting factors from ICRP Publication 60 and ICRP Publication 103 for the C–E and UF/NCI, respectively. Substantial differences in the absorbed dose estimates between UF/NCI hybrid pediatric phantoms and the C–E stylized phantoms were found for the lungs, ovaries, red bone marrow and urinary bladder wall. Large discrepancies in the calculated dose values were observed in the bone marrow; ranging between −26% to +199%. The effective doses computed by the UF/NCI hybrid phantom S values were slightly different than those seen using the C–E stylized phantoms with percent differences of −0.7%, 2.9% and 2.5% for a newborn, 1 year old and 5 year old, respectively. Differences in anatomical modeling features among computational phantoms used to perform Monte Carlo-based photon and electron transport simulations for 18F, and very likely for other radionuclides, impact internal organ dosimetry computations for pediatric nuclear medicine studies.

P080] Assessment of effective dose in hybrid imaging

Purpose The aim of this study is to assess the typical doses associated with PET/CT examination in a large population and to evaluate the difference of effective dose estimation in fixed vs patient-adapted activity utilizing the same imaging protocols. Doses differences in the urinary bladder are also estimated for PET examination. Methods and materials DoseWatch™ tracking system was utilized to collect patient information and to measure effective dose (for WB 18 F-FDG PET/CT) and organ dose data (for PET only) associated with a fixed activity by retrospectively analyzing existing data. For CT examination DLP values and effective dose data was collected; for PET examination DoseWatch™ provides the administered activity, the effective and the organ doses, based on ICRP 106. Effective and organ dose (for PET only) in a PET/CT examination where the administered activity is adapted to the patient’s weight will be estimated from the same database using a theoretical calculation. The dose in the urinary bladder is also assessed on theoretical calculations. Results Dose data from 6900 CT and 1700 WB 18F-FDG PET were collected. CT mean DLP (mGy*cm) data values were: 1481.3 (76.1–7700.9) and mean effective doses (mSv): 15.2 ± 4.9. Mean administered activities (MBq) and effective doses (mSv) for 18F-FDG PET are: 333.9–6.4. The mean total effective doses (mSv) due to both modality are: 21.5 ± 5.2. equivalent doses (mSv) to urinary bladder are: 43.7 ± 5.8. Conclusions The implementation of a dose tracking system in nuclear medicine is of great value for accurate and regular recording, reporting and analysis of patient’s effective doses.

Indoor Radon Levels and Effective Dose Estimation in Learning and Common Living Space of University

Radon which is natural component of air is a colorless and odorless radioactive gas. Radon exposure can also occur from some building materials if they are made from radon-containing substances by breathing. In this study, The radiation dose of radon concentration was detected at 8 buildings of the A university during 3-month from June. 2017 to August. 2017. We detected indoor radon exposure at 8 building of the university and estimated annual effective dose. The radon concentration of Hall G and Hall F of the A university represented 81 and 14 Bq/㎥ respectively and average indoor radon concentration represented 41.63 Bq/㎥. Average effective dose was estimated 0.40 mSv/y, maximum effective dose was 0.78 mSv/y and minimum effective dose was 0.13 mSv/y respectively. University is the place that students spend the almost whole time. We suggest ventilation and appropriate management of a building, which could reduce the natural radiation exposure by radon concentration.

Estimation of effective radiation dose for households living in rare earth mines in Nam Xe, Lai Chau province

According to the United Nations Scientific Council on the Effects of Atomic Radiation (UNSCEAR), the global average dose level for the community is 2.4mSv/year. People living in the areas with high levels of radiation will cause adverse effects on their health. There are two main components that cause the dose of radiation, mainly due to the inhalation of radon and the extra dose of gamma radiation. The paper presents the results of assessment of natural effective radiation doses on the basis of the projected outpatient dosimetry in 70 households living in Mau and Mo village of Nam Xe, Phong Tho distrist, Lai Chau province.

The effects of dietary probiotics and humic acid on meat quality of Japanese quail including sex-related differences and economical background

The effects of humic substances (HS) on the quality traits (colour, water-holding capacity, and pH), serum minerals (calcium, phosphorus, sodium, potassium, chlorides) and on the serum metabolites (glucose, total protein, triglycerides and cholesterols) of breast and thigh meats of Japanese quails were studied. A total of 60 birds (30 males and 30 females) were involved in the experiment. The animals were fed by the standard basal diet and divided to the 6 groups as follows: probiotic females (PF, n = 10) and probiotic males (PM, n = 10) received probiotic preparation in the single dose of 1 g/1 kg of feed mixture, humic acids females (HF, n = 10) and humic acid males (HM, n = 10) received humic acids in the single dose 3 g/1 kg of feed mixture. The group fed basal diet without any additive served as the control group (CF; n = 10, CM, n = 10). After 210 days the animals were slaughtered, blood samples and samples of muscles (breast and thigh) were collected. Probiotic and humic acids treatment resulted in the significant increase of serum calcium levels in the female groups against the male groups. The content of serum phosphorus significantly increased in the PF group in comparison to the PM group. In this study both treatments (probiotics and humic acids) significantly decreased amount of HDL cholesterol in the female groups in comparison to the female control. Significant sex-based differences were observed for HDL cholesterol (CF, PF, HF vs. CM, PM, HM) and LDL cholesterol (HM vs. HF). 24 h after slaughter meat pH showed significant differences in different muscles. Other investigated parameters of Japanese quails were not influenced by the treatment. We can conclude, that the effect of probiotics and humic acids treatment seems to be dose dependent and estimation of effective dose of additives used in poultry feeding play an important role. Further studies are needed.

Randomized controlled trials define shape of dose response for Pollinex Quattro Birch allergoid immunotherapy

BackgroundThe Birch Allergoid, Tyrosine Adsorbate, Monophosphoryl Lipid A (POLLINEX ® Quattro Plus 1.0 ml Birch 100%) is an effective, well‐tolerated short course subcutaneous immunotherapy. We performed 2 phase II studies to determine its optimal cumulative dose.MethodsThe studies were conducted in Germany, Austria and Poland (EudraCT numbers: 2012‐004336‐28 PQBirch203 and 2015‐000984‐15 PQBirch204) using a wide range of cumulative doses. In both studies, subjects were administered 6 therapy injections weekly outside the pollen season. Conjunctival Provocation Tests were performed at screening, baseline and 3‐4 weeks after completing treatment, to quantify the reduction in Total Symptom Scores (as the primary endpoint) with each cumulative dose. Multiple Comparison Procedure and Modeling analysis was used to test for the dose response, shape of the curve and estimation of the median effective dose (ED 50), a measure of potency.ResultsStatistically significant dose responses (P < .01 & .001) were seen, respectively. The highest cumulative dose in PQBirch204 (27 300 standardized units [SU]) approached a plateau. Potency of the PQBirch was demonstrated by an ED 50 2723 SU, just over half the current dose. Prevalence of treatment‐emergent adverse events was similar for active doses, most being short‐lived and mild. Compliance was over 85% in all groups.ConclusionIncreasing the cumulative dose of PQBirch 5.5‐fold from 5100 to 27 300 SU achieved an absolute point difference from placebo of 1.91, a relative difference 32.3% and an increase in efficacy of 50%, without compromising safety. The cumulative dose response was confirmed to be curvilinear in shape.

Effective dose and radiation risk estimation in certain paediatric renal imaging procedures

Renal imaging (scintigraphy, intravenous urography (IVU) and computed tomography urography (CTU)) are non-invasive procedures that provide information essential in the diagnosis and treatment of renal disorders. The importance of these procedures notwithstanding, radiation exposure to the different tissues and organs could result in diverse reaction possibilities of varying severity. Accordingly, patient dose measurement of such exposures represent an essential step in seeking radiation dose optimization. Present study seeks to quantify effective doses for paediatric patients undergoing renal scintigraphy, IVU and CTU procedures using technetium-99m-diethylene-triamine-pentaacetic acid. Patients population consist of 116 patients (68 boys and 48 girls) were investigated using an Orbiter 37 single-head gamma camera, a digital imaging system and a dual-slice CT detector unit. Patient effective doses were estimated, administered activity ranging between 37.0 and 129.5 MBq per procedure. The mean effective dose and range (in mSv) for renal scintigraphy, CT Urography and IVU procedures were 1.0, 0.98 and 0.6 mSv per procedure respectively. The associated radiation risk estimates per procedure range between 80 and 130 cancers per one million procedures. Patients undergoing renal scintigraphy and CTU procedures received comparable doses such that if CT parameters are optimized this then allows the referring physician to consider the best diagnostic outcome regardless of modality selected.

ESTIMATION OF THE CONVERSION COEFFICIENTS FROM DOSE-AREA PRODUCT TO EFFECTIVE DOSE FOR BARIUM MEAL EXAMINATIONS FOR ADULT PATIENTS

Fluoroscopic examinations of the upper gastro-intestinal tract and, especially, barium meal examinations, are commonly performed in a majority of hospitals. These examinations are associated both with substantial individual patient doses and contribution to the collective dose from medical exposure. Effective dose estimation for this type of examinations is complicated due to: 1) the necessity to simulate the moving X-ray irradiation field; 2) differences in study structure for the individual patients; 3) subjectivity of the operators; and 4) differences in the X-ray equipment. The aim of the current study was to estimate conversion coefficients from dose-area product to effective dose for barium meal examinations for the over couch and under couch exposure conditions. The study was based on data collected in the X-ray unit of the surgical department of the St-Petersburg Mariinsky hospital. A model of patient exposure during barium meal examination was developed based on the collected data on fluoroscopy protocols and adult patient irradiation geometry. Conversion coefficients were calculated using PCXMC 2.0 software. Complete examinations were converted into a set of typical fluoroscopy phases and X-ray images, specified by the examined anatomical region and the projection of patient exposure. Conversion coefficients from dose-area product to effective dose were calculated for each phase of the examination and for the complete examination. The resulting values of the conversion coefficients are comparable with published data. Variations in the absolute values of the conversion coefficients can be explained by differences in clinical protocols, models for the estimation of the effective dose and parameters of barium meal examinations. The proposed approach for estimation of effective dose considers such important features of fluoroscopic examinations as: 1) non-uniform structure of examination, 2) significant movement of the X-ray tube within a single fluoroscopic phase, and 3) the variety of exposure geometries within complete examination.

Radon 222 in drinking water resources of Iran: A systematic review, meta-analysis and probabilistic risk assessment (Monte Carlo simulation)

The current study was performed to review the conducted studies regarding the concentration of radon 222 in the tap drinking water; furthermore, by estimation of ingestion and inhalation effective dose, the health risk assessment in the adults and children using MCS technique was assessed. All related studies published among January 1990 to October 2016; were screened in the available databases such as Web of Science, PubMed, Science Direct, Scopus, SID, and Irandoc. The total effective dose was estimated by calculating Eing (Effective dose of ingestion) and Einh (Effective dose of inhalation) by Monte Carlo simulation (MCS) method. The range of ND ─ 40.9 Bq/L for radon 222 in water resources was proposed after evaluation of data collected from 13 studies with 1079 samples. The overall concentration of radon 222 in drinking water in Iran was 3.98: 95%CI (3.79 ─ 4.17 Bq/L). Also, the effective ingestion dose of radon 222 in adults age groups was 1.35 times higher than children. The rank order of drinking water resources based on the concentration of radon 222 was Spring > Spring and Well > Well > Spring and Qanat > Tap water. The overall concentration of radon 222 in drinking water in Iran was lower than WHO and EPA standard limits. Also, the rank order regarding area studied based on the concentration of radon 222 was Gillan > Mashhad > Mazandaran > Kerman > Yazd > Tehran > Kermanshah > Golestan > Hormozgan. The effective ingestion dose of radon 222 to consumers in the Gillan, Mashhad, Mazandaran, and Kerman were higher than WHO guidance (0.1 mSv/y). Also except consumers in the Hormozgan, inhalation effective dose radon 222, in the other investigated areas were higher than WHO guidance (0.1 mSv/y). Therefore, it is recommended to conduct the required programs regarding control and elimination of radon 222 concentration in Iranian drinking water supply.

Radiation Dose Exposure for Lumbar Transforaminal Epidural Steroid Injections and Facet Joint Blocks Under CT vs. Fluoroscopic Guidance.

Transforaminal epidural steroid injections (TFESIs) and facet joint blocks can be performed under fluoroscopy or computed tomography (CT) guidance. The purpose of this retrospective cohort study was to compare patient radiation dose for lumbar TFESIs and facet joint blocks under CT guidance vs. fluoroscopic guidance. The primary outcome of this retrospective cohort study was the difference between the estimated effective dose (ED) of CT guidance and fluoroscopic guidance for TFESIs and facet joint blocks. Patients who had undergone these procedures with both CT and fluoroscopic guidance were eligible for this study. Dose-length product for CT-guided procedures and dose-area product for fluoroscopic-guided procedures were retrospectively collected and converted to ED. Within- or between-group comparisons were performed with appropriate nonparametric tests, using a P value of < 0.05 to indicate statistical significance. The 42 patients included in this study underwent a total of 100 procedures. The median estimated ED differed significantly between CT-guided injections and fluoroscopic-guided injections (1.59 mSv (interquartile range [IQR] 0.78 to 3.09) vs. 0.19 mSv (IQR 0.11 to 0.30) (Wilcoxon signed rank test, P < 0.001). The study results suggest that TFESIs and facet joint blocks performed with CT guidance are associated with more than 8 times higher patient radiation dose exposure compared to fluoroscopic guidance. There needs to be more vigilance with regards to CT guidance in interventional pain procedures.

Subgroup identification in dose-finding trials via model-based recursive partitioning.

An important task in early-phase drug development is to identify patients, which respond better or worse to an experimental treatment. While a variety of different subgroup identification methods have been developed for the situation of randomized clinical trials that study an experimental treatment and control, much less work has been done in the situation when patients are randomized to different dose groups. In this article, we propose new strategies to perform subgroup analyses in dose-finding trials and discuss the challenges, which arise in this new setting. We consider model-based recursive partitioning, which has recently been applied to subgroup identification in 2-arm trials, as a promising method to tackle these challenges and assess its viability using a real trial example and simulations. Our results show that model-based recursive partitioning can be used to identify subgroups of patients with different dose-response curves and improves estimation of treatment effects and minimum effective doses compared to models ignoring possible subgroups, when heterogeneity among patients is present.

Evaluation of coefficients to derive organ and effective doses from cone-beam CT (CBCT) scans: a Monte Carlo study

Regular imaging is used throughout image guided radiation therapy to improve treatment delivery. In order for treatment procedures to be optimized, the doses delivered by imaging exposures should be taken into account. CT dosimetry methods based on the CT dose index (CTDI), measured with a 100 mm long pencil ionization chamber (CTDI100) in standard phantoms, are not designed for cone-beam CT (CBCT) imaging systems used in radiotherapy, therefore a modified version has been proposed for CBCT by the International Electrotechnical Commission (CTDIIEC). Monte Carlo simulations based on a Varian On-Board Imaging system were used to derive conversion coefficients that enable organ doses for ICRP reference phantoms to be determined from the CTDIIEC for different scan protocols and different beam widths (80–320) mm. A dose–width product calculated by multiplying the CTDIIEC by the width of the CBCT beam is proposed as a quantity that can be used for estimating effective dose. The variation in coefficients with CBCT beam width was studied. Coefficients to allow estimation of effective doses were derived, namely 0.0034 mSv (mGy cm)−1 for the head, 0.0252 mSv (mGy cm)−1 for the thorax, 0.0216 mSv (mGy cm)−1 for the abdomen and 0.0150 mSv (mGy cm)−1 for the pelvis, and these may be applicable more generally to other CBCT systems in radiotherapy. If data on effective doses are available, these can be used in making judgements on the contributions to patient dose from imaging, and thereby assist in optimization of the treatment regimes. The coefficients can also be employed in converting dosimetry data recorded in patient records into quantities relating directly to patient doses.

Virtual Computed Tomography Colonography: Evaluation of 2D and Virtual 3D Image Quality of Sub-mSv Examinations Enabled by Third-generation Dual Source Scanner Featuring Tin Filtering

To evaluate two- and three-dimensional (2D and 3D) image quality of sub-milliSievert (mSv) computed tomography (CT) colonography utilizing a third-generation dual source CT scanner featuring a tin filter. We retrospectively evaluated 26 consecutive patients who underwent third-generation dual source CT colonography, nine with the standard-dose clinical-scan protocol (SDP) and 17 with a low-dose protocol (LDP) featuring a tin filter. Radiation dose was evaluated by volume computed tomography dose index (CTDIvol), dose length product (DLP), effective dose (E), and size-specific dose estimate. Objective image quality was evaluated utilizing signal-to-noise ratio (SNR) derived from standardized placed regions of interest on the transverse 2D images and the ratio of SNR/CTDIvol (normalized SNR). Two radiologists in consensus assessed subjective image quality of the virtual 3D images. There were no significant differences in subjective image quality (P = .661). All examinations were rated "excellent" or "good" for diagnostic confidence. The mean total for DLP/E was 143.4 ± 29.8 mGy/3.00 ± 0.40 mSv in the SDP and therefore significantly higher than in the LDP with 36.9 ± 8.7 mGy/0.75 ± 0.16 mSv (P < .001). The SNR was 8.9 ± 2.1 in the SDP and 4.9 ± 0.8 in the LDP. Third-generation dual source CT featuring a tin filter enables consistent sub-mSv colonography without substantially impairing image quality.

Value of whole-body low-dose computed tomography in patients with ventriculoperitoneal shunts: a retrospective study.

OBJECTIVEThe gold standard for evaluation of ventriculoperitoneal (VP) shunt position, dislocation, or disconnection is conventional radiography. Yet, assessment with this modality can be challenging because of low image quality and can result in repetitive radiation exposure with high fluctuation in the radiation dose. Recently, CT-based radiation doses have been significantly reduced by using low-dose protocols. Thus, whole-body low-dose CT (LDCT) has become applicable for routine use in VP shunt evaluation. The authors here compared image quality and approximate radiation dose between radiography and LDCT in patients with implanted VP shunt systems.METHODSVentriculoperitoneal shunt systems have been investigated with LDCT scanning at the authors' department since 2015. A consecutive series of 57 patients (70 investigations) treated between 2015 and 2016 was retrospectively assessed. A historical patient cohort that had been evaluated with radiography was compared with the LDCT patients in terms of radiation dose and image quality. Three independent observers evaluated projection of the valve pressure level and correct intraperitoneal position, as well as complete shunt projection, using a Likert-type scale of 1-5, where 1 indicated "not assessable" and 5 meant "assessable with high accuracy." Descriptive statistics and the Mann-Whitney U-test were used for analysis.RESULTSTwenty-seven radiographs (38.6%) and 43 LDCT scans (61.4%) were analyzed. The median dose-length product (DLP) of the LDCT scans was 100 mGy·cm (range 59.9-183 mGy·cm). The median total dose-area product (DAP) of the radiographic images was 3177 mGy·cm2 (range 641-13,833 mGy·cm2). The estimated effective dose (EED) was significantly lower with the LDCT scan (p < 0.001). The median EED was 4.93 and 1.90 mSv for radiographs and LDCT, respectively. Significantly better identification of the abdominal position of the distal shunt catheter was achieved with LDCT (p < 0.001). Simultaneously, significantly improved visualization of the entire shunt system was realized with this technique (p < 0.001). On the contrary, identification of the valve settings was significantly worse with LDCT (p < 0.001).CONCLUSIONSWhole-body LDCT scanning allows good visualization of the distal catheter after VP shunt placement. Despite the fact that only a rough estimation of effective doses is possible in a direct comparison of LDCT and radiography, the data showed that shunt assessment via LDCT does not lead to greater radiation exposure. Thus, especially in difficult anatomical conditions, as in patients who have undergone multiple intraabdominal surgeries, have a high BMI, or are immobile, the use of LDCT shunt evaluation has high clinical value. Further data are needed to determine the value of LDCT for the evaluation of complications or radiation dose in pediatric patients.

Activity concentration and annual effective dose estimation of 210Pb, 40K and 137Cs in surface soil samples from southern Algeria

Activity concentration and annual effective dose estimation of 210Pb, 40K and 137Cs in surface soil samples from southern Algeria

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.

Estimation of the effective dose of dental cone-beam computed tomography using personal computer-based Monte Carlo software.

PurposeTo calculate the effective doses of cone-beam computed tomography (CBCT) using personal computer-based Monte Carlo (PCXMC) software (Radiation and Nuclear Safety Authority, Helsinki, Finland) and to compare the calculated effective doses with those measured using thermoluminescent dosimeters (TLDs) and an anthropomorphic phantom.Materials and MethodsAn Alphard VEGA CBCT scanner (Asahi Roentgen Ind. Co., Kyoto, Japan) with multiple fields of view (FOVs) was used for this study. The effective doses of the scout and main projections of CBCT using 1 large and 2 medium FOVs with a height >10 cm were calculated using PCXMC and PCXMCRotation software and then were compared with the doses obtained using TLD-100 LiF and an anthropomorphic adult human male phantom. Furthermore, it was described how to determine the reference points on the Y- and Z-axes in PCXMC, the important dose-determining factors in this software.ResultsThe effective doses at CBCT for 1 large (20.0 cm×17.9 cm) and 2 medium FOVs (15.4 cm×15.4 cm and 10.2 cm×10.2 cm) calculated by the PCXMC software were 181, 300, and 158 µSv, respectively. These values were comparable (16%–18% smaller) to those obtained through TLD measurements in each mode.ConclusionThe use of PCXMC software could be an alternative to the TLD measurement method for effective dose estimation in CBCT with large and medium FOVs.

210Po Radioactivity in Tobacco and Smoke Inhalation Effective Dose Estimation

In this study, 210 Po radioactivity in tobacco and effective dose estimation from smoke inhalation were investigated. 14 most frequently used cigarette brands in Turkey were used for this purpose. 210 Po average radioactivity in tobacco was found to be 25.4 ± 2.0 Bq/kg. 210 Po mean annual effective dose was found to be 181.8 µSv/y.

Patient-specific organ and effective dose estimates in pediatric oncology computed tomography

PurposeEstimate organ and effective doses from computed tomography scans of pediatric oncologic patients using patient-specific information. Materials and MethodsWith IRB approval patient-specific scan parameters and patient size obtained from DICOM images and vendor-provided dose monitoring application were obtained for a cross-sectional study of 1250 pediatric patients from 0 through 20 y-olds who underwent head, chest, abdomen-pelvis, or chest-abdomen-pelvis CT scans. Patients were categorized by age. Organ doses and effective doses were estimated using VirtualDose™ CT based on patient-specific information, tube current modulation (TCM), and age-specific realistic phantoms. CTDIvol, DLP, and dose results were compared with those reported in the literature. ResultsCTDIvol and DLP varied widely as patient size varied. The 75th percentiles of CTDIvol and DLP were no greater than in the literature with the exception of head scans of 16–20 y-olds and of abdomen-pelvis scans of larger patients. Eye lens dose from a head scan was up to 69 mGy. Mean organ doses agreed with other studies at maximal difference of 38% for chest and 41% for abdomen-pelvis scans. Mean effective dose was generally higher for older patients. The highest effective doses were estimated for the 16–20 y-olds as: head 3.3 mSv, chest 4.1 mSv, abdomen-pelvis 10.0 mSv, chest-abdomen-pelvis 14.0 mSv. ConclusionPatient-specific organ and effective doses have been estimated for pediatric oncologic patients from <1 through 20 y-olds. The effect of TCM was successfully accounted for in the estimates. Output parameters varied with patient size. CTDIvol and DLP results are useful for future protocol optimization.

Comparison of Radiation Dose and Image Quality of Abdominopelvic CT Using Iterative (AIDR 3D) and Conventional Reconstructions

The purpose of this study is to compare radiation dose and image quality of abdominopelvic CT studies reconstructed with iterative and conventional techniques. This retrospective study enrolled 99 patients who underwent abdominopelvic CT examinations with the portal venous phase images reconstructed with both filtered back projection and Adaptive Iterative Dose Reduction 3D (AIDR 3D) at different time points. Subjective assessment of image quality was performed by two radiologists who scored axial images for overall quality, sharpness, noise, and acceptability in a blinded fashion. The SD of the mean attenuation of the liver, aorta, and paraspinal muscle (as a measurement of image noise) and contrast-to-noise and signal-to-noise ratios for liver and aorta were used as objective parameters of image quality. Radiation dose parameters included CT dose index volume (CTDIvol), dose-length product, effective dose (ED), and size-specific dose estimate (SSDE). Results were compared for different body mass index (BMI; weight in kilograms divided by the square of height in meters) categories. Paired t test and McNemar paired tests for noninferiority were used, with p < 0.05 considered statistically significant. We obtained a 62.5% mean reduction in CTDIvol, a 58% mean reduction in ED, and a 63% mean reduction in SSDE when AIDR 3D was used (p < 0.001). Subjective parameters of image quality were considered noninferior for AIDR 3D studies compared with filtered back projection (p < 0.001), except for the sharpness of images of patients with BMI 20-24.9. Variable results were found regarding objective assessment of image quality. AIDR 3D allowed a significant reduction in radiation dose of abdominopelvic CT examinations without a loss of image quality in general.