Reported Radiation Dose Research Articles

Zero-fluoroscopy ablation with multielectrode pulse field ablation system: Case series.

Pulse field ablation (PFA) is a novel nonthermal ablation modality for treatment of atrial fibrillation. While mostly lacking 3D electroanatomical mapping integration, reported radiation doses in procedures using multielectrode PFA catheters are relatively high. We report a first case series of three patients where a zero-fluoroscopy approach by intracardiac echocardiography was utilized and present a possible workflow for zero-fluoroscopy ablation with the Farapulse PFA system.

Linear relationship between absorbed radiation dose and pulse rate during fluoroscopy.

To identify the relationship between fluoroscopy pulse rate and absorbed radiation dose. We compared absorbed radiation dose with common proxy measurements such as fluoroscopy time and C-arm reported dose. Using a simulated patient model, 60s fluoroscopy exposures were performed using pulse rates of 30, 8, 4, 2, and 1 pulse(s) per second. Each experiment was performed with both standard and low-dose settings using a GE OEC 9800 plus C-arm. Landauer nanoDot™ OSL dosimeters were used to measure the absorbed radiation dose. Fluoroscopy pulse rate and absorbed radiation dose demonstrated a linear correlation for both standard (R2 = 0.995, p < 0.001) and low-dose (R2 = 0.998, p < 0.001) settings. For any given pulse rate, using the low-dose setting reduced absorbed radiation dose by 58 ± 2.8%. Fluoroscopy time demonstrated a linear relationship with absorbed radiation dose for both standard (R2 = 0.996, p < 0.001) and low-dose (R2 = 0.991, p < 0.001) settings, but did not change with use of the low-dose setting. C-arm reported radiation dose correlated linearly with absorbed dose (R2 = 0.999) but consistently under-estimated measured values by an average of 49 ± 3.5%. Using a combination of 1 pulse-per-second and low-dose fluoroscopy, absorbed dose was reduced by 97.7 ± 0.1% compared to standard dose and 30 pulse-per-second settings. Absorbed radiation dose decreases linearly with fluoroscopy pulse rate during equivalent exposure times. Adjusting fluoroscopy pulse rate and utilizing low-dose settings significantly reduces overall absorbed radiation exposure by up to 98%.

Effectiveness of ultrasound-guided percutaneous transhepatic biliary drainage to reduce radiation exposure: A single-center experience.

Percutaneous transhepatic biliary drainage (PTBD) has been an effective treatment to access the biliary tree, especially in case of endoscopically inaccessible biliary tree. In general, PTBD techniques are divided into two methods: fluoroscopy-guided PTBD and ultrasound (US)-guided PTBD. This study aimed to evaluate the effectiveness of US-guided PTBD, focusing on radiation exposure according to intrahepatic duct (IHD) dilatation degree, differences between right- and left-sided approaches and differences between benign and malignant biliary stenosis/obstruction. We evaluated technical success, clinical success, procedural data (the number of liver capsule punctures, procedural time, fluoroscopy time and radiation dose), and procedure-related complications. During the study period, a total of 123 patients with biliary stenosis/obstruction or bile leakage were initially eligible. We excluded 76 patients treated with only ERCP or initially treated with ERCP followed underwent PTBD insertion. Finally, a total of 50 procedures were performed in 47 patients. Of the 47 patients, 8 patients had anatomical alteration due to previous surgery, 6 patients refused ERCP, and 3 patients failed ERCP. For the remaining 30 patients, PTBD was performed on weekend or at night, 11 of whom had poor general condition, 10 patients underwent ERCP 3 to 4 days later after PTBD insertion, 6 patients improved after PTBD insertion without ERCP, 1 patient died, and 1 patient was referred to other hospital. Remaining 1 patient underwent surgery due to Mirizzi syndrome. All procedures were performed by two interventional radiologists. Technical success rate was 100%, clinical success was 94%, and the complication rate was 10%. Fluoroscopy time and the reported radiation dose were significantly lower in patients with dilated bile ducts than in those with non-dilated bile ducts, when biliary puncture under US guidance was performed initially. However, even in patients with non-dilated bile ducts undergoing initial trials of biliary puncture under US guidance, the fluoroscopy time and the reported radiation dose were low, based on current studies. No statistical significant differences were observed in terms of technical and dosimetry results according to right-sided and left-sided procedures and benign and malignant biliary stenosis/obstruction. Thus, US-guided PTBD was found to be a safe and effective technique that significantly reduced fluoroscopy time and radiation doses.

Radiation Exposure in Pediatric Interventional Procedures.

The article is part of the series of articles on radiation protection. You can find further articles in the special section of the CVIR issue. The expanding applications of interventional procedures coupled with the potential harmful effects of ionizing radiation highlight the need to assess the delivered radiation dose and establish an effective radiation protection program, particularly in the radiosensitive pediatric population. Given the complexity and heterogeneity of interventional procedures as well as the unique characteristics of children, the management of radiation dose is proving to be quite challenging. The aim of the current article is to provide an overview of the radiation exposure in pediatric patients during interventional procedures focusing on the importance of radiation protection in the pediatric population, the reported radiation doses and the techniques of minimizing radiation dose.

Radiation Safety in Videofluoroscopic Swallowing Study: Systematic Review.

Videofluoroscopic swallowing study (VFSS) is generally used to diagnose dysphagia and oropharyngeal aspiration during swallowing movement. Patients and bolus-feeding operators (such as occupational therapist and speech language pathologist) may undergo multiple VFSS procedure, placing them at risk for more radiation exposure due to increased scan time. The present study investigated the dose-area product, effective dose of various protocols, and summarized dose reports from various studies of VFSS. The PubMed database searched for relevant publications reporting radiation dose in the VFSS procedure. 13 articles were selected to be reviewed. This systematic review involved 13 peer-reviewed articles that reported the specific dose of the VFSS procedure. The articles were categorized into three types: operator radiation dose, adult patient radiation dose, and pediatric radiation dose. The operator dose reports showed that the operators' scattering exposure, equivalent dose (across the whole body, eyes, and hands), and annual effective dose were significantly lower than the annual dose limit of 20mSv. Both adult and pediatric patient dose reports showed that the effective dose, which was estimated from recorded dose-area product, was significantly lower than the annual background exposure of 2.4mSv in various protocols. The present literature review suggested that the radiation dose of VFSS by modified barium swallowing is acceptable in both operators and patients. However, various radiation protection strategies should be conducted during the procedure to reduce the risk of stochastic effect.

Safety and effectiveness of ultrasound-guided percutaneous transhepatic biliary drainage: a multicenter experience.

Aim of this study is to describe a multicenter experience on percutaneous transhepatic biliary drainage (PTBD) performed with ultrasound-guidance to access the biliary tree, focusing on safety, effectiveness and radiation dose exposure; differences between right- and left-sided approaches have been also evaluated. This is a multicenter prospective single-arm observational study conducted on patients affected by biliary tree stenosis/occlusion with jaundice and endoscopically inaccessible. The procedures have been performed puncturing the biliary system under US guidance and crossing the stenosis/occlusion under fluoroscopy. Beam-on time and X-ray dose have been evaluated. 117 patients affected by biliary tree stenosis/occlusion not manageable with an endoscopic approach have been included in this analysis. The biliary stenosis/occlusion was malignant in 90.8% and benign in 9.2%. Technical success, considered as positioning of a drainage tube into the biliary tree, was 100%. Overall clinical success, considered as decrease in total bilirubin level after a single procedure, was 95.7%. The overall mean number of liver punctures to catheterize the biliary tree was 1.57. The mean total beam-on time was 570.4s; the mean dose-area product was 37.25Gycm2. No statistical significant differences were observed in terms of technical and dosimetry results according to right-sided and left-sided procedures. Complications rate recorded up to 30days follow-up was 10.8%, all of minor grades. In this series US guidance to access the biliary tree for PTBD was a safe and effective technique with an acceptable low-grade complications rate; the reported radiation dose is low.

Effects of Seasonal Change on the Levels of Geogenic Radionuclides in Sand and Rocks from Tyaa River deposit in Kitui County

The average activity concentration of 226Ra, 232Th and 40K in rock samples during the rainy season was 22±1.1 BqKg-1, 46±2.3 BqKg-1, and 659±33 BqKg-1 respectively, while in the sand was 27±1.4 BqKg-1, 49±2.5 BqKg-1and 824±41 BqKg-1 for 226Ra, 232Th and 40K respectively. A repeat study during dry season reported higher activities for 226Ra, 232Th, and 40K for most samples. The corresponding dose rates and radiological indices estimated from specific activities of 226Ra, 232Th and 40K showed an upward trend as seasons changed from rainy to dry. Both seasons reported radiation doses below the permissible limits.

Gray detector, a dose monitoring software for radiology departments

The aim of this work is to present the gray detector, a web-based patient radiation dose monitoring software developed to answer on health protection of individuals against the dangers of ionizing radiation in relation to medical exposure, (Council Directive 2013/59/Euratom) This software provides to capture, track and report radiation dose directly from any imaging device or PACS, completely vendor neutral solution, and it is the simple yet scalable way to document dose, set reference levels, benchmark performance, manage protocols and identify outliers. The solution gives the possibility to integrate all the information about the dose with the data in RIS: in this way there is the possibility to context the dosimetric data and to follow the optimization of the radiologic risk management and the ratio risk/benefit of the image. Gray detector manages all diagnostic modality tracking and archiving all dosimetry data: CT, Mammography, Interventional, Cardiovascular, Radiography and Nuclear Medicine. It is compatible with DICOM SR and DICOM MPPS messages, Query & Retrieve DICOM image header (for non MSSP/SR DICOM modality), to extract all relevant information from dose and maximize data collection, crossing the fundamental data stored in the RIS database. All data collected can be viewed through customizable charts or exported according to standard formats gray detector has an “alert system”, that gives the possibility to send email and display messages when the modality gives an over dose, based on DRL The integration of the gray detector with information systems, may improve clinical quality performance in diagnostic imaging The aim of this work is to present the gray detector, a web-based patient radiation dose monitoring software developed to answer on health protection of individuals against the dangers of ionizing radiation in relation to medical exposure, (Council Directive 2013/59/Euratom) This software provides to capture, track and report radiation dose directly from any imaging device or PACS, completely vendor neutral solution, and it is the simple yet scalable way to document dose, set reference levels, benchmark performance, manage protocols and identify outliers. The solution gives the possibility to integrate all the information about the dose with the data in RIS: in this way there is the possibility to context the dosimetric data and to follow the optimization of the radiologic risk management and the ratio risk/benefit of the image. Gray detector manages all diagnostic modality tracking and archiving all dosimetry data: CT, Mammography, Interventional, Cardiovascular, Radiography and Nuclear Medicine. It is compatible with DICOM SR and DICOM MPPS messages, Query & Retrieve DICOM image header (for non MSSP/SR DICOM modality), to extract all relevant information from dose and maximize data collection, crossing the fundamental data stored in the RIS database. All data collected can be viewed through customizable charts or exported according to standard formats gray detector has an “alert system”, that gives the possibility to send email and display messages when the modality gives an over dose, based on DRL The integration of the gray detector with information systems, may improve clinical quality performance in diagnostic imaging

SU‐G‐IeP3‐12: Preliminary Report On the Experience of Patient Radiation Dose Monitoring and Tracking Systems; PEMNET, Radimetrics and DoseWatch

Purpose:Three patient radiation dose monitoring and tracking (PRDMT) systems have been in operation at this institution for the past 6 months. There are useful information that should be disseminated to those who are considering installation of PRDMT programs. In addition, there are “problems” uncovered in the process of estimating fluoroscopic “peak” skin dose (PSD), especially, for those patients who received interventional angiographic studies and in conjunction with surgical procedures.Methods:Upon exporting the PRDMT data to Microsoft Excel program, the peak skin dose can be estimated by applying various correction factors including; attenuation due to the tabletop and examination mattress, table height, tabletop translation, backscatter, etc. A procedure was established to screen and divide the PRDMT reported radiation dose and estimated PSD to three different levels of threshold to assess the potential skin injuries, to assist patient follow‐up, risk management and provide radiation dosimetry information in case of “Sentinel Event”.Results:The Radiation Dose Structured Report (RDSR) was found to be the prerequisite for the PRDMT systems to work seamlessly. And, the geometrical parameters (gantry and table orientation) displayed by the equipment are not necessarily implemented in the “patient centric” manner which could result in a large error in the PSD estimation. Since, the PRDMT systems obtain their pertinent data from the DICOM tags including the polarity (+ and − signs), the geometrical parameters need to be verified.Conclusion:PRDMT systems provide a more accurate PSD estimation than previously possible as the air‐kerma‐area dose meter become widely implemented. However, care should be exercised to correctly apply the geometrical parameters in estimating the patient dose. In addition, further refinement is necessary for these software programs to account for all geometrical parameters such as the tabletop translation in the z‐direction in particular.

Radiation dose in pneumatic reduction of ileo-colic intussusceptions--results from a single-institution study.

Air enema under fluoroscopy is a well-accepted procedure for the treatment of childhood intussusception. However, the reported radiation doses of pneumatic reduction with conventional fluoroscopy units have been high in decades past. To compare current radiation doses at our institution to past doses reported by others for fluoroscopic-guided pneumatic reduction of ileo-colic intussusception in children. Since 2007 radiologists and residents in our department who perform reduction of intussusceptions have received a radiation risk training. We retrospectively analyzed the data of 45 children (5 months-8 years) who underwent a total of 48 pneumatic reductions of ileo-colic intussusception between 2008 and 2012. We analyzed data for screening time and dose area product (DAP) and compared these data to those reported up to and including the year 2000. Our mean screening time measured by the DAP-meter was 53.8 s (range 1-320 s, median 33.0 s). The mean DAP was 11.4 cGy ∙ cm(2) (range 1-145 cGy ∙ cm(2), median 5.45 cGy ∙ cm(2)). There was one bowel perforation, in a 1-year-old boy requiring surgical revision. Only three studies in the literature presented radiation exposure results on children who received pneumatic or hydrostatic reduction of intussusception under fluoroscopy. Screening times and dose area products in those studies, which were published in the 1990 s and in the year 2000, were substantially higher than those in our sample. Low-frequency pulsed fluoroscopy and other dose-saving keys as well as the radiation risk training might have helped to improve the quality of the procedure in terms of radiation exposure.

'Fukusensor:' a genetically engineered plant for reporting DNA damage in response to gamma radiation.

Transgenic plants can be designed to be 'phytosensors' for detection of environmental contaminants and pathogens. In this study, we describe the design and testing of a radiation phytosensor in the form of green fluorescence protein (GFP)-transgenic Arabidopsis plant utilizing a DNA repair deficiency mutant background as a host. Mutant lines of Arabidopsis AtATM (At3g48190), which are hypersensitive to gamma irradiation, were used to generate stable GFP transgenic plants in which a gfp gene was under the control of a strong constitutive CaMV 35S promoter. Mutant and nonmutant genetic background transgenic plants were treated with 0, 1, 5, 10 and 100Gy radiation doses, respectively, using a Co-60 source. After 1week, the GFP expression levels were drastically reduced in young leaves of mutant background plants (treated by 10 and 100Gy), whereas there were scant visible differences in the fluorescence of the nonmutant background plants. These early results indicate that transgenic plants could serve in a relevant sensor system to report radiation dose and the biological effects to organisms in response to radionuclide contamination.

Standardizing radiation dose reporting in the pediatric cardiac catheterization laboratory—A multicenter study by the CCISC (Congenital Cardiovascular Interventional Study Consortium)

We examine normalized air Kerma area product (PKA ) by body weight (PKA /BW) as a reference value of radiation dose and benchmark PKA /BW in pediatric laboratories using a multicenter registry database. Reduction of radiation dose is an important quality improvement task in pediatric cardiac catheterization laboratories. Physicians need to agree on a standard method of reporting radiation dose that would allow comparisons to be made between operators and institutions. This was a multicenter observational study of radiation dose in pediatric laboratories. Patient demographic, procedural and radiation data including fluoroscopic time and PKA (µGy m(2) ) were analyzed. PKA /BW was obtained by indexing PKA to body weight. A total of 8,267 pediatric catheterization procedures (age <18 years) were included from 16 institutions. The procedures consisted of diagnostic (n = 2,827), transplant right ventricular (RV) biopsy (n = 1,172), and interventional catheterizations (n = 4268). PKA correlated with body weight better than with age and best correlated with weight-fluoroscopic time product. PKA /BW showed consistent values across pediatric ages. Interventional catheterizations had the highest PKA /BW (50th, 75th, and 90th percentiles: 72, 151, and 281 μGy m(2) /kg), followed by diagnostic (59, 105, and 175 μGy m(2) /kg) and transplant RV biopsy (27, 79, and 114 μGy m(2) /kg). PKA /BW appeared to be the most reliable standard to report radiation dose across all procedure types and patient age. We recommend PKA /BW to be used as the standard unit in documenting radiation usage in pediatric laboratories and can be used to evaluate strategies to lower radiation dosage in pediatric patients undergoing cardiac catheterizations. © 2014 Wiley Periodicals, Inc.

Estimation of Radiation Doses in X-Ray Visualization of Biological Objects

Two setups for X-ray visualization of objects interior structure were designed and assembled in TPU. These radiographic systems are based on linear gas-discharge and GaAs semiconductor detectors. During investigation of biological object control of radiation doses has a high priority. In this report radiation dose calculations in X-ray visualization are presented. These calculation also includes dose calculations of sinograms which are used for reconstruction of tomography slices.

Aftershocks Associated With Impaired Health Caused by the Great East Japan Disaster Among Youth Across Japan: A National Cross-Sectional Survey

BackgroundThe Great East Japan earthquake, subsequent tsunamis and the Fukushima nuclear incident had a tremendous impact on Japanese society. Although small-scale surveys have been conducted in highly affected areas, few have elucidated the disaster’s effect on health from national perspective, which is necessary to prepare national policy and response.ObjectiveThe aim of the present study was to describe prefecture-level health status and investigate associations with number of aftershocks, seismic intensity, a closer geographical location to the Fukushima Nuclear Power Plant, or higher reported radiation dose in each prefecture even after adjusting for individual socioeconomic factors, by utilizing individual-level data acquired from a national cross-sectional Internet survey as well as officially reported prefecture-level data.MethodsA Japanese government research institute obtained 12,000 participants by quota sampling and 7335 participants were eligible for the analysis in an age range between 17 and 27 years old. We calculated the percentage of people with decreased subjective health in each prefecture after the earthquake. Variability introduced by a small sample size for some prefectures was smoothed using empirical Bayes estimation with a random-intercept logistic model, with and without demographic factors. Multilevel logistic regression was used to calculate adjusted odds ratios (ORs) for change of subjective health associated with prefecture-level and individual-level factors.ResultsAdjusted empirical Bayes estimates were higher for respondents commuting in the northeast region (Iwate 14%, Miyagi 19%, and Fukushima 28%), which faces the Pacific Ocean, while the values for Akita (10%) and Yamagata (8%) prefectures, which do not face the Pacific Ocean, were lower than those of Tokyo (12%). The values from the central to the western region were clearly lower. The number of aftershocks was coherently associated with decreased health (OR 1.05 per 100 times, 95% CI 1.04-1.06; P<.001) even after adjusting for covariates (OR 1.02 per 100 times, 95% CI 1.00-1.05; 1.32 per 1000 times, 95% CI 1.03-1.71; P=.049). In contrast, seismic intensity of the initial earthquake (OR 0.87, 95% CI 0.65-1.17; P=.36), radiation dose (OR 1.16, 95% CI 0.82-1.64; P=.41), and distance from the Fukushima Nuclear Power Plant (OR 1.00, 95% CI 0.99-1.00; P=.66) were not. Change in job condition (OR 2.05, 95% CI 1.72-2.45; P<.001), female (OR 1.43, 95% CI 1.19-1.69; P<.001), higher age (OR 1.06 per year, 95% CI 1.02-1.11; P=.005), and duration of evacuation longer than 4 weeks (OR 1.44, 95% CI 1.06-1.97; P=.02) seemed to decrease perceived health status.ConclusionsWe found nationwide differences that show decreased health status because of the Great East Japan disaster according to prefecture. The number of aftershocks, change in work conditions, being female, a higher age, and duration of the evacuation were risk factors for the population after the major earthquake, tsunamis, and nuclear incident.

Proton flux and radiation dose from galactic cosmic rays in the lunar regolith and implications for organic synthesis at the poles of the Moon and Mercury

Galactic cosmic rays are a potential energy source to stimulate organic synthesis from simple ices. The recent detection of organic molecules at the polar regions of the Moon by LCROSS (Colaprete, A. et al. [2010]. Science 330, 463–468, http://dx.doi.org/10.1126/science.1186986), and possibly at the poles of Mercury (Paige, D.A. et al. [2013]. Science 339, 300–303, http://dx.doi.org/10.1126/science.1231106), introduces the question of whether the organics were delivered by impact or formed in situ. Laboratory experiments show that high energy particles can cause organic production from simple ices. We use a Monte Carlo particle scattering code (MCNPX) to model and report the flux of GCR protons at the surface of the Moon and report radiation dose rates and absorbed doses at the Moon’s surface and with depth as a result of GCR protons and secondary particles, and apply scaling factors to account for contributions to dose from heavier ions. We compare our results with dose rate measurements by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) experiment on Lunar Reconnaissance Orbiter (Schwadron, N.A. et al. [2012]. J. Geophys. Res. 117, E00H13, http://dx.doi.org/10.1029/2011JE003978) and find them in good agreement, indicating that MCNPX can be confidently applied to studies of radiation dose at and within the surface of the Moon. We use our dose rate calculations to conclude that organic synthesis is plausible well within the age of the lunar polar cold traps, and that organics detected at the poles of the Moon may have been produced in situ. Our dose rate calculations also indicate that galactic cosmic rays can induce organic synthesis within the estimated age of the dark deposits at the pole of Mercury that may contain organics.

Radiation exposure among patients with the highest CT scan utilization in the emergency department

The risk of cancer from computed tomography (CT) scan radiation is a rising concern in the medical field. Our objectives were to determine how many patients received more than ten CT scans in an academic emergency department (ED) over the course of 7years and to quantify their radiation exposure and lifetime attributable risk of cancer. An electronic chart review was performed at our urban academic institution with an annual census of 110,000 patients. All patients who underwent a CT scan performed during ED management between the dates of January 2001 and December 2007 were identified. Specific predetermined data elements (e.g., subject demographics, type of CT scan) were extracted by two researchers blinded to hypothesis, using a preformatted data form. After identifying patients with more than ten CTs performed during the study period, radiation exposure was calculated based on accepted and reported radiation doses for the respective anatomic CTs, and lifetime attributable cancer risk was calculated based on the seventh report of the Biological Effects of Ionizing Radiation (BEIR VII) projections. Over the 7-year study period, 24,393 patients received 34,671 CT scans. The vast majority of patients (17,909) received a single CT. Twenty-six (0.1%) patients received more than ten CTs totaling 374 scans with an average radiation exposure of 83.4mSv. The maximum lifetime attributable risk for any individual in this cohort was 1.7% above the baseline cancer risk. Among those undergoing CT imaging in our ED, high-exposure patients (greater than ten scans) constituted a significant minority, while more than one in four patients underwent more than one CT scan during the study period. While the presumed overall risk of radiation-induced cancer continues to be low, it is important for the emergency physician to use clinical knowledge as well as concern for the patient when utilizing radiographic imaging. Increasing attributable cancer risk may have important public health implications in the future, regardless of the low individual risk.

86 Radiation Exposure Among Highest CT Scan Utilizers

The risk of cancer from CT scan radiation is a rising concern in the medical field. Our objective was to determine how many patients received more than 10 CT scans in the ED over the course of 7 years and to quantify their radiation exposure and cancer risk. An electronic chart review was performed at our inner city, academic institution with an annual census of 110,000 patients. All patients who underwent a CT scan performed during ED management between the dates of January 2001 and December 2007 were identified. Specific, pre-determined data elements (eg, subject demographics, type of CT scan) were extracted by 2 researchers blinded to hypothesis, using a pre-formatted data form. After identifying patients with more than 10 CTs performed during the study period, radiation exposure was calculated based on accepted and reported radiation doses for the respective anatomic CTs, and lifetime attributable cancer risk was calculated based on BEIR VII projections (7th report of the Biological Effects of Ionizing Radiation). Over the 7-year study period, 24,393 patients received 34,671 CT scans. 25 (0.1%) patients received more than 10 CTs, 272 (1%) received 5-10 CTs and 4239 (17%) received 2 CTs. Among those with more than 10 CTs, the mean, median, and range for number of CTs were 13.8, 13, and 11-23. The mean age of these patients was 53.3 years, with a range of 26-84 years. Mean radiation exposure was 93.8 mSv (range 24-240). The average lifetime attributable cancer risk above baseline in this group is 0.9% with a range from 0.2% to 2.4%. Among those undergoing CT in our ED, although high exposure patients (>10 scans) constituted a very small minority, attributable cancer risk increases (up to 2.4%) for these patients may have important public health implications.

Patient-specific radiation dose and cancer risk estimation in CT: part II. Application to patients.

Current methods for estimating and reporting radiation dose from CT examinations are largely patient-generic; the body size and hence dose variation from patient to patient is not reflected. Furthermore, the current protocol designs rely on dose as a surrogate for the risk of cancer incidence, neglecting the strong dependence of risk on age and gender. The purpose of this study was to develop a method for estimating patient-specific radiation dose and cancer risk from CT examinations. The study included two patients (a 5-week-old female patient and a 12-year-old male patient), who underwent 64-slice CT examinations (LightSpeed VCT, GE Healthcare) of the chest, abdomen, and pelvis at our institution in 2006. For each patient, a nonuniform rational B-spine (NURBS) based full-body computer model was created based on the patient's clinical CT data. Large organs and structures inside the image volume were individually segmented and modeled. Other organs were created by transforming an existing adult male or female full-body computer model (developed from visible human data) to match the framework defined by the segmented organs, referencing the organ volume and anthropometry data in ICRP Publication 89. A Monte Carlo program previously developed and validated for dose simulation on the LightSpeed VCT scanner was used to estimate patient-specific organ dose, from which effective dose and risks of cancer incidence were derived. Patient-specific organ dose and effective dose were compared with patient-generic CT dose quantities in current clinical use: the volume-weighted CT dose index (CTDIvol) and the effective dose derived from the dose-length product (DLP). The effective dose for the CT examination of the newborn patient (5.7 mSv) was higher but comparable to that for the CT examination of the teenager patient (4.9 mSv) due to the size-based clinical CT protocols at our institution, which employ lower scan techniques for smaller patients. However, the overall risk of cancer incidence attributable to the CT examination was much higher for the newborn (2.4 in 1000) than for the teenager (0.7 in 1000). For the two pediatric-aged patients in our study, CTDIvol underestimated dose to large organs in the scan coverage by 30%-48%. The effective dose derived from DLP using published conversion coefficients differed from that calculated using patient-specific organ dose values by -57% to 13%, when the tissue weighting factors of ICRP 60 were used, and by -63% to 28%, when the tissue weighting factors of ICRP 103 were used. It is possible to estimate patient-specific radiation dose and cancer risk from CT examinations by combining a validated Monte Carlo program with patient-specific anatomical models that are derived from the patients' clinical CT data and supplemented by transformed models of reference adults. With the construction of a large library of patient-specific computer models encompassing patients of all ages and weight percentiles, dose and risk can be estimated for any patient prior to or after a CT examination. Such information may aid in decisions for image utilization and can further guide the design and optimization of CT technologies and scan protocols.

Ultra low radiation dose cardiac CT

A 36 year old woman with a history of prior tobacco use and body mass index of 20.0 kg/m was referred for a cardiac computed tomography (CT) for evaluation of intermittent atypical chest discomfort which was provoked by exercise and relieved with rest. Given the patient's young age an individualized ultra low radiation dose protocol was selected. Using the dual-source CT scanner (Siemens Definition; 2×32× .6) the following parameters were used: prospective triggering at 65% of the R–R interval, 80 kV, 140 mA s. Beta blockers were administered and the average heart rate during the acquisition was 56 beats/minute. The CT demonstrated that all 3 coronary arteries were free of coronary artery disease and had a normal origin from the aortic root (Figs. 1 and 2). The effective radiation dose for the entire study was 0.7 mS v (0.2 mS v for the test bolus and 0.5 mS v for the coronary scan). To the best of our knowledge, this is the lowest reported radiation dose associated with a cardiac CT examination.

OCCUPATIONAL RADIATION DOSES TO OPERATORS PERFORMING CARDIAC CATHETERIZATION PROCEDURES

Cardiac catheterization procedures using fluoroscopy reduce patient morbidity and mortality compared to operative procedures. These diagnostic and therapeutic procedures require radiation exposure to patients and physicians. The objectives of the present investigation were to provide a systematic comprehensive summary of the reported radiation doses received by operators due to diagnostic or interventional fluoroscopically-guided procedures, to identify the primary factors influencing operator radiation dose, and to evaluate whether there have been temporal changes in the radiation doses received by operators performing these procedures. Using PubMed, we identified all English-language journal articles and other published data reporting radiation exposures to operators from diagnostic or interventional fluoroscopically-guided cardiovascular procedures from the early 1970's through the present. We abstracted the reported radiation doses, dose measurement methods, fluoroscopy system used, operational features, radiation protection features, and other relevant data. We calculated effective doses to operators in each study to facilitate comparisons. The effective doses ranged from 0.02-38.0 microSv for DC (diagnostic catheterizations), 0.17-31.2 microSv for PCI (percutaneous coronary interventions), 0.24-9.6 microSv for ablations, and 0.29-17.4 microSv for pacemaker or intracardiac defibrillator implantations. The ratios of doses between various anatomic sites and the thyroid, measured over protective shields, were 0.9 +/- 1.0 for the eye, 1.0 +/- 1.5 for the trunk, and 1.3 +/- 2.0 for the hand. Generally, radiation dose is higher on the left side of an operator's body, because the operator's left side is closer to the primary beam when standing at the patient's right side. Modest operator dose reductions over time were observed for DC and ablation, primarily due to reduction in patient doses due to decreased fluoroscopy/cineradiography time and dose rate by technology improvement. Doses were not reduced over time for PCI. The increased complexity of medical procedures appears to have offset dose reductions due to improvements in technology. The large variation in operator doses observed for the same type of procedure suggests that optimizing procedure protocols and implementing general use of the most effective types of protective devices and shields may reduce occupational radiation doses to operators. We had considerable difficulty in comparing reported dosimetry results because of significant differences in dosimetric methods used in each study and multiple factors influencing the actual doses received. Better standardization of dosimetric methods will facilitate future analyses aimed at determining how well medical radiation workers are being protected.