mSv For Effective Dose Research Articles

Cardiac computed tomography angiography with and without bolus tracking methods in infants with congenital heart disease.

The study investigated radiation dose, vascular computed tomography (CT) enhancement and image quality of cardiac computed tomography angiography (CCTA) with and without bolus tracking (BT) methods in infants with congenital heart disease (CHD). The volume CT dose index (CTDIvol) and dose length product (DLP) were recorded for all CT scans, and the effective dose was obtained using a conversion factors. The CT number for the ascending aorta (AO) and pulmonary artery (PA), image noise of muscle tissue and contrast-to-noise ratio (CNR) were measured and calculated. The median values in the groups with and without BT were 2.20mGy versus 0.44mGy for CTDIvol, 8.10mGy·cm versus 6.20mGy·cm for DLP, and 0.66mSv versus 0.51mSv for effective dose (p<0.001). There were no statistical differences in vascular CT enhancement, image noise, and CNR. CCTA without BT methods can reduce the radiation dose while maintaining vascular CT enhancement and image quality compared to CCTA with BT methods.

Evaluation of radiation risk for patients undergoing medical examinations in the Russian Federation

The aim of the study was to develop a methodology for assessing radiation risk for patients undergoing medical examinations in the Russian Federation. The methodology is based on the risk model of the ICRP Publication 103, the coefficients of lifetime radiation risk for the Russian population and the results of evaluating the doses of patients in the Russian Federation. For thirty examinations that define about 80% of the collective dose of the population of the Russian Federation from medical exposure, the radiation risk was calculated using «gold standard», — the organ doses and the corresponding sex/age risk coefficients for the Russian population. For other examinations (with the exception of mammography) the values of the risk coefficients normalized on 1 mSv of effective dose, which is the averaged value for four selected anatomical areas of the body: head, neck, chest and abdominal cavity — pelvis, were used. It is assumed that for such examinations the error of risk assessment will increase relative to the error of risk assessment for the aforementioned 30 examinations not more than 30%. It is shown that risk estimates for some examinations calculated using the “gold standard” may differ from such estimates on the base of effective dose and nominal risk coefficients averaged by age and the sex to the order of magnitude.

Abstract 188: Implementation of Choosing Wisely Recommendations for Stress-First Nuclear Myocardial Perfusion Imaging

Introduction: Current guidelines for myocardial perfusion imaging (MPI) encourage facilities to adopt patient-centered risk mitigation strategies such as individualized radiotracer dosing and stress-first imaging. Reducing radiation exposure is also a key recommendation of multiple societies participating in the Choosing Wisely campaign. The stated goal is for over 50% of studies to be performed with &lt;9 millisieverts (mSv) of radiation exposure. We hypothesized that adoption of a stress-first/stress-only imaging protocol would substantially reduce the median radiation dose administered in our nuclear lab. Methods: We switched the standard imaging protocol at the Malcom Randall VA Medical Center nuclear cardiology laboratory from rest-stress to stress-rest. To achieve this, a physician was required to review the stress images at the time they were obtained to determine if further imaging was indicated. Estimated effective radiation doses (in mSv) were calculated based on the radiotracer activity administered (in millicuries) used industry standards techniques. We compared 2 cohorts of patients: rest-stress studies consecutively done between 7/17/17 and 11/12/17 and stress-first studies consecutively done between 11/13/17 and 5/17/17. As a balancing measure, we compared the rate of normal studies between the cohorts. A normal MPI was defined as no evidence of ischemia or infarction with a preserved ejection fraction. Results: In the stress-first cohort, the median dose was 2.8 millisieverts (mSv) compared with 14.1 mSv in the rest-stress cohort (80.1% reduction, p&lt;0.0001). During the observed period, we estimate that 4,780 mSv of effective dose were avoided. In the rest-stress cohort, 424 studies were performed. In the stress-first cohort, 716 tests were performed, 423 stress only studies (59.1%) and 293 stress-rest studies (40.1%). The rate of normal studies in the stress-first cohort was not different from the rest-stress cohort (stress-first: 73.5%, (526/716) versus rest-stress: 71.7%, p=0.54, odds ratio 0.92, 95% CI 0.69-1.21) In the rest-stress cohort, 3 patients (1.0%) underwent coronary angiography and 2 patients (0.7%) underwent percutaneous coronary intervention (PCI). In the stress-first cohort 8 patients (1.1%) underwent coronary angiography and 2 patient (0.3%) underwent percutaneous coronary intervention (PCI). Conclusion: By switching from a rest-stress to a stress-first imaging protocol, we reduced the median radiation dose in our lab by 80%. We observed no change in the proportion of normal tests, suggesting no potential for harm with this strategy.

Letters to the Editor.

Letters to the Editor.

I Am Confused About the Cancer Risks Associated With CT: How Can We Summarize What Is Currently Known?

AJR:205, July 2015 A typical CT examination may involve 5–15 mSv of effective dose. The current data do not provide conclusive evidence regarding risk from a couple of CT examinations, though a minority of patients have undergone enough CT examinations to make some associated risk probable [8]. The question arises: Is there newer scientific information that warrants increasing the level of concern and intensifying the controversy? The answer is no. According to an International Commission on Radiological Protection (ICRP) report published in 2007 [9], “the estimates of cancer risk attributable to radiation exposure have not changed greatly in the past 17 years.” The ICRP has adjusted tissue weighting factors primarily to estimate additional risks for breasts and less risk for gonads, but the overall whole-body risk coefficient has changed only marginally. Then what is the cause for controversy? One reason is that the bounds of evidence are overstepped by extreme positions on both sides of the controversy. The ICRP clearly states that “the calculation of the number of cancer deaths based on collective effective doses from trivial individual doses should be avoided” [9]. According to ICRP, the collective effective dose quantity is an instrument for optimization, for comparing radiologic technologies and protection procedures, predominantly in the context of occupational exposure and group risk management. Collective effective dose is not intended as a tool for epidemiologic risk assessment, and it is inappropriate to use it in risk projections. The aggregation of very low doses to groups of individuals over extended time periods is misleading for individual risk projections [9]. Much as projections for cancer risk may be useful for policy planning, for strategic developments in managing radiation protection, they should not be used to characterize individual risk. I Am Confused About the Cancer Risks Associated With CT: How Can We Summarize What Is Currently Known?

Assessment of radiation hazards a result of natural radioactivity in water from Abyan delta, Yemen

This paper presents the concentrations of naturally occurring radionuclides 226Ra, 232Th and 40K measured in Groundwater collected from Abyan delta on Gulf of Aden in Yemen. Concentrations of radionuclides in samples were determined by gamma-ray spectrometer using HPGe detector with specially designed shield. The average activity concentrations were (1.71 ± 0.09 Bq l−1), (1.43 ± 0.05 Bq l−1) and (14.16 ± 0.45 Bq l−1) for 226Ra, 232Th and 40K, respectively. The annual effective doses mSv y−1 due to ingestion of 226Ra and 232Th for different age groups were also calculated. The results compared with the recommended value reported by World Health Organization.

Temporal Trends in Radiation Dose Associated with Coronary Computed Tomography Angiography

Background: In 2010, the International Atomic Energy Agency launched the “3A’s campaign” as an effective tool for primary cancer prevention. In 2011, the American Association of Physicists in Medicine recommended the size specific dose estimate (SSDE). Objectives: To audit doses of Coronary CT Angiography (Coronary CTA) in tertiary care referral center. Methods: We reviewed 998 consecutive Coronary CTA (from 2007 to 2012). Doses (CTDIvol mGy), DLP (mGy*cm), effective dose (DLP*0.014, mSv) were on-line archived. SSDE was estimated retrospectively. Appropriateness score was evaluated for exams performed from the 2010. Results: Overall median dose per Coronary CTA was 49.7 mGy for CTDIvol, 55.5 mGy for SSDE, 994.96 mGy*cm for DLP, 13.9 mSv for effective dose. Median DLP decreased over time (1452.94 in 2007, 1605.56 in 2008, 1113.49 in 2009, 759.99 in 2010, 448.61 in 2011 and 497.88 mGy*cm in 2012, p 1 (88%) CTDIvol underestimated SSDE (48.49 vs 57.19 mGy), whilst in patients with SDF < 1 (12%) CTDIvol overestimated SSDE (56.46 vs 50.3 mGy). Scans were appropriate in 58%, uncertain in 24%, and inappropriate in 18% of cases. Doses were similar in appropriate, uncertain or inappropriate examinations and in excellent-to-good (81%) vs. sufficient-to-poor (19%) image quality exams. Conclusions: Coronary CTA reference doses can be very misleading. SSDE can allow individual technique optimization. The dose is similar in appropriate and inappropriate examinations, and unrelated to image quality. The rate of inappropriate examinations is still too high even after dissemination of guidelines.

SKIN ENTRANCE RADIATION DOSE IN AN INTERVENTIONAL RADIOLOGY PROCEDURE

Monitoring of skin entrance radiation exposure in lengthy interventional procedures has been recommended because of the potential for skin injury. Fluoroscopy duration and dose-area product (DAP) are readily available real-time measurements. It would be of interest to study the correlation of these parameters and skin entrance radiation. Twenty neurological interventional procedures performed through the aortic arch were monitored. Two pieces of GafChromic XR Type R film were placed between the patient and the examination table. An observer recorded the fluoroscopy duration and DAP for each phase of the procedure. Each film was scanned post-procedure in RBG mode, and then the image was analyzed for peak skin entrance radiation dose (in air kerma). All DAP values were corrected according to a calibration with an ion chamber. With the DAP values for the respective phases of a procedure, the effective dose in a Reference Man was calculated. For these twenty cases, the means and standard deviations were 17.2+/-6.4 min for x ray on-time, 256+/-65 Gy cm (-2) for DAP, 94+/-34 cGy for peak skin entrance dose in air kerma, and 19.2+/-5.0 mSv for effective dose, respectively. The peak skin entrance dose was correlated to fluoroscopy duration, DAP, and effective dose with the r(2)-values of 0.48, 0.46, and 0.09, respectively. The correlation with DAP or fluoroscopy duration was not sufficiently strong to infer skin entrance dose from either of these parameters. Therefore, skin entrance dose should be determined directly.

SU‐FF‐I‐19: Skin Entrance Radiation Dose in An Interventional Radiology Procedure

Purpose: Monitoring of skin entrance radiation exposure in lengthy interventional procedures with X‐ray is recommended because of the potential for skin injury. X‐ray on‐time and dose‐area product (DAP) are readily available real‐time measurements. It would be of interest to study the correlation of these parameters and skin entrance radiation. Method and Materials: Twenty interventional procedures performed through the aortic arch to one or more of its three associated major blood vessels were monitored. Two pieces of GafChromic XR Type R film were placed between the patient and the examination table. An observer recorded the X‐ray on‐time and DAP for each phase of the procedure. Each film was scanned post‐procedure in RBG mode, and then the red component of the image was analyzed for peak skin entrance radiation dose (in air kerma) after proper calibration. All DAP values were corrected according to a calibration with an ion chamber. With the corrected DAP values for the respective phases of a procedure, and the Monte Carlo model used by the National Radiological Protection Board (United Kingdom), the effective dose in a standard man was calculated. Results: For these twenty cases, the mean and standard deviation of were 17.2 ± 6.4 minutes for X‐ray on‐time, 256 ± 65 Gy.cm2 for DAP, 94 ± 34 cGy for peak skin entrance dose in air kerma, and 13.2 ± 3.1 mSv for effective dose. The peak skin entrance dose was correlated to X‐ray on‐time, DAP and effective dose with the coefficients of 0.69, 0.68, and 0.49 respectively. The corresponding r‐values in linear regression analysis were 0.48, 0.46, and 0.24. Conclusion: The poor correlation with DAP and X‐ray on‐time suggests that skin dose should be measured independently. However, peak skin entrance dose would be a poor indicator for effective dose. Determination of the latter requires more detail information.

Personal dose monitoring of employees at the institute of modern physics, China.

The radiation field at the accelerator facility consists of radiation produced immediately and of secondary radiation induced by activation etc. As the accelerator building and the experimental hall are closed and inaccessible during accelerator operation, the exposure received by the employees at the IMP (Institute of Modern Physics) comes almost totally from the induced radiation. The methods and the results of personal dose monitoring from 1986 to 1999 at the IMP are presented. During the period, the total number of monitored individuals was 1960, and the average annual effective dose was 0.10 mSv. The number recording less than 0.1 mSv of effective dose was 1471 individuals. amounting to 77% of the total. Only six individuals had received effective doses between 5.0 mSv and 10 mSv. The maximum effective dose of 10 mSv was received by workers repairing the accelerator.

Quality criteria implementation for brain and lumbar spine CT examinations.

A study was undertaken to implement the quality criteria proposed by the European Commission for brain general and lumbar spine (disc herniation) CT examinations. The proposed criteria were evaluated for samples including 93 brain and 86 lumbar spine CT examinations, with special emphasis on the diagnostic and radiation dose requirements. The extent to which the image criteria had been achieved was evaluated after two independent observers had each read the images twice. Dose measurements were conducted in parallel to estimate the proposed dose quantities needed to obtain the images. For brain examinations, we found that a group of image criteria were largely met, and met uniformly in all sites. One criterion (1.2.5) was frequently fulfilled but had intermediate values for two sites; the remaining criteria were fulfilled to different extents, although for criteria 1.2.1 and 1.2.2, scores were lower than 50% and 70%, respectively. The mean percentage image quality score had values between 57% and 78%, with variation coefficients in the range 30-68%. Mean values of the dose quantities were in the ranges 44-74 mGy for weighted CT dose index (CTDIw), 497-1018 mGy cm for dose-length product (DLP) and 1.1-2.2 mSv for effective dose (E). CTDIw and DLP were not correlated because of significant variations in the scanned length, whereas DLP and E were strongly correlated. A weak relationship between image quality score and DLP was found for the sample as a whole. For lumbar spine examinations, none of the critical reproduction image criteria was systematically achieved. One group of criteria (1.2.7, 1.2.8 and 1.2.9) was fulfilled to a large extent in many departments, but fulfilment of the remainder varied widely. The mean score fluctuated in the range 39-88%, with three groups of differences: low (39-51%), intermediate (67-71%) and high (85-88%). Mean values of the CTDIw varied between sites in the range 27-48 mGy. Mean DLP values varied between 188 mGy cm and 333 mGy cm, and the mean effective dose ranged between 3 mSv and 5 mSv. There were significant differences in effective dose between men and women. By sites, there was no relationship between DLP and mean score, with the highest image score associated with intermediate dose values. The percentage disagreement among the observers about a given criterion ranged between 2% and 22% for brain, and between 3% and 46% for lumbar spine.