Diagnostic medical exposures in the U.K

Evaluation of institutional whole-body and extremity occupational radiation doses in nuclear medicine

This study evaluated nuclear medicine occupational radiation doses at Sultan Qaboos University Hospital, a 700-bed tertiary care teaching hospital in Oman. Personal effective whole-body doses, Hp(10), and extremity doses, Hp(0.07), were collected for 19 medical radiation workers over a 7-year period (2015-2021). Personal doses for four professional groups were measured using calibrated thermo-luminescence dosemeters ((LiF:Mg,Ti) TLD-100). The average, median and maximum cumulative doses were compared against the annual whole-body and extremity dose limits (20 mSv and 500 mSv y-1, respectively) and local dose investigation level (DIL; 6 mSv y-1). Personal whole-body doses (average:median:maximum) for technologists, medical physicists, nuclear medicine physicians and nurses were 1.8:1.1:7.8, 0.3:0.3:0.4, 0.1:0.1:0.2 and 0.1:0.1:0.2 mSv, respectively. Personal extremity doses for left and right hand (average and maximum doses) follow similar trends. Average annual effective whole-body and extremity doses were well below the recommended annual dose limits. The findings suggest lowering local DIL for all staff except for technologists.

Impact of Computed Tomography Scans on the Risk of Thyroid Disease in Minor Head Injury Patients: A Population-Based Retrospective Cohort Study

We investigated the association between head computed tomography (CT) scans and the risk of noncancer thyroid diseases in patients with minor head injury in a Taiwanese healthcare setting. For this retrospective population-based cohort study, the 2009–2013 Longitudinal Health Insurance Database was used to include patients with a minor head injury at admission or emergency visit between 2009 and 2013. Multivariate analysis with a multiple Cox regression model was applied to analyze the data. According to whether a CT scan was conducted within 14 days of admission, patients were divided into a CT scan group (n = 14,041) or a non-CT scan group (n = 34,684). No increased incidence of thyroid diseases was observed in the CT scan group regardless of the number of CT scans performed. The incidence rate ratio for one scan was 1.10 (95% confidence interval: 0.94–1.29) and for two or more scans was 1.09 (95% confidence interval: 0.93–1.28). In conclusion, this population-based cohort study showed that a head CT scan is not associated with increased risk of thyroid disease in patients with minor head injury. The short-term adverse effects on the thyroid could be mild when a regular CT scan is appropriately performed.

Knowledge and practice of computed tomography exposure parameters amongst radiographers in Jordan

OBJECTIVE

To investigate the knowledge and practice of computed tomography (CT) radiographers working in Jordan.

MATERIALS AND METHODS

This Institutional Review Board (IRB) approved study disseminated a questionnaire via social media and recruited 54 Jordanian CT radiographers. The questionnaire comprised 36 questions divided into four sections: demographics; an evaluation of knowledge regarding CT exposure; modifications to CT exposure for paediatric patients; dose units and diagnostic reference levels (DRLs). Descriptive and inferential statistics including Chi-square tests, Mann-Whitney U tests, independent samples t-tests and Kruskal-Wallis H tests were employed. Statistical significance was considered below p < 0.05.

RESULTS

The 54 participants had various qualifications, with the majority holding a Bachelor's degree (n = 35, 64.8%) and the rest holding a Diploma (n = 19, 35.2%). In order to pass the questionnaire, participants needed to score 13 correct answers. The overall number of radiographers who correctly passed the questionnaire was 48 (88.9%). None of the participants correctly stated all the DRL values for chest, abdomen and brain CT. However, four out of 54 respondents (7.4%) knew the chest DRL value, three (5.6%) participants correctly estimated the abdominal DRL value but only two (3.7%) knew the DRL for the brain.

CONCLUSION

Good general knowledge was found amongst radiographers regarding the relationship of each exposure parameter to the image quality and patient dose. However, there was poor knowledge of diagnostic reference levels and the order of the organ radiation sensitivity. The need for CT radiographers to undertake further education that focuses on radiation exposure in CT is highlighted.

An update on radiation absorbed dose to patients from diagnostic nuclear medicine procedures in Tehran: A study on four academic centers

Purpose:

Use of radiopharmaceuticals for diagnostic nuclear medicine procedures is one of the main sources of radiation exposure. We performed this study with respect to the rapid growth in nuclear medicine in Iran and lack of updated statistics.

Materials and Methods:

The data were obtained for all active Nuclear Medicine Centers affiliated to Shahid Beheshti University of Medical Sciences during 2009 and 2010.

Results:

The most frequently performed procedures were bone (30.16%), cardiac (28.96%), renal (17.97%), and thyroid (7.93%) scans. There was a significant decrease in the number of thyroid scintigraphies with ¹³¹I and ^99mTc-sulfur colloid liver/spleen scans and tremendous increase in the frequencies of cardiac and bone scintigraphies compared to one decade ago.

Conclusion:

Compared to previous studies, there were striking changes in trends of diagnostic nuclear medicine procedures in Tehran. This field is still evolving in the country, and this trend will further change with the introduction of positron emission tomography scanners in future.

The disproportionate risk burden of CT scanning on females and younger adults in Australia: a retrospective cohort study

OBJECTIVES

To explore the interaction of computed tomography (CT) use, dose and radiation risk of Australian Medicare-funded CT scanning and the impact on cancer incidence and mortality.

METHODS

This retrospective cohort study used records of Medicare subsidised CT scans in Australia (2006/07 to 2011/12) and Australian CT dosimetry. The annual number, rate and adjusted likelihood of CT were determined for gender, age and examination type. Incident cancer and cancer-related mortality attributable to CT in Australia were estimated using lifetime attributable risk coefficients, dosimetry and scan numbers.

RESULTS

The number of CT scans increased by 36% from 2006/07 to 2011/12. Only patients aged 0-4 years did not present an increase in CT scanning rates. Females were 11% more likely to be scanned than males. Head, abdomen/pelvis and spine CT scans were the most likely areas scanned. Females were attributed 61% of both incident cancers and cancer-related mortality from 55% of scans performed. Patients aged 15-44 years were attributed 37% of incident cancers and 30% of cancer-related mortality from 26% of CT scans.

CONCLUSIONS

CT in Australia is increasing, including in groups at higher risk from ionising radiation. This presents a complex set of risk/benefit considerations for clinicians and policy makers.

Establishment of diagnostic reference levels for CT trunk examinations in the western region of Saudi Arabia

Diagnostic reference levels (DRLs) are an important optimisation tool, which aid in identifying abnormally high dose levels. These are currently not available in Saudi Arabia, and this research aims to remedy this. CT dose data (DLP and CTDIvol) were collected for a minimum number of 10 adult patients of average size (60-80 kg) presenting for a range of CT examinations from public hospitals in the western region of Saudi Arabia. These include routine chest, high-resolution chest (HRCT), pulmonary angiography (CTPA), abdomen and pelvis (AP) and the combined chest, abdomen and pelvis (CAP) CT examinations. Mean values for each site were calculated, and the 75th percentile of DLP and CTDIvol was used as a basis for DRLs. Data for 550 patients were collected from 14 hospitals over a 7-month period. The rounded third-quartile CTDIvol and DLP were 18 mGy and 630 mGy cm(-1) for chest CT, 20 mGy and 600mGy cm(-1) for HRCT, 18 mGy and 480 mGy cm(-1) for CTPA, 15 mGy and 800 mGy cm(-1) for AP, and 16 mGy and 1040 mGy cm(-1) for CAP, respectively. Regional DRLs have been proposed from this study. Dose variations across CT departments have identified an urgent need for optimisation to improve distribution of observed doses for CT examinations.

The Impact of Iterative Reconstruction on Computed Tomography Radiation Dosimetry: Evaluation in a Routine Clinical Setting

Purpose

To evaluate the effect of introduction of iterative reconstruction as a mandated software upgrade on radiation dosimetry in routine clinical practice over a range of computed tomography examinations.

Methods

Random samples of scanning data were extracted from a centralised Picture Archiving Communication System pertaining to 10 commonly performed computed tomography examination types undertaken at two hospitals in Western Australia, before and after the introduction of iterative reconstruction. Changes in the mean dose length product and effective dose were evaluated along with estimations of associated changes to annual cancer incidence.

Results

We observed statistically significant reductions in the effective radiation dose for head computed tomography (22–27%) consistent with those reported in the literature. In contrast the reductions observed for non-contrast chest (37–47%); chest pulmonary embolism study (28%), chest/abdominal/pelvic study (16%) and thoracic spine (39%) computed tomography. Statistically significant reductions in radiation dose were not identified in angiographic computed tomography. Dose reductions translated to substantial lowering of the lifetime attributable risk, especially for younger females, and estimated numbers of incident cancers.

Conclusion

Reduction of CT dose is a priority Iterative reconstruction algorithms have the potential to significantly assist with dose reduction across a range of protocols. However, this reduction in dose is achieved via reductions in image noise. Fully realising the potential dose reduction of iterative reconstruction requires the adjustment of image factors and forgoing the noise reduction potential of the iterative algorithm. Our study has demonstrated a reduction in radiation dose for some scanning protocols, but not to the extent experimental studies had previously shown or in all protocols expected, raising questions about the extent to which iterative reconstruction achieves dose reduction in real world clinical practice.

Occupational radiation exposure among the staff of departments of nuclear medicine and diagnostic radiology in Kuwait

OBJECTIVES

To investigate radiation exposure among the staff of departments of nuclear medicine (NM) and diagnostic radiology (DR) during 2008 and 2009 and to compare the mean doses received with the limit of 20 mSv/year of the International Commission of Radiological Protection (ICRP).

MATERIALS AND METHODS

The whole-body dose or effective dose, i.e. Hp(10), and the skin dose, i.e. Hp(0.07), of the staff of departments of NM and DR in Kuwait for the period of 2008 and 2009 were taken from the national thermoluminescent dosimetry database. A total of 1,780 radiation workers, grouped as NM physicians, radiologists, NM technologists, and DR technologists, from 7 departments of NM and 12 departments of DR were included. The annual average Hp(10) and Hp(0.07) were calculated for each group and comparisons were made between the groups and the years. A two-sided Mann-Whitney test was carried out, at the p = 0.05 level, to compare the means. The mean Hp(10) was compared with the limits of the ICRP.

RESULTS

Of the 16 distributions of Hp(10) and Hp(0.07), 10 were normal, with a mean annual Hp (10) in 2008 of 1.06, 1.03, 1.07, and 1.05 mSv for NM physicians, radiologists, NM technologists, and DR technologists, respectively. The corresponding Hp(0.07) values for 2008 were 1.03, 1.00, 1.05, and 1.03 mSv, respectively. Small but significant (p < 0.001) reductions in Hp(10) and Hp(0.07) were observed in 2009 for NM technologists and DR technologists. In all other cases, no significant (p > 0.072) differences were found.

CONCLUSION

The annual average Hp(10) was well below the limit of the ICRP.

Population radiation dose from diagnostic nuclear medicine procedures in the Tehran population in 1999-2003: striking changes in only one decade

Use of unsealed radiopharmaceuticals in Iran's nuclear medicine centers has expanded rapidly in the last decade. As part of a nationwide survey, this study was undertaken to estimate the radiation risk due to the diagnostic nuclear medicine procedures performed in Tehran in 1999-2003. During the five years of the study, the data of 101,540 yearly examinations of diagnostic nuclear medicine were obtained for 34 (out of 40) active nuclear medicine centers in Tehran. The patients studied were aged 1 y, 5 y, 10 y, 15 y, and adults (>15 y). Compared to an earlier investigation in 1989 (which was published in 1995), striking changes were found to be occurring in the trends of nuclear medicine in Tehran in a matter of a decade. The frequency of cardiac examinations increased from less than 1% in 1989 to 43.2% (mean of 5 y) in 2003; thyroid examinations, with the relative frequency of higher than 80% in 1989, decreased to 26.7% in the current investigation (averaged for 2001); and the number of overall examinations per 1,000 population of Tehran increased from 1.9 in 1989 to 8.8 in this study (about fourfold). The decrease in relative frequency of thyroid examinations could be attributed to the lower referral policy (mainly by specialists), decreased incidence of goiter due to implementation of programs for iodine enrichment diets, introduction of fine needle aspiration (FNA), and sonography techniques for diagnosis of thyroid disease. The large increase in relative frequency of cardiac examinations could be due to the increase in the number of single photon emission computerized tomography (SPECT) systems in recent years as compared to 1989 in Tehran. The collective effective dose increased from 400 (person-Sv) in 1999 to 529 (person-Sv) in 2003, and the effective dose per capita increased from 34.80 μSv in 1999 to 44.06 μSv in 2003 (average, 35.60 μSv).

A dose comparison survey in CT departments of dedicated paediatric hospitals in Australia and Saudi Arabia

AIM: To measure and compare computed tomography (CT) radiation doses delivered to patients in public paediatric hospitals in Australia and Saudi Arabia.

METHODS: Doses were measured for routine CT scans of the head, chest and abdomen/pelvis for children aged 3-6 years in all dedicated public paediatric hospitals in Australia and Saudi Arabia using a CT phantom measurement cylinder.

RESULTS: CT doses, using the departments’ protocols for 3-6 year old, varied considerably between hospitals. Measured head doses varied from 137.6 to 528.0 mGy_·cm, chest doses from 21.9 to 92.5 mGy_·cm, and abdomen/pelvis doses from 24.9 to 118.0 mGy_·cm. Mean head and abdomen/pelvis doses delivered in Saudi Arabian paediatric CT departments were significantly higher than those in their Australian equivalents.

CONCLUSION: CT dose varies substantially across Australian and Saudi Arabian paediatric hospitals. Therefore, diagnostic reference levels should be established for major anatomical regions to standardise dose.

Justification in clinical radiological practice: a survey among staff of five London hospitals

This study represents a survey performed among staff who, according to the Ionising Radiation (Medical Exposures) Regulations of 2000 (IRMER), are responsible for justifying radiological examinations in the UK. The aim of the survey is to map the current situation regarding knowledge of risks from X-ray exposures and the criteria used for their justification. An anonymous electronic questionnaire was emailed to 219 radiologists and radiographers of five National Health Service hospitals. The questions were designed to investigate the way the sample group defines/assesses risk and benefit when justifying medical exposures, and to test their knowledge on radiation doses, risk communication, and on relevant national legislation. The majority of the respondents are aware of the relevant legislation/guidelines. Patient's medical condition, age and sex, and alternative techniques using less or no ionising radiation are the main criteria used for justification. However, when estimating the effective dose of various examinations in chest radiograph equivalents, the majority of the responses were incorrect. Although there is good knowledge of legislation around justification of medical exposures, there seems to be a lack of knowledge on radiation doses and risks among IRMER practitioners.

Diagnostic reference levels from the ACR CT Accreditation Program

PURPOSE

The aim of this study was to assess the distribution of CT dose index (CTDI) values reported by sites undergoing ACR CT accreditation between 2002 and 2004.

METHODS

Weighted CTDI (CTDI(w)) values were measured and reported by sites applying for ACR CT accreditation, and the percentage of scanners with values above the 2002 ACR diagnostic reference levels (DRLs) was determined. Acquisition parameters for a site's adult head, adult abdominal, and pediatric abdominal examinations were used to calculate volume CTDI (CTDI(vol)), and the average and standard deviation were calculated by year. Histogram analysis was performed to determine 75th and 90th percentiles of CTDI(vol).

RESULTS

Between September 2002 and December 2004, 829 scanners underwent the accreditation process. Volume CTDI values (average ± SD) for 2002, 2003, 2004, and 2002 to 2004, respectively, were 66.7 ± 23.5, 58.5 ± 17.5, 55.8 ± 15.7, and 59.1 ± 18.6 mGy for adult head examinations; 18.7 ± 8.0, 19.2 ± 8.6, 17.0 ± 7.6, and 18.4 ± 8.3 for adult abdominal examinations; and 17.2 ± 9.7, 15.9 ± 8.6, 14.0 ± 7.0, and 15.5 ± 8.4 for pediatric abdominal examinations. For 2004 data, 23.8%, 2.3%, and 6.9% of sites reported doses above the 2002 CTDI(w) reference levels, compared with 49.6%, 4.7%, and 15% for 2002 data for adult head, adult abdominal, and pediatric abdominal examinations, respectively. Seventy-fifth percentiles of CTDI(vol) were 76.8 mGy (adult head, 2002 only), 22.2 mGy (adult abdominal), and 20.0 mGy (pediatric abdominal).

CONCLUSIONS

From 2002 to 2004, average CTDI(vol) values decreased by 10.9, 1.7, and 3.2 mGy for adult head, adult abdominal, and pediatric abdominal examinations. Effective January 1, 2008, the ACR program implemented United States-specific diagnostic reference levels of 75, 25, and 20 mGy, respectively, for the CTDI(vol) of routine adult head, adult abdominal, and pediatric abdominal CT scans.

Radiation dose and excess risk of cancer in children undergoing neuroangiography

OBJECTIVE

The primary goal of this study was to determine the radiation dose received during diagnostic and interventional neuroangiographic procedures in a group of pediatric patients. A second goal was to approximate the total average radiation dose from all angiographic and CT studies that pediatric patients underwent during the study period and to estimate the increased risk of cancer incidence in this patient group.

MATERIALS AND METHODS

The study subjects were pediatric patients who had undergone one or more neuroangiographic procedures at Harborview Medical Center between December 1, 2004, and April 30, 2008. Recorded radiation doses were converted to entrance skin dose (ESD) and effective dose (ED) to indicate deterministic and stochastic damage, respectively. The Biologic Effects of Ionizing Radiation (BEIR) VII, phase 2, report was used to estimate the expected increased risk of cancer in the study population.

RESULTS

For diagnostic and therapeutic procedures, a mean ED of 10.4 and 34.0 mSv per procedure was calculated, respectively. The ESD values proved too low to cause deterministic harm. The estimated number of excess cases of malignancy projected from the total average radiation exposure was 890.6 per 100,000 exposed male children and 1,222.5 per 100,000 exposed females, an overall increase of approximately 1% to the lifetime attributable risk of cancer.

CONCLUSION

Although both angiography and CT have revolutionized the practice of medicine and confer benefits to patients, it is important that we continue to investigate the possible adverse effects of these technologies. Protocols that minimize radiation dose without compromising a study should be implemented.

Overview of patient dosimetry in diagnostic radiology in the USA for the past 50 years

This review covers the role of medical physics in addressing issues directly related to patient dosimetry in radiography, fluoroscopy, mammography, and CT. The sections on radiography and fluoroscopy radiation doses review the changes that have occurred during the last 50 to 60 years. A number of technological improvements have contributed to both a significant reduction in patient and staff radiation doses and improvements to the image quality during this period of time. There has been a transition from film-screen radiography with hand dip film processing to electronic digital imaging utilizing CR and DR. Similarly, fluoroscopy has progressed by directly viewing image intensifiers in darkened rooms to modern flat panel image receptor systems utilizing pulsed radiation, automated variable filtration, and digitally processed images. Mammography is one of the most highly optimized imaging procedures performed, because it is a repetitive screening procedure that results in annual radiation exposure. Mammography is also the only imaging procedure in the United States in which the radiation dose is regulated by the federal government. Consequently, many medical physicists have studied the dosimetry associated with screen-film and digital mammography. In this review, a brief history of mammography dose assessment by medical physicists is discussed. CT was introduced into clinical practice in the early 1970s, and has grown into one of the most important modalities available for diagnostic imaging. CT dose quantities and measurement techniques are described, and values of radiation dose for different types of scanner are presented. Organ and effective doses to adult patients are surveyed from the earliest single slice scanners, to the latest versions that include up to two x-ray tubes and can incorporate as many as 256 detector channels. An overview is provided of doses received by pediatric patients undergoing CT examinations, as well as methods, and results, of studies performed to assess the radiation absorbed by the conceptus of pregnant patients.

Estimation of patients' organ doses and conceptus doses from selected X-ray examinations in two Nigeria X-ray centres

In this study, organ and conceptus doses of patients undergoing chest, abdomen and skull radiograph examinations at two Nigeria X-ray centres, Niger State General Hospital (NGH) and Two-Tees (TTX), are reported. Air kerma was measured, and entrance surface dose (ESD) and half-value layer estimated for each set of tube potential (kV(p)), focus to skin distance and current-time product (mAs) used for each of the patients included in this study. Results show that the mean air kerma in the two centres are similar for the three projections considered in this study. Organ doses ranged from <0.01 to 2.18 mGy in NGH and from <0.01 to 1.29 mGy in TTX for examinations of the abdomen, from <0.01 to 0.20 mGy in NGH and from <0.01 to 0.13 mGy in TTX for examinations of the skull and from <0.01 to 3.90 mGy in NGH and from <0.01 to 1.96 mGy in TTX for examinations of the chest. Generally, no significant difference is seen between the organ doses of male and female patients. In NGH, organ doses are generally greater than those from TTX for the three examinations. The mean ESDs for examinations of the chest postero-anterior, abdomen antero-posterior (AP) and skull AP are, respectively, 5.37, 6.28 and 4.24 mGy in NGH, and 5.82, 5.33 and 4.76 mGy in TTX. The ESDs reported in this study, except for examinations of the chest, are generally lower than comparable values published in the literature. Conceptus doses were also estimated for female patients using normalised published conceptus dose data for abdomen examinations. The estimated conceptus doses were >1 mGy even when the conceptus was located 12 cm below the surface of the abdomen.

DEXA as a predictor of fixator removal in distraction osteogenesis

Premature removal of the fixator after a lengthening procedure can result in gradual bending or acute fracture of the regenerate. We reviewed the records of 26 patients who underwent 28 limb lengthenings between 1997 and 2005 to assess the post lengthening regenerate fracture rate and bone healing index when using dual energy xray absorptiometry (DEXA) to aid in deciding on when to remove the fixator. Sixteen male and 10 female patients with an average age at lengthening of 12.3 years underwent an average lengthening of 5.2 cm (range, 3-9.1 cm). Nineteen femurs and nine tibiae were lengthened. Serial monthly DEXA scans were analyzed for bone mineral density. Bone healing indices and post fixator removal complications were assessed. The fixators were removed once the bone mineral density had plateaued to a less than 10% increase and plain radiographs showed no obvious defects precluding fixator removal. There were no regenerate fractures and only one fracture in the proximal segment of the lengthened bone after apparatus removal and the healing index for the series averaged 47 d/cm (range, 20-73 d/cm). Using serial DEXA scans during the consolidation phase of lengthening has a low rate (3.6%) of fractures while maintaining an acceptable bone healing index without excessively increasing fixation time.

LEVEL OF EVIDENCE

Level IV, therapeutic retrospective study. See the Guidelines for Authors for a complete description of levels of evidence.

Effective doses in radiology and diagnostic nuclear medicine: a catalog

Medical uses of radiation have grown very rapidly over the past decade, and, as of 2007, medical uses represent the largest source of exposure to the U.S. population. Most physicians have difficulty assessing the magnitude of exposure or potential risk. Effective dose provides an approximate indicator of potential detriment from ionizing radiation and should be used as one parameter in evaluating the appropriateness of examinations involving ionizing radiation. The purpose of this review is to provide a compilation of effective doses for radiologic and nuclear medicine procedures. Standard radiographic examinations have average effective doses that vary by over a factor of 1000 (0.01-10 mSv). Computed tomographic examinations tend to be in a more narrow range but have relatively high average effective doses (approximately 2-20 mSv), and average effective doses for interventional procedures usually range from 5-70 mSv. Average effective dose for most nuclear medicine procedures varies between 0.3 and 20 mSv. These doses can be compared with the average annual effective dose from background radiation of about 3 mSv.

Male gonadal dose of ionizing radiation delivered during X-ray examinations and monthly probability of pregnancy: a population-based retrospective study

Background

Male gonadal exposure to ionizing radiation may disrupt spermatogenesis, but its influence on the fecundity of couples has been rarely studied. We aimed to characterize the influence of male gonadal dose of ionizing radiation delivered during radiodiagnostic on the monthly probability of pregnancy.

Methods

We recruited a random sample of women who retrospectively described 1110 periods of unprotected intercourse beginning between 1985 and 1999 and leading either to a live birth or to no pregnancy; their duration was censored after 13 months. The male partner answered a telephone questionnaire on radiodiagnostic examinations. We assigned a mean gonadal dose to each type of radiodiagnostic examination. We defined male dose for each period of unprotected intercourse as the sum of the gonadal doses of the X-ray examinations experienced between 18 years of age and the date of discontinuation of contraception. Time to pregnancy was analysed using a discrete Cox model with random effect allowing to estimate hazard ratios of pregnancy.

Results

After adjustment for female factors likely to influence fecundity, there was no evidence of an association between male dose and the probability of pregnancy (test of homogeneity, p = 0.55). When compared to couples with a male gonadal dose between 0.01 and 0.20 milligrays (n = 321 periods of unprotected intercourse), couples with a gonadal dose above 10 milligrays had a hazard ratio of pregnancy of 1.44 (95% confidence interval, 0.73–2.86, n = 31).

Conclusion

Our study provides no evidence of a long-term detrimental effect of male gonadal dose of ionizing radiation delivered during radiodiagnostic on the monthly probability of pregnancy during the year following discontinuation of contraceptive use. Classification errors due to the retrospective assessment of male gonadal exposure may have limited the statistical power of our study.

Multi–Detector Row CT Pulmonary Angiography: Comparison of Standard-Dose and Simulated Low-Dose Techniques

PURPOSE

To compare standard-dose and simulated low-dose multi-detector row computed tomography (CT) pulmonary angiography.

MATERIALS AND METHODS

The institutional review board approved the study protocol and waived patient informed consent because the study was based on existing data. Raw data from 21 CT scans obtained at 90 mAs (effective) in 11 women and 10 men aged 25-74 years (mean, 52 years) that showed at least one filling defect within a pulmonary artery were used to simulate CT pulmonary angiography with reduced radiation doses, at 60, 40, 20, and 10 mAs. Three independent readers coded each central and segmental pulmonary artery twice as positive, negative, or inconclusive for presence of a filling defect. The second reading of images obtained with 90 mAs was considered the reference standard. The potential dependence of results on reader, radiation dose, and/or pulmonary artery segment was investigated with analysis of variance. Positive and negative consistent values were calculated for standard-dose scans and simulated low-dose scans in the first reading session. The branching order of the artery with the most distal filling defect was recorded. The quality of intravascular contrast at each tube current-time product setting was scored on a five-point scale. Interreader agreement was investigated with kappa statistics.

RESULTS

The frequencies of positive and inconclusive results (P = .21 and .08, respectively), positive and negative consistent values (P = .19 and .34, respectively), and branching order of the most distal artery with a filling defect (P = .41) did not depend on the radiation dose. Values for inter- and intrareader agreement were higher for central arterial segments than for branch arteries but were not influenced by dose reduction, regardless of arterial segment. The quality of intravascular contrast was not significantly changed when the tube current-time product was reduced from 90 to 40 mAs (P = .10 to >.99).

CONCLUSION

The evaluated parameters remained stable when tube current-time product was reduced from 90 (effective) to 10 (simulated) mAs at multi-detector row CT pulmonary angiography.

Radiological parameters and radiation doses of patients undergoing abdomen, pelvis and lumbar spine X-ray examinations in three Nigerian hospitals

Thermoluminescent dosemeters (TLDs) have been used to measure the entrance surface doses (ESDs) of patients undergoing pelvis, abdomen and lumbar spine diagnostic X-ray examinations in Nigeria. A total of three public hospitals and 171 patients were included in this investigation. The ages of the patients involved were from 40 years to 85 years, while their weights ranged from 64 kg to 73 kg. Mean, median, first and third quartiles of ESDs are reported. The results showed that in most cases, for each of the examinations, the individual ESD values are found to be comparable with, and higher than, those from Ghana and Tanzania, respectively. The mean ESD values are also found to be within the range of mean ESD values that have been previously been reported from countries outside Africa. When compared with the European Community (EC) reference values, the mean ESDs were found to be below the reference values in only two of the hospitals. The ranges found in this work are high and this indicates more attention needs to be given to X-ray facilities in the country. This also suggests that radiographic departments need to review their radiographic practices in order to bring their doses to optimum levels. Effective doses were also calculated from the ESD values. The mean effective doses were found to be generally low when compared with those found in the literature from other countries including two African countries. The radiographic parameters used for all the patients were also compared with the European criteria. It is recommended that the tube filtration at one hospital be increased. The importance of good regulatory activities and trained personnel is stressed in this work. Apart from the fact that the data provided in this work will be useful for the formulation of national guidance levels, they also provide patient dosimetry information on healthcare level IV countries.

Survey of radiological techniques and doses of children undergoing some common x-ray examinations in three hospitals in Nigeria

A dosimetric survey has been carried out in order to investigate typical radiation doses for children undergoing a number of common x-ray examinations in Nigeria. The results presented in this work are derived from the data of 226 children from three different hospitals included in the survey. Assuming the sample is representative of national practice patterns, pediatric chest examinations are the most frequent radiological examinations. Doses were measured by attaching thermoluminescent dosimeters to the patient's skin to determine entrance surface dose (ESD). The mean and standard deviation of the individual ESD values are reported. Comparisons were made between these doses and diagnostic reference levels, and also between the doses and those from other countries. The mean ESD values in the present work are found to be generally higher than those found in an UNSCEAR document and the NRPB diagnostic reference levels. The ratio of maximum ESD to minimum ESD, a parameter that characterizes ESD variation, was found to be less than 10 in each of the hospitals, while across the three hospitals the ratio was found to be greater than 10. The reasons for the high mean ESD and the variations in patients' ESD values have been discussed in terms of regulatory control, personnel, difference in radiological techniques, performance of x-ray facility, film processing condition, and the type of film-screen combination used. The results presented in this work will form part of the baseline data needed for deriving national guidance levels of pediatric radiological examination. In addition, it will also serve as a source of additional information on pediatric patient dosimetry. Suggestions are given on how to reduce doses to pediatric patients during x-ray examinations, especially in developing countries.

Orbital, thyroid, and breast superficial radiation shielding for patients undergoing diagnostic CT

Computed tomography (CT) now provides over 30% of all radiation received from medical imaging. Superficial radiosensitive organs, such as the thyroid, eyes, and breasts receive a greater proportion of this radiation because of increase scatter and the lack of overlying other tissues to partially absorb some of the dose. This article describes the use of bismuth radioprotective garments to shield these radiosensitive areas while preserving the overall quality of the diagnostic image.

Population exposure to diagnostic use of ionizing radiation in The Netherlands

The use of ionizing radiation for diagnostic medical procedures and the exposure of the Dutch population to this radiation were assessed for 1998. The annual average effective dose from diagnostic medical exposures has increased by 26% to 0.59 mSv per capita since the last inventory of medical radiation exposure in the Netherlands a decade ago. The population-averaged effective dose comprises x-ray procedures in hospitals (87%), nuclear medicine examinations (11%), mammography screening (1.5%), and extramural dentistry (0.2%). The rise has resulted mainly from an increase in frequency and patient dose for CT examinations and from vascular radiology. The increase in the number of CT examinations leveled off in the mid-1990's. Medically exposed people were found to be significantly older than the general population. Based on age distribution alone, an "age reduction factor" for the risk coefficient of 0.64 was found to apply to the medically exposed group. More information on patient dose for the complete set of procedures should, according to this study, become available.

A survey of patient dose and image quality for computed tomography scanners in Wales

The main aim of the study was to assess the current level of radiation dose from computed tomography scanning in the NHS in Wales and to compare these results with previous studies in Wales and the UK. In addition, the relationship between patient dose and image quality was investigated by comparing mean patient dose calculations with image noise using two quality assurance (QA) phantoms. The results show that although the introduction of spiral scanners has reduced the dose per examination, the collective dose per scanner has actually increased. The results also highlight the potential for relating dose and objective measures of image quality to assist in the selection of scanning parameters to optimise dose without compromising image quality.

Radiation exposure and image quality in chest CT examinations

OBJECTIVE

The purpose of this study was to determine how changes in radiographic tube current affect patient dose and image quality in unenhanced chest CT examinations.

SUBJECTS AND METHODS

Ten sets of CT images were obtained from patients undergoing CT-guided chest biopsies. For each patient, six images of the same region were obtained at settings between 40 and 280 mAs. CT data were used to reconstruct tomographic sections with a field of view limited to the normal contralateral lung. Images were printed using lung and mediastinal image display settings. Image quality was determined by asking radiologists to assess the perceived level of mottle in CT images. Five chest radiologists ranked the relative image quality of six images. Patient effective doses were computed for chest CT examinations performed at each milliampere-second setting. Radiologists indicated whether any perceived improvement of image quality at the higher radiation exposures was worth the additional radiation dose.

RESULTS

The differences in quality of chest CT images generated at greater than or equal to 160 mAs were negligible. Reducing the radiographic technique factor below 160 mAs resulted in a perceptible reduction in image quality. Differences in CT image quality for radiographic techniques between 120 and 280 mAs were deemed to be insufficient to justify any additional patient exposure. However, the use of 40 mAs results in an inferior image quality that would justify increased patient exposure.

CONCLUSION

Radiographic techniques for unenhanced chest CT examinations can be reduced from 280 to 120 mAs without compromising image quality.

Radiation exposure in bone mineral density assessment

Osteoporosis is a systematic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue which leads to diminished biomechanical competence of the skeleton and low-trauma or atraumatic fractures. Due to increased awareness of the impact of osteoporosis on the elderly population, the use of bone densitometric techniques is becoming more widespread. Considerable progress has been made in the development of non-invasive methods for the assessment of the skeleton. While DXA and QCT are commonly used techniques, the popularity of other approaches such as RA, SXA and QUS is gaining grounds. QCT has an advantage over the other techniques in its ability to measure the true volumetric density of trabecular or cortical bone. We therefore present an overview of these current techniques for bone mineral density (BMD) measurements. In the second section we discuss the radiation doses incurred in BMD measurements by patients and methods for reducing patient and staff radiation exposure are given. Studies of radiation dose to patient from DXA confirms that patient dose is small (0.08-4.6 muSv) compared to that given by many other investigations involving ionizing radiation. Fan beam technology with increased resolution has resulted in increase patient dose radiation dose (6.7-31 muSv) but this is still relatively small. Carrying vertebral morphometry using DXA also incurs less radiation dose (< 60 muSv) than standard lateral radiographs QCT has radiation dose (25-360 muSv) comparable to simple radiological examination such as chest X-ray but lower than imaging CT. Radiation dose from other techniques such as RA and SXA are in the same order of magnitude as pencil beam DXA. For pencil beam DXA and SXA systems the time average dose to staff from scatter is very low even with the operator sitting as close as 1 m from the patient during measurement. However the scatter dose from fan beam DXA systems is considerable higher and approaches limits set by regulator bodies for occupational exposure.