Effective doses in radiology and diagnostic nuclear medicine: a catalog

Major radiodiagnostic imaging in pregnancy and the risk of childhood malignancy: a population-based cohort study in Ontario

BACKGROUND

The association between fetal exposure to major radiodiagnostic testing in pregnancy-computed tomography (CT) and radionuclide imaging-and the risk of childhood cancer is not established.

METHODS AND FINDINGS

We completed a population-based study of 1.8 million maternal-child pairs in the province of Ontario, from 1991 to 2008. We used Ontario's universal health care-linked administrative databases to identify all term obstetrical deliveries and newborn records, inpatient and outpatient major radiodiagnostic services, as well as all children with a malignancy after birth. There were 5,590 mothers exposed to major radiodiagnostic testing in pregnancy (3.0 per 1,000) and 1,829,927 mothers not exposed. The rate of radiodiagnostic testing increased from 1.1 to 6.3 per 1,000 pregnancies over the study period; about 73% of tests were CT scans. After a median duration of follow-up of 8.9 years, four childhood cancers arose in the exposed group (1.13 per 10,000 person-years) and 2,539 cancers in the unexposed group (1.56 per 10,000 person-years), a crude hazard ratio of 0.69 (95% confidence interval 0.26-1.82). After adjusting for maternal age, income quintile, urban status, and maternal cancer, as well as infant sex, chromosomal or congenital anomalies, and major radiodiagnostic test exposure after birth, the risk was essentially unchanged (hazard ratio 0.68, 95% confidence interval 0.25-1.80).

CONCLUSIONS

Although major radiodiagnostic testing is now performed in about 1 in 160 pregnancies in Ontario, the absolute annual risk of childhood malignancy following exposure in utero remains about 1 in 10,000. Since the upper confidence limit of the relative risk of malignancy may be as high as 1.8 times that of an unexposed pregnancy, we cannot exclude the possibility that fetal exposure to CT or radionuclide imaging is carcinogenic.

Imaging in pediatric patients: time to think again about surveillance

BACKGROUND

Despite concerns regarding ionizing radiation exposures from diagnostic imaging procedures in pediatric patients, many are deemed unavoidable or even mandated by treatment protocols. A prior review at our institution found patients with lymphoma had a higher median cumulative radiation exposure (191 mSv) versus other oncology subgroups (61 mSv).

PURPOSE

Estimations of cumulative diagnostic radiation exposures were tabulated for 5 years from the first diagnostic scan for 30 consecutive lymphoma patients diagnosed in 2001. Each individual imaging procedure was reviewed and classified as protocol mandated or discretionary (for disease surveillance, good patient care or radiologist request).

RESULTS

Almost all patients (28/29) received chemotherapy; one had surgery only. Individual cumulative radiation exposures ranged from 10 to 642 mSv. Over 5 years, 690 procedures were performed; 303 (44%) X-rays, 203 (29%) CTs, 157 (23%) radionucleotide, and 27 (4%) interventional procedures. Of these, 238 (34%) were protocol required and 452 (66%) discretionary (224 as part of good patient care for a co-morbid illness and 228 for evaluation of possible disease progression/surveillance). A total of 86/217 (40%) studies (including 43 CTs and 38 radionucleotide scans) were performed when the recurrence risk was low (>2 years off therapy).

CONCLUSIONS

The majority of ionizing radiation procedures in this lymphoma cohort were discretionary. Given the excellent outcome of this group and the long-term risks; rational use of discretionary surveillance procedures is necessary. Guidelines for the appropriate use of surveillance imaging based on probability of risk recurrence must be developed in order to minimize ionizing radiation exposure.

The radiation dose from a proposed measurement of arsenic and selenium in human skin

Dose measurements following 10 min irradiations with a portable x-ray fluorescence spectrometer composed of a miniature x-ray tube and a silicon PiN diode detector were performed using thermoluminescent dosimeters consisting of LiF:Mg,Ti chips of 3 mm diameter and 0.4 mm thickness. The table-top setup of the spectrometer was used for all measurements. The setup included a stainless steel lid which served as a radiation shield. Two rectangular polyethylene skin/soft tissue phantoms with two cylindrical plaster of Paris bone phantoms were used to study the effect of x-ray beam attenuation and backscatter on the measured dose. Eight different irradiation experiments were performed. The average dose rate values measured with TLD chips within a 1 x 1 cm(2) area were between 4.8 and 12.8 mGy min(-1). The equivalent dose for a 1 x 1 cm(2) skin area was estimated to be 13.2 mSv. The maximum measured dose rate values with a single TLD chip were between 7.5 and 25.1 mGy min(-1). The effective dose corresponding to a proposed arsenic/selenium skin measurement was estimated to be 0.13 microSv for a 2 min irradiation.

Radiation doses and cancer risks from breast imaging studies

PURPOSE

To compare radiation doses and lifetime attributable risks (LARs) of radiation-induced cancer incidence and mortality from breast imaging studies involving the use of ionizing radiation.

MATERIALS AND METHODS

Recent literature on radiation doses from radiologic procedures and organ doses from nuclear medicine procedures, along with Biologic Effects of Ionizing Radiation (BEIR) VII age-dependent risk data, is used to estimate LARs of radiation-induced cancer incidence and mortality from breast imaging studies involving ionizing radiation, including screen-film mammography, digital mammography, digital breast tomosynthesis, dedicated breast computed tomography, breast-specific gamma imaging (BSGI), and positron emission mammography (PEM).

RESULTS

Two-view digital mammography and screen-film mammography involve average mean glandular radiation doses of 3.7 and 4.7 mGy, respectively. According to BEIR VII data, these studies are associated, respectively, with LARs of fatal breast cancer of 1.3 and 1.7 cases per 100,000 women aged 40 years at exposure and less than one case per one million women aged 80 years at exposure. Annual screening digital or screen-film mammography performed in women aged 40-80 years is associated with an LAR of fatal breast cancer of 20-25 cases in 100,000. A single BSGI study involving a label-recommended dose of 740-1100 MBq (20-30 mCi) of technetium 99m-sestamibi is estimated to involve an LAR of fatal cancer that is 20-30 times that of digital mammography in women aged 40 years. A single PEM study involving a labeled dose of 370 MBq (10 mCi) of fluorine 18 fluorodeoxyglucose is estimated to involve an LAR of fatal cancer that is 23 times higher than that of digital mammography in women aged 40 years.

CONCLUSION

A single BSGI or PEM study is associated with a fatal radiation-induced cancer risk higher than or comparable to that of annual screening mammography in women aged 40-80 years.

In vivo tracking of transfused platelets for recovery and survival studies: an appraisal of labeling methods

The measurement of recovery and survival of platelets is an important decisive factor when 'new' platelet products have been developed. Recovery and survival measurements are mostly performed with radioactive-labeled platelets in healthy volunteers. This approach is required by the FDA for acceptance of platelet products that differ substantially in production or storage conditions from standard methods. However, due to regulatory obstacles, such radiolabeling studies are only carried out in designated institutes. Many countries do not require radioactive labeling studies in volunteers prior to accepting new products, and rather rely on surrogate tests. Also, the European guide to the preparation of blood components does not require this step. This paper reviews alternative, non-radioactive methods, which includes biotinylation of platelets, and discrimination of transfused platelets based on HLA discrepancy. The benefits and disadvantages of these methods will be discussed.

Cumulative imaging radiation exposure following breast-conservation therapy

INTRODUCTION

Radiation from medical imaging may induce cellular damage and increase the risk of cancer. While health care workers are restricted to an annual dose of 50 milliSieverts (mSv), the exposure to patients is not typically recorded. After breast-conservation therapy (BCT), patients are subjected to screening mammography, diagnostic breast imaging, and systemic surveillance imaging (SSI). Our objectives are to determine the cumulative radiation exposure of breast cancer survivors after completion of BCT, and to compare exposure levels in two historical cohorts. We also evaluated the indications of SSI.

METHODS

We performed a retrospective study of 68 patients with stage I or II breast cancer who received BCT in 1997 or 2002. Cumulative radiation exposure during follow-up from all imaging attributable to the breast cancer diagnosis was recorded, including both breast and non-breast imaging. The indications for SSI were recorded.

RESULTS

In the first 5 years after BCT, patients received a median annual dose of 0.92 mSv with no difference between the 1997 and 2002 cohorts. A median of 90% of radiation exposure was due to mammography. From 1997 to 2002, the percentage of patients receiving computed tomography (CT) scans increased. Additional SSI occurred in 65% of patients, with the majority of tests ordered in the asymptomatic patient. Patients with nodal positivity were more likely to receive SSI (p = 0.03).

CONCLUSIONS

In the first 5 years after BCT, annual radiation exposure due to imaging was low. However, it seems prudent to consider the risks of radiation exposure when ordering potentially low-yield screening studies in asymptomatic patients.

Evaluation of the patient with acute chest pain

The past decade has brought rapid advances in CT technology, which allows increasingly precise application to the study of coronary arteries and acute chest pain. The literature has expanded to lend quantifiable justification to the intuitive appeal of a rapid, reproducible, 3D study of the heart and vasculature. More complete analysis of efficacy and costs on broader populations will further refine our understanding of how best to implement what may become the new gold standard. Meanwhile, evolving technology promises to further challenge radiologists and clinicians to optimize approach and diagnosis to acute chest pain.

Effects of dose reduction on multi-detector computed tomographic images in evaluating the maxilla and mandible for pre-surgical implant planning: a cadaveric study

OBJECTIVE

To assess effects of dose reduction on image quality in evaluating maxilla and mandible for pre-surgical implant planning using cadavers.

MATERIALS AND METHODS

Six cadavers were used for the study using multi-detector computed tomography (CT) operated at 120 kV and the variable tube current of 80, 40, 20 and 10 mA. A slice thickness of 0.625 mm and pitch 1 were used. Multi-planar images perpendicular and parallel to dentitions were created. The images were evaluated by five oral radiologists in terms of visibility of the anatomical landmarks including alveolar crest, mandibular canal, floors of the maxillary sinus and nasal cavity, contours/cortical layer of jaw bones and the details of trabecular bone. Observers were asked to determine the quality of the images in comparison with 80 mA images based on the criteria: excellent, good, fair or non-diagnostic. The average scores of all observers were calculated for each specimen in all exposure conditions.

RESULTS

The 40 mA images could visualize such landmarks and were evaluated to be same or almost equivalent in quality to the 80 mA images. Even the 20 mA images could be accepted just for diagnostic purpose for implant with substantial deterioration of the image quality. The 10 mA images may not be accepted because of the obscured contour caused by image noise.

CONCLUSION

Significant dose reduction by lowering mA can be utilized for pre-surgical implant planning in multi-detector CT.

Cumulative exposure to ionizing radiation from diagnostic and therapeutic cardiac imaging procedures: a population-based analysis

OBJECTIVES

The purpose of this study was to describe radiation exposure from cardiac imaging procedures over time in a general population.

BACKGROUND

Cardiac imaging procedures frequently expose patients to ionizing radiation, but their contribution to effective doses of radiation in the general population is unknown.

METHODS

We used administrative claims to identify cardiac imaging procedures performed from 2005 to 2007 in 952,420 nonelderly insured adults in 5 U.S. health care markets. We estimated 3-year cumulative effective doses of radiation in millisieverts from these procedures We then calculated population-based annual rates of radiation exposure to effective doses < or =3 mSv/year (background level of radiation from natural sources), >3 to 20 mSv/year, or >20 mSv/year (upper annual limit for occupational exposure averaged over 5 years).

RESULTS

A total of 90,121 (9.5%) individuals underwent at least 1 cardiac imaging procedure using radiation. Among patients who underwent > or =1 cardiac imaging procedures, the mean cumulative effective dose over 3 years was 23.1 mSv (range 1.5 to 543.7 mSv). Myocardial perfusion imaging accounted for 74% of the cumulative effective dose. Overall, 47.8% of cardiac imaging procedures were performed in physician offices; this proportion was higher for myocardial perfusion imaging (74.8%) and cardiac computed tomography studies (76.5%). The annual population-based rate of receiving an effective dose of >3 to 20 mSv/year was 89.0 per 1,000; and 3.3 per 1,000 for cumulative doses >20 mSv/year. Annual effective doses increased with age and were generally higher among men.

CONCLUSIONS

Cardiac imaging procedures lead to substantial radiation exposure and effective doses for many patients in the U.S.

Cumulative exposure to ionizing radiation from diagnostic and therapeutic cardiac imaging procedures: a population-based analysis

OBJECTIVES

The purpose of this study was to describe radiation exposure from cardiac imaging procedures over time in a general population.

BACKGROUND

Cardiac imaging procedures frequently expose patients to ionizing radiation, but their contribution to effective doses of radiation in the general population is unknown.

METHODS

We used administrative claims to identify cardiac imaging procedures performed from 2005 to 2007 in 952,420 nonelderly insured adults in 5 U.S. health care markets. We estimated 3-year cumulative effective doses of radiation in millisieverts from these procedures We then calculated population-based annual rates of radiation exposure to effective doses < or =3 mSv/year (background level of radiation from natural sources), >3 to 20 mSv/year, or >20 mSv/year (upper annual limit for occupational exposure averaged over 5 years).

RESULTS

A total of 90,121 (9.5%) individuals underwent at least 1 cardiac imaging procedure using radiation. Among patients who underwent > or =1 cardiac imaging procedures, the mean cumulative effective dose over 3 years was 23.1 mSv (range 1.5 to 543.7 mSv). Myocardial perfusion imaging accounted for 74% of the cumulative effective dose. Overall, 47.8% of cardiac imaging procedures were performed in physician offices; this proportion was higher for myocardial perfusion imaging (74.8%) and cardiac computed tomography studies (76.5%). The annual population-based rate of receiving an effective dose of >3 to 20 mSv/year was 89.0 per 1,000; and 3.3 per 1,000 for cumulative doses >20 mSv/year. Annual effective doses increased with age and were generally higher among men.

CONCLUSIONS

Cardiac imaging procedures lead to substantial radiation exposure and effective doses for many patients in the U.S.

Radiation doses to ERCP patients are significantly lower with experienced endoscopists

BACKGROUND

Patients undergoing ERCP receive nontrivial doses of radiation, which may increase their risk of developing cancer, especially young patients. Radiation doses to patients during ERCP correlate closely with fluoroscopy time.

OBJECTIVE

The aim of this study was to determine whether endoscopist experience is associated with fluoroscopy time.

DESIGN

Retrospective analysis of a prospectively collected database.

SETTING

Data from 69 providers from 6 countries.

PATIENTS

9,052 entries of patients undergoing ERCP.

MAIN OUTCOME MEASUREMENTS

Percent difference in fluoroscopy time associated with endoscopist experience and fellow involvement.

RESULTS

For procedure types that require less fluoroscopy time, compared with endoscopists who performed > 200 ERCPs in the preceding year, endoscopists who performed <100 and 100 to 200 ERCPs had 104% (95% confidence interval [CI], 85%-124%) and 27% (95% CI, 20%-35%) increases in fluoroscopy time, respectively. Every 10 years of experience was associated with a 21% decrease in fluoroscopy time (95% CI, 19%-24%). For fluoroscopy-intense procedures, compared with endoscopists who performed >200 ERCPs in the preceding year, endoscopists who performed <100 and 100 to 200 ERCPs had 59% (95% CI, 39%-82%) and 11% (95% CI, 3%-20%) increases in fluoroscopy time, respectively. Every 10 years of experience was associated with a 20% decrease in fluoroscopy time (95% CI, 18%-24%).

LIMITATIONS

Database used is a voluntary reporting system, which may not be generalizable. Data is self-reported and was not verified for accuracy.

CONCLUSIONS

Fluoroscopy time is shorter when ERCP is performed by endoscopists with more years of performing ERCP and a greater number of ERCPs in the preceding year. These findings may have important ramifications for radiation-induced cancer risk.

Multidetector computed tomography with triple-bolus contrast medium administration protocol for preoperative anatomical and functional assessment of potential living renal donors

OBJECTIVE

To evaluate multidetector computed tomography (MDCT) with a triple-bolus contrast administration protocol for preoperative anatomical and functional assessment of living renal donors.

METHODS

Fifty-five potential living renal donors underwent MDCT of which 27 proceeded to donor nephrectomy. A triple-bolus contrast administration protocol was used for simultaneous acquisition of arterial, nephrographic, and excretory phases. MDCT images were independently reviewed in random order by two radiologists blinded to surgical anatomy findings. Diagnostic accuracy for anatomical variants was quantified by sensitivity and specificity. Differential renal function (DRF) was derived from MDCT for 54 patients and compared with technetium-99 m dimercaptosuccinic acid renography (Tc-99 m DMSA).

RESULTS

All triple-bolus MDCT examinations were technically adequate. Accessory renal arteries and veins were identified at surgery in 33% (n = 9/27) and 22% (n = 6/27) of donor kidneys. The mean difference between MDCT-derived DRF and DMSA was 0.8% (95% CI 0.1-1.6) with 95% limits of agreement of -4.6% (95% CI -3.3 to -5.9) to 6.3% (95% CI 5.0-7.6). MDCT delivered a mean (SD, range) radiation dose of 9.5 (3.6, 3.6-17.3) mSv.

CONCLUSION

MDCT with a triple-bolus contrast administration provides accurate anatomical and functional evaluation of living renal donors.

Optimizing parameters for flat-panel detector digital tomosynthesis

Digital tomosynthesis is a novel technique that allows easy and swift volume data acquisition in selected regions of the body. However, many radiologists and technologists are unfamiliar with this technique and the potential artifacts related to data acquisition. Digital tomosynthesis requires a single linear sweep of the x-ray tube assembly with corresponding tomographic reconstruction of large-area flat-panel detector radiographic data. Standard acquisition parameters include sweep angle, sweep direction, patient barrier-object distance, number of projections, and total radiation dose. Potential acquisition-related artifacts include blurring-ripple, ghost artifact-distortion, poor spatial resolution, image noise, and metallic artifact. A comprehensive understanding of the relationships between acquisition parameters and potential associated artifacts is critical to optimizing acquisition technique and avoiding misinterpretation of artifacts. Sweep direction should be chosen on the basis of the anatomy of interest and the purpose of the examination so as to reduce the influence of blurring-ripple, ghost artifact-distortion, and metallic artifact. Adjusting the sweep angle, number of projections, and radiation dose will optimize depth resolution, avoid ripple in the sections of interest, and reduce unnecessary radiation exposure without compromising image quality. Thus, it is important that the radiologist and technologist establish appropriate protocols for different examination types to allow optimal utilization of this novel imaging technique.

Leukocyte SPECT/CT for detecting infection of left-ventricular-assist devices: preliminary results

We report our experience with using integrated molecular and anatomic hybrid imaging to assess infection in patients who have a left-ventricular-assist device (LVAD).

METHODS

Thirteen (99m)Tc-exametazime-leukocyte planar and SPECT/CT scans were obtained for 8 consecutive patients who had an implanted LVAD. SPECT/CT was used to assess suspected device-related infections (n = 8) and to evaluate the efficiency of current antibiotic therapy (n = 5).

RESULTS

Device-related infection was seen on 8 of the 13 scans. SPECT/CT was positive for infection in all 8 patients, whereas planar scans were positive in 6 of 8. SPECT/CT provided relevant information on the extent of infection and its exact location in all patients. Additional distant infectious foci were demonstrated in 3 of 13 patients.

CONCLUSION

SPECT/CT led to an accurate diagnosis of LVAD-related infection, revealing both anatomic location and extent. This noninvasive approach could lead to improved therapeutic strategies.

Implications of ionizing radiation in the pediatric urology patient

PURPOSE

We reviewed the literature on the effects of ionizing radiation in pediatric patients, and discuss current recommendations and challenges facing radiologists and pediatric urologists.

MATERIALS AND METHODS

We performed a MEDLINE(R) search to identify articles evaluating the risk of ionizing radiation in pediatric patients. Particular attention was focused on computerized tomography. Standard radiography, fluoroscopy and nuclear imaging were also evaluated.

RESULTS

To date the literature relating radiation exposure to imaging has primarily focused on the role of the pediatrician and radiologist as decision makers. However, these imaging modalities are important to treat and monitor many conditions treated by the pediatric urologist. Conflicting reports have made clinical decision making and patient education challenging.

CONCLUSIONS

A lack of consensus on the risk of radiation exposure in pediatric patients increases the need for heightened awareness by the urologist requesting radiographic evaluation. Monitoring future studies is required to better understand the impact of radiation on children and ensure prompt implementation of appropriate guidelines for patient care.

Cost-effectiveness of coronary CT angiography in evaluation of patients without symptoms who have positive stress test results

OBJECTIVE

Patients without symptoms who have positive stress test results are often referred for diagnostic catheter angiography in an evaluation for coronary artery disease (CAD). The purpose of this study was to use decision tree analysis to determine the cost-effectiveness and radiation dose that would result from performing coronary CT angiography (CTA) before catheterization.

MATERIALS AND METHODS

A decision tree was constructed to compare the false-negative rates, false-positive rates, costs, and radiation exposure of direct referral of patients for cardiac catheterization with the values associated with performing coronary CTA before catheterization. We assumed that patients referred for coronary CTA proceed to catheterization only when significant disease is identified. Costs for coronary CTA and diagnostic catheterization were obtained from the 2009 physician Medicare fee schedule. Sensitivity, specificity, and radiation dose were obtained by literature review.

RESULTS

Cost reduction with coronary CTA depends on the prevalence of coronary artery disease, but overall costs are reduced as long as the prevalence is less than 85%. At a 50% prevalence of coronary artery disease, performing coronary CTA before cardiac catheterization results in an average cost saving of $789 per patient with a false-negative rate of 2.5% and average additional radiation exposure of 1-2 mSv.

CONCLUSION

Performing coronary CTA before cardiac catheterization is a cost-effective strategy in the care of patients without symptoms who have positive stress test results when the probability that the patient has significant coronary artery disease is less than 50%. The false-negative rate with this strategy compares favorably with the false-negative rate of stress testing. The use of coronary CTA in this role can avoid many unnecessary cardiac catheterization procedures.

Estimation of percentage body fat by dual-energy x-ray absorptiometry: evaluation by in vivo human elemental composition

Dual-energy x-ray absorptiometry (DXA) is widely applied for estimating body fat. The percentage of body mass as fat (%fat) is predicted from a DXA-estimated R(ST) value defined as the ratio of soft tissue attenuation at two photon energies (e.g., 40 keV and 70 keV). Theoretically, the R(ST) concept depends on the mass of each major element in the human body. The DXA R(ST) values, however, have never been fully evaluated by measured human elemental composition. The present investigation evaluated the DXA R(ST) value by the total body mass of 11 major elements and the DXA %fat by the five-component (5C) model, respectively. Six elements (i.e. C, N, Na, P, Cl and Ca) were measured by in vivo neutron activation analysis, and potassium (i.e. K) by whole-body (40)K counting in 27 healthy adults. Models were developed for predicting the total body mass of four additional elements (i.e. H, O, Mg and S). The elemental content of soft tissue, after correction for bone mineral elements, was used to predict the R(ST) values. The DXA R(ST) values were strongly associated with the R(ST) values predicted from elemental content (r = 0.976, P < 0.001), although there was a tendency for the elemental-predicted R(ST) to systematically exceed the DXA-measured R(ST) (mean +/- SD, 1.389 +/- 0.024 versus 1.341 +/- 0.024). DXA-estimated %fat was strongly associated with 5C %fat (24.4 +/- 12.0% versus 24.9 +/- 11.1%, r = 0.983, P < 0.001). DXA R(ST) is evaluated by in vivo elemental composition, and the present study supports the underlying physical concept and accuracy of the DXA method for estimating %fat.

Decision analytic model for evaluation of suspected coronary disease with stress testing and coronary CT angiography

RATIONALE AND OBJECTIVES

The aim of this study was to apply a decision analytic model for the evaluation of coronary artery disease (CAD) to define the optimal utilization of coronary computed tomographic angiography (cCTA) and stress testing.

MATERIALS AND METHODS

The model tested in this study assumes that CAD is evaluated with a stress test and/or cCTA and that a patient with positive evaluation results undergoes cardiac catheterization. On the basis of values of sensitivity, specificity, and radiation dose from the published literature and test costs from the Medicare fee schedule, a decision tree model was constructed as a function of disease prevalence.

RESULTS

The false-negative rate is lowest when cCTA is used as an isolated test. The false-positive rate is minimized when cCTA is used in combination with stress echocardiography. Effective radiation is minimized by use of stress electrocardiography or stress echocardiography alone or prior to cCTA. When the pretest probability of CAD is low, a strategy that uses stress echocardiography followed by cCTA minimizes the false-positive rate and effective radiation exposure, with relatively low imaging costs and with a false-negative rate only slightly higher than a strategy including stress myocardial scintigraphy. As the pretest probability of CAD increases above 20%, the false-negative rate of stress echocardiography followed by cCTA increases by >5% relative to cCTA alone.

CONCLUSION

Effective radiation dose and imaging costs for the workup of CAD may be minimized by an appropriate combination of stress testing and cCTA. A strategy that uses stress echocardiography followed by cCTA is most appropriate for the evaluation of low-risk patients with CAD with a pretest probability < 20%, while cCTA alone may be more appropriate in intermediate-risk patients.

CT colonography: perforation rates and potential radiation risks

Computed tomographic colonography (CTC) has emerged as an alternative screening tool for colorectal cancer due to the potential to provide good efficacy combined with greater acceptability than optical colonoscopy or fecal occult blood testing. However, some organizations have raised concerns about the potential harms, including perforation rates and radiation-related cancer risks, and have not recommended that it currently be used as a screening tool in the general population in the US. In this article the authors review the current evidence for these potential harms from CTC and compare them to the potential harms from the alternatives including colonoscopy and double-contrast barium enema.

Patient dose levels for seven different radiographic examination types

This study was carried out as a part of a comprehensive project to establish a national diagnostic reference level (NDRL), for the first time, in Saudi Arabia. Seven of the most common X-ray examinations (10 projections) were included. This study consisted of 200 patients who were referred for X-ray examinations at King Khalid University Hospital (KKUH). The selected X-ray examinations were skull (PA), kub (AP and LAT), ankle (AP and LAT), foot (AP/OBL and LAT/OBL), hib (AP and LAT) and sinuses paranasal (AP). Mean patient information and exposure parameters for these seven radiographic examinations were recorded at KKUH. Some of these radiographic examinations were compared with their corresponding values at other national places [Security Forces Hospital (SFH); King Abdulaziz City for Science and Technology (KACST)] in Saudi Arabia. We found that the patient mean dose values recorded at KKUH were varied from those recorded at other national places. Wide variations in patient dose arising from a specific type of X-ray examination at different national places suggests that significant reductions in patient dose would be possible without affecting image quality. Furthermore, variations in patient dose may emerge from the examination technique, clinical condition, radiologist skill, tube current, tube potential and focus to film distance. The data of this study will be useful for the formulation of NDRLs, and it is also provides local diagnostic reference levels for some diagnostic X-ray examinations at KKUH and other national places in Saudi Arabia.

Responsible use of computed tomography in the evaluation of coronary artery disease and chest pain

Many options are available to clinicians for the noninvasive evaluation of the cardiovascular system and patient concerns about chest discomfort. Cardiac computed tomography (CT) is a rapidly advancing field of noninvasive imaging. Computed tomography incorporates coronary artery calcium scoring, coronary angiography, ventricular functional analysis, and information about noncardiac thoracic anatomy. We searched the PubMed database and Google from inception to September 2009 for resources on the accuracy, risk, and predictive capacity of coronary artery calcium scoring and CT coronary angiography and have reviewed them herein. Cardiac CT provides diagnostic information comparable to echocardiography, nuclear myocardial perfusion imaging, positron emission tomography, and magnetic resonance imaging. A cardiac CT study can be completed in minutes. In patients with a nondiagnostic stress test result, cardiac CT can preclude the need for invasive angiography. Prognostic information portends excellent outcomes in patients with normal study results. Use of cardiac CT can reduce health care costs and length of emergency department stays for patients with chest pain. Cardiac CT examination provides clinically relevant information at a radiation dose similar to well-established technologies, such as nuclear myocardial perfusion imaging. Advances in technique can reduce radiation dose by 90%. With appropriate patient selection, cardiac CT can accurately diagnose heart disease, markedly decrease health care costs, and reliably predict clinical outcomes.

Effective dose to patients from chest examinations with tomosynthesis

Chest tomosynthesis, which refers to the principle of collecting low-dose projections of the chest at different angles and using these projections to reconstruct section images of the chest, is an imaging technique recently introduced to health care. The main purpose of the present work was to determine the average effective dose to patients from clinical use of chest tomosynthesis. Exposure data for two chest radiography laboratories with tomosynthesis option (Definium 8000 with VolumeRAD option, GE Healthcare, Chalfont St. Giles, UK) were registered for 20 patients with a weight between 60 and 80 kg (average weight of 70.2 kg). The recorded data were used in the Monte Carlo program PCXMC 2.0 (STUK-Radiation and Nuclear Safety Authority, Helsinki, Finland) to determine the average effective dose for each projection. The effective dose for the chest tomosynthesis examination, including a scout view and the tomosynthesis acquisition, was finally obtained by adding the effective doses from all projections. Using the weighting factors given in ICRP 103, the average effective dose for the examination was found to be 0.13 mSv, whereas the average effective dose for the conventional two-view chest radiography examination was 0.05 mSv. A conversion factor of 0.26 mSv Gy(-1) cm(-2) was found suitable for determining the effective dose from a VolumeRAD chest tomosynthesis examination from the total registered kerma-area product. In conclusion, the effective dose to a standard-sized patient (170 cm/70 kg) from a VolumeRAD chest tomosynthesis examination is ~2 % of an average chest CT and only two to three times the effective dose from the conventional two-view chest radiography examination.

Dose optimisation of double-contrast barium enema examinations

The purpose of the present work was to optimise the filtration and dose setting for double-contrast barium enema examinations using a Philips MultiDiagnost Eleva FD system. A phantom study was performed prior to a patient study. A CDRAD phantom was used in a study where copper and aluminium filtration, different detector doses and tube potentials were examined. The image quality was evaluated using the software CDRAD Analyser and the phantom dose was determined using the Monte Carlo-based software PCXMC. The original setting [100 % detector dose (660 nGy air kerma) and a total filtration of 3.5 mm Al, at 81 kVp] and two other settings identified by the phantom study (100 % detector dose and additional filtration of 1 mm Al and 0.2 mm Cu as well as 80 % detector dose and added filtration of 1 mm Al and 0.2 mm Cu) were included in the patient study. The patient study included 60 patients and up to 8 images from each patient. Six radiologists performed a visual grading characteristics study to evaluate the image quality. A four-step scale was used to judge the fulfillment of three image quality criteria. No overall statistical significant difference in image quality was found between the three settings (P > 0.05). The decrease in the effective dose for the settings in the patient study was 15 % when filtration was added and 34 % when both filtrations was added and detector dose was reduced. The study indicates that additional filtration of 1 mm Al and 0.2 mm Cu and a decrease in detector dose by 20 % from the original setting can be used in colon examinations with Philips MultiDiagnost Eleva FD to reduce the patient dose by 30 % without significantly affecting the image quality. For 20 exposures, this corresponds to a decrease in the effective dose from 1.6 to 1.1 mSv.

Predictors for the selection of patients for abdominal CT after blunt trauma: a proposal for a diagnostic algorithm

OBJECTIVE

To select parameters that can predict which patients should receive abdominal computed tomography (CT) after high-energy blunt trauma.

SUMMARY BACKGROUND DATA

Abdominal CT accurately detects injuries of the abdomen, pelvis, and lumbar spine, but has important disadvantages. More evidence for an appropriate patient selection for CT is required.

METHODS

A prospective observational study was performed on consecutive adult high-energy blunt trauma patients. All patients received primary and secondary surveys according to the advanced trauma life support, sonography (focused assessment with sonography for trauma [FAST]), conventional radiography (CR) of the chest, pelvis, and spine and routine abdominal CT. Parameters from prehospital information, physical examination, laboratory investigations, FAST, and CR were prospectively recorded for all patients. Independent predictors for the presence of > or =1 injuries on abdominal CT were determined using a multivariate logistic regression analysis.

RESULTS

A total of 1040 patients were included, 309 had injuries on abdominal CT. Nine parameters were independent predictors for injuries on CT: abnormal CR of the pelvis (odds ratio [OR], 46.8), lumbar spine (OR, 16.2), and chest (OR, 2.37), abnormal FAST (OR, 26.7), abnormalities in physical examination of the abdomen/pelvis (OR, 2.41) or lumbar spine (OR 2.53), base excess <-3 (OR, 2.39), systolic blood pressure <90 mm Hg (OR, 3.81), and long bone fractures (OR, 1.61). The prediction model based on these predictors resulted in a R of 0.60, a sensitivity of 97%, and a specificity of 33%. A diagnostic algorithm was subsequently proposed, which could reduce CT usage with 22% as compared with a routine use.

CONCLUSIONS

Based on parameters from physical examination, laboratory, FAST, and CR, we created a prediction model with a high sensitivity to select patients for abdominal CT after blunt trauma. A diagnostic algorithm was proposed.

Radiation safety in abdominal computed tomography

The rapid technological developments in computed tomography (CT) have enabled many new clinical applications in the abdominal region. Abdomen CT is considered as a high radiation dose examination due to the large number of radiosensitive organs in the field of view. CT radiation dose has received a lot of attention not only by the medical specialties and researchers, but also by patients and media. This article reviews the situation on radiation dose and risk and provides practical guidelines to effectively manage the radiation dose without losing the benefits and maintaining diagnostic confidence in CT procedures.

Scan time and patient dose for thoracic imaging in neonates and small children using axial volumetric 320-detector row CT compared to helical 64-, 32-, and 16- detector row CT acquisitions

BACKGROUND

Recently a 320-detector-row CT (MDCT) scanner has become available that allows axial volumetric scanning of a 16-cm-long range (50 cm field of view) in a single 0.35-s rotation. For imaging neonates and small children, volume scanning is potentially of great advantage as the entire scan range can be acquired in 0.35 s, which can reduce motion artefacts and may reduce the need for sedation in clinical CT imaging. Also, because there is no over-ranging associated with axial volumetric scanning, this may reduce patient radiation dose.

OBJECTIVE

To evaluate, by means of a phantom study, scan time and patient dose for thoracic imaging in neonates and small children by using axial cone-beam and helical fan-beam MDCT acquisitions.

MATERIALS AND METHODS

Paediatric imaging protocols were assessed for a 320-MDCT volumetric scanner (Aquilion ONE, Toshiba, Otawara, Japan). The 320-MDCT scanner allows for cone-beam acquisitions with coverage up to 160 mm, but it also allows for helical fan-beam acquisitions in 64-, 32-, or 16-MDCT modes. The acquisition configurations that were evaluated were 320 x 0.5 mm, 240 x 0.5 mm, and 160 x 0.5 mm for axial volumetric scanning, and 64 x 0.5 mm, 32 x 0.5 mm, and 16 x 0.5 mm for helical scanning. Dose assessment was performed for clinically relevant paediatric angiographic or chest/mediastinum acquisition protocols with tube voltages of 80 or 100 kVp and tube currents between 40 and 80 mA.

RESULTS

Scan time was 0.35 s for 320-MDCT acquisitions, scan times varied between 1.9 s and 8.3 s for helical acquisitions. Dose savings varying between 18% and 40% were achieved with axial volumetric scanning as compared to helical scanning (for 320- versus 64-MDCT at 160 mm and 80 kVp, and for 320- versus 16-MDCT at 80 mm and 100 kVp, respectively). Statistically significant reduction in radiation dose was found for axial 320-MDCT volumetric scanning compared to helical 64-, 32-, and 16-MDCT scanning.

CONCLUSION

Axial thoracic CT of neonates and small children with volumetric 320-MDCT can be performed between 5 and 24 times faster compared to helical scanning and can save patient dose.