Effects of radiation exposure from cardiac imaging: how good are the data?

Novel X-ray image noise reduction technology reduces patient radiation dose while maintaining image quality in coronary angiography

AIMS

The consequences of high radiation dose for patient and staff demand constant improvements in X-ray dose reduction technology. This study assessed non-inferiority of image quality and quantified patient dose reduction in interventional cardiology for an anatomy-specific optimised cine acquisition chain combined with advanced real-time image noise reduction algorithms referred to as 'study cine', compared with conventional angiography.

METHODS

Fifty patients underwent two coronary angiographic acquisitions: one with advanced image processing and optimised exposure system settings to enable dose reduction (study cine) and one with standard image processing and exposure settings (reference cine). The image sets of 39 patients (18 females, 21 males) were rated by six experienced independent reviewers, blinded to the patient and image characteristics. The image pairs were randomly presented. Overall 85 % of the study cine images were rated as better or equal quality compared with the reference cine (95 % CI 0.81-0.90). The median dose area product per frame decreased from 55 to 26 mGy.cm(2)/frame (53 % reduction, p < 0.001).

CONCLUSION

This study demonstrates that the novel X-ray imaging technology provides non-inferior image quality compared with conventional angiographic systems for interventional cardiology with a 53 % patient dose reduction.

Long-term strategies support autonomy in radiation safety in invasive cardiology

BACKGROUND AND PURPOSE

Despite comprehensive radiation safety programs, radiation exposure in invasive cardiology remains considerable. According to the 2013 German Registry, median in-hospital dose area products (DAP) amount to 19.8Gycm(2) for invasive coronary angiography (CA). We analyzed long-term radiation-reducing strategies for an experienced interventionalist from 1997 to 2012, for the target intervention of CA.

METHODS

Among representative cohorts, we evaluated iterative alterations in collimation, time on beam, pulse rates, detector entrance doses, and angulations on the basis of DAP, radiographic DAP(R) and fluoroscopic DAP(F), the respective times on beam, and the number of frames and runs.

RESULTS

Patients' median overall DAP decreased from 33.8Gycm(2) at baseline to 2.4 and 0.6Gycm(2) for CA in conventional (C) and electrocardiogram-gated (E) modes - one diastolic radiographic frame per heartbeat at 77% of the RR interval. Further median dose parameters for CA at baseline and finally in C/E mode were as follows: effective dose (6.76-0.48/0.13mSv), radiography time (43.8-12.9/21.7s), frames (548-105/25), frames/run (41.3-14.4/3.4), DAP(R)/frame (42.6-16.6/12.6mGycm(2)), DAP(R)/s (532-130/13.8mGycm(2)/s), fluoroscopy time (195-120/119s), DAP(F)/pulse (2.0-1.1/0.8mGycm(2)), and DAP(F)/s (48.9-4.4/3.1mGycm(2)/s).

CONCLUSIONS

Our data highlight the efficacy of various radiation-reducing strategies by autonomous control and iterative training in radiation safety toward submillisievert levels for CA, and define realizable benchmarks for comparison with the performance data of any individual.

Feasibility of real-time magnetic resonance imaging-guided endomyocardial biopsies: An in-vitro study

AIM: To investigate if magnetic resonance (MR)-guided biopsy can improve the performance and safety of such procedures.

METHODS: A novel MR-compatible bioptome was evaluated in a series of in-vitro experiments in a 1.5T magnetic resonance imaging (MRI) system. The bioptome was inserted into explanted porcine and bovine hearts under real-time MR-guidance employing a steady state free precession sequence. The artifact produced by the metal element at the tip and the signal voids caused by the bioptome were visually tracked for navigation and allowed its constant and precise localization.

RESULTS: Cardiac structural elements and the target regions for the biopsy were clearly visible. Our method allowed a significantly better spatial visualization of the bioptoms tip compared to conventional X-ray guidance. The specific device design of the bioptome avoided inducible currents and therefore subsequent heating. The novel MR-compatible bioptome provided a superior cardiovascular magnetic resonance (imaging) soft-tissue visualization for MR-guided myocardial biopsies. Not at least the use of MRI guidance for endomyocardial biopsies completely avoided radiation exposure for both patients and interventionalists.

CONCLUSION: MRI-guided endomyocardial biopsies provide a better than conventional X-ray guided navigation and could therefore improve the specificity and reproducibility of cardiac biopsies in future studies.

Clinical application of 'Justification' and 'Optimization' principle of ALARA in pediatric CT imaging: "How many children can be protected from unnecessary radiation?"

RATIONALE AND OBJECTIVES

Practice of ALARA (as low as reasonably achievable) principle in the developed world is currently well established. However, there is striking lack of published data regarding such experience in the developing countries. Therefore, the goal of this study is to prospectively evaluate CT request forms to assess how many children could be protected from harmful radiation exposure if 'Justification' and 'Optimization' principles of ALARA are applied before obtaining CT imaging in a developing country. This can save children from potential radiation risks including development of brain cancer and leukemia.

MATERIAL AND METHODS

Consecutive CT request forms over a six month study period (May 16, 2013 to November 15, 2013) in a tertiary pediatric children's hospital in India were prospectively reviewed by two pediatric radiologists before obtaining CT imaging. First, 'Justification' of CT was evaluated and then 'Optimization' was applied for evaluation of appropriateness of the requested CT studies. The number (and percentage) of CT studies avoided by applying 'Justification' and 'Optimization' principle of ALARA were calculated. The difference in number of declined and optimized CT requests between CT requests from inpatient and outpatient departments was compared using Chi-Square test.

RESULTS

A total of 1302 consecutive CT request forms were received during the study period. Some of the request forms (n=86; 6.61%) had requests for more than one (multiple) anatomical regions, hence, a total of 1392 different anatomical CT requests were received. Based on evaluation of the CT request forms for 'Justification' and 'Optimization' principle of ALARA by pediatric radiology reviewers, 111 individual anatomic part CT requests from 105 pediatric patients were avoided. Therefore, 8.06% (105 out of 1302 pediatric patients) were protected from unnecessary or additional radiation exposure.The rates of declined or optimized CT requests from inpatient department was significantly higher than that from outpatient departments (p<0.05).

CONCLUSIONS

A substantial number of pediatric patients, particularly coming from outpatient departments, can be protected from unnecessary or additional radiation exposure from CT imaging when 'Justification' and 'Optimization' principle of ALARA are applied before obtaining CT imaging in a developing country.

Radiation doses from fluoroscopically guided cardiac catheterization procedures in children and young adults in the United Kingdom: a multicentre study

OBJECTIVE

To gather data on radiation doses from fluoroscopically guided cardiac catheterization procedures in patients aged under 22 years at multiple centres and over a prolonged period in the UK. To evaluate and explain variation in doses. To estimate patient-specific organ doses and allow for possible future epidemiological analysis of associated cancer risks.

METHODS

Patient-specific data including kerma area product and screening times from 10,257 procedures carried out on 7726 patients at 3 UK hospitals from 1994 until 2013 were collected. Organ doses were estimated from these data using a dedicated dosimetry system based on Monte Carlo computer simulations.

RESULTS

Radiation doses from these procedures have fallen significantly over the past two decades. The organs receiving the highest doses per procedure were the lungs (median across whole cohort, 20.5 mSv), heart (19.7 mSv) and breasts (13.1 mSv). Median cumulative doses, taking into account multiple procedures, were 23.2, 22.2 and 16.7 mSv for these organs, respectively. Bone marrow doses were relatively low (median per procedure, 3.2 mSv; cumulative, 3.6 mSv).

CONCLUSION

Most modern cardiac catheterizations in children are moderately low-dose procedures. Technological advances appear to be the single most important factor in the fall in doses. Patients undergoing heart transplants undergo the most procedures. An epidemiological assessment of cancer risks following these procedures may be possible, especially using older data when doses were higher.

ADVANCES IN KNOWLEDGE

This is the first large-scale, patient-specific assessment of organ doses from these procedures in a young population.

Approaches to reducing radiation dose from radionuclide myocardial perfusion imaging

Radionuclide myocardial perfusion imaging (MPI) plays a vital role in the evaluation and management of patients with coronary artery disease. However, because of a steep growth in MPI in the mid 2000s, concerns about inappropriate use of MPI and imaging-related radiation exposure increased. In response, the professional societies developed appropriate-use criteria for MPI. Simultaneously, novel technology, image-reconstruction software for traditional scanners, and dedicated cardiac scanners emerged and facilitated the performance of MPI with low-dose and ultra-low-dose radiotracers. This paper provides a practical approach to performing low-radiation-dose MPI using traditional and novel technologies.

The diagnosis of CAD in women: addressing the unmet need - a report from the national expert roundtable meeting

A multistakeholder panel comprising experts in the fields of clinical cardiology, medical technology innovation, women's health research and policy analysis, personalized medicine, payers (including self-insured employers), patient advocacy, and health economics was convened at the Heart House in Washington, DC. The following points emerged as key concepts: (1) Diagnostic challenges in the evaluation of women with symptoms suggestive of obstructive coronary artery disease (CAD) result from: (a) presentation with atypical symptoms and lower pretest probability of disease compared to men, (b) fatty tissue and breast tissue attenuation on cardiac imaging leading to false positive findings, and (c) the presence of microvascular CAD. (2) Diagnostic challenges lead to both over-testing of low-risk women and under-testing of high-risk women. (3) Efforts should be directed toward increasing clinician, clinical professional society, and consumer awareness and understanding of sex-specific differences between men and women in the pathophysiology of CAD. (4) Multiple health care stakeholders should be made aware of new advances in genomic approaches to address the challenges of diagnosing obstructive CAD; specifically, the Corus CAD gene expression test, which was shown to have high sensitivity and negative predictive value in a recent clinical trial. As such, it has promise as a tool to help clinicians to rule out obstructive CAD as a cause of a patient's symptoms. (Population Health Management 2015;18:86-92).

Nuclear medicine in the management of patients with heart failure: guidance from an expert panel of the International Atomic Energy Agency (IAEA)

Heart failure is increasing worldwide at epidemic proportions, resulting in considerable disability, mortality, and increase in healthcare costs. Gated myocardial perfusion single photon emission computed tomography or PET imaging is the most prominent imaging modality capable of providing information on global and regional ventricular function, the presence of intraventricular synchronism, myocardial perfusion, and viability on the same test. In addition, ¹²³I-mIBG scintigraphy is the only imaging technique approved by various regulatory agencies able to provide information regarding the adrenergic function of the heart. Therefore, both myocardial perfusion and adrenergic imaging are useful tools in the workup and management of heart failure patients. This guide is intended to reinforce the information on the use of nuclear cardiology techniques for the assessment of heart failure and associated myocardial disease.

Myocardial perfusion imaging determination using an appropriate use smartphone application

BACKGROUND

Inappropriate cardiac imaging has been a significant cost concern and cause of radiation burden to patients.

OBJECTIVE

To assess if a smartphone application (app) based on 2009 Appropriate Use Criteria (AUC) for Cardiac Radionuclide Imaging published by American College of Cardiology would be feasible at the point of order.

METHODS

We evaluated stress myocardial perfusion imaging (MPI) (N = 403) (mean age = 62.23 years; 47.89% males) over a 4 month period using a smartphone app to determine whether the study ordered was Appropriate, Inappropriate, or Uncertain per 2009 AUC. We also monitored the time needed to use the app to determine the level of appropriateness of each stress MPI. The results of the stress MPI were noted.

RESULTS

Of the 403 stress MPIs evaluated, 267 (66.25%) were noted to be Appropriate, 118 (29.28%) were Inappropriate, and 13 (3.23%) were Uncertain, per AUC; 5 (1.25%) remained unclassified. Average time needed to use the app to assess each stress MPI for appropriateness was noted to be 44 (±9) seconds. Non-teaching physicians ordered 70 (38.89%) inappropriate stress MPIs as compared to 20 (23.53%) ordered by physicians on resident teaching service, and 28 (23.33%) by cardiologists (P = .0045). Among inappropriately ordered stress MPIs, 87 (42.65%) were ordered in females as compared to 31 (17.13%) in males (P < .0001). 70 (26.22%) stress MPIs among appropriately ordered were abnormal (reversible ischemia or fixed perfusion defect) as compared to 15 (12.17%) among inappropriately ordered stress MPIs (P = .0032).

CONCLUSION

A free and convenient smartphone app provides an easy-to-use tool to assist physicians in determining the level of appropriateness of stress MPI in a time- and cost-effective manner at the point of order. The smartphone app may have potential to promote the usage of the AUC and possibly aid reduction of healthcare cost and ionizing radiation burden.

Multicenter long-term validation of a minicourse in radiation-reducing techniques in the catheterization laboratory

Patient radiation exposure in invasive cardiology is considerable. We aimed to investigate, in a multicenter field study, the long-term efficacy of an educational 90-minute workshop in cardiac invasive techniques with reduced irradiation. Before and at a median period of 2.5 months and 2.0 years after the minicourse (periods I, II, and III, respectively) at 5 German cardiac centers, 18 interventionalists documented various radiation parameters for 10 coronary angiographies. The median patient dose area product (DAP) for periods I, II, and III amounted to 26.6, 12.2, and 9.6 Gy × cm(2), respectively. The short-term and long-term effects were related to shorter median fluoroscopy times (180, 138, and 114 seconds), fewer radiographic frames (745, 553, and 417) because of fewer (11, 11, and 10) and shorter (64, 52, and 44 frames/run) runs, consistent collimation, and restriction to an adequate image quality; both radiographic DAP/frame (27.7, 17.3, and 18.4 mGy × cm(2)) and fluoroscopic DAP/second (26.6, 12.9, and 14.9 mGy × cm(2)) decreased significantly. Multivariate analysis over time indicated increasing efficacy of the minicourse itself (-55% and -64%) and minor influence of interventionist experience (-4% and -3% per 1,000 coronary angiographies, performed lifelong until the minicourse and until period III). In conclusion, autonomous self-surveillance of various dose parameters and feedback on individual radiation safety efforts supported the efficacy of a 90-minute course program toward long-lasting and ongoing patient dose reduction.

Are Risks From Medical Imaging Still too Small to Be Observed or Nonexistent?

Several radiation-related professional societies have concluded that carcinogenic risks associated with doses below 50-100 mSv are either too small to be detected, or are nonexistent. This is especially important in the context of doses from medical imaging. Radiation exposure to the public from medical imaging procedures is rising around the world, primarily due to increased utilization of computed tomography. Professional societies and advisory bodies consistently recommend against multiplying small doses by large populations to predict excess radiation-induced cancers, in large part because of the potential for sensational claims of health impacts which do not adequately take the associated uncertainties into account. Nonetheless, numerous articles have predicted thousands of future cancers as a result of CT scanning, and this has generated considerable concern among patients and parents. In addition, some authors claim that we now have direct epidemiological evidence of carcinogenic risks from medical imaging. This paper critically examines such claims, and concludes that the evidence cited does not provide direct evidence of low-dose carcinogenicity. These claims themselves have adverse public health impacts by frightening the public away from medically justified exams. It is time for the medical and scientific communities to be more assertive in responding to sensational claims of health risks.

Standardization and optimization of CT protocols to achieve low dose

The increase in radiation exposure due to CT scans has been of growing concern in recent years. CT scanners differ in their capabilities, and various indications require unique protocols, but there remains room for standardization and optimization. In this paper, the authors summarize approaches to reduce dose, as discussed in lectures constituting the first session of the 2013 UCSF Virtual Symposium on Radiation Safety and Computed Tomography. The experience of scanning at low dose in different body regions, for both diagnostic and interventional CT procedures, is addressed. An essential primary step is justifying the medical need for each scan. General guiding principles for reducing dose include tailoring a scan to a patient, minimizing scan length, use of tube current modulation and minimizing tube current, minimizing tube potential, iterative reconstruction, and periodic review of CT studies. Organized efforts for standardization have been spearheaded by professional societies such as the American Association of Physicists in Medicine. Finally, all team members should demonstrate an awareness of the importance of minimizing dose.

ECG-gated coronary angiography enables submillisievert imaging in invasive cardiology

BACKGROUND

The median dose area products (DAP) and effective doses (ED) of patients arising from coronary angiography (CA) are considerable: According the 2013 National German Registry, they amount to 19.8 Gy × cm(2) and 4.0 mSv, respectively.

METHODS

We investigated the feasibility of prospective electrocardiogram (ECG)-gated coronary angiography (CA)-a novel technique in invasive cardiology-with respect to possible reduction in irradiation effects. Instead of universally fix-rated radiographic acquisition within 7.5-15 frames/s, one single frame/heartbeat was triggered toward the diastolic moment immediately before atrial contraction (77 % of ECG-RR interval) most likely to provide motion-free and hence optimized resolution of the coronary tree. For 200 patients (body mass index 27.8 kg/m(2), age 67.5 years, male 55 %, 68 bpm) undergoing ECG-gated CA, we measured various median (interquartile range) parameters for radiation exposure.

RESULTS

The total DAP was 0.64 (0.46-1.00), radiographic fraction was 0.30 (0.19-0.43), and fluoroscopic fraction was 0.35 (0.21-0.57) Gy × cm(2). Radiographic imaging occurred within 21.7 s (17.1-26.3), with 25 frames (20-30) over the course of 7 runs (6-8). Fluoroscopy time was 119 s (94-141). Radiographic DAP was 12.6 mGy × cm(2)/frame and 13.8 mGy × cm(2)/s. Fluoroscopic DAP was 0.8 mGy × cm(2)/pulse and 3.1 mGy × cm(2)/s. Patient reference point air kerma was 17.0 mGy (11.1-28.1) and contrast volume was 70 ml (60-85).

CONCLUSION

In conclusion, invasive ECG-gated coronary imaging is feasible in clinical routine and enables patient EDs of approx. 3 % of typical values in invasive cardiology: 0.13 mSv (0.09-0.20).

Approaches to enhancing radiation safety in cardiovascular imaging: a scientific statement from the American Heart Association

Education, justification, and optimization are the cornerstones to enhancing the radiation safety of medical imaging. Education regarding the benefits and risks of imaging and the principles of radiation safety is required for all clinicians in order for them to be able to use imaging optimally. Empowering patients with knowledge of the benefits and risks of imaging will facilitate their meaningful participation in decisions related to their health care, which is necessary to achieve patient-centered care. Limiting the use of imaging to appropriate clinical indications can ensure that the benefits of imaging outweigh any potential risks. Finally, the continually expanding repertoire of techniques that allow high-quality imaging with lower radiation exposure should be used when available to achieve safer imaging. The implementation of these strategies in practice is necessary to achieve high-quality, patient-centered imaging and will require a shared effort and investment by all stakeholders, including physicians, patients, national scientific and educational organizations, politicians, and industry.

Automatic detection and quantification of the Agatston coronary artery calcium score on contrast computed tomography angiography

Potentially, Agatston coronary artery calcium (CAC) score could be calculated on contrast computed tomography coronary angiography (CTA). This will make a separate non-contrast CT scan superfluous. This study aims to assess the performance of a novel fully automatic algorithm to detect and quantify the Agatston CAC score in contrast CTA images. From a clinical registry, 20 patients were randomly selected for each CAC category (i.e. 0, 1-99, 100-399, 400-999, ≥1,000). The Agatston CAC score on non-contrast CT was calculated manually, while the novel algorithm was used to automatically detect and quantify Agatston CAC score in contrast CTA images. The resulting Agatston CAC scores were validated against the non-contrast images. A total of 100 patients (60 ± 11 years, 63 men) were included. The median CAC score on non-contrast CT was 145 (IQR 5-760), whereas the contrast CTA CAC score was 170 (IQR 23-594) (P = 0.004). The automatically computed CAC score showed a high correlation (R = 0.949; P < 0.001) and intra-class correlation (R = 0.863; P < 0.001) with non-contrast CT CAC score. Moreover, agreement within CAC categories was good (κ 0.588). Fully automatic detection of Agatston CAC score on contrast CTA is feasible and showed high correlation with non-contrast CT CAC score. This could imply a radiation dose reduction and time saving by omitting the non-contrast scan.

Comparison of image quality, myocardial perfusion, and left ventricular function between standard imaging and single-injection ultra-low-dose imaging using a high-efficiency SPECT camera: the MILLISIEVERT study

SPECT myocardial perfusion imaging plays a central role in coronary artery disease diagnosis, but concerns exist regarding its radiation burden. Compared with standard Anger SPECT (A-SPECT) cameras, new high-efficiency (HE) cameras with specialized collimators and solid-state cadmium-zinc-telluride detectors offer potential to maintain image quality (IQ), while reducing administered activity and thus radiation dose to patients. No previous study has compared IQ, interpretation, total perfusion deficit (TPD), or ejection fraction (EF) in patients receiving both ultra-low-dose (ULD) imaging on an HE SPECT camera and standard low-dose (SLD) A-SPECT imaging.

METHODS

We compared ULD HE SPECT with SLD A-SPECT imaging by dividing the rest dose in 101 patients at 3 sites scheduled to undergo clinical A-SPECT myocardial perfusion imaging using a same day rest-stress (99m)Tc protocol. Patients underwent HE SPECT imaging after an initial approximately 130-MBq (3.5 mCi) dose and SLD-A-SPECT imaging after the remainder of the planned dose. Images were scored visually by 2 masked readers for IQ and summed rest score. TPD and EF were assessed quantitatively.

RESULTS

Mean activity was 134 MBq (3.62 mCi) for ULD HE SPECT (effective dose, 1.15 mSv) and 278 MBq (7.50 mCi, 2.39 mSv) for SLD A-SPECT. Overall IQ was superior for ULD HE SPECT (P < 0.0001), with twice as many studies graded excellent quality. Extracardiac activity and overall perfusion assessment were similar. Between-method correlations were high for summed rest score (r = 0.87), TPD (r = 0.91), and EF (r = 0.88).

CONCLUSION

ULD HE SPECT rest imaging correlates highly with SLD A-SPECT. It has improved image quality, comparable extracardiac activity, and achieves radiation dose reduction to 1 mSv for a single injection.

Closing in on the K edge: coronary CT angiography at 100, 80, and 70 kV-initial comparison of a second- versus a third-generation dual-source CT system

PURPOSE

To prospectively evaluate radiation and contrast medium requirements for performing high-pitch coronary computed tomographic (CT) angiography at 70 kV using a third-generation dual-source CT system in comparison to a second-generation dual-source CT system.

MATERIALS AND METHODS

All patients gave informed consent for this institutional review board-approved study. Forty-five patients (median age, 52 years; 27 men) were imaged in high-pitch mode with a third-generation dual-source CT system at 70 kV (n = 15) or with a second-generation dual-source CT system at 80 or 100 kV (n = 15 for each). Tube voltage was based on body mass index: 80 or 70 kV for less than 26 kg/m(2) versus 100 kV for 26-30 kg/m(2). For the 80- and 100-kV protocols, 80 mL of contrast material was injected, versus 45 mL for the 70-kV protocol. Data were reconstructed by using a second-generation iterative reconstruction algorithm for second-generation dual-source CT and a recently introduced third-generation iterative reconstruction algorithm for third-generation dual-source CT. Objective image quality was measured for various regions of interest, and subjective image quality was evaluated with a five-point Likert scale.

RESULTS

The signal-to-noise ratio of the coronary CT angiography studies acquired with 70 kV was significantly higher (70 kV: 14.3-17.6 vs 80 kV: 7.1-12.9 vs 100 kV: 9.8-12.9; P < .0497) than those acquired with the other two protocols for all coronary arteries. Qualitative image quality analyses revealed no significant differences between the three CT angiography protocols (median score, 5; P > .05). The mean effective dose was 75% and 108% higher (0.92 mSv ± 0.3 [standard deviation] and 0.78 mSv ± 0.2 vs 0.44 mSv ± 0.1; P < .0001), respectively, for the 80- and 100-kV CT angiography protocols than for the 70-kV CT angiography protocol.

CONCLUSION

In nonobese patients, third-generation high-pitch coronary dual-source CT angiography at 70 kV results in robust image quality for studying the coronary arteries, at significantly reduced radiation dose (0.44 mSv) and contrast medium volume (45 mL), thus enabling substantial radiation dose and contrast medium savings as compared with second-generation dual-source CT.

Low-Dose Radiation Risks of Computerized Tomography and Cone Beam Computerized Tomography: Reducing the Fear and Controversy

Regulations for protecting humans against stochastic biological effects from ionizing radiation are based on the linear no-threshold (LNT) risk assessment model, which states that any amount of radiation exposure may lead to cancer in a population. Based on the LNT model, risk from low-dose radiation increases linearly with increasing doses of radiation. Imaging procedures in medicine and dentistry are an important source of low-dose ionizing radiation. The increased use of computerized tomography (CT) and cone beam computerized tomography (CBCT) has raised health concerns regarding exposure to low-dose ionizing radiation. In oral and maxillofacial surgery and implant dentistry, CBCT is now at the forefront of this controversy. Although caution has been expressed, there have been no direct studies linking radiation exposure from CT and CBCT used in dental imaging with cancer induction. This article describes the concerns about radiation exposure in dental imaging regarding the use of CT.

Prehospital use of cervical collars in trauma patients: a critical review

The cervical collar has been routinely used for trauma patients for more than 30 years and is a hallmark of state-of-the-art prehospital trauma care. However, the existing evidence for this practice is limited: Randomized, controlled trials are largely missing, and there are uncertain effects on mortality, neurological injury, and spinal stability. Even more concerning, there is a growing body of evidence and opinion against the use of collars. It has been argued that collars cause more harm than good, and that we should simply stop using them. In this critical review, we discuss the pros and cons of collar use in trauma patients and reflect on how we can move our clinical practice forward. Conclusively, we propose a safe, effective strategy for prehospital spinal immobilization that does not include routine use of collars.

Using the coronary artery calcium score to guide statin therapy: a cost-effectiveness analysis

BACKGROUND

The coronary artery calcium (CAC) score predicts future coronary heart disease (CHD) events and could be used to guide primary prevention interventions, but CAC measurement has costs and exposes patients to low-dose radiation.

METHODS AND RESULTS

We estimated the cost-effectiveness of measuring CAC and prescribing statin therapy based on the resulting score under a range of assumptions using an established model enhanced with CAC distribution and risk estimates from the Multi-Ethnic Study of Atherosclerosis. Ten years of statin treatment for 10,000 55-year-old women with high cholesterol (10-year CHD risk, 7.5%) was projected to prevent 32 myocardial infarctions, cause 70 cases of statin-induced myopathy, and add 1108 years to total life expectancy. Measuring CAC and targeting statin treatment to the 2500 women with CAC>0 would provide 45% of the benefit (+501 life-years), but CAC measurement would cost $2.25 million and cause 9 radiation-induced cancers. Treat all was preferable to CAC screening in this scenario and across a broad range of other scenarios (CHD risk, 2.5%-15%) when statin assumptions were favorable ($0.13 per pill and no quality of life penalty). When statin assumptions were less favorable ($1.00 per pill and disutility=0.00384), CAC screening with statin treatment for persons with CAC>0 was cost-effective (<$50 000 per quality-adjusted life-year) in this scenario, in 55-year-old men with CHD risk 7.5%, and in other intermediate risk scenarios (CHD risk, 5%-10%). Our results were critically sensitive to statin cost and disutility and relatively robust to other assumptions. Alternate CAC treatment thresholds (>100 or >300) were generally not cost-effective.

CONCLUSIONS

CAC testing in intermediate risk patients can be cost-effective but only if statins are costly or significantly affect quality of life.

Latest-generation catheterization systems enable invasive submillisievert coronary angiography

BACKGROUND

The radiation risk of patients undergoing invasive cardiology remains considerable and includes skin injuries and cancer. To date, submillisievert coronary angiography has not been considered feasible.

PATIENTS AND METHODS

In 2011, we compared results from 100 consecutive patients undergoing elective coronary angiography using the latest-generation flat-panel angiography system (FPS) with results from examinations by the same operator using 106 historic controls with a conventional image-intensifier system (IIS) that was new in 2002.

RESULTS

The median patient exposure parameters were measured as follows: dose-area product (DAP) associated with radiographic cine acquisitions (DAP(R)) and fluoroscopy (DAP(F)) scenes, radiographic frames and runs, and cumulative exposure times for radiography and fluoroscopy. On the FPS as compared to the traditional IIS, radiographic detector entrance dose levels were reduced from 164 to 80 nGy/frame and pulse rates were lowered from 12.5/s to 7.5/s during radiography and from 25/s to 4/s during fluoroscopy. The cardiologist's performance patterns remained comparable over the years: fluoroscopy time was constant and radiography time even slightly increased. Overall patient DAP decreased from 7.0 to 2.4 Gy × cm(2); DAP(R), from 4.2 to 1.7 Gy × cm(2); and DAP(F), from 2.8 to 0.6 Gy × cm(2). Time-adjusted DAP(R)/s decreased from 436 to 130 mGy × cm(2) and DAP(F)/s, from 21.6 to 4.4 mGy × cm(2). Cumulative patient skin dose with the FPS amounted to 67 mGy, and the median (interquartile range) of effective dose was 0.5 (0.3 … 0.7) mSv.

CONCLUSION

Consistent application of radiation-reducing techniques with the latest-generation flat-panel systems enables submillisievert coronary angiography in invasive cardiology.

Comparison of cancer risk associated with low-dose ionizing radiation from cardiac imaging and therapeutic procedures after acute myocardial infarction in women versus men

Patients with cardiovascular disease are increasingly exposed to low-dose ionizing radiation (LDIR) from diagnostic and therapeutic procedures. Previous studies have suggested that the malignancy risk associated with LDIR may be greatest in women and in young patients. We sought to compare the effect of LDIR on incident cancer across gender and age strata in a population-based cohort of patients with myocardial infarction (MI). All initially cancer-free patients with MI from 1996 to 2006 were identified in a province-wide administrative database. Procedure-specific LDIR dose estimates were used to generate a cumulative cardiac LDIR exposure variable. Time-dependent multivariate Cox regression was used to determine the relation between cardiac LDIR and incident cancer. A time-lag covariate of 3 years was used wherein a de novo cancer could only be attributed to LDIR incurred at least 3 years earlier. The effect of age and gender on LDIR-associated risk of cancer was evaluated with stratified models and the addition of interaction terms. The study cohort consisted of 56,606 men and 26,255 women. For each millisievert of cardiac LDIR, women were more likely to develop a cancer (hazard ratio 1.005, 95% confidence interval 1.002 to 1.008) than men (hazard ratio 1.002, 95% confidence interval 1.001 to 1.004) after adjusting for age, noncardiac LDIR, and covariates (p for interaction = 0.014). Contrarily, over the range studied (predominantly patients aged >50 years), age was not a determinant of LDIR-associated risk of cancer. In conclusion, women exposed to LDIR from cardiac imaging and therapeutic procedures after MI are at a greater risk of incident cancer compared with men after similar exposure. The extrapolated absolute risk from LDIR exposure would nonetheless be expected to be low.

[State of the art and future trends in technology for computed tomography dose reduction]

The introduction of helical and multislice acquisitions in CT scanners together with decreased image reconstruction times has had a tremendous impact on radiological practice. Technological developments in the last 10 to 12 years have enabled very high quality images to be obtained in a very short time. Improved image quality has led to an increase in the number of indications for CT. In parallel to this development, radiation exposure in patients has increased considerably. Concern about the potential health risks posed by CT imaging, reflected in diverse initiatives and actions by official organs and scientific societies, has prompted the search for ways to reduce radiation exposure in patients without compromising diagnostic efficacy. To this end, good practice guidelines have been established, special applications have been developed for scanners, and research has been undertaken to optimize the clinical use of CT. Noteworthy technical developments incorporated in scanners include the different modes of X-ray tube current modulation, automatic selection of voltage settings, selective organ protection, adaptive collimation, and iterative reconstruction. The appropriate use of these tools to reduce radiation doses requires thorough knowledge of how they work.

Polypill therapy, subclinical atherosclerosis, and cardiovascular events-implications for the use of preventive pharmacotherapy: MESA (Multi-Ethnic Study of Atherosclerosis)

OBJECTIVES

This study examines whether the coronary artery calcium (CAC) score can be used to define the target population to treat with a polypill.

BACKGROUND

Prior studies have suggested a single polypill to reduce cardiovascular disease (CVD) at the population level.

METHODS

Participants from MESA (Multi-Ethnic Study of Atherosclerosis) were stratified using the criteria of 4 polypill studies (TIPS [The Indian Polycap Study], Poly-Iran, Wald, and the PILL [Program to Improve Life and Longevity] Collaboration). We compared coronary heart disease (CHD) and CVD event rates and calculated the 5-year number needed to treat (NNT) after stratification based on the CAC score.

RESULTS

Among MESA participants eligible for TIPS, Poly-Iran, Wald, and the PILL Collaboration, CAC = 0 was observed in 58.6%, 54.5%, 38.9%, and 40.8%, respectively. The rate of CHD events among those with CAC = 0 varied from 1.2 to 1.9 events per 1,000 person-years, those with CAC scores from 1 to 100 had event rates ranging from 4.1 to 5.5, and in those with CAC scores >100 the event rate ranged from 11.6 to 13.3. The estimated 5-year NNT to prevent 1 CVD event ranged from 81-130 for patients with CAC = 0, 38-54 for those with CAC scores from 1 to 100, and 18-20 for those with CAC scores >100.

CONCLUSIONS

In MESA, among individuals eligible for treatment with the polypill, the majority of CHD and CVD events occurred in those with CAC scores >100. The group with CAC = 0 had a very low event rate and a high projected NNT. The avoidance of treatment in individuals with CAC = 0 could allow for significant reductions in the population considered for treatment, with a more selective use of the polypill and, as a result, avoidance of treatment in those who are unlikely to benefit.

Evaluation of suspected ischemic heart disease in symptomatic women

There is a wealth of evidence about the role of a variety of diagnostic testing modalities to define coronary artery disease (CAD) risk in women presenting for evaluation of suspected myocardial ischemia. The exercise electrocardiogram (ECG) is the core index procedure, which can define risk in women capable of performing maximal exercise. Stress imaging, using echocardiography or myocardial perfusion single-photon emission computed tomography/positron emission tomography, is useful for symptomatic women with an abnormal resting ECG or for those who are functionally disabled. For women with low-risk stress imaging findings, there is a very low risk of CAD events, usually < 1%. There is a gradient relationship between the extent and severity of inducible abnormalities and CAD event risk. Women at high risk are those defined as having moderate to severely abnormal wall motion or abnormal perfusion imaging findings. In addition to stress imaging, the evidence of the relationship between CAD extent and severity and prognosis has been clearly defined with coronary computed tomographic angiography. In women, prognosis for those with mild but nonobstructive CAD is higher when compared with those without any CAD. The current evidence base clearly supports that women presenting with chest pain can benefit from one of the commonly applied diagnostic testing modalities.

Risk of ionizing radiation in women of childbearing age undergoing radiofrequency ablation

Background

The International Commission of Radiology recommends a pregnancy screening test to all female patients of childbearing age who will undergo a radiological study. Radiation is known to be teratogenic and its effect is cumulative. The teratogenic potential starts at doses close to those used during these procedures. The prevalence of positive pregnancy tests in patients undergoing electrophysiological studies and/or catheter ablation in our midst is unknown.

Objective

To evaluate the prevalence of positive pregnancy tests in female patients referred for electrophysiological study and/or radiofrequency ablation.

Methods

Cross-sectional study analyzing 2,966 patients undergoing electrophysiological study and/or catheter ablation, from June 1997 to February 2013, in the Institute of Cardiology of Rio Grande do Sul. A total of 1490 procedures were performed in women, of whom 769 were of childbearing age. All patients were screened with a pregnancy test on the day before the procedure.

Results

Three patients tested positive, and were therefore unable to undergo the procedure. The prevalence observed was 3.9 cases per 1,000 women of childbearing age.

Conclusion

Because of their safety and low cost, pregnancy screening tests are indicated for all women of childbearing age undergoing radiological studies, since the degree of ionizing radiation needed for these procedures is very close to the threshold for teratogenicity, especially in the first trimester, when the signs of pregnancy are not evident.

Radiation-induced noncancer risks in interventional cardiology: optimisation of procedures and staff and patient dose reduction

Concerns about ionizing radiation during interventional cardiology have been increased in recent years as a result of rapid growth in interventional procedure volumes and the high radiation doses associated with some procedures. Noncancer radiation risks to cardiologists and medical staff in terms of radiation-induced cataracts and skin injuries for patients appear clear potential consequences of interventional cardiology procedures, while radiation-induced potential risk of developing cardiovascular effects remains less clear. This paper provides an overview of the evidence-based reviews of concerns about noncancer risks of radiation exposure in interventional cardiology. Strategies commonly undertaken to reduce radiation doses to both medical staff and patients during interventional cardiology procedures are discussed; optimisation of interventional cardiology procedures is highlighted.

Cumulative radiation dose from medical imaging in chronic adult patients

Chronic patients require ongoing care that results in repeated imaging and exposure to ionizing radiation for both diagnostic and therapeutic purposes. This is of concern due to the long-term effects of radiation exposure, namely the association between radiation and increased cancer risk. In this study, the scientific literature on cumulated dose of radiation accrued from medical imaging by 4 cohorts of chronic patients (cardiac disease, end-stage kidney disease, inflammatory bowel disease, and patients undergoing endovascular aortic repair) was systematically reviewed. We found that the cumulative effective dose is moderate in cardiac and inflammatory bowel disease patients, high in end-stage kidney disease patients, and very high in endovascular aortic repair patients. We concluded that radiation burden of medical imaging is high in selected cohorts of chronic patients. Efforts should be implemented to reduce this cumulative dose and its potential attendant risks.