Version May 2024
INTRODUCTION — The use of diagnostic cardiovascular imaging has increased rapidly over the past decade owing to developments in technology, increased availability, and the perception that imaging can meaningfully affect medical decision making. Studies documenting increasing medical radiation exposure, particularly from cardiovascular imaging, have raised concerns about potential health risks associated with this exposure and have been highly publicized in the professional and lay literature [1,2].
Several of the major imaging modalities for cardiovascular diagnosis and treatment use ionizing radiation. Radionuclide myocardial perfusion imaging in the form of single photon emission computed tomography (CT) and positron emission tomography use radionuclides that produce both photon and particulate radiation. Sources of radiograph radiation include cardiovascular CT, which is used for imaging coronary artery plaque and calcification, and radiograph fluoroscopy, which is used to guide established and emerging diagnostic and therapeutic electrophysiologic, coronary, and other cardiovascular procedures.
The potential risks of imaging tests that use ionizing radiation must be weighed against the potential benefits of these tests. This assessment is difficult since the health risks related to radiation exposure at the levels common in cardiovascular imaging are controversial. In addition, limited evidence is available on the impact of these tests on clinical outcomes.
This topic will discuss radiation exposure and potential risks from cardiovascular imaging. Various cardiovascular imaging tests and radiation-related risk of medical imaging studies generally are discussed in detail separately. (See "Radiation-related risks of imaging".)
RADIATION DOSIMETRY
Parameters — Some radiation dosimetry parameters can be measured whereas others are estimates that are modeled using complex assumptions and simulations. Parameters of radiation dosimetry readily derived from physical measurements of radiation exposure (in Coulomb/kg, C/kg) include the accumulated air kerma at a reference point (Ka,r, in mGy) and the kerma-area product (KAP, in cGy × cm2 or related units) in radiography and fluoroscopy (in units of milliGray, mGy), the volume computed tomographic dose index (CTDIvol, in mGy) and the dose-length product (DLP, in mGy x cm) in computed tomography (CT) [3,4]. These parameters are extremely useful to establish so-called "diagnostic reference levels" for quality control and benchmarking among institutions that perform cardiac imaging with ionizing radiation [5]. For example, consistently exceeding the 75th to 80th percentile as established in radiation dose surveys should suggest to an individual institution the need for reevaluation and change of practices. Establishing reference values has been shown to reduce the median dose and interinstitutional dose variability of radiological procedures [6,7]. Parameters of radiation dosimetry are discussed in detail elsewhere. (See "Clinical manifestations, evaluation, and diagnosis of acute radiation exposure", section on 'Measures of radiation'.)
The effective dose (E, expressed in units of milliSievert, mSv) [8], the radiation dose parameter most frequently reported in medical journals, is a broad estimate of the risk of biologic detriment from a partial body exposure to ionizing radiation that allows comparisons between different imaging protocols, between different types of radiological examinations or between man-made and natural sources of radiation. Conversely, because E is estimated based on generic mathematical models of the human body and does not take into account variations of human anatomy, E cannot be used to compare radiation doses for the same type of procedure between different patients. There is no measurable physical gold standard for E. Given the complex modeling and many assumptions involved with the estimation of E, E should generally be reported as ranges, not at specific values with decimal precision [9].
Confusion between E and reported organ doses should be avoided. Estimation of organ doses is one of several steps in the estimation of E and there are various types of organ doses. To avoid possible ambiguity, the dose to an organ should best be described as the organ's absorbed dose, expressed in units of mGy. However, sometimes the organ equivalent dose expressed in mSv is reported and can be mistaken for E because they share the same unit of measurement although their values differ. For example, in cardiac CT imaging, the numerical value of the equivalent dose of the breast is typically several times higher than that of E.
Individualization of dose and risk estimates is complex and inherently imperfect. Longitudinal tracking of individual cumulative lifetime dose of nontherapeutic medical radiation in patients is currently not standard because of its logistical challenges and disagreement as to its usefulness and societal value [10]. Efforts are underway to develop pertinent information systems [11].
Radiation doses associated with medical imaging
Epidemiology — According to the National Council on Radiation Protection and Measurement (NCRP) reports numbers 160 [12-14] and 184 [15], the collective medical radiation dose to the United States population (excluding dental and radiotherapy) increased by 730 percent from 123,7000 person-Sv in the early 1980s, to 900,000 person-Sv in 2006, before decreasing somewhat to 750,000 person-Sv by 2016. These numbers appear dramatic, but collective dose has been criticized as a measure since a large dose delivered to a small number of people is not the same as a small dose delivered to many people. The collective dose does not account for the fact that by far the largest proportion of the population-averaged radiation dose is delivered to the ill and older adults. The annual total radiation exposure to individuals who are NOT exposed to medical ionizing radiation has generally changed only modestly since 1982.
The highest proportion of the collective dose of nontherapeutic medical radiation (49 percent) in 2006 was related to CT, the use of which increased by 10 to 11 percent per year from 18.3 million studies in 1993 to 62 million in 2006. In 2006, cardiac CT represented 4.7 percent of all CT studies and 12.1 percent of the collective dose received from CT, according to this NCRP report.
Nuclear medicine studies represented 26 percent of the collective dose in 2006. The use of nuclear medicine studies increased over fourfold from 7.6 million in 1982 to an estimated 18.1 million in 2006. The highest increase in utilization was related to cardiac imaging. In 2005, cardiac imaging studies represented 57 percent of patient visits related to nuclear medicine (increased from 1 percent in 1973) and 85 percent of the collective dose received from nuclear medicine studies.
In a study using administrative claims data for over 950,000 insured adults <65 years old, 9.5 percent underwent at least one cardiac imaging procedure during 2005 to 2007 [16]. Among those receiving ≥1 cardiac imaging procedures, the estimated mean cumulative effective dose over three years from cardiac imaging was 23.1 mSv (range 1.5 to 543.7 mSv). Most (74 percent) of the cumulative effective dose was from radionuclide myocardial perfusion imaging (rMPI).
Radiation dose and determinants — The accompanying table lists representative values and ranges of effective dose estimates from the literature for various radiologic imaging studies (table 1 and table 2) [10]. The dose-saving strategies in CT that are reflected in this table are discussed in the next section. For comparison, the average annual background radiation in the United States is approximately 3 mSv (range, 1 to 10 mSv) and the radiation dose received during a six-hour commercial airline flight is approximately 0.03 mSv.
In fluoroscopy, the principal determinants of radiation exposure are patient habitus, operator technique and procedural complexity (which affect exposure time), and the radiograph system and its selected settings. An evaluation of fluoroscopic exposure rates in 41 cardiac catheterization laboratory systems using a standardized methodology revealed a four- to sixfold variation among systems [17]. Exposure rates under simulated medium habitus conditions varied over sixfold from less than 0.3 to 1.7 mC/kg/min, with a median of 0.8 mC/kg/min. Only 25 percent of systems had satisfactory image quality at a low exposure rate. In a review of almost 1000 coronary procedures performed at the Mayo Clinic during 1997, the median exposure was 35 mC/kg for diagnostic procedures and 96 mC/kg for interventional procedures [18].
The mean duration of fluoroscopy in electrophysiologic interventional procedures was 41 minutes in one report, with a range of 15 to 67 minutes [19]. A typical procedure resulted in a total effective dose of 8.3 mSv per hour of fluoroscopy. The mean fluoroscopy time was typically longer, and thus radiation exposure was greater for paroxysmal atrial fibrillation than for common atrial flutter or accessory pathway ablation: 57 versus 20 to 22 minutes in one report [20] and 130 versus 30 and 17 minutes in another [21]. As mentioned above, patient-specific factors can also affect radiation dose. In a series of 85 patients undergoing pulmonary vein isolation procedures for the treatment of atrial fibrillation, patients with obesity received more than twice the effective radiation dose of normal-weight patients (mean 39 versus 15 mSv) [22].
Effective radiation doses from CT imaging vary with equipment, patient size, and body parts imaged. In addition, wide variation (eg, mean 13-fold) in effective radiation dose within CT exam types has been observed within and across institutions [23]. Facilities performing full-body CT imaging for "screening" purposes often adjust radiation doses to levels 20 to 50 percent below typical diagnostic studies to market so-called "low-dose CT scans." However, too low a dose relative to patient size may result in images that have limited diagnostic value. (See "Radiation-related risks of imaging", section on 'CT examinations'.)
In cardiac CT, examinations performed to quantify coronary artery calcification generally impart a lower dose than examinations performed for coronary CT angiography (CCTA) [10]. Among the multidetector row scanners used for cardiac CT, scanners with a higher number of detector rows or "slices" (typically 4 in 1999, 16 in 2003, 64 in 2005, and as many as 320 in 2013) typically impart a higher radiation dose using the standard helical technique, although many newer scanners incorporate scanning and reconstruction algorithms that enable significant radiation dose reductions. As a result of differences in scanner setting and imaging protocols, the effective dose received from CCTA can differ substantially (eg, sixfold variation between institutions in a multinational survey [24]).
Multiple testing — Patients frequently undergo multiple medical tests involving radiation exposure leading to high cumulative doses of radiation. This was illustrated by a retrospective cohort study of 1097 consecutive patients undergoing rMPI [25]. During an approximately 20-year period, the patients underwent a median of 15 (interquartile range, 6 to 32; mean 23.9) procedures involving radiation exposure. Of these, a median of four (mean, 6.5) were high-dose procedures (≥3 mSv) including 1 (mean, 1.8) rMPI exam per patient. The cumulative estimated effective dose from all medical sources exceeded 100 mSv in 31.4 percent of patients.
Options for reducing radiation dose — Patients undergoing diagnostic testing and interventional catheter-based percutaneous procedures may receive substantial radiation exposure. The first step in reducing radiation exposure is use of testing and management strategies that are medically appropriate with careful assessment of individualized potential risks and benefits. (See 'Balancing risks and benefits' below.)
The operator of a procedure entailing radiation exposure has an obligation to expose the patient and the staff to the minimal dose of radiation needed to complete the procedure successfully. Particularly in complex electrophysiologic procedures such as ablation for atrial fibrillation, newer imaging and mapping techniques have reduced fluoroscopy times. Pulse fluoroscopy and optimization of fluoroscopy exposure parameters also reduce the risk of radiation injury.
In radionuclide imaging, choice of the radiopharmaceutical, individualized adjustment of the injected activity, use of sensitive equipment and improved reconstruction algorithms, and use of one-day or stress-only protocols are among the options for reducing radiation dose. The International Atomic Energy Agency (IAEA) conducted a cross-sectional study of nuclear cardiology practice and protocols in nearly 8000 patients in 65 countries [26]. Eight best practices relating to radiation dose reduction from nuclear cardiology were identified a priori by an IAEA expert panel. While there was a wide range of radiation doses observed, patients undergoing radionuclide imaging in laboratories following more of these best practices received lower radiation doses.
The radiation dose of cardiac CT can be reduced with certain scanning techniques, some of which may affect image quality. The most basic approach, which requires some experience on the part of the performing healthcare provider, is individualized adjustment of scanning parameters such as tube voltage and scan length that take into account the variability of anatomy between different patients. Cardiac CT-specific software-based modifications of common CT scanning protocols are available. For example, electrocardiogram (ECG)-controlled tube current modulation (ECTCM) markedly reduces the output of the radiograph tube during certain portions of the cardiac cycle when so-called retrospective gating is used. The benefit of ECG-dependent dose modulation is reduced at higher heart rates with standard single-source CCTA [27], but not with dual source CCTA [28]. Prospectively triggered sequential scanning is available with some multidetector scanners and produces radiation only during predetermined portions of the cardiac cycle [29]. Other dose-reduction methods include iterative reconstruction, whole-heart volume scanning, and high-pitch helical scanning.
In a statewide registry of a collaborative radiation dose-reduction program that included education on a best-practice CCTA scanning model using some or all of these techniques [30], the mean E of CCTA was reduced by 53 percent from 21 mSv to 10 mSv over the course of a year. In an international, multicenter survey of radiation dose in CCTA performed in 2007 [24], ECTCM lowered E by 25 percent, reduction of tube voltage (from 120 to 100 kVp) reduced E by 46 percent, and sequential scanning reduced E by 78 percent. ECTCM was used in 73 percent of patients, but the most effective dose reduction strategies were rarely used (sequential scanning in 6 percent or patients and reduction of tube voltage in 5 percent). This may have been in part because of concerns that dose-sparing scanning protocols may interfere with image quality and diagnostic accuracy of CCTA. However, in several direct comparisons between conventional retrospectively gated and newer prospectively triggered scanning [31,32], subjective image quality and diagnostic accuracy were similar whereas radiation dose was substantially lower in the latter group (21 and 21 mSv versus 4 and 6 mSv). These data will hopefully result in wider acceptance and use of dose-saving imaging strategies.
HEALTH RISKS OF RADIATION EXPOSURE — Exposure to ionizing radiation from medical imaging may lead to tissue reactions and/or stochastic effects:
●A tissue reaction (formerly known as a deterministic effect) is one in which severity is determined by the dose. A dose threshold (ie, a dose below which an effect is not seen) is characteristic of a tissue reaction. A skin burn is an example of a tissue reaction due to ionizing radiation. Radiation exposure during prolonged fluoroscopic procedures can result in skin burns, usually with fluoroscopy times longer than 60 minutes. Those burns are often under-reported since they may not develop for weeks after the procedure. In a study on fluoroscopy used in electrophysiologic ablation procedures, one report included 859 patients undergoing ablation of the atrioventricular node or accessory pathway in which the mean duration of fluoroscopy was 53 minutes [33]. The radiation dose needed to cause radiation skin injury was exceeded during 22 percent of procedures [34,35]. Patients with repeated doses of radiation to the same skin entry portal may be at increased risk.
●A stochastic effect represents an outcome for which the probability of occurrence (rather than severity) is determined by the dose. An example is radiation-induced carcinogenesis, which occurs after a typically prolonged but variable delay (latency) after exposure. These effects may not have an apparent threshold dose. The stochastic consequences of exposure to ionizing radiation at the doses used in medical imaging for public and individual patient health are somewhat controversial. The radiation sensitivity of biological cells is related to the rate of proliferation, number of future divisions, and degree of differentiation. It is undisputed that ionizing radiation can cause chromosomal changes and that high doses of radiation are associated with an increase in malignancies. However, not all chromosomal changes will translate into phenotypic illness.
The doses of ionizing radiation received in medical imaging are typically considerably lower than those received in nuclear explosions or accidents. Although there is controversy, the majority opinion of experts is that the health consequences resulting from whole body irradiation, as occurred in Hiroshima and Nagasaki, can be extrapolated to the "low" (<100 units of millisievert [mSv]) dose partial body exposures that occur in medical imaging. There are epidemiological studies of atomic bomb survivors, nuclear industry workers in 15 countries, and in utero radiograph exposure that have been interpreted as being consistent with an increase in cancer risk at radiation doses comparable to those received by some patients undergoing cardiovascular imaging studies [36]. The strongest evidence to date relating low-dose radiation from medical imaging to increased risk of cancer derives from a cohort study of nearly 180,000 children who underwent CT exams in the United Kingdom between 1985 and 2002, in which statistically significant increases in brain cancer and leukemia were noted with doses as low as 30 mSv [37].
The symptoms, diagnosis, and management of acute radiation sickness and the types (tissue reaction versus stochastic effect) and nature of long-term effects that can occur in victims of nuclear explosions or accidents are discussed elsewhere. (See "Clinical manifestations, evaluation, and diagnosis of acute radiation exposure".)
Potential carcinogenesis from imaging — Defining the carcinogenic potential of ionizing radiation at the doses used in medical imaging is made difficult by the intrinsic, substantial background risk of cancer of the general population and the ubiquity of natural background radiation [10]. Given the many confounding issues, together with the difficulties related to determining patient-specific radiation doses accurately that are discussed above and the latency period of 10 to 40 years for most radiation-induced solid malignancies, studies designed to examine possible carcinogenic effects of ionizing radiation at the levels used in cardiovascular imaging require very large sample sizes and many years of follow-up. Such medically exposed cohorts are only beginning to be studied, and the results of numerous epidemiological investigations are expected over the next five years [37-39].
Given the many uncertainties related to dose-response relationship of radiation exposure, radiation protection is typically discussed on the basis of the so-called "linear no-threshold" model [40]. This model holds that any level of ionizing radiation dose, no matter how low, can cause cancer and that the risk of cancer increases linearly with radiation dose. This model of dose-response is unproven but has been chosen by several influential bodies of experts concerned with radiation protection as the best simple model fitting the available data on the relationships between radiation dose and the lifetime attributable risk of cancer, with the understanding that there still remain considerable uncertainties.
By contrast, a "linear quadratic" model is more complex, incorporating terms that are proportional both to dose and the square of dose. The concept of "radiation hormesis" [41] dismisses any risk of cancer at low radiation dose, and instead assumes a protective effect, presumably on the basis of up-regulation of molecular cell repair mechanisms.
It is important to realize that all published estimates of potential cancer risk related to cardiovascular imaging are based on the linear no-threshold model. Within this conceptual framework, the age- and sex-averaged lifetime risk of dying from radiation-related cancer has been estimated to be 5 to 7.9 in 100 individuals of the general population who are exposed to 1 Sv of effective dose [40,42]. The following examples illustrate published risk estimates:
●An analysis from the United Kingdom estimated that fluoroscopic radiation exposure during catheter-based coronary angiography may cause up to 280 cases of cancer per million examinations performed [43]. Other studies estimated that the radiation dose received from 53 to 60 minutes of fluoroscopy during electrophysiologic ablation procedures would result in 0.7 to 1.4 excess fatal malignancies per 1000 females and 1.0 to 2.6 per 1000 males [21,33].
●The potential lifetime-attributable risk (LAR) of cancer for CCTA varies markedly with age and sex. The LAR of cancer is much greater for females (due to risk of breast cancer in addition to lung cancer), younger patients, and for combined cardiac and aortic scanning. Older age is associated with lower risk since the radiosensitivity of many organs such as breast appears to decline with age and there is typically a long latency period from radiation exposure to development of malignancy [27,44]. In one study, for example, a single helical 64-slice CCTA without electrocardiogram-controlled tube current modulation was associated with a lifetime cancer risk estimate of 1 in 143 (0.7 percent) in a 20-year-old female and 1 in 466 (0.2 percent) in a 60-year-old female [27]. Lifetime cancer risk estimates were lower in male adults: 1 in 686 (0.15 percent) in a 20-year-old male and 1 in 1241 (0.08 percent) for a 60-year-old male. However, considerably lower cancer risks would be expected from contemporary scanning protocols that involve dose reduction techniques.
BALANCING RISKS AND BENEFITS — The potential risks of tests that use ionizing radiation must be weighed against the potential benefits of these tests. This assessment is difficult since the estimates on health risks related to radiation exposure at the levels common in cardiovascular imaging are controversial. In addition, evidence is limited on the impact of these tests on clinical outcomes.
Acknowledging these limitations, "patient-centered imaging" with an individualized assessment of potential risks and benefits of each imaging procedure is required that incorporates the patient's age and sex, clinical presentation, the health risks implied by the tentative diagnosis for which imaging is to be performed and the types of imaging modalities that are appropriate to address the clinical question at hand [45,46].
As an example, in CCTA or radionuclide myocardial perfusion stress testing in a 65-year-old symptomatic male whose chest pain is at intermediate probability of being due to ischemic heart disease, the benefit of identifying treatable, potentially life-threatening coronary artery disease would generally be considered as outweighing the potential risk of imaging associated radiation. This is true given the probability of morbidity and mortality from undiagnosed cardiovascular disease in such an individual before a potential radiation-induced cancer could emerge as a clinical problem. In contrast, CCTA to assess prognosis in an asymptomatic 40-year-old female by identifying or excluding the presence of subclinical coronary artery plaques ("screening") is not proven to improve quality of life or longevity. In this situation, the potential risk would likely outweigh the potential benefit. The risk/benefit of such screening examination might require re-evaluation in the future if coronary CT examinations at very low doses (<3 mSv) became available and if a clinical benefit of such screening was demonstrated by outcomes data.
Guidance documents for minimizing radiation exposure with cardiac imaging are available [10,46-48]. Some common recommendations are:
●Appropriateness guidelines and/or decision support tools for imaging exam ordering
●Mechanisms to avoid duplication imaging
●Individualized image acquisition (ie, tailored to age, weight, etc) to address the specific clinical indication
●Utilization of evolving scanning technologies to minimize the dose of an individual exam
●Longitudinal and systematic exam dose monitoring and tracking by the imaging facility
Although, the health risks related to radiation exposure at the levels common in cardiovascular imaging are controversial, it is prudent to follow the principles of performing only clinically appropriate tests and if testing is indicated, keeping the patient dose "as low as reasonably achievable." A 2009 science advisory on ionizing radiation in cardiac imaging from the American Heart Association offered the following recommendations [10]:
●Cardiac imaging studies that expose patients to ionizing radiation should only be ordered after individualized assessment of risks and benefits to the patient, and in accordance with established appropriateness criteria.
•It is important to consider the risk of missing an important diagnosis if imaging is not performed because of concerns about radiation exposure.
•Among equivalent tests, the one that exposes that patient to the least amount of radiation should be chosen.
•Among younger patients, imaging modalities without radiation exposure should be preferred if possible (for example, magnetic resonance coronary angiography over CCTA if a congenital coronary anomaly is to be excluded or defined, or stress echocardiography instead of radionuclide myocardial perfusion imaging in patients with chest pain).
•Potential risks and benefits of the imaging exam being considered should be discussed with the patient whenever practical and appropriate.
•Every effort should be made to avoid needlessly repeating imaging studies that use ionizing radiation.
●Once it has been established that a cardiac imaging test that uses ionizing radiation is needed, the test should be performed with every effort to reduce patient dose as much as possible without jeopardizing the diagnostic quality of the exam.
●Routine surveillance radionuclide stress tests or cardiac CTs in asymptomatic patients at low risk for ischemic heart disease are not recommended.
A follow-up scientific statement from the American Heart Association [47] outlined practical and specific strategies for further enhancement of radiation safety in medical imaging. This statement identified education of patients and clinicians, clinical justification of imaging procedures that use ionizing radiation, and optimization of the radiation exposure from imaging procedures specific to the patient and clinical question at hand. Some of the key recommendations in this statement included:
●Healthcare providers who can request cardiac imaging procedures should be required to know which cardiac imaging tests use ionizing radiation, basic concepts related to medical radiation exposure and dose, and typical dose estimates for the most common cardiac imaging procedures.
●Nonemergency cardiac imaging using ionizing radiation should be performed on the basis of shared decision making. The decision to proceed with imaging should be consistent with both medical evidence and patient values and preferences.
●All cardiac imaging facilities should record all relevant radiation-related data. These exposure reports should be archived and audited regularly for quality assurance and benchmarking.
●In trials, comparative effectiveness studies, and registries that involve diagnostic cardiac imaging with ionizing radiation, all relevant radiation exposure data should be collected and reported.
Additional recommendations were made in a National Institutes of Health-sponsored symposium focusing on shared decision making for cardiac imaging procedures with exposure to ionizing radiation [46]. The following recommendations were made in 2013 for laboratory practice to enhance patient-centered imaging, with the expectation that all of these recommendations should in time become mandatory:
●Required (supported by majority opinion) measures included reporting of appropriate use criteria categories (appropriate, uncertain, and inappropriate), dosimetry reporting, development of diagnostic reference levels for a variety of specific cardiac imaging tasks, and implementation of continuous quality improvement programs.
●Recommended (supported by general agreement) measures included implementation of decision support tools and continuing medical education for referring physicians.
●A suggested (supported by expert opinion) measure was creation of a repository from electronic health record data on each patient's past history of medical imaging radiation exposure.
SUMMARY AND RECOMMENDATIONS
●Radiation dosimetry reference values are useful for quality control and benchmarking among institutions. (See 'Parameters' above.)
●The effective dose is a broad estimate of the risk of biologic detriment from a partial body exposure to ionizing radiation. (See 'Parameters' above.)
●The collective medical radiation dose to the United States population has increased severalfold since the early 1980s, largely related to computed tomography (CT) and nuclear medicine studies. The annual total radiation exposure to individuals who are not exposed to medical ionizing radiation has generally changed only modestly since 1982. (See 'Epidemiology' above.)
●Determinants of radiation dose from fluoroscopy include patient habitus (greater for patients with obesity), operator technique and procedural complexity (which impact exposure time), the radiograph system, and selected settings. Substantial variation in fluoroscopic exposure rates among cardiac catheterization laboratories has been observed. (See 'Radiation dose and determinants' above.)
●Effective radiation doses from CT imaging vary with equipment, patient size, body parts imaged, and imaging protocols. Several strategies are available for reducing radiation dose and these do not necessitate a reduction in image quality. (See 'Options for reducing radiation dose' above.)
●In radionuclide imaging, the choice of the radiopharmaceutical, individualized adjustment of injected activity, use of sensitive equipment and improved reconstruction algorithms, and use of stress-only protocols are options for reducing radiation dose.
●Prolonged fluoroscopic exposure (generally greater than 60 minutes) can cause skin burns. (See 'Health risks of radiation exposure' above.)
●The risk of radiation-induced carcinogenesis from medical imaging is controversial. Estimates of potential cancer risk from cardiovascular imaging are based on a linear no-threshold model, which, while unproven, is the model best supported by the currently-available epidemiological data. (See 'Potential carcinogenesis from imaging' above.)
●Cardiac imaging studies that expose patients to ionizing radiation should only be ordered after individualized assessment of risks and benefits to the patient, and in accordance with established appropriateness criteria. Among equivalent options, the one that exposes that patient to the least amount of radiation should be chosen. The selection of an alternative test that involves no ionizing radiation, such as echocardiography or magnetic resonance imaging, should be considered. (See 'Balancing risks and benefits' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Thomas C Gerber, MD, PhD, FACC, FAHA, who contributed to earlier versions of this topic review.
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