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

Deep Learning Analysis of Upright-Supine High-Efficiency SPECT Myocardial Perfusion Imaging for Prediction of Obstructive Coronary Artery Disease: A Multicenter Study

Combined analysis of SPECT myocardial perfusion imaging (MPI) performed with a solid-state camera on patients in 2 positions (semiupright, supine) is routinely used to mitigate attenuation artifacts. We evaluated the prediction of obstructive disease from combined analysis of semiupright and supine stress MPI by deep learning (DL) as compared with standard combined total perfusion deficit (TPD). Methods: 1,160 patients without known coronary artery disease (64% male) were studied. Patients underwent stress ^99mTc-sestamibi MPI with new-generation solid-state SPECT scanners in 4 different centers. All patients had on-site clinical reads and invasive coronary angiography correlations within 6 mo of MPI. Obstructive disease was defined as at least 70% narrowing of the 3 major coronary arteries and at least 50% for the left main coronary artery. Images were quantified at Cedars-Sinai. The left ventricular myocardium was segmented using standard clinical nuclear cardiology software. The contour placement was verified by an experienced technologist. Combined stress TPD was computed using sex- and camera-specific normal limits. DL was trained using polar distributions of normalized radiotracer counts, hypoperfusion defects, and hypoperfusion severities and was evaluated for prediction of obstructive disease in a novel leave-one-center-out cross-validation procedure equivalent to external validation. During the validation procedure, 4 DL models were trained using data from 3 centers and then evaluated on the 1 center left aside. Predictions for each center were merged to have an overall estimation of the multicenter performance. Results: 718 (62%) patients and 1,272 of 3,480 (37%) arteries had obstructive disease. The area under the receiver operating characteristics curve for prediction of disease on a per-patient and per-vessel basis by DL was higher than for combined TPD (per-patient, 0.81 vs. 0.78; per-vessel, 0.77 vs. 0.73; P < 0.001). With the DL cutoff set to exhibit the same specificity as the standard cutoff for combined TPD, per-patient sensitivity improved from 61.8% (TPD) to 65.6% (DL) (P < 0.05), and per-vessel sensitivity improved from 54.6% (TPD) to 59.1% (DL) (P < 0.01). With the threshold matched to the specificity of a normal clinical read (56.3%), DL had a sensitivity of 84.8%, versus 82.6% for an on-site clinical read (P = 0.3). Conclusion: DL improves automatic interpretation of MPI as compared with current quantitative methods.

Radiation-Induced Sarcoma following Prolonged Coronary Stent Placement

Radiation exposure for the average coronary stent placement varies based on a number of factors but typically amounts to 6-11 mSv per patient (compared to 3 mSv background). As with all procedures which utilize radiation, there is an inherent risk of genetic mutation and the possible development of malignancy. Here, we present the case of a 75-year-old male who presented with an exophytic mass on his back following prolonged coronary catheterization with a radiation burn seven years prior. Biopsy of the lesion revealed the mass was consistent with an undifferentiated pleomorphic sarcoma emanating from the site of the radiation burn. After staging studies demonstrated no evidence of metastatic disease, radical excision with negative margins was performed. This case demonstrates that despite the rarity of radiation injury, each incidence necessitates strict monitoring of radiation exposure and continual follow-up due to the risk of malignancy.

The Status of Stress Myocardial Perfusion Imaging Using 99mTc Pharmaceuticals in Japan: Results from a Nationwide Survey

Objective(s):

To appropriately use one-day myocardial perfusion imaging (MPI) with ^99mTc radiopharmaceuticals (i.e. to avoid shine-through artifacts), injection doses need to be optimized and dose ratios between the 1^st and 2^nd scans should be maintained at ≥ 3. However, the current state of practice in Japan is unclear. Thus, the aim of this study was to clarify the details of MPI protocols using ^99mTc radiopharmaceuticals in Japan.

Methods:

A nationwide survey was conducted in June and July 2016. Questionnaires about stress MPI protocols using ^99mTc radiopharmaceuticals were sent to 641 nuclear medicine facilities.

Results:

Responses were received from 246 facilities. One-day protocols were used in 97.1% of the facilities. The most common injection dose ratio was 2.5. Only 18.2% of facilities achieved the recommended injection dose ratio. Stress-only protocols were performed in only 1.7% of facilities; the primary reasons for not performing stress-only protocols were as follows: 1) “The reading-physician cannot interpret the image just after the first scan,” and 2) “Preparation of radiopharmaceuticals and scan arrangements turn out to be complicated.”

Conclusion:

Approximately 80% of nuclear medicine facilities do not follow the recommended injection dose ratio. Stress-only protocols are ideal, but are performed at very few facilities. Both optimization and standardization of stress MPI protocols using ^99mTc radiopharmaceuticals are needed in Japan.

Risk-related 18F-FDG PET/CT and new diagnostic strategies in patients with solitary pulmonary nodule: the ITALIAN multicenter trial

PURPOSE

Diagnosis of solitary pulmonary nodule (SPN) is an important public health issue and ¹⁸F-FDG PET/CT has proven to be more effective than CT alone. Pre-test risk stratification and clinical presentation of SPN could affect the diagnostic strategy. A relevant issue is whether thoracic segmental (s)-PET/CT could be implemented in patients with SPN. This retrospective multicenter study compared the results of FDG whole-body (wb)-PET/CT to those of s-PET/CT.

METHODS

¹⁸F-FDG PET/CT of 502 patients, stratified for pre-test cancer risk, were retrospectively analyzed. The thoracic part of wb-PET/CT, considered s-PET/CT, was compared to wb-PET/CT. Clinical and PET/CT variables were investigated for SPN characterization as well as for identification of patients in whom s-PET/CT could be performed. Histopathology or follow-up data were used as a reference.

RESULTS

In the study population, 36% had malignant, 35% benign, and 29% indeterminate SPN. ¹⁸F-FDG uptake indicative of thoracic and extra-thoracic lesions was detectable in 13% and 3% of the patients. All patients with extra-thoracic metastases (n = 13) had thoracic lymph node involvement and highest ¹⁸F-FDG uptake at level of SPN (negative predictive value 100%). Compared to wb-PET/CT, s-PET/CT could save about 2/3 of ¹⁸F-FDG dose, radiation exposure or scan-time, without affecting the clinical impact of PET/CT.

CONCLUSION

Pre-test probability of malignancy can guide the diagnostic strategy of ¹⁸FDG-PET/CT in patients with SPN. In subjects with low-intermediate pretest probability s-PET/CT imaging might be planned in advance, while in those at high risk and with thoracic lymph node involvement a wb-PET/CT is necessary.

Exposure to Low-Dose Ionizing Radiation From Cardiac Procedures and Malignancy Risk in Adults With Congenital Heart Disease

Background:

Adults with congenital heart disease (CHD) are exposed to increasing amounts of low-dose ionizing radiation (LDIR) from cardiac procedures. Cancer prevalence in this population is higher than in the general population. This study estimates the association between LDIR exposure from cardiac procedures and incident cancer in adult patients with CHD.

Methods:

The study population derived from the Quebec Congenital Heart Disease Database. We measured cumulative numbers of LDIR-related cardiac procedures for each patient until 1 year before the time of cancer diagnosis or administrative censoring. To assess the association between LDIR exposure and cancer risk, we conducted a nested case-control study and matched cancer cases with controls on sex, CHD severity, birth year, and age.

Results:

The study included 24 833 adult patients with CHD aged 18 to 64 years from 1995 to 2009. In >250 791 person-years of follow-up, 602 cancer cases were observed (median age, 55.4 years). The cumulative incidence of cancer estimated up to 64 years of age was 15.3% (95% confidence interval [CI], 14.2–16.5). Cases had more LDIR-related cardiac procedures than controls (1410 versus 921 per 1000 adult patients with CHD, P <0.0001). Cumulative LDIR exposure was independently associated with cancer (odds ratio [OR], 1.08 per procedure; 95% CI, 1.04–1.13). Similar results were obtained by using dose estimates for LDIR exposure (OR, 1.10 per 10 mSv; 95% CI, 1.05–1.15) with a possible dose-related response. The effect measure was in the same direction, and the association was persistent for exposure from ≥6 procedures in all sensitivity analyses: after excluding most smoking-related cancer cases (OR, 1.10 per procedure; 95% CI, 1.05–1.16 and OR when exposure from ≥6 procedures, 3.08; 95% CI, 1.77–5.37), and after applying a 3-year lag period (OR, 1.09 per procedure; 95% CI, 1.03–1.14 and OR when exposure from ≥6 procedures: 2.58; 95% CI, 1.43–4.69).

Conclusions:

To our knowledge, this is the first large population-based study to analyze and document the association between LDIR-related cardiac procedures and incident cancer in the population of adults with CHD. Confirmations of these findings by prospective studies are needed to reinforce policy recommendations for radiation surveillance in patients with CHD where no regulation currently exists. Physicians ordering and performing cardiac imaging should ensure that exposure is as low as reasonably achievable without sacrificing quality of care.

Deep Learning for Prediction of Obstructive Disease From Fast Myocardial Perfusion SPECT: A Multicenter Study

OBJECTIVES

The study evaluated the automatic prediction of obstructive disease from myocardial perfusion imaging (MPI) by deep learning as compared with total perfusion deficit (TPD).

BACKGROUND

Deep convolutional neural networks trained with a large multicenter population may provide improved prediction of per-patient and per-vessel coronary artery disease from single-photon emission computed tomography MPI.

METHODS

A total of 1,638 patients (67% men) without known coronary artery disease, undergoing stress ^99mTc-sestamibi or tetrofosmin MPI with new generation solid-state scanners in 9 different sites, with invasive coronary angiography performed within 6 months of MPI, were studied. Obstructive disease was defined as ≥70% narrowing of coronary arteries (≥50% for left main artery). Left ventricular myocardium was segmented using clinical nuclear cardiology software and verified by an expert reader. Stress TPD was computed using sex- and camera-specific normal limits. Deep learning was trained using raw and quantitative polar maps and evaluated for prediction of obstructive stenosis in a stratified 10-fold cross-validation procedure.

RESULTS

A total of 1,018 (62%) patients and 1,797 of 4,914 (37%) arteries had obstructive disease. Area under the receiver-operating characteristic curve for disease prediction by deep learning was higher than for TPD (per patient: 0.80 vs. 0.78; per vessel: 0.76 vs. 0.73: p < 0.01). With deep learning threshold set to the same specificity as TPD, per-patient sensitivity improved from 79.8% (TPD) to 82.3% (deep learning) (p < 0.05), and per-vessel sensitivity improved from 64.4% (TPD) to 69.8% (deep learning) (p < 0.01).

CONCLUSIONS

Deep learning has the potential to improve automatic interpretation of MPI as compared with current clinical methods.

Evaluation of a High Concentrated Contrast Media Injection Protocol in Combination with Low Tube Current for Dose Reduction in Coronary Computed Tomography Angiography: A Randomized, Two-center Prospective Study

RATIONALE AND OBJECTIVES

The study aimed to prospectively evaluate the radiation dose reduction potential and image quality (IQ) of a high-concentration contrast media (HCCM) injection protocol in combination with a low tube current (mAs) in coronary computed tomography angiography.

MATERIALS AND METHODS

Eighty-one consecutive patients (mean age: 62 years; 34 females; body mass index: 18-31) were included and randomized-assigned into two groups. All computed tomography (CT) examinations were performed in two groups with the same tube voltage (100 kV), flow rate of contrast medium (5.0 mL/s), and iodine dose (22.8 g). An automatic mAs and low concentration contrast medium (300 mgI/mL) were used in group A, whereas effective mAs was reduced by a factor 0.6 along with HCCM (400 mgI/mL) in group B. Radiation dose was assessed (CT dose index [CTDI_vol] and dose length product), and vessel-based objective IQ for various regions of interest (enhancement, noise, signal-to-noise ratio, and contrast-to-noise ratio), subjective IQ, noise, and motion artifacts were analyzed overall and vessel-based with a 5-point Likert scale.

RESULTS

The CT attenuation of coronary arteries and image noise in group B were significantly higher than those in group A (ranges: 507.5-548.1 Hounsfield units vs 407.5-444.5 Hounsfield units; and 20.3 ± 8.6 vs 17.7 ± 8.0) (P ≤ 0.0166). There was no significant difference between the two groups in signal-to-noise ratio, contrast-to-noise ratio, and subjective IQ of coronary arteries (29.4-31.7, 30.0-37.0, and medium score of 5 in group A vs 29.4-32.4, 27.7-36.3, and medium score of 5 in group B, respectively, P ≥ 0.1859). Both mean CTDI_vol and dose length product in group B were 58% of those of group A.

CONCLUSIONS

HCCM combined with low tube current allows dose reduction in coronary computed tomography angiography and does not compromise IQ.

Defining Quality in Cardiovascular Imaging: A Scientific Statement From the American Heart Association

The aims of the current statement are to refine the definition of quality in cardiovascular imaging and to propose novel methodological approaches to inform the demonstration of quality in imaging in future clinical trials and registries. We propose defining quality in cardiovascular imaging using an analytical framework put forth by the Institute of Medicine whereby quality was defined as testing being safe, effective, patient-centered, timely, equitable, and efficient. The implications of each of these components of quality health care are as essential for cardiovascular imaging as they are for other areas within health care. Our proposed statement may serve as the foundation for integrating these quality indicators into establishing designations of quality laboratory practices and developing standards for value-based payment reform for imaging services. We also include recommendations for future clinical research to fulfill quality aims within cardiovascular imaging, including clinical hypotheses of improving patient outcomes, the importance of health status as an end point, and deferred testing options. Future research should evolve to define novel methods optimized for the role of cardiovascular imaging for detecting disease and guiding treatment and to demonstrate the role of cardiovascular imaging in facilitating healthcare quality.

Diagnostic performance of semi-quantitative and quantitative stress CMR perfusion analysis: a meta-analysis

BACKGROUND

Stress cardiovascular magnetic resonance (CMR) perfusion imaging is a promising modality for the evaluation of coronary artery disease (CAD) due to high spatial resolution and absence of radiation. Semi-quantitative and quantitative analysis of CMR perfusion are based on signal-intensity curves produced during the first-pass of gadolinium contrast. Multiple semi-quantitative and quantitative parameters have been introduced. Diagnostic performance of these parameters varies extensively among studies and standardized protocols are lacking. This study aims to determine the diagnostic accuracy of semi- quantitative and quantitative CMR perfusion parameters, compared to multiple reference standards.

METHOD

Pubmed, WebOfScience, and Embase were systematically searched using predefined criteria (3272 articles). A check for duplicates was performed (1967 articles). Eligibility and relevance of the articles was determined by two reviewers using pre-defined criteria. The primary data extraction was performed independently by two researchers with the use of a predefined template. Differences in extracted data were resolved by discussion between the two researchers. The quality of the included studies was assessed using the 'Quality Assessment of Diagnostic Accuracy Studies Tool' (QUADAS-2). True positives, false positives, true negatives, and false negatives were subtracted/calculated from the articles. The principal summary measures used to assess diagnostic accuracy were sensitivity, specificity, andarea under the receiver operating curve (AUC). Data was pooled according to analysis territory, reference standard and perfusion parameter.

RESULTS

Twenty-two articles were eligible based on the predefined study eligibility criteria. The pooled diagnostic accuracy for segment-, territory- and patient-based analyses showed good diagnostic performance with sensitivity of 0.88, 0.82, and 0.83, specificity of 0.72, 0.83, and 0.76 and AUC of 0.90, 0.84, and 0.87, respectively. In per territory analysis our results show similar diagnostic accuracy comparing anatomical (AUC 0.86(0.83-0.89)) and functional reference standards (AUC 0.88(0.84-0.90)). Only the per territory analysis sensitivity did not show significant heterogeneity. None of the groups showed signs of publication bias.

CONCLUSIONS

The clinical value of semi-quantitative and quantitative CMR perfusion analysis remains uncertain due to extensive inter-study heterogeneity and large differences in CMR perfusion acquisition protocols, reference standards, and methods of assessment of myocardial perfusion parameters. For wide spread implementation, standardization of CMR perfusion techniques is essential.

TRIAL REGISTRATION

CRD42016040176 .

Cardiac Computed Tomography: Before and After Cardiac Surgery

Cardiac computed tomography angiography (CCTA) is a noninvasive imaging technique that has been rapidly adopted into clinical practice. Over the past decade, technological advances have improved CCTA accuracy, and there is an increasing amount of data supporting its prognostic value in the assessment of coronary artery disease. Recently, "appropriate use criteria" has been used as a tool to minimize inappropriate testing and reduce patient exposure to unnecessary risk and inconclusive studies. This review will summarize the appropriate uses of CCTA in patients before and after cardiac surgery. Although the most common indication for CCTA is assessment of patency of native coronary arteries, other potential perioperative uses (eg, assessment of congenital heart disease, valvular heart disease, pericardial disease, myocardial disease, cardiac anatomy, bypass grafts, aortic disease, and cardiac masses) will be reviewed.

Safety of coronary CT angiography and functional testing for stable chest pain in the PROMISE trial: A randomized comparison of test complications, incidental findings, and radiation dose

BACKGROUND

Coronary computed tomography angiography (CTA) and functional testing strategies for stable chest pain yield similar outcomes; one aspect that may guide test choice is safety.

METHODS

We compared test safety (test complications, incidental findings, and effective radiation dose) between CTA and functional testing as-tested in PROMISE (PROspective Multicenter Imaging Study for Evaluation of Chest Pain). In the subgroup whose physicians intended nuclear stress over other functional tests if randomized to the functional arm, we compared radiation dose of CTA versus nuclear stress and identified characteristics associated with dose.

RESULTS

Of 9470 patients, none had major and <1% had minor complications (CTA: 0.8% [37/4633] vs. functional: 0.6% [27/4837]). CTA identified more incidental findings (11.6% [539/4633] vs. 0.7% [34/4837], p < 0.001), most commonly pulmonary nodules (9.4%, 437/4633). CTA had similar 90-day cumulative radiation dose to functional testing. However, in the subgroup whose physicians intended nuclear stress (CTA 3147; nuclear 3203), CTA had lower median index test (8.8 vs. 12.6 mSv, p < 0.001) and 90-day cumulative (11.6 vs. 13.1 mSv, p < 0.001) dose, independent of patient characteristics. The lowest nuclear doses employed 1-day Tc-99m protocols (12.2 mSv). The lowest CTA doses were at sites performing ≥500 CTAs/year (6.9 mSv) and with advanced (latest available) CT scanners (5.5 mSv).

CONCLUSION

Complications were negligibly rare for both CTA and functional testing. CTA detects more incidental findings. Compared to nuclear stress testing, CTA's lower radiation dose, independent of patient characteristics, makes it an attractive test choice. Radiation dose varies with imaging protocol, indicating opportunities to further reduce dose. (ClinicalTrials.gov number, NCT01174550).

Perceptions of patients and providers on myocardial perfusion imaging for asymptomatic patients, choosing wisely, and professional liability

Background

Despite efforts by professional societies to reduce low value care, many reports indicate that unnecessary tests, such as nuclear myocardial perfusion imaging (MPI), are commonly used in contemporary practice. The degree to which lack of awareness and professional liability concerns drive these behaviors warrants further study. We sought to investigate patient and provider perceptions about MPI in asymptomatic patients, the Choosing Wisely (CW) campaign, and professional liability concerns.

Methods

We administered an anonymous, paper-based survey with both discrete and open-response queries to subjects in multiple outpatient settings at our facilities. The survey was completed by 456 respondents including 342 patients and 114 physicians and advanced practice providers between May and August 2014. Our outcome was to compare patient and provider perceptions about MPI in asymptomatic patients and related factors.

Results

Patients were more likely than providers to report that MPI was justified for asymptomatic patients (e.g. asymptomatic with family history of heart disease 75% versus 9.2%, p < 0.0001). In free responses to the question “What would be an inappropriate reason for MPI?” many responses echoed the goals of CW (for example, “If you don’t have symptoms”, “If the test is too risky”, “For screening or in asymptomatic patients”). A minority of providers were aware of CW while even fewer patients were aware (37.2% versus 2.7%, p < 0.0001). Over one third of providers (38.9%) admitted to ordering MPI out of concern for professional liability including 48.3% of VA affiliated providers.

Conclusions

While some patients and providers are aware of the low value of MPI in patients without symptoms, others are enthusiastic to use it for a variety of scenarios. Concerns about professional liability likely contribute, even in the VA setting. Awareness of the Choosing Wisely campaign is low in both groups.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-017-2510-y) contains supplementary material, which is available to authorized users.

Utility of Imaging in Risk Stratification of Chest Pain in Women

OPINION STATEMENT

Recent decades have seen a growing recognition that the understanding of sex differences in cardiovascular disease (CVD) is vital to optimal diagnosis and management, particularly of women (Mosca et al. Circulation 124:2145-54, 2011). There is simultaneously an increasing appreciation of the multifactorial nature of ischemic heart disease (IHD) in many patients, in whom disease may extend beyond the epicardial coronaries. While obstructive coronary artery disease (CAD) remains underdiagnosed in women and still represents a major burden of disease, women also present with nonobstructive CAD more commonly than men (Patel et al. N Engl J Med 362:886-95, 2010). Indeed, microvascular dysfunction, coronary artery vasospasm, and coronary dissections contribute to a larger proportion of IHD in women than men (Bairey Merz et al. J Am Coll Cardiol 47:S21-9, 2006). Here, we review the symptom presentation of women with IHD and the noninvasive modalities used to risk stratify women with suspected IHD.

Comparison of the Appropriateness of Myocardial Perfusion Imaging in Men Versus Women

After a decade of appropriate use criteria publication, the degree and predictors of inappropriate use in women compared with men are not known. We conducted a retrospective cohort investigation comparing appropriateness categories (appropriate, maybe appropriate, and rarely appropriate) and cardiovascular outcomes in patients undergoing nuclear myocardial perfusion imaging (MPI) between June 2011 and September 2014 in predominantly inpatient setting. Of 1,475 cases reviewed, 747 (50.6%) were women, and they were more likely to have rarely appropriate use 118 (15.8%) than men 62 (8.5%), p <0.01, but they were less likely to have an abnormal MPI 102 (13.6%) than men 183 (25.6%), p <0.01. Subsequent angiography and revascularization rates were similar in women 38 (37.2%) and 5 (4.9%) and men 52 (28.4%) and 16 (8.7%), p = 0.12, p = 0.23, respectively. After median follow-up of 6 months, myocardial infarction rates were similar in women 3 (2.9%) and men 7 (3.8%), p = 0.67. Death rates were similar in women 8 (7.8%) and men 18 (9.8%), p = 0.57. The most common clinical scenario designated as rarely appropriate was in those with low pretest probability of coronary artery disease, who have interpretable electrocardiogram and are able to exercise in women 58 (49.1%) and men 21 (33.8%). In conclusion, based on the most contemporary appropriate use criteria publication, rarely appropriate use of MPI remains higher in women than that in men. This phenomenon was mostly observed in low-risk patients who can exercise.

Associated Risk of Malignancy in Patients with Cardiovascular Disease: Evidence and Possible Mechanism

Cardiovascular disease and malignancy are leading causes of morbidity and mortality. Increased risk of malignancy was identified in patients with cardiovascular disease, including patients with heart failure, heart failure after myocardial infarction, patients undergoing cardiac intervention, and patients after a thrombotic event. Common risk factors and biological pathways can explain this association and are explored in this review. Further research is needed to establish the causes of malignancy in this population and direct possible intervention.

New developments for the detection and treatment of cardiac vasculopathy

PURPOSE OF REVIEW

Cardiac allograft vasculopathy (CAV) is a major limitation to long-term survival after heart transplantation. Innovative new techniques to diagnose CAV have been applied to detect disease. This review will examine the current diagnostic and treatment options available to clinicians for CAV.

RECENT FINDINGS

Diagnostic modalities addressing the pathophysiology underlying CAV (arterial wall thickening and decreased coronary blood flow) improve diagnostic sensitivity when compared to traditional (angiography and dobutamine stress echocardiography) techniques.

SUMMARY

Limited options are available to prevent and treat CAV; however, progress has been made in making an earlier and more accurate diagnosis. Future research is needed to identify the optimal time to modify immunosuppression and investigate novel treatments for CAV.

Coronary CT angiography in the emergency department utilizing second and third generation dual source CT

BACKGROUND

Coronary computed tomography angiography (coronary CTA) allows efficient triage of low to intermediate risk patients with suspected acute coronary syndrome (ACS) in the emergency department (ED). Techniques for coronary CTA acquisition in the ED continue to evolve with the establishment of standardized scan protocols and the introduction of newer generations of CT hardware.

OBJECTIVES

To evaluate qualitative and quantitative image quality and radiation dose exposure of coronary CTA acquired on 2nd versus 3rd generation dual source CT (DSCT) scanners using a standardized institutional scan protocol designed for the ED.

METHODS

A retrospective observational case-control study was performed of 246 ED patients referred to coronary CTA with suspicion of ACS (56.5% male; mean age 53.3 ± 11.6 years) between October 2013 and August 2015.123 consecutive patients were scanned on 3rd generation DSCT, and a cohort of 123 patients matched by age, BMI and heart rate were identified who had undergone 2nd generation DSCT imaging utilizing the same standard clinical protocol. Qualitative and quantitative image quality parameters and radiation exposures were evaluated.

RESULTS

Qualitative image quality was significantly higher using 3rd generation DSCT as compared to 2nd generation (p < 0.001). Mean attenuation in the proximal coronary arteries was also significantly higher on 3rd generation DSCT than for 2nd generation (586 HU vs. 426 HU in the left main coronary artery (LM), p < 0.001). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values, however, were lower in 3rd generation DSCT than 2nd generation (SNR 11.2 [9.9-13.4] vs 13.5 [11.0-15.5] and CNR 12.4 [10.9-14.8] vs 15.2 [12.8-17.9] in the LM, p < 0.001). Median effective dose was also lower for 3rd generation DSCT than for 2nd generation (2.9 [2.3-5.0] mSv and 3.7 mSv [2.5-5.7], respectively) although this trend did not reach statistical significance (p = 0.065).

CONCLUSION

Qualitative image quality and mean CT attenuation values of the assessed coronary segments were significantly higher using 3rd generation DSCT. SNR and CNR were lower on 3rd generation DSCT, however this was accompanied by a trend toward lower radiation dose exposure when using the same standard institutional protocol.

Cardiac imaging: working towards fully-automated machine analysis & interpretation

INTRODUCTION

Non-invasive imaging plays a critical role in managing patients with cardiovascular disease. Although subjective visual interpretation remains the clinical mainstay, quantitative analysis facilitates objective, evidence-based management, and advances in clinical research. This has driven developments in computing and software tools aimed at achieving fully automated image processing and quantitative analysis. In parallel, machine learning techniques have been used to rapidly integrate large amounts of clinical and quantitative imaging data to provide highly personalized individual patient-based conclusions. Areas covered: This review summarizes recent advances in automated quantitative imaging in cardiology and describes the latest techniques which incorporate machine learning principles. The review focuses on the cardiac imaging techniques which are in wide clinical use. It also discusses key issues and obstacles for these tools to become utilized in mainstream clinical practice. Expert commentary: Fully-automated processing and high-level computer interpretation of cardiac imaging are becoming a reality. Application of machine learning to the vast amounts of quantitative data generated per scan and integration with clinical data also facilitates a move to more patient-specific interpretation. These developments are unlikely to replace interpreting physicians but will provide them with highly accurate tools to detect disease, risk-stratify, and optimize patient-specific treatment. However, with each technological advance, we move further from human dependence and closer to fully-automated machine interpretation.

Variability of radiation doses of cardiac diagnostic imaging tests: the RADIO-EVINCI study (RADIationdOse subproject of the EVINCI study)

BACKGROUND

Patients with coronary artery disease can accumulate significant radiation dose through repeated exposures to coronary computed tomographic angiography, myocardial perfusion imaging with single photon emission computed tomography or positron emission tomography, and to invasive coronary angiography. Aim of the study was to audit radiation doses of coronary computed tomographic angiography, single photon emission computed tomography, positron emission tomography and invasive coronary angiography in patients enrolled in the prospective, randomized, multi-centre European study-EVINCI (Evaluation of Integrated Cardiac Imaging for the Detection and Characterization of Ischemic Heart Disease).

METHODS

We reviewed 1070 tests (476 coronary computed tomographic angiographies, 85 positron emission tomographies, 310 single photon emission computed tomographies, 199 invasive coronary angiographies) performed in 476 patients (mean age 60 ± 9 years, 60% males) enrolled in 12 centers of the EVINCI. The effective doses were calculated in milli-Sievert (mSv) as median, interquartile range (IQR) and coefficient of variation of the mean.

RESULTS

Coronary computed tomographic angiography (476 exams in 12 centers) median effective dose was 9.6 mSv (IQR = 13.2 mSv); single photon emission computed tomography (310 exams in 9 centers) effective dose was 9.3 (IQR = 2.8); positron emission tomography (85 in 3 centers) effective dose 1.8 (IQR = 1.6) and invasive coronary angiography (199 in 9 centers) effective dose 7.4 (IQR = 7.3). Inter-institutional variability was highest for invasive coronary angiography (100%) and coronary computed tomographic angiography (54%) and lowest for single photon emission computed tomography (20%). Intra-institutional variability was highest for invasive coronary angiography (121%) and coronary computed tomographic angiography (115%) and lowest for single photon emission computed tomography (14%).

CONCLUSION

Coronary computed tomographic angiography and invasive coronary angiography doses vary substantially between and within centers. The variability in nuclear medicine procedures is substantially lower. The findings highlight the need to audit doses, to track cumulative exposures and to standardize doses for imaging techniques.

TRIAL REGISTRATION

The study protocol is available at https://www.clinicaltrials.gov/ (ClinicalTrials.gov Identifier: NCT00979199 ). Information provided on September 16, 2009.

Reducing Fluoroscopic Radiation Exposure During Endomyocardial Biopsy in Pediatric Transplant Recipients

Endomyocardial biopsy (EMB) with fluoroscopy is used for rejection surveillance in pediatric heart transplantation. Lowering frame rate may reduce radiation, but decreases temporal resolution and image quality. We undertook a quality initiative reducing frame rate from 10 frames per second (FPS) to 5 FPS. To assess whether lowering frame rate can reduce radiation exposure without compromising safety, data on EMBs from 9/2009 to 4/2013 without angiography or intervention were reviewed. Effective dose was calculated from dose area product (DAP) and fluoroscopy time. Complications were reviewed. Independent t test compared pre- and post-data and a general linear model were used to control for confounders. Paired t test of most proximate data was used for pts with EMB before and after our change. Eighty-six patients had 543 EMB. After adjusting for weight, attending, and presence of a fellow, the lower FPS group had a 60.3% reduction in DAP (p < 0.0001) and 53.8% drop in effective dose (p < 0.0001). Fluoroscopy time did not differ. Twenty-eight pts had EMBs both before and after the FPS change. Pair-wise analysis of this group demonstrated a 33% reduction in DAP (p < 0.05) and 37% drop in effective dose (p < 0.01), without difference in fluoroscopy time. No patient had an increase in TR > 1 grade by ECHO. There were no deaths or perforations. Lowering the frame rate reduces radiation exposure by >50% without compromising safety. Efforts to further minimize radiation exposure of this vulnerable population should be considered.

Gender Differences in Radiation Dose From Nuclear Cardiology Studies Across the World: Findings From the INCAPS Registry

OBJECTIVES

The aim of this study was to investigate gender-based differences in nuclear cardiology practice globally, with a particular focus on laboratory volume, radiation dose, protocols, and best practices.

BACKGROUND

It is unclear whether gender-based differences exist in radiation exposure for nuclear cardiology procedures.

METHODS

In a large, multicenter, observational, cross-sectional study encompassing 7,911 patients in 65 countries, radiation effective dose was estimated for each examination. Patient-level best practices relating to radiation exposure were compared between genders. Analysis of covariance was used to determine any difference in radiation exposure according to gender, region, and the interaction between gender and region. Linear, logistic, and hierarchical regression models were developed to evaluate gender-based differences in radiation exposure and laboratory adherence to best practices. The study also included the United Nations Gender Inequality Index and Human Development Index as covariates in multivariable models.

RESULTS

The proportion of myocardial perfusion imaging studies performed in women varied among countries; however, there was no significant correlation with the Gender Inequality Index. Globally, mean effective dose for nuclear cardiology procedures was only slightly lower in women (9.6 ± 4.5 mSv) than in men (10.3 ± 4.5 mSv; p < 0.001), with a difference of only 0.3 mSv in a multivariable model adjusting for patients' age and weight. Stress-only imaging was performed more frequently in women (12.5% vs. 8.4%; p < 0.001); however, camera-based dose reduction strategies were used less frequently in women (58.6% vs. 65.5%; p < 0.001).

CONCLUSIONS

Despite significant worldwide variation in best practice use and radiation doses from nuclear cardiology procedures, only small differences were observed between genders worldwide. Regional variations noted in myocardial perfusion imaging use and radiation dose offer potential opportunities to address gender-related differences in delivery of nuclear cardiology care.

Image noise reduction technology reduces radiation in a radial-first cardiac catheterization laboratory

BACKGROUND

Transradial coronary angiography (TRA) has been associated with increased radiation doses. We hypothesized that contemporary image noise reduction technology would reduce radiation doses in the cardiac catheterization laboratory in a typical clinical setting.

METHODS AND RESULTS

We performed a single-center, retrospective analysis of 400 consecutive patients who underwent diagnostic and interventional cardiac catheterizations in a predominantly TRA laboratory with traditional fluoroscopy (N=200) and a new image noise reduction fluoroscopy system (N=200). The primary endpoint was radiation dose (mGy cm²). Secondary endpoints were contrast dose, fluoroscopy times, number of cineangiograms, and radiation dose by operator between the two study periods. Radiation was reduced by 44.7% between the old and new cardiac catheterization laboratory (75.8mGycm²±74.0 vs. 41.9mGycm²±40.7, p<0.0001). Radiation was reduced for both diagnostic procedures (45.9%, p<0.0001) and interventional procedures (37.7%, p<0.0001). There was no statistically significant difference in radiation dose between individual operators (p=0.84). In multivariate analysis, radiation dose remained significantly decreased with the use of the new system (p<0.0001) and was associated with weight (p<0.0001), previous coronary artery bypass grafting (p<0.0007) and greater than 3 stents used (p<0.0004). TRA was used in 90% of all cases in both periods. Compared with a transfemoral approach (TFA), TRA was not associated with higher radiation doses (p=0.20).

CONCLUSIONS

Image noise reduction technology significantly reduces radiation dose in a contemporary radial-first cardiac catheterization clinical practice.

Radiobiology in Cardiovascular Imaging

The introduction of ionizing radiation in medicine revolutionized the diagnosis and treatment of disease and dramatically improved and continues to improve the quality of health care. Cardiovascular imaging and medical imaging in general, however, are associated with a range of radiobiologic effects, including, in rare instances, moderate to severe skin damage resulting from cardiac fluoroscopy. For the dose range associated with diagnostic imaging (corresponding to effective doses on the order of 10 mSv [1 rem]), the possible effects are stochastic in nature and largely theoretical. The most notable of these effects, of course, is the possible increase in cancer risk. The current review addresses radiobiology relevant to cardiovascular imaging, with particular emphasis on radiation induction of cancer, including consideration of the linear nonthreshold dose-response model and of alternative models such as radiation hormesis.

Automatic Valve Plane Localization in Myocardial Perfusion SPECT/CT by Machine Learning: Anatomic and Clinical Validation

Precise definition of the mitral valve plane (VP) during segmentation of the left ventricle for SPECT myocardial perfusion imaging (MPI) quantification often requires manual adjustment, which affects the quantification of perfusion. We developed a machine learning approach using support vector machines (SVM) for automatic VP placement. Methods: A total of 392 consecutive patients undergoing ^99mTc-tetrofosmin stress (5 min; mean ± SD, 350 ± 54 MBq) and rest (5 min; 1,024 ± 153 MBq) fast SPECT MPI attenuation corrected (AC) by CT and same-day coronary CT angiography were studied; included in the 392 patients were 48 patients who underwent invasive coronary angiography and had no known coronary artery disease. The left ventricle was segmented with standard clinical software (quantitative perfusion SPECT) by 2 experts, adjusting the VP if needed. Two-class SVM models were computed from the expert placements with 10-fold cross validation to separate the patients used for training and those used for validation. SVM probability estimates were used to compute the best VP position. Automatic VP localizations on AC and non-AC images were compared with expert placement on coronary CT angiography. Stress and rest total perfusion deficits and detection of per-vessel obstructive stenosis by invasive coronary angiography were also compared. Results: Bland-Altman 95% confidence intervals (CIs) for VP localization by SVM and experts for AC stress images (bias, 1; 95% CI, -5 to 7 mm) and AC rest images (bias, 1; 95% CI, -7 to 10 mm) were narrower than interexpert 95% CIs for AC stress images (bias, 0; 95% CI, -8 to 8 mm) and AC rest images (bias, 0; 95% CI, -10 to 10 mm) (P < 0.01). Bland-Altman 95% CIs for VP localization by SVM and experts for non-AC stress images (bias, 1; 95% CI, -4 to 6 mm) and non-AC rest images (bias, 2; 95% CI, -7 to 10 mm) were similar to interexpert 95% CIs for non-AC stress images (bias, 0; 95% CI, -6 to 5 mm) and non-AC rest images (bias, -1; 95% CI, -9 to 7 mm) (P was not significant [NS]). For regional detection of obstructive stenosis, ischemic total perfusion deficit areas under the receiver operating characteristic curve for the 2 experts (AUC, 0.79 [95% CI, 0.7-0.87]; AUC, 0.81 [95% CI, 0.73-0.89]) and the SVM (0.82 [0.74-0.9]) for AC data were the same (P = NS) and were higher than those for the unadjusted VP (0.63 [0.53-0.73]) (P < 0.01). Similarly, for non-AC data, areas under the receiver operating characteristic curve for the experts (AUC, 0.77 [95% CI, 0.69-0.89]; AUC, 0.8 [95% CI, 0.72-0.88]) and the SVM (0.79 [0.71-0.87]) were the same (P = NS) and were higher than those for the unadjusted VP (0.65 [0.56-0.75]) (P < 0.01). Conclusion: Machine learning with SVM allows automatic and accurate VP localization, decreasing user dependence in SPECT MPI quantification.

Stress-first single photon emission computed myocardial perfusion imaging

BACKGROUND

Myocardial perfusion imaging (MPI) with single photon emission tomography (SPET) is widely used in coronary artery disease evaluation. Recently major dosimetric concerns have arisen. The aim of this study was to evaluate if a pre-test scoring system could predict the results of stress SPET MPI, thus avoiding two radionuclide injections.

METHODS

All consecutive patients (n=309) undergoing SPET MPI during the first 6 months of 2014 constituted the study group. The scoring system is based on these characteristics: age >65 years (1 point), diabetes (2 points), typical chest pain (2 points), congestive heart failure (3 points), abnormal ECG (4 points), male gender (4 points), and documented previous CAD (5 points). The patients were divided on the basis of the prediction score into 3 classes of risk for an abnormal stress-first protocol.

RESULTS

An abnormal stress SPET MPI was present in 7/31 patients (23%) with a low risk score, in 24/90 (27%) with an intermediate score risk, and in 124/188 (66%) with an high score risk. ROC curve analysis showed good prediction of abnormal stress MPI.

CONCLUSIONS

Our results suggest an appropriate use of a pre-test clinical prediction formula of abnormal stress MPI in a routine clinical setting.

Ionizing radiation exposure in interventional cardiology: current radiation protection practice of invasive cardiology operators in Lithuania

Ionizing radiation management is among the most important safety issues in interventional cardiology. Multiple radiation protection measures allow the minimization of x-ray exposure during interventional procedures. Our purpose was to assess the utilization and effectiveness of radiation protection and optimization techniques among interventional cardiologists in Lithuania. Interventional cardiologists of five cardiac centres were interviewed by anonymized questionnaire, addressing personal use of protective garments, shielding, table/detector positioning, frame rate (FR), resolution, field of view adjustment and collimation. Effective patient doses were compared between operators who work with and without x-ray optimization. Thirty one (68.9%) out of 45 Lithuanian interventional cardiologists participated in the survey. Protective aprons were universally used, but not the thyroid collars; 35.5% (n  =  11) operators use protective eyewear and 12.9% (n  =  4) wear radio-protective caps; 83.9% (n  =  26) use overhanging shields, 58.1% (n  =  18)-portable barriers; 12.9% (n  =  4)-abdominal patient's shielding; 35.5% (n  =  11) work at a high table position; 87.1% (n  =  27) keep an image intensifier/receiver close to the patient; 58.1% (n  =  18) reduce the fluoroscopy FR; 6.5% (n  =  2) reduce the fluoro image detail resolution; 83.9% (n  =  26) use a 'store fluoro' option; 41.9% (N  =  13) reduce magnification for catheter transit; 51.6% (n  =  16) limit image magnification; and 35.5% (n  =  11) use image collimation. Median effective patient doses were significantly lower with x-ray optimization techniques in both diagnostic and therapeutic interventions. Many of the ionizing radiation exposure reduction tools and techniques are underused by a considerable proportion of interventional cardiology operators. The application of basic radiation protection tools and techniques effectively reduces ionizing radiation exposure and should be routinely used in practice.

The influence of clopidogrel on ischemia diagnosed by myocardial perfusion stress testing

BACKGROUND

Clopidogrel is a platelet adenosine receptor antagonist which can influence coronary vascular tone and thus can potentially interfere with myocardial perfusion imaging. We investigated whether clopidogrel can hamper the diagnosis of ischemia in patients undergoing myocardial perfusion testing.

METHODS

Data from a database of 6349 myocardial perfusion stress tests were analyzed. Using a propensity analysis, patients who were taking clopidogrel were compared with patients not taking clopidogrel for the presence of reversible perfusion defects on myocardial single-photon emission computed tomography scans.

RESULTS

Of the 6349 tests, the stress technique was adenosine in 2713 patients and exercise in 3636. At the time of the stress test, 277 (4.3%) of the patients were taking clopidogrel. The odds ratio (OR) for patients taking clopidogrel to have a reversible perfusion defect was 2.75 (95% confidence interval [CI] 2.09-3.62; P < .01). After adjusting for the propensity to take clopidogrel, the OR was 1.06 (CI 0.76-1.49; P = .73) for patients undergoing adenosine stress tests and 1.60 (CI 0.85-3.00; P = .14) for patients undergoing exercise stress tests.

CONCLUSIONS

We found no evidence that the use of clopidogrel decreases the likelihood of ischemia on adenosine or exercise stress myocardial perfusion scans.

Women and Chest Pain: Recognizing the Different Faces of Angina in the Emergency Department

Emergency departments (ED) in the United States see over eight million cases of chest pain annually. While a cardinal symptom of acute coronary syndrome (ACS), multiple emergent and non-emergent causes can attribute to chest pain. This case-based perspective describes the different sex-specific causes of angina seen in ED patients. Once coronary artery disease (CAD) is ruled out with standard protocols, microvascular dysfunction is perhaps the most prevalent but under-diagnosed cause of non-CAD related angina in ED patients. Additional causes include coronary artery spasm, coronary artery dissection, coronary artery endothelial dysfunction and myocardial bridging. Non-CAD related angina is associated with persistent chest pain causing poor function, quality of life, and recidivism. Clinicians should consider additional diagnostics to routinely screen for non-CAD related causes of angina in patients with recurrent chest pain. Future work is needed to better define the epidemiological, clinical, biological, and genetic correlates of microvascular dysfunction in these patients.

Monitoring Ionizing Radiation Exposure for Cardiotoxic Effects of Breast Cancer Treatment

Serial assessments of left ventricular ejection fraction (LVEF) are customary in patients with breast cancer receiving trastuzumab. Radionuclide angiography (RNA) is often used; however, a typical monitoring schedule could include 5 scans in a year. We evaluated the proportion of imaging-related ionizing radiation attributable to RNA in 115 patients with breast cancer, from 3 medical centers in the United States, Ireland, and Japan, who completed 12 months of trastuzumab treatment. Estimated radiation dose (ERD) was used to calculate exposure associated with imaging procedures spanning the 18 months before and after trastuzumab therapy. In addition, 20 cardiologists and oncologists from participating centers were surveyed for their opinions regarding the contribution of RNA to overall radiation exposure during trastuzumab treatment. When RNA was used to monitor LVEF, the mean ERD from imaging was substantial (34 ± 24.3 mSv), with the majority attributable solely to RNA (24.7 ± 14.8 mSv, 72.6%). Actual ERD associated with RNA in this population differed significantly from the perception in surveyed cardiologists and oncologists; 70% of respondents believed that RNA typically accounted for 0% to 20% of overall radiation exposure from imaging; RNA actually accounted for more than 70% of ERD. In conclusion, RNA was used to monitor LVEF in most patients in this cohort during and after trastuzumab therapy. This significantly increased ERD and accounted for a greater proportion of radiation than that perceived by surveyed physicians. ERD should be taken into account when choosing a method of LVEF surveillance. Alternative techniques that do not use radiation should be strongly considered.

A new hand-held microfluidic cytometer for evaluating irradiation damage by analysis of the damaged cells distribution

Space radiation brings uneven damages to cells. The detection of the distribution of cell damage plays a very important role in radiation medicine and the related research. In this paper, a new hand-held microfluidic flow cytometer was developed to evaluate the degree of radiation damage of cells. The device we propose overcomes the shortcomings (e.g., large volume and high cost) of commercial flow cytometers and can evaluate the radiation damage of cells accurately and quickly with potential for onsite applications. The distribution of radiation-damaged cells is analyzed by a simultaneous detection of immunofluorescence intensity of γ-H2AX and resistance pulse sensor (RPS) signal. The γ-H2AX fluorescence intensity provides information of the degree of radiation damage in cells. The ratio of the number of cells with γ-H2AX fluorescence signals to the total numbers of cells detected by RPS indicates the percentage of the cells that are damaged by radiation. The comparison experiment between the developed hand-held microfluidic flow cytometer and a commercial confocal microscope indicates a consistent and comparable detection performance.

Reduction in Radiation Exposure through a Stress Test Algorithm in an Emergency Department Observation Unit

INTRODUCTION

Clinicians are urged to decrease radiation exposure from unnecessary medical procedures. Many emergency department (ED) patients placed in an observation unit (EDOU) do not require chest pain evaluation with a nuclear stress test (NucST). We sought to implement a simple ST algorithm that favors non-nuclear stress test (Non-NucST) options to evaluate the effect of the algorithm on the proportion of patients exposed to radiation by comparing use of NucST versus Non-NucST pre- and post-algorithm.

METHODS

An ST algorithm was introduced favoring Non-NucST and limiting NucST to a subset of EDOU patients in October 2008. We analyzed aggregate data before (Jan-Sept 2008, period 1) and after (Jan-Sept 2009 and Jan-Sept 2010, periods 2 and 3 respectively) algorithm introduction. A random sample of 240 EDOU patients from each period was used to compare 30-day major adverse cardiac events (MACE). We calculated confidence intervals for proportions or the difference between two proportions.

RESULTS

A total of 5,047 STs were performed from Jan-Sept 2008-2010. NucST in the EDOU decreased after algorithm introduction from period 1 to 2 (40.7%, 95% CI [38.3-43.1] vs. 22.1%, 95% CI [20.1-24.1]), and remained at 22.1%, 95% CI [20.3-24.0] in period 3. There was no difference in 30-day MACE rates before and after algorithm use (0.1% for period 1 and 3, 0% for period 2).

CONCLUSION

Use of a simple ST algorithm that favors non-NucST options decreases the proportion of EDOU chest pain patients exposed to radiation exposure from ST almost 50% by limiting NucST to a subset of patients, without a change in 30-day MACE.

Clinical use of quantitative cardiac perfusion PET: rationale, modalities and possible indications. Position paper of the Cardiovascular Committee of the European Association of Nuclear Medicine (EANM)

Until recently, PET was regarded as a luxurious way of performing myocardial perfusion scintigraphy, with excellent image quality and diagnostic capabilities that hardly justified the additional cost and procedural effort. Quantitative perfusion PET was considered a major improvement over standard qualitative imaging, because it allows the measurement of parameters not otherwise available, but for many years its use was confined to academic and research settings. In recent years, however, several factors have contributed to the renewal of interest in quantitative perfusion PET, which has become a much more readily accessible technique due to progress in hardware and the availability of dedicated and user-friendly platforms and programs. In spite of this evolution and of the growing evidence that quantitative perfusion PET can play a role in the clinical setting, there are not yet clear indications for its clinical use. Therefore, the Cardiovascular Committee of the European Association of Nuclear Medicine, starting from the experience of its members, decided to examine the current literature on quantitative perfusion PET to (1) evaluate the rationale for its clinical use, (2) identify the main methodological requirements, (3) identify the remaining technical difficulties, (4) define the most reliable interpretation criteria, and finally (5) tentatively delineate currently acceptable and possibly appropriate clinical indications. The present position paper must be considered as a starting point aiming to promote a wider use of quantitative perfusion PET and to encourage the conception and execution of the studies needed to definitely establish its role in clinical practice.

Patient and staff doses in paediatric interventional cardiology derived from experimental measurements with phantoms

The aim of this paper was to determine experimentally the entrance surface air kerma (ESAK) and kerma-area product (KAP) levels to patients and scatter doses at the cardiologist's eyes during paediatric interventional cardiology (IC) procedures for Chile, on the basis of measurements taken from X-ray systems characterization for different thicknesses of polymethyl methacrylate, together with the average values of fluoroscopy time and number of cine frames for ten paediatric IC procedures. The range of cumulative ESAK values when the different clinical procedures were simulated was from 2 to 1100 mGy. KAP values ranged from 0.30 to 150 Gy cm(2). Scatter doses at cardiologist's eyes for the simulated procedures ranged from 0.20 to 116 µSv per procedure. Large differences between the X-ray systems were found in our study. Standardized guidelines in terms of X-ray system setting and protocols should be developed for hospitals that perform paediatric IC procedures in Chile.