Stress-only Imaging Research Articles

Accurate and efficient rapid acquisition early post-injection stress-first CZT SPECT myocardial perfusion imaging with tetrofosmin and attenuation correction.

Myocardial perfusion imaging (MPI) protocols have not changed significantly despite advances in instrumentation and software. We compared an early post-injection, stress-first SPECT protocol to standard delayed imaging. 95 patients referred for SPECT MPI were imaged upright and supine on a Spectrum Dynamics D-SPECT CZT system with CT attenuation correction. Patients received injection of 99mTc tetrofosmin at peak of regadenoson stress and were imaged. Early post-stress (mean 17 ± 2 minutes) and Standard 1-h delay (mean 61 ± 13 min). Three blinded readers evaluated images for overall interpretation, perceived need for rest imaging, image quality, and reader confidence. Laboratory efficiency was also evaluated. Blinded readers had the same response for the need for rest in 77.9% of studies. Studies also had the same interpretation in 89.5% of studies. Reader confidence was high (86.0% (Early) and 90.3% (Standard p=0.52. Image quality was good or excellent in 87.4% Early vs 96.8% Standard (p=0.09). Time between patient check-in and end of stress imaging was 104 ± (Standard) to 60 ± 18 minutes (Early) (p<0.001). Early post-injection stress-only imaging using CZT SPECT/CT appears promising with Tc-99m tetrofosmin with similar image quality, reader confidence, diagnosis, and need for a rest scan.

Prediction of multivessel coronary artery disease and candidates for stress-only imaging using multivariable models with myocardial perfusion imaging

PurposeSelecting patients with coronary multivessel disease (MVD) or no stenosis using myocardial perfusion imaging (MPI) is challenging. We aimed to create a model to predict MVD using a combination of quantitative MPI values and background factors of patients. We also assessed whether patients in the same database could be selected who do not require rest studies (stress-only imaging).MethodsWe analyzed data from 1001 patients who had been assessed by stress MPI at 12 centers and 463 patients who had not undergone revascularization in Japan. Quantitative values based on MPI were obtained using cardioREPO software, which included myocardial perfusion defect scores, left ventricular ejection fractions and volumes. Factors in MPI and clinical backgrounds that could predict MVD were investigated using univariate and multivariate analyses. We also investigated whether stress data alone could predict patients without coronary stenosis to identify candidates for stress-only imaging.ResultsWe selected summed stress score (SSS), rest end-diastolic volume, and hypertension to create a predictive model for MVD. A logistic regression model was created with an area under the receiver operating characteristics curve (AUC) of 0.825. To more specifically predict coronary three-vessel disease, the AUC was 0.847 when SSS, diabetes, and hypertension were selected. The mean probabilities of abnormality based on the MVD prediction model were 12%, 24%, 40%, and 51% for no-, one-, two-, and three-vessel disease, respectively (p < 0.0001). For the model to select patients with stress-only imaging, the AUC was 0.78 when the model was created using SSS, stress end-systolic volume and the number of risk factors (diabetes, hypertension, chronic kidney disease, and a history of smoking).ConclusionA model analysis combining myocardial SPECT and clinical data can predict MVD, and can select patients for stress-only tests. Our models should prove useful for clinical applications.

Optimal Protocol of Myocardial Perfusion Imaging for Reduction of Radiation Exposure.

The Japanese Circulation Society (JCS) 2021 guideline on radiation safety in cardiology was updated based on the eight best practices for myocardial perfusion single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI), which was determined by panels of international atomic energy agency (IAEA) nuclear cardiology protocols cross-sectional study (INCAPS). Although the guideline recommends to avoid too much 201Tl or 201Tl/99mTc dual-isotope protocol, the utilization rate of 201Tl for SPECT-MPI in Japan is considerably high compared to other countries. In Japan, protocols using 99mTc should be appropriately promoted based on the guideline to reduce radiation exposure in SPECT-MPI. Among the eight practices, stress-only imaging is considered to be a useful strategy that contributes to a significant reduction in radiation exposure, and hybrid assessment in combination with rest computed tomography (CT)-MPI is one of the practical application methods.

Stress only myocardial perfusion imaging - comparison of hospitalized and outpatient patients

Abstract Funding Acknowledgements Type of funding sources: None. Background In selected patients, stress-only myocardial perfusion imaging (MPI) has been proposed as an alternative to rest-stress MPI to reduce radiation exposure and enhance laboratory efficiency. The use of attenuation correction improves the diagnostic accuracy of stress-only imaging. However, criteria for selecting appropriate patients for stress-first imaging protocol are not uniform. There is limited data about stress-only MPI in hospitalized patients. The purpose of this study was to compare the proportion of suitable hospitalized and outpatient patients with normal MPI on a routine two-day protocol for stress-only MPI. Methods In a retrospective longitudinal cohort study, stress scintigrams (with and without attenuation correction) of consecutive hospitalized and outpatient patients who underwent MPI at our department by a routine two-day protocol and had a normal MPI were visually and semi-quantitatively re-examined. Patients with summed stress score 0 or 1 were considered as candidates for stress-only MPI. We also obtained data on the patients" clinical characteristics and their treatment. Results We studied 178 patients (mean age 68.8 ± 13.4 years, 89 hospitalized, 89 outpatient patients, 55.6 % female). Hospitalized patients were significantly older than outpatient participants (72.4 ± 13.0 vs. 65 ± 12.9 years, p &amp;lt; 0.001) with no significant differences in risk factors and clinical characteristics. Proportion of inpatients and outpatients suitable for stress-only MPI with and without attenuation correction is shown on Figure 1. There was no significant difference in stress-only MPI with and without attenuation correction between hospitalized and outpatient patients (Figure 1). 9.1% of patients in whom stress only MPI was possible had known coronary artery disease, whereas it was present in 25.0% of patients in whom stress-only MPI was not possible (p = 0.004). By using attenuation correction stress-only MPI could be performed in 54% of patients without known coronary artery disease. There was no difference between hospitalized patients and outpatients (52% vs. 56%, p = 0.700). Absence of coronary artery disease turned out as the only independent prognostic factor for application of stress-only MPI (odds ratio 3.433, 95% confidence interval 1.44-8.17, p = 0.003). There was no influence of hospitalization on the application of stress-only MPI. Conclusions When we choose the right patients (especially those without a known coronary artery disease) and use modern cameras that enable attenuation correction, we can perform stress-only MPI in 50% of patients with a normal MPI result. The same approach can be used for outpatients and inpatients.

A Clinical Tool to Identify Candidates for Stress-First Myocardial Perfusion Imaging

ObjectivesThis study sought to develop a clinical model that identifies a lower-risk population for coronary artery disease that could benefit from stress-first myocardial perfusion imaging (MPI) protocols and that can be used at point of care to risk stratify patients. BackgroundThere is an increasing interest in stress-first and stress-only imaging to reduce patient radiation exposure and improve patient workflow and experience. MethodsA secondary analysis was conducted on a single-center cohort of patients undergoing single-photon emission computed tomography (SPECT) and positron emission tomography (PET) studies. Normal MPI was defined by the absence of perfusion abnormalities and other ischemic markers and the presence of normal left ventricular wall motion and left ventricular ejection fraction. A model was derived using a cohort of 18,389 consecutive patients who underwent SPECT and was validated in a separate cohort of patients who underwent SPECT (n = 5,819), 1 internal cohort of patients who underwent PET (n=4,631), and 1 external PET cohort (n = 7,028). ResultsFinal models were made for men and women and consisted of 9 variables including age, smoking, hypertension, diabetes, dyslipidemia, typical angina, prior percutaneous coronary intervention, prior coronary artery bypass graft, and prior myocardial infarction. Patients with a score ≤1 were stratified as low risk. The model was robust with areas under the curve of 0.684 (95% confidence interval [CI]: 0.674 to 0.694) and 0.681 (95% CI: 0.666 to 0.696) in the derivation cohort, 0.745 (95% CI: 0.728 to 0.762) and 0.701 (95% CI: 0.673 to 0.728) in the SPECT validation cohort, 0.672 (95% CI: 0.649 to 0.696) and 0.686 (95% CI: 0.663 to 0.710) in the internal PET validation cohort, and 0.756 (95% CI: 0.740 to 0.772) and 0.737 (95% CI: 0.716 to 0.757) in the external PET validation cohort in men and women, respectively. Men and women who scored ≤1 had negative likelihood ratios of 0.48 and 0.52, respectively. ConclusionsA novel model, based on easily obtained clinical variables, is proposed to identify patients with low probability of having abnormal MPI results. This point-of-care tool may be used to identify a population that might qualify for stress-first MPI protocols.

Drivers of radiation dose reduction with myocardial perfusion imaging: A large health system experience

BackgroundDespite increasing emphasis on reducing radiation exposure from myocardial perfusion imaging (MPI), the use of radiation-sparing practices (RSP) at nuclear laboratories remains limited. Defining real-world impact of RSPs on effective radiation dose (E) can potentially further motivate their adoption. MethodsMPI studies performed between 1/2010 and 12/2016 within a single health system were included. Mean E was compared between sites with ‘basic’ RSP (defined as elimination of thallium-based protocols and use of stress-only (SO) imaging on conventional single photon emission computed tomography (SPECT) cameras) and those with ‘advanced’ capabilities (sites that additionally used solid-state detector (SSD) SPECT cameras, advanced post-processing software (APPS) or positron emission tomography (PET) imaging), after matching patients by age, gender, and weight. Contributions of individual RSP to E reduction were determined using multiple linear regression after adjusting for factors affecting tracer dose. ResultsAmong 55,930 MPI studies performed, the use of advanced RSP was associated with significantly lower mean E compared to basic RSP (7 ± 5.6 mSv and 16 ± 5.4 mSv, respectively; P < 0.001), with a greater likelihood of achieving E < 9 mSv (65.7% vs. 10.8%, respectively; OR 15.8 [95% CI 14 to 17.8]; P < 0.0001). Main driver of E reduction was SO-SSD SPECT (mean reduction = 11.5 mSv), followed by use of SO-SPECT + APPS (mean reduction = 10.1 mSv), ;ET (mean reduction = 9.7 mSv); and elimination of thallium protocols (mean reduction = 9.1 mSv); P < 0.0001 for all comparisons. ConclusionIn a natural experiment with implementation of radiation-saving practices at a large health system, stress-only protocols used in conjunction with modern SPECT technologies, the use of PET and elimination of thallium-based protocols were associated with greatest reductions in radiation dose. Availability of several approaches to dose reduction within a health system can facilitate achievement of targeted radiation benchmarks in a greater number of performed studies.

Automated Interpretation of Myocardial Perfusion Images with Multilayer Perceptron Network as a Decision Support System

Aim: Bull's eye pattern recognition with artificial neural networks (ANNs) has the potential to assist interpretation of myocardial perfusion images (MPIs). We aimed to develop a model for interpretation of MPI based on the clinical variables and imaging data. Materials and Methods: The study included 208 patients referred to the department of nuclear medicine for 2-day stress-rest ECG-gated MPI. Several ANN models were designed with the following input variables: average count of 20 segments of the bull's eye images of stress and rest MPIs, gender, the constellation of coronary artery disease risk factors and scintigraphic cardiac ejection fraction. The procedure was repeated excluding the data of the rest phase scan. Data of 150 subjects were used for training, 21 subjects for cross-validation and 37 subjects for final operation testing. Several ANN models were examined with different hidden layers and processing elements and functions. The target output variable was the conclusion of the nuclear physician (i.e., normal vs. abnormal scan). Results: A multilayer perceptron (MLP) with two hidden layers trained with both stress and rest data demonstrated the best performance to classify the normal and abnormal MPIs. It showed an overall accuracy of 91.9%, sensitivity of 91.3% and specificity of 92.9%. The accuracy of the similar MLP trained using stress-only myocardial perfusion images reduced to 67.6%. Conclusion: The automated interpretation of MPIs with a 2 hidden layer MLP trained with stress and rest images could be an accurate support system either for the interpretation or quality assurance.

Analysis of stress-only imaging, comparing upright and supine CZT camera acquisition to conventional gamma camera images with and without attenuation correction, with coronary angiography as a reference

BackgroundDiagnostic performance of stress-only imaging using a Cadmium-Zinc-Telluride (CZT) camera has not been directly compared in the same patients to stress-only attenuation-corrected conventional Anger camera images. Methods112 subjects with correlative coronary angiographic data and 40 subjects with <5% pre-test likelihood of coronary disease completed attenuation-corrected stress-only images on a conventional Anger camera and uncorrected upright and supine stress images on a CZT camera. Two readers provided independent, blinded interpretations of stress-only images. ResultsUpright and supine stress-only CZT images and attenuation-corrected Anger camera images provided similar positive (reader 1/reader 2, 50.0%/44.1% vs 46.4%/51.9%) and negative (66.7%/64.0% vs 67.9%/67.7%) predictive values (all P = NS) for obstructive coronary artery disease; however, the sensitivity was higher (81.3% vs 58.3%, P = .05), specificity lower (29.7% vs 50.0%, P = .005), and normalcy rate lower (87.5% vs 100%, P = .025) with attenuation-corrected Anger camera images for the first reader with no significant differences between cameras for the second reader. ConclusionsStress-only upright and supine CZT imaging was non-inferior statistically to attenuation-corrected stress-only Anger camera imaging. Nevertheless, stress-only CZT imaging may be associated with reduced diagnostic sensitivity for some readers compared to attenuation-corrected Anger camera images, which may be less acceptable clinically compared to stress plus rest images.

USVAH Study Demonstrates Statistically Significant Improvement in Diagnosis and Care of U.S Veterans Using FMTVDM – FHRWW©℗ “Quantitative” Nuclear Imaging. The Era of Truly Quantitative Stress- First, Stress-Only Imaging has begun!

Background: Myocardial perfusion imaging (MPI) has evolved over the last several decades with improvements in equipment and isotopes. Despite these limitations sensitivity and specificity of this study remains 65%-85% principally due to “qualitative” interpretation of the results. Numerous investigators have recommended changes in protocols and quantification of data to increase the diagnostic accuracy of this non-invasive physiologic test. Initial investigations have demonstrated the ability to “quantitatively” measure isotope redistribution with planar, SPECT and PET using FMTVDM©℗. This study was designed to compare the diagnostic and treatment outcomes of U.S. Veterans undergoing conventional “stress-rest” “qualitative” imaging using Technetium 99m isotopes (Sestamibi and Myoview) compared with FMTVDM©℗ “quantification” isotope redistribution using a single dose of the isotope.Methods: Forty-one U.S. Veterans were studied using pharmacologic and exercise stress approaches with either Sestamibi or Myoview following routine MPI Imaging protocols compared with FMTVDM©℗. The results were compared with coronary angiography.Result: Angiographic coronary artery disease (CAD) was defined using both 50% and 70% diameter narrowing/ stenosis (%DS). Accuracy of a “qualitative” (yes/no) test in the determination of the presence or absence of CAD is measured by the ability of the test to find CAD when present (sensitivity) and to show that CAD is not present (specificity) when absent, based upon the arbitrarily assigned value for %DS. The sensitivity, specificity and accuracy of “qualitative” MPI assessment of 50% DS CAD was 50.0%, 88.2% and 70.7% for the left coronary artery system and 29.2%, 64.7% and 43.9% respectively for the right coronary artery system. These values improved to 59.1%, 89.5% and 73.2% for the left coronary artery system and 64.3%, 85.2% and 78.0% respectively for the right coronary artery system when 70%DS was used as the cutoff for CAD. No differences noted between either of the technetium 99m isotopes or cameras used for either the “qualitative” or “quantitative” (FMTVDM©℗) methods. FMTVDM©℗ provides the First Ever “quantitative” Nuclear Cardiology MPI test, which consequently defines CAD not on a yes/no basis, but “quantitatively.” As such, the accuracy of FMTVDM©℗ must be compared first to a “quantitative” measure which is known; viz. isotope decay using TFM. Results of FMTVDM©℗ is then not simply a yes/no result, but rather a “quantitative” value which places the “extent” of CAD on a measured continuum much as a coronary angiogram would, specifically a quantitative coronary angiogram (QCA). FMTVDM©℗ demonstrated a statistically significant relationship between CAD and %DS (r=0.75, p < 0.001).Conclusion: Modern Nuclear Cameras have relied completely upon “quality” control methods, which do exactly that; they provide for “qualitative” control but not “quantitative” control. The accuracy of the cameras ability to correctly count the resulting scintillations from which “quantitative” analysis and even “qualitative” images are displayed for clinician interpretation are dependent, has never been established or used in either the experimental or clinical areas of Medicine. This study demonstrated the importance of first using TFM from the FMTVDM©℗ for “quantitative” camera calibration and correction prior to conducting MPI. Even with the correction of the “quantitative” errors in the Nuclear Cameras, errors in “qualitative” MPI resulted in a conservative estimate of misdiagnosis of CAD 35% of the time. These errors result in potential life threatening CAD being missed as demonstrated here. This same CAD is accurately measured using the new “quantitative” MPI test (FMTVDM©℗), which accurately “quantify” the extent of CAD. FMTVDM©℗ provides the first “quantitative” Nuclear Cardiology and Medicine test, ushering in the era of “machine learning” and “quantitative” Nuclear Cardiology and Medicine providing accurate, reproducible measurement of CAD in less time and with less radiation than the prior “qualitatively” applied method of “physician interpretation” of CAD, reducing healthcare costs and improving patient throughput and clinical management.

Myocardial perfusion imaging in women for the evaluation of stable ischemic heart disease—state-of-the-evidence and clinical recommendations

This document from the American Society of Nuclear Cardiology represents an updated consensus statement on the evidence base of stress myocardial perfusion imaging (MPI), emphasizing new developments in single-photon emission tomography (SPECT) and positron emission tomography (PET) in the clinical evaluation of women presenting with symptoms of stable ischemic heart disease (SIHD). The clinical evaluation of symptomatic women is challenging due to their varying clinical presentation, clinical risk factor burden, high degree of comorbidity, and increased risk of major ischemic heart disease events. Evidence is substantial that both SPECT and PET MPI effectively risk stratify women with SIHD. The addition of coronary flow reserve (CFR) with PET improves risk detection, including for women with nonobstructive coronary artery disease and coronary microvascular dysfunction. With the advent of PET with computed tomography (CT), multiparametric imaging approaches may enable integration of MPI and CFR with CT visualization of anatomical atherosclerotic plaque to uniquely identify at-risk women. Radiation dose-reduction strategies, including the use of ultra-low-dose protocols involving stress-only imaging, solid-state detector SPECT, and PET, should be uniformly applied whenever possible to all women undergoing MPI. Appropriate candidate selection for stress MPI and for post-MPI indications for guideline-directed medical therapy and/or invasive coronary angiography are discussed in this statement. The critical need for randomized and comparative trial data in female patients is also emphasized.

Implementation of stress-only imaging: What will it take?

Implementation of stress-only imaging: What will it take?

Opportunities for improvement on current nuclear cardiology practices and radiation exposure in Latin America: Findings from the 65-country IAEA Nuclear Cardiology Protocols cross-sectional Study (INCAPS)

BackgroundComparison of Latin American (LA) nuclear cardiology (NC) practice with that in the rest of the world (RoW) will identify areas for improvement and lead to educational activities to reduce radiation exposure from NC. Methods and ResultsINCAPS collected data on all SPECT and PET procedures performed during a single week in March-April 2013 in 36 laboratories in 10 LA countries (n = 1139), and 272 laboratories in 55 countries in RoW (n = 6772). Eight “best practices” were identified a priori and a radiation-related Quality Index (QI) was devised indicating the number used. Mean radiation effective dose (ED) in LA was higher than in RoW (11.8 vs 9.1 mSv, p < 0.001). Within a populous country like Brazil, a wide variation in laboratory mean ED was found, ranging from 8.4 to 17.8 mSv. Only 11% of LA laboratories achieved median ED <9 mSv, compared to 32% in RoW (p < 0.001). QIs ranged from 2 in a laboratory in Mexico to 7 in a laboratory in Cuba. Three major opportunities to reduce ED for LA patients were identified: (1) more laboratories could implement stress-only imaging, (2) camera-based methods of ED reduction, including prone imaging, could be more frequently used, and (3) injected activity of 99mTc could be adjusted reflecting patient weight/habitus. ConclusionsOn average, radiation dose from NC is higher in LA compared to RoW, with median laboratory ED <9 mSv achieved only one third as frequently as in RoW. Opportunities to reduce radiation exposure in LA have been identified and guideline-based recommendations made to optimize protocols and adhere to the “as low as reasonably achievable” (ALARA) principle.

Sequential SPECT/CT imaging for detection of coronary artery disease in a large cohort: evaluation of the need for additional imaging and radiation exposure

BackgroundPerforming both single photon emission computerized tomography (SPECT) and coronary computed tomography angiography (CCTA) in patients suspected for coronary artery disease (CAD) leads to increased radiation exposure. We evaluated the need for additional imaging and following implications for radiation exposure of a sequential SPECT/computed tomography (CT) algorithm. Methods and Results5018 consecutive patients without history of CAD were referred for stress-first SPECT and coronary artery calcium (CAC) scoring. If stress SPECT was abnormal, additional rest SPECT and, if feasible, CCTA were acquired. Stress SPECT was normal in 2617 patients (52%). CCTA was not performed in 1289 of the 2401 patients referred for additional imaging (54%), mainly because of severe CAC (47%) or fast/irregular heart rate (22%). 642 patients with abnormal SPECT underwent CCTA, which excluded significant CAD in 378 patients (59%). Mean radiation dose was 4.5 ± 0.3 mSv for stress-only imaging and 13.2 ± 3.3 mSv for additional imaging (P < 0.001). ConclusionsHalf of the patients do not require additional imaging in our sequential SPECT/CT algorithm, which is accompanied with low radiation exposure. CCTA cannot be performed in half of the patients who undergo additional imaging because of (relative) contra-indications. CCTA is able to correct for false-positive SPECT findings in our algorithm.

Nuclear Cardiology Practice in Asia: Analysis of Radiation Exposure and Best Practice for Myocardial Perfusion Imaging - Results From the IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS).

This paper examines the current status of radiation exposure to patients in myocardial perfusion imaging (MPI) in Asia.Methods and Results:Laboratories voluntarily provided information on MPI performed over a 1-week period. Eight best practice criteria regarding MPI were predefined by an expert panel. Implementation of ≥6 best practices (quality index [QI] ≥6) was pre-specified as a desirable goal for keeping radiation exposure at a low level. Radiation effective dose (ED) in 1,469 patients and QI of 69 laboratories in Asia were compared against data from 239 laboratories in the rest of the world (RoW). Mean ED was significantly higher in Asia (11.4 vs. 9.6 mSv; P<0.0001), with significantly lower doses in South-East vs. East Asia (9.7 vs. 12.7 mSv; P<0.0001). QI in Asia was lower than in RoW. In comparison with RoW, Asian laboratories used thallium more frequently, used weight-based technetium dosing less frequently, and trended towards a lower rate of stress-only imaging. MPI radiation dose in Asia is higher than that in the RoW and linked to less consistent use of laboratory best practices such as avoidance of thallium, weight-based dosing, and use of stress-only imaging. Given that MPI is performed in Asia within a diverse array of medical contexts, laboratory-specific adoption of best practices offers numerous opportunities to improve quality of care.

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

ObjectivesThe 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. BackgroundIt is unclear whether gender-based differences exist in radiation exposure for nuclear cardiology procedures. MethodsIn 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. ResultsThe 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). ConclusionsDespite 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.

Estimating the Reduction in the Radiation Burden From Nuclear Cardiology Through Use of Stress-Only Imaging in the United States and Worldwide.

Estimating the Reduction in the Radiation Burden From Nuclear Cardiology Through Use of Stress-Only Imaging in the United States and Worldwide.

Nuclear cardiology practice and associated radiation doses in Europe: results of the IAEA Nuclear Cardiology Protocols Study (INCAPS) for the 27 European countries.

PurposeNuclear cardiology is widely used to diagnose coronary artery disease and to guide patient management, but data on current practices, radiation dose-related best practices, and radiation doses are scarce. To address these issues, the IAEA conducted a worldwide study of nuclear cardiology practice. We present the European subanalysis.MethodsIn March 2013, the IAEA invited laboratories across the world to document all SPECT and PET studies performed in one week. The data included age, gender, weight, radiopharmaceuticals, injected activities, camera type, positioning, hardware and software. Radiation effective dose was calculated for each patient. A quality score was defined for each laboratory as the number followed of eight predefined best practices with a bearing on radiation exposure (range of quality score 0 – 8). The participating European countries were assigned to regions (North, East, South, and West). Comparisons were performed between the four European regions and between Europe and the rest-of-the-world (RoW).ResultsData on 2,381 European patients undergoing nuclear cardiology procedures in 102 laboratories in 27 countries were collected. A cardiac SPECT study was performed in 97.9 % of the patients, and a PET study in 2.1 %. The average effective dose of SPECT was 8.0 ± 3.4 mSv (RoW 11.4 ± 4.3 mSv; P < 0.001) and of PET was 2.6 ± 1.5 mSv (RoW 3.8 ± 2.5 mSv; P < 0.001). The mean effective doses of SPECT and PET differed between European regions (P < 0.001 and P = 0.002, respectively). The mean quality score was 6.2 ± 1.2, which was higher than the RoW score (5.0 ± 1.1; P < 0.001). Adherence to best practices did not differ significantly among the European regions (range 6 to 6.4; P = 0.73). Of the best practices, stress-only imaging and weight-adjusted dosing were the least commonly used.ConclusionIn Europe, the mean effective dose from nuclear cardiology is lower and the average quality score is higher than in the RoW. There is regional variation in effective dose in relation to the best practice quality score. A possible reason for the differences between Europe and the RoW could be the safety culture fostered by actions under the Euratom directives and the implementation of diagnostic reference levels. Stress-only imaging and weight-adjusted activity might be targets for optimization of European nuclear cardiology practice.

Radiation dose and prognosis of ultra-low-dose stress-first myocardial perfusion SPECT in patients with chest pain using a high-efficiency camera.

Although SPECT myocardial perfusion imaging (MPI) provides valuable information about patients with chest pain, there is growing concern regarding its radiation burden and lengthy duration. New high-efficiency (HE) cameras and stress-first protocols both offer the potential to markedly reduce radiation. No previous study has assessed outcomes and radiation doses of patients undergoing MPI on an HE-SPECT camera using an ultra-low-dose stress-first protocol. One hundred patients presenting to the emergency department with chest pain who were candidates for stress-first MPI underwent injection of approximately 185 MBq (5 mCi) of (99m)Tc-tetrofosmin at peak stress, followed by supine and prone imaging on an HE-SPECT camera. Same-day rest imaging was performed on patients with any abnormality on imaging after stress. Radiation effective dose was calculated from administered and residual activities. Patients were contacted 3 mo after discharge, and electronic records were accessed to evaluate the need for reevaluation for chest pain, additional imaging, or cardiac events. Stress-only imaging was performed in 69 patients, for whom radiation effective dose averaged 0.99 mSv and study duration, 117 min. Radiation dose averaged 2.22 mSv over all patients. At 3 mo, 96 patients were free of major adverse cardiac events, repeat hospital chest pain evaluation, and repeat imaging or stress testing. One year after MPI and hospital discharge, all patients were living and without acute coronary syndrome. HE-SPECT stress-only imaging can be performed in more than two thirds of chest pain patients without a high pretest probability of a stress perfusion defect, with excellent prognosis, a radiation dose averaging 1 mSv, and a test duration of less than 2 h.

Combining stress-only myocardial perfusion imaging with coronary calcium scanning as a new paradigm for initial patient work-up: An exploratory analysis

BackgroundWe conducted an exploratory analysis to test whether the addition of a CAC scan can increase the applicability of stress-only SPECT-MPI. MethodsWe studied 162 patients referred for rest/stress SPECT-MPI who underwent a CAC scan. Each scan was interpreted by two readers in stepwise fashion: stress-only images; addition of clinical data; and addition of CAC data. At each step, the reader was asked if rest SPECT-MPI was necessary. ResultsStress-only images were interpreted as normal in 62, probably normal in 42, equivocal in 15, probably abnormal in 5, and definitely abnormal in 38 patients. Rest SPECT-MPI imaging was considered necessary, in 0% of normal studies, but in 88% of probably normal studies, and 100% of those with equivocal/abnormal studies. Addition of the clinical data did not materially change this decision. Additional consideration of the CAC scan results did not influence the deemed lack of need for a rest SPECT-MPI with normal SPECT-MPI or the necessity of rest SPECT-MPI with abnormal SPECT-MPI. However, the CAC scan reduced the deemed need for a rest SPECT-MPI in 72% with a probably normal, 47% with an equivocal, and 40% of those with a probably abnormal SPECT-MPI. ConclusionsOur exploratory analysis indicates that addition of a CAC scan to stress SPECT-MPI tends to diminish experienced readers’ deemed need to perform rest SPECT-MPI studies among patients with probably normal or borderline stress-only SPECT-MPI studies. Thus, further study appears warranted to assess the utility of using CAC scanning as a means for increasing the percent of SPECT-MPI studies that can be performed as stress-only studies.

Abstract 159: Evaluation of Downstream Utilization Following Stress-only versus Rest-Stress Myocardial Perfusion Imaging

Background: Current evidence and guidelines in nuclear cardiology support the use of stress-only myocardial perfusion imaging (SO-MPI), without rest imaging, to decrease radiation dose to the patient. We sought to determine the downstream utilization of cardiac procedures in patients undergoing SO-MPI in comparison to those undergoing rest-stress myocardial perfusion imaging (RS-MPI). Demonstration of the decreased need for cardiac procedures following SO-MPI would increase the confidence of interpreting nuclear cardiologists and referring physicians. Methods: We retrospectively analyzed the nuclear cardiology database at Allegheny General Hospital for patients undergoing stress testing with MPI from Jan 2010 to June 2011. Selection criteria for SO-MPI in our laboratory, includes no prior history of revascularization and low pre-test probability of coronary artery disease (CAD) based on symptoms and risk factors. We analyzed the rate of follow-up cardiac catherizations and repeat stress testing upto12 months after the index stress MPI. We compared the rate of procedure utilization following SO-MPI and RS-MPI. Results: A total of 5269 stress tests were performed during the enrollment period, of which 829 (16%) underwent SO-MPI, and the remainder (n=4440, 84%) had RS-MPI. Abnormal MPI was more likely in patients undergoing RS-MPI vs SO-MPI (525 vs 5; p&lt;0.05). Patients undergoing RS-MPI were more likely to have a follow-up procedure compared to those undergoing SO-MPI (odds ratio 2.5; p&lt;0.0001). Specifically the rate of cardiac catherization (565/4440; 13% in RS-MPI vs 27/829; 3%in SO-MPI p&lt;0.05) and the rate of repeat stress testing (177/4440; 4% in RS-MPI vs 15/829; 1.8% in SO-MPI, p&lt;0.05) were significantly higher in the RS-MPI group. Among patients undergoing SO-MPI, rate of cardiac catherization was significantly higher in patients having follow-up rest images compared to those that did not (odds ratio: 12.5, p&lt;0.001). There were 6 revascularizations in the SO-MPI group in the follow-up period of which 5 occurred in those with abnormal MPI and 1 occurred in a patient with normal SO-MPI but in the setting of an acute infarct. Conclusions: Downstream procedure utilization following a SO-MPI strategy is low. This complements the low mortality rate noted in this population by prior studies. It further confirms that the current selection criteria for SO-MPI is appropriate as most patients require only one image and do not need additional testing. In patients with low-intermediate pretest probability for CAD that are referred for MPI, SO-MPI with limited use of rest imaging can facilitate throughput, reduce patient radiation dose and is associated with appropriately low downstream utilization.