Myocardial Perfusion Single-photon Emission Tomography Research Articles

A novel algorithm developed using machine learning and a J-ACCESS database can estimate defect scores from myocardial perfusion single-photon emission tomography images.

Stress myocardial perfusion single-photon emission computed tomography (SPECT) imaging (MPI) has been used to diagnose and predict the prognoses of patients with coronary artery disease (CAD). An ongoing multicenter collaboration established a Japanese database (J-ACCESS) in 2001 that includes a risk model and expert interpretations. The present study aimed to develop a novel algorithm using machine learning (ML) and resources from the J-ACCESS database to aid SPECT image interpretation. We analyzed data from 1288 patients in J-ACCESS 3 and 4 databases. Three-dimensional (3D) stereoscopic images of left ventricular myocardial perfusion were reconstructed with linear transformation from the original short-axis data. Segments were extracted from U-Net, then features were extracted from each segment during the ML process. We estimated segmental scores based on weighted features obtained from fully connected layers. Correlations between segment scores interpreted by nuclear cardiology experts and estimated by ML were evaluated using a 17-segment model, summed stress (SSS), summed rest (SRS), and summed difference (SDS) scores, and ratios (%) of summed different scores (%SDS). The complete concordance rate of scores assessed by the experts and estimated by ML was 79.6%. The underestimated and overestimated rates were 10.3% and 10.0%, respectively. Associations between defect scores assessed by experts and ML were close, with correlation coefficients (r) of 0.923, 0.917, 0.842 and 0.853 for SSS, SRS, SDS, %SDS, respectively (p < 0.0001 for all). We created a new algorithm to estimate MPI scores using ML and the J-ACCESS database. This algorithm should provide accurate MPI interpretation even in facilities without specialist nuclear cardiologists, and might facilitate therapeutic decision-making and predict prognoses.

Texture analysis of SPECT myocardial perfusion provides prognostic value for dilated cardiomyopathy

BackgroundTexture analysis (TA) has demonstrated clinical values in extracting information, quantifying inhomogeneity, evaluating treatment outcomes, and predicting long-term prognosis for cardiac diseases. The aim of this study was to explore whether TA of SPECT myocardial perfusion could contribute to improving the prognosis of dilated cardiomyopathy (DCM) patients. MethodsEighty-eight patients were recruited in our study between 2009 and 2020 who were diagnosed with DCM and underwent single-photon emission tomography myocardial perfusion imaging (SPECT MPI). Forty TA features were obtained from quantitative analysis of SPECT imaging in subjects with myocardial perfusion at rest. All patients were divided into two groups: the all-cause death group and the survival group. The prognostic value of texture parameters was assessed by Cox regression and Kaplan–Meier analysis. ResultsTwenty-five all-cause deaths (28.4%) were observed during the follow-up (39.2±28.7 months). Compared with the survival group, NT-proBNP and total perfusion deficit (TPD) were higher and left ventricular ejection fraction (LVEF) was lower in the all-cause death group. In addition, 26 out of 40 texture parameters were significantly different between the two groups. Univariate Cox regression analysis revealed that NT-proBNP, LVEF, and 25 texture parameters were significantly associated with all-cause death. The multivariate Cox regression analysis showed that low gray-level emphasis (LGLE) (P = 0.010, HR = 4.698, 95% CI 1.457–15.145) and long-run low gray-level emphasis (LRLGE) (P =0.002, HR = 6.085, 95% CI 1.906–19.422) were independent predictors of the survival outcome. When added to clinical parameters, LVEF, TPD, and TA parameters, including LGLE and LRLGE, were incrementally associated with all-cause death (global chi-square statistic of 26.246 vs. 33.521; P = 0.028, global chi-square statistic of 26.246 vs. 34.711; P = 0.004). ConclusionTA based on gated SPECT MPI could discover independent prognostic predictors of all-cause death in medically treated patients with DCM. Moreover, TA parameters, including LGLE and LRLGE, independent of the total perfusion deficit of the cardiac myocardium, appeared to provide incremental prognostic value for DCM patients.

Soluble urokinase plasminogen activator receptor and functionally relevant coronary artery disease: a prospective cohort study

Background Soluble urokinase plasminogen activator receptor (suPAR) is an emerging biomarker associated with anatomical CAD burden and cardiovascular outcomes including myocardial infarction (MI) and death. We aimed to validate previous findings of the prognostic value of suPAR and to evaluate its diagnostic potential for functional relevant CAD (fCAD). Methods Consecutive patients with suspected fCAD were enrolled. Adjudication of fCAD was performed blinded to suPAR concentrations by myocardial perfusion single-photon emission tomography (MPI-SPECT) and coronary angiography. Prognostic outcome measures included all-cause death, cardiovascular death, and incident MI during 2-year follow-up. Results Among consecutive 968 patients, suPAR concentrations were higher in patients with fCAD compared to those without (3.45 vs. 3.20 ng/mL, p = 0.007), but did not provide acceptable diagnostic accuracy (area under the curve [AUC]: 0.56, 95%CI 0.52–0.60). SuPAR correlated with high-sensitivity cardiac-troponin T (Spearman’s rho (ρ) 0.393, p < 0.001), NT-proBNP (ρ = 0.327, p < 0.001), age (ρ = 0.364, p < 0.001) and very weakly with coronary atherosclerosis (ρ = 0.123, p < 0.001). Prognostic discrimination of suPAR was moderate for cardiovascular death (AUC = 0.72, 95%CI 0.62–0.81) and all-cause death (AUC = 0.72, 95%CI 0.65–0.79) at 2-years. SuPAR remained a significant predictor for all-cause death in multivariable Cox regression (HR = 1.96, p = 0.001). Conclusions SuPAR was an independent predictor of all-cause death, without diagnostic utility for fCAD. Clinical trial registration NCT01838148

Abstract 11490: Coronary Computed Tomography Angiography with Fractional Flow Reserve Outperforms Single-Photon Emission Tomography Myocardial Perfusion Imaging in the Observation Unit

Introduction: Coronary Computed Tomography Angiography (CCTA) and SPECT myocardial perfusion imaging (SPECT-MPI) are equally safe in evaluating patients presenting to the emergency department with acute chest pain. However, no study has compared the use of CCTA with Fractional Flow Reserve (FFR-CT) to SPECT-MPI in a chest pain observation unit (OU). We compared the performance of CCTA (with FFR-CT as needed) to SPECT-MPI for change in coronary artery disease (CAD) specific treatment (statins, antianginals, antiplatelets, and coronary revascularization) as well its impact on length of hospital stay (LOS). Methods: In 2020, our institution implemented an algorithm-based protocol in the OU to select patients appropriate for CCTA with explicit guidelines for management based on the results. We performed a retrospective analysis of 105 patients (52 SPECT-MPI patients from the period prior to initiation of the OU CCTA protocol who met criteria for CCTA, and 53 CCTA patients after CCTA protocol initiation). We performed two-tailed t-tests and chi-squared analyses to compare changes in treatment and LOS in both groups. Results: Patients in the CCTA group were younger (61 vs. 67 years, p=0.007), but there were no significant differences in CAD risk factors amongst the two groups. CCTA led to significant increase in statin, antianginal, and antiplatelet therapies, cardiac catheterization and revascularization within 6 months. There was no increase in LOS. Finally, CCTA did not increase acute kidney injury at follow up (Table 1). Conclusion: CCTA with FFR-CT significantly improved patient care by increasing appropriate preventative CAD treatment compared to SPECT-MPI while increasing the rate of revascularization without compromising length of stay or kidney function. In conclusion, protocol-based use of CCTA with FFR-CT is a more effective tool when compared to SPECT-MPI for chest pain patients admitted to the OU.

Evaluation of the Appropriateness of Patients Referring for Single-Photon Emission Tomography Myocardial Perfusion Imaging Based On ACCF/ASNC AUC 2009

Evaluation of the Appropriateness of Patients Referring for Single-Photon Emission Tomography Myocardial Perfusion Imaging Based On ACCF/ASNC AUC 2009

Myocardial ischemia in female patients with rheumatoid arthritis assessed with single photon emission tomography-myocardial perfusion imaging.

Non-specific cardiac symptoms in female patients with rheumatoid arthritis (RA) could indicate early cardiovascular disease. Myocardial perfusion imaging (MPI), with 99mTc tetrofosmin stress-rest single photon emission computer tomography (SPECT), in 13 RA female patients with atypical cardiac symptoms, was compared to 44 weight- and age-matched females with similar cardiac complaints (control group). Smoking, hypertension, diabetes mellitus, dyslipidemia, obesity and cardiac heredity were recorded and compared between the study and control group. MPI was assessed using 17 segment polar map and with a scale of 0 to 5 scoring. Patients with RA demonstrated higher cardiovascular risk (46%) compared to control individuals (17%). In addition, patients with RA had more irreversible myocardial ischemic abnormalities in their MPI than the control group. Dyslipidemia and obesity was found more frequent in RA patients with MPI SSS ≥ 4. RA patients with atypical cardiac complaints are at higher risk for cardiovascular disease; early detection and monitoring of this patient group could potentially reverse or successfully manage the consequences of the upcoming cardiovascular disease.

Combining high-sensitivity cardiac troponin and B-type natriuretic peptide in the detection of inducible myocardial ischemia

BackgroundSingle biomarker approaches provide only moderate accuracy in the non-invasive detection of exercise-induced myocardial ischemia. We therefore assessed the combination of the two most promising single biomarkers: high-sensitivity cardiac troponin I (hs-cTnI) and B-type natriuretic peptide (BNP). MethodsConsecutive patients with suspected myocardial ischemia referred to stress myocardial perfusion single-photon emission tomography imaging (MPI) were enrolled. Clinical judgment (CJ) of the treating cardiologist regarding myocardial ischemia, quantified using a visual analogue scale, and blood concentrations of hs-cTnI and BNP were determined before and after stress. The presence of myocardial ischemia was adjudicated by independent cardiologists using MPI, blinded to biomarker measurements. Death and acute myocardial infarction (AMI) during follow-up were the prognostic endpoints. ResultsAmong 1142 consecutive patients inducible myocardial ischemia was found in 456 (40%) of all patients. For the detection of inducible myocardial ischemia, CJ before exercise stress testing (CJb) showed an area under the receiver-operating-characteristics curve (AUC) of 0.66 (95%CI 0.63–0.69), hs-cTnI 0.70 (95%CI 0.67–0.73, p=0.07 vs CJb), and BNP 0.66 (95%CI 0.62–0.69, p=0.98). The use of a dual-biomarker strategy combining hs-cTnI and BNP with CJb did not provide a significant advantage over the combination of hs-cTnI alone and CJb (AUC 0.74, 95%CI 0.72–0.77 vs AUC 0.74, 95%CI 0.71–0.77, p=0.16). Hs-cTnI showed good prognostic value for AMI (HR 1.6, 95%CI 1.3–1.9), and BNP for death (HR 1.6, 95%CI 1.3–2.1). ConclusionA dual-biomarker strategy combing BNP and hs-cTnI does not further increase diagnostic accuracy on top of clinical judgment and hs-cTnI alone. Summary and highlightsWe included 1142 consecutive patients with suspected inducible ischemia, and evaluated the added value of the biomarkers high-sensitivity cardiac troponin (hs-cTn) and B-type natriuretic peptide (BNP), alone and in combination, on top of clinical judgment. Clinical trial registrationBiochemical and Electrocardiographic Signatures in the Detection of Exercise-induced Myocardial Ischemia (BASEL VIII), NCT01838148, https://clinicaltrials.gov/ct2/show/NCT01838148

Assessment of inpatient multimodal cardiac imaging appropriateness at large academic medical centers.

BackgroundResponding to concerns regarding the growth of cardiac testing, the American College of Cardiology Foundation (ACCF) published Appropriate Use Criteria (AUC) for various cardiac imaging modalities. Single modality cardiac imaging appropriateness has been reported but there have been no studies assessing the appropriateness of multiple imaging modalities in an inpatient environment.MethodsA retrospective study of the appropriateness of cardiac tests ordered by the inpatient General Internal Medicine (GIM) and Cardiology services at three Canadian academic hospitals was conducted over two one-month periods. Cardiac tests characterized were transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), single-photon emission tomography myocardial perfusion imaging (SPECT), and diagnostic cardiac catheterization.ResultsOverall, 553 tests were assessed, of which 99.8 % were classifiable by AUC. 91 % of all studies were categorized as appropriate, 4 % may be appropriate and 5 % were rarely appropriate. There were high rates of appropriate use of all modalities by GIM and Cardiology throughout. Significantly more appropriate diagnostic catheterizations were ordered by Cardiology than GIM (93 % vs. 82 %, p = <0.01). Cardiology ordered more appropriate studies overall (94 % vs. 88 %, p = 0.03) but there was no difference in the rate of rarely appropriate studies (3 % vs. 6 %, p = 0.23).ConclusionThe ACCF AUC captured the vast majority of clinical scenarios for multiple cardiac imaging modalities in this multi-centered study on Cardiology and GIM inpatients in the acute care setting. The rate of appropriate ordering was high across all imaging modalities. We recommend further work towards improving appropriate utilization of cardiac imaging resources focus on the out-patient setting.

A multicenter evaluation of the appropriate use of single-photon emission tomography myocardial perfusion imaging in Greece

BackgroundThis study evaluates the appropriate use of myocardial perfusion imaging (MPI) and determines patterns and variables associated with inappropriate testing. MethodsOver a 10-month period data were collected prospectively from consecutive patients referred for MPI in four academic departments and an appropriate use grade was assigned (appropriate, uncertain, inappropriate, and unclassifiable scans) according to established criteria. ResultsAmong 3,032 referrals appropriate MPI had 72.8% of patients and 19.2% of studies were inappropriate, the remaining being uncertain (7.2%) or unclassifiable (0.8%). In multivariate analysis the asymptomatic status (odds ratio 10.7, P < .001), good functional capacity (odds ratio 1.9, P < .001), an interpretable resting electrocardiogram (odds ratio 1.8, P = .004), an age <65 years (odds ratio 1.5, P = .001) and the absence of diabetes (odds ratio 1.7, P < .001) or dyslipidemia (odds ratio 1.3, P = .014) were independent predictors of inappropriate scintigraphy. The most common indication for inappropriate testing was the assessment of asymptomatic patients <2 years after percutaneous coronary intervention (PCI) (38.9%). ConclusionsThe appropriate use of MPI is relatively high, but a considerable proportion of inappropriate scans is noted which is associated with markers of lower risk. The most common source of inappropriate testing is the assessment of asymptomatic patients <2 years after PCI.

Phase analysis in patients with reversible perfusion defects and normal coronary arteries at angiography

A count-based new technique from gated myocardial perfusion single-photon emission tomography (gMPS) was developed to allow the phase analysis providing information about the left ventricular (LV) regional discordance in contractility which is a measure of LV dyssynchrony. Since the phase analysis provides data for evaluating the dyssynchronous LV contraction, it has an important role in diagnosis and management of patients with left ventricular dysfunction. The aim of the study was to assess the presence of left ventricular dyssynchrony in patients with reversible perfusion defects on gMPS scans and normal or near normal coronary arteries at angiography. 32 patients (19 men, 59 %) with reversible mild perfusion defects on gMPS and normal coronary angiogram were retrospectively enrolled in the study. The peak of the phase histogram, the standard deviation of the phase distribution (PSD), the width of the band (PHB), and the symmetry and peakedness of the phase histogram, which are the assessment parameters for the LV dyssynchrony, were calculated from gMPS scans of patients by means of the phase analysis. Although, five quantitative variables are derived from the phase analysis of gMPS, PSD and PHB are two quantitative indices to assess LV global mechanical dyssynchrony and measurements of PSD (men 24.96 ± 7.31, women 24.26 ± 10.07) and PHB (men 70.1 ± 13.99, women 71.0 ± 30.4) were significantly higher than the those reported in the literature (p < 0.001). No significant differences in gMPS phase analysis indices were found between both sexes except kurtosis. As a conclusion, this study provides the phase analysis to detect LV mechanical dyssynchrony as new evidence supporting the concept that an abnormal scintigraphy finding, rather than being false-positive, may be an early marker of vasomotion changes associated with occult atherosclerosis in patients with normal coronary angiography findings.

Myocardial Perfusion Single-Photon Emission Tomography (SPET) and Positron Emission Tomography–Computed Tomography (PET-CT) Imaging for Congenitally Corrected Transposition of Great Arteries

Congenitally corrected transposition of great arteries (ccTGA) consists of both atrioventricular and ventriculo-arterial discordance. In patients with ccTGA, the pulmonary artery arises from the left ventricle, whereas the aorta arises from the right ventricle. The burden of the systemic blood pressure on the right ventricle involves an increased risk of coronary artery disease (CAD) and, as a long-term consequence, myocardial hypertrophy and gradual failure. This report describes the case of an adult patient affected by ccTGA who was referred for an episode of atypical chest pain while at rest. First-line diagnostic examinations were inconclusive. Myocardial perfusion single-photon emission tomography (SPET) was performed to exclude CAD, but the congenital abnormalities of the patient's heart made interpretation of the images particularly difficult. A perfusion positron emission tomography-computed tomography (PET-CT) scan with (13)N-ammonia then was suggested, which unmasked an unexpected artifact. The case report demonstrates that hybrid imaging techniques such as SPET-CT and PET-CT should be used systematically when CAD is suspected for patients with abnormal anatomy of the heart, including ccTGA.

Myocardial bridging on coronary CTA: An innocent bystander or a culprit in myocardial infarction?

Myocardial bridging describes the clinical entity whereby a segment of coronary artery is either partially or completely covered by surrounding myocardium. It represents the most frequent congenital coronary anomaly and has an estimated prevalence of ≤13% on angiographic series. With the emergence of cardiac computed tomography and its ability to simultaneously image the coronary arteries and also the myocardium, there has been an apparent increase in the detection rates of myocardial bridges (prevalence as high as 44%). It has now become important to evaluate their clinical significance. Myocardial bridging is generally considered a benign entity with survival rates of 97% at 5 years; however, there is now emerging evidence that certain myocardial bridge characteristics may be associated with cardiovascular morbidity. The length and depth of myocardial bridges have been associated with increased atherosclerosis, whereas the degree of systolic compression has been associated with ischemia on myocardial perfusion single-photon emission tomography. On the basis of current evidence, it appears that limiting further testing for ischemia to symptomatic patients with long and/or deep myocardial brides would be appropriate.

Study of the Predictors and Lesion Characteristics of Ischemic Heart Disease Patients With False Negative Results in Stress Myocardial Perfusion Single-Photon Emission Tomography

The predictors and lesion morphology of patients with ischemic heart disease testing false negative results in stress myocardial perfusion single-photon emission computed tomography (SPECT) was investigated. Subjects were 58 consecutive patients who underwent coronary angiography (CAG), even though they showed normal findings in stress myocardial perfusion SPECT. Age, gender, methods of stress, perfusion agent, coronary risk factors, angina symptoms, and electrocardiographic changes were investigated as predictors by multivariate analysis. For lesion morphology, significant stenotic lesions were studied for morphological characteristics and reference diameter (RD), percentage diameter stenosis (%DS), minimum lumen diameter (MLD), and lesion length (LL) were measured. CAG revealed 30 significant stenotic lesions in 18 patients. Logistic regression analysis revealed significant predictors to be age (odds ratio (OR) 1.118, p<0.05), typical anginal pain (OR 21.09, p<0.01), and hypertension (OR 8.336, p<0.05). For lesion morphology, there were only 2 diffuse lesions and the mean RD, %DS, MLD, and LL were 3.03+/-0.9 mm, 63.1 +/-9.3%, 1.13+/-0.49 mm, and 13.2+/-7.0 mm, respectively. Sufficient caution is believed necessary in the interpretation of normal findings of stress myocardial perfusion SPECT when the patient is elderly, complains of typical anginal pain, or has hypertension. In regard to characteristics of lesion morphology, there were hardly any diffuse lesions.

Long-term prognostic value of exercise 99m Tc-MIBI SPET myocardial perfusion imaging in patients after percutaneous coronary intervention

The purpose of this study was to evaluate the long-term prognostic value of exercise technetium-99m methoxyisobutylisonitrile ((99m)Tc-MIBI) single-photon emission tomography (SPET) imaging in patients after percutaneous coronary intervention (PCI). Three hundred and eighteen consecutive post-PCI patients who underwent exercise and rest (99m)Tc-MIBI SPET myocardial perfusion imaging (MPI) were followed up for 38+/-27 months. Patients with early revascularisation (<3 months after MPI) were excluded. A semiquantitative visual analysis employing a 20-segment and four-point scoring system was used to define the summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS). Death and non-fatal myocardial infarction (MI) were considered as hard events, and late revascularisation procedures (>/=3 months after MPI) as soft events. Fifty-one patients (16.0%) suffered from cardiac events during follow-up, including 1 (0.3%) death, 13 (4.1%) non-fatal MIs, 9 (2.8%) coronary artery bypass grafting procedures and 28 (8.8%) PCIs. According to the SPET results, patients were classified into three groups: patients with normal MPI (SSS=0, n=153), patients with irreversible defects (SDS<3 and SRS>1, n=100) and patients with reversible defects (SDS>/=3, n=65). The annual hard cardiac event rate in patients with reversible defects was 3.9%, which was significantly higher than that in patients with normal MPI (0.2%, chi(2)=7.71; P<0.01). The annual soft cardiac event rate in patients with reversible defects was 10.7%, which was significantly higher than that in patients with irreversible defects (2.5% chi(2)=17.69; P<0.001), and also significantly higher than that in patients with normal MPI (1.5%, chi(2)=33.89; P<0.001). In patients with normal and reversible defects, there was no significant difference in soft and hard cardiac event rates according to whether patients were symptomatic or asymptomatic ( P>0.05). However, the annual soft event rate in patients with irreversible defects and symptoms was 5.0%, which was higher than that of 0.6% in asymptomatic patients (chi(2)=6.11, P<0.05). Multivariate Cox analysis showed that SSS was the best independent predictor for hard cardiac events (chi(2)=12.70; P<0.001) and SDS was the strongest independent predictor for soft cardiac events (chi(2)=11.72; P<0.001). Post-PCI patients who have normal exercise (99m)Tc-MIBI SPET MPI have a good long-term prognosis, while those with reversible defects are at a higher risk for future cardiac events, without correlation to the chest pain symptoms. However, symptomatic patients with irreversible defects have a higher risk for repeat revascularisation, but not for hard events, compared with asymptomatic patients. Exercise (99m)Tc-MIBI SPET MPI has important clinical value for risk stratification and management decision-making in post-PCI patients.

Validation of a model of left ventricular segmentation for interpretation of SPET myocardial perfusion images.

Several models of left ventricular segmentation have been developed that assume a standard coronary artery distribution, and are currently used for interpretation of single-photon emission tomography (SPET) myocardial perfusion imaging. This approach has the potential for incorrect assignment of myocardial segments to vascular territories, possibly over- or underestimating the number of vessels with significant coronary artery disease (CAD). We therefore sought to validate a 17-segment model of myocardial perfusion by comparing the predefined coronary territory assignment with the actual angiographically derived coronary distribution. We examined 135 patients who underwent both coronary angiography and stress SPET imaging within 30 days. Individualized coronary distribution was determined by review of the coronary angiograms and used to identify the coronary artery supplying each of the 17 myocardial segments of the model. The actual coronary distribution was used to assess the accuracy of the assumed coronary distribution of the model. The sensitivities and specificities of stress SPET for detection of CAD in individual coronary arteries and the classification regarding perceived number of diseased coronary arteries were also compared between the two coronary distributions (actual and assumed). The assumed coronary distribution corresponded to the actual coronary anatomy in all but one segment (#3). The majority of patients (80%) had 14 or more concordant segments. Sensitivities and specificities of stress SPET for detection of CAD in the coronary territories were similar, with the exception of the RCA territory, for which specificity for detection of CAD was better for the angiographically derived coronary artery distribution than for the model. There was 95% agreement between assumed and angiographically derived coronary distributions in classification to single- versus multi-vessel CAD. Reassignment of a single segment (segment #3) from the LCX to the LAD territory further improved the model's fit with the anatomic data. It is concluded that left ventricular segmentation using a model with assumed coronary artery distribution is valid for interpretation of SPET myocardial perfusion imaging.

A new dynamic myocardial phantom for the assessment of left ventricular function by gated single-photon emission tomography

Gated myocardial perfusion single-photon emission tomography (SPET) has been used for the measurement of left ventricular (LV) function and validated by means of comparison with other imaging modalities. We have designed a new dynamic myocardial phantom in order to validate the LV function as assessed by the use of gated myocardial perfusion SPET. The phantom consists of two half-ellipsoids (an endocardial surface and an epicardial surface) and a thorax. The myocardial space is filled with a radioactive solution. The endocardial surface moves continuously towards and away from the epicardial surface in the longitudinal axis to vary the LV volume [143 ml at end-diastole (ED), 107 ml at end-systole (ES)] and thickness (apex 8 mm at ED and 26 mm at ES, midplane 8 mm). The mean values of wall motion (WM) for the apical midplane region and the basal midplane region were 5 mm and 2 mm, respectively. Gated myocardial SPET was performed during 8 and 16 intervals. These projection data sets were processed using a Butterworth filter with an order of 5 and a critical frequency of 0.34 cycles/cm. LV function was calculated using the quantitative gated SPET (QGS) algorithm. The LV function values estimated by gated SPET during 16 intervals [22% for ejection fraction (EF), 3.7 mm for WM of the apical midplane, 1.7 mm for WM of the basal midplane] closely resembled actual LV functions [25% for EF, 5 mm for WM of the apical midplane, 2 mm for WM of the basal midplane]. However, the estimated values during 8 intervals were smaller than those during 16 intervals (19% for EF, 3.3 mm for WM of the apical-midplane, 1.1 mm for WM of the basal-midplane). The estimated LV volumes closely correlated with the actual volumes (r=0.99 for 16 intervals, r=0.95 for 8 intervals). Utilizing this phantom, LV function estimated using gated myocardial SPET can be compared with actual values.

Gated single-photon emission tomography imaging protocol to evaluate myocardial stunning after exercise.

This study was designed to apply ECG-gating to stress myocardial perfusion single-photon emission tomography (SPET) for the evaluation of myocardial stunning after exercise. Technetium-99m sestamibi was selected as the perfusion agent and a rest/exercise 1-day protocol was employed. Fourteen patients without coronary stenosis and 33 patients with coronary stenosis were enrolled in the study. We carried out three data acquisitions with ECG-gating: a 15-min data acquisition starting 30 min after the rest injection (AC1), a 5-min acquisition starting 5 min after the stress injection (AC2) and a 15-min acquisition starting 20 min after the stress injection (AC3). Calculation of left ventricular ejection fraction (LVEF) values was performed by means of automatic determination of the endocardial surface for all gating intervals in the cardiac cycle. Measured global EF values in 14 patients without coronary stenosis were 52.3% +/- 7.6% (AC1), 60.6% +/- 8.9% (AC2) and 55.6% +/- 5.6% (AC3), and those in 11 patients with severe ischaemia were 53.6% +/- 8.0% (AC1), 45.6% +/- 12.1% (AC2) and 49.7% +/- 10.7%. The magnitude of the depression of post-stress LVEF relative to the rest LVEF correlated with the severity of ischaemia (r = 0.594, P = 0.002), and segments manifesting post-stress functional depression were associated with ischaemic segments showing reversible perfusion defects. Stress myocardial perfusion SPET with ECG-gating is a feasible method for the evaluation of myocardial stunning as well as exercise-induced ischaemia.

Quality of myocardial perfusion single-photon emission tomography imaging: multicentre evaluation with a cardiac phantom.

The aim of the study was to evaluate quality of myocardial perfusion single-photon emission tomography (SPET) imaging in Finnish hospitals. Nineteen nuclear medicine departments participated in the study. A myocardial phantom simulating clinical stress and rest conditions was filled with routinely used isotope solution (technetium-99m or thallium-201). The cardiac insert included three reversible defects (simulating ischaemia): 30x30x14 mm(3) septal (90% recovery at rest), 30x20x14 mm(3) posterobasal (full recovery) and 20x20x14 mm(3) lateral (full recovery). There were two fixed defects (simulating infarct): 30x20x14 mm(3) postero-apical and 10x10x6 mm(3) apical. The phantom was imaged and interpreted as a myocardial perfusion patient. Reconstruction, printout and reporting were performed according to the clinical routine of each centre. Three nuclear medicine specialists anonymously evaluated the quality of the image sets. The visual scores of the experts were ranked from 1 to 5. Additionally, points from 0 to 8 were given to research reports according to how well perfusion defects were detected. Quantitative points were calculated by comparing background-subtracted and -normalized counts from 12 regions of interest between stress and rest images. Results for technetium studies (12 departments) were better than those for thallium (7 departments). The average visual scores of the experts were 3.7+/-0. 9 for all image sets, 3.2+/-0.5 for thallium users and 3.9+/-0.6 for technetium users (P=0.003). Five laboratories received a low score which, according to the specialists, is barely sufficient for limited clinical use. Average points for the reports were 5.6+/-2.1, 4.9+/-1.5 and 6.5+/-1.7 (P=0.051), and for the quantitation 8.2+/-1. 0, 7.9+/-0.4 and 8.4+/-1.1 (P=0.185), respectively. Seven out of 22 interpreters did not detect the lateral 20x20x14 mm(3) defect; five of them used thallium. This study demonstrated the heterogeneity of myocardial perfusion SPET in Finland. The participating laboratories used a wide scale of methods and, sometimes, inappropriate imaging protocols. The need for quality assurance in nuclear cardiology, correct use of SPET instrumentation and objective comparison of clinical studies is evident. The method described is suitable for external quality assurance and quality improvement of myocardial SPET imaging, and is recommended for regular use in nuclear medicine.

Gated SPET myocardial perfusion acquisition within 5 minutes using focussing collimators and a three-head gamma camera.

Short acquisition protocols for gated single-photon emission tomography (SPET) myocardial perfusion imaging are desirable for sequential imaging to evaluate the myocardial response during pharmacological intervention. In this study a less than 5 min gated SPET acquisition protocol is proposed. Perfusion characteristics (defect severity) and left ventricular ejection fraction (LVEF), end-diastolic and end-systolic volumes (EDV, ESV), wall motion (WM) and wall thickening (WT) were calculated, checked for reproducibility and compared with data obtained using a standard gated SPET acquisition protocol. Gated SPET images were recorded in 20 patients starting 60 min after the administration of 925 MBq technetium-99m tetrofosmin at rest. The 5 min gated SPET studies were acquired with a three-head camera equipped with Cardiofocal collimators. This protocol was repeated twice. In addition gated SPET studies were acquired according to a standard protocol using parallel-hole collimators. The severity of perfusion defects was quantified on polar maps using the non-gated image data and a normal database. LVEF, EDV, ESV, WM and WT were calculated from the gated images. The agreement between 5-min and standard gated SPET acquisitions was excellent for all investigated parameters. The reproducibility of repeated 5-min acquisitions for the quantification of perfusion defect severity was excellent (r=0.97). The agreement for segmental WT scores between repeated 5-min gated SPET acquisitions was good: kappa=0.71; major differences in segmental classification were observed in 2.5%. For WM a good agreement was found for segments with a tracer uptake >/=30% of the maximum: kappa=0.65, major differences =7.7%. Excellent reproducibility was found for LVEF, EDV and ESV measurements: r=0.97, 0.99 and 0.99, respectively. It is concluded that fast gated SPET perfusion studies acquired in less than 5 min yield accurate and reproducible measurements of myocardial perfusion and function (global and regional). In addition the results obtained with the 5-min gated SPET protocol correlate well with those obtained using a standard acquisition protocol.

Stress/Rest Myocardial Perfusion SPET in Evaluation of the Hemodynamic Significance of a Fistula Between the Anterior Descending Branch of the Left Coronary and the Left Pulmonary Arteries

This paper describes the use of Stress/Rest Tc-99m Sestamibi (MIBI) Single Photon Emission Tomography (SPET) to evaluate the hemodynamic significance of an unusual fistula between the descending anterior branch of the left coronary artery and the left pulmonary artery. Coronary arteriography in a patient with myocardial infarction of the inferior wall revealed subocclusive (greater than 90%) stenosis of the right coronary and an abnormal branch proceeding from the intermediate section of the left anterior descending (LAD) artery to the left pulmonary artery. Treatment of the stenosis by percutaneous transluminal coronary angioplasty gave a good angiographic result but failed to resolve the angina. Myocardial Stress/Rest Tc-99m MIBI SPET disclosed an irreversible defect corresponding to the previous infarction. The anterior wall and apex were marked by a reversible defect due to a flow steal via the abnormal branch running from the intermediate section of the LAD artery to the left pulmonary artery. The examination was thus able to reveal perfusion defects in two different sites and of different size and gravity. Its findings and the coronary angiography data showed that these defects were caused by different coronary disorders (atherosclerosis of the right coronary artery and a coronary arteriovenous fistula of the LAD artery). It also demonstrated the functional importance of the LAD to the left pulmonary artery coronary fistula.