An automatic approach to the analysis, quantitation and review of perfusion and function from myocardial perfusion SPECT images

Relationship between Semi-Quantitative Parameters of Thallium-201 Myocardial Perfusion Imaging and Coronary Artery Disease

This study aimed to investigate the diagnostic performance of semi-quantitative parameters of thallium-201 myocardial perfusion imaging (MPI) for coronary artery disease (CAD). From January to December 2017, patients were enrolled who had undergone Tl-201 MPI and received cardiac catheterization for coronary artery disease within three months of MPI. Receiver operating characteristics (ROC) analysis was used to determine the optimal cutoff values of semi-quantitative parameters. A comparison of the sensitivity and specificity of these parameters based on different subgroupings was further performed. A total of 130 patients were enrolled for further analysis. Among the collected parameters, the stress total perfusion deficit (sTPD) had the highest value of the area under curve (0.813) under the optimal cutoff value of 3.5%, with a sensitivity and specificity of 73.5% and 74.5%, respectively (p = 0.0000), for the diagnosis of CAD. With further subgrouping analysis based on history of diabetes or dyslipidemia, the sensitivity and specificity showed similar results. Based on the currently collected data and image acquisition conditions, the sTPD parameter has a clinical role for the diagnosis of CAD with a cutoff value of 3.5%.

Serial examination of cardiac function and perfusion in growing rats using SPECT/CT for small animals

Few studies have evaluated myocardial perfusion and ventricular function in normal, growing rats. We, therefore, evaluated serial changes in cardiac perfusion and function during the growth of normal rats using single photon emission computed tomography (SPECT) with technetium (^99mTc)-sestamibi. Gated SPECT was serially performed in six normal rats. The left ventricular end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF) were calculated with Quantitative Gated SPECT software. The perfusion distribution was calculated as the percentage uptake of each of the 17 segments using Quantitative Perfusion SPECT software. As expected, the body weight (BW) of the rats increased with growth, but their heart rates (HR) did not change over time. EF decreased very slowly over time and showed a negative correlation with BW. EDV, ESV and SV showed strong positive correlations with BW. There were no significant differences in the percentage segmental uptake in 13 of the 17 segments during growth, except for three basal and one apical segments. Therefore, a single normal database could be applied for the evaluation of perfusion abnormalities in rats of at least 8 to 28 weeks old.

Comparative Performances of Dipyridamole and Regadenoson to Detect Myocardial Ischemia using Cardiac Cadmium-Zinc-Telluride Single-Photon Emission Computerized Tomography

Objective:

We evaluated the relative performances of dipyridamole (Dip) and regadenoson (Reg) in a cohort of patients referred for coronary artery disease diagnosis or follow-up using myocardial perfusion imaging.

Materials and Methods:

We retrospectively included 515 consecutive patients referred for ^99mTc-sestamibi myocardial perfusion single-photon emission computerized tomography (SPECT) on a cadmium-zinc-telluride (CZT) camera after pharmacologic stress. About three quarters (n = 391, 76%) received Dip. Reg was administrated to patients with chronical respiratory disease or with body mass index (BMI) over 38 kg/m² (n = 124, 24%). Patients with an abnormal stress scan (92%) underwent a rest imaging on the same day. Qualitative interpretation of perfusion images was achieved using QPS software, and the ischemic area was assessed using the 17-segment model. In patients undergoing a stress-rest protocol, perfusion polar plots were postprocessed using automated in-house software to quantify the extension, intensity, and location of the reversible perfusion defect. Statistical comparison between groups was performed using univariate and multivariate analysis.

Results:

Qualitative analysis concluded to myocardial ischemia in 70% of the patients (69% in the Dip group, 76% in the Reg group, P = ns). In those patients, the number of involved segments (Dip 2.5 ± 1.6, Reg 2.7 ± 1.6, P = ns) and the proportion of patients with an ischemic area larger than two segments (Dip 30%, Reg 37%, P = ns) were comparable. Automated quantification of the reversible perfusion defect demonstrated similar defect extension, intensity, and severity in the two groups. Defect location was identical at the myocardial segment and vascular territory scales.

Conclusions:

Reg and Dip showed equal performances for ischemic burden characterization using myocardial CZT SPECT.

Is it Feasible to Use the Commercially Available Autoquantitation Software for the Evaluation of Myocardial Viability on Small-Animal Cardiac F-18 FDG PET Scan?

PURPOSE

To evaluate the reliability of quantitation of myocardial viability on cardiac F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) scans with three different methods of visual scoring system, autoquantitation using commercially available autoquantitation software, and infarct-size measurement using histogram-based maximum pixel threshold identification on polar-map in rat hearts.

METHODS

A myocardial infarct (MI) model was made by left anterior descending artery (LAD) ligation in rat hearts. Eighteen MI rats underwent cardiac FDG-PET-computed tomography (CT) twice within a 4-week interval. Myocardium was partitioned into 20 segments for the comparison, and then we quantitated non-viable myocardium on cardiac FDG PET-CT with three different methods: method A-infarct-size measurement using histogram-based maximum pixel threshold identification on polar-map; method B-summed MI score (SMS) by a four-point visual scoring system; method C-metabolic non-viable values by commercially available autoquantitation software. Changes of non-viable myocardium on serial PET-CT scans with three different methods were calculated by the change of each parameter. Correlation and reproducibility were evaluated between the different methods.

RESULTS

Infarct-size measurement, visual SMS, and non-viable values by autoquantitation software presented proportional relationship to each other. All the parameters of methods A, B, and C showed relatively good correlation between each other. Among them, infarct-size measurement (method A) and autoquantitation software (method C) showed the best correlation (r = 0.87, p < 0.001). When we evaluated the changes of non-viable myocardium on the serial FDG-PET-CT- however, autoquantitation program showed less correlation with the other methods. Visual assessment (method B) and those of infarct size (method A) showed the best correlation (r = 0.54, p = 0.02) for the assessment of interval changes.

CONCLUSIONS

Commercially available quantitation software could be applied to measure the myocardial viability on small animal cardiac FDG-PET-CT scan. This kind of quantitation showed good correlation with infarct size measurement by histogram-based maximum pixel threshold identification. However, this method showed the weak correlation when applied in the measuring the changes of non-viable myocardium on the serial scans, which means that the caution will be needed to evaluate the changes on the serial monitoring.

Cardioprotective effects of adenosine within the border and remote areas of myocardial infarction

Background

Adenosine may have beneficial effects on left ventricular function after myocardial infarction (MI), but the magnitude of this effect on remote and MI areas is controversial. We assessed the long-term effects of adenosine after MI using electrocardiogram-triggered ¹⁸ F-fluorodeoxyglucose positron emission tomography.

Methods

Wistar rats were subjected to coronary ligation and randomized into three groups treated daily for 2 months by NaCl (control; n = 7), 2-chloroadenosine (CADO; n = 8) or CADO with 8-sulfophenyltheophilline, an antagonist of adenosine receptors (8-SPT; n = 8).

Results

After 2 months, control rats exhibited left ventricular remodelling, with increased end-diastolic volume and decreased ejection fraction. Left ventricular remodelling was not significantly inhibited by CADO. Segmental contractility, as assessed by the change in myocardial thickening after 2 months, was improved in CADO rats compared to control rats (+1.6% ± 0.8% vs. −2.3% ± 0.8%, p < 0.001). This improvement was significant in border (+5.6% ± 0.8% vs. +1.5% ± 0.8%, p < 0.001) and remote (−4.0% ± 1.0% vs. −10.4% ± 1.3%, p < 0.001) segments, but absent in MI segments. Histological analyses revealed that CADO reduced fibrosis, cardiomyocyte hypertrophy and apoptosis. Protective effects of CADO were blunted by 8-SPT.

Conclusion

Long-term administration of adenosine protects the left ventricle from contractile dysfunction following MI.

Preoperative regional left ventricular wall thickening determined by quantitative gated SPECT as a predictor of mid-term surgical results for ischemic and nonischemic cardiomyopathy

BACKGROUND

This study aimed to elucidate whether regional left ventricular wall thickening (LVWT) determined by quantitative gated SPECT (QGS) is useful in predicting surgical outcomes for ischemic (ICM) and nonischemic cardiomyopathy (NICM).

METHODS AND RESULTS

The study group comprised 53 patients with either ICM (n=30, left ventricular ejection fraction (LVEF)=24.7±7.1%) or NICM (n=23, LVEF=24.0±6.3%) scheduled for surgical repair underwent preoperative QGS to evaluate regional LV function. LVWT of 20 segments derived from QGS was normalized by being divided by the normal value of each LV level. Normalized values of the segments were summed to be representative of each area. For 16 of the 30 patients with ICM and 17 of the 23 patients with NICM, surgical ventricular restoration and papillary muscle approximation (PMA) were performed for surgical repair and, for the rest, PMA alone was done for both ICM and NICM patients. Adjunctive coronary artery bypass grafting for ICM patients was added when necessary. Mean follow-up periods were 2.5±1.8 years for ICM and 2.2±2.4 years for NICM. Posterior regional LVWT in NICM (normalized sum value <0.61 n=7, ROC: AUC=0.80) predicted cardiac events (chronic heart failure and cardiac-caused death). The one-year cardiac event-free rates were 22.2% and 85.1% and the 2 years rates were 11.1% and 48.6% for the lower posterior WT group and higher posterior WT group respectively (P=0.003).

CONCLUSIONS

Posterior LVWT can be a predictor for postoperative cardiac events in patients with NICM.

SPECT myocardial perfusion imaging as an adjunct to coronary calcium score for the detection of hemodynamically significant coronary artery stenosis

Background

Coronary artery calcifications (CAC) are markers of coronary atherosclerosis, but do not correlate well with stenosis severity. This study intended to evaluate clinical situations where a combined approach of coronary calcium scoring (CS) and nuclear stress test (SPECT-MPI) is useful for the detection of relevant CAD.

Methods

Patients with clinical indication for invasive coronary angiography (ICA) were included into our study during 08/2005-09/2008. At first all patients underwent CS procedure as part of the study protocol performed by either using a multidetector computed tomography (CT) scanner or a dual-source CT imager. CAC were automatically defined by dedicated software and the Agatston score was semi-automatically calculated. A stress-rest SPECT-MPI study was performed afterwards and scintigraphic images were evaluated quantitatively. Then all patients underwent ICA. Thereby significant CAD was defined as luminal stenosis ≥75% in quantitative coronary analysis (QCA) in ≥1 epicardial vessel. To compare data lacking Gaussian distribution an unpaired Wilcoxon-Test (Mann–Whitney) was used. Otherwise a Students t-test for unpaired samples was applied. Calculations were considered to be significant at a p-value of <0.05.

Results

We consecutively included 351 symptomatic patients (mean age: 61.2±12.3 years; range: 18–94 years; male: n=240) with a mean Agatston score of 258.5±512.2 (range: 0–4214). ICA verified exclusion of significant CAD in 66/67 (98.5%) patients without CAC. CAC was detected in remaining 284 patients. In 132/284 patients (46.5%) with CS>0 significant CAD was confirmed by ICA, and excluded in 152/284 (53.5%) patients. Sensitivity for CAD detection by CS alone was calculated as 99.2%, specificity was 30.3%, and negative predictive value was 98.5%. An additional SPECT in patients with CS>0 increased specificity to 80.9% while reducing sensitivity to 87.9%. Diagnostic accuracy was 84.2%.

Conclusions

In patients without CS=0 significant CAD can be excluded with a high negative predictive value by CS alone. An additional SPECT-MPI in those patients with CS>0 leads to a high diagnostic accuracy for the detection of CAD while reducing the number of patients needing invasive diagnostic procedure.

Measuring myocardial salvage

The efficacy of cardioprotective strategies can be quantified by myocardial salvage as an indicator of therapeutic benefit. Salvage is calculated as the difference between the area at risk (AAR) and the final infarct size (FIS). AAR has been quantified by angiographic assessment followed by quantification of FIS by biochemical ischaemic markers or imaging modalities such as cardiovascular magnetic resonance (CMR). Angiographical methods may overestimate AAR and since methodological differences may exist between different modalities, the use of different modalities for estimating AAR and FIS may not be recommended. (99m)Technetium (Tc)-Sestamibi single-photon emission tomography (SPECT) allows quantification of AAR and FIS by tracer injection prior to revascularization and after 1 month, respectively. SPECT provides the most validated measure of myocardial salvage and has been utilized in multiple randomized clinical trials. However, SPECT is logistically challenging, expensive, and includes radiation exposure. More recently, a large number of studies have suggested that CMR can determine salvage in a single examination by combining measures of myocardial oedema in the AAR exposed to ischaemia reperfusion with FIS quantification by late gadolinium enhancement. The T1- and T2-weighted CMR approaches for quantification of AAR utilize non-contrast, early and late gadolinium enhancement techniques. The technical progress, high spatial resolution and the potential for retrospective quantification of the AAR makes CMR the most appropriate technique for assessment of myocardial salvage. However, the optimum CMR technique for assessment of myocardial AAR remains to be defined. Consequently, we recommend a comprehensive CMR protocol to ensure reliable assessment of myocardial salvage.

A blunted heart rate response to regadenoson is an independent prognostic indicator in patients undergoing myocardial perfusion imaging

BACKGROUND

Regadenoson myocardial perfusion imaging (MPI) is a useful method for risk assessment. We hypothesized that the heart rate response (HRR) to regadenoson carries incremental prognostic information to that derived from perfusion pattern and left ventricular (LV) ejection fraction (EF).

METHODS AND RESULTS

The study population included 1,156 (60 ± 13 years, 46% women, 40% diabetes mellitus, 53% chronic kidney disease) patients. During a follow-up period of 22 ± 5 months, 103 patients died (9%). Independent determinants of the HRR included age, gender, race, diabetes mellitus, coronary revascularization, LVEF, use of insulin and aldosterone antagonists. Decreasing HRR was associated with stepwise increase in mortality (log-rank P < .0001). In a Cox proportional model for mortality that adjusted for age, gender, diabetes mellitus, renal disease, and MPI findings, HRR in the lowest quartile was independently associated with fivefold increase in mortality compared to the highest quartile [HR 5.2, 95% CI 2.3-12.0, P < .0001]. Patients with a normal HRR had a relatively low annualized total mortality despite the presence of risk factors. The addition of HRR to traditional MPI findings had a net reclassification improvement of 15%, P = .02.

CONCLUSION

A blunted HRR to regadenoson is an independent predictor of poor outcome, adds incremental value to MPI, and helps in better risk stratification.

The prevalence and predictive accuracy of quantitatively defined transient ischemic dilation of the left ventricle on otherwise normal SPECT myocardial perfusion imaging studies

AIM

TID in the setting of otherwise normal MPI has been suggested as a marker of high risk CAD. In this study we estimate the variance of TID in a normal population and the statistical frequency of false positive TID. This will provide an indirect measurement of predictive accuracy (PA) in a mixed referral population.

OBJECTIVE

To study the PA of TID in otherwise normal MPI.

METHODS

688 consecutive patients were studied. We defined TID according to the standard method at 2 cut-off values; 1SD and 2SD, and also by a BSA normalized volume difference with gender-specific 2SD limits (NrVD).

RESULTS

457 patients with otherwise normal MPI were analyzed. PA of TID at 1SD was 4% and 26% at 2SD. PA was slightly higher (42%) using the NrVD, however, still too low to be clinically useful as a high-risk marker. PA of TID in patients with perfusion abnormalities was 58% at 1SD, 80% at 2SD and slightly higher (93%) by NrVD.

CONCLUSIONS

In the setting of otherwise normal MPI, elevated TIDr has a low prevalence and poor predictive accuracy and should not be considered summarily as a marker of high risk CAD.

Acipimox-enhanced ¹⁸F-fluorodeoxyglucose positron emission tomography for characterizing and predicting early remodeling in the rat infarct model

The rat myocardial infarction (MI) model is widely used to study left ventricular (LV) remodeling. In this study, acipimox-enhanced (18)F-Fluorodeoxyglucose (FDG) gated-positron emission tomography (PET) was assessed for characterizing and predicting early remodeling in the rat infarct model. Nineteen Wistar rats had surgical occlusion of the left anterior descending coronary artery and 7 were sham-operated. PET was scheduled 48 h and 2 weeks later for quantifying MI area and LV function. Segments with <50% of FDG uptake had histological evidence of MI (74 ± 9% decrease in parietal thickness, fibrosis development). At 48 h, MI area was large (>35% of LV) in 6 rats, moderate (15-35% of LV) in 8 rats, limited (<15% of LV) in 5 rats and absent in the 7 sham rats. LV remodeling, assessed through the 2 weeks increase in end-diastolic volume, increased between rats with limited, moderate and large MI (+72 ± 25, +109 ± 56, +190 ± 69 μl, respectively, P = 0.007). This 3-groups classification allowed predicting 44% of the 2 weeks increase in end-diastolic volume, and additional 34% were predicted by heart rate at 48 h. The acipimox-enhanced FDG gated-PET technique provides efficient characterization and prediction of early remodeling in the rat infarct model.

Surgical ventricular restoration improves the left ventricle basal wall function using quantitative gated SPECT

OBJECTIVE

It is not clear whether surgical ventricular restoration (SVR) or procedures approaching mitral complex for controlling functional mitral regurgitation (MR) affect the regional left ventricular wall function. The purpose of the present study was to evaluate the regional LV function after SVR using overlapping left ventriculoplasty (OLVP) using quantitative gated myocardial perfusion SPECT (QGS).

PATIENTS AND METHOD

Forty-one heart failure patients, including those with ischemic cardiomyopathy (ICM) (n = 25) and non-ICM (NICM) (n = 16), underwent SVR and/or papillary muscle approximation (PMA). The rest myocardial perfusion SPECT were performed before and early after operation (mean 25.8 ± 10.6 days). These patients were divided into 4 groups based on the surgical procedures (SVR and/or PMA) and etiology of patients (ICM or NICM) as follows: SVR (with or without PMA) of ICM, SVR of NICM, PMA of ICM and PMA of NICM groups. The regional wall thickening was compared before and after the operation between the four groups.

RESULTS

NYHA functional classes were improved after the operation in all four groups. MR grade was also improved in three groups other than SVR of the ICM group. The left ventricular basal wall thickening was improved postoperatively in following three groups (SVR of ICM: 12.7 ± 3.8% to 16.5 ± 4.6% p <0.05, PMA of ICM: 11.1 ± 4.3% to 14.9 ± 4.8% p <0.05, SVR of NICM: 5.8 ± 6.6% to 12.3 ± 6.4% p <0.05), whereas PMA of the NICM group did not show an improvement. Wall thickening in the middle and distal levels was not improved in all groups.

CONCLUSION

OLVP improved NYHA functional classes, and also improved the regional wall function at the basal level of the left ventricle. In contrast, lone PMA did not improve or impair the regional wall function at any of the levels.

QT prolongation is an independent predictor of mortality in end-stage renal disease

BACKGROUND

Coronary artery disease (CAD) is the predominant cause of sudden cardiac death in the general population, and sudden cardiac death is the leading cause of mortality in end-stage renal disease (ESRD).

HYPOTHESIS

QT-interval prolongation is an independent prognosticator in ESRD.

METHODS

We reviewed clinical, electrocardiographic, stress test, and coronary angiography data on ESRD patients evaluated for transplantation at our institution between 2000 and 2004 who underwent coronary angiography. The QT interval was corrected for heart rate and QRS duration (QTc). All-cause mortality data were prospectively collected and verified against the Social Security Death Index database.

RESULTS

During 40 +/- 28 months of follow-up, 132 of the 280 (47%) patients died prior to renal transplantation. Patients with a prolonged QTc (39%) had 1-, 3-, and 5-year death-rates of 12%, 36%, and 47%, respectively, vs 8%, 24%, and 36% for those with normal QTc (log-rank P = 0.03). In a multivariate Cox regression model that adjusted for age, gender, diabetes mellitus, myocardial infarction, presence and severity of CAD on angiography, left ventricular (LV) hypertrophy, LV ejection fraction (EF), and multiple other variables, QTc remained to be an independent predictor of survival (hazard ratio [HR]: 1.008, 95% confidence interval [CI]: 1.001-1.014, P = 0.016). Female gender, decreasing LVEF, and decreasing severity of CAD on angiography were independent predictors of prolonged QTc.

CONCLUSIONS

QTc prolongation is an independent predictor of mortality in ESRD patients being evaluated for renal transplantation. The prognostic information gained from the QTc is additive to that provided by the LVEF and the severity of CAD.

Geometric feature-based multimodal image registration of contrast-enhanced cardiac CT with gated myocardial perfusion SPECT

PURPOSE

Cardiac computed tomography (CT) and single photon emission computed tomography (SPECT) provide clinically complementary information in the diagnosis of coronary artery disease (CAD). Fused anatomical and physiological data acquired sequentially on separate scanners can be coregistered to accurately diagnose CAD in specific coronary vessels.

METHODS

A fully automated registration method is presented utilizing geometric features from a reliable segmentation of gated myocardial perfusion SPECT (MPS) volumes, where regions of myocardium and blood pools are extracted and used as an anatomical mask to de-emphasize the inhomogeneities of intensity distribution caused by perfusion defects and physiological variations. A multiresolution approach is employed to represent coarse-to-fine details of both volumes. The extracted voxels from each level are aligned using a similarity measure with a piecewise constant image model and minimized using a gradient descent method. The authors then perform limited nonlinear registration of gated MPS to adjust for phase differences by automatic cardiac phase matching between CT and MPS. For phase matching, they incorporate nonlinear registration using thin-plate-spline-based warping. Rigid registration has been compared with manual alignment (n=45) on 20 stress/rest MPS and coronary CTA data sets acquired from two different sites and five stress CT perfusion data sets. Phase matching was also compared to expert visual assessment.

RESULTS

As compared with manual alignment obtained from two expert observers, the mean and standard deviation of absolute registration errors of the proposed method for MPS were 4.3 +/- 3.5, 3.6 +/- 2.6, and 3.6 +/- 2.1 mm for translation and 2.1 +/- 3.2 degrees, 0.3 +/- 0.8 degree, and 0.7 +/- 1.2 degrees for rotation at site A and 3.8 +/- 2.7, 4.0 +/- 2.9, and 2.2 +/- 1.8mm for translation and 1.1 +/- 2.0 degrees, 1.6 +/- 3.1 degrees, and 1.9 +/- 3.8 degrees for rotation at site B. The results for CT perfusion were 3.0 +/- 2.9, 3.5 +/- 2.4, and 2.8 +/- 1.0 mm for translation and 3.0 +/- 2.4 degrees, 0.6 +/- 0.9 degree, and 1.2 +/- 1.3 degrees for rotation. The registration error shows that the proposed method achieves registration accuracy of less than 1 voxel (6.4 x 6.4 x 6.4 mm) misalignment. The proposed method was robust for different initializations in the range from -80 to 70, -80 to 70, and -50 to 50 mm in the x-, y-, and z-axes, respectively. Validation results of finding best matching phase showed that best matching phases were not different by more than two phases, as visually determined.

CONCLUSIONS

The authors have developed a fast and fully automated method for registration of contrast cardiac CT with gated MPS which includes nonlinear cardiac phase matching and is capable of registering these modalities with accuracy <10 mm in 87% of the cases.

Quantitative analysis of myocardial perfusion SPECT anatomically guided by coregistered 64-slice coronary CT angiography

Sequential testing by coronary CT angiography (CTA) and myocardial perfusion SPECT (MPS) obtained on stand-alone scanners may be needed to diagnose coronary artery disease in equivocal cases. We have developed an automated technique for MPS-CTA registration and demonstrate its utility for improved MPS quantification by guiding the coregistered physiologic (MPS) with anatomic CTA information.

METHODS

Automated registration of MPS left ventricular (LV) surfaces with CTA coronary trees was accomplished by iterative minimization of voxel differences between presegmented CTA volumes and motion-frozen MPS data. Studies of 35 sequential patients (26 men; mean age, 67 +/- 12 y) with 64-slice coronary CTA, MPS, and available results of the invasive coronary angiography performed within 3 mo were retrospectively analyzed. Three-dimensional coronary vessels and CTA slices were extracted and fused with quantitative MPS results mapped on LV surfaces and MPS coronary regions. Automatically coregistered CTA images and extracted trees were used to correct the MPS contours and to adjust the standard vascular region definitions for MPS quantification.

RESULTS

Automated coregistration of MPS and coronary CTA had the success rate of 96% as assessed visually; the average errors were 4.3 +/- 3.3 mm in translation and 1.5 +/- 2.6 degrees in rotation on stress and 4.2 +/- 3.1 mm in translation and 1.7 +/- 3.2 degrees in rotation on rest. MPS vascular region definition was adjusted in 17 studies, and LV contours were adjusted in 11 studies using coregistered CTA images as a guide. CTA-guided myocardial perfusion analysis, compared with standard MPS analysis, resulted in improved area under the receiver-operating-characteristic (ROC) curves for the detection of right coronary artery (RCA) and left circumflex artery (LCX) lesions (0.84 +/- 0.08 vs. 0.70 +/- 0.11 for LCX, P = 0.03, and 0.92 +/- 0.05 vs. 0.75 +/- 0.09 for RCA, P = 0.02).

CONCLUSION

Software image coregistration of stand-alone coronary CTA and MPS obtained on separate scanners can be performed rapidly and automatically, allowing CTA-guided contour and vascular territory adjustment on MPS for improved quantitative MPS analysis.

Scintigraphic evaluation of routine filterwire distal protection in percutaneous coronary intervention for acute ST-segment elevation myocardial infarction: a randomized controlled trial

AIM

Distal embolization during primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI) may result in reduced myocardial perfusion, infarct extension and impaired prognosis. In a prospective randomized trial, we assessed the effect of routine filterwire distal protection on scintigraphic estimated infarct size.

METHODS AND RESULTS

The effect of routine filterwire distal protection was evaluated in 344 patients with STEMI <12 hours undergoing primary PCI. Patients were randomized to distal protection with a filterwire or standard PCI. The primary endpoint was myocardial infarct size measured by Sestamibi SPECT after 30 days (%). Secondary endpoints included myocardial salvage, ST-segment resolution (STR), myocardial biomarker release and major adverse cardiac and cerebral events. Baseline characteristics including area at risk (estimated by Sestamibi SPECT) were similar. Final infarct size was not statistically different in the distal protection and the control groups (median [IQR], 6% [1-19] and 5% [1-14], P = .23). Also, secondary endpoints were similar in the two treatment groups.

CONCLUSION

Distal protection with a filterwire performed as routine therapy in primary PCI for STEMI did not reduce myocardial infarct size. The study does not support routine use of distal protection in primary PCI.

The effects of technological developments on nuclear medicine technologist productivity: a systematic review

OBJECTIVES

Nuclear medicine has changed rapidly as a result of technological developments. Very little is reported on the effects these developments may have on technologist productivity. This study aims to determine whether advances have created a workplace where more patient studies can be performed with fewer technologists. The level of change in automation or time taken to perform a routine task by the nuclear medicine technologist as a result of technological development over the past decade is reported.

METHODS

A systematic review was conducted using Embase.com, Medline, INSPEC, and Cinahl. Two authors reviewed each article for eligibility. Technological developments in routine areas over the past decade were reviewed. The resultant automation or time effects on data acquisition, data processing, and image processing were summarized.

RESULTS

Sixteen articles were included in the areas of myocardial perfusion, information technology, and positron emission tomography (PET). Gamma camera design has halved the acquisition time for myocardial perfusion studies, automated analysis requires little manual intervention and information technologies and filmless departments are more efficient. Developments in PET have reduced acquisition to almost one-fifth of the time.

CONCLUSIONS

Substantial efficiencies have occurred over the decade thereby increasing productivity, but whether staffing levels are appropriate for safe, high quality practice is unclear. Future staffing adequacy is of concern given the anticipated increasing service needs.

Motion-frozen myocardial perfusion SPECT improves detection of coronary artery disease in obese patients

In this study, we compared the diagnostic performance of the standard SPECT with motion-frozen (MF) myocardial perfusion SPECT (MPS) in obese patients.

METHODS

A total of 90 consecutive obese patients (body mass index, 30.1-46.8, average, 34.3 +/- 3.6; age, 63 +/- 12 y; 30% women) underwent standard supine rest (201)Tl/stress (99m)Tc dual-isotope gated MPS and cardiac catheterization within 3 mo. MF images were obtained by nonlinear warping of cardiac phases to the end-diastolic position. Total perfusion deficit (TPD) was obtained for summed (S-TPD) and motion-frozen (MF-TPD) datasets with sex-specific standard and MF normal limits.

RESULTS

The area under the receiver-operating-characteristic (ROC) curve for detection of coronary artery disease (CAD) by MF-TPD was significantly larger than that for S-TPD (0.93 +/- 0.25 vs. 0.88 +/- 0.32, P < 0.05). MF-TPD had higher specificity (77% vs. 55%, P < 0.05) and accuracy (89% vs. 80%, P < 0.05) than did S-TPD.

CONCLUSION

MF processing of MPS improves CAD detection in obese patients.

Diagnosis and treatment of musculoskeletal chest pain: design of a multi-purpose trial

Background

Acute chest pain is a major health problem all over the western world. Active approaches are directed towards diagnosis and treatment of potentially life threatening conditions, especially acute coronary syndrome/ischemic heart disease. However, according to the literature, chest pain may also be due to a variety of extra-cardiac disorders including dysfunction of muscles and joints of the chest wall or the cervical and thoracic part of the spine. The diagnostic approaches and treatment options for this group of patients are scarce and formal clinical studies addressing the effect of various treatments are lacking.

Methods/Design

We present an ongoing trial on the potential usefulness of chiropractic diagnosis and treatment in patients dismissed from an acute chest pain clinic without a diagnosis of acute coronary syndrome. The aims are to determine the proportion of patients in whom chest pain may be of musculoskeletal rather than cardiac origin and to investigate the decision process of a chiropractor in diagnosing these patients; further, to examine whether chiropractic treatment can reduce pain and improve physical function when compared to advice directed towards promoting self-management, and, finally, to estimate the cost-effectiveness of these procedures. This study will include 300 patients discharged from a university hospital acute chest pain clinic without a diagnosis of acute coronary syndrome or any other obvious cardiac or non-cardiac disease. After completion of the clinic's standard cardiovascular diagnostic procedures, trial patients will be examined according to a standardized protocol including a) a self-report questionnaire; b) a semi-structured interview; c) a general health examination; and d) a specific manual examination of the muscles and joints of the neck, thoracic spine, and thorax in order to determine whether the pain is likely to be of musculoskeletal origin. To describe the patients status with regards to ischemic heart disease, and to compare and indirectly validate the musculoskeletal diagnosis, myocardial perfusion scintigraphy is performed in all patients 2–4 weeks following discharge. Descriptive statistics including parametric and non-parametric methods will be applied in order to compare patients with and without musculoskeletal chest pain in relation to their scintigraphic findings. The decision making process of the chiropractor will be elucidated and reconstructed using the CART method. Out of the 300 patients 120 intended patients with suspected musculoskeletal chest pain will be randomized into one of two groups: a) a course of chiropractic treatment (therapy group) of up to ten treatment sessions focusing on high velocity, low amplitude manipulation of the cervical and thoracic spine, mobilisation, and soft tissue techniques. b) Advice promoting self-management and individual instructions focusing on posture and muscle stretch (advice group). Outcome measures are pain, physical function, overall health, self-perceived treatment effect, and cost-effectiveness.

Discussion

This study may potentially demonstrate that a chiropractor is able to identify a subset of patients suffering from chest pain predominantly of musculoskeletal origin among patients discharged from an acute chest pain clinic with no apparent cardiac condition. Furthermore knowledge about the benefits of manual treatment of patients with musculoskeletal chest pain will inform clinical decision and policy development in relation to clinical practice.

Trial registration

NCT00462241 and NCT00373828

Effect of streptozotocin-induced diabetes on left ventricular function in adult rats: an in vivo Pinhole Gated SPECT study

BACKGROUND

Recent studies have suggested that diabetes mellitus (DM) may cause left ventricular (LV) dysfunction directly resulting in increased susceptibility to heart failure. Using pinhole collimators and advances in data processing, gated SPECT was recently adapted to image the rat heart. The present study was aimed to assess this new imaging technique for quantifying LV function and remodeling from the Streptozotocin (STZ) rat model compared to controls.

METHODS

Twenty one rats were randomly assigned to control or diabetic group. Six months after the induction of diabetes by STZ, Pinhole 99 m Tc-sestamibi gated SPECT was performed for determining rat LV volumes and function. Post-mortem histopathologic analysis was performed to evaluate the determinant of LV remodeling in this model.

RESULTS

After six months, the normalized to body weight LV End-systolic volume was significantly different in diabetic rats compared to controls (0.46 +/- 0.02 vs 0.33 +/- 0.03 microL/g; p = 0.01). The normalized LV End-diastolic volume was also different in both groups (1.51 +/- 0.03 vs 0.88 +/- 0.05 microL/g; p = 0.001) and the normalized stroke volume was significantly higher in STZ-rats (1.05 +/- 0.02 vs 0.54 +/- 0.06 microL/g; p = 0.001). The muscular fibers were thinner at histology in the diabetic rats (0.44 +/- 0.07 vs 0.32 +/- 0.06 AU; p = 0.01).

CONCLUSION

Pinhole 99 m Tc-sestamibi gated SPECT can successfully be applied for the evaluation of cardiac function and remodeling in STZ-induced diabetic rats. In this model, LV volumes were significantly changed compared to a control population, leading to a LV dysfunction. These findings were consistent with the histopathological abnormalities. Finally, these data further suggest the presence of diabetes cardiomyopathy.

Quantitation of infarct size in patients with chronic coronary artery disease using rest-redistribution Tl-201 myocardial perfusion SPECT: correlation with contrast-enhanced cardiac magnetic resonance

BACKGROUND

Rest and rest-redistribution thallium 201 myocardial perfusion single photon emission computed tomography (SPECT) (MPS) has been incompletely validated in patients for determination of the total amount of scarred myocardium. We sought to determine whether rest or redistribution Tl-201 MPS provides an accurate determination of infarct size as defined by delayed contrast-enhanced cardiac magnetic resonance (CMR).

METHODS AND RESULTS

We studied patients (n = 44) with chronic coronary artery disease referred for rest-redistribution Tl-201 MPS, who were also studied by contrast-enhanced CMR within 3 +/- 4 days. Patients were considered retrospectively based on a series of patients referred for clinically indicated MPS. Defect size, as a percent of left ventricular mass (% LV), was determined by quantitative perfusion SPECT (QPS) and compared with the volume of delayed hyperenhancement on contrast-enhanced CMR, normalized to LV mass. Infarct size varied from 0% to 43% LV. Rest QPS defect size correlated with the amount of nonviable myocardium assessed by contrast-enhanced CMR (r = 0.76; mean difference, 4.3% +/- 8.0% LV). When delayed thallium data were considered, redistribution QPS was superior to rest QPS for determination of infarct size (redistribution r = 0.90; mean difference, 2.4% +/- 5.2% LV; P = .03 vs rest).

CONCLUSION

Rest-redistribution Tl-201 MPS provides a more accurate measurement of total infarct size than rest-only Tl-201 MPS and correlates with contrast-enhanced CMR.

Subendocardial versus transmural ischaemia in myocardial perfusion SPECT--a Monte Carlo study

Myocardial perfusion imaging with single-photon emission computed tomography (SPECT) is useful for the evaluation of patients with known or suspected coronary artery disease. Parameters of interest are the reduction in the blood perfusion (severity) and the lesion volume (extent). The aim of this study was to evaluate these parameters, as calculated by automatic quantification software, for different cases of subendocardial and transmural myocardial lesions.

METHODS

A computer phantom was used to simulate 32 male patients with different defect locations and activity uptakes, which were based on clinical patient studies. The Monte Carlo program SIMIND was used to simulate realistic SPECT projections which were reconstructed to give short-axis images, analysed by the AutoQUANT program using the same procedure as for a real patient.

RESULTS

The results showed a disparity between the quantification of transmural and subendocardial lesions with the same lesion activity uptake reduction and this could be confirmed by visual interpretation. Neither the parameters given by the quantification program nor visual interpretation could distinguish between the transmural lesions and the subendocardial lesions with activity uptake reduction twice as high as in the corresponding transmural lesions.

CONCLUSION

Transmural lesions and the corresponding subendocardial lesions with the same activity uptake reduction could be separated by the quantification software for SPECT imaging and visual analysis. The subendocardial lesions with activity uptake reduction twice as high as in the corresponding transmural lesions could not be differentiated neither by the quantification software nor by visual interpretation. Thus these lesions will get the same scoring when analysed by the AutoQUANT program.

Variation in heart rate influences the assessment of transient ischemic dilation in myocardial perfusion scintigraphy

BACKGROUND

Transient arrhythmias can affect transient ischemic dilation (TID) ratios. This study was initiated to evaluate the frequency and effect of normal heart rate change on TID measures in routine clinical practice.

METHODS

Consecutive patients undergoing stress/rest sestamibi gated myocardial perfusion scintigraphy were studied (N = 407). Heart rate at the time of stress and rest imaging were recorded. TID ratios were analyzed in relation to absolute change in heart rate (stress minus rest) for subjects with normal perfusion and systolic function (Group 1, N = 169) and those with abnormalities in perfusion and/or function (Group 2, N = 238).

RESULTS

In Group 1, mean TID ratio was inversely correlated with the change in heart rate (r = -0.47, P < 0.0001). For every increase of 10 BPM in heart rate change, the TID ratio decreased by approximately 0.06 (95% confidence interval 0.04-0.07). In Group 2, multiple linear regression demonstrated that the change in heart rate (beta = -0.25, P < 0.0001) and the summed difference score (beta = 0.36, P < 0.0001) were independent predictors of the TID ratio.

CONCLUSION

Normal variation in heart rate between the stress and rest components of myocardial perfusion scans is common and can influence TID ratios in patients with normal and abnormal cardiac scans.

Outcome of patients with adenosine-induced ST-segment depression but with normal perfusion on tomographic imaging

Most patients with ST depression during adenosine infusion have reversible perfusion defects by single-photon emission computed tomographic (SPECT) perfusion images. Occasionally ST depression is observed in the setting of normal perfusion images. The outcome of such patients is controversial. We identified 65 patients who underwent gated SPECT perfusion imaging with adenosine as the stress agent. These patients were selected based on the following criteria: none had previous myocardial infarction or coronary revascularization, all were in sinus rhythm, and none had left bundle branch block. The 65 patients had normal SPECT images but ischemic ST response (>or=1 mm ST depression). There were 52 women and 13 men who were 66 +/- 13 years of age. History of diabetes mellitus was present in 16 patients (25%) and hypertension in 48 patients (74%). At a mean follow-up of 24 months, there were no cardiac deaths or myocardial infarctions, and there were 6 coronary revascularization procedures (2 coronary artery bypass graftings and 4 coronary stentings of 1-vessel coronary disease). One patient died of cancer. In conclusion, patients with no previous myocardial infarction or coronary revascularization who have normal SPECT images have a benign outcome despite the presence of ST depression (0% for death or myocardial infarction and 4.6%/year for coronary revascularization). Balanced ischemia could not be a common cause for discordant perfusion and ST response.

Routine thrombectomy in percutaneous coronary intervention for acute ST-segment-elevation myocardial infarction: a randomized, controlled trial

BACKGROUND

Distal embolization during primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction may result in reduced myocardial perfusion, infarct extension, and impaired prognosis.

METHODS AND RESULTS

In a prospective randomized trial, we studied the effect of routine thrombectomy in 215 patients with ST-segment-elevation myocardial infarction lasting <12 hours undergoing primary PCI. Patients were randomized to thrombectomy pretreatment or standard PCI. The primary end point was myocardial salvage measured by sestamibi SPECT, calculated as the difference between area at risk and final infarct size determined after 30 days (percent). Secondary end points included final infarct size, ST-segment resolution, and troponin T release. Baseline variables, including ST-segment elevation and area at risk, were similar. Salvage was not statistically different in the thrombectomy and control groups (median, 13% [interquartile range, 9% to 21%] and 18% [interquartile range, 7% to 25%]; P=0.12), but 24 patients in the thrombectomy group and 12 patients in the control group did not have an early SPECT scan, mainly because of poor general or cardiac condition (P=0.04). In the thrombectomy group, final infarct size was increased (median, 15%; [interquartile range, 4% to 25%] versus 8% [interquartile range, 2% to 18%]; P=0.004).

CONCLUSIONS

Thrombectomy performed as routine therapy in primary PCI for ST-elevation myocardial infarction does not increase myocardial salvage. The study suggests a possible deleterious effect of thrombectomy, resulting in an increased final infarct size, and does not support the use of thrombectomy in unselected primary PCI patients.

Prognostic utility of sestamibi lung uptake does not require adjustment for stress-related variables: a retrospective cohort study

Background

Increased ^99mTc-sestamibi stress lung-to-heart ratio (sLHR) has been shown to predict cardiac outcomes similar to pulmonary uptake of thallium. Peak heart rate and use of pharmacologic stress affect the interpretation of lung thallium uptake. The current study was performed to determine whether ^99mTc-sestamibi sLHR measurements are affected by stress-related variables, and whether this in turn affects prognostic utility.

Methods

sLHR was determined in 718 patients undergoing ^99mTc-sestamibi SPECT stress imaging. sLHR was assessed in relation to demographics, hemodynamic variables and outcomes (mean follow up 5.6 ± 1.1 years).

Results

Mean sLHR was slightly greater in males than in females (P < 0.01) and also showed a weak negative correlation with age (P < 0.01) and systolic blood pressure (P < 0.01), but was unrelated to stress method or heart rate at the time of injection. In patients undergoing treadmill exercise, sLHR was also positively correlated with peak workload (P < 0.05) but inversely with double product (P < 0.05). The combined explanatory effect of sex, age and hemodynamic variables on sLHR was less than 10%. The risk of acute myocardial infarction (AMI) or death increased by a factor of 1.7–1.8 for each SD increase in unadjusted sLHR, and was unaffected by adjustment for sex, age and hemodynamic variables (hazard ratios 1.6–1.7). The area under the ROC curve for the unadjusted sLHR was 0.65 (95% CI 0.59–0.71, P < 0.0001) and was unchanged for the adjusted sLHR (0.65, 95% CI 0.61–0.72, P < 0.0001).

Conclusion

Stress-related variables have only a weak effect on measured sLHR. Unadjusted and adjusted sLHR provide equivalent prognostic information for prediction of AMI or death.

A model that accounts for the interdependence of extent and severity in the automatic evaluation of myocardial defects

BACKGROUND

The extent and severity are two important parameters when describing a regional defect in myocardial single-photon emission computed tomography (SPECT) perfusion imaging. Intuitively, these two parameters should be independent of each other, but we have shown in a previous study that there is an interdependence. This interdependence has been investigated in two commercially available analysis programs (AutoQUANT and 4D-MSPECT) using Monte Carlo-simulated SPECT data.

METHODS

An anthropomorphic digital computer phantom and a Monte Carlo program were used to generate SPECT data. Several defects of different volumes and lesion activity uptake reductions were simulated and evaluated. Comparison of the measures of extent and severity with their corresponding known values led to the development of a correction model based on least-squares parameter estimation. This model was then applied to a test group consisting of 10 different computer-simulated patients.

RESULTS

Our results showed that the interdependence was reduced significantly for most of our test cases after applying the correction method. The application of the correction model to the test group demonstrated that the model was robust with respect to different patient geometries. A further test with projections that simulated a perfect SPECT system revealed that the interdependence between the extent and severity was not caused by the limited spatial resolution of the SPECT system, but rather the inherent design of the algorithms of the analysis programs.

CONCLUSIONS

A model has been developed to take into account the interdependence of the extent and severity.

Erroneous Left ventricular cavity size measurements on myocardial perfusion SPECT resulting from transient arrhythmias

Transient ischemic dilatation (TID) of the left ventricle during stress on myocardial perfusion imaging is a sign of severe coronary artery disease. Factors other than ischemia can transiently influence left ventricular size, however, and TID ratios can be misleading if these factors are not properly identified. We describe 4 cases of stress-rest Tc-99m sestamibi SPECT myocardial perfusion imaging in which both abnormally high and low TID ratios were seen as a result of the presence of transient supraventricular tachyarrhythmias that reduced cardiac filling time and corresponding left ventricular volumes.

Evaluation of the Quantitative Gated SPECT (QGS) software program in the presence of large perfusion defects

OBJECTIVES

To evaluate the reproducibility and operator dependence for the quantitative regional left ventricular functional parameters (LVFP) assessed by Cedars-Sinai's Quantitative automated gated SPECT (QGS) software.

METHODS

The QGS algorithm was reviewed in detail and potential operator dependencies were defined. Series of prototypes were selected, consisting of (a) normal perfusion, (b) perfusion defects in all perfusion regions, (c) perfusion studies of patients with angiographic confirmed normal coronary arteries, proximal (>or=70% stenoses) single and multiple vessel disease, and (d) spurious activity in close proximity. While defining and re-orienting the volume containing the left ventricle, the operator adjusted 8 variables/degrees of freedom (DF). The software was used without further operator interventions. Results were expressed as a coefficient of variation (COV). Separate COV were calculated per distinct DF. A segment was considered not robust when the COV did exceed 20% in a single DF, 15% in at least 2 DF, or 10% in at least 3 DF.

RESULTS

Regional left ventricular EF and volumes showed excellent reproducibility. Normal perfusion and the vessel disease prototypes showed an excellent COV (for all re-orientation steps [33/prototype]) mostly below 5% for LVFP. However, regional wall motion and thickening became less reliable in the presence of large perfusion defects or artifacts.

CONCLUSIONS

Quantitative estimates for regional left ventricular functional data show excellent reproducibility using automated gated SPECT. However, there may be substantial operator dependency in the presence of large defects or spurious activity in close proximity.

Left ventricular wall motion abnormalities as well as reduced wall thickness can cause false positive results of routine SPECT perfusion imaging for detection of myocardial infarction

AIMS

The relationship between wall thickness, wall thickening, wall motion, and single-photon emission computed tomography (SPECT) results for detection of myocardial infarction has never been systematically evaluated in a clinical setting. In particular, the discussion whether non-ischaemic regional wall motion abnormalities and reduced wall thickness can cause SPECT to be false positive for infarct detection remains unsettled.

METHODS AND RESULTS

We therefore evaluated patients presenting with left bundle branch block (LBBB) and only included them in the analysis if any coronary artery disease (CAD) had been ruled out by angiography. LBBB is known to cause septal wall motion abnormalities as well as to reduce systolic septal wall thickness. Thus, LBBB is a good non-ischaemic clinical model to evaluate the influence of wall thickness and wall motion on the homogeneity of tracer distribution in resting SPECT images. SPECT revealed fixed defects in all 139 patients initially identified for possible enrollment. CAD was found to be present by angiography in 120 patients. The remaining 19 patients without any CAD underwent cardiovascular magnetic resonance (CMR) and were included in the study. Evaluation of SPECT using a 72-segment model revealed septum-related fixed defects in all 19 patients. Every defect was interpreted as myocardial infarction by blinded observers. The comparison of nuclear results to the gold standard CMR demonstrated that none of the fixed SPECT defects did represent myocardial infarcts. Defects, however, exactly matched areas of wall motion abnormalities as well as regions with impaired wall thickness as demonstrated by CMR. On a segmental basis, we found a strong relationship between wall motion and reduced wall thickness on one hand and SPECT defects on the other hand. For example, only 5% of segments with normal wall motion were false positive by SPECT for myocardial infarction, whereas 93% of all dyskinetic segments were found to be false positive (P<0.01). Comparing wall thickness to SPECT results revealed that 58% of segment in which wall thickness was 1 SD below the mean and 93% of segments in which wall thickness was 2 SD below the mean showed fixed defects by SPECT. Conversely, only 0.5% of segments in which wall thickness was above the mean were affected by false positive SPECT results (P<0.01).

CONCLUSION

Wall motion abnormalities as well as impaired myocardial wall thickening and wall thickness can cause false positive results of resting SPECT myocardial perfusion imaging for detection of myocardial infarction in the absence of myocardial infarct scars and CAD.

Automated quantification of 99mTc sestamibi myocardial perfusion compared with visual analysis

OBJECTIVES

The visual interpretation of 99mTc sestamibi single photon emission computed tomography (SPECT) myocardial perfusion images can be challenging due to the quantity of scan information generated, the large number of normal variants, attenuation artifacts and gender differences. The development of automated, computer derived, quantitative indices of perfusion can assist in this interpretation by providing an objective measure. It is important to verify that similar results can be obtained when the software is used in centres outside those where the algorithms were initially developed. Our objective was to assess the degree of concordance between the visual and automated diagnostic assessments of 99mTc sestamibi SPECT.

METHODS

We studied 718 patients referred for 99mTc sestamibi SPECT myocardial perfusion imaging. The SPECT studies were initially interpreted visually without benefit of computer based analysis, and were then subjected to blinded reprocessing to extract quantitative indices of perfusion.

RESULTS

There was very good agreement between the visual and quantitative diagnostic classifications. When a visual abnormality was taken to be the reference standard, the automated summed stress score (SSS) showed agreement (SSS>3) in 80% (kappa 0.60, P<0.0001). The area under the receiver operating characteristic (ROC) curve was 0.89 (95% confidence interval (CI), 0.86-0.91). Concordance was greater in those with previous myocardial infarction or severe perfusion defects, but was not affected by age, prior revascularization, stress procedure or heart rate. Concordance over the presence or absence of visual reversibility and the summed difference score (SDS) in abnormal scans was slightly lower (overall agreement 73% (kappa 0.36, P<0.00001) and ROC area 0.84 (95% CI, 0.77-0.90)).

CONCLUSION

Automated quantification of 99mTc sestamibi SPECT myocardial perfusion with the SSS and SDS provides objective diagnostic information and concordance when compared with conventional visual image interpretation.

Quantitative single-photon emission computed tomography imaging

Over the past decade, quantitation of cardiac single-photon emission computed tomography (SPECT) data, once limited to perfusion assessment, has been extended to global and regional function assessment for both the left and the right ventricle, as well as to measurement of additional cardiac parameters of diagnostic and prognostic interest. A number of commercially available quantitative algorithms exist, based on different mathematic operators and with varying degrees of automation, that are capable of providing accurate and reproducible results. This article describes the many quantitative cardiac SPECT measurements available today, defining them in terms of validation, practical use, and limitations.

Effects of glucose-insulin-potassium solution on myocardial salvage and left ventricular function after primary angioplasty

OBJECTIVE

To evaluate the effects of glucose-insulin-potassium (GIK) therapy on infarct size and left ventricular function when used as an adjuvant therapy to primary angioplasty.

DESIGN

Prospective, randomized, double-blind, placebo-controlled study.

SETTING

Cardiac intensive care unit at a university hospital.

PATIENTS

Thirty-seven patients with acute myocardial infarction for whom primary angioplasty was indicated.

INTERVENTIONS

Eligible patients were randomized by a blinded pharmacist to GIK solution (30% glucose in water with insulin 50 U/L, and KCl 40 mM/L) vs. placebo at 1.5 mL/kg/hr for 24 hrs.

MEASUREMENTS AND MAIN RESULTS

Tc 99m sestamibi myocardial scintigraphy was performed at admission and at 3 months. Primary end points were the changes in left ventricular ejection fraction (LVEF) and the size of salvaged myocardium. Baseline clinical characteristics were similar in both groups. At the 3-month follow-up, a significant overall decrease in infarct size (37 +/- 16% vs. 12 +/- 10%, p <.005) and an increase in LVEF (34 +/- 13% vs. 49 +/- 9%, p =.005) were observed. Patients randomized to GIK solution experienced a significant increase in their LVEF at 3 months (39 +/- 12 to 51 +/- 13, p =.002). Patients who received placebo had no significant differences between baseline and 3-month measurements (44 +/- 13 vs. 49 +/- 14, p = NS). There was a trend toward an increase in myocardial salvage in the GIK group, which did not reach statistical significance. When patients from both groups were compared directly, differences in LVEF improvement were no longer significant.

CONCLUSIONS

GIK solution did not improve LVEF or decrease the infarct size among patients undergoing primary angioplasty.

Prediction of functional recovery after coronary bypass surgery using quantitative gated myocardial perfusion SPECT

Previous studies have demonstrated that myocardial perfusion imaging using 99mTc-tetrofosmin at rest allows viability assessment similar to that obtained with 201Tl imaging and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET). The simultaneous assessment of perfusion and regional function is now available by quantitative gated myocardial perfusion single-photon emission computed tomography (SPECT). This study was designed to evaluate the utility of quantitative values of wall motion and wall thickening, calculated by quantitative gated myocardial perfusion SPECT, for the prediction of functional recovery after coronary bypass grafting (CABG). Fifty-six patients with coronary artery disease scheduled for CABG were included prospectively. All patients underwent 99mTc-tetrofosmin gated SPECT imaging at rest preoperatively and 3 months after CABG. The myocardium was divided into nine segments and the average quantitative values of regional perfusion (percentage uptake) (%), wall motion (mm) and wall thickening (%) were determined automatically using quantitative gated SPECT (QGS) software. The wall motion score was defined visually using a four-point scale (0, normal; 3, akinesis), and segments with severe asynergy (score of 2 or 3) with patent grafts were assessed. Of 77 segments with severe asynergy, 56 segments showed improved wall motion and 21 segments did not improve after CABG. The area under the receiver operating characteristic curve of wall thickening for the prediction of functional recovery was significantly higher (0.92) than that of the percentage uptake (0.77, P<0.017) or wall motion (0.60, P<0.0001). When each analysis used the optimal threshold, the wall thickening analysis (>or=10%) had a sensitivity of 95% and a specificity of 81%. These values tended to be higher than those of the percentage uptake (sensitivity, 86%; specificity, 67%). The wall motion analysis (>or=1.5 mm) had a significantly lower sensitivity of 75% and specificity of 43% than the wall thickening analysis (P=0.0038 and P=0.011, respectively). The results indicate that wall thickening, calculated by QGS software, may be more useful than regional perfusion or wall motion analysis for the prediction of functional recovery after CABG. The areas of asynergy with relatively preserved wall thickening may have the potential for improved function despite severely decreased perfusion.

Comparison of automatic quantification software for the measurement of ventricular volume and ejection fraction in gated myocardial perfusion SPECT

The aim of this study was to compare the performance of three different software packages for the calculation of ejection fraction (EF) and end diastolic volume (EDV) from gated myocardial single photon emission computed tomography studies. Two hundred patients undergoing gated stress myocardial perfusion scans were analysed retrospectively. Patients were grouped as follows: small heart (n=31), normal perfusion scan (n=71), and scan with perfusion defects (n=98). EF and EDV were calculated for each using QGS (Cedars Sinai, Los Angeles, CA), 4D-MSPECT (University of Michigan, Ann Arbor, MI), and ECT (Emory University, Atlanta, GA). Bland-Altman plots, repeated measures ANOVA, and linear regression analysis were used to compare methods. Correlation coefficients between the methods for both EF and EDV were high, greater than 0.9. However, Bland-Altman plots revealed a large standard deviation of the difference between methods, preventing the confident estimate of the value of one method from an observation of another. Despite good correlation, the variance between methods was high. These algorithms behave differently, produce widely variable results from one another, and should not be used interchangeably. It may prove prudent for laboratories to independently validate the software algorithm that is chosen against a 'gold standard' using their own population.

Reproducibility of chronic infarct size measurement by contrast-enhanced magnetic resonance imaging

BACKGROUND

The reproducibility of contrast-enhanced MRI has not been established. We compared MRI reproducibility for infarct size determination with that of (99m)Tc-sestamibi (MIBI) single photon emission computed tomography (SPECT).

METHODS AND RESULTS

Patients with chronic myocardial infarction defined by enzymes (peak creatine kinase-MB 173+/-119 U/L) were scanned twice by MRI (MRI I and MRI II, n=20) and twice by SPECT (SPECT I and SPECT II, n=15) on the same day. The MRI contrast agent was injected during MRI I but not MRI II to test the effect of imaging time after contrast. Resting Tc-MIBI SPECT images were acquired and infarct size was determined with commercial software. Infarct size in patients scanned by MRI and SPECT was 14+/-6% of left ventricular mass (%LV) by MRI (range 4%LV to 27%LV) and 14+/-7%LV by SPECT (range 4%LV to 26%LV). MRI I and II scans were performed 10+/-2 and 27+/-3 minutes after contrast, respectively. For MRI, the difference in infarct size between scans I and II (bias) was -0.1%LV, and the coefficient of repeatability was +/-2.4%LV. For SPECT, bias was -1.3%LV, and the coefficient of repeatability was +/-4.0%LV. Within individual patients, no systematic differences in infarct size were detected when the 2 MRI scans were compared, the 2 SPECT scans were compared, or MRI was compared to SPECT.

CONCLUSION

The size of healed infarcts measured by contrast-enhanced MRI does not change between 10 and 30 minutes after contrast. The clinical reproducibility of contrast-enhanced MRI for infarct size determination compares favorably with that of routine clinical SPECT.

Transmyocardial laser revascularization dose response: enhanced perfusion in a porcine ischemia model as a function of channel density

BACKGROUND

Transmyocardial laser revascularization (TMR) appears to provide symptomatic relief to patients with ischemic heart disease, but evidence that TMR enhances perfusion to ischemic myocardium remains limited. Furthermore, it is uncertain whether there exists a TMR dose-response relationship that is a function of channel number. We therefore compared restoration of blood flow as analyzed by rest and stress 99mTc-sestamibi scans and histologic grading of neovascularization after 50-channel, 25-channel, or 10-channel TMR using the excimer laser in an established model of porcine myocardial ischemia.

METHODS

Yorkshire swine underwent a thoracotomy and placement of an ameroid constrictor around the proximal circumflex coronary artery. Three weeks later, the animals underwent resting and adenosine stress 99mTc-sestamibi scans for evaluation of ischemia immediately before repeat thoracotomy and TMR with either 50 channels (n = 4), 25 channels (n = 4), or 10 channels (n = 4) in the circumflex territory. The animals underwent repeat perfusion analyses 4 weeks later, after which the animals were sacrificed and the hearts were perfusion fixed for histologic evaluation of neovascularization.

RESULTS

All animals survived to sacrifice. Semiquantitative analyses of the sestamibi perfusion scans 4 weeks after lasing demonstrated significant improvement (p < 0.04) in stress-induced ischemia in the 50-channel TMR animals, but not in the 25- or 10-channel TMR groups, as compared with scans obtained immediately before lasing. A computerized image analysis of perfusion scans similarly demonstrated an improvement in the area of ischemia of 42% +/- 22% in the scans obtained 4 weeks after lasing compared with scans obtained immediately before lasing in the 50-channel group (p < 0.004), but only a 12% +/- 9% improvement in the 25-channel group and an 8% +/- 4% improvement in the 10-channel group (p > 0.05). Histologic assessment of neovascularization demonstrated significantly greater number of microvessels per low-power field in the 50- versus the 25- and 10-channel groups (p < 0.001).

CONCLUSIONS

In an animal model of myocardial ischemia, TMR appears to enhance myocardial perfusion. A dose-response relationship related to channel number may be of significance when evaluating the efficacy of various treatment strategies.

Assessment of regional myocardial wall motion and thickening by gated 99Tcm-tetrofosmin SPECT: a comparison with magnetic resonance imaging

Gated single photon emission computed tomography (SPECT) imaging allows the simultaneous assessment of both perfusion and function by using one single study. The assessment of regional wall motion and thickening pattern with gated SPECT allows viability studies to be performed. Magnetic resonance imaging (MRI) is well validated for the assessment of myocardial wall motion and thickening in patients with normal and impaired ventricular function. The aim of the study was to analyse the concordance between wall motion and thickening scores derived by gated SPECT and MRI imaging. Furthermore, the agreement for myocardial wall motion and thickening according to myocardial perfusion was analysed with both techniques. We studied a group of 21 patients, including 13 with a previous myocardial infarction (all more than 4 months before the study), using both gated SPECT 99Tcm-tetrofosmin myocardial perfusion imaging and MRI. A 13-segment model was used for both gated SPECT and MRI and each segment was visually scored using a scale of 1-3 for wall motion and thickening. There was a high agreement between gated SPECT and MRI for both wall motion (229/273, 84%; k = 0.72, P<0.001) and wall thickening (236/273, 86%; k = 0.77, P<0.001). The agreement for wall motion and thickening was 80% (k = 0.66) and 83% (k = 0.70), respectively, for patients with myocardial infarction; and 90% (k = 0.81) and 92% (k = 0.86), respectively (P = NS), for patients without myocardial infarction. Agreement in segmental wall motion and thickening scores between gated SPECT and MRI was 90% (k = 0.80) and 91% (k = 0.84), respectively, for segments with normal or mild to moderate hypoperfusion; and 71% (k = 0.45) and 77% (k = 0.57), respectively, for segments with severe hypoperfusion or no perfusion. Of the 70 (41%) segments that had severely diminished or no perfusion in post-myocardial infarction patients, 22 (31%) showed preserved wall motion and 17 (24%) showed preserved wall thickening both by gated SPECT and MRI, suggesting residual myocardial viability in malperfused segments. Our results suggest that gated SPECT imaging is a reliable tool for the assessment of regional wall motion and thickening in patients with known or suspected coronary artery disease. In patients with a previous myocardial infarction gated SPECT imaging has the potential to detect preserved wall motion and thickening in regions with fixed perfusion defects indicating the potential presence of residual myocardial viability.