Diagnostic performance of low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT using the 530c CZT camera: quantitative vs visual analysis.

BACKGROUND: We set out to develop normal databases and prospectively validate abnormality criteria for a low-dose Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera. METHODS: All patients received 6 mCi rest/20 mCi stress doses of Tc-99m tetrofosmin. Rest and stress images were obtained over 7-9 and 5-7 minutes according to the chest size. Low-dose CT of the chest was obtained on a standalone CT scanner. Forty patients with very low likelihood (LLK) of coronary artery disease (CAD) were used to define the normal count distributions. The abnormality criteria were prospectively validated in 55 patients who had coronary angiography and in 40 patients with LLK of CAD. RESULTS: The results for quantitative non-attenuation-corrected (AC) and AC analysis and visual analysis were as follows: sensitivity of 79%, 85%, and 92% (P = NS) and specificity of 44%, 75%, and 56% (P = NS), respectively. The normalcy rates for quantitative non-AC and AC analyses and visual analysis were 95%, 98%, and 98% (P = NS). CONCLUSIONS: We have developed non-AC and AC normal databases for low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera. The per-patient diagnostic performance of quantitative analyses is not significantly different from visual analysis by an experienced reader.

Quantitative I-123 mIBG SPECT in differentiating abnormal and normal mIBG myocardial uptake.

BACKGROUND: The purpose of this study was to evaluate global quantitation of cardiac uptake on I-123 mIBG SPECT. METHODS: The study included a pilot group of 67 subjects and a validation group of 1,051 subjects. SPECT images were reconstructed by filtered backprojection, ordered subsets expectation maximization, and deconvolution of septal penetration, respectively. SPECT heart-to-mediastinum ratio (H/M) was calculated by comparing the mean counts between heart and mediastinum volumes of interest drawn on transaxial images. Receiver operating characteristic (ROC) analysis was used to assess the capability of each SPECT method to differentiate the heart disease subjects from controls in comparison with that of the planar H/M. RESULTS: In the validation group, the areas under the ROC curves were not significantly different between the SPECT and planar H/M. Order subsets expectation maximization had significantly larger area under the ROC curve than the other two SPECT methods. CONCLUSION: H/M obtained from I-123 mIBG SPECT was equivalent to the planar H/M for differentiating between subjects with normal and abnormal mIBG uptake. Global quantification of cardiac I-123 mIBG SPECT may represent a viable alternative to the planar H/M.

Left-ventricular systolic and diastolic dyssynchrony as assessed by multi-harmonic phase analysis of gated SPECT myocardial perfusion imaging in patients with end-stage renal disease and normal LVEF.

BACKGROUND: The purpose of this study was to develop a multi-harmonic phase analysis method to measure diastolic dyssynchrony from conventional gated SPECT myocardial perfusion imaging (MPI) data and to compare it with systolic dyssynchrony in normal subjects and in patients with end-stage renal disease (ESRD) and normal left-ventricular ejection fraction (LVEF). METHODS: 121 consecutive patients with ESRD and normal LVEF and 30 consecutive normal controls were enrolled. Diastolic dyssynchrony parameters were calculated using 3-harmonic phase analysis. Systolic dyssynchrony parameters were calculated using the established 1-harmonic phase analysis. RESULTS: The systolic and diastolic dyssynchrony parameters were correlated, but significantly different in both control and ESRD groups, indicating they were physiologically related but measured different LV mechanisms. The systolic and diastolic dyssynchrony parameters were each significantly different between the control and the ESRD groups. Significant systolic and diastolic dyssynchrony were found in 47% and 65% of the entire ESRD group. CONCLUSION: Multi-harmonic phase analysis has been developed to assess diastolic dyssynchrony, which measured a new LV mechanism of regional function from gated SPECT MPI and showed a significantly higher prevalence rate than systolic dyssynchrony in patients with ESRD and normal LVEF.

Diagnostic performance of fusion of myocardial perfusion imaging (MPI) and computed tomography coronary angiography.

BACKGROUND: We evaluated the incremental diagnostic value of fusion images of coronary computed tomography angiography (CTA) and myocardial perfusion imaging (MPI) over MPI alone or MPI and CTA side-by-side to identify obstructive coronary artery disease (CAD > 50% stenosis) using invasive coronary angiography (ICA) as the gold standard. METHODS: 50 subjects (36 men; 56 +/- 11 years old) underwent rest-stress MPI and CTA within 12-26 days of each other. CTAs were performed with multi-detector CT-scanners (31 on 64-slice; and 19 on 16-slice). 37 patients underwent ICA while 13 subjects did not because of low (<5%) pre-test likelihood (LLK) of disease. Three blinded readers scored the images in sequential sessions using (1) MPI alone (2) MPI and CTA side-by-side, (3) fused CTA/MPI images. RESULTS: One or more critical stenoses during ICA were found in 28 patients and non-critical stenoses were found in 9 patients. MPI, side-by-side MPI-CTA, and fused CTA/MPI showed the same normalcy rate (NR:13/13) in LLK subjects. The fusion technique performed better than MPI and MPI and CTA side-by-side for the presence of CAD in any vessel (overall area under the curve (AUC) for fused images: 0.89; P = .005 vs MPI, P = .04 vs side-by-side MPI-CTA) and for localization of CAD to the left anterior descending coronary artery (AUC: 0.82, P < .001 vs MPI; P = .007 vs side-by-side MPI-CTA). There was a non-significant trend for better detection of multi-vessel disease with fusion. CONCLUSIONS: Using ICA as the gold standard, fusion imaging provided incremental diagnostic information compared to MPI alone or side-by-side MPI-CTA for the diagnosis of obstructive CAD and for localization of CAD to the left anterior descending coronary artery.

Adenosine stress rubidium-82 PET/computed tomography in patients with known and suspected coronary artery disease.

BACKGROUND: Integrated positron emission tomography/computed tomography (PET/CT) is increasingly being utilized for myocardial perfusion imaging (MPI). However, there is a potential for increased imaging artifact compared with standard PET due to the different temporal resolution of PET and CT. We reviewed the diagnostic accuracy of adenosine stress Rb myocardial perfusion PET/CT to detect obstructive coronary artery disease (CAD) on invasive angiography at our institution. METHODS AND RESULTS: Seventy-five patients were included, 23 (13 men, mean age 55.8+/-11.8 years) with low likelihood of CAD and 52 (28 men, mean age 67.1+/-11.4 years) with intermediate to high pretest probability of disease. Coronary angiography was performed only in the latter 52 patients on average within 17 days of the MPI study. The test characteristics of PET/CT MPI were assessed using a threshold of >or=50 and >or=70% stenosis in one or more major coronary artery on invasive angiography. Dedicated software was used for registration, processing, and interpretation. Consensus interpretation of the tomographic PET slices using a 4-point scale (1=definitely normal, 2=probably normal, 3=probably abnormal, 4=definitely abnormal) was done by two readers blinded to clinical information. RESULTS: All MPI studies in the 23 low likelihood patients were normal. In the remaining 52 patients using a stenosis severity>or=50%, global sensitivity and specificity, negative and positive predictive value for detection of CAD were 86, 100, 57, and 100%. Using a stenosis severity>or=70%, these values changed to 90, 83, 71, and 87%. CONCLUSION: Adenosine stress Rb MPI using PET/CT with manual registration demonstrates diagnostic accuracy comparable with that of traditional PET MPI.

Prognostic performance of quantitative PET tools for stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment.

OBJECTIVES: This study was performed to determine the prognostic performance of quantitative PET tools in the stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment. METHODS: We applied four different quantitative tools to 104 consecutive patients with coronary artery disease and previous myocardial infarction who had undergone rest Rb/gated F-fluorodeoxyglucose (FDG) PET, to assess myocardial viability for potential revascularization. One of these tools was based on the FDG study alone and the other three tools assessed the extent of match/mismatch defects using FDG in comparison with a perfusion reference database. The four quantitative tools used in this research to define viability were (i) FDG alone, which calculates the percentage of left ventricular myocardium (LVM) that is above the 50% of the maximum LVM FDG counts, (ii) low flow match/mismatch, which determines the area with a 5% increase in normalized FDG counts in relation to defined resting perfusion defects as compared with a reference database, (iii) all regions match/mismatch, which computes the area with a 10% increase in normalized FDG counts in relation to the left ventricle resting perfusion distribution, and (iv) percentage max FDG match/mismatch, which defines the area with FDG uptake greater than 60% of the maximum LVM FDG counts within defined perfusion defects as determined by the reference database. The primary endpoint for this analysis was cardiac death. RESULTS: During the follow-up period (22+/-14 months), 19 patients (18%) died; in 17 of these the cause of death was cardiac. Using univariate analysis, none of the methods were predictive of cardiac death. Receiver operating characteristic analysis defined the optimal thresholds for the extent of myocardial viability for the four tools in the prediction of cardiac death: FDG alone=20%, low flow match/mismatch=15%, all regions match/mismatch=35%, and percentage max FDG match/mismatch=20%. A censored survival analysis using a Kaplan-Meier method showed a statistically significant difference between patients with cardiac death and those with no cardiac death using only the low flow match/mismatch (hazard ratio=0.29, P=0.01) and percentage max FDG match/mismatch criteria (hazard ratio=0.23, P=0.005) tools. CONCLUSION: The low flow match/mismatch and percentage max FDG match/mismatch quantitative PET tools are useful for prognostic stratification of patients with ischemic cardiomyopathy undergoing myocardial viability assessment.

Quantitative (82)Rb PET/CT: development and validation of myocardial perfusion database.

UNLABELLED: The use of myocardial perfusion (82)Rb PET/CT studies continues to increase but its accuracy using database quantification methods for the diagnosis of coronary artery disease (CAD) has not been established. METHODS: A sex-independent normal database and criteria for abnormality for rest-stress (82)Rb PET/CT myocardial perfusion imaging were developed and validated by evaluation of 281 patients (136 females: mean age +/- SD, 63.3 +/- 13.3 y; 145 males: mean age +/- SD, 63.9 +/- 12.8 y) who underwent a rest-adenosine stress (82)Rb PET/CT study. These patients were divided into 3 groups: (a) healthy group: 30 patients, with <5% likelihood of CAD (low likelihood [LLK]) based on sequential Bayesian analysis; these patients were used to generate the normal distribution; (b) pilot group: 174 patients; these patients were used to determine the optimal criteria for detecting and localizing the perfusion abnormality; and (c) validation group: 76 patients (23 with LLK of CAD and 53 who underwent coronary angiography; these patients were used for prospective validation. RESULTS: Of the 53 patients who underwent coronary angiography, 8 had <50% stenosis and 45 patients had at least one stenosis > or =50% in one major artery. Fifteen patients had single-vessel disease, 17 had double-vessel disease, and 13 had triple-vessel disease. The prospective validation shows a normalcy rate of 78% (18/23) for global CAD. The analyses by individual arteries show a normalcy rate of 96% (22/23) for the left anterior descending coronary artery, 96% for the left circumflex coronary artery (22/23), and 100% for the right coronary artery (23/23). The overall sensitivity for detection of CAD (> or =50% stenosis) was 93% (42/45). The overall specificity for detection of the absence of CAD (< or =50% stenosis) was 75% (6/8). Also, the positive predictive value for global CAD was 95% (42/44), the negative predictive value was 67% (6/9), and the accuracy was 91% (48/53). CONCLUSION: The quantitative (82)Rb PET/CT database created and validated in this study is highly accurate for the detection and localization of CAD. Physicians should consider using the quantitative output of these algorithms as decision support tools to aid with image interpretation.

Normal values and prospective validation of transient ischaemic dilation index in 82Rb PET myocardial perfusion imaging.

BACKGROUND: The use of Rb positron emission tomography (PET) for the diagnosis of coronary artery disease (CAD) has increased in recent years but the role of some of the traditional parameters used in SPECT for the diagnosis of CAD, such as transient ischaemic dilation index (TID) of the left ventricle, have not been validated in PET studies. METHODS AND RESULTS: We studied 95 patients who had undergone rest/pharmacological stress Rb PET scans. Thirty of these patients (18 female and 12 male) who had less than 5% likelihood of CAD (LLK) based on sequential Bayesian analysis, were used to determine the normal limits of TID index in this protocol. The remaining 65 patients (33 female and 32 male) underwent coronary angiography within 15 days of the cardiac PET scan. This second group of patients was used to validate the TID normal limits determined in the first group. In LLK patients mean TID index was 1.01+/-0.07 and there were no significant differences between genders. The TID index upper normal limit was 1.15 and was calculated as mean+2 SD. Using this cut-off point, TID index had high specificity and PPV in the diagnosis of single vessel CAD (100% and 100% respectively) and multiple vessel CAD (93% and 85%, respectively). CONCLUSION: Our results indicate that elevated TID index is a specific, although not sensitive marker of single and multiple vessel CAD in pharmacologically stressed Rb PET myocardial perfusion studies.

Development of a relational database to capture and merge clinical history with the quantitative results of radionuclide renography.

UNLABELLED: Our objective was to design and implement a clinical history database capable of linking to our database of quantitative results from (99m)Tc-mercaptoacetyltriglycine (MAG3) renal scans and export a data summary for physicians or our software decision support system. METHODS: For database development, we used a commercial program. Additional software was developed in Interactive Data Language. MAG3 studies were processed using an in-house enhancement of a commercial program. The relational database has 3 parts: a list of all renal scans (the RENAL database), a set of patients with quantitative processing results (the Q2 database), and a subset of patients from Q2 containing clinical data manually transcribed from the hospital information system (the CLINICAL database). To test interobserver variability, a second physician transcriber reviewed 50 randomly selected patients in the hospital information system and tabulated 2 clinical data items: hydronephrosis and presence of a current stent. The CLINICAL database was developed in stages and contains 342 fields comprising demographic information, clinical history, and findings from up to 11 radiologic procedures. A scripted algorithm is used to reliably match records present in both Q2 and CLINICAL. An Interactive Data Language program then combines data from the 2 databases into an XML (extensible markup language) file for use by the decision support system. A text file is constructed and saved for review by physicians. RESULTS: RENAL contains 2,222 records, Q2 contains 456 records, and CLINICAL contains 152 records. The interobserver variability testing found a 95% match between the 2 observers for presence or absence of ureteral stent (κ = 0.52), a 75% match for hydronephrosis based on narrative summaries of hospitalizations and clinical visits (κ = 0.41), and a 92% match for hydronephrosis based on the imaging report (κ = 0.84). CONCLUSION: We have developed a relational database system to integrate the quantitative results of MAG3 image processing with clinical records obtained from the hospital information system. We also have developed a methodology for formatting clinical history for review by physicians and export to a decision support system. We identified several pitfalls, including the fact that important textual information extracted from the hospital information system by knowledgeable transcribers can show substantial interobserver variation, particularly when record retrieval is based on the narrative clinical records.

Attenuation correction reveals gender-related differences in the normal values of transient ischemic dilation index in rest-exercise stress sestamibi myocardial perfusion imaging.

BACKGROUND: Transient ischemic dilation (TID) has been established as an important independent marker of severe and extensive coronary artery disease (CAD) in myocardial perfusion imaging (MPI). The accuracy of the TID index is dependent on a well-determined threshold (normal limits) between normal and abnormal values for each study protocol. To date, the effects of neither gender nor attenuation correction (AC) on TID normal limits have been established. Thus, the objectives of this study were to determine if AC processing changes the normal value of the TID index and if there were gender-related differences in the TID index of normal patients who had undergone rest/exercise-stress technetium-99m sestamibi MPI. METHODS AND RESULTS: Seventy-five patients (33 women, 42 men; mean age, 57.7 +/- 11.7 y and 55.9 +/- 10.0 y, respectively) with less than a 5% likelihood of CAD, who had undergone low-dose rest/high-dose exercise-stress Tc-99m sestamibi MPI, were studied. All studies were acquired using simultaneous emission/transmission scans and were corrected for attenuation, scatter, and resolution effects using the ExSPECT II method. Both the AC and non-AC studies were analyzed using the Emory Cardiac Toolbox (ECTb; Syntermed, Inc, Atlanta, Ga) quantitative software. The TID index was calculated automatically as the ratio of stress mean left ventricular volumes to rest mean left ventricular volumes by ECTb. Patients were grouped by gender and the TID indices from AC and non-AC studies were compared. Linear regressions of the TID index and body mass index were analyzed to exclude differences in body size between male and female patients as a confounding factor in gender-related differences in TID. The TID index upper normal limits were calculated as the mean value plus 2 standard deviations (SDs). AC processing did not change the TID index significantly whether the genders were combined or separated (AC TID = 0.97 +/- 0.14 vs non-AC TID = 0.98 +/- 0.12 for all patients). Female patients showed higher mean TID indices than male patients in both AC (1.01 +/- 0.15 vs 0.95 +/- 0.12) and non-AC studies (1.00 +/- 0.15 vs. 0.97 +/- 0.10), but this difference was statistically significant only in AC studies (p = .03). TID indices remained constant across the range of body mass index studied. The TID index upper normal limit was 1.31 for female and 1.18 for male patients. CONCLUSION: TID normal values for rest/exercise-stress Tc-99m sestamibi MPI are gender-dependent and not affected by AC processing. Thus, diagnosticians should take into account these gender-related differences, as compared with the traditional value generated from mostly male populations, to ensure both men and women have the same overall accuracy of using the TID index in the diagnosis and prognosis of CAD.