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This chapter examines how cardiac single-photon emission computed tomography (SPECT) images are processed by computer to provide physicians with valuable displays and analyses of the images. Advancements in computer methods have evolved in key areas such as total automation, data-based quantification of myocardial perfusion, measurement of parameters of left-ventricular global and regional function, three-dimensional displays of myocardial perfusion and function, image fusion and the use of artificial intelligence (AI), and data mining techniques in decision support systems. Assistance in the interpretation of medical images by decision-support systems has made significant progress, mostly because of the implementation of AI. This chapter emphasizes on two AI techniques that are currently being applied to nuclear medicine, namely, expert systems and neural networks. These advancements in computer methods applied to higher-quality images from instrumentation advancements have resulted in tools that allow clinicians to make a more comprehensive and accurate assessment of their patient's myocardial status. The advancements have continued to strengthen the already strong role of myocardial perfusion SPECT imaging in the diagnosis and prognosis of patients with coronary artery disease.

A method for automatic unification of three-dimensional models of the coronary artery tree from biplane angiograms and three-dimensional models of the left ventricular epicardial surface from perfusion SPECT is introduced. The efficacy of the technique is evaluated using six swine models. The results are shown to be satisfactory in all cases.

Interpretation of cardiac perfusion SPECT images, and the subsequent reporting of results to referring physicians, are sometimes taken to be outside the sphere of the nuclear medicine technologist. However, all personnel involved with nuclear medicine procedures contribute to the timeliness and usefulness of the final report. The goal of this article is to review the principles of scan interpretation and reporting, from the standpoint of what technologists need to understand about these processes. In addition, software tools to aid these processes will be discussed, including quantitative image analysis, telemedicine, computer-aided scan interpretation, databases, computer-aided reporting, and Internet-based reporting. Finally, the accuracy of the scan report will be related to the tasks normally performed by technologists, such as the acquisition and processing of images and the entry, transfer, and networking of data. After reading this article, the reader will be able to describe the principles of scan interpretation and reporting, the software tools for telemedicine and computer-aided interpretation, and the role of the technologist in this process.

A processing program for analysis of left ventricular perfusion, anatomy, and function from single photon emission computed tomographic perfusion images is presented. This program combines a well-known and validated perfusion quantification approach with a left ventricular surface modeler which enables computation of local and global functional parameters. Thus, perfusion and function can be associated and compared. The results can be displayed in two or three dimensions, using slice displays, polar plots, or surface-shaded 3-D graphics. Finally, the abilities to align a 3-D coronary artery tree with the 3-D left ventricular epicardial surface and display the unification results have been provided, to allow for comparison between coronary anatomy and left ventricular structure and function. Each portion of the analysis package has been separately validated.

Two methods of computing left ventricular volumes and ejection fraction (EF) from 8-frame gated perfusion single photon emission computed tomography (SPECT) were compared with each other and with magnetic resonance (MR) imaging. Thirty-five subjects underwent 8-frame gated dual-isotope SPECT imaging and 12- to 16-frame gated MR imaging. Endocardial boundaries on short-axis MR images were hand traced by experts blinded to any SPECT results. Volumes and EF were computed with the use of Simpson’s rule. SPECT images were analyzed for the same functional variables with the use of 2 automatic programs, Quantitative Gated SPECT (QGS) and the Emory Cardiac Toolbox (ECTb). The mean difference between MR and SPECT EF was 0.008 for ECTb and 0.08 for QGS. QGS showed a slight trend toward higher correlation for EF (r = 0.72, SE of the estimate = 0.08) than ECTb (r = 0.70, SE of the estimate = 0.09). For both SPECT methods, left ventricular volumes were similarly correlated with MR, although SPECT volumes were higher than MR values by approximately 30%. QGS and ECTb values of cardiac function computed from 8-frame gated perfusion SPECT correlate very well with each other and correlate well with MR. Averaged over all subjects, ECTb measurements of EF are not significantly different from MR values but QGS significantly underestimates the MR values.

A new implementation of the iterative closest point method for automatic registration is introduced. It is designed to unify three-dimensional models of the coronary artery tree created from biplane angiograms with three-dimensional models of the left ventricular epicardial surface created from perfusion SPECT. The speed and efficacy of the technique is evaluated using simulations and five patient studies. The technique is shown to be fast and quantitatively accurate in the simulations; evaluations of the results in patients are also satisfactory.

To evaluate an improved camera-based method for calculating the clearance of technetium-99m mercaptoacetyltriglycine (MAG3) in a multicenter trial.Tc-99m MAG3 scintigraphy was performed in 49 patients at three sites in the United States and Canada. The percentage of the injected dose of Tc-99m MAG3 in the kidney at 1-2, 1.0-2.5, and 2-3 minutes after injection was correlated with the plasma-based Tc-99m MAG3 clearances. The data were combined with the results obtained in 20 additional patients in a previously published pilot study.Regression models correlating the plasma-based Tc-99m MAG3 clearance with the percentage uptake in the kidney for each time interval were developed; there was no statistically significant difference among sites in the regression equations. Correction for body surface area statistically significantly (P.005) improved the correlation coefficient for each time interval. For the 1.0-2.5-minute interval, the body surface area-corrected correlation coefficient for the four combined sites was .87, and it improved to .93 when one outlier was omitted from the analysis. Similar results were obtained with the other time intervals. Independent processing by two observers showed no clinically important differences in the percentage dose in the kidney or in relative function.An improved camera-based method to calculate the clearance of Tc-99m MAG3 was validated in a multicenter trial.

Objectives: To determine gender-matched normal values of TID index using attenuation corrected (AC) and non AC rest/exercise stress Tc-99m sestamibi myocardial perfusion SPECT imaging (MPI) in patients with low likelihood of CAD. Methods: 75 patients (33 females (F) and 42 males (M)) with Results: Mean and standard deviation (SD) TID values and normal limits (NL) (Mean + 2SD) are shown below for each population. No significant differences in TID were found between AC and non-AC studies whether genders were combined or separated. Importantly, a trend was found in non-AC studies with females having a higher NL TID than males. This trend became statistically significant in the AC studies. ;*>p AC TID Non AC TID ALL M F ALL M F Mean 0.97 0.95 1.01 0.98 0.97 1.00 SD 0.14 0.12 0.15 0.12 0.10 0.15 NL 1.25 1.18;*> 1.31;*> 1.23 1.17 1.30 Conclusions: Attenuation correction does not change the normal TID value compared to conventional non-AC studies. A significantly higher normal TID value was found in attenuation corrected females compared to AC males. Diagnosticians should be aware of these results when using TID as a marker of extensive ischemia considering that previous normal values of TID have not been gender-matched and generated from heavily weighted male populations.

This study examines the importance of left ventricular (LV) dilatation, and evidence of multivessel coronary artery disease identified on thallium-201 (TI-201) single-photon emission computed tomographic (SPECT) scintigrams, for predicting long-term outcome in patients with an extensive left anterior descending (LAD) perfusion deficit. Impaired contractility of the left ventricle determined by low ejection fraction, elevated LV end-systolic volume, and dilatation of the left ventricle are known as major predictors of mortality after myocardial infarction. TI-201 single-photon emission computed tomography primarily reveals status of perfusion/redistribution, but also contains indirect information on LV function. To date, there are no TI-201 SPECT data on impaired function of the left ventricle (LV dilatation) and extent of perfusion deficits, discussed together as correlates of survival. Patient data were prospectively collected in the computer data base at Emory University. A large perfusion defect involving more than one third of the LAD territory was identified in 291 of 2,652 consecutive patients examined with TI-201 SPECT initial and 3-hour redistribution studies. Follow-up data were obtained for 284 patients (98%) at 38 +/- 14 months. Of the 291 patients, 58 died. The most powerful multivariate correlates of death were LV dilatation, multivessel disease, and the ratio of the LAD severity stress score to total severity of SDs stress score. Cox model analysis was used to determine correlates of survival. Three-year survival for patients with LV dilatation was 73% versus 89% without LV dilatation (p0.001). Three-year survival in patients with 1-vessel disease ("LAD only") was 94% versus 78% for multivessel disease (p0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Most reports to date using single photon emission computed tomography (SPECT) with technetium-99m (Tc-99m) sestamibi have used acquisition parameters that were optimized for thallium-201. To fully utilize the superior imaging characteristics of Tc-99m sestamibi, there is a need to optimize the technical aspects of SPECT imaging for this agent. Performance can be enhanced through the careful selection of optimal radiopharmaceutical doses, imaging sequences, acquisition parameters, reconstruction filters, perfusion quantification methods and multidimensional methods for visualizing perfusion distribution. The current report describes theoretical considerations, phantom studies and preliminary patient results that have led to optimized protocols, developed at Emory University and Cedars-Sinai Medical Center, for same-day reststress studies, given existing instrumentation and recommended dose limits. The optimizations were designed to fit a low-dose-high-dose rest-stress same-day imaging protocol. A principal change in the acquisition parameters compared with previous Tc-99m sestamibi protocols is the use of a highresolution collimator. The approach is being developed in both prone and supine positions. A new method for extracting a 3-dimensional myocardial count distribution has been developed that uses spherical coordinates to sample the apical region and cylindrical coordinates to sample the rest of the myocardium. New methods for visualizing the myocardial distribution in multiple dimensions are also described, with improved 2-dimensional, as well as 3- and 4-dimensional (3 dimensions plus time) displays. In the improved 2-dimensional display, distance-weighted and volume-weighted polar maps are used that appear to significantly improve the representation of defect location and defect extent, respectively. The protocols established and the methods developed for acquisition, quantification and display of Tc-99m sestamibi SPECT should provide improved image quality and accuracy, compared to current thallium-201 and Tc-99m sestamibi studies reported to date.

Objective: To compare the diagnostic performance of automatic vs. manual processing of ECTb v2.5, QPS v3.0, and 4DMSPECT (4DM) v2.3b quantitative programs in the assessment of CAD. Methods: 94 patients who had rest Tl and maximal exercise gated sestamibi MPI were used. Sixty-five of the 94 patients had stenosis ≥50%. The heart was automatically found by each program. This step failed in 4 patients using ECTb, 2 patients using QPS and 8 patients using 4DM, and in these cases the LV was manually located. All studies were first processed totally automatically (Auto), followed by an expert technologist manually modifying the parameters (21 ECTb, 17 QPS, and 39 4DM). ROC curves were generated using the extent of perfusion defect, as a percentage of LV myocardium and of each vascular territory. Coronary angiography was used as a gold standard. Results: The areas under the ROC curves were similar using either automatic or manually corrected parameters (p = NS). However, manual correction seemed to improve slightly the results of ECTb and 4DM for the diagnosis of CAD and localization of disease, except for the RCA, for which the ECTb results were lower. For QPS automatic processing provided better results than manual processing, except for the RCA. Conclusion: The accuracy of automatic and manually corrected processing by ECTb, QPS and 4MD are similar in the detection and localization of CAD. Automatic processing by these programs is robust and accurate and should generally not be overridden except in the few cases where they totally fail. Area under the ROC curve CAD LAD LCX RCA Auto ECTb 0.65 0.58 0.62 0.75 Manual ECTb 0.67 0.60 0.65 0.73 Auto QPS 0.65 0.55 0.61 0.71 Manual QPS 0.64 0.54 0.58 0.72 Auto 4DM 0.62 0.56 0.58 0.71 Manual 4DM 0.63 0.58 0.60 0.73

Background: We evaluated the effect of LV positional differences on detection of serial perfusion changes. Methods: We used the NCAT software phantom to simulate three different shaped LVs based on actual patient studies. A small (∼10% of the myocardium) single defect was simulated for each of the three patients; the severity of each defect was varied in 5% increments from .5 of LV maximum perfusion for 6 steps, with each severity repeated. This provided a total of 12 simulations for each patient. Random LV rotations (stdev=2.5°), translations (stdev=0.5cm), and small scaling factors ( Results: In the repeated studies, where no difference in defect severity should be detected, a mean difference of 1.3% of LV maximum was seen; this difference was significant (p Conclusion: Current perfusion quantification methods may underestimate actual perfusion changes in serial studies. Noise, detector response, and orientation differences may make small changes in small defects difficult to detect with statistical significance.