Left ventricular ejection and filling rate measurement based on the automatic edge detection method of ECG-gated blood pool single-photon emission tomography

Development of a new Python-based cardiac phantom for myocardial SPECT imaging

PURPOSE

The aim of this work was to develop a digital dynamic cardiac phantom able to mimic gated myocardial perfusion single photon emission computed tomography (SPECT) images.

METHODS

A software code package was written to construct a cardiac digital phantom based on mathematical ellipsoidal model utilizing powerful numerical and mathematic libraries of python programing language. An ellipsoidal mathematical model was adopted to create the left ventricle geometrical volume including myocardial boundaries, left ventricular cavity, with incorporation of myocardial wall thickening and motion. Realistic myocardial count density from true patient studies was used to simulate statistical intensity variation during myocardial contraction. A combination of different levels of defect extent and severity were precisely modeled taking into consideration defect size variation during cardiac contraction. Wall thickening was also modeled taking into account the effect of partial volume.

RESULTS

It has been successful to build a python-based software code that is able to model gated myocardial perfusion SPECT images with variable left ventricular volumes and ejection fraction. The recent flexibility of python programming enabled us to manipulate the shape and control the functional parameters in addition to creating variable sized-defects, extents and severities in different locations. Furthermore, the phantom code also provides different levels of image filtration mimicking those filters used in image reconstruction and their influence on image quality. Defect extent and severity were found to impact functional parameter estimation in consistence to clinical examinations.

CONCLUSION

A python-based gated myocardial perfusion SPECT phantom has been successfully developed. The phantom proved to be reliable to assess cardiac software analysis tools in terms of perfusion and functional parameters. The software code is under further development and refinement so that more functionalities and features can be added.

Depressed Exercise Peak Ejection Rate Detected on Ambulatory Radionuclide Monitoring Reflects End-Stage Cardiac Inotropic Reserve and Predicts Mortality in Ischaemic Cardiomyopathy

BACKGROUND

Fifteen patients with ischaemic cardiomyopathy and inducible ischaemia were studied to determine the mechanisms of mortality. Failure of the contractile reserve during daily life activities may reflect a prognostic index.

METHODS

Single photon emission cardiac tomography and radionuclide ambulatory monitoring (Vest) data were analysed in all patients with a 7-year follow-up.

RESULTS

At peak exercise on Vest, the 7 non-survivors (N-SURV) showed worse peak ejection rates (PERs) and ejection fractions (EFs) compared with the 8 survivors (SURV), (2 ± 0.6 vs. 3.3 ± 0.7; end-diastolic volumes (EDVs), P < 0.003), and (34 ± 10% vs. 50 ± 13%; P < 0.02), respectively. However, exercise peak filling rates (PFRs) (1.9 ± 0.6 vs. 2.7 ± 0.9; EDVs/s) and exercise heart rates (HRs), (97 ± 17 vs. 106 ± 10), did not differ between the two groups (P > 0.05). In SURV, exercise PERs, which represented rapid left ventricular (LV) emptying, were significantly correlated with exercise PFRs, representing rapid LV filling, (r = 0.71, P < 0.04) but not in N-SURV (r = 0.66, P > 0.05). Among SURV, the Frank-Starling mechanism was thus preserved but not in N-SURV. Upon Cox analysis, overall LV function parameters, exercise PER was the only predictive measure associated with mortality (b = - 0.018, relative hazard ratio = 0.98, P = 0.02).

CONCLUSIONS

Exercise PER reduced values reflected failure of the Frank-Starling mechanism, the incapacity of the heart to perform rapid contractile adaptations to daily life activities and a poor prognosis.

Nuclear Cardiology: Present and Future

Nuclear cardiology has made significant advances since the first reports of planar scintigraphy for the evaluation of left ventricular perfusion and function. While the current "state of the art" of gated myocardial perfusion single-photon emission computed tomographic (SPECT) imaging offers invaluable diagnostic and prognostic information for the evaluation of patients with suspected or known coronary artery disease (CAD), advances in the cellular and molecular biology of the cardiovascular system have helped to usher in a new modality in nuclear cardiology, namely, molecular imaging. In this review, we will discuss the current state of the art in nuclear cardiology, which includes SPECT and positron emission tomographic evaluation of myocardial perfusion, evaluation of left ventricular function by gated myocardial perfusion SPECT and gated blood pool SPECT, and the evaluation of myocardial viability with PET and SPECT methods. In addition, we will discuss the future of nuclear cardiology and the role that molecular imaging will play in the early detection of CAD at the level of the vulnerable plaque, the evaluation of cardiac remodeling, and monitoring of important new therapies including gene therapy and stem cell therapy.