Gated single-photon emission computed tomography (SPECT) is a useful application to distinguish between an artifact due to soft tissue attenuation versus myocardial scar (infarction), and it also improves reader confidence.
Determination of left ventricular (LV) function by gated SPECT or radionuclide angiography (RNA) has valuable prognostic value, especially for prediction of death, and this is incremental to perfusion data alone.
Gated SPECT may frequently distinguish between ischemia cardiomyopathy and LV dysfunction due to a nonischemic etiology.
RNA has excellent reproducibility and permits assessment of both systolic and diastolic functions and is particularly useful in guiding chemotherapy administration.
Global dyssychrony may be assessed with gated SPECT and determination of histogram bandwidth and phase standard deviation. These factors may be useful in the prediction of response to resynchronization therapy or development of arrhythmias.
The assessment of ventricular function is a critical component of the evaluation of the cardiac patient with important diagnostic and prognostic applications. Radionuclide imaging offers highly accurate and precise methods for the measurement of left ventricular (LV) systolic and diastolic function, either in conjunction with myocardial perfusion imaging (single-photon emission computed tomography [SPECT] or positron emission tomography [PET]) or separately in the form of radionuclide ventriculography (RNV). More recently, the ability to assess dyssneregy has added another depth to the role of nuclear imaging in the accurate assessment of patients. This chapter will discuss the role of all three of these approaches.
GATED SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHY
The introduction of electrocardiographic (ECG)-gated myocardial SPECT in the 1990s expanded the application of myocardial perfusion imaging to routinely include the assessment of LV systolic function.1 The development and use of this technique occurred when technetium-based imaging agents were placed into clinical use, as these tracers provided much higher counts, and therefore image quality for measuring function. This was a critical development in the evolution of myocardial perfusion imaging. Currently, the majority of myocardial perfusion studies performed in the United States use gated SPECT technology and Tc-99m tracers. A more recent development has been the evaluation of ventricular dyssynchrony by SPECT, providing further data beyond myocardial perfusion. This chapter will discuss both aspects of ventricular assessment.
Gated SPECT images can be acquired using single- or multiple-detector cameras. More recently, dual-headed cameras in the 90-degree configuration have been preferred, as images can be acquired in half the time required using a single-headed system without sacrificing image quality. The majority of gated SPECT imaging is performed with high-resolution parallel hole collimators for Tc-99m studies, while all-purpose collimators are used for thallium-201 (Tl-201) studies. A 180-degree imaging arc (45-degree right anterior oblique [RAO] to 45-degree left posterior oblique projections) with a circular orbit is most commonly used, although noncircular (body contour, elliptical) orbits can also be used. The most ...