Value of gating of technetium-99m sestamibi single-photon emission computed tomographic imaging.

OBJECTIVES: The purpose of this study was to determine how frequently and for what reasons the addition of electrocardiographically gated technetium-99m (Tc-99m) sestamibi single-photon emission computed tomographic (SPECT) images add value to nongated SPECT perfusion images. BACKGROUND: Electrocardiographic gating of Tc-99m sestamibi SPECT images permits assessment of regional and global left ventricular function and may assist in differentiating attenuation artifacts from myocardial scar. METHODS: A total of 285 consecutive patients (143 women and 142 men; mean age 57.6 +/- 11.5 years) underwent gated SPECT Tc-99m sestamibi imaging (212 with exercise, 63 with dipyridamole and 10 with dobutamine). The conventional stress and rest tomograms were interpreted first by means of a 14-segment scoring system, and then the studies were reinterpreted while the gated images were viewed. RESULTS: In the total group of 285 patients, the number of "borderline" interpretations was reduced from 89 to 29. In the 137 patients with a < or = 10% pretest likelihood of coronary artery disease, the addition of gated images added significantly to the percentage of interpretations that were designated "normal" (74% [101 of 137] vs. 93% [127 of 137], p < 0.0001), due to a reduction in borderline normal and borderline abnormal readings. In 49 patients with a previous infarction or recent angiography with > or = 70% stenosis, or both, the addition of gated images changed the percentage of "abnormal" scan interpretations from 78% (38 of 49) to 92% (45 of 49). This result was not significant (p = 0.09, two-tailed), but the trend was toward a greater number of unequivocal abnormal interpretations in this subgroup. CONCLUSIONS: The addition of electrocardiographically gated Tc-99m sestamibi SPECT images to the reading of stress and rest perfusion images alone resulted in shifting the final scan interpretations to a more normal designation in patients with a low pretest likelihood of coronary artery disease, and to more abnormal defects consistent with coronary artery disease in patients with known coronary artery disease. The number of "borderline normal" and "borderline abnormal" interpretations are significantly reduced when gated SPECT images are interpreted simultaneously with stress and rest perfusion images.

Quantitative gated single photon emission computed tomography imaging: a counts-based method for display and measurement of regional and global ventricular systolic function.

BACKGROUND: Gated single photon emission computed tomography imaging allows simultaneous determination of myocardial perfusion and function. Quantitative perfusion measurements can be based on regional tracer uptake, but function measurements ordinarily require endocardial and epicardial edge detection, which is problematic because of the inherently low spatial resolution and image noise in single photon emission computed tomography images. This article presents methods for quantification of both function and perfusion that do not require edge detection. METHODS AND RESULTS: In SPECT imaging the partial volume effect causes changes in myocardial wall thickness to be reflected as changes in pixel counts in pixels representing the myocardial wall. This effect allows an estimation of changes in myocardial wall thickness by comparing pixel counts in end-systolic images with corresponding pixel counts in end-diastolic images. This article first describes a standard method to quantify myocardial perfusion by sampling myocardial tracer activity at rest and stress. The same method is then used to sample tracer activity in diastolic and systolic images. A new method is developed to convert the diastolic and systolic samples into quantitative estimates of regional wall thickening. A method is then developed to convert the regional wall thickening fractions into a global left ventricular ejection fraction. A normal database is presented. Receiver operating characteristic analysis is used to establish normal limits. CONCLUSION: This method requires no edge detection or geometric boundary estimates. Computer results are presented in a simple and intuitive format, which is uniform for parameters of both perfusion and function. The method is robust and produces relatively few false-positive results.

Validation of a new counts-based gated single photon emission computed tomography method for quantifying left ventricular systolic function: comparison with equilibrium radionuclide angiography.

BACKGROUND: Because myocardial wall thickness is smaller than the spatial resolution of single photon emission computed tomography (SPECT) imaging, changes in myocardial wall thickness are related to changes in maximum pixel counts via the partial volume effect, allowing for quantification of regional systolic wall thickening. We have developed a new gated SPECT method for computing the global left ventricular ejection fraction (LVEF) based entirely on changes in maximum regional myocardial counts during systolic contraction. This new method is independent of endocardial edge detection or other geometric measurements. METHODS AND RESULTS: In 23 patients the gated SPECT method was validated by comparison with radionuclide angiography. The correlation between computed LVEFs was excellent (slope = 0.97, r = 0.91). The measurement of LVEF by gated SPECT was highly reproducible, with minimal intraoperator (slope = 0.97, r = 0.97) or interoperator (slope = 1.00, r = 0.97) variability. Measurements of regional thickening indexes were also reproducible, with a mean intraoperator correlation coefficient of 0.89 +/- 0.05 (range 0.79 to 0.95) for the 14 myocardial regions. Finally, the measurement of LVEF was not significantly influenced by changes in reconstruction filter parameters over a range of cutoff frequencies from 0.16 to 0.28. CONCLUSIONS: This new counts-based gated SPECT method for measuring global left ventricular systolic function correlates well with radionuclide angiography, is highly reproducible, and has theoretic advantages over geometric methods.