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.

Databases as Topic↗

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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.

Adult↗

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SPECT: current and future developments.

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Heart↗

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Removal of atmospheric particulates by urban vegetation: implications for human and vegetative health.

A review of the literature reveals considerable evidence to support the suggestion that vegetative surfaces remove particulate matter from the atmosphere. Preliminary observations of the leaf surfaces of an important urban tree indicate the presence of numerous particulate contaminants. In view of the medical importance of fine particles in urban atmospheres, it is important to assess the efficiency of tree surfaces in particle retention. Can particulate loads be reduced below biologically significant thresholds by vegetation? Are trees acutely injured or subtly influenced in the process of this removal? A brief assessment of research needs is provided.

Air Pollutants↗

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Determination of aspirin and salicylic acid by reverse-phase liquid chromatography.

Buffered solid dosage forms containing aspirin, magnesium hydroxide, and aluminum hydroxide are blended with acidic ethanol to extract the aspirin and salicylic acid rapidly. The resulting preparation is then immediately injected onto a 4.6 mm x 3 cm 5 micron reverse-phase column. Aspirin and free salicylic acid are determined simultaneously. The run time is less than 2 min. The total time from the initiation of sample extraction to completion of the separation is less than 5 min.

Aspirin↗