Spatial calibration of digital scintigraphic images: work in progress.

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Abstract
Accurate scintigraphic determination of organ dimensions is often difficult because of the wide variety of camera-collimator combinations and display formats used for imaging. An algorithm (SPACE-CAL) was developed for digital spatial calibration of up to 6 field .gamma. cameras or small-field .gamma. cameras using various collimators and magnification factors. The algorithm employs a master calibration file that can be used at multiple terminals. An interactive subroutine permits the operator to measure distances and areas directly from the images. Evaluation of 3 operators'' measurements of a pine-tree phantom acquired at various magnifications showed that distances could be measured with a high degree of accuracy. Calculation of ejection fraction from end-diastolic and end-systolic areas determined by SPACE-CAL showed a high correlation with automatic count determinations (r = 0.96) and angiographic calculations (r = 0.93) of ejection fraction in 12 patients. SPACE-CAL provides an easily implemented, reproducible and rapid method for accurate analysis of organ dimensions in digital images.