To improve the quality of digital nuclear medicine images, we have developed a new implementation of the Wiener restoration filter. The Wiener filter uses as its optimality criterion the minimization of the mean-square error between the undistorted image of the object and the filtered image. In order to form this filter, the object and noise power spectrums are needed. The noise power spectrum for the count-dependent Poisson noise of nuclear medicine images is shown to have a constant average magnitude equal to the total count in the image. The object power spectrum is taken to be the image power spectrum minus the total count, except in the noise dominated region of the image power spectrum where a least-squares-fitted exponential is used. Processing time is kept to a clinically acceptable time frame through use of an array processor. Pronounced noise suppression and detail enhancement are noted with use of this filter with clinical images.

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The effect of maximum exercise on left ventricular function was assessed in 12 patients with normally innervated hearts (IH) and six patients with denervated hearts (DH) who had undergone cardiac transplantation. Left ventricular function was assessed by computer-assisted analysis of the motion of surgically implanted midwall myocardial tantalum markers, visualized fluoroscopically. Measurements were made at rest, and peak supine exercise in both groups of patients. The effect of atrial pacing to the heart rate achieved with peak exercise was also assessed in the patients with denervated hearts. The mean ejection fraction was increased at peak exercise in both groups of patients, although to a greater extent in patients with DH (14% vs 5%). With atrial pacing the mean ejection fraction decreased from the resting value by 4% in DH. The velocity of circumferential fiber shortening increased with peak exercise by 43% in IH and 38% in DH, but did not increase with atrial pacing in the DH group. Stroke volume index increased with peak exercise by 3% in IH and 14% in DH, but decreased by 6% with atrial pacing. There was no significant difference between end-diastolic volumes at rest, exercise or atrial pacing. Although these data may be important with milder exercise, they suggest that the preload effect was not predominant at peak exercise. By exclusion, adrenergic drive was the most important inotropic factor in the left ventricular response to peak exercise. The comparison between denervated and innervated patients' response to strenuous exercise suggests that comparably good exercise performance can be obtained by the denervated heart in the absence of normal autonomic control. Circulating catecholamines may therefore be contributing a very important inotropic action at peak exercise.THE CIRCULATORY AND HEMODYNAMIC effects of muscular exercise have been extensively studied,'-2 but direct measurement of left ventricular

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