SUMMARY To determine the relationship of phase changes and abnormalities of ventricular contraction and conduction, we performed phase image analysis of blood pool scintigrams in 29 patients. Eleven patients had no evidence of blood pool contraction or ECG conduction abnormalities, four had contraction abnormalities, seven had abnormal conduction and seven had abnormalities of both variables.The phase delay generally related to the degree of contraction abnormality. The mean phase delay in hypokinetic segments differed from that in normokinetic segments in the same patient (p < 0.025), the phase delay of akinetic and dyskinetic segments differed from that in normokinetic segments (p < 0.001) and the phase delay in dyskinetic segments differed from that in akinetic segments (p < 0.005), but there was a significant overlap in the phase delay in normal and hypokinetic segments. Also, in patients with conduction abnormalities, the minimal associated regional phase delay presented a phase dispersion and a pattern of contraction consistent with the pattern of conduction and different from normal.A single study performed both at rest and with stress demonstrated the effect of heart rate on phase assessment and confirmed the independent effects of contraction and conduction on phase delay. Acquisition and analytic methods should add significantly to the resolution of the phase method.EQUILIBRIUM multiple-gated blood pool scintigraphy is an accurate noninvasive method for determining ventricular size and function.1' 2 Analytic methods that use digital computer manipulation have been applied to the blood pool study to extract additional data.8' 4 Such manipulation produces functional images as the ejection fraction image, which color-codes the end-diastolic frame of the blood pool scintigram in terms of regional ejection fraction, while the stroke volume image color-codes the end-diastolic frame in terms of regional stroke volume. Recently, the phase image has been developed. MethodsPhase image analysis was performed on two series of consecutive patients, in whom blood pool scintigraphy was required clinically for the noninvasive assessment of ventricular size and function. One group included patients with a normal ejection fraction and segmental wall motion and without electrocardiographic conduction delay. A second consecutive series of patients had reduced left ventricular ejection fraction and obvious contraction abnormalities on qualitative visual blood pool assessment or significant electrocardiographic intraventricular conduction delay with QRS > 0.12 second. All patients were in normal sinus rhythm.The history of each patient was reviewed for infarction, and a 12-lead ECG was obtained on the day of scintigraphy. Electrocardiographic abnormalities were noted. Evidence of infarction was confirmed historically and supported by the presence of ECG Q waves . 0.04 second in duration. Conduction abnormalities, including evidence of left bundle branch block and right bundle branch block,7 were documented and pacemaker ar...

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To localize bypass pathways, left and right ventricular regions were analyzed at rest by phase image analysis in 18 patients with ventricular pre-excitation syndromes. These were compared with image findings in 18 normal subjects. In each of 17 patients with pre-excitation, the site localized on electrophysiologic study correlated closely with the region of earliest ventricular phase angle. This site could be objectively separated from that in normal subjects in each of eight patients with an active left-sided pathway and in both patients with a right-sided pathway. Those with a septal pathway revealed earliest septal phase angle, but could not be separated from normal subjects. In the eight patients with an active left bypass tract, the onset, upstroke and peak of the left ventricular phase histogram preceded those of the right ventricular histogram. Those with a left-sided pathway demonstrated a mean left ventricular phase angle, a difference between mean left and mean right ventricular phase angle and a difference between earliest left and right ventricular phase angles which was significantly less than that in normal subjects (p less than 0.05). These variables presented characteristic converse changes in those with a right-sided pathway. Sequential phase changes in 10 studies suggested "fusion" of normal septal with lateral bypass fronts. Electrocardiographic and electrophysiologic localization of the bypass pathway agreed in only 8 of 14 patients with a recognized delta wave. The phase image represents a new, noninvasive method of evaluating ventricular pre-excitation. The method may provide useful information complementary to that of electrocardiographic and electrophysiologic analysis.

The Rose model of signal-to-noise ratios in images has been applied to diagnostic imaging instrumentation, extending it by taking into account effects due to finite spatial resolution, background effects and texture. The model leads to an understanding of the impact of the physics of the total system (object and instrument) on output contrast and signal-to-noise ratios. Principally, it leads to an understanding of the fact that nuclear images are not (by and large) statistics limited. The model can also be used to compare different imaging techniques. To the extent that the signal-to-noise ratio is a necessary but not sufficient estimator of the detectability of a lesion, the model does not provide a complete description of the imaging characteristics of an instrument.