Coupling of results of cerebral blood flow and static brain studies.

A positivestatic,if dynamicis positive 0.448 0.480 The relationship between cerebral dynamic studies and static brain imaging was evaluated in 200 consecutive patient examinations. The results indicated that the two studies are not independent but are coupled. Cerebral dynamic studies have become a recog nized and helpful first step in the brain scanning pro cedure. Recent description of computer programs for processing the data (I ,2) may contribute even further to the value of the dynamic phase of the study. However, there have been only a few state ments of the interrelationship of the number of posi tive dynamic studies and those found on the static brain images. We present here a simple but useful analysis which may set the stage for more sophisti cated approaches. In late I 972 we studied the results of 200 consecu tive cerebral dynamic studies and companion static brain scans. The recent publication of 1, I 65 cases of dynamic and static studies by Cowan and cowork ers (3) has allowed a comparison of the two series (especially since the methodologies were nearly iden tical). Technetium-99m-pertechnetate (200 pCi/kg body weight) was injected as a bolus into an arm vein, and eight Polaroid pictures were obtained by hand pulling. A Nuclear-Chicago Pho/Gamma III or Picker Dynacamera were used with parallel-hole collimators. Static images were obtained after a wait of at least 1 hr. Results of the numerical analysis are shown in Table I. Of particular interest are the last three lines of the table. If the results of the dynamic study do not influence the results of the static brain scan (in dependent variables) , then the likelihood of having both a positive dynamic study and a positive static study is obtained by multiplying the two probabili ties together. In both our series and that of Cowan, et al (3), the number of patients having both studies positive was greater (2.2†" 3.2 times greater) than expected on the basis of independent variables. The two studies are thus not independent but are coupled. The last two lines in Table I indicate the extent of the coupling of the results of the positive dynamic and static studies. Indeed, the values emerging from our series are nearly identical to those derived from the figures given by Cowan and coworkers (3). If a static study was positive, there was a 27% proba bility that the dynamic study was also …