An in vivo evaluation of labeled lesions within a body lumen (30) using a catheter (30) having an array of radiation detectors (28). Catheters and methods which detect radiotracers which have bound to vulnerable plaque as in Figure (1). The radiation detectors can be coupled to a signal processor through a delay line (42) so as to reduce the number of transmission lines traveling through the catheter to outside the body. The radiation detectors (28) can be semiconductor detectors or optical detectors.
