Eugene Gualtieri

ABSTRACT We present a new approach to decision making based on the concept of emission counts (EC), i.e., the number of events emitted per voxel during the scan. The approach allows direct computation of posterior probabilities of hypotheses defined in terms of EC, and is applicable to any type of emission tomographic list-mode projection data, e.g., SPECT, PET, or time-of-flight (TOF)-PET, as well as binned data which can be considered a special case of list-mode data. Conditional Bayesian (CB) decision theory utilizing values of the posterior probability of hypotheses as test statistics are used to derive decision rules. We demonstrate that the derived decision principle is equivalent to the likelihood-ratio ideal observer for binary hypothesis testing. We use data acquired in list-mode format for an anthropomorphic torso phantom using a lanthanum-bromide time-of-flight PET scanner to provide examples of application of EC-CB observer. For data-specific decisions, we demonstrate examples of multiple-hypotheses decision making. For imaging system evaluation, we define two regions of interest (ROls) on the image, and two hypotheses, H1 and H2, that one ROI emitted on average at least r times more events than the other region. The posterior probabilities of H1 and H2 are determined. ROC curves are constructed using 50 projection data sets (list-mode tiles), each including 16 million prompts, from which 25 data sets correspond to H1 and the other 25 to H2. The areas and partial areas under the ROC curves are used as figures of merit evaluating the performance of the LaBr3 PET system in discriminating between H1 and H2 with and without TOF information. Summary: A new optimal numerical observer which makes decisions based on posterior probability of emission counts is presented. The utility of the observer for hypothesis testing is demonstrated on TOF list-mode phantom data acquire- on PENN LaPET scanner.

ABSTRACT A new PET system has been developed for the purposes of simultaneous PET/MR whole body rodent imaging in conjunction with a Varian large-bore 9.4T MRI system with a commercial Insight birdcage coil. The detector and readout technology is based on that developed for the RatCAP PET system, resulting in a highly robust and compact design that is compatible with MRI systems at the highest field strength. Testing of the full readout chain has shown a successful implementation of both modalities, with indications of only modest cross-interference on MRI image quality or PET detection efficiency. The final design cycle is complete, and supports operation of the full system with upgrades to the data acquisition electronics, firmware, and software. First results from the complete PET system will be presented, including preliminary imaging and tests of interference between modalities.

The feasibility of performing high-resolution PET and high-field MRI simultaneously in rodents has been previously demonstrated in small-scale systems capable of imaging the rat brain and mouse. We are nearing completion of a larger scale PET system which will accommodate the whole rat and perform at 9.4 T with <2 mm PET resolution. The PET insert has inner/outer diameters of

ABSTRACT We describe the prototype of a full-body PET scanner for rats that is compatible with a 9.4 T MRI system. The detector consists of 96 PET detector blocks in a cylindrical arrangement. In this paper we concentrate on a new readout technology, which takes advantage of the fact that optical fibers are insensitive to electromagnetic interference. The data are formatted in a FPGA on the motherboard and sent to a data acquisition computer through standard Gigabit Ethernet connections. We will describe the technology chosen for the system, and introduce the data acquisition adapted for the readout of the data.