C.A. Burnham

Development of a small animal PET imaging device with resolution approaching 1 mm

This paper describes progress in the design and construction of a single-plane PET tomograph having a spatial resolution approaching 1 mm. The system consists of a 12-cm diameter ring with 360 LSO (Lu/sub 2/SiO/sub 5/) detectors viewed by 30 photomultiplier tubes. Thin (5-mm) crystals and a low energy threshold are used. Crystals are identified using both position arithmetic and energy criteria. To date, the system construction has been completed, system tuning has been carried out and imaging studies have begun.

A Multi-Crystal Positron Camera

A multicrystal positron camera designed for use with radionuclides produced with a medical cyclotron is described. The camera uses coincidence techniques for collimation by detecting the positron annihilation radiation. Typical radionuclides are 11C, 13N, 15O with half lives of 20, 10, and 2 minutes, respectively. The principal object of the design is to achieve a data rate capacity to 5 × 104 coincidence events per second, as well as high sensitivity and resolution. This will allow time sequential images of fractional second duration. Each of the cameras two identical detectors consist of a planar array of 127 small NaI(Tl) crystals viewed by an array of 72 phototubes. Timing signals are derived from the phototubes and are subsequently used to identify 2549 crystal pairs. The coincidence data is stored in a magnetic-core memory and used for a local data display; alternatively data may be transferred under program control to a PDP-9 computer. The sensitive field area is 27 cm × 30 cm and the spatial resolution is less than 1 cm at the midplane. The camera is currently being used for a number of clinical applications.

Cylindrical PET detector design

A cylindrically shaped high-resolution PET (positron-emission-tomography) detector that uses cross-plane coincidence events is being developed. A 2-D analog coded position-sensitive detector is used. It consists of a hexagonal array of photomultiplier tubes and a rectangular array of crystals, eight elements per tube. The optics has been designed to maximize the light collection and to provide uniform spatial resolution. The detector will be 60 cm in diameter by 11.5 cm wide, the crystals are 3 mm*5.7 mm*30 mm. The design, associated electronics, and results of measurements on a sector of the detector are presented. >

A Stationary Positron Emission Ring Tomograph Using Bgo Detector and Analog Readout

A single ring PET camera has been constructed to demonstrate the use of one dimensional scintillation camera techniques in positron tomographic design. A pseudo-continuous BGO detector is used. The detector is 46 cm ID, 52 cm OD, 2 cm wide and is made using 360 elements. A narrow light guide and 90 PM Tubes are used for the readout. The position of coincident events are found using unique scintillation camera logic.

Performance evaluation of MMP-II:A second-generation small animal PET

We have completed construction of a second-generation, single-plane small animal PET instrument based on LSO detectors. The second-generation design addresses some of the limitations in the first-generation. The purpose of the work reported here was to characterize the physical performance of this instrument. Results of the performance measurements include: Spatial resolution=1.25 mm at field center and 1.5 mm at 2 cm radius; point source sensitivity=56 cps/uCi,; scatter fractions of 0.019 and 0.056 in 3.8 and 6 cm diameter cylinders respectively; linearity of reconstructed signal within 5% up to 100 uCi/cc and acceptable dead-time performance up to 25 k true cps. Examples of phantom and animal images are also presented.

A Positron Tomograph Employing a One Dimension BGO Scintillation Camera

A detector employing a pseudo-continuous ring of BGO and analog type position sensing has been constructed. It is fabricated using 360 2 × 3 × 0.4cm BGO detector elements, a light guide 1 × 1.6 × 51cm ID and 90 2cm diameter PM tubes. The position of a scintillation event is identified using logic based on a maximum likelihood estimator. A stationary high spatial resolution high detection efficiency tomograph is achieved using this approach.

One Dimensional Scintillation Cameras for Positron Ect Ring Detectors

A one-dimensional scintillation camera configured as a continuous ring with coincidence-mode collimation avoids many of the problems associated with rings formed from an array of discrete detector elements. With the goal of achieving a stationary detector exhibiting high spatial resolution and sensitivity, several detector configurations have been designed. Both analytic and Monte-Carlo simulation techniques have been used to evaluate these designs. Results of the calculations and comparative measurements on the various detector designs are discussed.

Design of a Cylindrical Shaped Scintillation Camera for Positron Tomographs

The design of a cylindrically shaped scintillation camera for volume imaging of positron emitters is discussed. The design is based on the detector concepts developed for a single ring scintillation camera, i.e., the Massachusetts General Hospital analog ring camera. Detector characteristics derived from both computer modeling and measurements are presented.

Application of Monte-Carlo Methods to the Design of Spect Detector Systems

Monte-Carlo methods have been applied to the design of a detector suitable for use in a SPECT cylindrically shaped scintillation camera. Included in the study are the calculated detection characteristics of two scintillator materials and the optical performance of several geometric configurations. Results include maps of the light distribution for several rectangular crystal-light guide combinations, a comparison of various approaches to specifying the optical properties of detector surfaces, and estimates of relative light output for various geometries.

Application of a One Dimensional Scintillation Camera in a Positron Tomographic Ring Detector

The optical and position sensing properties of the array are unique. All the light from a scintillation is projected from the narrow elements through a light guide and into a ring of PM tubes yielding a narrow light spread function that is independent of the depth of an interaction. Position sensing logic based on a maximum likelihood estimator has been employed to ensure high spatial resolution. The spatial sampling has been chosen so not to impose the primary resolution limit.