Performance of a brain PET camera based on anger-logic gadolinium oxyorthosilicate detectors.
A high-sensitivity, high-resolution brain PET scanner ("G-PET") has been developed. This scanner is similar in geometry to a previous brain scanner developed at the University of Pennsylvania, the HEAD Penn-PET, but the detector technology and electronics have been improved to achieve enhanced performance.


METHODS
This scanner has a detector ring diameter of 42.0 cm with a patient aperture of 30.0 cm and an axial field of view of 25.6 cm. It comprises a continuous light-guide that couples 18,560 (320 x 58 array) 4 x 4 x 10 mm(3) gadolinium oxyorthosilicate (GSO) crystals to 288 (36 x 8 array) 39-mm photomultiplier tubes in a hexagonal arrangement. The scanner operates only in 3-dimensional (3D) mode because there are no interplane septa. Performance measurements on the G-PET scanner were made following National Electrical Manufacturers Association NU 2-2001 procedures for most measurements, although NU 2-1994 procedures were used when these were considered more appropriate for a brain scanner (e.g., scatter fraction and counting-rate performance measurements).


RESULTS
The transverse and axial resolutions near the center are 4.0 and 5.0 mm, respectively. At a radial offset of 10 cm, these numbers deteriorate by approximately 0.5 mm. The absolute sensitivity of this scanner measured with a 70-cm long line source is 4.79 counts per second (cps)/kBq. The scatter fraction measured with a line source in a 20-cm-diameter x 19-cm-long cylinder is 39% (for a lower energy threshold of 410 keV). For the same cylinder, the peak noise equivalent counting rate is 60 kcps at an activity concentration of 7.4 kBq/mL (0.20 micro Ci/mL), whereas the peak true coincidence rate is 132 kcps at an activity concentration of 14 kBq/mL (0.38 micro Ci/mL). Images from the Hoffman brain phantom as well as (18)F-FDG patient scans illustrate the high quality of images acquired on the G-PET scanner.


CONCLUSIONS
The G-PET scanner attains the goal of high performance for brain imaging through the use of an Anger-logic GSO detector design with continuous optical coupling. This detector design leads to good energy resolution, which is needed in 3D imaging to minimize scatter and random coincidences.
Karp
Joel S
JS
Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA. karp@rad.upenn.edu
Surti
Suleman
S
Daube-Witherspoon
Margaret E
ME
Freifelder
Richard
R
Cardi
Christopher A
CA
Adam
Lars-Eric
LE
Bilger
Kilian
K
Muehllehner
Gerd
G
D001921:Brain / Q000000981:diagnostic imaging*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D019047:Phantoms, Imaging; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017640:Silicates; D014055:Tomography, Emission-Computed / Q000295:instrumentation*; D014159:Transducers
D017640:Silicates; C477725:gadolinium oxyorthosilicate