Performance characteristics of a newly developed PET/CT scanner using NEMA standards in 2D and 3D modes.
This study evaluates the 2-dimensional (2D) and 3-dimensional (3D) performance characteristics of a newly developed PET/CT scanner using the National Electrical Manufacturers Association (NEMA) NU 2-1994 (NU94) and NEMA NU 2-2001 (NU01) standards. The PET detector array consists of 10,080 individual bismuth germanate crystals arranged in 24 rings of 420 crystals each. The size of each crystal is 6.3 x 6.3 x 30 mm in the axial, transaxial, and radial dimensions, respectively. The PET detector ring diameter is 88.6 cm with axial and transaxial fields of view (FOVs) of 15.7 and 70 cm, respectively. The scanner has a uniform patient port of 70 cm throughout the PET and CT FOV, and the PET scanner is equipped with retractable septa to allow 2D and 3D imaging.


METHODS
Spatial resolution, scatter fraction, sensitivity, counting rate, image quality, and accuracy as defined by the NEMA protocols of NU94 and NU01 for 2D and 3D modes are evaluated. The 2D mode data were acquired with a maximum ring difference of 5, whereas the 3D mode acquisition used ring differences of 23. Both 2D and 3D mode data were acquired with an energy window of 375-650 keV. Random estimation from singles counting rate was applied to all relevant analysis. In addition, images from 2 clinical whole-body oncology studies acquired in 2D and 3D modes are shown to demonstrate the image quality obtained from this scanner.


RESULTS
The 2D NU94 transaxial resolution is 6.1-mm full width at half maximum (FWHM) 1 cm off center and increases to 6.9 mm tangential and 8.1 mm radial at a radius (R) of 20 cm. NU01 2D average transaxial (axial) FWHM resolution measured 6.1 (5.2) mm at R = 1 cm and 6.7 (6.1) mm at R = 10 cm. The NU94 scatter fraction for 2D (3D) was 13% (29%), whereas the NU01 scatter fraction gave 19% (45%). NU01 peak 2D (3D) noise equivalent counting rate (T(2)/[T + R + S]) was 90.2 (67.8) kilocount per second (kcps) at 52.5 (12) kBq/mL. Total 2D (3D) system sensitivity for true events is 8 (32.9) kcps/kBq/mL for NU94 and 1.95 (9.2) kcps/Bq for NU01.


CONCLUSIONS
The results show excellent system sensitivity with relatively uniform resolution throughout the FOV, making this scanner highly suitable for whole-body studies.
Mawlawi
Osama
O
Department of Imaging Physics, M.D. Anderson Cancer Center, Houston, Texas 77030, USA. Omawlawi@mdanderson.org
Podoloff
Donald A
DA
Kohlmyer
Steve
S
Williams
John J
JJ
Stearns
Charles W
CW
Culp
Randall F
RF
Macapinlac
Homer
H
D000328:Adult; D019544:Equipment Failure Analysis / Q000379:methods / Q000592:standards*; D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000592:standards; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000592:standards*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique / Q000295:instrumentation* / Q000592:standards*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000592:standards*; D014481:United States