Impact of upgrading from a 25-cm to a 30-cm z-axis field of view digital PET/CT in a pediatric hospital

Increased positron emission tomography (PET) scanner z-axis coverage provides an opportunity in pediatrics to reduce dose, anesthesia, or repeat scans due to motion.

Recently, our digital PET scanner was upgraded from a 25-cm to a 30-cm z-axis coverage. We compare the two systems through National Electrical Manufacturing Association (NEMA) testing and evaluation of paired images from patients scanned on both systems.

NEMA testing and a retrospective review of pediatric patients who underwent clinically indicated 18F-fluorodeoxyglucose (FDG) PET computed tomography (PET/CT) on both systems with unchanged acquisition parameters were performed. Image quality was assessed with liver signal to noise ratio (SNR-liver) and contrast to noise ratio (CNR) in the thigh muscle and liver with results compared with an unpaired t-test. Three readers independently reviewed paired (25 cm and 30 cm) images from the same patient, blinded to scanner configuration.

Expansion to 30 cm increased system sensitivity to 29.8% (23.4 cps/kBq to 30.4 cps/kBq). Seventeen patients (6 male/11 female, median age 12.5 (IQR 8.3–15.0) years, median weight 53.7 (IQR 34.2–68.7) kg) were included. SNR-liver and CNR increased by 35.1% (IQR 19.0–48.4%) and 43.1% (IQR 6.2–50.2%) (P-value <0.001), respectively. All readers preferred images from the 30-cm configuration. A median of 1 (IQR 1–1) for fewer bed positions was required with the 30-cm configuration allowing a median of 91 (IQR 47–136) s for shorter scans.

Increasing z-axis coverage from 25 to 30 cm on a current-generation digital PET scanner significantly improved PET system performance and patient image quality, and reduced scan duration.