Computed tomography automatic exposure control techniques in 18F-FDG oncology PET-CT scanning

Area of Science:

• Medical Imaging
• Radiology
• Nuclear Medicine

Background:

• Computed tomography (CT) automatic exposure control (AEC) systems are integral to modern PET-CT scanners.
• Comparing AEC techniques across manufacturers is essential for consistent imaging.
• Fluorine-18 fluorodeoxyglucose (FDG) PET-CT is a key tool in oncology imaging.

Purpose of the Study:

• To compare the automatic exposure control (AEC) techniques of three major PET-CT manufacturers.
• To evaluate AEC performance for fluorine-18 fluorodeoxyglucose (FDG) half-body oncology imaging.
• To assess the impact of AEC on radiation dose and image quality across varying patient weights.

Main Methods:

• A retrospective audit of 70 patients undergoing half-body CT scans on GE, Philips, and Siemens PET-CT systems.
• Recording of patient demographics and radiation dose information.
• Calculation of image noise using the standard deviation of Hounsfield units in the liver.
• Phantom studies using a Rando phantom to directly compare AEC systems across various settings.

Main Results:

• Significant differences in dose and image quality variation with patient weight were observed among the three manufacturers.
• The GE system exhibited the largest dose variation with weight, while Philips showed the least.
• Image noise varied with patient weight in Philips and Siemens systems but remained constant in the GE system.
• Tube current modulation techniques and AEC settings directly influenced these observed differences.

Conclusions:

• CT AEC systems from GE, Philips, and Siemens demonstrate distinct tube current modulation patterns.
• These differences result in varied radiation doses and image quality levels depending on patient weight.
• Awareness of system-specific AEC behavior is vital for optimizing PET-CT imaging protocols in oncology.