Variable-time positron emission tomography leg protocol to equalize noise for positron emission tomography/computed...

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Radiological Physics

Background:

• Conventional positron emission tomography (PET) protocols utilize constant scan times per bed position (BP).
• This approach may not be optimal for body sections with varying attenuation, such as the legs.
• Leg anatomy exhibits consistent tapering, suggesting potential for a variable-time imaging protocol.

Purpose of the Study:

• To develop and evaluate a variable-time PET scanning protocol for leg imaging.
• To reduce overall scan duration and redistribute acquisition time.
• To equalize image quality throughout the leg and minimize motion artifacts.

Main Methods:

• Analysis of leg dimensions from 55 adult PET/CT scans.
• Image quality was parameterized using bottle phantoms of varying diameters (4.5-19.7 cm) simulating leg structures.
• An exponential relationship between diameter and noise was established to define the noise-equalizing, variable-time protocol.

Main Results:

• Leg diameters in 94.5% of patients (52/55) were within ±7.5% of the mean diameter for similar height.
• Relative scan times were determined to equalize noise, decreasing from superior to inferior leg positions.
• The protocol defines specific relative scan times for sequential bed positions.

Conclusions:

• A variable-time PET protocol can reduce scan times by up to 75% for certain bed positions and halve total acquisition time.
• This optimized protocol has been successfully implemented.
• Variable-time scanning improves efficiency and image quality in PET leg imaging.