A new simpler image quality index based on body size for FDG-PET/CT

Area of Science:

• Nuclear Medicine
• Medical Imaging Physics

Background:

• Noise Equivalent Count (NEC) density is a standard metric for assessing whole-body fluorodeoxyglucose (FDG) positron emission tomography (PET) image quality.
• Calculating NEC density requires patient volume, which is often difficult to obtain consistently across different healthcare facilities.

Purpose of the Study:

• To develop and validate new, easily calculable image quality indices for whole-body FDG PET scans.
• To establish alternative metrics that do not rely on patient volume, improving accessibility for all facilities.

Main Methods:

• Ninety-four patients undergoing whole-body FDG PET scans were included in the study.
• Patient body weight and Body Mass Index (BMI) were correlated with patient volume.
• New indices, NEC normalized by body weight (NEC bw) and BMI (NEC bmi), were defined and calculated.
• Correlations between NEC bw, NEC bmi, and traditional NEC density were analyzed.
• The relationship between the new indices and visual image quality scores was also evaluated.

Main Results:

• Strong correlations were found between patient volume and both body weight (r=0.861) and BMI (r=0.728).
• NEC bw and NEC bmi demonstrated high correlations with NEC density (r=0.954 and r=0.897, respectively).
• Correlations between the new indices and visual scores were comparable to those with NEC density, particularly for patients with similar physiques.

Conclusions:

• NEC bw and NEC bmi are proposed as practical and reliable image quality indices for whole-body FDG PET.
• These new metrics overcome the limitations of NEC density by not requiring patient volume, thus enhancing usability across diverse clinical environments.
• The study validates NEC bw and NEC bmi as effective tools for evaluating image quality, comparable to existing methods.