Protocol for 18F-FDG quantification in PET-CT whole-body exams

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Radiological Physics

Background:

• Positron Emission Tomography (PET) with 18F-FDG is crucial for diagnosing various conditions.
• Accurate quantification of 18F-FDG uptake is essential for effective internal dosimetry.
• Standardized protocols are needed for reliable organ-level activity measurements.

Purpose of the Study:

• To propose a protocol for quantifying 18F-FDG activity at the organ level using whole-body PET scans.
• To establish a framework for internal dosimetry considering both normal uptake and pathological conditions.
• To compare internal radiation doses from 18F-FDG with external exposures from Computed Tomography (CT).

Main Methods:

• Selection of 97 adult patients with normal 18F-FDG uptake for a control group.
• Inclusion of patients with specific pathologies (intestine, colon, rectum, lung, lymphoma, melanoma, liver, esophagus, gonads, breasts).
• Estimation of absorbed doses from both CT scans and 18F-FDG uptake, considering organ kinetics and effective half-life.

Main Results:

• Quantification of 18F-FDG activity at the organ level was achieved through a proposed protocol.
• Internal dosimetry calculations were performed for various organs based on 18F-FDG kinetics.
• External exposure from CT was generally higher than internal 18F-FDG exposure, except for the bladder and kidneys.

Conclusions:

• The proposed protocol enables organ-level 18F-FDG activity quantification for improved dosimetry.
• Accurate individual dose estimation requires knowledge of parameters like effective half-life, achievable through protocol adaptation.
• The study highlights the importance of considering both internal and external radiation sources in patient safety during PET/CT procedures.