Evaluating FDG uptake changes between pre and post therapy respiratory gated PET scans

Area of Science:

• Nuclear Medicine
• Radiotherapy Oncology
• Medical Imaging Analysis

Background:

• Whole body (3D) and respiratory gated (4D) FDG-PET/CT scans are utilized in cancer staging and treatment monitoring.
• Evaluating changes in 18F-fluorodeoxyglucose (FDG) uptake post-radiotherapy (RT) is critical for assessing treatment efficacy.

Purpose of the Study:

• To investigate the impact of 4D FDG-PET/CT in evaluating therapy-induced FDG uptake changes compared to traditional 3D PET/CT.
• To assess differences in standardized uptake value (SUV) measurements between 3D and 4D PET/CT scans pre- and post-radiotherapy.

Main Methods:

• Acquired sequential 3D and 4D FDG-PET/CT scans pre- and post-RT for non-small cell lung cancer (NSCLC) patients.
• Analyzed lesions targeted with radiotherapy using regions of interest (ROIs) on both 3D and 4D scans across five respiratory phases.
• Compared pre- and post-RT FDG uptake using rigid registration and ROI analysis.

Main Results:

• Analyzed 16 lesions from 12 NSCLC patients.
• Significantly higher SUVmax values were observed on 4D PET compared to 3D PET (p < 0.005).
• Mean SUV decrease post-RT was 62% for 3D PET and 67% for 4D PET, with a non-significant mean absolute difference of 4.9% in SUV change (p=0.07).

Conclusions:

• 4D PET, with its signal recovery, yields higher SUVs than standard 3D PET.
• Observed differences in SUV change evaluation between 3D and 4D PET can significantly impact PET-based response assessment in NSCLC patients.
• Utilizing 4D PET may provide a more sensitive evaluation of treatment response.