Quantification of FDG in the spinal cord using PET/MRI

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Radiophysics

Background:

• Investigating MR-derived attenuation maps and detector resolution effects on PET/MRI spinal cord uptake.
• Simulating [18F]FDG PET data to assess quantification accuracy.
• Evaluating attenuation correction methods, including bone removal and detector resolution impacts.

Purpose of the Study:

• To quantify the impact of MR-derived attenuation maps and limited detector resolution on PET spinal cord activity uptake.
• To assess the effectiveness of point spread function (PSF) and time-of-flight (TOF) corrections in mitigating quantification errors.
• To compare different attenuation correction strategies in PET/MRI.

Main Methods:

• Simulated [18F]FDG PET data in the neck and thorax at 2.1 mm and 4.4 mm detector resolutions.
• Modified attenuation maps to exclude bone features and compared with full attenuation correction.
• Analyzed clinical patient data using PSF and TOF corrections on a SIGNA PET/MR scanner.
• Measured mean uptake in regions of interest along the spinal cord.

Main Results:

• Excluding bone from attenuation correction decreased mean uptake by 3%-10.4%.
• Lower detector resolution (4.4 mm) resulted in a 32.2% uptake decrease compared to 2.1 mm.
• TOF correction reduced uptake differences to 4.3%-7%, with TOF Q.Clear (beta=100) showing the smallest difference (0.6%-5.2%).
• PSF modeling did not yield statistically significant changes.

Conclusions:

• Ignoring bone in PET/MRI spinal cord imaging leads to reduced activity quantification.
• Partial volume effects significantly impact uptake reduction in lower-resolution data.
• TOF correction partially addresses quantification errors, but further research into partial volume correction is necessary.