Quantitation in PET using isotopes emitting prompt single gammas: application to yttrium-86

Area of Science:

• Nuclear medicine
• Radiopharmaceutical therapy
• Medical imaging

Background:

• Yttrium-90 somatostatin analogues are used in cancer radiotherapy.
• Accurate biodistribution assessment is needed to optimize dosing and minimize toxicity.
• Yttrium-90 is not suitable for quantitative imaging, while yttrium-86 imaging is affected by gamma-ray emissions.

Purpose of the Study:

• To develop and validate a patient-dependent correction method for quantitative yttrium-86 positron emission tomography (PET) imaging.
• To improve the accuracy of tissue uptake quantification for yttrium-86 labelled compounds used in radiotherapy planning.

Main Methods:

• A novel correction method using sinogram tail fitting with an yttrium-86 point spread function library was developed.
• The method was tested on abdominal phantom data and in patient studies.
• Quantitative accuracy was assessed by comparing PET-derived activity with known phantom activity and urinary excretion data.

Main Results:

• Phantom studies showed a reduction in background overestimation from 117% to 9% and kidney uptake error from 84% to 5%.
• Patient studies demonstrated a significant decrease in the discrepancy between total body activity and expected activity from urinary collections, from 92% to 7%.

Conclusions:

• The proposed patient-dependent correction method substantially improves the quantitative accuracy of yttrium-86 PET imaging.
• This advancement facilitates more precise biodistribution and pharmacokinetic assessments for yttrium-90 radiotherapy planning.
• Accurate imaging allows for safer and more effective personalized dosimetry in targeted radionuclide therapy.