Feasibility of ¹⁷⁷Lu activity quantification using a small portable CZT-based gamma-camera

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Radiopharmaceutical Therapy

Background:

• Activity quantification in image processing aims for geometry-independent metrics.
• Photon attenuation correction is crucial and can be achieved using spectral information.
• This study investigates ¹⁷⁷Lu activity quantification with a CZT-based hand-held gamma camera.

Purpose of the Study:

• To assess the feasibility of ¹⁷⁷Lu activity quantification using a small, hand-held gamma camera.
• To implement and evaluate an attenuation correction method based on spectral information.
• To compare performance with different collimator types (LEHR and MEGP).

Main Methods:

• Adapted a dual photopeak method for ¹⁷⁷Lu's three photopeaks (55, 113, 208 keV).
• Developed a measurement model incorporating source depth, activity, distance-dependent sensitivity, attenuation, and build-up.
• Estimated parameters and source depth/activity by minimizing model-measurement differences.
• Evaluated the method in phantom, clinical (superficial lesions), and pre-clinical (xenograft) settings.

Main Results:

• The MEGP collimator showed better performance with lower activity errors (2.9% ± 3.6% in phantoms) compared to LEHR (17% ± 9.6%).
• Patient measurements showed deviations of 0% ± 21% (LEHR) and 16% ± 18% (MEGP) compared to planar imaging.
• Pre-clinical mouse studies yielded average deviations of -16% (LEHR) and -6% (MEGP).

Conclusions:

• ¹⁷⁷Lu activity quantification is feasible with the hand-held gamma camera.
• The hand-held camera's accessibility facilitates frequent activity quantification, particularly for superficial structures and in pre-clinical research.
• The MEGP collimator is more suitable for accurate activity quantification with this system.