Ultra-high energy spectral prompt PET

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Preclinical Research

Background:

• Prompt gamma imaging in preclinical positron emission tomography (PET) offers advantages over traditional methods by mitigating image degradation from positron range blurring and photon downscatter.
• This technique enables multi-isotope PET imaging and improves counting statistics for low-abundance positron emitters, as previously demonstrated for isotopes like Iodine-124 (¹²⁴I) and Zirconium-89 (⁸⁹Zr).

Purpose of the Study:

• To evaluate the feasibility of achieving sub-millimeter PET imaging resolution using prompt gammas for a wide range of isotopes.
• To investigate the performance of prompt gamma imaging with isotopes emitting high-energy prompt gammas (>1 MeV) or complex gamma-ray spectra.

Main Methods:

• Utilized Monte Carlo simulations to assess image resolution and uniformity.
• Simulated a broad spectrum of prompt gamma energies (603 keV to 2.2 MeV) and various isotopes, including Manganese-52 (⁵²Mn), Technetium-94 (⁹⁴Tc), Zirconium-89 (⁸⁹Zr), Scandium-44 (⁴⁴Sc), Yttrium-86 (⁸⁶Y), Arsenic-72 (⁷²As), Iodine-124 (¹²⁴I), Potassium-38 (³⁸K), and Gallium-66 (⁶⁶Ga).
• Employed current cluster pinhole collimators in the simulations.

Main Results:

• Sub-millimeter resolution imaging was found to be feasible for most investigated isotopes using cluster pinhole collimators.
• Image resolutions of approximately 0.65 mm and 0.7 mm were achieved for lower energy prompt gammas (e.g., ¹²⁴I at 603 keV, ⁹⁴Tc at 703 keV, ⁵²Mn at 744 keV, ⁷²As at 834 keV, ⁸⁹Zr at 909 keV).
• Resolutions of approximately 0.75 mm and 0.8 mm were maintained at ultra-high energies (1.2 MeV for ⁴⁴Sc, 1.4 MeV for ⁵²Mn), with minor ring artifacts at 1.4 MeV. An image resolution of 1.2 mm was achieved for Potassium-38 (³⁸K) at 2.2 MeV.

Conclusions:

• Current cluster pinhole collimators are effective for sub-millimeter resolution prompt PET imaging up to at least 1.4 MeV prompt gamma energies.
• This capability expands the potential applications of various PET isotopes, paving the way for new tracer development and therapeutic strategies.