Imaging joint infections using D-methyl-¹¹C-methionine PET/MRI: initial experience in humans

Area of Science:

• Nuclear medicine
• Radiochemistry
• Infectious disease imaging

Background:

• Current non-invasive imaging struggles to differentiate infection from tumors or sterile inflammation.
• Prosthetic joint infections are a significant complication of joint replacement surgery.
• There is a need for specific imaging agents to detect bacterial infections accurately.

Purpose of the Study:

• To evaluate the biodistribution, radiation dosimetry, and initial human safety and efficacy of D-methyl-11C-methionine (D-11C-Met) for suspected prosthetic joint infections.
• To assess the potential of D-11C-Met as a bacteria-specific PET radiotracer.

Main Methods:

• D-11C-Met was synthesized and administered to healthy volunteers and patients with suspected prosthetic joint infections.
• Positron emission tomography/magnetic resonance imaging (PET/MRI) was used to study tracer uptake.
• Radiation dosimetry was calculated using OLINDA/EXM software.
• Standardized uptake values (SUVmax, SUVpeak) and kinetic modeling were used to quantify tracer uptake in infected vs. uninfected joints.

Main Results:

• D-11C-Met was well tolerated, exhibiting rapid urinary clearance and low effective doses.
• Minimal background uptake was observed in healthy tissues and organs.
• Significantly higher focal uptake of D-11C-Met was observed in suspected prosthetic joint infections compared to contralateral joints and background (P < 0.01).

Conclusions:

• D-11C-Met demonstrates a favorable radiation profile, minimal background uptake, and rapid urinary excretion.
• The tracer shows promising increased uptake in suspected infection sites, indicating its potential for diagnosing prosthetic joint infections.
• Larger clinical trials are needed to validate these findings against a gold standard.