Human dose estimation of a novel SPECT imaging agent using animal experimental data and Monte Carlo simulation

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Chemistry
• Medical Imaging

Background:

• Precise dose determination is crucial for diagnostic and therapeutic procedures.
• Gastrin-releasing peptide receptor (GRPR) is a target for diagnosing GRPR-positive tumors, especially prostate cancer.

Purpose of the Study:

• To estimate the human absorbed dose of the novel GRPR-targeting SPECT imaging agent [^113mIn]In-RM2.
• To evaluate its potential clinical application for diagnosing GRPR-positive tumors.

Main Methods:

• Preparation of [^113mIn]In-RM2 using a ¹¹³Sn/^113mIn generator.
• Assessment of radiochemical purity (>98%) and stability (>3 hours).
• Biodistribution studies in mice, dose extrapolation to humans using mass-scaling, and Monte Carlo simulation (MCNPX) for absorbed dose calculation.

Main Results:

• [^113mIn]In-RM2 demonstrated high radiochemical purity and stability.
• The radiotracer exhibited rapid blood clearance and urinary excretion in mice.
• The pancreas and kidneys received the highest absorbed doses (0.008 ± 0.0007 and 0.0036 ± 0.0003 mGy/MBq, respectively), with negligible doses to other organs.

Conclusions:

• [^113mIn]In-RM2 is a safe and promising SPECT imaging agent for GRPR-positive tumors.
• It shows lower absorbed doses compared to similar radiopharmaceuticals.
• The findings support its potential clinical application in diagnosing prostate cancer.