Internal dosimetry for radioembolization therapy with Yttrium-90 microspheres

Area of Science:

• Medical Physics
• Nuclear Medicine
• Radiotherapy

Background:

• Accurate dosimetry is crucial for Yttrium-90 radioembolization therapy of liver lesions.
• Current dosimetry methods for liver and adjacent organs are not well-established.
• Yttrium-90 (90Y) radioembolization is an emerging treatment for metastatic liver disease.

Purpose of the Study:

• To establish a clinically practical method for determining Yttrium-90 dosimetry in liver radioembolization.
• To calculate absorbed doses in the liver and adjacent organs (lungs, kidneys, bone marrow).
• To evaluate the safety and efficacy of higher Yttrium-90 activities.

Main Methods:

• Utilized Monte Carlo GATE code simulations with various female and male XCAT body mass index models.
• Simulated uniform deposition of 100 MBq of 90Y in the liver.
• Calculated self-irradiation and absorbed doses using the mean energy of 90Y (0.937 MeV).

Main Results:

• Liver absorbed doses ranged from 53 to 84 Gy, falling below the target range of 80-150 Gy.
• Absorbed doses in bone marrow, lungs, and kidneys were significantly low (<0.1 Gy, <0.4 Gy, and <0.5 Gy, respectively).
• Estimated S-values and equivalent doses in target and organs at risk.

Conclusions:

• The study suggests that higher Yttrium-90 activities than the conventional 3 GBq may be required for effective liver radioembolization.
• Calculated absorbed doses in non-target organs indicate a favorable safety profile for increased activity.
• Further clinical validation is necessary to confirm these dosimetry findings and treatment recommendations.