A comparison study on various low energy sources in interstitial prostate brachytherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Medicine

Background:

• Low-energy sources are standard in prostate brachytherapy.
• Iodine-125 (125I) is a widely used source.
• Cesium-131 (131Cs) is a newer low-energy brachytherapy source.

Purpose of the Study:

• To compare the dose distributions of 125I, 103Pd, and 131Cs sources in prostate brachytherapy.
• Evaluate the efficacy of different radioactive seeds for interstitial prostate brachytherapy.

Main Methods:

• Monte Carlo simulation (MCNPX) was used to model 125I, 103Pd, and 131Cs brachytherapy sources.
• Simulations used identical geometries for all sources, with specific gamma spectra for each.
• Dose rates and isodose curves were analyzed in a prostate phantom.

Main Results:

• Cesium-131 (131Cs) delivered a higher absolute dose to the tumor compared to 125I and 103Pd at the same air kerma strength and time.
• Palladium-103 (103Pd) showed a higher relative dose rate within the tumor and a lower relative dose rate outside the tumor.
• Dose profiles were analyzed along transverse and longitudinal axes, both inside and outside the simulated prostate tumor.

Conclusions:

• Cesium-131 (131Cs) offers an advantage due to its higher initial absolute dose rate (cGy/(h·U)).
• Palladium-103 (103Pd) is advantageous for its superior tumor targeting (higher relative dose inside, lower relative dose outside).
• Iodine-125 (125I) remains a strong option due to its longer half-life, potentially offering advantages in total delivered dose.