32P liquid sources—comparison of the effectiveness of postangioplasty versus poststenting intravascular brachytherapy in hypercholesterolemic rabbits

Monte Carlo dosimetric parameter study of a new (32)P brachytherapy source

OBJECTIVE

Recently, a new catheter-based (32)P brachytherapy source has been developed (College of Chemistry, Sichuan University) for use in high-dose-rate afterloader. This study presents the results of the dosimetric data of the Geant4 Monte Carlo (MC) simulation toolkit for this new (32)P brachytherapy source.

METHODS

The new (32)P source had dimensions of 0.50-cm length and 0.08-cm diameter and was encapsulated in teflon. In this study, we attempted to obtain dosimetric data for this new source, as required by the formalism proposed by the American Association of Physicists in Medicine reports TG60 and TG149. The source was located in a 30-cm radius theoretical sphere water phantom, and the absorbed dose of the source was calculated using MC code.

RESULTS

The dosimetric data included the reference absorbed dose rate, the radial dose function in the range of 0.10-0.50 cm at a longitudinal axis, the polynomial function for the radial dose function and the anisotropy function with a θ value of 0-90° in 5° intervals and an r of 0.10-0.35 cm in 0.01-cm intervals. The radial and axial dose profiles and away-along quality assurance table are also calculated for the unsheathed (32)P source. The dose rate D(r0,θ0) at the reference point for the unsheathed (32)P source is determined to be equal to 1.2660 ± 0.0006 cGy s(-1) mCi. The radial dose function of the new (32)P source shows good agreement with the other (32)P source presented in this work with an average difference of 1.78%.

CONCLUSION

Dosimetric data are provided for the new (32)P source. These data could be used in treatment-planning systems in clinical practice.

ADVANCES IN KNOWLEDGE

Provided a new beta-emitting brachytherapy source that is intended for treatment of liver cancer. A dosimetric study of the unsheathed (32)P source for which no published dosimetric data existed was performed.

Monte Carlo dosimetry of a new (90)Y brachytherapy source

Purpose

In this study, we attempted to obtain full dosimetric data for a new ⁹⁰Y brachytherapy source developed by the College of Chemistry (Sichuan University) for use in high-dose-rate after-loading systems.

Material and methods

The dosimetric data for this new source were used as required by the dose calculation formalisms proposed by the AAPM Task Group 60 and Task Group 149. The active core length of the new ⁹⁰Y source was increased to 4.7 mm compared to the value of 2.5 mm for the old ⁹⁰Sr/⁹⁰Y source. The Monte Carlo simulation toolkit Geant4 was used to calculate these parameters. The source was located in a 30-cm-radius theoretical sphere water phantom.

Results

The dosimetric data included the reference absorbed dose rate, the radial dose function in the range of 1.0 to 8.0 mm in the longitudinal axis, and the anisotropy function with a θ in the range of 0° to 90° at 5° intervals and an r in the range of 1.0 to 8.0 mm in 0.2-mm intervals. The reference absorbed dose rate for the new ⁹⁰Y source was determined to be equal to 1.6608 ± 0.0008 cGy s^–1 mCi^–1, compared to the values of 0.9063 ± 0.0005 cGy s^–1 mCi^–1 that were calculated for the old ⁹⁰Sr/⁹⁰Y source. A polynomial function was also obtained for the radial dose function by curve fitting.

Conclusions

Dosimetric data are provided for the new ⁹⁰Y brachytherapy source. These data are meant to be used commercially in after-loading system.