Monte Carlo dosimetric characterization of a new high dose rate 169 Yb brachytherapy source and independent verification using a multipoint plastic scintillator detector. Issue 9 (19th July 2020)

• Record Type: Journal Article
• Authors: Famulari, Gabriel; Linares Rosales, Haydee M.; Dupere, Justine; Medich, David C.; Beaulieu, Luc; Enger, Shirin A.
• Is Part Of: Medical physics. Volume 47:Issue 9(2020)
• Page Start: 4563
• Page End: 4573
• Publication Date: 2020-07-19
• Subjects: Geant4 -- IMBT -- mPSD -- shielded applicator -- TG‐43 -- TG‐186 -- Yb‐169; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1002/mp.14336
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: A prototype 169 Yb source was developed in combination with a dynamic rotating platinum shield system (AIM‐Brachy) to deliver intensity modulated brachytherapy (IMBT). The purpose of this study was to evaluate the dosimetric characteristics of the bare/shielded 169 Yb source using Monte Carlo (MC) simulations and perform an independent dose verification using a dosimetry platform based on a multipoint plastic scintillator detector (mPSD). Methods: The TG‐43U1 dosimetric parameters were calculated for the source model using RapidBrachyMCTPS. Real‐time dose rate measurements were performed in a water tank for both the bare/shielded source using a custom remote afterloader. For each dwell position, the dose rate was independently measured by the three scintillators (BCF‐10, BCF‐12, and BCF‐60). For the bare source, dose rate was measured at distances up to 3 cm away from the source over a range of 7 cm along the catheter. For the shielded source, measurements were performed with the mPSD placed at 1 cm from the source at four different azimuthal angles ( 0 ∘, 9 0 ∘, 18 0 ∘, and 27 0 ∘ ). Results: The dosimetric parameters were tabulated for the source model. For the bare source, differences between measured and calculated along‐away dose rates were generally below 5–10%. Along the transverse axis, deviations were, on average (range), 3.3% (0.6–6.2%) for BCF‐10, 1.7% (0.9–2.9%) for BCF‐12, and 2.2% (0.3–4.4%) for BCF‐60. The maximum dose rate reduction due to shielding at a radial distance of 1 cm was 88.8 ± 1.2%, compared to 83.5 ± 0.5% as calculated by MC. Conclusions: The dose distribution for the bare/shielded 169 Yb source was independently verified using mPSD with good agreement in regions close to the source. The 169 Yb source coupled with the partial‐shielding system is an effective technique to deliver IMBT.