A photon spectrometric dose-rate constant determination for the Advantage Pd-103 brachytherapy source.
OBJECTIVE
Although several dosimetric characterizations using Monte Carlo simulation and thermoluminescent dosimetry (TLD) have been reported for the new Advantage Pd-103 source (IsoAid, LLC, Port Richey, FL), no AAPM consensus value has been established for the dosimetric parameters of the source. The aim of this work was to perform an additional dose-rate constant (lamda) determination using a recently established photon spectrometry technique (PST) that is independent of the published TLD and Monte Carlo techniques.


METHODS
Three Model IAPD-103A Advantage Pd-103 sources were used in this study. The relative photon energy spectrum emitted by each source along the transverse axis was measured using a high-resolution germanium spectrometer designed for low-energy photons. For each source, the dose-rate constant was determined from its emitted energy spectrum. The PST-determined dose-rate constant (PST lamda) was then compared to those determined by TLD (TLD lamda) and Monte Carlo (MC lamda) techniques. A likely consensus lamda value was estimated as the arithmetic mean of the average lamda values determined by each of three different techniques.


RESULTS
The average PST lamda value for the three Advantage sources was found to be (0.676 +.- 0.026) cGyh(-1) U(-1). Intersource variation in PST lamda was less than 0.01%. The PST lamda was within 2% of the reported MC lamda values determined by PTRAN, EGSnrc, and MCNP5 codes. It was 3.4% lower than the reported TLD lamda. A likely consensus lamda value was estimated to be (0.688 +/- 0.026) cGyh(-1) U(-1), similar to the AAPM consensus values recommended currently for the Theragenics (Buford, GA) Model 200 (0.686 +/- 0.033) cGyh(-1) U(-1), the NASI (Chatsworth, CA) Model MED3633 (0.688 +/- 0.033) cGyh(-1) U(-1), and the Best Medical (Springfield, VA) Model 2335 (0.685 +/- 0.033) cGyh(-1) U(-1) 103Pd sources.


CONCLUSIONS
An independent lamda determination has been performed for the Advantage Pd-103 source. The PST lamda obtained in this work provides additional information needed for establishing a more accurate consensus lamda value for the Advantage Pd-103 source.
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA. zhe.chen@yale.edu
Zhe Jay
ZJ
Chen
Paul
P
Bongiorni
Ravinder
R
Nath
D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D010165:Palladium / Q000032:analysis* / Q000627:therapeutic use*; D017785:Photons; D019736:Prostheses and Implants; D011868:Radioisotopes / Q000032:analysis* / Q000627:therapeutic use*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000379:methods*
D011868:Radioisotopes; D010165:Palladium