Measurement of I-125 RAPID Strand™ Iodine Seeds

Using Source Holder, SeeDOS Code 70026 with the Standard Imaging HDR 1000 Plus Brachytherapy Well Chamber

Q A measurements within ± 5% of calibrated 6711 iodine seeds can be made without removing the I-125 RAPID Strand™ from the spacing jig.   Short term precision is < 1%.   No measureable rotational dependence.

Close up view of I-125 RAPID StrandTM seeds in carrier

I-125 RAPID StrandTM in Source Holder 70023, ready for a measurement

The Source Holder, SeeDOS Code 70026 has been designed for use with the HDR 1000 Plus Brachytherapy Well Chamber and the Max 4000 Electrometer, SeeDOS Code 90015, which provides a quick and convenient QA measurement of I-125 RAPID Strand™ iodine seeds. This custom source holder uses a standard HDR 1000 Plus so your facility can also measure every other brachytherapy isotope, LDR or HDR. This will eliminate the need to invest in several well chambers dedicated to specific isotopes.

The I-125 RAPID Strand™ Source Holder is constructed to simultaneously measure five seeds at one end of the I-125 RAPID Strand™ while the I-125 RAPID Strand™ remains in the spacing jig. The spacing jig is then inverted and the five seeds at the other end are measured. The source holder itself can be sterilized.

Calibration and Correction Factors

An I-125 RAPID Strand™ containing 10 iodine seeds was obtained and an extensive evaluation was performed with the HDR 1000 Plus and the I-125 RAPID Strand™ Source Holder 70023. Following the evaluation, individual seeds of the I-125 RAPID Strand™ were cut from the strand and individually calibrated. To obtain a correction factor, these measurements were compared to the initial, collective seeds measurements of the intact I-125 RAPID Strand™ in Source Holder 70023.

Seed Activity = (R * CF * C_T/P * EF)/N

R = reading
CF(correction factor) is defined as 1.15 time the single ADCL 6711 iodine seed calibration factor
N = number of seeds
CT/P = correction for temperature and pressure
EF = electrometer correction factor

SeeDOS would like to thank The University of Wisconsin Accredited Dosimetry Calibration Laboratory (ADCL) in Madison Wisconsin, for performing complete initial performance testing of the I-125 RAPID Strand™ Source Holder with the HDR 1000 Plus Brachytherapy Well Chamber.

Rapid Strand, Metastron, and OncoSeed are trademarks of Amersham plc.

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