AbstractID: 7893 Title: Quality Assurance Autoradiographs of Ir-192 and Sr-90
Intravascular Brachytherapy Sources
Upon receipt, and periodically, intravascular brachytherapy (IVB) sources should be
tested for uniform absorbed dose distributions over specified lengths. We report
autoradiographs for quality assurance (QA) of IVB sources. The Ir-192 source, 132-mCi,
in the Cordis Checkmate Intravascular System was 39 mm long, 10 seeds, and absorbed
dose rate 37.3-cGy/min at 2 mm. The 30 mm 45.1-mCi Sr-90 source in the Novoste
BetaCath System contained 12 pellets 0.64 mm diameter, 2.5 mm long, absorbed dose
rate 640-cGy/min at 2 mm. Autoradiographs used Ready-Pack “V” film (Eastman Kodak,
Inc.) in a Perma-Doc Phantom (Mick Radio-Nuclear Instruments, Inc.) for QA of high
dose rate (HDR) devices. The phantom holds film against a back plate containing
tungsten markers spaced 1 cm apart. The plate holds a removable stainless steel tandem
2-mm below the surface. A 1.5 min Ir-192 60-cGy exposure produced an autoradiograph
with enhanced images of the tungsten makers from photoelectric absorption of gamma
rays in tungsten. For the Sr-90 source the tandem was removed. An exposure of 0.1 min,
64-cGy, yielded an autoradiograpy that shows the tungsten markers attenuate beta rays.
With the tandem replaced, a 1.0 min exposure, absorbed dose unknown, yielded an
autoradiograph from bremsstrahlung radiation, but with no enhanced images of the
tungsten markers. All images exhibited expected lengths and dose uniformity. The
phantom used for HDR QA can be used to QA IVB sources. For beta-rays
autoradiographs, we will present data comparing direct beta ray and bremsstrahlung
dosimetry for quality assurance.