Xoft Manufacturing Procedures Every Source Tested Thoroughly

Xoft Tests Every Source we Build Testing of an isotope seed typically consists simply of a measurement of the output level Spatial characteristics are just as important to accurate treatment as the overall output Xoft sources are tested for output, polar and azimuthal distributions, depth dose and dose rate constant Being electronic sources, they are also tested for several stability related parameters

Xoft Manufacturing Test Fixture From an AAPM 2008 oral presentation A high precision, high throughput fixture for routine spatial characterization of the Xoft Axxent™ miniature x-ray source Describes the custom built device which tests every Xoft source Polar distribution Azimuthal symmetry Depth dose Dose rate constant

Manufacturing Test Fixture (MTF) Design Source Water tank phantom Shielded enclosure with leaded acrylic window Carousel assembly holding all detectors Shielded bridge and diode amplifiers on top plate Source to be tested is fixed, carousel assembly rotates Bridge Assembly Top Plate (raised) Carousel Assembly Acrylic water tank Leaded acrylic and stainless steel enclosure Carousel assembly with all detectors PTW 34013 ion chamber Hamamatsu S8559 Scintillator/photodiodes critical fixtures are Solid WaterTM Source to be tested is fixed, carousel assembly rotates Shielded bridge on top plate with diode amplifiers Water Tank Assembly

MTF Carousel Plate 1 cm miniature x-ray ion chamber 2 cm C-arm: 6 photodiode detectors Cross-calibrated to ion chamber 7cm detector 1 cm Ion chamber C-arm detectors C-arm measures polar distribution Carousel rotates around source Detector at various distances measure depth dose 4cm detector 1cm: miniature soft x-ray ionization chamber used to measure depth dose can be moved to all other diode distances to calibrate the photodiode detectors 2cm C arm photodiode detectors: 0°,30°,60°,90°,120°,150°. Hamamatsu S8559 x-ray monitor detector designed for x-ray detection below 100keV 5.8mm diameter CsI scintillator custom gain amplifiers for the different distance detectors calibrated in place with the IC measures the polar distribution at 0,30,60,90,120,150 degrees 90 deg – measures the azimuthal deviation 90deg – measures depth dose 4 and 7 cm photodiodes measure depth dose Source holder fixed stop for positioning the source anode Tolerances .002 in enclosures measured at a metrology house or at xoft custom made gauges for in situ measurements actual detector positions entered into software 90°: azimuthal and 2cm depth dose 4cm and 7cm photodiodes: depth dose Position tolerances: .002” - measured and software corrected Alignment assembly Source to test Carousel plate

MTF Creates a Wealth of Data for Each Source Deviation from TG43 reference Depth dose readings One of a total of 6 sheets describing the spatial parameters and test conditions Go into the record for each accepted source Sample Printed Output – Depth Dose

High Precision Measurements Performance qualification: repeatability, reproducibility, operator to operator variability Operator to operator variability was measured to be less than 1% for 3 operators testing 3 sources during performance qualification Performance qualification repeatability – one source tested 5 times without removing it from the fixture reproducability – one source tested 5 times removing it each time from the fixture operator to operator variability – 3 operators testing 3 sources Azimuthal deviation from average Polar distribution (avg over all azim angles)

Spatial Plots for 25 Sources Show Low Variability Normalized depth dose distributions averaged over azimuthal angle Azimuthal asymmetry as percent deviation from the average. Normalized polar output averaged over azimuthal angle. 0° is along the source axis.

Output Level and Stability From an AAPM 2007 Poster Xoft Routine Per Article Manufacturing Testing of the Axxent® Source Source is cycled 10 times Last cycle held for 20 minutes Data analyzed for peak reproducibility, noise and drift

Xoft’s Policy Every source is tested To ensure that every treatment is safe and accurate