A fixture designed to provide high precision, high throughput routine spatial characterization of th...
This presentation is the property of its rightful owner.
Sponsored Links
1 / 13

Linda Kelley, Steve Axelrod, Mike Powell Xoft, Inc. Acknowledgements to: Aileen Lum, Long Nguyen, PowerPoint PPT Presentation


  • 117 Views
  • Uploaded on
  • Presentation posted in: General

A fixture designed to provide high precision, high throughput routine spatial characterization of the Xoft Axxent™ X-ray source. Linda Kelley, Steve Axelrod, Mike Powell Xoft, Inc. Acknowledgements to: Aileen Lum, Long Nguyen, Carol Raleigh, Rick Walkup, Sara Yao, Zirao Zheng.

Download Presentation

Linda Kelley, Steve Axelrod, Mike Powell Xoft, Inc. Acknowledgements to: Aileen Lum, Long Nguyen,

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Linda kelley steve axelrod mike powell xoft inc acknowledgements to aileen lum long nguyen

A fixture designed to provide high precision, high throughput routine spatial characterization of the Xoft Axxent™ X-ray source

Linda Kelley, Steve Axelrod, Mike Powell

Xoft, Inc.

Acknowledgements to: Aileen Lum, Long Nguyen,

Carol Raleigh, Rick Walkup, Sara Yao, Zirao Zheng


The xoft axxent x ray source

The Xoft Axxent™ X-ray source

  • Miniature x-ray source operating at 50kVp and 300μA

    • 2.2 mm diameter

  • Attached to a flexible high voltage cable and enclosed in a cooling catheter

  • Used in brachytherapy indications

    • Accelerated partial breast irradiation (APBI)

    • Endometrial and rectal

    • Future indications: IORT, superficial …


Motivation it s got to be fast and it s got to be right

Motivation - it’s got to be fast and it’s got to be right!

  • To assure an accurate delivery of radiation, must match TG-43 protocol parameters to within an overall error budget

    • Depth dose distribution

    • Polar distribution

    • Azimuthal asymmetry

    • Output level and stability

      • Using a HDR-1000+ well chamber

  • High throughput

  • We have designed, built and validated an apparatus to accomplish these goals

90°


Manufacturing test fixture mtf

Manufacturing Test Fixture (MTF)

Source

  • Water tank

  • Shielded enclosure with leaded acrylic window

  • Carousel assembly holding all detectors

    • PTW 34013 ion chamber

    • Photodiode devices

    • critical fixtures are Solid WaterTM

  • Shielded bridge and diode amplifiers on top plate

  • Source to be tested is fixed, carousel assembly rotates

Bridge Assembly

Top Plate (raised)

Carousel Assembly

Water Tank Assembly


Carousel plate

Carousel Plate

  • 1cm ion chamber: 1cm depth dose measurement , calibration of all photodiode detectors

  • 2cm C-arm: 6 photodiode detectors:

7cm detector

Polar 0°-150° at 30° spacing.

  • 90°: azimuthal and 2cm depth dose

  • 4cm and 7cm photodiodes: depth dose

  • Source holder

  • 1 cm Ion chamber

    C-arm detectors

    4cm detector

    Alignment assembly

    Source to test

    Carousel plate


    Calibration

    Calibration

    • Position tolerances: .002”

      • Enclosures measured

      • Custom gauges

    • Calibration of Si photodiodes coupled to CsI scintillator

      • Response dependent on spectra

      • All diodes calibrated in situ

      • Ion chamber is moved to each photodiode distance

    • Distance corrections and calibration constants in software

    In use positionCalibration position

    Rotated C-arm


    Detector paths

    Detector paths

    • Detectors read every 20°

    Source to test

    1cm depth dose path

    Polar 150° path

    Polar 120° path

    2cm depth dose 2cm Azimuthal Polar 90° path

    Polar 60° path

    7cm depth dose path

    Polar 30° path

    Polar 0°

    4cm depth dose path


    Linda kelley steve axelrod mike powell xoft inc acknowledgements to aileen lum long nguyen

    • Parameters are measured simultaneously with all 9 detectors.

      • Time to acquire data ~ 10 minutes 4 tests per hour

    • Custom LabVIEW software controls all operation

      • Operation of the source

      • Motion of detectors

      • Recording and processing data

      • Printing of test reports

      • >40,000 source lines of code

    • Safety interlocks


    Validation

    Validation

    • Software was validated and is under document control

    • All equipment was extensively validated

      • Installation, operational and performance qualification

      • Validating all recipes

      • Validating an extensive list of normal and abnormal conditions

        Made possible by: Chocolate!


    Sample printed output

    Sample printed output


    Precision of measurements

    Precision of measurements

    • Performance qualification: repeatability, reproducibility, operator to operator variability

    • No operator adjustments to the source or detector position make the measurements highly reproducible.

    • Operator to operator variability was measured to be less than 1% for 3 operators testing 3 sources during performance qualification

    Polar distribution averaged over azimuthal angles, normalized at 90deg

    Azimuthal deviation from average


    Spatial plots for 25 sources

    Spatial plots for 25 sources

    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.


    Summary

    Summary

    • The MTF provides accurate measurement of the polar, azimuthal and depth dose characteristics of Xoft x-ray sources.

    • Measurements are consistent with those made with a previously validated spatial test fixture

    • Measurements have been verified to be highly reproducible

    • Parameters are measured simultaneously resulting in a high throughput of up to 4 sources per hour

    • With adaptation, the apparatus could be used to characterize other small sources


  • Login