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E-poster Presented by ProTom at PTCOG58 is ready to Download!

The 58th Annual Conference of the Particle Therapy Co-operative Group (PTCOG57) was held June 10-15, 2019 at the Manchester Convention Center in Manchester, UK.

This year, ProTom worked with the physics team from University of Adelaide to present a E-Poster at the conference. Click here to download:

Relative Stopping Power (RSP) and Water Equivalent Thickness (WET) measurements of phantoms using x-ray flat panel detector and scanned proton beam.

Introduction

An x-ray flat panel detector was used to measure the WET of a head phantom measured via proton radiography and compare to the WET calculated from the DRR. The RSP of a tissue characterization phantom (Gammex model 467) was also calculated.

Previous experiments have shown the validity of using proton radiography for calculating WET values. In lieu of a dedicated proton tracking and range system,  easy clinical integration can be realized by utilizing existing systems, such as a flat panel detector.

Methods

A total of 35 layers ranging from 140 MeV– 222 MeV were used to measure the phantom WET in 9 locations using the Energy Resolved Dose Function (ERDF) method. These values were compared to the WET calculated from the DRR of the head phantom (via HU lookup table) or the Bethe-Bloch relation (for the tissue phantom).

Deliver low intensity spots       Compare WET from DRR and pR

         

Results

  • The WET values of the 9 ROIs were accurately measured with proton radiography. Comparison to the WET values calculated from the DRR show agreement when the registration is correct and there are no anatomical changes. Discrepancies between the calculated WET and measured WET can indicate positioning errors or anatomical changes occurring between CT and treatment.
  • Tissue Phantom RSP values found via proton radiography were all within 1.5% of calculated values, with the exception of adipose tissue.

Discussion

Proton radiography with a scanned pencil beam can be used to check the WET of a patient immediately before treatment, allowing immediate detection of any anatomical changes. Use of an x-ray flat panel simplifies clinical integration by utilizing readily available equipment.

Head Phantom:Measured vs Calculated WET values at 9 locations

 

The Radiance 330© is the first proton therapy system specifically designed and built for proton therapy. With up to 330 MeV beam energy, future capabilities include proton tomography and proton radiography.