gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Low Energy Prompt γ-ray Imaging of the Proton Range in Proton Radiation Therapy

Meeting Abstract

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  • C. Butuceanu - Hampton University Proton Therapy Institute, Hampton, USA

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog031

DOI: 10.3205/09ptcog031, URN: urn:nbn:de:0183-09ptcog0311

Published: September 24, 2009

© 2009 Butuceanu.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Outline

Text

A pilot study to validate a method and apparatus to image and monitor dynamically the delivery of proton beam radiation therapy is underway at the Hampton University Proton Therapy Institute (HUPTI) in Virginia, US. This is a collaborative effort by IBA/HUPTI/JLab (Jefferson Lab, Newport News, Virginia, US), which focuses on dynamic imaging of the proton beam during the therapy and specifically the distall falloff position of the beam by means of promp γ -ray measurements.

Recently it has been shown [1] that the prompt γ-ray generated by various interaction mechanisms (nuclear reactions) of a passive proton beam with a target can be clinically used to verify the energy and the range (position of the distal falloff) of the proton beam, ensuring their correct tuning in the treatment planning in proton radiation therapy.

In our concept, we would like to test if there is timely correlation between the spatial distribution of the proton energy, mostly secondary emitted produced along the beam path, specifically at the end of the Bragg peak, and the dynamic position of the beam in the target. In this concept, only the low energy photons with energy less than 200 KeV will be detected in a compact γ-ray imager, designed to be sensitive to this particular low energy range.

A prototype prompt γ-ray detector has been constructed at JLab, consisting of interchangeable scintillator plates coupled to a 2 x 2 H8500 flat panel PMTs, each with 64 anodic pad channels separately read and equipped with resistive type fast readout with 4 output channels per PMT output [2], and therefore with a total of 16 channels PMT readout electronics. To read the output signals, the FPGA-based data aquisition (DAQ) system developed at JLab [3] is used. The data is recorded and analyzed by a Kmax [4] based operator software interface which displays beam images on a single-frame basis or in real-time. The gamma camera is encased in a 4 mm thick tungsten shell (shielding it from low energy γ-rays) with a low energy (<200 keV) photon energy range pinhole collimator. The detector have been designed to preferentially image low energy direct and indirect γ-rays, Compton scattered γ-rays, bremstrahlung radiation from stopping high energy secondary electrons, and x-rays radiation, all emitted from the target as a result of the proton beam energy deposition. The candidate scintilator materials and thicknesses have been selected to have low sensitivity for high energy photons. Several types of pinhole collimator inserts will be tested with the intention of achieving a dynamic image of the distal falloff position of the therapeutic proton beam.

In this contribution we are presenting the main features of this prototype prompt γ-ray detector, preliminary test results in a proton beam at HUPTI, and lessons learned as we move forward with this project.


References

1.
Chul-Hee Min, et al. Prompt gamma measurements for locating the dose falloff region in the proton therapy. Applied Physics Letters. 2006;89:183517. DOI: 10.1063/1.2378561 External link
2.
Popov V, et al. A Novel Readout Concept for Multianode Photomultiplier Tubes with Pad Matrix Anode Layout, N. I. M. Phys Res. 2006;A567:319-322.
3.
Proffitt J, et al. “A Flexible High-Rate USB2 Data Acquisition System for PET and SPECT Imaging”. Puerto Rico: IEEE Medical Imaging Conference; 2005 October 23-29.
4.
McKisson JE, et al. “A Java Distributed Acquisition System for PET and SPECT Imaging”. Honolulu, Hawaii: Conference Record, IEEE Nuclear Science Symposium and Medical Imaging Conference; October 27-November 3 2007.