Verification of proton range, position, and intensity in IMPT with a 3D liquid scintillator detector system

Journal Article · Thu Mar 15 04:00:00 EDT 2012 · Medical Physics

DOI:https://doi.org/10.1118/1.3681948· OSTI ID:22098774

Archambault, L.; Poenisch, F.; Sahoo, N.; Robertson, D.; Lee, A.; Gillin, M. T.; Mohan, R.; Beddar, S. ^[1]

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1. Departments of Radiation Physics, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 (United States)

Purpose: Intensity-modulated proton therapy (IMPT) using spot scanned proton beams relies on the delivery of a large number of beamlets to shape the dose distribution in a highly conformal manner. The authors have developed a 3D system based on liquid scintillator to measure the spatial location, intensity, and depth of penetration (energy) of the proton beamlets in near real-time. Methods: The detector system consists of a 20 x 20 x 20 cc liquid scintillator (LS) material in a light tight enclosure connected to a CCD camera. This camera has a field of view of 25.7 by 19.3 cm and a pixel size of 0.4 mm. While the LS is irradiated, the camera continuously acquires images of the light distribution produced inside the LS. Irradiations were made with proton pencil beams produced with a spot-scanning nozzle. Pencil beams with nominal ranges in water between 9.5 and 17.6 cm were scanned to irradiate an area of 10 x 10 cm square on the surface of the LS phantom. Image frames were acquired at 50 ms per frame. Results: The signal to noise ratio of a typical Bragg peak was about 170. Proton range measured from the light distribution produced in the LS was accurate to within 0.3 mm on average. The largest deviation seen between the nominal and measured range was 0.6 mm. Lateral position of the measured pencil beam was accurate to within 0.4 mm on average. The largest deviation seen between the nominal and measured lateral position was 0.8 mm; however, the accuracy of this measurement could be improved by correcting light scattering artifacts. Intensity of single proton spots were measured with precision ranging from 3 % for the smallest spot intensity (0.005 MU) to 0.5 % for the largest spot (0.04 MU). Conclusions: Our LS detector system has been shown to be capable of fast, submillimeter spatial localization of proton spots delivered in a 3D volume. This system could be used for beam range, intensity and position verification in IMPT.

• OSTI ID: 22098774
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 3 Vol. 39; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BRAGG CURVE
CAMERAS
CHARGE-COUPLED DEVICES
DISTRIBUTION
IRRADIATION
LIGHT SCATTERING
LIQUID SCINTILLATION DETECTORS
NOZZLES
PHANTOMS
PROTON BEAMS
RADIATION DOSE DISTRIBUTIONS
RADIOTHERAPY
SIGNAL-TO-NOISE RATIO
SURFACES