Clinical characterization of a proton beam continuous uniform scanning system with dose layer stacking

Journal Article · Sat Nov 15 04:00:00 EST 2008 · Medical Physics

DOI:https://doi.org/10.1118/1.2982248· OSTI ID:22095247

Farr, J. B.; Mascia, A. E.; Hsi, W. -C.; Allgower, C. E.; Jesseph, F.; Schreuder, A. N.; Wolanski, M.; Nichiporov, D. F.; Anferov, V. ^[1]

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1. Indiana University, Department of Physics, Swain Hall West, Room 117, 727 E. Third St., Bloomington, Indiana 47405 and Midwest Proton Radiotherapy Institute, 2425 Milo B. Sampson Lane, Bloomington, Indiana 47408 (United States)

A proton beam delivery system on a gantry with continuous uniform scanning and dose layer stacking at the Midwest Proton Radiotherapy Institute has been commissioned and accepted for clinical use. This paper was motivated by a lack of guidance on the testing and characterization for clinical uniform scanning systems. As such, it describes how these tasks were performed with a uniform scanning beam delivery system. This paper reports the methods used and important dosimetric characteristics of radiation fields produced by the system. The commissioning data include the transverse and longitudinal dose distributions, penumbra, and absolute dose values. Using a 208 MeV cyclotron's proton beam, the system provides field sizes up to 20 and 30 cm in diameter for proton ranges in water up to 27 and 20 cm, respectively. The dose layer stacking method allows for the flexible construction of spread-out Bragg peaks with uniform modulation of up to 15 cm in water, at typical dose rates of 1-3 Gy/min. For measuring relative dose distributions, multielement ion chamber arrays, small-volume ion chambers, and radiographic films were employed. Measurements during the clinical commissioning of the system have shown that the lateral and longitudinal dose uniformity of 2.5% or better can be achieved for all clinically important field sizes and ranges. The measured transverse penumbra widths offer a slight improvement in comparison to those achieved with a double scattering beam spreading technique at the facility. Absolute dose measurements were done using calibrated ion chambers, thermoluminescent and alanine detectors. Dose intercomparisons conducted using various types of detectors traceable to a national standards laboratory indicate that the measured dosimetry data agree with each other within 5%.

• OSTI ID: 22095247
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 11 Vol. 35; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
62 RADIOLOGY AND NUCLEAR MEDICINE
BRAGG CURVE
COMMISSIONING
COMPARATIVE EVALUATIONS
CYCLOTRONS
DOSIMETRY
IONIZATION CHAMBERS
MEV RANGE 100-1000
PROTON BEAMS
PROTONS
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOTHERAPY
SCATTERING