Sensitivity of helium beam-modulator design to uncertainties in biological data

Journal Article · Wed May 01 00:00:00 EDT 1991 · Medical Physics; (USA)

DOI:https://doi.org/10.1118/1.596654· OSTI ID:5670322

Petti, P L; Lyman, J T; Castro, J R ^[1]

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1. Research Medicine and Radiation Biophysics Division, University of California, Lawrence Berkeley Laboratory, Berkeley, California 94720 (USA)

The goal in designing beam-modulating devices for heavy charged-particle therapy is to achieve uniform biological effects across the spread-peak region of the beam. To accomplish this, the linear-quadratic model for cell survival has been used to describe the biological response of the target cells to charged-particle radiation. In this paper, the sensitivity of the beam-modulator design in the high-dose region to the values of the linear-quadratic variables {alpha} and {beta} has been investigated for a 215-MeV/u helium beam, and implications for higher LET beams are discussed. The major conclusions of this work are that, for helium over the LET range of 2 to 16 keV/{mu}, uncertainties in measuring {alpha} and {beta} for a given cell type which are of the order 20% or less have a negligible effect on the beam-modulator design (i.e., on the slope of the spread Bragg peak); uncertainties less than or equal to 10% in the dose-averaged LET at each depth are unimportant; and, if the linear-quadratic variables for the tumor differ from those used in the beam-modulator design by a constant factor between about 0.5 and 3, then the resultant nonuniformity in the photon-equivalent dose delivered to the tumor is within {plus minus}2.5%. It is also shown that for any ion, if the nominal values of {alpha} or {beta} used by the beam-modulator design program differ from their actual values by a constant factor, then the maximum errors possible in the beam-modulator design may be characterized by two limiting depth-dose curves such that the ratio of the dose at the proximal end of the spread Bragg curve to the dose at the distal end of the spread peak is given by {alpha}{sub distal}/{alpha}{sub prox} for the steepest curve, and ({beta}{sub distal}/{beta}{sub prox}){sup 1/2} for the flattest curve.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5670322
• Journal Information: Medical Physics; (USA), Vol. 18:3; ISSN 0094-2405
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ION BEAMS
BEAM SHAPING
RADIOTHERAPY
BEAM MONITORING
BIOLOGICAL RADIATION EFFECTS
CELL KILLING
DESIGN
HELIUM IONS
LET
MODULATION
SENSITIVITY
TUMOR CELLS
ANIMAL CELLS
BEAMS
BIOLOGICAL EFFECTS
CHARGED PARTICLES
ENERGY TRANSFER
IONS
MEDICINE
MONITORING
NUCLEAR MEDICINE
RADIATION EFFECTS
RADIOLOGY
THERAPY
550603* - Medicine- External Radiation in Therapy- (1980-)