A 3-Dimensional Beam Scanning System for Particle Radiation Therapy

Abstract

In radiation therapy treatment volumes up to several liters have to be irradiated. Today's charged particle programs use ridge filters, scattering foils, occluding rings collimators and boluses to shape the dose distribution. 1 An alternative approach, scanning of a small diameter beam, is analyzed and tentative systems specifications are derived. Critical components are scheduled for fabrication and testing at LBL.. , " This report was done with support from the United States Energy Research and Development Administration. Any conclusions or opinions expressed in this report represent solely those of the author(s) and not necessarily those of The Regents' of the University of California, the Lawrence Berkeley Laboratory or the United States Energy Research and Development Administration.

Heavy Charged Particle Radiotherapy

“…results in overdosing normal tissues in other areas. Beam scanning may be used to overcome this disadvantage (36,44). In beam scanning, a charged particle pencil beam is scanned across the field by magnetic lenses.…”

Magnetically scanned ion beams for radiation therapy

“…The Raster Scanner [6] (Fig ld) has a fast sweep saw-tooth drive and a slow sweep single pass for each spill from the accelerator. The Pixel Scanner [7] (Fig le) dwells at one spot delivering the desired dose at that spot before moving to the next spot. These systems all provide great flexibility in treatment delivery options, with prospects of good improvements in the quality of treatments which can be delivered.…”

“…Analysis [7] of scanning with the smallest possible spot size indicates that very high instantaneous dose rates, possibly as high as 104 Gy/second, as well as very short dwell times at each voxel, around 100 J.Lsec, will be necessary to cover the treatment field in about 1 minute. Not only are precision of dosimetry and overall control and magnet slewing rates critical problems, but even the biological effects of such high instantaneous dose rates are an important unknown.…”

“…A single scanning magnet sweeps the beam Magnetically Scanned Beams 7 Alonso back and forth in the {x} direction across a defining aperture of fixed {dy} whose limits {x(min),…”