Experimental validation of magnetically focused proton beams for radiosurgery.

Experimental validation of magnetically focused proton beams for radiosurgery.
Phys Med Biol. 2019 Mar 07;:
Authors: McAuley GA, Teran AV, McGee PQ, Nyguen TT, Slater JM, Slater JD, Wroe AJ
Abstract
We performed experiments using a triplet of quadrupole permanent magnets to focus protons and compared their dose distributions with unfocused collimated beams using energies and field sizes typically employed in proton radiosurgery. Experiments were performed in a clinical treatment room wherein small-diameter proton beams were focused by a magnet triplet placed immediately upstream of a water tank. The magnets consisted of segments of Sm<sub>2</sub>Co<sub>17</sub> rare-earth permanent magnetic material adhered into Halbach cylinders with nominal field gradients of 100, 150, 200, and 250 T/m. Unmodulated beams with initial diameters of 3 mm to 20 mm were delivered using a single scattering system with nominal energies of 127 and 157 MeV (respective ranges of ~10 cm and 15 cm in water), commonly used for proton radiosurgery at our institution. For comparison, small-diameter unfocused collimated beams were similarly delivered. Transverse and depth dose distributions were measured using radiochromic film and a diode detector, respectively, and compared between the focused and unfocused beams. The focused beams produced low-eccentricity beam spots (defined by the 80% dose contour) at Br...

Source: Physics in Medicine and Biology - March 6, 2019 Category: Physics Authors: McAuley GA, Teran AV, McGee PQ, Nyguen TT, Slater JM, Slater JD, Wroe AJ Tags: Phys Med Biol Source Type: research