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Proton Beam Therapy Treatment Techniques

Proton Beam Therapy Treatment Techniques
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Proton Beam Therapy Treatment Techniques - 1

Proton Therapy System PROTON BEAM THERAPY SCATTERING VERSUS SCANNING TREATMENT TECHNIQUES Protons have potential advantages over photons for delivering higher radiation doses to the tumor while sparing the surrounding healthy tissue. Though protons are inherently capable of higher dose conformity and lower integral dose to the body, the method of proton beam delivery is an important consideration as well. Beam delivery methods Two proton beam delivery methods are available today: passive spreading, which includes single and dual scattering, and active spreading, which is commonly known as scanning. In passive spreading techniques, the proton beam is spread by placing scattering material in its path. A single scatterer broadens the beam sufficiently for the coverage of small fields. For larger fields, a second scatterer is needed to ensure a uniform dose profile. A combination of custom-made collimators and compensators conform the dose to the target volume. The spread out Bragg peak (SOBP) used for treatment is obtained by a set of range modulator wheels or ridge filters inside the gantry of the delivery system. (See Figure 1.) In scanning beam techniques, magnets deflect and steer the proton beam. Under computer control, the beam “paints” the treatment volume, voxel by voxel, in successive layers. The depth of penetration of the Bragg peak is adjusted by varying the energy of the beam before it enters the gantry. (See Figure 2.) Patient Scatterer Modulator wheels or ridge filters Target Extra dose Scatterer (contoured) Figure 1: Scattering diagram Treatment volume Magnets Figure 2: Scanning diagr

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Proton Beam Therapy Treatment Techniques - 2

SCATTERING VERSUS SCANNING AT A GLANCE How do these two delivery methods compare in a clinical setting? Are there differences in the conformity of the treatment, or the integral dose to patients? What should centers consider when choosing a proton therapy system? The following table addresses these questions through a side-by-side comparison of scattering versus scanning to help clinicians determine the most appropriate treatment method. SCANNING Beam modifying devices Dual scattering uses patient-specific beam-modifying devices to conform the dose to the treatment volume. These devices...

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Proton Beam Therapy Treatment Techniques - 3

SCANNING IMPT With dual scattering, the ability to vary the dose distribution throughout the treatment volume is limited. Multiple fields can deposit dose from different directions. However, multiple fields require a complex set of compensators and apertures, and switching them adds to the treatment time. Scanning makes IMPT possible. With scanning, dose distributions can be varied voxel by voxel. By varying the beam intensity or the speed of the scan, or both, dose is painted non-uniformly on a field-by-field basis to yield an overall uniform target dose. The scanning technique lets...

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Proton Beam Therapy Treatment Techniques - 4

Proton Therapy System VARIAN PROTON THERAPY Varian stakes its global reputation on giving patients and clinicians innovative treatment technology for fighting cancer. Our mission is to help save more lives, improve the quality of treatment, and provide solutions for treating a wide range of cancers. Proton therapy is one weapon in Varian’s advanced treatment arsenal, and we intend to drive its development forward as we have other modes of radiation treatment. Our pledge is this: when you want sophisticated, advanced treatments, you can turn to Varian. References Blom M, Glimelius B, Lorin...

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