Back to Search
Start Over
Out-of-field doses and neutron dose equivalents for electron beams from modern Varian and Elekta linear accelerators.
- Source :
-
Journal of applied clinical medical physics [J Appl Clin Med Phys] 2016 Jul 08; Vol. 17 (4), pp. 442-455. Date of Electronic Publication: 2016 Jul 08. - Publication Year :
- 2016
-
Abstract
- Out-of-field doses from radiotherapy can cause harmful side effects or eventually lead to secondary cancers. Scattered doses outside the applicator field, neutron source strength values, and neutron dose equivalents have not been broadly investigated for high-energy electron beams. To better understand the extent of these exposures, we measured out-of-field dose characteristics of electron applicators for high-energy electron beams on two Varian 21iXs, a Varian TrueBeam, and an Elekta Versa HD operating at various energy levels. Out-of-field dose profiles and percent depth-dose curves were measured in a Wellhofer water phantom using a Farmer ion chamber. Neutron dose was assessed using a combination of moderator buckets and gold activation foils placed on the treatment couch at various locations in the patient plane on both the Varian 21iX and Elekta Versa HD linear accelerators. Our findings showed that out-of-field electron doses were highest for the highest electron energies. These doses typically decreased with increasing distance from the field edge but showed substantial increases over some distance ranges. The Elekta linear accelerator had higher electron out-of-field doses than the Varian units examined, and the Elekta dose profiles exhibited a second dose peak about 20 to 30 cm from central-axis, which was found to be higher than typical out-of-field doses from photon beams. Electron doses decreased sharply with depth before becoming nearly constant; the dose was found to decrease to a depth of approximately E(MeV)/4 in cm. With respect to neutron dosimetry, Q values and neutron dose equivalents increased with electron beam energy. Neutron contamination from electron beams was found to be much lower than that from photon beams. Even though the neutron dose equivalent for electron beams represented a small portion of neutron doses observed under photon beams, neutron doses from electron beams may need to be considered for special cases.
- Subjects :
- Algorithms
Humans
Photons
Radiometry instrumentation
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted instrumentation
Radiotherapy, High-Energy instrumentation
Water
Electrons
Neutrons
Particle Accelerators
Phantoms, Imaging
Radiometry methods
Radiotherapy Planning, Computer-Assisted methods
Radiotherapy, High-Energy methods
Subjects
Details
- Language :
- English
- ISSN :
- 1526-9914
- Volume :
- 17
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Journal of applied clinical medical physics
- Publication Type :
- Academic Journal
- Accession number :
- 27455499
- Full Text :
- https://doi.org/10.1120/jacmp.v17i4.6216