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Updated: Aug 9, 2026

Dosimetry for Cell Irradiation using Orthovoltage (40-300 kV) X-Ray Facilities
Published on: February 20, 2021
Absorbed dose and transmission factor in blocked fields for radiotherapy treatments with 6 MV X-ray
Ana Elena Buenfil1, Marvin Francisco Rodríguez-González, Gabriel Reséndiz González
1Instituto de Física, UNAM, México D.F., México. buenfil@fisica.unam.mx
Abstract:
Absorbed dose and transmission factors were determined for 6 MV X-ray fields applied in four conventional external radiation treatments where protection blocks are used to shield organs at risk. Studied treatments are: head and neck (cancer of the larynx), breast (breast cancer), brain (brain tumours) and pelvis (cervix-uterine cancer). Experimental determinations were made using ionization chambers and thermoluminescent dosimeters, at different locations in phantoms, for blocked and unblocked fields. Calculated absorbed doses, using the treatment planning system and Clarkson method, were compared to those measured. Measured transmission factor values ranged from 5% to 18%. It was found that the planning treatment system may underestimate the absorbed dose under the blocks, up to 35%.
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