title: Surface dose for tangentially incident photon beams in the presence of air gap and air cavity.
abstract: Dose to a surface parallel to an incident photon beam has been investigated in the presence of air gaps and air cavities. Measurements have been made in an acrylic phantom with a parallel plate chamber. Photon beams of Co 60, 4-MV, 6-MV, and 15-MV X-rays have been investigated. The results of our measurements show that in the case of air gaps, the dose reduction to a tangential surface is considerable. On the other hand, the dose reduction is 2% or less in the case of air cavity for volumes encountered in clinical situations.
authors.affiliation: SUNY Health Science Center, Department of Radiology 13210, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Prasad
authors.forename: C T
authors.initials: CT
authors.lastname: Chung
mesh_terms: D000388:Air; D008961:Models, Structural; D017785:Photons; D011829:Radiation Dosage