A simple method of obtaining off-axis half-value layers for megavoltage photon beams.
We describe a simplified technique for the acquisition of off-axis beam-quality data (i.e., half-value layers in water) for medical linear accelerators. A measurement protocol is presented in which an ordinary beam-scanning water phantom is used to accurately position an ionization chamber at appropriate measuring positions. Attenuation coefficients are calculated by performing a regression on the measured data. The technique uses the smallest fields for which lateral electron equilibrium can be established.
Cancer Institute, Mary Immaculate Hospital Division, Catholic Medical Center of Brooklyn and Queens, Jamaica, New York 11432, USA.
R J
RJ
Barish
D006801:Humans; D008433:Mathematics; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D017785:Photons; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D014867:Water
D014867:Water