Measurement of dose distributions using film in therapeutic electron beams.
The feasibility of using film dosimetry data as the input data for patient treatment planning was evaluated. The central-axis depth dose and the off-axis ratios obtained from film measurements in a solid phantom were compared with those of ion-chamber measurements in water. Two techniques were used to generate isodose distributions. The first technique used only the film data, i.e., the central-axis depth dose and the off-axis ratios used for the reconstruction were determined from the film optical density (corrected for film nonlinearity). In the second technique, the central-axis depth dose measured by an ion chamber in a water phantom was combined with the off-axis ratios measured using film in the "solid water" phantom. The resulting isodose distributions from both techniques were compared with the ion-chamber measurements in water for 7-, 12-, and 18-MeV electrons, and the second technique showed better agreement with the ion-chamber measurements than did the first technique. The differences were within a clinically acceptable range.
Shiu
A S
AS
Department of Radiation Physics, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Otte
V A
VA
Hogstrom
K R
KR
D004583:Electrons; D005373:Film Dosimetry; D010315:Particle Accelerators; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy