Abstract：
:Weighting of given doses from parallel opposed fields is a widespread practice in radiation therapy of cancer in the tonsillar region. In order to determine when weighting is useful, dose distributions on the central axis were calculated for various energies (60Co, 4-, 8-, 15-, and MVp photons), weighting factors, and field separations. Criteria for judging the usefulness of weighting were (i) that variation in the dose across the tumor volume not exceed 10%, and (ii) that the dose to critical tissues outside the target volume be at least 20% less than target volume dose. The clinical situation that met these criteria was a lateral lesion that extended to less than one-third of the transverse diameter of the head, treated with either 60Co, 8, or 4 MVp with 4:1 weighting. Under these conditions, weighting was considered to be justified.
journal_name
Med Physjournal_title
Medical physicsauthors
Wollin M,Gilbert HA,Kagan ARdoi
10.1118/1.594276subject
Has Abstractpub_date
1976-03-01 00:00:00pages
113-6issue
2eissn
0094-2405issn
2473-4209journal_volume
3pub_type
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