Reference volume, milligram-hours and external irradiation for the Fletcher applicator.
The ICRU Report 38 recommends the use of reference point doses and reference volumes for the reporting of intracavitary gynecologic therapy. The reference volume enclosed by the 60 Gy isodose for intracavitary therapy alone (which can be represented by hwt) and for combined external and intracavitary therapy (HWT) has no conceptual counterpart in the standard intracavitary systems. We report the relationship of the reference volumes (hwt and HWT) to milligram-hours (mgh) radium equivalent and to dose of external irradiation (XRT) for the Fletcher system. HWT and hwt are directly proportional to mgh, the proportionality constant depending on XRT but not appreciably on moderate changes in source geometry. HWT increases slowly with increasing XRT to about 30 Gy, then increases dramatically with even small increases in XRT. The reasons for this behavior and the possible clinical significance are discussed.
Department of Radiotherapy, Centre Georges-François Leclerc, Dijon, France.
B A
BA
Esche
J M
JM
Crook
J
J
Isturiz
J C
JC
Horiot
D001918:Brachytherapy / Q000295:instrumentation / Q000592:standards*; D004735:Energy Transfer; D005260:Female; D006801:Humans; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted; D012015:Reference Standards; D014594:Uterine Neoplasms / Q000532:radiotherapy*