The midline dose distribution for a three-field radiotherapy technique.
At the University of Florida, head and neck cancer often is irradiated using parallel opposed lateral fields (with inferior borders slanted superiorly) and an anterior low neck field. A common criticism is that overlap may occur at the match-line junction of the three fields, resulting in an increased risk of radiation myelitis. One setup for treatment of the oropharynx and two for the larynx were irradiated in an anthropomorphic head and neck phantom made of tissue-equivalent polyacrylamide gel with a two-dimensional thermoluminescent dosimeter array in its sagittal midplane. The results showed that no excess radiation dose was measured at the junction of the three fields. The "spinal cord dose," as percentage of dose to the central axis of the primary field, was as follows: oropharynx setup, 15% to 100%; larynx setup with midline tracheal block, 10% to 90%; larynx setup without tracheal block, 10% to 90%. In conclusion, the University of Florida three-field technique for head and neck cancer produces no measured increase in dose at field junctions.
Meeks
S L
SL
Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, USA.
Williams
R O
RO
Bova
F J
FJ
Mendenhall
W M
WM
Buatti
J M
JM
D000180:Acrylic Resins; D002277:Carcinoma / Q000532:radiotherapy / Q000601:surgery; D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D005431:Florida; D005782:Gels; D006801:Humans; D007822:Laryngeal Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D007825:Laryngectomy; D009187:Myelitis / Q000209:etiology; D009959:Oropharyngeal Neoplasms / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011832:Radiation Injuries / Q000209:etiology; D011835:Radiation Protection / Q000295:instrumentation; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant; D011881:Radiotherapy, Computer-Assisted; D012307:Risk Factors; D013116:Spinal Cord / Q000528:radiation effects; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation; D014132:Trachea / Q000528:radiation effects
D000180:Acrylic Resins; D003037:Cobalt Radioisotopes; D005782:Gels; D019275:Radiopharmaceuticals; C016680:polyacrylamide gels