Quantitative evaluation of changes in irradiated lung fields after stereotactic irradiation by the Polygon Method.
OBJECTIVE
To evaluate areas of change in lung after thoracic stereotactic irradiation (STI).


METHODS
We developed a method of evaluation named the Polygon Method, to measure the irradiated lung fields of 12 lung tumors treated by STI. Before treatment, each targeted field was divided into several circular zones of 2 cm in width centered at the tumor on high resolution computed tomography, and the areas of each zone before and after treatment were compared.


RESULTS
Six months after treatment, the areas of the zone within 2 cm from the tumor decreased, and the mean ratio of areas after and before STI was 0.849 (range, 0.515 to 1.052, p=0.0254). By contrast, the areas of zones located at 4 to 6, 6 to 8, 8 to 10, and more than 10 cm from the tumor tended to increase, with mean ratios of 1.059, 1.058, 1.089 (p=0.0374), and 1.084, respectively.


CONCLUSIONS
After thoracic STI, volume loss in the lung is limited to the field in close proximity to the tumor, while compensatory expansion of the lung occurs in fields distant from the tumor.
Yamada
Yuji
Y
Division of Multidisciplinary Radiotherapy, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka 565-0871, Japan.
Shiomi
Hiroya
H
Sumida
Iori
I
Suzuki
Osamu
O
Isohashi
Fumiaki
F
Oh
Ryoong-Jin
RJ
Tanaka
Eiichi
E
Inoue
Takehiro
T
Nakamura
Hironobu
H
D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000601:surgery*; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary / Q000601:surgery*; D008297:Male; D017564:Radiation Pneumonitis / Q000000981:diagnostic imaging; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods*