The effect of tumor location and respiratory function on tumor movement estimated by real-time tracking radiotherapy (RTRT) system.
OBJECTIVE
The effects of tumor location and pulmonary function on the motion of fiducial markers near lung tumors were evaluated to deduce simple guidelines for determining the internal margin in radiotherapy without fiducial markers.


METHODS
Pooled data collected by a real-time tumor-tracking radiotherapy system on 42 markers in 39 patients were analyzed. The pulmonary functions of all patients were assessed before radiotherapy. Using chest X-ray film, the position of the marker was expressed relative to the geometry of the unilateral lung. Posterior location meant the area of the posterior half of the lung in a lateral chest X-ray film, and caudal location meant the caudal half of the chest X-ray film; these categories were determined by measuring the distance between the marker and anatomic landmarks, including the apex, costophrenic angle, midline of spinal canal, lateral, anterior, and posterior boundary of the lung.


RESULTS
Before the radiotherapy, 18 patients had obstructive respiratory dysfunction (ratio of forced expiratory volume in 1 s to forced vital capacity [FEV1.0/FVC] <70), 5 patients had constrictive dysfunction (percent vital capacity [%VC] <80), and 3 had mixed dysfunction. Means of FEV1.0/FVC and %VC were 97.0% and 66.5%, respectively. Median tumor movements in the x (left-right), y (anteroposterior), and z (craniocaudal) directions were 1.1 mm, 2.3 mm, and 5.4 mm, respectively. There was no significant correlation between respiratory function and magnitude of marker movement in any direction. Median marker movement in the z direction was 2.6 mm for the cranial location and 11.8 mm for the caudal location, respectively (p < 0.001). Median movement in the z direction was 11.8 mm for posterior location and 3.4 mm for anterior location, respectively (p < 0.01).


CONCLUSIONS
Simple measurement of the relative location on plain chest X-ray film was related, but respiratory function test was not related, to the craniocaudal amplitude of the motion of the fiducial marker near lung tumors.
Onimaru
Rikiya
R
Department of Radiology, Hokkaido University School of Medicine, Sapporo, Japan.
Shirato
Hiroki
H
Fujino
Masaharu
M
Suzuki
Keishiro
K
Yamazaki
Kouichi
K
Nishimura
Masaharu
M
Dosaka-Akita
Hirotoshi
H
Miyasaka
Kazuo
K
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009068:Movement; D019736:Prostheses and Implants; D011859:Radiography; D011878:Radiotherapy / Q000379:methods; D012119:Respiration; D014797:Vital Capacity / Q000502:physiology