Effects of density changes in the chest on lung stereotactic radiotherapy.
To experimentally and theoretically evaluate dose distribution during lung stereotactic radiotherapy, we investigated the relative electron densities in lung and tumor tissues using X-ray computed tomography images obtained from 30 patients in three breathing states: free breathing, inspiration breath-hold, and expiration breath-hold. We also calculated dose distribution using Monte Carlo simulation for lung tissue with two relative electron densities. The effect of changes in relative electron density on dose distribution in lung tissue was evaluated using calculated differential and integral dose volume histograms. The relative electron density of lung tissue was 0.22 in free breathing, 0.23 in shallow expiration, and 0.17 in shallow inspiration, and there was a tendency for relative electron density to decrease with age. The relative electron density of tumor tissue was approximately 0.9, with little variation due to differences in breathing state. As the relative electron density of lung tissue decreases, the low-dose region expands and leads to changes in the marginal dose.
Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-machi, Ibaraki 300-0394, JAPAN.
Tatsuya
T
Fujisaki
Kyoko
K
Kikuchi
Hidetoshi
H
Saitoh
Naoki
N
Tohyama
Atsushi
A
Myojoyama
Atsushi
A
Osawa
Akio
A
Kuramoto
Shinji
S
Abe
Tesuo
T
Inada
Takatsugu
T
Kawase
Etsuo
E
Kunieda
D000367:Age Factors; D000368:Aged; D004583:Electrons; D045853:Exhalation / Q000502:physiology; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008297:Male; D009010:Monte Carlo Method; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012119:Respiration; D013238:Stereotaxic Techniques; D036542:Tomography, Spiral Computed; D014057:Tomography, X-Ray Computed