Relation between radiation-induced whole lung functional loss and regional structural changes in partial irradiated rat lung.
OBJECTIVE
Radiation-induced pulmonary toxicity is characterized by dose, region, and time-dependent severe changes in lung morphology and function. This study sought to determine the relation between the structural and functional changes in the irradiated rat lung at three different phases after irradiation.


METHODS
Six groups of animals were irradiated to 16-22 Gy to six different lung regions, each containing 50% of the total lung volume. Before and every 2 weeks after irradiation, the breathing rate (BR) was measured, and at Weeks 8, 26, and 38 CT was performed. From the computed tomography scans, the irradiated lung tissue was delineated using a computerized algorithm. A single quantitative measure for structural change was derived from changes of the mean and standard deviation of the density within the delineated lung. Subsequently, this was correlated with the BR in the corresponding phase.


RESULTS
In the mediastinal and apex region, the BR and computed tomography density changes did not correlate in any phase. After lateral irradiation, the density changes always correlated with the BR; however, in all other regions, the density changes only correlated significantly (r(2) = 0.46-0.85, p < 0.05) with the BR in Week 26.


CONCLUSIONS
Changes in pulmonary function correlated with the structural changes in the absence of confounding heart irradiation.
Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Peter
P
van Luijk
Alena
A
Novakova-Jiresova
Hette
H
Faber
Marloes N J
MN
Steneker
Harm H
HH
Kampinga
Haarm
H
Meertens
Robert P
RP
Coppes
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D008168:Lung / Q000473:pathology / Q000503:physiopathology / Q000528:radiation effects*; D008297:Male; D011833:Radiation Injuries, Experimental / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration; D013997:Time Factors; D014057:Tomography, X-Ray Computed