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TU‐H‐CAMPUS‐TeP2‐01: A Comparison of Noninvasive Techniques to Assess Radiation‐Induced Lung Damage in Mice
Author(s) -
Rubinstein A,
Kingsley C,
Melancon A,
Tailor R,
Pollard J,
Guindani M,
Followill D,
Hazle J,
Court L
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4957689
Subject(s) - nuclear medicine , contouring , lung , respiratory system , lung volumes , breathing , medicine , respiratory rate , lung cancer , thorax (insect anatomy) , radiology , pathology , anatomy , heart rate , engineering drawing , engineering , blood pressure
Purpose: To evaluate the use of post‐irradiation changes in respiratory rate and CBCT‐based morphology as predictors of survival in mice. Methods: C57L/J mice underwent whole‐thorax irradiation with a Co‐60 beam to four different doses [0Gy (n=3), 9Gy (n=5), 11Gy (n=7), and 13Gy (n=5)] in order to induce varying levels of pneumonitis. Respiratory rate measurements, breath‐hold CBCTs, and free‐breathing CBCTs were acquired pre‐irradiation and at six time points between two and seven months post‐irradiation. For respiratory rate measurements, we developed a novel computer‐vision‐based technique. We recorded mice sleeping in standard laboratory cages with a 30 fps, 1080p webcam (Logitech C920). We calculated respiratory rate using corner detection and optical flow to track cyclical motion in the fur in the recorded video. Breath‐hold and free‐breathing CBCTs were acquired on the X‐RAD225Cx system. For breathhold imaging, the mice were intubated and their breath was held at full‐inhale for 20 seconds. Healthy lung tissue was delineated in the scans using auto‐threshold contouring (0–0.7 g/cm 3 ). The volume of healthy lung was measured in each of the scans. Next, lung density was measured in a 6‐mm 2 ROI in a fixed anatomic location in each of the scans. Results: Day‐to‐day variability in respiratory rate with our technique was 13%. All metrics except for breath‐hold lung volume were correlated with survival: lung density on free‐breathing (r=−0.7482,p<0.01) and breath‐hold images (r=−0.5864,p<0.01), free‐breathing lung volume (r=0.7179,p<0.01), and respiratory rate (r= 0.6953,p<0.01). Lung density on free‐breathing scans was correlated with respiratory rate (r=0.7142,p<0.01) and lung density on breath‐hold scans (r=0.5543,p<0.01). One significant practical hurdle in the CBCT measurements was that at least one lobe of the lung was collapsed in 36% of free‐breathing scans and 45% of breath‐hold scans. Conclusion: Lung density and lung volume on free‐breathing CBCTs and respiratory rate outperform breath‐hold CBCT measurements as indicators for survival from radiation‐induced pneumonitis. This work was partially funded by Elekta.