Radiation and Cancer Physics

SS 01 - Physics 1 -Best of Physics

10 - Virtual Bronchoscopy-Guided Dose Response Modeling of Airways to Mitigate Radiation Induced Airway Injury in Lung Sabr

Sunday, October 21
1:55 PM - 2:05 PM
Location: Room 214 A/B

Virtual Bronchoscopy-Guided Dose Response Modeling of Airways to Mitigate Radiation Induced Airway Injury in Lung Sabr
S. Samanta1, A. Modiri2, T. Rozario3, J. Yu4, Y. Yan5, R. D. Timmerman6, and A. Sawant2; 1University of Maryland, Dept. of Radiation Oncology, Baltimore, MD, 2Department of Radiation Oncology, University of Maryland, School of Medicine, Baltimore, MD, 3UT Southwestern Medical Center, Dallas, TX, 4Bronchus Medical Inc, San Jose, CA, 5The University of Texas Southwestern Medical Center, Dallas, TX, 6Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX

Purpose/Objective(s): Preserving post-treatment lung function is an important consideration in lung stereotactic ablative radiotherapy (SAbR). An important yet poorly understood toxicity in lung SAbR is radiation injury to the individual segments of the airway tree, especially the peripheral elements, which are essential for gas conduction to and from the alveoli. Here, we use virtual bronchoscopy to spatially map central and peripheral airways for individual patients, and estimate the radiation dose response for these airway segments as quantified by the dose-dependent probability of airway collapse.

Materials/Methods: Under IRB approval, pre- and post-SAbR diagnostic-quality CT scans were retrospectively collected from three lung cancer patients. For each patient, the pre and post-SAbR bronchial trees were segmented using a research version of a commercially available virtual bronchoscopy software (Archimedes, Bronchus, San Jose, CA). The post SAbR bronchial tree was deformably registered (MIM Vista) to the pre SAbR tree to identify airways that had collapsed post-treatment. The airways were imported as RTStructs into a commercial treatment planning system (Eclipse, Varian Medical Systems) and doses received by individual airway segments from the clinical RT plan were computed. In a previous multivariate analysis, we had shown that airway collapse was closely associated with max point dose(Dmax) and airway diameter. Accordingly, logistic regression was utilized to fit a dose-response curve as a function of segmental collapse based on Dmax to and mean diameter of individual airways.

Results: A total of 648 airway segments were segmented and analyzed. The min, max and median diameters were 3.2, 24.4 and 4.14 mm respectively. We limited our study to the airways with diameters 3-6 mm since larger airways (>6 mm) did not show collapse even at the highest dose level. The collapse of smaller diameter airways (3-6 mm) was significantly correlated with Dmax and airway diameter (P<0.001 for both). The probability of collapse of the small airways as function of dose is represented in the table below. Our estimated dose response curve exhibited a 78% accurate prediction rate for airway collapse across all diameters.
Airway diameter Dose (Gy) for various probabilities of collapse
30% 40% 50% 70%
3-4 mm 1 1.43 10.40 29.14
4.1-5 mm 15.88 25.65 34.62 53.36
5.1-6 mm 40.10 49.87 58.84 77.57

Conclusion: Using virtual bronchoscopy guidance, we demonstrated the feasibility of spatially mapping and quantitatively estimating the radiation dose response of individual segments of the airway tree. Beyond the present scope, such improved understanding of radiation injury to airways will enable current and future novel treatment planning strategies to minimize airway injury and thereby better preserve post-SAbR respiratory function.

Author Disclosure: S. Samanta: None. A. Modiri: None. J. Yu: None. Y. Yan: None. R.D. Timmerman: Research Grant; Varian Medical Systems, Accuray, Inc, Elekta Oncology.

Send Email for Santanu Samanta


Assets

10 - Virtual Bronchoscopy-Guided Dose Response Modeling of Airways to Mitigate Radiation Induced Airway Injury in Lung Sabr



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for Virtual Bronchoscopy-Guided Dose Response Modeling of Airways to Mitigate Radiation Induced Airway Injury in Lung Sabr