SU‐GG‐BRC‐07: 4DCT‐Based Measurement of Radiation Induced Changes in Pulmonary Function

Purpose The present treatment‐planning dosimetry constraints for the lung are based on studies that assume lung tissue is homogeneous in its response to toxicity, irrespective of tissue location or underlying function. No human studies have investigated the relationships between local lung function, spatial radiation dose distribution, and radiation induced lung function changes. We are able to observe radiation‐induced changes in lung tissue function using 4DCT and image registration. Method and Materials Two 4DCT data sets before and after RT from one patient are used in this study. Nonlinear, 3D image registration was applied to register the maximum exhalation image to the maximum inhalation image for the calculation of local lung expansion as a measurement of regional pulmonary function. We compared the changes of pulmonary function before and after RT with planned radiation dose at different locations of the lung. Results The registration accuracy analysis indicated our registration error is on the order of 1 mm. The pulmonary function change in left lung where the tumor is located is larger than it is in right lung (maximum Jacobian change is respectively 0.23 and 0.15). The highest correlation of the pulmonary function change to the delivered radiation dose is in regions which are at the distance of 20 to 25 mm to the tumor region (linear regression, r = −0.73). Further plots between the radiation dose and the pulmonary function change suggest the lung tissue function change is not sole based on radiation dose. Conclusion We described a technique that uses 4DCT, image registration and biomechanical analysis to measure regional lung function. We compared the regional lung function before and after RT to the planned radiation dose distribution and examined the differences at the treatment location and in non‐treatment regions. Conflict of Interest VIDA Diagnostics, Inc (shareholder).