Quantification of radiation lung injuries.

Purpose: The aim of this paper is to find techniques for quantifying radiat ion lung injury after irradiation with lung involvement to improve an early diagnosis. Methods: The case of a patient with NSCLC was used to demonstra te different methods in order to quantify a developing pneumopathy after ra diation treatment. By means of HRCT studies in the follow-up, a procedure w as developed by defining a test-ROI in high-dose areas of the lung and eval uating the corresponding HU-histogramm for the parameters of the lung peak. Changes during the follow-up can be derived from the differential HU-histo gram by the determination of a parameter called Delta HUrel, which quantifi es the shift to higher HU values. Alternatively, a Fourier analysis of the lung pattern within the test-ROI results in a Fourier amplitude distributio n, which reacts sensitively to changes during the followup. Furthermore, a Fourier-frequency histogram can be derived which is independent of the spat ial orientation of the density pattern. Results: From the HRCT follow-up st udy, values for Delta HUrel can be derived to be 0.24, 0.44, and 0.50 (56, 100 and 422 days after beginning the treatment). The differential Fourier f requency-histogram presentations demonstrate pronounced pattern changes. Co nclusion: The presented methods demonstrate possibilities to quantify radia tion lung injury. The proven sensitivity can possibly be improved after the introduction of a breath triggered HRCT technique.