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[Diagnostic methods for the quantification of radiation injuries of the lungs].

PURPOSE
The aim of this paper is to find techniques for quantifying radiation lung injury after irradiation with lung involvement to improve an early diagnosis.


METHODS
The case of a patient with NSCLC was used to demonstrate different methods in order to quantify a developing pneumopathy after radiation treatment. By means of HRCT studies in the follow-up, a procedure was developed by defining a test-ROI in high-dose areas of the lung and evaluating the corresponding HU-histogramm for the parameters of the lung peak. Changes during the follow-up can be derived from the differential HU-histogram by the determination of a parameter called delta HUrel, which quantifies the shift to higher HU values. Alternatively, a Fourier analysis of the lung pattern within the test-ROI results in a Fourier amplitude distribution, which reacts sensitively to changes during the follow-up. Furthermore, a Fourier-frequency histogram can be derived which is independent of the spatial orientation of the density pattern.


RESULTS
From the HRCT follow-up study, 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 frequency-histogram presentations demonstrate pronounced pattern changes.


CONCLUSION
The presented methods demonstrate possibilities to quantify radiation lung injury. The proven sensitivity can possibly be improved after the introduction of a breath triggered HRCT technique.