Experimental determination of modulation power of lung tissue for particle therapy

• Published in: Physics in medicine & biology Vol. 66; no. 24; pp. 245018 - 245028
• Main Authors: Burg, Jan Michael, Flatten, Veronika, Witt, Matthias, Derksen, Larissa, Weber, Uli, Engenhart-Cabillic, Rita, Vorwerk, Hilke, Zink, Klemens, Baumann, Kilian-Simon
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 21.12.2021
• Subjects: Animals; Bragg peak degradation; Lung - radiation effects; Lung Neoplasms - diagnostic imaging; Lung Neoplasms - pathology; Lung Neoplasms - radiotherapy; lung tissue; modulation power; porous material; Proton Therapy - methods; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Swine; Bragg peak degradation; porous material; modulation power; lung tissue
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/1361-6560/ac3e0d

In particle therapy of lung tumors, modulating effects on the particle beam may occur due to the microscopic structure of the lung tissue. These effects are caused by the heterogeneous nature of the lung tissue and cannot be completely taken into account during treatment planning, because these micro structures are too small to be fully resolved in the planning CT. In several publications, a new material parameter called modulation power ( ) was introduced to characterize the effect. For various artificial lung surrogates, this parameter was measured and published by other groups and ranges up to approximately 1000 m. Studies investigating the influence of the modulation power on the dose distribution during irradiation are using this parameter in the rang of 100-800 m. More precise measurements for on real lung tissue have not yet been published. In this work, the modulation power of real lung tissue was measured using porcine lungs in order to produce more reliable data of for real lung tissue. For this purpose, porcine lungs were frozen in a ventilated state and measurements in a carbon ion-beam were performed. Due to the way the lungs were prepared and transferred to a solid state, the lung structures that modulate the beam could also be examined in detail using micro CT imaging. An optimization of the established methods of measuring the modulation power, which takes better account of the typical structures within lung tissue, was developed as well.