Measurement of prompt gamma profiles in inhomogeneous targets with a knife-edge slit camera during proton irradiation. (9th June 2015)

• Record Type: Journal Article
• Authors: Priegnitz, M; Helmbrecht, S; Janssens, G; Perali, I; Smeets, J; Vander Stappen, F; Sterpin, E; Fiedler, F
• Is Part Of: Physics in medicine & biology. Volume 60:Number 12(2015:Jun.)
• Page Start: 4849
• Page End: 4871
• Publication Date: 2015-06-09
• Subjects: proton therapy -- prompt gamma imaging -- range verification -- slit camera -- sensitivity; Biophysics -- Periodicals; Medical physics -- Periodicals; 610.153
• DOI: 10.1088/0031-9155/60/12/4849
• Languages: English
• ISSNs: 0031-9155

Abstract

Abstract: Proton and ion beam therapies become increasingly relevant in radiation therapy. To fully exploit the potential of this irradiation technique and to achieve maximum target volume conformality, the verification of particle ranges is highly desirable. Many research activities focus on the measurement of the spatial distributions of prompt gamma rays emitted during irradiation. A passively collimating knife-edge slit camera is a promising option to perform such measurements. In former publications, the feasibility of accurate detection of proton range shifts in homogeneous targets could be shown with such a camera. We present slit camera measurements of prompt gamma depth profiles in inhomogeneous targets. From real treatment plans and their underlying CTs, representative beam paths are selected and assembled as one-dimensional inhomogeneous targets built from tissue equivalent materials. These phantoms have been irradiated with monoenergetic proton pencil beams. The accuracy of range deviation estimation as well as the detectability of range shifts is investigated in different scenarios. In most cases, range deviations can be detected within less than 2 mm. In close vicinity to low-density regions, range detection is challenging. In particular, a minimum beam penetration depth of 7 mm beyond a cavity is required for reliable detection of a cavity filling with the present setup. Dedicated data post-processing methods may be capable of overcoming this limitation.