High-energy proton imaging for biomedical applications.

The charged particle community is looking for techniques exploiting proton interactions instead of X-ray absorption for creating images of human tissue. Due to multiple Coulomb scattering inside the measured object it has shown to be highly non-trivial to achieve sufficient spatial resolution. We present imaging of biological tissue with a proton microscope. This device relies on magnetic optics, distinguishing it from most published proton imaging methods. For these methods reducing the data acquisition time to a clinically acceptable level has turned out to be challenging. In a proton microscope, data acquisition and processing are much simpler. This device even allows imaging in real time. The primary medical application will be image guidance in proton radiosurgery. Proton images demonstrating the potential for this application are presented. Tomographic reconstructions are included to raise awareness of the possibility of high-resolution proton tomography using magneto-optics.

Commissioning of the PRIOR proton microscope.

Recently, a new high energy proton microscopy facility PRIOR (Proton Microscope for FAIR Facility for Anti-proton and Ion Research) has been designed, constructed, and successfully commissioned at GSI Helmholtzzentrum für Schwerionenforschung (Darmstadt, Germany). As a result of the experiments with 3.5-4.5 GeV proton beams delivered by the heavy ion synchrotron SIS-18 of GSI, 30 µm spatial and 10 ns temporal resolutions of the proton microscope have been demonstrated. A new pulsed power setup for studying properties of matter under extremes has been developed for the dynamic commissioning of the PRIOR facility. This paper describes the PRIOR setup as well as the results of the first static and dynamic proton radiography experiments performed at GSI.

First biological images with high-energy proton microscopy.

High-energy proton microscopy provides unique capabilities in penetrating radiography including the combination of high spatial resolution and field-of-view, dynamic range of density for measurements, and reconstructing density variations to less than 1% inside volumes and in situ environments. We have recently proposed to exploit this novel proton radiography technique for image-guided stereotactic particle radiosurgery. Results of a first test for imaging biological and tissue-equivalent targets with high-energy (800 MeV) proton microscopy are presented here. Although we used a proton microscope setup at ITEP (Moscow, Russia) optimized for fast dynamic experiments in material research, we could reach a spatial resolution of 150 µm with approximately 10(10) protons per image. The potential of obtaining high-resolution online imaging of the target using a therapeutic proton beam in the GeV energy region suggests that high-energy proton microscopy may be used for image-guided proton radiosurgery.