Proton therapy is continuing to be adopted in elite cancer centers as an option over traditional focused beam radiotherapy. Protons fired at different energies from particle accelerators can be made to stop and ablate precisely the tumor tissue being targeted. The trick is to map out in advance the “stopping power” of the tissue on the way to the tumor. Currently CT scans are used to create these maps, but tissue attenuates X-rays much differently than it does speeding protons, so there’s much room for improvement.
Researchers from UC Santa Cruz, Loma Linda University, and California State University, San Bernardino have developed a technique that uses a proton accelerator to create stopping power maps. They’re currently in early stages of this research, but they’re working toward true proton computed tomography that may one day be a new 3D imaging modality along side MR and X-ray CT.
From UC Santa Cruz:
They presented their findings at the 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference in Anaheim in a poster presentation on October 29 and in an invited talk by Dr. Reinhard Schulte from LLUMC, “A status update on proton imaging for applications in medicine,” on October 30.
Like Roentgen’s x-ray image, the proton image of the hand phantom clearly shows details of the bone structure. Unlike x-rays, however, protons also show the soft tissue of the hand in more detail, which reflects differences in how the two forms of radiation interact with tissues. Whereas x-rays get absorbed preferentially by bones and show them much more clearly than the surrounding soft tissue, protons get slowed down or stopped by bone only 50 percent more than by soft tissue.
In addition to the progress in image reconstruction reported at the meeting, the researchers are developing innovations in detector technology that they will incorporate into future prototypes of the proton CT scanner.
Press release: Image of hand shows progress toward proton radiography