Proton computed tomography (pCT) is a new imaging technique that uses protons instead of photons to create images with improved accuracy over standard x-ray CT. pCT reduces radiation dose and range errors compared to x-ray CT, which is especially important for imaging near vital organs. The presented detector for pCT was built through collaboration and tracks proton trajectories using a fiber tracker and calculates residual energy using a scintillator stack to estimate proton path lengths and densities for improved treatment planning and delivery of proton therapy. Testing of the detector is ongoing to quantify the benefits of pCT compared to standard x-ray CT.

1. Proton Computed
Tomography
Nicole Hoffmann

2. Introduction
 Radiation therapy
◦ Common and effective
 Photons damage everything
◦ Detrimental to healthy tissue
 Dose plot and irradiation damages

3. Overview
 Proton therapy is a popular and
effective treatment option
◦ Maximize radiation dose to tumor
◦ Minimize radiation dose to healthy tissue
 How do we make this process better?
 First center in Loma Linda, CA, 1990
 Worked with Dr. Zutshi

4. Background
 Why would anyone use pCT?
 X-ray CT uses photons, causing 3 to 5
percent range errors
 More dangerous near vital organs
 Potential pCT benefits
◦ Fewer range errors by using same
particle
◦ Planning and treatment with protons

5. Methods
 Protons are charged
 Multiple Coulomb Scattering
 Calculations
◦ Trajectory (fiber tracker)
◦ Residual energy (scintillator stack)
◦ Estimation of path length and density
The detector was built as a collaboration between
Delhi, Fermilab, and NIU.

6. Fiber Tracker and Scintillator Stack

7. SiPMs
 Silicon photomultipliers
◦ Protons pass through fibers
◦ Each pixel operates as a digital device
◦ Scintillation light
◦ Converts photons to current
◦ Analog output

8. Single Photo Electron Spectrum

9. Detector

10. Methods
 Performance plots
 Approximation of proton path
◦ MCS and trajectories
◦ Most likely path algorithm
◦ Shows error
◦ Calculated with residual energies
B. Erdelyi

11. Results
 Detector is finished
 Undergoing testing to confirm pCT
benefits
 Compare to X-Ray CT
◦ Accuracy
◦ Non-medical applications
◦ Not affected by implants
◦ Less radiation during scan

12. Conclusions
 Significance
◦ Changes cancer treatment
◦ Less detrimental to patient health
 Compared to X-Ray CT
◦ Benefits are being investigated

13. Future Directions
 Where do we go next?
◦ Confirm positive benefits of pCT
◦ Further improve the detector
◦ Commercialize for clinical settings

14. Acknowledgments
 Warrenville Proton Center
 Department of Defense
 Research Rookies
 University of Delhi
 Fermilab