1. Proton beam range verification using proton activated fiducials and off-site PET AAPM Best in Physics, Indianapolis, August 7, 2013
Cho J1, Ibbott G1, Gillin M1, Gonzalez-Lepera C2, Titt U1, and Mawlawi O3.
Departments of 1 Radiation Physics, 2 Nuclear Medicine and 3 Imaging Physics
University of Texas MD Anderson Cancer Center, Houston, TX
PET imaging for proton therapy verification.
Please interrupt me anytime for questions.

2. Outline Background Purpose Measurements Future application
Use of PET for proton range verification and its limitations
Purpose
Proton activated fiducial markers for range verification
Measurements
Activation comparison of 68Zn, Cu, and tissue- substitute materials
Future application

3. Proton range uncertainty

4. Proton range verification by imaging tissue activation
Dose
Proton
Tissue activation
Limitations
No or weak PET signal
at the end of proton range
PET
Min et al, IJROBP 2013
PET
Activity washout
Short half-lives
→ Requires in-beam or
on-site PET (additional cost !)
Parodi et al, NIH public access 2007

5. Purpose: 68Zn and 63Cu as implantable markers
Overcome limitations by
High PET signal
at the end of proton range
Activated marker
No activity washout
Not activated
marker
Relatively long half-lives
→ Off-site PET utilized (already available !)

6. 68Zn and Cu(70% 63Cu) activation (no background)
30 min PET scan after 50 min delay
12.5 Gy

7. 68Zn and Cu activation (with background)
30 min PET scan
after 48 min delay
Signal reduced

8. 68Zn and Cu activation in soft-tissue phantom
126 min delay,
30 min PET scan

9. 68Zn and Cu activation in soft-tissue phantom
Proton
Range ???
Proton
Range YES!

10. Limitation Point verification vs. Volume verification Invasive
Fiducial migration
Sensitivity (signal vs. fiducial volume)
PET

11. Conclusion
68Zn / Cu foils were activated much stronger and at deeper depths than PC.
68Zn / Cu foils’ activation were stronger than background activation from balsa wood and meat phantom.
68Zn / Cu may be feasible as implantable fiducial markers for proton range verification.

12. Future application as a fiducial replacement
Proton activated
fiducial
Non-activated
fiducial

13. Thank you.
Acknowledgement Reinhard Schulte at Loma Linda University Medical Center. Pablo Yepes at Rice University. Wen Hsi at ProCure Treatment Center. Francesco Stingo Lawrence Bronk Bryan Steward Kevin Casey Kevin Vredevoogd Richard Amos Matthew Kerr at UT MD Anderson Cancer Center.

14. 68Zn and Cu activation with depth
12.5 Gy
50 min delay,
150 min PET scan

15. Sensitivity of 68Zn and Cu for different volumes

17. Purpose: 68Zn and 63Cu as implantable markers
Overcome limitations by
High PET signal
at the end of proton range
Activated marker
No activity washout
Not activated
marker
Relatively long half-lives
→ Off-site PET utilized (already available !)