Proton range verification with PET: 68Zn, Cu and polycarbonate activation SNMMI Young Investigator Symposium, Vancouver, June 9, 2013 Cho J1, Ibbott G1, Gillin M1, Gonzalez-Lepera C2, and Mawlawi O3. 1 Department of Radiation Physics 2 Department of Nuclear Medicine 3 Department of Imaging Physics University of Texas MD Anderson Cancer Center, Houston, TX PET imaging for proton therapy verification. Please interrupt me anytime for questions.

Outline Background Purpose Measurements Future application Proton therapy Use of PET for proton range verification Current limitations Purpose Proton activated fiducial markers for range verification Measurements Activation comparison of 68Zn, Cu and polycarbonate Future application

X-ray therapy vs. Proton therapy high dose low dose low dose high dose Dose (%) Proton X-ray Depth (cm)

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

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 !)

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

68Zn and Cu activation (with background) 30 min PET scan after 48 min delay 50 mm3 5 Gy Signal reduced

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

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. 68Zn / Cu may be feasible as implantable fiducial markers for proton range verification.

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

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

68Zn and Cu activation in meat phantom 126 min delay, 30 min PET scan 5 Gy

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

Sensitivity of 68Zn and Cu for different volumes

X-ray therapy vs. Proton therapy Healthy tissue Tumor Critical organ

X-ray therapy vs. Proton therapy Healthy tissue Tumor Critical organ

X-ray therapy vs. Proton therapy

Proton therapy verification using PET Incident proton beam Nucleus in patient patient Parodi et al, NIH public access 2007