PET Imaging of Proton Therapy Harvard Medical School

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PET Imaging of Proton Therapy Harvard Medical School Massachusetts General Hospital

PET Imaging of Proton Therapy Harvard Medical School Massachusetts General Hospital

Proton vs photon therapy Finite range implies reduced integral dose, better conformality Figure from

Proton vs photon therapy Finite range implies reduced integral dose, better conformality Figure from Wikipedia, http: //en. wikipedia. org/wiki/File: Bragg. Peak. png

Finite range drawbacks Uncertainty in range has higher consequences Tumor Critical structure Ideal treatment

Finite range drawbacks Uncertainty in range has higher consequences Tumor Critical structure Ideal treatment Potential actual treatment Beam Dose to critical structure

Drawbacks of Finite Range Uncertainty in range has higher consequences Tumor Critical structure Ideal

Drawbacks of Finite Range Uncertainty in range has higher consequences Tumor Critical structure Ideal treatment Potential actual treatment More robust plan Beam Dose to critical structure Patched Beams

Patched Beam Treatment Plan

Patched Beam Treatment Plan

Improving Proton Therapy with PET In proton therapy, the dose stops within the patient

Improving Proton Therapy with PET In proton therapy, the dose stops within the patient Protons occasionally interact with nuclei and create a small amount of radioactivity PET makes it possible to “see” where some of the radioactive particles were made Good for avoiding dose to sensitive areas Bad for verifying dose delivery Detects gamma rays emitted when positrons from the decaying nucleus annihilate with native electrons Provides 3 D images of the radioactivity that can be related to the dose through various means of analysis Any discrepancies between the measured PET activity and what is expected can be used to improve therapy

Proton from cyclotron patient’s tumor Createsbeam radioactive isotopessent thatto can be imaged

Proton from cyclotron patient’s tumor Createsbeam radioactive isotopessent thatto can be imaged

Use of PET for verification of proton therapy DOSE PET - PET

Use of PET for verification of proton therapy DOSE PET - PET

PET Signal from Protons Positron emitters are produced from nuclear interactions of protons and

PET Signal from Protons Positron emitters are produced from nuclear interactions of protons and nuclei PET cameras detect the photons emitted from the annihilation of the positron and an electron Proton Neutron Positron Electron Photon

Improving Proton Therapy with PET makes it possible to “see” the location of the

Improving Proton Therapy with PET makes it possible to “see” the location of the radioactive particles and thus where therapeutic protons were delivered Provides 3 D images of the radioactivity that can be related to the dose through various means of analysis e. g. , compare PET images with simulations of the expected PET image Planned dose PET image Simulated image Any discrepancies between the measured PET activity and what is expected can be used to improve therapy

Current status PET monitoring of proton therapy is in the research stage Scanning phantoms

Current status PET monitoring of proton therapy is in the research stage Scanning phantoms and patients after irradiation to verify analysis techniques Routine use of PET to monitor and modify proton therapy at MGH has not yet been established PET has been used at other institutions to successfully alter treatment plans PET for proton therapy was first proposed in the early 90 s Gradually getting better results as PET cameras improve Found to be most successful in rigid and bony locations such as the head and the spine Most critical when the tumor is near a sensitive structure PET studies so far have found a precision of several millimeters Would like to reduce the uncertainty to one millimeter

Neuro. PET from Photo. Detection Systems The first mobile PET scanner that you can

Neuro. PET from Photo. Detection Systems The first mobile PET scanner that you can plug and play! Currently being used in patient studies at MGH

PET scanning procedure The patient is treated according to their treatment plan As soon

PET scanning procedure The patient is treated according to their treatment plan As soon as the beam stops, the mobile Neuro. PET scanner is wheeled into the room, while the patient’s bed is repositioned to move into the bore of the scanner There is no need to move the patient with this technique The patient’s head is positioned into the scanner and remains there for 20 minutes At MGH only patients with head treatments are being scanned In routine use the scan time can be reduced to 5 minutes The PET data is reconstructed into 3 D images that can be compared to the planned dose and/or to Monte Carlo simulations of the expected PET image

Using In-room Neuro. PET for proton therapy verification Patient treated with proton beam pt

Using In-room Neuro. PET for proton therapy verification Patient treated with proton beam pt s ro on Patient imaged with PET scanner PET • The patient is treated according to the prescribed treatment plan • Proton beam is on for 30 -90 seconds • Patient is moved into PET scanner while still on the treatment bed • Positioning takes 1 -2 minutes • Patient is scanned for 20 minutes • Can be reduced to 5 minutes for routine use • 3 D images are reconstructed and compared to simulations

Patient being scanned after proton therapy

Patient being scanned after proton therapy

Comparison of Measured PET and Simulated PET Patient’s PET scan Reconstructi on In-room PET

Comparison of Measured PET and Simulated PET Patient’s PET scan Reconstructi on In-room PET 3 D OSEM PET+CT List mode raw data Measured PET In-room PET scan just after irradiation Comparison Monte Carlo Simulation Geant 4 Fluence Cross Sections Dose and PET calculation with nozzle and CT 11 C 15 O MATLAB Decay Washout Blurrring Normalization Simulated PET

Reconstructed PET Images and Simulated Results Nasal cavity Orbit Brain Treatment planned dose Simulated

Reconstructed PET Images and Simulated Results Nasal cavity Orbit Brain Treatment planned dose Simulated PET Measured PET

Improvements Incorporate CT scanner into mobile Neuro. PET Already done, will soon be scanning

Improvements Incorporate CT scanner into mobile Neuro. PET Already done, will soon be scanning patients at MGH Better modeling of the signal loss from biological effects Studying a promising new algorithm Faster simulations of PET activity Determination of dose directly from PET image

Next Generation: Mobile Neuro. PET/CT Includes CT scanner for improved attenuation correction and anatomical

Next Generation: Mobile Neuro. PET/CT Includes CT scanner for improved attenuation correction and anatomical registration Soon to be employed for scanning proton therapy patients at MGH