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Practical aspects of in situ 16O (gamma,n) 15O activation using a conventional medical accelerator for the purpose of perfusion imaging.

Publication ,  Journal Article
Oldham, M; Sapareto, SA; Li, XA; Allen, J; Sutlief, S; Wong, OC; Wong, JW
Published in: Med Phys
August 2001

We report investigations into the feasibility of generating radioactive oxygen (15O, a positron emitter, with half-life 2.05 min) using a tuned Elekta SL25 accelerator, for the end purpose of imaging tumor perfusion. 15O is produced by the "gamma, neutron," (gamma,n) reaction between high-energy photons and normal oxygen (16O) in the body. As most in vivo 16O is bound in water molecules the 15O radio-marker is produced in proportion to water content in tissue. Imaging the washout of the 15O distribution using sensitive positron-emission-tomography (PET) technology can yield spatial information about blood perfusion in the tissue. The aim of this article was to determine the amount of 15O activity that could be produced by the tuned medical accelerator. A further aim was to model the activation process using Monte Carlo and to investigate ways to optimize the amount of 15O that could be generated. Increased activation was achieved by (i) tuning the beam to give higher-energy electrons incident on the target of the accelerator, (ii) increasing dose rate by removing the conventional filtration in the beam and reducing the source to object distance, and (iii) reducing low-energy photons by means of a carbon block absorber. The activity per-unit-dose produced by the tuned beam was measured by irradiating spheres of water to known doses and placing the spheres in a calibrated coincidence-counting apparatus. Peak energy of the tuned bremsstrahlung beam was estimated at 29 MeV, and generated activity up to 0.24/microCi/cc/3Gy in water. The measured amount of 15O agreed to within 10% of the prediction from the Monte-Carlo-computed spectrum, indicating reasonable ability to model the activation process. The optimal thickness of the carbon absorber was found to be about 25 cm. The insertion of a carbon absorber improved spectral quality for activation purposes but at the cost of reduced dose rate. In conclusion, the viability of generating 15O with an Elekta SL25 has been demonstrated. In conjunction with recent advances in high-sensitivity portable PET imaging devices, real potential exists for imaging in situ activated 15O washout as a surrogate measurement of macroscopic tumor perfusion.

Duke Scholars

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Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

August 2001

Volume

28

Issue

8

Start / End Page

1669 / 1678

Location

United States

Related Subject Headings

  • Time Factors
  • Photons
  • Perfusion
  • Particle Accelerators
  • Oxygen Radioisotopes
  • Oxygen
  • Nuclear Medicine & Medical Imaging
  • Neutrons
  • Monte Carlo Method
  • Light
 

Citation

APA
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ICMJE
MLA
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Oldham, M., Sapareto, S. A., Li, X. A., Allen, J., Sutlief, S., Wong, O. C., & Wong, J. W. (2001). Practical aspects of in situ 16O (gamma,n) 15O activation using a conventional medical accelerator for the purpose of perfusion imaging. Med Phys, 28(8), 1669–1678. https://doi.org/10.1118/1.1386777
Oldham, M., S. A. Sapareto, X. A. Li, J. Allen, S. Sutlief, O. C. Wong, and J. W. Wong. “Practical aspects of in situ 16O (gamma,n) 15O activation using a conventional medical accelerator for the purpose of perfusion imaging.Med Phys 28, no. 8 (August 2001): 1669–78. https://doi.org/10.1118/1.1386777.
Oldham M, Sapareto SA, Li XA, Allen J, Sutlief S, Wong OC, et al. Practical aspects of in situ 16O (gamma,n) 15O activation using a conventional medical accelerator for the purpose of perfusion imaging. Med Phys. 2001 Aug;28(8):1669–78.
Oldham, M., et al. “Practical aspects of in situ 16O (gamma,n) 15O activation using a conventional medical accelerator for the purpose of perfusion imaging.Med Phys, vol. 28, no. 8, Aug. 2001, pp. 1669–78. Pubmed, doi:10.1118/1.1386777.
Oldham M, Sapareto SA, Li XA, Allen J, Sutlief S, Wong OC, Wong JW. Practical aspects of in situ 16O (gamma,n) 15O activation using a conventional medical accelerator for the purpose of perfusion imaging. Med Phys. 2001 Aug;28(8):1669–1678.

Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

August 2001

Volume

28

Issue

8

Start / End Page

1669 / 1678

Location

United States

Related Subject Headings

  • Time Factors
  • Photons
  • Perfusion
  • Particle Accelerators
  • Oxygen Radioisotopes
  • Oxygen
  • Nuclear Medicine & Medical Imaging
  • Neutrons
  • Monte Carlo Method
  • Light