title: Mapping (15)O production rate for proton therapy verification.
abstract: OBJECTIVE
  This work was a proof-of-principle study for the evaluation of oxygen-15 ((15)O) production as an imaging target through the use of positron emission tomography (PET), to improve verification of proton treatment plans and to study the effects of perfusion.
  
  
  METHODS
  Dynamic PET measurements of irradiation-produced isotopes were made for a phantom and rabbit thigh muscles. The rabbit muscle was irradiated and imaged under both live and dead conditions. A differential equation was fitted to phantom and in vivo data, yielding estimates of (15)O production and clearance rates, which were compared to live versus dead rates for the rabbit and to Monte Carlo predictions.
  
  
  RESULTS
  PET clearance rates agreed with decay constants of the dominant radionuclide species in 3 different phantom materials. In 2 oxygen-rich materials, the ratio of (15)O production rates agreed with the expected ratio. In the dead rabbit thighs, the dynamic PET concentration histories were accurately described using (15)O decay constant, whereas the live thigh activity decayed faster. Most importantly, the (15)O production rates agreed within 2% (P>.5) between conditions.
  
  
  CONCLUSIONS
  We developed a new method for quantitative measurement of (15)O production and clearance rates in the period immediately following proton therapy. Measurements in the phantom and rabbits were well described in terms of (15)O production and clearance rates, plus a correction for other isotopes. These proof-of-principle results support the feasibility of detailed verification of proton therapy treatment delivery. In addition, (15)O clearance rates may be useful in monitoring permeability changes due to therapy.
authors: Center for Advanced Radiological Sciences, Nuclear Medicine and Molecular Imaging, Radiology Department, Massachusetts General Hospital, Boston, Massachusetts.
authors: Kira
authors: K
authors: Grogg
authors: Center for Advanced Radiological Sciences, Nuclear Medicine and Molecular Imaging, Radiology Department, Massachusetts General Hospital, Boston, Massachusetts.
authors: Nathaniel M
authors: NM
authors: Alpert
authors: Center for Advanced Radiological Sciences, Nuclear Medicine and Molecular Imaging, Radiology Department, Massachusetts General Hospital, Boston, Massachusetts.
authors: Xuping
authors: X
authors: Zhu
authors: Department of Radiological Science, College of Health Science, Yonsei University, Wonju, Kangwon, Korea.
authors: Chul Hee
authors: CH
authors: Min
authors: Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors: Mauro
authors: M
authors: Testa
authors: Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors: Brian
authors: B
authors: Winey
authors: Center for Advanced Radiological Sciences, Nuclear Medicine and Molecular Imaging, Radiology Department, Massachusetts General Hospital, Boston, Massachusetts.
authors: Marc D
authors: MD
authors: Normandin
authors: Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors: Helen A
authors: HA
authors: Shih
authors: Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors: Harald
authors: H
authors: Paganetti
authors: Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors: Thomas
authors: T
authors: Bortfeld
authors: Center for Advanced Radiological Sciences, Nuclear Medicine and Molecular Imaging, Radiology Department, Massachusetts General Hospital, Boston, Massachusetts. Electronic address: elfakhri@pet.mgh.harvard.edu.
authors: Georges
authors: G
authors: El Fakhri
mesh_terms: D000818:Animals; D001669:Biochemical Phenomena; D005240:Feasibility Studies; D009010:Monte Carlo Method; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000528:radiation effects; D010104:Oxygen Radioisotopes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D010539:Permeability; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D061766:Proton Therapy / Q000295:instrumentation; D011817:Rabbits; D013848:Thigh; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D010104:Oxygen Radioisotopes