title: Feasibility of magnetic resonance imaging-guided liver stereotactic body radiation therapy: A comparison between modulated tri-cobalt-60 teletherapy and linear accelerator-based intensity modulated radiation therapy.
abstract: OBJECTIVE
  The purpose of this study was to investigate the dosimetric feasibility of liver stereotactic body radiation therapy (SBRT) using a teletherapy system equipped with 3 rotating (60)Co sources (tri-(60)Co system) and a built-in magnetic resonance imager (MRI). We hypothesized tumor size and location would be predictive of favorable dosimetry with tri-(60)Co SBRT.
  
  
  METHODS
  The primary study population consisted of 11 patients treated with SBRT for malignant hepatic lesions whose linear accelerator (LINAC)-based SBRT plans met all mandatory Radiation Therapy Oncology Group (RTOG) 1112 organ-at-risk (OAR) constraints. The secondary study population included 5 additional patients whose plans did not meet the mandatory constraints. Patients received 36 to 60 Gy in 3 to 5 fractions. Tri-(60)Co system SBRT plans were planned with ViewRay system software.
  
  
  RESULTS
  All patients in the primary study population had tri-(60)Co SBRT plans that passed all RTOG constraints, with similar planning target volume coverage and OAR doses to LINAC plans. Mean liver doses and V10Gy to the liver, although easily meeting RTOG 1112 guidelines, were significantly higher with tri-(60)Co plans. When the 5 additional patients were included in a univariate analysis, the tri-(60)Co SBRT plans were still equally able to pass RTOG constraints, although they did have inferior ability to pass more stringent liver and kidney constraints (P < .05). A multivariate analysis found the ability of a tri-(60)Co SBRT plan to meet these constraints depended on lesion location and size. Patients with smaller or more peripheral lesions (as defined by distance from the aorta, chest wall, liver dome, and relative lesion volume) were significantly more likely to have tri-(60)Co plans that spared the liver and kidney as well as LINAC plans did (P < .05).
  
  
  CONCLUSIONS
  It is dosimetrically feasible to perform liver SBRT with a tri-(60)Co system with a built-in MRI. Patients with smaller or more peripheral lesions are more likely to have optimal liver and kidney sparing, with the added benefit of MRI guidance, when receiving tri-(60)Co-based SBRT.
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Amar U
authors.initials: AU
authors.lastname: Kishan
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Minsong
authors.initials: M
authors.lastname: Cao
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Pin-Chieh
authors.initials: PC
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Argin G
authors.initials: AG
authors.lastname: Mikaeilian
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Stephen
authors.initials: S
authors.lastname: Tenn
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Jean-Claude M
authors.initials: JM
authors.lastname: Rwigema
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Ke
authors.initials: K
authors.lastname: Sheng
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Low
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Kupelian
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Steinberg
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California. Electronic address: PercyLee@mednet.ucla.edu.
authors.forename: Percy
authors.initials: P
authors.lastname: Lee
mesh_terms: D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010315:Particle Accelerators; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*