title: Improved MAGIC gel for higher sensitivity and elemental tissue equivalent 3D dosimetry.
abstract: OBJECTIVE
  Polymer-based gel dosimeter (MAGIC type) is a preferable phantom material for PET range verification of proton beam therapy. However, improvement in elemental tissue equivalency (specifically O/C ratio) is very desirable to ensure realistic time-activity measurements.
  
  
  METHODS
  Glucose and urea was added to the original MAGIC formulation to adjust the O/C ratio. The dose responses of the new formulations were tested with MRI transverse relaxation rate (R2) measurements.
  
  
  RESULTS
  The new ingredients improved not only the elemental composition but also the sensitivity of the MAGIC gel. The O/C ratios of our new gels agree with that of soft tissue within 1%. The slopes of dose response curves were 1.6-2.7 times larger with glucose. The melting point also increased by 5 degrees C. Further addition of urea resulted in a similar slope but with an increased intercept and a decreased melting point.
  
  
  CONCLUSIONS
  Our improved MAGIC gel formulations have higher sensitivity and better elemental tissue equivalency for 3D dosimetry applications involving nuclear reactions.
authors.affiliation: Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, USA. xzhu4@partners.org
authors.forename: Xuping
authors.initials: X
authors.lastname: Zhu
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Reese
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Crowley
authors.forename: Georges
authors.initials: G
authors.lastname: El Fakhri
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry* / Q000528:radiation effects*; D040761:Biomimetic Materials / Q000737:chemistry* / Q000528:radiation effects*; D019327:Copper Sulfate / Q000737:chemistry* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005780:Gelatin / Q000737:chemistry* / Q000528:radiation effects*; D006873:Hydroquinones / Q000737:chemistry* / Q000528:radiation effects*; D008689:Methacrylates / Q000737:chemistry* / Q000528:radiation effects*; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects*; D011522:Protons; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D006873:Hydroquinones; C476159:MAGIC polymer gel; D008689:Methacrylates; D011108:Polymers; D011522:Protons; D005780:Gelatin; D019327:Copper Sulfate; D001205:Ascorbic Acid