title: Preclinical evaluation of bioabsorbable polyglycolic acid spacer for particle therapy.
abstract: OBJECTIVE
  To evaluate the efficacy and safety of a polyglycolic acid (PGA) spacer through physical and animal experiments.
  
  
  METHODS
  The spacer was produced with surgical suture material made of PGA, forming a 3-dimensional nonwoven fabric. For evaluation or physical experiments, 150-MeV proton or 320-MeV carbon-ion beams were used to generate 60-mm width of spread-out Bragg peak. For animal experiments, the abdomens of C57BL/6 mice, with or without the inserted PGA spacers, were irradiated with 20 Gy of carbon-ion beam (290 MeV) using the spread-out Bragg peak. Body weight changes over time were scored, and radiation damage to the intestine was investigated using hematoxylin and eosin stain. Blood samples were also evaluated 24 days after the irradiation. Long-term thickness retention and safety were evaluated using crab-eating macaques.
  
  
  RESULTS
  No chemical or structural changes after 100 Gy of proton or carbon-ion irradiation were observed in the PGA spacer. Water equivalency of the PGA spacer was equal to the water thickness under wet condition. During 24 days' observation after 20 Gy of carbon-ion irradiation, the body weights of mice with the PGA spacer were relatively unchanged, whereas significant weight loss was observed in those mice without the PGA spacer (P<.05). In mice with the PGA spacer, villus and crypt structure were preserved after irradiation. No inflammatory reactions or liver or renal dysfunctions due to placement of the PGA spacer were observed. In the abdomen of crab-eating macaques, thickness of the PGA spacer was maintained 8 weeks after placement.
  
  
  CONCLUSIONS
  The absorbable PGA spacer had water-equivalent, bio-compatible, and thickness-retaining properties. Although further evaluation is warranted in a clinical setting, the PGA spacer may be effective to stop proton or carbon-ion beams and to separate normal tissues from the radiation field.
authors.affiliation: Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Akasaka
authors.affiliation: Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan. Electronic address: rsasaki@med.kobe-u.ac.jp.
authors.forename: Ryohei
authors.initials: R
authors.lastname: Sasaki
authors.affiliation: Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Miyawaki
authors.affiliation: Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan.
authors.forename: Naritoshi
authors.initials: N
authors.lastname: Mukumoto
authors.affiliation: Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan.
authors.forename: Nor Shazrina Binti
authors.initials: NS
authors.lastname: Sulaiman
authors.affiliation: Division of Gastroenterology, Kobe University Graduate School of Medicine, Hyogo Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nagata
authors.affiliation: Research Center Hospital, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamada
authors.affiliation: Radiation Oncology Center, Dokkyo Medical University, Tochigi, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Murakami
authors.affiliation: Department of Radiology, Hyogo Ion Beam Medical Center, Hyogo, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Demizu
authors.affiliation: Division of Hepato-Biliary-Pancreatic Surgery, Kobe University Graduate School of Medicine, Hyogo Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Fukumoto
mesh_terms: D020341:Absorbable Implants / Q000009:adverse effects; D000818:Animals; D001835:Body Weight / Q000528:radiation effects*; D002244:Carbon; D063193:Heavy Ion Radiotherapy / Q000009:adverse effects; D007422:Intestines / Q000528:radiation effects*; D008252:Macaca fascicularis; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008810:Mice, Inbred C57BL; D008970:Molecular Weight; D058958:Organs at Risk / Q000528:radiation effects*; D011100:Polyglycolic Acid / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects*; D061766:Proton Therapy; D011829:Radiation Dosage; D011833:Radiation Injuries, Experimental / Q000517:prevention & control*; D012062:Relative Biological Effectiveness; D014783:Viscosity / Q000528:radiation effects; D015431:Weight Loss
chemical_list: D011100:Polyglycolic Acid; D002244:Carbon