title: [Elastic modulus measured by spherical indentation used toward the clinical application of the brain stiffness].
abstract: OBJECTIVE
  Palpation of brain stiffness is one of techniques that leads to successful neurosurgical procedures. In order to evaluate brain stiffness quantitatively, we studied the potential clinical applicability of a spherical indenting tactile sensor.
  
  
  METHODS
  The sensor had a spherical rigid indenter (diameter=5.0 mm; contact pressure=1.0 gf/mm2), and the indenter was rapidly pushed and pulled at a constant speed by a computer-controlled motor. The pressure-depth hysteresis curve was obtained using the sensor, and the shear elastic modulus (G) was calculated on the basis of the Hertz contact theory. We adopted the G-value at the maximum depth (G_max) as an indicator of brain stiffness.
  
  
  RESULTS
  First, to calibrate the sensor, we investigated the elasticity of silicone plates. The optimal settings for clinical application was an indenting speed of 1.5 mm/s and an indenting maximum depth of 2-3 mm. Next, we measured the elasticity of a decompressive site in 7 patients who had been stable for more than 21 days after undergoing decompressive craniectomy. The G_max of the decompressive site was 1.71 ± 0.75 kPa. Finally, we measured the intraoperative brain elasticity in a case of brain tumor with severe brain edema. The transdural elasticity of the edematous brain was G=4.87 kPa, and the direct elasticity of the brain surface decreased to G=4.34 kPa after dura incision.
  
  
  CONCLUSIONS
  The spherical indentation method for measuring brain elasticity seems applicable to neurosurgical procedures.
authors.affiliation: Department of Neurosurgery, Shimane University Faculty of Medicine, Japan.
authors.forename: Hidemasa
authors.initials: H
authors.lastname: Nagai
authors.forename: Daikei
authors.initials: D
authors.lastname: Takada
authors.forename: Mizuki
authors.initials: M
authors.lastname: Kambara
authors.forename: Shinya
authors.initials: S
authors.lastname: Hagiwara
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Daisu
authors.forename: Takeshi
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Akiyama
mesh_terms: D000368:Aged; D001932:Brain Neoplasms / Q000601:surgery; D055119:Elastic Modulus / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D019635:Neurosurgical Procedures / Q000379:methods; D010173:Palpation / Q000009:adverse effects; D011312:Pressure / Q000009:adverse effects