title: The development and validation of micro-CT of large deep frozen specimens.
abstract: Repetitive freeze/thaw cycles lead to a progressive loss of structural and molecular integrity in deep frozen specimens. The aim of this study was to evaluate a micro-CT stage, which maintains the cryoconservation of large specimens throughout micro-CT imaging. Deep frozen ovine vertebral segments (-20 °C) were fixed in a micro-CT stage made of expanded polystyrene and cooled with dry ice (0 g, 60 g and 120 g). The temperature inside the stage was measured half-hourly over a time span of three hours with subsequent measurement of surface temperature. The method was validated in a series of 30 deep frozen vertebral specimens and in liver tissue after repetitive micro-CT scanning. Isolation without cooling resulted in defrosting. Cooling with 60 g of dry ice led to a temperature rise inside the stage (max. 5.1 °C) and on the specimen surfaces (max. -3 °C). Cooling with 120 g of dry ice resulted in a significant (p < 0.001) and sufficient lowering of the temperature inside the stage (max. -14 °C) and on the surface of the specimens (max. -13.9 °C). The surface temperature during the subsequent micro-CT validation study did not exceed -16 °C (processing time 1 h 45 min). The resolution was 33 μm isotropic voxel side length, enabling a binarization of bone microstructures. Temperature can reliably be maintained below -10 °C during a micro-CT scan by applying the described technique. The resulting spatial resolution and image quality permits a binarization of bone microstructure.
authors: Department of Diagnostic and Interventional Radiology, University Hospital Giessen, Giessen, Germany; Laboratory of Experimental Radiology, Justus Liebig University Giessen, Giessen, Germany.
authors: Marian
authors: M
authors: Kampschulte
authors: Georg
authors: G
authors: Erdmann
authors: Jonas
authors: J
authors: Sender
authors: Gunhild
authors: G
authors: Martels
authors: Wolfgang
authors: W
authors: Böcker
authors: Thaqif
authors: T
authors: ElKhassawna
authors: Christian
authors: C
authors: Heiß
authors: Alexanders Claus
authors: AC
authors: Langheinrich
authors: Elke
authors: E
authors: Roeb
authors: Martin
authors: M
authors: Roderfeld
authors: Gabriele Anja
authors: GA
authors: Krombach
mesh_terms: D000818:Animals; D005615:Freezing; D008099:Liver / Q000000981:diagnostic imaging; D012756:Sheep; D013048:Specimen Handling / Q000379:methods*; D013131:Spine / Q000000981:diagnostic imaging*; D013696:Temperature; D055114:X-Ray Microtomography / Q000379:methods*
keywords: cryo-fixation; imaging; tomography