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Development of process parameters for the stereolithography
Vítek, Jan ; Škaroupka, David (referee) ; Paloušek, David (advisor)
This bachelor thesis deals with the search for optimal process parameters to reach a high strength of the Detax Solflex model material, with the DLP (digital light processing) 3D Solflex 650 printer. In the first part of this thesis the principle of printing using a laser and using a DLP projector and their comparison are presented. Further information about materials and impact of the process parameters on a printing are discussed. Based on a knowledge two assumptions were set: influence of exposure time and influence of layer thickness on strength. Firstly, samples were tested by the hardness Shore D test and the results from the test were compared. New samples for the stress test with the optimal set of parameters given by the previous test were printed and tested. Process parameters influence on strength was determined from the achieved results.
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Development of process parameters for the stereolithography
Vítek, Jan ; Škaroupka, David (referee) ; Paloušek, David (advisor)
This bachelor thesis deals with the search for optimal process parameters to reach a high strength of the Detax Solflex model material, with the DLP (digital light processing) 3D Solflex 650 printer. In the first part of this thesis the principle of printing using a laser and using a DLP projector and their comparison are presented. Further information about materials and impact of the process parameters on a printing are discussed. Based on a knowledge two assumptions were set: influence of exposure time and influence of layer thickness on strength. Firstly, samples were tested by the hardness Shore D test and the results from the test were compared. New samples for the stress test with the optimal set of parameters given by the previous test were printed and tested. Process parameters influence on strength was determined from the achieved results.
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Reduction of radiation exposure by the use of the fluoroscopic spinal navigation system during the transpedicular screw placement of the lumbal spine.
ŠRŮTKOVÁ, Eva
RADIATION EXPOSURE REDUCTION BY THE USE OF FLUOROSCOPIC NAVIGATION IN TRANSPEDICULAR INSTRUMENTATION OF THE LUMBAR SPINE SUMMARY The topic of this thesis is a comparison of radiation exposure during standard fluoroscopy and navigated transpedicular instrumentation of the lumbar spine, in compliance with standard techniques and accuracy of screw placement. Material and the Method: A group of 60 patients, divided into two equal groups, was statistically processed. In the first group 1.9 lumbar spine segments were stabilized. The patients´ average age was 60.8 years (from 35 to 75 years). Screws were inserted transpedicularly under the X-ray image intensifier navigation. In the second group stabilization of 1.8 segments was performed on average. The average age was 61.1 years (from 38 to 75 years). The screws were inserted postoperatively by using 2D fluoroscopic navigation technique (VectorVision, BrainLAB, Germany). The duration of skiascopy was collected from the X-ray image intensifier and recorded for each surgery (with navigation and without). The measured values were compared with each other. In both groups the screw positioning was checked continuously according to the rules defined by Learch, Acikbas and Whitecloud in the anteroposterior and lateral projection by meticulous pedicle palpation Results: The radiation exposure was calculated to one vertebra (2 screws) in both groups. In the second (navigated) group the radiation exposure time was significantly shorter (3.4 s) than in the first (standard) group (14.4 s). The mean duration of data registration was 6.0 minutes (range 3 to 11 minutes). The mean ratio according to Acikbas's calculation method was 43.2 % (range 32 % to 74 %) in the first group and 44.1% (range 35% - 76%) in the second group. The mean exposure dose of the first group was 243 ?G/m2 and 138 ?G/m2 in the second group. Exposition doses are smaller by 105 ?G/m2 in the second group Conclusion: Based on the results, the hypothesis that navigation allows the same accuracy of pedicle screws insertion while reducing radiation exposure of the patients and the operating room staff to about ? can be confirmed. This reduction is more pronounced in multiple-level spinal stabilizations and in the centers for spinal surgeries, where numerous spinal instrumentations are performed every day.
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