San Jose State University College of Engineering Microtomes Brian Cheung Bernard Hwang David Yu.
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Transcript of San Jose State University College of Engineering Microtomes Brian Cheung Bernard Hwang David Yu.
![Page 1: San Jose State University College of Engineering Microtomes Brian Cheung Bernard Hwang David Yu.](https://reader035.fdocuments.net/reader035/viewer/2022062318/55182d46550346ac318b4ece/html5/thumbnails/1.jpg)
San Jose State University College of Engineering
Microtomes
Brian Cheung
Bernard Hwang
David Yu
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San Jose State University College of Engineering
Background
• The earliest form of microtomy was the freehand sectioning of fresh or fixed material using a sharp razor.
• The first microtome used were manual sectioning instruments made from wood, that were mainly used in Botany for cutting plants.
• Modern microtomes are precision instruments that cut uniformly thin sections of a variety of materials for microscopic examination.
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San Jose State University College of Engineering
Parts of a Microtome
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San Jose State University College of Engineering
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San Jose State University College of Engineering
Capabilities
• Standard microtomes are used to cut paraffin imbedded tissue specimens into thin plane sections.
• Sectioned material must be reproducible from only a fraction of a micron to a few microns thick. (Leitz 1512: 1 – 25m)
• Movements must be precisely controlled to ensure quality of the sectioned material.– Thickness– Reproducibility– Plane parallelism
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San Jose State University College of Engineering
Rotary Microtome Operation
• Insert paraffin-embedded sample into sample holder and release spring loaded clamp.
• Clamp blade into blade holder.
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San Jose State University College of Engineering
• Adjust blade holder angle and tighten
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San Jose State University College of Engineering
• Adjust thickness of sample section.
• Set counter dial to zero.
• Turn crank (one revolution per section).
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San Jose State University College of Engineering
• microtome pics\MVI_3845.AVI
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San Jose State University College of Engineering
Precision Engineering Applications
• Constraint of the Sample Block
• Constraint of the Knife Blade
• Microtome Knife Material Selection
• Translational Guide Rails
• Digital Volumetric Imaging
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San Jose State University College of Engineering
Constraint of the Sample Block• Embedded sample is held against a flat
surface and clamped down.– Semi-kinematic Constraint With A Line Contact
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San Jose State University College of Engineering
Constraint of the Knife Blade• Knife is placed in a retaining platform and secured rigidly
in place to the microtome by preloading the opposite side of the knife.
• If disposable knives are used, the knife is first held in a fixture; and the fixture is secured to the microtome.
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San Jose State University College of Engineering
Alternative Constraint Methods
• Newer microtomes may use additional methods to secure the blade.
– Additional Tightening Screws For Additional Point Contacts
– Knife Holder With Magnetic Retaining Points
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San Jose State University College of Engineering
Microtome Knife Material Selection
• Typical microtome blades are manufactured from high carbon steel or heat-treated tool grade steel.– Free From Impurities– Anti-corrosive And
Rust Resistant
• Profile of steel knives– A: Strongly Plano Concave– B: Plano Concave
– C: Wedge Shaped (Wedge Angle 27o)
– D: Plane Shaped (Wedge Angle 45o)
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San Jose State University College of Engineering
More on Microtome Knives
• Depending on the application other materials are available for blade:– Tungsten Carbide– Glass– Diamond– Sapphire– Disposable Blades
(Stainless Steel)
• Sharpening– Coarse sharpening– Fine sharpening– Stropping– Performed less with
the introduction of disposable knives
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San Jose State University College of Engineering
Translational Guide Rails• Guide rails with V-grooves
used to limit motion to1-DOF translation.
– Forward Knife Motion
– Vertical Raising And Lowering Of The Rigidly Held Sample
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San Jose State University College of Engineering
• Previous Sliding Guides Replaced With Rigid And Play-free Cross-roller Linear Bearings– Reduces Wear On The Grooves– Relieves Stress In Bearings– Support More Load With Increasing Contact Surface
• Roller bearings have less tendency to move out of position, or creep
Pictures From References 6 and 7
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San Jose State University College of Engineering
Digital Volumetric Imaging
Normally• Microtome → Slices → Microscope Slide → Microscope → Viewing or
Photography
Digital Volumetric Imaging (DVI)• Microtome → Slices → Digital Photography → Computer → 3-D Model
• Precision in Both a Microtome System and a Microscopic Imaging System
Picture From Reference 10
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San Jose State University College of Engineering
Examples of DVI Datasets
Pictures F
rom R
eference 10
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San Jose State University College of Engineering
Focus and Color Images
• CCD Chip → Grayscale Image
– Color Filters
• Capturing Images: Time-Dependent
• Illumination and Motors → Heat → Expansion → Focus Issues
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San Jose State University College of Engineering
Solution to Expansion of Block
1. Add Refrigeration System
2. Add Auto Focus System• Objective Lens on Piezo
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San Jose State University College of Engineering
More Precise Motion
• Higher Magnification Requires Thinner Sections.
• Cross Roller Bearings → Air Bearing Slide
• Stepper Motor & Linkages → Linear Motor
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San Jose State University College of Engineering
References1. Steedman, H.F.; Section Cutting in Microscopy; Blackwell Scientific Publications Ltd, Oxford;
England, 1960.
2. Leitz,Ernst; Leitz 1512/1516 rotary microtomes Instructions; Germany; 1984.
3. http://www.materials-sectioning.com
4. Woods and Ellis, Microtome: function and design http://home.primus.com.au/royellis/microt/microt.htm
5. http://biomicro.sdstate.edu/Hildrethm/Bio545/Techniques/Microtom.htm
6. http://www.schneeberger.com/
7. http://www.mellesgriot.com/glossary/wordlist/glossarydetails.asp?wID=136
8. http://www.theproductfinder.com/component/crorol.htm
9. Collins, Rodney; Personal Interview; San Francisco General Hospital, March 14, 2003
10. http://www.meyerinst.com/html/resolve3d/default.htm
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San Jose State University College of Engineering
Thank You Very Much!
Any Questions?