How is microtomy alignment achieved?
There are two methods of microtome alignment- using a microtome alignment tool or using blank blocks for alignment.
Microtome Alignment Tool
How does the microtomy alignment tool work? It is placed into the cassette clamp. There is a bubble in the center. When the bubble is in the center of the black circles, then the microtome is aligned. The cassette clamp can be adjusted by knobs on the microtome. There is a lever on the microtome which must be loosened before the alignment knobs can be adjusted. One knob adjusts the x-axis, while the other knob adjusts the y-axis. After the microtome is aligned, the lever must be locked in place. The equipment manual for the model microtome in your lab can be read for exact instruction on knob adjustment for cassette clamp adjustment. A universal microtome alignment tool should be able to be used for any microtome in the lab. Microtome alignment tools can be purchased online from various vendors for as little as $225.00.
Another method utilized for the alignment of microtomes to each other are blank blocks. A blank block, a block with paraffin only poured into mold and a cassette atop should be prepared for each microtome in the lab which you wish to align. In my lab, we used the large rectangular shape molds. Make sure that the blank blocks are straight. I did not use a level for this part of the process, I just checked the blocks to make sure that the paraffin was even on all sides. Start with a microtome which is in alignment. If you put a blank block in it , it should cut an even slice of paraffin. When you start to align microtomes which are not aligned, you can look at how the block is being cut to see where the microtome is out of alignment. It may cut too much from either the left or right sides of the block in which case the x-axis need to be adjusted. Adjust the knobs to correct the alignment, cut more from the block. An aligned microtome will cut evenly from the blank block. This method might require additional time, but it is less expensive.
How often should microtome alignment be conducted in the lab?
There isn’t a set number of times or length of time between alignments. The truth is you can perform the alignment as often as you need to in the lab. In my experience you typically need to perform the alignment a couple times a year. The effort will increase your efficiency and minimize tissue loss while cutting.
Written by: Aubrey Paul, MS