Technique – Induced Microtomy Artifacts

by | Dec 1, 2019 | LabStore Highlights | 0 comments

Histotechnology is often and appropriately referred to as an ‘Art & Science’. Art, because it requires skilled craftmanship in manual operations such as microtomy, mounting multiple sections/ribbons on slide, etc. Science because of the histochemistry involved in tissue fixation, processing, staining, etc. Historically, the ‘art’ of the profession preceded the science because it was such a hands-on craft that was taught via on-the-job training. It did not require much knowledge about the science to learn and master sectioning. Unfortunately, for years this hindered the Histology profession’s growth and acceptance in the medical community as a legitimate science the same as medical technology, cytotechnology, etc., because it was perceived as ‘only’ a craft. Interestingly, the craftmanship allowed the creativity of individual technique to be developed. Because there was a patient waiting for diagnosis, technicians did what they had to do to produce a diagnosable section. Addressing unforeseen variables such as over/under processed tissue could not be programmed into automation to circumvent problems; it required the skill and experience of the technologist to troubleshoot. Technicians learned how to develop tricks of the trade to address unforeseen issues and deliver a readable slide to the pathologist. During this learning process it was also revealed how the physical dynamics of the technique used could dramatically effect results. The image to the right demonstrates how abruptly slowing down the cutting speed in the middle of a section can produce a thick & thin section.

In microtomy it is difficult to define exactly what works and what doesn’t work for each individual technologist. They have all developed their own microtomy technique. This variability in technique oftentimes produces variability in results. Some technicians are inherently more proficient, faster, skilled, and successful than others. Particularly in high-volume environments such as hospital histopathology labs, speed and the urgency of a heavy block load can compromise optimal quality. Does the technician produce a ‘diagnosable’ section for the pathologist, …yes!!! Does the technique used frequently produce artifacts in that section that are induced by the technique used, …unfortunately, yes!!! Because the technician has delivered a diagnosable slide, oftentimes the artifact is never addressed. Further, the technique used that induced the artifact, can become a habitual part of the technician’s standard cutting style.
A common differential in microtomy technique from one person to another is cutting speed during block facing and sectioning. While countless technicians can produce good quality sections using a rapid machine-gun wheel rotation, it is a noted fact that this rapid nature does not necessarily cause artifacts, but it ‘can’ induce several artifacts. The images here demonstrate incidences of venetian blind effect, chatter, and washboarding; all caused by extremely rapid wheel rotation, and all eliminated by slowing down the stroke speed during final sectioning. As mentioned supervisor yelling at subordinate before, rapid wheel rotation does not necessarily ‘cause’ the artifact, but increases the probability of artifacts, particularly when dealing with factors such as overly dehydrated tissue, mild calcifications, block warming, etc. Also, rapid facing off or sectioning will decrease the life span of the blade area you are using. The blade facet is at its pinnacle a very fine delicate edge, which with repeated pounding and friction can cause premature nicks and abrasions on the edge (see knife facet at x5000 magnification) resulting in discrete, ‘angel hair’ knife marks in the tissue.
While factors such as loose knife or block holder and dull knife can cause an artifact such as thick/thin sections, inconsistency in final sectioning is also an area where the technician can affect the end result regardless of the blade. When technicians are taking their final ribbon at a consistent smooth slow rotation per section, but then abruptly stops and takes the next section at a half speed slower, this will typically cause the next section to be thicker as seen in the image to the right.

Even though there is a strong craftmanship component in microtomy, science is still a hidden major part of success in sectioning. Knife angle, a fresh blade, block temperature; all these are science related factors that must be blended in with craftmanship, however sometimes we rely too much on the craft. Technicians must always be cognizant of their cutting surface and how often to change blades. It is always better to err on playing it safe and change the blade more often than not. Technicians must always try to minimize the time that the block is in the chuck during sectioning, because it is warming up incrementally with each minute that passes. This warming up period progressively hinders the ability to get a smooth thin section. The longer the block is in the chuck, the thicker the sections will become off the knife. Caked up paraffin or debris on or behind the knife will affect your ability to produce consistently thin sections from ribbon to ribbon.

There are numerous factors that are out of our control that can hinder our ability to produce smooth, thin sections. Histology professionals more times than not have to take what’s given and create a diagnostic miracle on a slide. It is a credit to the Histologist that we are still able to provide this service to the pathologist and the patient, in spite of unforeseen challenges to the tissue. As professionals we must always check and monitor ourselves and the quality of work that we produce. Our efficiency in working through a caseload of blocks must never compromise our effectiveness in quality and doing our best to produce artifact-free results. All of the images shown in this article are still diagnosable slides, but it is important to note that all of the artifacts shown were technique-induced and could have been avoided with closer monitoring. Never stop caring about the work you produce.

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