What are Processing Artifacts?
Processing artifacts are unintended alterations in tissue samples that occur during the preparation stages for histological examination. These artifacts can obscure or mimic pathological features, leading to potential misinterpretations. Understanding and identifying these artifacts are crucial for accurate
histological analysis.
Common Types of Processing Artifacts
There are several types of artifacts that can arise during tissue processing. Some of the most common include:Fixation Artifacts
Fixation is crucial for preserving tissue morphology and preventing degradation. However, improper fixation can introduce artifacts such as shrinkage, swelling, and hardening of tissues. Common fixation artifacts include:
Shrinkage: This occurs when tissues lose water and collapse, often due to over-fixation or the use of harsh fixatives like formalin.
Swelling: Overhydration during fixation can cause tissues to swell, leading to distorted morphology.
Hardening: Excessive fixation can harden tissues, making them difficult to section.
Sectioning Artifacts
During
microtomy, thin sections of tissue are cut using a microtome. This step can introduce artifacts such as:
Knife Marks: Visible lines caused by a dull or damaged microtome blade.
Compression: Tissues may appear compressed due to improper sectioning speed or blade angle.
Wrinkles: Folding or wrinkling of tissue sections, often due to insufficient flattening on the water bath.
Staining Artifacts
Staining enhances tissue contrast, making cellular components visible under a microscope. However, improper staining can lead to artifacts like: Overstaining: Excessive staining can obscure cellular details.
Understaining: Inadequate staining can make cellular components difficult to distinguish.
Precipitation: Stain precipitates can form if reagents are not properly filtered or if slides are not adequately rinsed.
Mounting Artifacts
Mounting involves placing a cover slip over the stained tissue section. Artifacts in this step can include: Air Bubbles: Trapped air can obstruct the view of tissue sections.
Mounting Medium Inconsistencies: Uneven application of mounting medium can lead to distorted images.
Cover Slip Movement: If the cover slip shifts, it can cause tissues to appear misaligned.
How to Minimize Processing Artifacts
Reducing processing artifacts requires meticulous attention to each stage of tissue preparation. Some strategies include: Proper Fixation: Use appropriate fixatives and fix for the recommended time to avoid under or over-fixation.
Optimal Sectioning: Ensure microtome blades are sharp and set to the correct angle and speed.
Consistent Staining: Follow standardized staining protocols and ensure reagents are fresh and properly filtered.
Careful Mounting: Apply mounting medium evenly and avoid trapping air bubbles.
Conclusion
Processing artifacts are a common challenge in histology, but they can be minimized with careful attention to detail during tissue preparation. By understanding the types of artifacts and their causes, histologists can take steps to ensure accurate and reliable histological analysis.
