Stereotactic core needle biopsy targeting errors

Case contributed by Dr Morlie L Wang

Presentation

These diagrams explain various types of errors when targeting during stereotactic guided core needle biopsy. This is on a prone stereotactic table. The positive/negative X, Y and Z designations can vary on different systems.

Patient Data

Gender: Female

Good position.

Diagram

This needle is in good position.

Negative Y-axis error.

Diagram

This is a negative Y-axis error (some other systems may call this a positive Y-axis error). You can move needle if too far away or just sample at 6:00.

Positive Y-axis error.

Diagram

This is a positive Y-axis error (some other systems may call this a negative Y-axis error). You can move needle if too far away or just sample at 12:00. 

Negative X-axis error.

Diagram

This is a negative X-axis error (some other systems may call this a positive X-axis error). You can move needle if too far away or just sample at 3:00. 

Positive X-axis error.

Diagram

This is a positive X-axis error (some other systems may call this a negative X-axis error). You can move needle if too far away or just sample at 9:00. 

Negative Z-axis error.

Diagram

This is a negative Z-axis error. You need to push the needle in more. 

Positive Z-axis error.

Diagram

This is a positive Z-axis error. You need to pull the needle out more. 

Good position.

Diagram

This is in good position. The right and left images are just flipped. 

Case Discussion

The errors described are for the prone table at my institution. The positive/negative designations in the parenthesis may be for other stereotactic systems. It is just a matter of what the system labels as positive or negative. The important thing to know is if it is a X, Y or Z axis and how to move the needle to target or where to sample to biopsy the target. In real life, you can see the needle moving with your naked eyes so you don't really know positive/negative. 

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