Filling in of an anechoic region due to finite slice thickness is known as which artifact?

• A. Partial volume artifact
• B. Slice thickness artifact
• C. Section thickness artifact
• D. Ghosting artifact

Answer: (B)

This question centers on how the finite thickness of the ultrasound slice can cause echoes from tissue outside the ideal imaging plane to contribute to the image, filling in an area that should be anechoic. When the scan slice is not infinitely thin, structures surrounding the true plane can lie within the slice thickness and their echoes get averaged into the display, making a truly anechoic region appear partially or wholly filled. This specific effect is known as slice thickness artifact.

It’s related to the idea of partial volume averaging, where a single image voxel contains multiple tissue types and their echoes blend. However, the description given—filling of an anechoic region due to the finite slice thickness—maps most directly to slice thickness artifact. The term section thickness artifact is sometimes used interchangeably, but slice thickness artifact is the most direct description of this particular phenomenon. To reduce it, using thinner slices, higher-frequency transducers, or imaging techniques that narrow the slice can help.