Slice Thickness

The advantage of thin slice acquisition and reconstruction is that the subtle reticular and interstitial abnormalities are better visualized due to improved resolution, and reduction in partial volume effects seen on thicker slices. This can be seen in this series of images reconstructed from the same raw dataset with the same soft-tissue kernel but at different size reconstructions of 5 mm, 3 mm and 1 mm. While it is clear in each of the images that the patient has parenchymal abnormalities, what becomes increasingly clear as we evaluate the 5 mm, 3 mm, and 1 mm cut are the fine details of reticulation and architectural distortion, which become more clear with thinner slice thickness. More importantly, on the 5 mm section, there appears to be a fair amount of ground glass opacity, which is still visible in the 3 mm image, but in the 1 mm image, we conclude that in fact it is reticular interstitial architectural distortion with very little ground glass abnormality.

Another important feature to note is that this patient has honeycombing that is clearly seen on the 1 mm, is hinted at on the 3 mm, but not seen at all on the 5 mm thick cuts. This is clear evidence of the importance of 1 mm cuts to identify key features of interstitial lung disease, and why an acceptable CT scan for a patient must include at least some images acquired at 1 mm, if not the entire dataset.