Page 30 - A Practical Guide to Equine Radiography

VetBooks.ir CHAPTER 3

Image quality

How do we assess image quality and what can
we do to get the best possible image?

Image quality is one of the main parameters that • Image resolution is set by the manufac-
influences the diagnostic success of an imaging turer and cannot be changed in DR systems;
procedure. The better an image, the easier lesions however, in CR systems different plates with
can be detected and misinterpretations avoided. different types of resolution are available.
While the standard plates are sufficient for
most applications, high-resolution plates may
What image parameters characterize be better for looking at fine trabecular detail.
a radiograph? • There are no guidelines in veterinary medi-
The following parameters all determine image cine as to the minimum resolution a system
quality and are influenced by our equipment needs to have; however, there are in human
and the way we take and process our images: medicine and usually the systems on the vet-
erinary market follow those as well.
• image resolution • Beware of the image resolution of the screen
• sharpness you are viewing your images on. It is point-
• image contrast less having a high-resolution image to start
• signal-to-noise ratio with if you are viewing it on a low-resolution
• exposures screen.
• distortion and magnification • Equally, beware of how an image is sent. The
• artefacts. default image format in which images are
sent is JPG which, as standard, compresses
images and this may well result in loss of
Image resolution image quality.
• Image resolution quantifies how close struc-
tures can be to each other and still be visibly
resolved and provides a measure of detail. Image sharpness
• In conventional radiography, it is usually • Image sharpness describes how well the edges
expressed as line pairs/mm (10–15 lp/mm). of a structure can be distinguished from other
In CR/DR radiography it is expressed in pix- structures or the background. Image sharp-
els, similar to what you will be familiar with ness is affected by the equipment but also by
in photo cameras and smartphones. the way we take radiographs.

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