Meetings » 10th CTUG Meeting » Abstracts

CT Numbers - Think of a number, double it, add 20, divide by 4...

Jane Edwards

Royal Free Hospital,


At our hospital we currently have two different manufacturers' scanners available to us in the imaging department. On reviewing images of certain pathologies, involving the liver, kidney and pancreas, the clinicians noted an offset in the CT numbers for the same position in the same image when viewed on the two different manufacturers reviewing workstations. This has possible serious clinical consequences as this could result in misdiagnosis of the pathology in question.

We were asked by the clinicians to explore this problem and determine the degree of offset. We designed an investigation that involved scanning an image quality phantom containing different materials covering a range of CT numbers. The phantom was imaged on both scanners using matching scan parameters to minimise variations in the resulting images. The acquired images were then distributed to all the possible combinations of workstations and scanners available. Analysis was completed for the images from each scanner, with the middle image of the sequence used in all cases to limit any partial volume and edge effects. The CT number of each material was recorded and a quantification of the offset was made.

This presentation aims to discuss the issues and the solutions found for this problem.

Click the link for a pdf of the presentation: view pdf version of presentation

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