What is a Hounsfield Unit (HU)?

A Computed Tomography (CT) scan comprises of many tens, if not hundreds, of seperate X-ray exposures which are acquired by the CT scanner and composited together to form a cohesive image of the subject of the CT scan.

With all these composited images being taken and meshed together, there needs to be a way to visualise the patient’s anatomy in a meaningful way that can be interpreted by trained radiologists and doctors. This is done by attributing different colour ranges to different tissue densities.


多様な組織密度を決定するために、ゴッドフリー・ハウンズフィールド卿は、とりわけ、さまざまな解剖学的構造からの吸収によって引き起こされる減衰値(X線ビームの強度の低下)を測定することができました。1. The value of this attenuation became the Hounsfield Unit (HU).
With a baseline of 0, being the density of pure water, the Hounsfield scale can be both negative and positive. The higher the value, the more dense the matter.


What are windowing settings?

In a medical / radiology setting, Windowing relates to the grey-level mapping/contrast of a CT image and is a way of changing the Hounsfield Units/CT numbers to highlight particular areas within the medical image.

By changing both the Upper & Lower threshold values on the Hounsfield scale, it is possible to occlude (hide) certain features from the CT image, such as ‘removing the skin’ or hiding the skeletal system. View our short video below to see how easy it is to change the Upper & Lower threshold values in our DICOM Viewer. Note, the video is recorded in 3Dicom R&D but is applicable to all tiers.

Editing HU Values in 3Dicom R&D – note that it is the same process across all tiers of the software.

How to change Hounsfield values in 3DICOM Viewer?




へのアップグレード 3Dicom Surgical また 3Dicom R&D for Advanced Hounsfield Unit Measurement with a Hounsfield histogram, CT HU pointer and the ability to use presets with colour to showcase certain structures.

Disclaimer: The 3Dicom software is NOT a medical device and must not be used for treatment or diagnosis. The information contained in this article is informational only and whilst best efforts have been made to ensure the accuracy of this article, you should confirm the information provided with other sources. 3Dicom and Singular Health are not liable for any direct or indirect consequences arising from the application of the information provided.