As detailed in our previous blog about Hounsfield windowing, Hounsfield Units (HU) are used as the primary control in 3Dicom, allowing for various densities to be visualised. When users upgrade to 3Dicom Pro, they obtained features such as the ability to perform precise HU windowing and display settings, save and share measurements as well as view specific meta tags. So what other features are users given that can further enhance their analysis of medical images?
What are Hounsfield Presets?
When users upgrade to 3Dicom Pro, they are given specific ‘Hounsfield Presets’. As opposed to users manually changing their specific HUs, Hounsfield Presets allow the user to quickly reveal certain anatomy without altering any of their density display settings. The incorporation of Hounsfield Presets into 3Dicom Pro not only benefit new users who are un-informed about the density display settings, but medical specialists. It is common for medical specialists to alternate between skin, bone and muscle views of a scan so the development of Hounsfield Presets make this process much easier and efficient. Furthermore, when medical experts explain these certain densities to patients, it makes this process much less complex and understandable. So what are these Hounsfield Presets and where are they located?
The first Hounsfield Preset users are given is the ‘Skin’ preset. This preset exposes only the skin in the medical scan. The skin preset automatically sets our HU between -700 to 300. In many cases, users often set their HU around -900 when analysing skin within a scan and this most often results in in-adequate analysis. This is due to the fact that air around the scan often blocks certain features and impairs our analysis.
To use the skin preset, simply click the icon shown in Figure 1 displayed in the image below. If users need to slightly alter the preset due the scan result or individual, they can change the HU in the density display window. Figure 2 displays the HU that are automatically changed when applying this preset.
The next Hounsfield preset users are given is the ‘Muscle’ preset. This preset exposes the next significant density within the scan which is muscle. The muscle preset automatically sets our HU between -5 to 135. It is recommended that users also alter their display settings when using this preset. This is due to the fact that muscle density and size is very dependent on the patient. For example, a subject that regularly works out and undergoes consistent hypertrophy training will differ from a subject that is old and immobile. For a tutorial on how to use the display settings, refer to this guide.
To use the muscle preset, simply click the icon shown in Figure 1 displayed in the image below. Similarly to the skin preset, if users need to alter the result of the scan, they can change the HU shown in the density display window. Figure 2 displays the HU that are automatically changed when applying this preset.
The final preset that users can access is the ‘Bone Preset’. This preset exposes all the bone inside of the medical scan and hides any major muscle, skin or other densities that may interfere with our analysis of the bone. The bone preset is most commonly used when analysing 2D images (sagittal, coronal and axial) within DICOM. 2D bone images are typically clearly understood by those with little to no medical background making it smooth for discussions with patients. The bone preset automatically sets our HU between 100 to 2400.
To use the bone preset, simply click on the icon shown in Figure 1 displayed in the image below. Similiarly to the skin and muscle preset, if the user needs to change the result of the scan, they can alter the HU shown in the density display window. Figure 2 displays the HU that are automatically changed when applying this preset. Figure 3 also displays the tools we can use to display the three different types of 2D images (that are commonly used when applying the bone preset (sagittal, coronal and axial).
What are colour presets?
Colour pre-sets work similarly to the way Hounsfield Presets work. Colour presets are designed for specific scans and their corresponding analysis. There are nine different colour pre-sets incorporated into dicom all serving a specific purpose. All nine colour presets are listed below with a description, as well as the location correlating on the image.
- CT Bone
- The CT Bone preset is used when analysing any type of anatomy that is heavily dominated by bone. The CT Bone pre-set allows the user to clearly distinguish which parts of the anatomy are bone through a red and yellow colour palette. Often users may have trouble distinguishing bone from certain muscles or cartilage so the CT Bone pre-set counters this.
- CT Cardiac
- The CT Cardiac pre-set is typically used when analysing scans around the heart and circulatory system. The CT Cardiac pre-set is commonly used when analysing cardiovascular diseases and defects of the heart. This pre-set is effective in outlining signs of stress and fatigue around the circulatory system.
- CT Lung
- The CT Lung pre-set is used when analysing lungs or the chest region in a scan. Using the CT Lung pre-set is common when checking for blood clots, excess fluid, tumours or just assessing the overall health of the subjects lungs. The CT Lung pre-set is the most noticeable in appearance showing predominately blue, green and yellow with tinges of red and orange. This pre-set also significantly emphasises minor details such as small vessels and tiny pockets of air. This is due to the fact that these details are extremely important when analysing lungs.
- CT Muscle
- The CT Muscle pre-set is used when analysing any specific part of anatomy that is heavily dominated or consists of a large muscle. The CT Muscle pre-set is common when analysing a part of anatomy that is subject to a strain, rupture or break.
- The Xray pre-set is one of the most common colour pre-sets. This pre-set is typically used during patient discussion as it is typically the most understood type of scan due to it’s popularity. The Xray pre-set captures large, dense parts of the anatomy and is typically used as an overview tool. This pre-set is used in conjunction with other pre-sets if the user would like to go more into more complex parts of the anatomy.
- The inverse pre-set is essentially a colour inverse of the normal dicom view we are exposed to before adding any pre-sets. This pre-set is typically used for areas within a scan that are too dark/light to be analysed. If a flaw occurs within a scan, users can invert the colours to expose the area that is in-decipherable.
- Red, Green and Blue
- These three colour pre-sets change our anatomy to the desired colour. These three pre-sets are typically used for users who experience a visual impairment such as colour vision deficiency or colour blindness. Although these pre-sets typicaly aid users possessing a visual impairment, some users may use these pre-sets as they may overall improve the analysis with specific colours. For example, the green colour pre-set may alter a dark region of anatomy to become lighter.
Congratulations. You have just learnt what the nine different Hounsfield and colour presets do and how to apply them. Perhaps you want to learn about more 3Dicom Pro features such as using measurement tools, saving scans or precise HU windowing.