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## What is window level in CT scan?

The window level (WL), often also referred to as window center, is the midpoint of the range of the CT numbers displayed. When the window level is decreased the CT image will be brighter and vice versa.

## What is the difference between window width and window level in CT?

The window width is the range of the grayscale that can be displayed. The center of grayscale range is referred to as the window level.

What is the window width in CT?

The window width (WW) as the name suggests is the measure of the range of CT numbers that an image contains. A wider window width (2000 HU), therefore, will display a wider range of CT numbers.

What is CT bone window?

CT windowing ‘Bone windows’ are used to emphasise a narrow range of densities close to the density of bone. When viewing a CT scan of the brain, both the brain window images and the bone window images must be viewed routinely.

### What is window width control?

In the figure below, the window width (W) determines the range of pixel values that will be incorporated into the display width. Increasing W will reduce display contrast (see figure) whereas decreasing the W increases the brightness interval between two consecutive pixel values.

### How are window levels calculated in CT?

Upper and lower grey level calculation

1. the upper grey level (x) is calculated via WL + (WW ÷ 2)
2. the lower grey level (y) is calculated via WL – (WW ÷ 2)

Which is a typical bone window setting?

To view bone, the window level is set at about 250 HU with a wide window width (1000 HU). For soft-tissue structures, a level of 50 HU and a width of 250 HU are selected. For air-filled structures (e.g. lung) a level −600 HU and a width 1000 HU are used.

What is bone window setting?

Bone window is useful for visualizing details of bone structures and identifying subtle skull lesions. However, the details of soft tissues such as brain, that shows density lower than that of bones, are lost in the bone window setting.

## How many windows are in CT?

For head CT, bone window and brain window are two important window settings. Bone window is useful for visualizing details of bone structures and identifying subtle skull lesions. However, the details of soft tissues such as brain, that shows density lower than that of bones, are lost in the bone window setting.

## How does window width affect contrast?

How does choosing a narrow window impact the CT image?

What window should a chest CT be viewed in?

A soft tissue window is used to view most organs. A soft tissue window cannot be used for lung parenchyma, as lung density (−500 HU) is outside range and will appear completely black.

### When to use bone window settings on CT?

The use of bone window settings is helpful for detecting appendicoliths when evaluating patients for acute appendicitis, particularly patients in whom evidence of appendicitis is equivocal. In this era of PACS (picture archiving and communication systems), bone window settings should be used routinely.

### Which is better bone window or brain window?

For head CT, bone window and brain window are two important window settings. Bone window is useful for visualizing details of bone structures and identifying subtle skull lesions. However, the details of soft tissues such as brain, that shows density lower than that of bones, are lost in the bone window setting.

Is the bone window the same as the lung window?

As seen in the examples below the ‘Lung’ preset shows details in lung tissue not apparent on the ‘Bone’ window, but conversely much of the detail in bone and subcutaneous soft tissue is lost on the ‘Lung’ window. Other presets are listed, similar to those found as standard on CT Workstations.

How is the window width related to CT?

The window width (WW) as the name suggests is the measure of the range of CT numbers that an image contains. A wider window width (2000 HU), therefore, will display a wider range of CT numbers. Consequently, the transition of dark to light structures will occur over a larger transition area to that of a narrow window width (<1000 HU).