问题描述
DICOM图像（CT）中的rescale intercept和rescale slope是什么？
如何计算窗口宽度和窗口中心？
What is "rescale intercept" and "rescale slope" in DICOM image (CT)?How to calculate window width and window center with that?
推荐答案
重新缩放截距和斜率用于转换将图像的像素值转换为对应用程序有意义的值。
The rescale intercept and slope are applied to transform the pixel values of the image into values that are meaningful to the application.
例如，原始像素值可以存储特定于设备的值，该值仅在由生成它的设备：将rescale slope / intercept应用于像素值会将原始值转换为光密度或其他已知测量单位（例如hounsfield）。
For instance, the original pixel values could store a device specific value that has a meaning only when used by the device that generated it: applying the rescale slope/intercept to pixel value converts the original values into optical density or other known measurement units (e.g. hounsfield).
转换时不是线性的，然后应用LUT（查找表）。
When the transformation is not linear, then a LUT (lookup table) is applied.
应用模态变换后（重新缩放斜率/截距或LUT）然后窗口宽度/中心指定哪些像素应该是可见的：窗口指定的值之外的所有像素都显示为黑色或白色。
After the modality transform has been applied (rescale slope/intercept or LUT) then the window width/center specify which pixels should be visible: all the pixels outside the values specified by the window are displayed as black or white.
例如，如果窗口中心为100且窗口wid th为20然后所有值小于90的像素显示为黑色，所有值大于110的像素显示为白色。
For instance, if the window center is 100 and the window width is 20 then all the pixels with a value smaller than 90 are displayed as black and all the pixels with a value bigger than 110 are displayed as white.
这允许仅显示部分图像（例如仅显示骨骼或仅显示组织）。
This allow to display only portions of the images (for instance just the bones or just the tissues).
Hounsfield比例：
Hounsfield scale: http://en.wikipedia.org/wiki/Hounsfield_scale
如何应用重新缩放斜率/截距：
final_value = original_value * rescale_slope + rescale_intercept
How to apply the rescale slope/intercept:final_value = original_value * rescale_slope + rescale_intercept
如何使用窗口中心/宽度计算要显示的像素：
How to calculate the pixels to display using the window center/width:
- lowest_visible_value = window_center - window_width / 2
- highest_visible_value = window_center + window_width / 2
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