lecture 1 Flashcards
What is the common image depth in medical images
usually higher than 8 bits (commonly 16 bits)
what does the 8 bits image depth allows for
( 256 shades of grey)
what is DICOM
a standard format used for medical imaging
What is GIMP
a popular image editing software but it is not equipped to handle 16bits medical images
Does dicom support 8 bits
yes but it cannot support more. so it cannot handle medical images as they often feature more than 8 bits of image depth (16bits)
Dicom plug-in
a special plug in is an add on installed to GIMP to allow it to properly handle images with higher bit depth
in the case of the MR or CT,
the easiest way to get a suitable range of grey scales for display is”
a linear transform of the grey values ρ so that the maximum and the minimum of the image fit with the data range of the pixels to be
displayed.
Linear intensity transfer
function
a function that operates on all grey values of an imnage
what does this statement mean “not all types of grey values are suitable for direct display”
means that some processing or adjustment may be needed to make images more visually interpretable and informative, by highlighting relevant details and minimizing distractions or noise.
From a discrete point of view, an ITF is
a lookup-table – it assigns new grey values (ρ’) to
the old grey values (ρ)
Non-linear Intensity Transfer Function (ITF):
increasing the intensity value in the original image might not lead to a proportional increase in brightness in the displayed image. Instead, the mapping could be such that certain intensity values are compressed or expanded, resulting in enhanced contrast, improved visibility of certain features, or better overall visual perception.
Non-linear ITFs can take various forms
logarithmic, exponential, sigmoidal, or piecewise functions
Modelling dynamic range – the
Sigmoid
In the context of dynamic range modeling, the sigmoid curve can represent the relationship between the input, which is the intensity levels of the captured image, and the output of a system, which can be the intensity levels of the displayed image after processing .
what is Windowing
An important intensity operation, s a technique used to adjust the brightness and contrast of an image to better visualize specific features or tissues of interest.
involves selecting a specific range of intensity values, called the “window,” within the overall dynamic range of the image.
How is the window defined?
By choosing a window center (C, ω) and a window width (W, σ), one can define an intensity range of interest.
* All grey values below the borders of the window are set to black, all above are set towhite.
* A subsequent linear intensity transform spans the grey value range to a range appropriate
for human perception
