Medical Image
The set of techniques that
noninvasively produce images of
the internal aspect of the body
Image Quality
It refers to how well the image conveys anatomical or functional information to the interpreting
physician such that an accurate diagnosis can be made.
4 factors of Image Quality
- Spatial Resolution
- Contrast Resolution
- Convolution
- Physical Mechanisms of Blurring
Spatial Resolution
- Spatial resolution describes the level of detail that can be
seen on an image. - relates to how small an object can be seen on a
particular imaging system
Contrast Resolution
It refers to the ability to detect very subtle changes in gray
scale
- t pertain to the signal-to-noise
ratio (SNR) in an image.
Convolution
The integral calculus procedure that accurately
describes mathematically what the blurring process does
physically.
Physical Mechanisms of Blurring
It refers to the process of reducing the spatial resolution of an image produced by an optical device by accidental defocusing
Accuracy
It refers to the closeness of something to the center/target
Precision
It refers to the closeness of things to each other
5 Sources of Image Noise
- Grain Noise
- Electronic Noise
- Structured Noise
- Anatomical Noise
- Quantum Noise
Grain Noise
- The increase in the optical density of an image results in the increase of the density of the reduced silver halide crystals that adheres to the film
Electronic Noise
It refers to the added electron noise in the signal that can come from thermal noise, shot noise, and others.
Structured Noise
It is about the different offset noise and gained characteristics that a group of detectors elements read out because each channel uses its own
amplifier circuits and these circuits cannot be perfectly
tuned with respect to each other.
Anatomical Noise
It refers to the patient anatomy that is present on the image but is not important for the diagnosis
Quantum Noise
- Quanta refers to the number of particles that can be counted
- Low quanta in imaging modalities that is based on ionizing radiation results in quantum noise
What is the picture element of an image?
Pixels
What is the volume element of an image
Voxel: gives depth to the image
2 categories of an Image Data Format
First, the formats intended to standardize the image generated by diagnostic modalities: DICOM
Second, the formats aim is to facilitate and strengthen post-processing analysis: Analyze, Nifti, Minc
4 Imaging Data Format
- Analyze
- Nifti
- Minc
- DICOM
Analyze
- File extension: .img & .hdr
- created in Mayo Clinic, USA at the end of 1980
- Designed for multidimensional data
Nifti
- FIle Extension: .nii
-Stands for: Neuroimaging Informatics Technology Institute - created at the National Institute of Health (NIH) in the 2000s
- AKA Revised Analyze Format
- Intended to create a format for neuroimaging
maintaining the advantages of the Analyze format, but solving the weaknesses
Minc
- File Extension: .mnc
- developed at the Montreal Neurological Institute
- Intended to provide flexible data format
DICOM
- File Extension: MPEG and such
- AKA Digital Imaging and Communications in Medicine
- Established by the American College of Radiology and
the National Electric Manufacturers Association
Phoenix
- It is capable of extracting the protocol and replicate it for a new acquisition in DICOM
