w2 Flashcards
What are pathological processes
Pathological processes are the cause or the effect of a disruption of the normal physiological status. Associated with certain signals and anatomical structures.
What are some methods of examining Pathological Processes on the outer surface of the body
Focused Physical Examination, Medical Thermology Imaging, Medical Transillumination Imaging
what is Medical Thermology
imaging the 2D representation of the heat radiated from the human body
what is Medical Transillumination Imaging
Transillumination imaging involves the shining of visible light or near-infrared radiation through a part of the body, and viewing or imaging the transmitted radiation (noninvasively)
What are some invasive medical imaging procedures
Medical Endoscopy Imaging, Biopsy Examinations: Medical Light Microscopy Imaging and Medical Electron Microscopy Imaging
What is Medical Endoscopy Imaging
uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are inserted directly into the organ. Can be simulated using CT-scans.
define Hypertrophic
increase in the size of an organ or other part, resulting from enlargement of the individual cells.
describe the anatomical planes
Coronal/Frontal Plane: Divides the body into anterior and posterior portions.
Sagittal/Lateral Plane: Divides the body into right and left sides. If using the midline as reference then called Median plane.
Trans-Axial/Transverse Plane: A horizontal plane dividing the body into upper and lower parts.
how does Conventional X-ray Imaging capture anatomical features
X-Ray absorption is proportional to tissue density, therefore x-rays passed through the body will have a positive/negative outline of anatomical structures.
X-Ray photons are produced when electrons of high energy strike a heavy metal target (e.g. W), referred to as an X-ray Film. Contrast agents help increase the contrast between positive and negative.
How does Digital X-ray Imaging differ from conventional methods
Uses X-Ray detectors instead of films. Detectors have a phosphor screen, which is excited by the X-Rays. CCDs (Charge-Coupled Device) or TFTs (thin-film transistor) convert light from phosphor to digital signal.
how is Digital Mammography performed
breast is compressed and the x-ray is captured using a film plate.
how is Digital Angiography performed
patient is injected with a radio-contrast agent, e.g. iodine, which absorbs x-rays. The dye may fill arteries, capillaries and veins.
what is computer tomography
a computerized x-ray imaging procedure in which a narrow beam of x-rays is aimed at a patient and quickly rotated around the body in the gantry, producing signals that are processed by the machine’s computer to generate cross-sectional images or “slices” of the body.
What anatomical plane does CT capture cross sections of
Transverse Plane
What is the Hounsfield Attenuation Scale and what is its interpretation
A quantitative scale for describing radiodensity. Frequently used in CT scans. Based on water being 0 HU and air being -1000 HU. Very dense tissue can be up to 2000 HU. High-density structures are assigned brighter (whiter) colors.
What is radiodensity
the relative inability of electromagnetic radiation, particularly X-rays, to pass through a particular material. Radiolucency indicates greater transparency or “transradiancy” to X-ray photons.
What are the HUs for fat, soft tissue, and and bone
-100 HU,
+20 to +70 HU,
+400 to +2000 HU
how does MRI work
The cylinder creates a strong magnetic field that causes the protons (hydrogen) in water to align with the magnetic field. External radio frequencies/pulses are then emitted, pushing the protons slightly out of alignment. Quickly, the protons will snap back to it’s original orientation, causing a radio signal (rotating magnetic field) to be emitted. This magnetic field is detected and used as the data.
Since the hydrogen in different tissues will realign at different speeds (depending on amount of hydrogen and type of tissue, particularly water and fat), the different structures of the body can be revealed.
How are the radio frequencies from MRI analyzed to make images
filtered back projection reconstruction or Fourier analysis
what are the benefits of MRI
non-invasive, captures fine details, does not require ionizing radiation such as x-rays. Flexible technique- contrast can be varied by varying how the image is acquired, such as adding additional magnetic fields or adjusting repetition time or echo time.
What are T1 and T2 weighted images
differently constrasted MRI images based on different repetition time and echo time parameter settings.
T1: TR=small, TE=small, watery fluids are very dark, water-based tissues are mid-grey and fat-based tissues are very bright.
T2: TR=large, TE=large, fluids have the highest intensity, and water- and fat-based tissues are mid grey.
In what contexts are T1 or T2 more suitable
T1 images are often known as “anatomy scans”, as they show most clearly the boundaries between different tissues.
T2 images are often thought of as “pathology” scans because collections of abnormal fluid are bright against the darker normal tissue.
How does ultrasonic imaging work
It is based on the reflection of ultrasound at tissue interfaces.
Large, smooth surfaces in a body cause specular reflection, whereas rough surfaces and regions cause nonspecular reflection or diffuse scatter. fluid (black), soft tissue (grey), and bone (white).
In what context is ultrasound useful
can be used to image muscle and soft tissue and is particularly useful for delineating the interfaces between solid and fluid-filled spaces.
However organs, such as the brain, located beneath bone cannot be imaged clearly.
what are the benefits of ultrasound
real-time, non-invasive, portable, and inexpensive
how does PET work
Patient is injected with a radiopharmaceutical, which is a tracer tagged with radioactive atoms/isotopes. These tracers emit positrons, which annihilate with surrounding electrons. This annihilation produces gamma rays, which are detected by the device.
in what context are pet scans useful
when investigating physiological processes. It is particularly useful for detecting metabolic changes, since many malignant cells exhibit elevated glucose
metabolism (anaerobic glycolysis).
Most diseases are functional in nature and structural changes are secondary.
what is microPET imaging
A miniature PET scanner for imaging mice
What does SPECT stand for
Single Photon Emission Computed Tomography.
How does SPECT work
patient inhales or is injected with a radionuclide (like PET and unlike CT). SPECT detects the gamma rays being directly emitted from the nuclei (unlike PET and like CT). Similar to CT, the camera system rotates around the patient.
what is image registration
the process of aligning two or more images of the same scene.
This process involves designating one image as the reference image, also called the fixed image, and applying geometric transformations or local displacements to the other images so that they align with the reference. This is useful for combining functional images such as pet with anatomical images such as CT to gain a fuller understanding of the patient’s state.
what are the different names for a pixel
image element, picture element, pel
what is a k-bit image
for a grayscale image, each pixel/data structure is k-bits large, e.g. ints are 32 bits. meaning there are 2^k possible grayscale values for each pixel.
k is also referred to as the gray-level resolution, then the image is called a k gray level image e.g. 32 gray level image.
What is image reconstruction
making an image from one-dimentsional projections into a two- (or higher) dimensional object
What is the premise of the Algebraic Reconstruction Technique (ART)
the resultant reconstruction should match the measured projections (measured projection for a 1D line is a single value)
describe steps in the ART system
(1) each value of the image begins at zero. (2) in each iteration, the new pixel value is calculated as (current pixel value + (measured projection value - the pixel values along the line of projection)/number of elements in that line). (3) This is performed for each pixel along the projection lines, then the next iteration begins. (4) Iterations occur until the final image’s projection (the sum of each pixel for that direction) matches the measured projections.
what are some general challenges of medical imaging
Accessibility of the organ of interest, Variability of information, Physiological artifacts and interference, Energy limitations, Patient safety
