RADIOLOGY Flashcards
what is the sagittal plane
divides the body into left and right
what is the axis plane
divides the body into superior (top) and inferior (bottom)
what is the coronal plane
divides the body into anterior/ventral (front) and posterior/dorsal (back)
what is medical imaging
non-invasive visualization of internal organs and tissues
what are the types of imagining modalities
X-ray (radiography) CT scan (X-ray computed tomography) MRI (magnetic resonanance imagining) Nuclear imaging (SPECT,PET) ultrasound mammography fluoroscopy
what are plain radiographs
commonly known as Xrays
they are two dimensional snapshot images
shadows with five basic densities
projection of x-ray imaging
- image records transmission of x-rays through object
- image depends upon absorption of x-rays
- absorption depends upon density and thickness of object and time of exposure
what does the colour intensity mean on an xray
- x-rays that pass through the body to the film reneder the film black
- x-rays that are totally blocked do not reach the film rendering it white
- air=low density=xrays pass=image is dark
- metal=high density=x-rays blocked=image is light
what are the five basic densities you can tell on an x-ray
air density-black fat density-light grey soft tissue-brighter than fat bone-most white normal structure metal-absolute white (can be labels on the film/ any metal implants)
what is an ultrasound
the bouncing of high frequency sound waves back from an object producing an image based on returning echoes
what does ultrasound tell us
- normal organ/structure
- diffuse disease causing change in echogenicity
- presence of focal lesions
- obstruction/dilation
- blood blow patterns and stenosis
what are the advantages of an ultrasound
no radiation
portable
instantaneous
excellent for cysts and fluids
doppler ultrasound is excellent to assess blood flow
excelled for newbron brain, thyroid,gall bladder, female pelvis etc
disadvantages of ultrasound
does not work well in large or obese patients
resolution less than CT and MRI
air or bowel gas prevents visualization of structures
when to use a CT and when to use an MRI
CT is faster and less expensive
CT is used in emergency and good for bones and lungs
MRI is good for brain and spinal cord
how can you differentiate between an MRI T1 and T2 image
using the CSF (cerebral spinal fluid )
in T1 it is dark and in T2 imaging it is bright
what is an MRI
strong magnet fields aligns the spin of protons of water molecules in the body. the protons absorb energy and flip their spins and when the magnetic field is turned off they gradually return to the normal positions releasing radio signals. this produces slices which can be stacked to form a 3D image like CT scans
advantages of an MRI
no overlapping
excellent resolution
very good at detecting fluid
excellent imaging for the brain,spine and joints
no radiation
multiple imaging tests within the same study eg T1 and T2
disadvantages of an MRI
very expensive
patients cannot have a pacemaker or ferromagnetic material
slower to acquire images aprox 45min
what are the advantages of a CT scan
eliminates overlapping densities
excellent resolution
excellent for detecting intracranial bleeding
excellent in the neck, chest and abdomen
excellent for evaluating fractures
what are the disadvantages of a CT scan
more expensive than an xray and ultrasound
more radiation
dense bone and metal cause severe artifacts
what is nuclear medicine ( scintigraphy)
detector records emission of gamma photons from radioisotopes introduced into the body source s(x,y,z) usually represents a selective uptake of a radio labeled pharmaceutical
what is endoscopy
it is putting a tiny camera on a flexible tube into some body part
give examples of endoscopy
gastroscopy - through the mouth into the stomach
colonoscopy - through the back entrance to the colon
rhinoscopy - up the nose
laproscopy - in the abdomen
arthroscopy - into a joint
what are the different parts of a long bone
cortex medullary cavity(marrow) diaphysis metaphysis epiphysis
what is the diaphysis
the shaft of the long bone
what is the metaphysis
the tapered part of the bone
what is the epiphysis
at the end of each long bone
where is the growth plate in children
between the epiphysis and the metaphysis
why do we use CT scans for tumors
delineates tumors extent- see spread
soft tissue extension
presence of calcification
biopsy
when do we use ultrasound
- evaluation of rotator cuff
- injuries to various tendons
- evaluation of the infant hip
