Medical Imaging Techniques Flashcards
Types of imaging
Conventional radiology (x ray) Computed tomography (CT) Ultrasonography (US) Magnetic Resonance imaging (MRI) Nuclear medicine imaging
What is a plain field study
Conventional radiology in which special techniques such as contrast media have not been used
How does conventional radiology work
Highly penetrating dreams of x rays transilluminate the patient , showing tissues of different densities of mass as images of differening intensities (light and dark)on film monitor
X ray tube—>human—> detector behind human
What appears dense (white) and less dense (dark) on conventional radiology (x ray)
Compact bone absorbs or reflects more then
Spongy bone
Organ-transparent in between
Radiolucent
Less dense
Radioopaque
Dense
PA projection
X rays transvers from posterior to anterior (x ray tube is posterior and detector is anterior)
AP projection
Opposite
Conventional radiographs are all viewed for body, head trunk shoulder, arms and legs
Patient is facing you AP view
Patient left always your right
How do you view radiographs for wrist, hands, feet
As if looking at own wrists hands or feet
What do L and R mean on radiographs
Side placed closes to the film (detector) image is viewed from same direction beam was projected
What does the introduction of contrast media(radioopaque fluids such as iodine or barium) to conventional radiography cause
Study of luminal or vascular organs and potential or actual spaces-such as digestive tract, blood vessels, kidneys, synovial cavities, and the subarachnoid space-that are not visible with plain films
Why do we usually need two views at 90 degree angles
Each radiograph represents a 2d view of 3d structure
Structures that get beams overlap each other
Need 2 views to localize an abnormality
What is seen in computed tomography
Radiographic images of body that resemble transverse anatomical sections
How does CT work
X ray passes through the body as the x ray tube and detector rotate around the axis of the body. Multiple overlapping radial energy absorption’s are measured, recorded, and compared by a computer to determine the radio density of each volumetric pixel (vowel) of chosen body plane
In CT the computer maps the vowels into a ___ __ that is displayed on a monitor or print out
Planar image (slice
In a CT what is seen as light and dark
Light-bone treated absorption (transparent) white
Dark-little absorption
How is an axial ct viewed
As if standing at patients feet -from inferior
How are coronal ct images viewed
As if patient is facing you
How are sagittal ct viewed
Standing at patients left side
What is ultrasonography used for
Visualizesuperficial or deep structures in body by recording pulses of ultrasonic waves reflecting off the tissues
Advantadge of ultrasonography
Cheap and transportable
Real time-can see things moving
Structures and flow in vessel
How does ultrasonography work
Transducer in contact with skin generates high frequency sound waves that pass through the body and reflect off tissue interfaces between tissues of differing characteristics, such as soft tissue and bone . Echoes from the body reflect into the transducer and convert to electrical energy. The electrical signals are recorded and displayed on a monitor as a cross sectional image which can be viewed in real time and recorded as a single image or on videotape
Doppler ultrasonography
Shifts in frequency between emitted ultrasonic waves and their echoes are used to measure the velocities of moving objects . Blood flow through vessels seen in color superimposed on a 2d cross sectional image
What does scanning the pelvic viscera require for ultrasound
Fully distended bladder. The urine serves as an acoustical window, transmitting sound waves to and from the posteriorly placed pelvic viscera. Distended bladder also displaces gas filled intestinal loops out of the pelvis
Why do transvaginal ultrasound
Permits positioning of transducer closer to the organ of interest and avoid fats and gas which absorb or reflect sound waves, whereas air conducts them poorly.
Ultrasound used for lungs
No
Does ultrasound use radiation
No
MRI provides images of the body similar to those of CT scene but is better for ___ __ differentiation
Soft tissue
How does MRI work
Person placed in scanner with a strong magnetic field, and the body is pulsed with radio waves. Signals subsequently emitted from the patients tissues are stored in a computer and reconstructed into various images of the body .
For MRI, how can how can we control appearance of tissues to generate images
Controlling radio frequency pulses
In MRI, free protons int he tissues that become aligned by the surrounding magnetic field are excited (flipped) with a radio wave pulse. As the proton lips back, minute but measurable energy signals are emitted. What emits stronger and weaker signals
More signals emitted by tissues that are high in proton density, such as fat and water
Weaker0less protons
What do moving fluids appear as what on T1
Black
Even through proton dense, after flip they move out of field
T2
World was 2 Water looks white t2 Fat dark Blood flow dar Subacute blood bright Cyst bright Solid mass bright
T1
Fat bright Acute and chronic blood gray Subacute blood bright Cyst dark Solid mass dark
MRI see real time?
Yea with fast scanners
Nuclear medicine imaging
Infor about distribution or concentration of trace amounts of radioactive substances introduced into the body. Shows images of specific organs after IV injection of a small dose of radioactive material
A radionucleotide is attached to a compound that is selectively taken up by an organ such as ___ fr bone scanning
technetium-99m
Tc-MDP
Positron emission tomography
Uses cyclotron produced isotopes of extremely short half life that emit positrons
Examines the physiologic function of organs such as the brain on a dynamic basis
Images viewed as whole organ or cross section
SPECT
Similar to PET but longer lasting tracers
Less costly but more time and have lower resolution
