Overview of Diagnostic Imaging
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Name four methods of diagnostic imaging
Radiography and computed tomography Scintigraphy MRI Ultrasonography
What is the physical basis of radiography/CT and what can these images show?
X-rays Show variations in physical density
What is the physical basis of scintigraphy and what can this show?
Gamma rays Shows metabolic activity
What is the physical bases for MRI and what can this show?
Radiowaves Shows magnetization ?!!
What is the physical basis for ultrasonography and what can this show?
High frequency sound Shows echogenicity
Define radiography
Making images representing a shadow of an object placed in an xray beam
Which structures show as most radiopaque/radiolucent?
Opaque: Bone - Soft tissue and liquid - Fat - Air : Lucent
How does CT differ from a standard radiograph?
Ring of xrays taken and amalgamated to make cross sectional slice - uaully looked at in the tranverse but can also look at sagittal plane and rebuild to make 3D image
What is scintigraphy most often useful for?
Bone metabolism
Where is diffuse uptake often noted in the normal anima;?
Growth plates and joints
Why is scintigraphy useful?
More sensitive than radiographs for bony changes
What is the main use of MRI?
Brain and spinal imaging
How does MRI work?
Apply a pulsed magnetic energy and collecting radiowaves emitted by patient between pulses Must be contained in a tunnel to allow a uniform magnetic field to form around the patient.
How would a heamotoma appear on MRI?
Heterogenous
How are colour changes on MRI referred to?
“Signal” - An “Abnormal signal” Fat has a “bright signal”
What form of radiography may be useful for observing dynamic processes?
C arm radiography Allows real time moving xray
How does ultrasonography work?
Fire pulses of high frequency sound and collect returning echos
How are images of ultrasound described?
Hypo or hyper echoic
How do liver and spleen appear relative to each other on ultrasound
Spleen is hyperechoic (brighter)
How do bladder and prostate appear differnet on ultrasound?
NB: Would appear the same on radiogrpah Bladder is hypo-echoic due to urine
When is diagnostic imaging most likely to be useful?
Structural lesions of a system rather than a dysfuntion