Introduction to Imaging Flashcards
What does the transducer in ultrasound produce and at what frequency?
Theres a transducer producing high frequency sound beams at a frequency of (2-20MHz)
What does the computer analysis convert and into what in ultrasound scanning?
The computer analysis converts reflected sound waves into an electrical signal and grey-scale image
What are the high frequency sound waves in ultrasound generated by?
generated by electric crystals within the ultrasound transducer (PIEZOELECTRIC)
How does fat appear as in ultrasound and why?
Fat is high reflectivity of sound waves on ultrasound and appears white
How does fluid appear in ultrasound?
Fluid(bile and blood) appears black on ultrasound
How do we differentiate between fat and calcified prodcuts?
Sound waves are unable to penetrate calcium and so we get an acoustic shadow
What is ultrasound scanning used in?
- Assessment of liver and biliary tract, solid organs
- Renal imaging: Kidney size, collecting systems, masses, calculi and cysts
- Occult abdominal collections, abscesses
- Obestric and gynaecological disease
- Vascular/doppler imaging
- Muscoskeletal
What frequency of sound waves give better resolution and why?
Higher frequency sound waves give better resolution because the wavelength is smaller
What frequency of sound wave penetrate deeper into the body?
Lower frequency sound waves penetrate deeper.
Why is an ultrasound gel used?
Ultrasound gel is used to exclude air between the patient skin and probe
What are plain films(X-rays) used in?
Used in X-rays for fractures
What gram is being formed by plain films?
A shadow gram is being formed
What color does bone appear in plain films?
Bones appear white
What color does soft tissue appear in plain films
Soft tissue appear grey
What is mammography used to look for and why?
Mammography is lesser x-rays looking for breast disease
Why do bones appear white on plain films?
Ca2+ in bones stops x-rays from penetrating hence bones appear white on x-rays
Why is contrast medium added in contrast studies?
Contrast medium is added to look at a particular structure in more detail
What contrast medium is used for enteral structures?
Barium or iodine based(low osmolar non ionic) compounds for GI tract
What contrast medium is used for intravenous structure and what is it used in?
Iodinated
Used for urography and venography
What contrast medium is used for intra-arterial structure and what is it used in?
- Iodinated
- Used in peripheral vascular disease, coronary disease, renal transplants, cerebral circulation
What contrast medium is used for ducts and tubes and what is it used in?
- Iodinated
- Used in salivary, naso-lacrimal, urethra, fallopian tubes
What is computed tomography(CT) used in?
- Used in:
- Strokes
- Staging of malignant disease
- Trauma
- Pancreas and retroperitoneum
- Abdominal disease
- Chest mass and diffuse lung disease
How does blood appear in a CT scan immediately and after a while when its an acute haemorrhage?
- Blood appears bright
- Blood turns grey after a while and eventually dark
How does fluid appear in a CT scan?
Fluid will appear dark
