DIAGNOSTIC IMAGING - Radiography and Ultrasound Flashcards
- Radiology - Ultrasound
When taking radiographs, how can you overcome superimposition?
Take two radiographs of the object at a 90° angle from eachother
What are the three factors which determine the rate of X-ray absorption?
Tissue-radio opacity
Atomic number
Density
What is tissue-radio opacity?
Tissue-radio opacity determines how opaque a substance is
What is the difference between a high and a low tissue-radio opacity?
High tissue-radio opacity: high levels of X-ray absorption leading to an opaque object
Low tissue-radio opacity: low levels of X-ray absorption leading to a darker, more transparent object
Do objects with a high atomic number appear white or black on a radiograph?
Objects with a high atomic number appear white on a radiograph
Do objects with a high density appear black or white on a radiograph?
Objects with a high density appear white on a radiograph
List the different radiographed structures in order of tissue-radio opacity
Metal > Bone > Soft tissue/Fluid > Fat >Gas
Gas has a higher atomic number than fat but appears darker on ultrasound. Why is this?
Gas has a higher anatomic number than fat but has such a low density that it appears darker than fat on a radiograph
Which three areas of the body cannot be properly assessed on a radiography?
Spinal cord
Kidney
Bladder
What are the advantages of using ultrasound?
Good soft tissue imaging
Real time imaging
What are the the disadvantages of using ultrasound?
Poor imaging of bone and gas
Operator and machine dependent
Need to clip patient hair
What are the three ways an ultrasound beam can interact with tissues?
Reflected
Refracted/scattered
Transmitted
Describe ultrasound reflection
The ultrasound beam reflects back from the tissues, contributing to the ultrasound image
Describe ultrasound refraction/scattering
The ultrasound beam is refracted and the image lost
Describe ultrasound transmission
The ultrasound beam passes through the tissue leading to attenuation
What is attenuation?
Attenuation is the decrease in ultrasound intensity making it difficult to visualise tissues
Attenuation often occurs when trying to image deeper organs/tissues. What can be done to rectify this?
Attenuation can be reduced by increased the ultrasound transducer frequency to increase the image resolution. This does however lead to less depth perception
Which three factors influence ultrasound beam reflection?
Tissue type
Tissue echogenicity
Tissue absorption
What are the three classifications of echogenicity?
Hyperechoic (white)
Hypoechoic (grey)
Anechoic (black)
Which tissues are hyperechoic?
Bone
Gas
Fat
Fibrous tissue
Which tissues are hypoechoic?
Vascular tissue (dark grey)
Cellular tissue (light grey)
Which tissues are anechoic?
Fluid
What are the three different types of ultrasound transducer?
Sector/phased array
Linear array
Curvilinear array
Which types of ultrasound transducer produce a fan-shaped image?
Sector/phased array
Curvilinear array
Which type of ultrasound transducer produces a rectangular shaped image?
Liner array
Why are sector/phased array transducers best for imaging the heart?
Sector/phased array transducers are small enough to fit between the ribs to image the heart
Which type of transducer is best for visualising superficial structures?
Linear array
