DIAGNOSTIC IMAGING - Radiography and Ultrasound

Question 1

When taking radiographs, how can you overcome superimposition?

Answer 1

Take two radiographs of the object at a 90° angle from eachother

Question 2

What are the three factors which determine the rate of X-ray absorption?

Answer 2

Tissue-radio opacity
Atomic number
Density

Question 3

What is tissue-radio opacity?

Answer 3

Tissue-radio opacity determines how opaque a substance is

Question 4

What is the difference between a high and a low tissue-radio opacity?

Answer 4

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

Question 5

Do objects with a high atomic number appear white or black on a radiograph?

Answer 5

Objects with a high atomic number appear white on a radiograph

Question 6

Do objects with a high density appear black or white on a radiograph?

Answer 6

Objects with a high density appear white on a radiograph

Question 7

List the different radiographed structures in order of tissue-radio opacity

Answer 7

Metal > Bone > Soft tissue/Fluid > Fat >Gas

Question 8

Gas has a higher atomic number than fat but appears darker on ultrasound. Why is this?

Answer 8

Gas has a higher anatomic number than fat but has such a low density that it appears darker than fat on a radiograph

Question 9

Which three areas of the body cannot be properly assessed on a radiography?

Answer 9

Spinal cord
Kidney
Bladder

Question 10

What are the advantages of using ultrasound?

Answer 10

Good soft tissue imaging
Real time imaging

Question 11

What are the the disadvantages of using ultrasound?

Answer 11

Poor imaging of bone and gas
Operator and machine dependent
Need to clip patient hair

Question 12

What are the three ways an ultrasound beam can interact with tissues?

Answer 12

Reflected
Refracted/scattered
Transmitted

Question 13

Describe ultrasound reflection

Answer 13

The ultrasound beam reflects back from the tissues, contributing to the ultrasound image

Question 14

Describe ultrasound refraction/scattering

Answer 14

The ultrasound beam is refracted and the image lost

Question 15

Describe ultrasound transmission

Answer 15

The ultrasound beam passes through the tissue leading to attenuation

Question 16

What is attenuation?

Answer 16

Attenuation is the decrease in ultrasound intensity making it difficult to visualise tissues

Question 17

Attenuation often occurs when trying to image deeper organs/tissues. What can be done to rectify this?

Answer 17

Attenuation can be reduced by increased the ultrasound transducer frequency to increase the image resolution. This does however lead to less depth perception

Question 18

Which three factors influence ultrasound beam reflection?

Answer 18

Tissue type
Tissue echogenicity
Tissue absorption

Question 19

What are the three classifications of echogenicity?

Answer 19

Hyperechoic (white)
Hypoechoic (grey)
Anechoic (black)

Question 20

Which tissues are hyperechoic?

Answer 20

Bone
Gas
Fat
Fibrous tissue

Question 21

Which tissues are hypoechoic?

Answer 21

Vascular tissue (dark grey)
Cellular tissue (light grey)

Question 22

Which tissues are anechoic?

Answer 22

Fluid

Question 23

What are the three different types of ultrasound transducer?

Answer 23

Sector/phased array
Linear array
Curvilinear array

Question 24

Which types of ultrasound transducer produce a fan-shaped image?

Answer 24

Sector/phased array
Curvilinear array

Question 25

Which type of ultrasound transducer produces a rectangular shaped image?

Answer 25

Liner array

Question 26

Why are sector/phased array transducers best for imaging the heart?

Answer 26

Sector/phased array transducers are small enough to fit between the ribs to image the heart

Question 27

Which type of transducer is best for visualising superficial structures?

Answer 27

Linear array