General Principles of Imaging

Question 1

list some conventional terminology that refers to radiographs (3)

Answer 1

1. plain film
2. film
3. x-ray

Question 2

what is the difference between radiography and radiation?

Answer 2

1. radiograph - an x-ray containing an image or part of a patient’s anatomy
2. radiation - energy that is transmitted through space or matter. For medical purposes can include:
   
   1. mechanical - ultrasound
   2. electrical
   3. thermal (IR lamp)
   4. Nuclear (gamma rays)
   5. electromagnetic (x-rays)

Question 3

what are the current units of measurement for radiation?

Answer 3

gray

sievert

Question 4

shorter wave length = _______ energy = ________ penetration

Answer 4

higher energy

greater penetration

Question 5

compare soft and hard x-rays

Answer 5

• Soft
  
  • longer wave length
  • utility → trx of superficial malignancies
• Hard
  
  • shorter wave lengths
  • diagnostic imaging

Question 6

what is required for an x-ray?

Answer 6

1. production of electrons
2. force for rapid movement
3. something to halt movement rapidly
4. X-ray tube
   
   1. cathode and anode within glass tube
   2. vacuum maintained within tube
5. Kilovoltage produced between filament and anode
   
   1. electrons accelerate and then strike anode
   2. x-ray created

Question 7

x-rays are attenuated based on ________

Answer 7

tissue densities

Question 8

list the benefits of plain film (4)

Answer 8

1. low cost
2. reliable
3. relatively good quality
4. ease of use

Question 9

what is radiodensity?

• what does it determine?*
• what is it a product of?*
• What is the difference between radiopaque and radiolucent?*

Answer 9

the combo of physical qualities of an object that determine how much radiation it absorbs from the x-ray beam

1. determines attenuation
2. product of composition and thickness
3. radiographic density → blackening
4. radiopaque → harder to penetrate w/x-rays
5. radiolucent → easier to penetrate w/x-rays

Question 10

list the shades of gray relating to radiodensity

Answer 10

1. Air (black)
2. Fat (gray-black)
3. Water (gray)
4. Bone (white)
5. contrast media (bright white)
6. heavy metals (solid white)

Question 11

what does the term decubitus mean when referring to x-ray and imaging?

Answer 11

body positioned on horizontal surface with horizontal beam

Question 12

list common projections for x-rays

Answer 12

1. anterioposterior (AP)
2. posterioanterior (PA)
3. lateral

Question 13

describe the process for viewing x-ray images

Answer 13

1. hard images
   
   1. placed on illuminator with anatomic position and patient facing clinician
2. computed/digital
   
   1. viewed on screen
3. ID markers
   
   1. >/= 2 markers such as pt info, date, institution, sex, age and laterality

Question 14

list and describe terms relating to image quality

Answer 14

1. density → degree of blackening
2. contrast → affects anatomic detail (low vs high)
3. detail → geometric sharpness or accuracy of structural lines (can be affected by motion)
4. distortion → difference between actual and recorded image (may be elongated or shortened)

Question 15

describe an arthrography

Answer 15

• injection of contrast within joint space
• distends capsule
• outlines internal surfaces
• commonly used with CT, MR, fluoroscopy

Question 16

describe a myelography

Answer 16

• pertaining to spinal cord, dura mater, and nerve root
• injected into cerebrospinal fluid (subarachnoid space)
• column of radiopaque fluid
• may be administered with CT

Question 17

what is a conventional tomography and what is it’s best clinical application?

Answer 17

x-ray tube or film move about fulcrum point (focused on anatomic area)

Best clinical application → fracture evaluation

Question 18

list limitations to conventional tomography

Answer 18

1. detail cannot be enhanced
2. difficulty with positioning
3. exposure

Question 19

describe computed tomography (CT)

Answer 19

1. it is an x-ray beam and detector within a circular scanner that moves around the pt
2. computer interprets (constructs) image
3. tissues assigned different shades of gray
4. series of cross-section slices (axial); can be reconstructed in sagittal and coronal planes, as well as 3D

Question 20

describe MRI

what are the 9 signal intensities?

Answer 20

• radiofrequency waves within a magnetic field interact with tissues
• relies on detection of reemitted radiofrequency waves that are absorbed
• view in axial, sagittal, coronal planes
• signal intensities:
  
  • bone, muscle, articular cartilage, fibrocartilage, ligaments, tendons, vessels, nerves, fat
• contrast may be used

Question 21

list several example indications for CT (6)

Answer 21

1. bone and soft tissue tumors
2. fractures
3. intra-articular abnormalities
4. bone fragment detection
5. bone mineral analysis (metabolic disorders)
6. neuroimaging

Question 22

list several example indications for MRI (4)

Answer 22

1. soft tissue trauma
2. internal joint derangement
3. tumors
4. stress fractures

Question 23

list several example indications for ultrasonography (5)

Answer 23

1. muscle, tendon, and ligament lesions
2. cysts
3. soft tissue tumor
4. blood flow
5. muscle function

Question 24

list several interventions where imaging would also be utilized (7)

Answer 24

1. epidural steroid injections
2. spinal nerve blocks
3. radiofrequency ablation
4. discography
5. percutaneous needle biopsy of spine
6. percutaneous vertebroplasty, kypoplasty, cementoplasty
7. biofeedback with ultrasonography