L3: Radiology of the musculoskeletal system

Question 1

How do you produce X-rays?

Answer 1

Beam of electron
Through sample
Onto detector

Question 2

In X-rays how does density have an impact?

Answer 2

Density affects amount of radiation absorbed

Denser material= more absorbed= less of detector= appears white

Question 3

In X-rays what appears white and what appears black?

Answer 3

White = bone (dense materials) all radiation absorbed
Black= air (less dense) radiation hits detector

Question 4

What are the advantages of x-rays?

Answer 4

Inexpensive
Quick to obtain
Readily available

Question 5

What are the disadvantages?

Answer 5

Uses ionising radiation

Poor soft tissue contrast resolutions

Question 6

What are X-rays used to detect bones?

Answer 6

Fractures
Dislocation 
Chronic bone or joint pathologies
--> osteomyelitis 
Arthritis 
--> chronic and rheumatoid

Question 7

What can you see on X-ray of long bones?

Answer 7

Periosteum
Cortex- thick diaphysis, thin epiphyses/ metaphyses
Medullary cavity
Articular cartilage- appears as joint space

Question 8

What is a fracture?

Answer 8

Partial or complete break in continuity of a bone

Question 9

What types of fractures are there?

Answer 9

Transverse- one side to other, right angle to axis
Linear- parallel with bone
Non displaced oblique- Diagonal break, bone stay alligned
Displace oblique- Diagonal break, bones don’t stay inline
Spiral- break goes around bone, start and finish not at same point
Compression- bone crumbles,
Greenstick- children mainly, incomplete fracture, bone bends and cracks
Epiphyseal separation- fracture extends through growth plate, separate epiphyses and diaphysis

Question 10

What happens to bones as children grow up?

Answer 10

Birth- Long bone separate ossification centres
–> primary (diaphysis), secondary (epiphysis)
–> separated by growth plate–> less mineralised –> appear opaque on x-ray
Child grows –> growth plate thinner –> close
Bone gradually calcify

Question 11

What influences proliferation and transformation of cell in growth plate? How can this be used?

Answer 11

Growth hormone- promotes
Thyroid deficiency inhibits
Bone age study –> determine MSK maturity
Significant difference between bone and actual age–> pathology (early or late puberty, thyroid deficiency etc…)

Question 12

What are the 8 simplified steps of bone healing? (NOT body log version)

Answer 12

Haematoma formation
Tissue dies
Inflammation/ cellular proliferation
Angiogenesis/ Formation of granulation tissue/ Procallus
Soft (fibrocartilagenous) callus formation
Lamellar bone
Remodelling

Question 13

What are the three phases in radiology? How long do they last?

Answer 13

Inflammatory phase–> hours to days
- haematoma formation
- tissue death
- inflammation/ cellular proliferation
Reparative phase –> days to weeks –> mineralisation seen, eventually trabecular seen
-angiogenesis/ formation of granulation tissue/ procallus
-Soft (fibrocartilagenous) callus formation
- Lamellar bone
Remodelling –> months to years –> fracture line obscured

Question 14

How does CT scan differ from X-rays ?

Answer 14

Uses narrow X-rays
Images slices
Creates 2D or 3D image

Question 15

What are the advantages of a CT scan?

Answer 15

Better soft tissue detail
Whole body- short period of time
Manipulation of image with computer software
Subtle fractures seen

Question 16

What are the disadvantage of CT?

Answer 16

More ionising radiation
Motion artefact (move-blurs image)
Obese- cant fit in scanner
Poor soft tissue compared to MRI

Question 17

How is the density of tissue measure in CT? How does this compare to whats seen on a scan?

Answer 17

Measured in Hounsfield units
Tissues <0HU dark –>air, water
Tissue 0-40 HU Grey –> soft tissue
Tissue >40HU white –> bone

Question 18

What do ‘windows’ show?

Answer 18

CT scan manipulate grey scale

view tissue of interest

Question 19

How does MRI work?

Answer 19

Uses magnetic to cause proton in H atoms to line up
Adds radiofrequency pulse
Causes unalligned (facing wrong direction) to flip
Remove Radiofrequency energy released
Signal detected
Creates image

Question 20

What are the advantage of MRI?

Answer 20

Non ionising radiation
Better for imaging soft tissue
Image manipulated

Question 21

What are the disadvantages of MRI?

Answer 21

Micro-architecture of bone poor
Takes longer
Claustrophobic
Electronic or metal devices must be removed

Question 22

What the difference between T1 and T2 weighted images?

Answer 22

T1 weighted- Fat white
T2 weighted- Water and fat white
Injection of dye may also improve image (gadolinium)

Question 23

What is STIR MRI?

Answer 23

Fluid senstive sequence, fat signal suppressed so fluid is seen better

Question 24

How does ultrasound (ultrasonography) work?

Answer 24

High frequency sound waves
Tisses deflect wave back to transducer
Analysed–> creates image

Question 25

What are the advantages of ultrasound?

Answer 25

Non ionising
Non invasive
Excellent soft tissue- superficial 
Tendons and peripheral nerves 
Fluid collection 
Superficial foreign bodies
Dynamic imaging
Image guided MSK intervention

Question 26

What are the disadvantages of ultrasound?

Answer 26

Operate dependant
Limited bone and intra-articular imaging
Poor deep tissue resolution

Question 27

What is nuclear medicine?

Answer 27

Uses radio-labelled isotopes
Attached to biologically active drugs
Assess metabolically active bone- diseased, healing, osteomyelitis

Question 28

Why is ionising radiation bad? What precautions should be taken?

Answer 28

Deposit energy in any organ or tissue - DNA damage 
Rapidly dividing cells most susceptible 
Medical personal--> led aprons
Minimise exposure--> films badges
Low dose radiation
Only when necessary