Session 1 embryology and radiology

Question 1

Which genes control segmentation in embryology?

Answer 1

Hox genes

Question 2

What is segmentation in the embryonic period?

Answer 2

Patterning and segregation of cells into repeating units (segments) along the longitudinal axis.

• what limb develops from a limb bud
• how many fingers

Question 3

What is a homeotic mutation?

What does it cause?

Answer 3

Mutation of a Hox gene?

The tissue to alter their differentiation pattern.
E.g. a 6th lumbar vertebra develops instead of the 1st sacral vertebra / 6th didgit develops

Question 4

What causes thoracic outlet syndrome?

What is it?

Answer 4

Compression of nerves and vessels from the neck to the armpit due to extra cervical ribs (Hox gene/ homeotic mutation)

Question 5

When do the limb buds develop?

How do they elongate?

Answer 5

4th week of development

mesenchyme proliferation

Question 6

When does endochondrial ossification begin in embryonic development?

Answer 6

12th week

Question 7

Describe how the limbs rotate in development?

Answer 7

Upper limbs externally rotate through 90 degrees

Lower limbs internally rotate through almost 90 degrees

Question 8

Why does sartorius muscle follow an oblique path?

Answer 8

Due to internal rotation of the lower limbs during development

Question 9

Why does bone appear whiter than tissue on an X ray?

Answer 9

Bone is more radiodense so absorbs more electrons (radiation)

Question 10

What is ‘joint space’ on an X-ray?

Answer 10

The place where articular cartilage is present. The cartilage is radiolucent so can’t be seen on an X-ray

Question 11

Two fractures which only occur in children?

Answer 11

• Green stick fracture
  (bone bends and cracks)
• Epiphyseal separation fracture
  (epiphysis slips off the metaphysis)

Question 12

Most common place for a compression fracture?

Answer 12

Lumbar vertebrae

looks like a squashed can

Question 13

How does an epiphyseal separation fracture occur?

Which patients do they commonly occur in?

Answer 13

The fracture extends through an unfused growth plate (epiphyseal plate) so the epiphysis is removed from the metaphysis

Overweight, adolescent boys during a rapid growth spurt. In the femur; presents as hip pain and limp

Question 14

What can affect the cell proliferation and transformation within the epiphyseal growth plate?

Answer 14

Growth hormone - increased

Thyroid deficiency- reduced
Excess corticosteroids - reduced

Question 15

How do you calculate a bone age?

Answer 15

X-ray of the hand to determine the ossification of the carpal bones in the wrist as they gradually ossify from birth until 12 years old

Question 16

8 steps in a fracture healing

Answer 16

(fracture)
haematoma 
necrosis
inflammation 
granulomatous tissue/ angiogenesis 
soft callus (fibrocartilaginous)
hard callus (woven bone)
lamellar bone 
remodelling

Question 17

Benefits of CT scanning compared to X ray

Answer 17

(Both use X ray beams
CT is a polo mint)
- CT images can be assembled to produce 3D images
- Better for soft tissues
- Ability to manipulate the image afterwards allows you to see tissues of different density in the same image slice
- High resolution; can be used in real time

Question 18

Negatives of CT

Answer 18

• higher radiation dose
• motion artefact if the patient moves
• some patients are allergic to intravenous contrast
• very obese patients can’t always fit the polo

Question 19

Units of tissue density in a CT scan?

Density > 100 HU appears ____?
Density < 0 appears____?

Answer 19

Hounsfield Units (HU)

Above 100 is white (bone)
Below 0 is dark

Question 20

How does MRI work?

Answer 20

• Magnets produce a strong magnetic field which causes protons in the body (in hydrogen atoms) to align with the field. (No radiation in MRI)
• Radiofrequency signal pulses are applied which deflects the protons from their equilibrium position
• The pulses are stopped and the protons realign with the magnetic field, releasing energy
• Energy released and time taken to return are measured and used to create the images (vary with molecule and environment).

Question 21

How do fluid and fat appear in these types of MRI images?
T1
T2
STIR

Answer 21

T1- fat bright, fluid dark
T2- fat bright, fluid bright
STIR- fluid bright, fat dark

Question 22

When is a STIR MRI useful and why?

Answer 22

Useful to see oedema because fluid appears bright and signal from fat is suppressed (fat appears dark)

Question 23

What is gadolinium and when is it used?

Answer 23

Chemical element used as a contrast media during MRI. It enhances image clarity and can be injected into a joint or intravenously

Question 24

How does ultrasound work?

Answer 24

High frequency sound waves travel through the patient and are deflected by tissue and tissue planes. The deflected signals are measured by the transducer and analysed to create an image

Question 25

Ultrasound benefits and disadvantages

Answer 25

Good things;
No radiation exposure 
Good at soft tissue 
Useful for imaging tendons and muscles 
Used to locate fluid collections/ haematomas

Bad things;
Need a skilled operator
Poor resolution of deep tissues
Limited use for bone and intra-articular (in the joint) imaging

Question 26

Who are especially sensitive to damage from ionising radiation?

Answer 26

Children and foetuses because they have rapidly dividing cells

Question 27

What is nuclear medicine?

Answer 27

Use radiolabelled biologically active drugs to measure biological activity.
E.g. measure areas of metabolically active bone

Question 28

Why do veins appear dark in the DR?

Answer 28

Blood drains into the veins from the arteries (appear bouncy and hollow) and clots
veins look dark or collapsed

Question 29

Where is the intercostal neurovascular bundle?

What does it consist of?

Answer 29

Beneath each rib

Intercostal vein
Intercostal artery
Intercostal nerve