Theme 1 : Symposium

Question 1

Ionising radiation waves (3)

Answer 1

X-rays
Gamma rays
U/V light

Question 2

What is the relationship between X-ray absorption and tissue?

Answer 2

Absorption proportional to density of tissue

Question 3

State and Elaborate the 3 X-ray interactions

Answer 3

Transmitted- pass through unaffected/with a lower energy

Absorbed- transfer all energy to matter and not pass through the patient to the film

Scattered- diverted with or without energy loss

Question 4

What are the strengths of radiography?

Answer 4

• Great spatial resolution- especially bone
• Cheap & available
• Easy interpretation

Question 5

What are the weaknesses of radiography?

Answer 5

• Projectional
• Ionising radiation
• Very limited soft tissue visualisation

Question 6

Explain and state the 2 types of resolutions in radiography

Answer 6

Contrast – differentiate between structures of different intensities

Spatial – ability to differentiate between 2 neighbouring structures

Question 7

What are the weaknesses of computed tomography (CT)?

Answer 7

• Ionising radiation
• Limited soft tissue contrast – differentiation is difficult

Question 8

What are the strengths of computed tomography (CT) ?

Answer 8

• Cross-sectional
• Spatial resolution
• Widely available

Question 9

Non Ionising radiation (2)

Answer 9

Ultrasound and MRI

Question 10

What are ultrasounds based on?

Answer 10

production and detection of echoes when probe is on patient

Question 11

What are echoes?

Answer 11

Reflection of beam(s) and occurs at the interface between 2 materials

Question 12

Attenuation

Answer 12

the amplitude and intensity of ultrasound waves - decreases as they travel through tissue

Question 13

What are the interactions of ultrasounds?

Answer 13

Interactions the same as x rays + refraction

Question 14

The More dense the tissue in ultrasounds…

Answer 14

= higher attenuation coefficient (dB/cm at 1MHz)

Question 15

What are the strengths of ultrasounds?

Answer 15

• Non-ionising radiation
• Multiplanar
• Dynamic
• Doppler

Question 16

What are the weaknesses of ultrasounds?

Answer 16

• Operator-dependent
• Can’t see through bone or gas

Question 17

What are the strengths of Magnetic Resonance Imaging (MRI)?

Answer 17

• Non-ionising & Multiplanar
• Exquisite soft tissue contrast
• Reproducible & non-operator dependent

Question 18

What are the weaknesses of Magnetic Resonance Imaging (MRI)?

Answer 18

• Limited availability - slow
• Magnetic field
• Some patients/equipment not suitable – checklist before MRI scan : Pacemaker,
• Intracranial aneurysm, clips will effect the MRI scan and therefore not suitable
• Expensive shielding
• Can be difficult to appreciate calcification or gas

Question 19

State and elaborate the 3 conventional planes of MRI scans

Answer 19

• Axial (transverse) ‘bird’s eye view’ – back towards, front outwards
• Coronal (frontal) – patient facing towards you
• Sagittal (lateral) – front left back right

Question 20

CT in chest drain insertion, what is it used for and how does the need travel to get to the target?

Answer 20

CT is used to guide lung biopsy
Needle travels through air to get to target

Question 21

Ultrasound in chest drain insertion, what is it used for and how does the need travel to get to the target?

Answer 21

used to drain pleural effusions
Needle travels through fluid to get to target

Question 22

Which aspect of the rib would you put your needle?

Answer 22

Inferior aspect of the space, top or bottom of the rib to avoid neurovascular bundle