alternative imaging modalities

Question 1

what can be visualised with CT

Answer 1

soft tissue and bony anatomy in 3D

Question 2

how can soft tissue contrast be improved in CT

Answer 2

IV iodinated contrast

Question 3

disadvantages of CT 2

Answer 3

Expensive
Artefacts from metal

Question 4

what is a hounsfield unit?

Answer 4

a value of density given to voxels

Question 5

what is the hounsfield unit for air?

Answer 5

-1000 = black

Question 6

what is the hounsfield unit for fat

Answer 6

-100 to -60

Question 7

what is the hounsfield unit for water

Answer 7

0
used to calibrate machine

Question 8

what is the hounsfield unit for dense bone

Answer 8

+1000 = white

Question 9

what does windowing do?

Answer 9

Alters the levels of densities visualised to optimally look at specific tissues

Question 10

what is the window level?

Answer 10

value at centre of range of densities

Question 11

what is the window width

Answer 11

range of values selected to view tissue

Question 12

what does MRI stand for?

Answer 12

magnetic resonance imaging

Question 13

how does MRI work

Answer 13

Uses magnetic field, radiofrequency pulses and hydrogen protons (within water molecules) within the body to produce images

Question 14

MRI has different sequences what is T1 good for?

Answer 14

anatomy - fat is white

Question 15

MRI has different sequences what is T2 good for?

Answer 15

pathology - fat and fluid is white

Question 16

advantages of MRI 2

Answer 16

No ionising radiation
Very good soft tissue imaging

Question 17

disadvantages of MRI

Answer 17

Multiple contraindications

Long scan time - higher cost, less availability

Claustrophobia - smaller hole that CT

Question 18

contraindications for MRI

Answer 18

Pacemakers, orbital foreign bodies, artificial heart valves, surgical clips

Question 19

how does ultrasound work

Answer 19

High frequency sound waves used to produce images

Question 20

ultrasound is good for assessing what?

Answer 20

superficial structures

Question 21

advantages of ultrasound 3

Answer 21

No ionising radiation
Real time imaging
Assess blood flow

Question 22

disadvantages of ultrasound 4

Answer 22

Operator dependant

Cant penetrate bone - deep pathology may be missed

Only superficial structures seen

Can be difficult to interpret

Question 23

name 3 types of nuclear medicine

Answer 23

PET - positron emission tomography

SPECT - single photon emission CT

scintigraphy

Question 24

how does nuclear medicine work

Answer 24

Pt injected with radiopharmaceutical which when decays emits particles which are picked up on a gamma camera

Increased activity = hot spot

Reduced/no activity = cold spot

Question 25

advantages of nuclear medicine 3

Answer 25

Can superimpose over other imaging Highly sensitive Can asses function

Question 26

disadvantages of nuclear medicine 3

Answer 26

Poor resolution Poor specificity - hot spot could be malignancy, infection, inflammation Very high radiation dose - higher than CT