Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics > Medical > Flashcards

Medical Flashcards

1
Q

What is used to create ultrasound impulses

A

Piezoelectric crystals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How are pulses of ultrasound produced by a transducer

A

Apply an alternating potential difference of high frequency to electrodes which are attached to piezoelectric crystals which causes the crystals to contract and expand repeatedly at the same frequency as the potential difference. This causes mechanical vibrations which produces sound waves over 20000hz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How are ultrasound signals detected

A

The piezoelectric crystals are forced to compress and extend repeatedly so they vibrate due to waves which causes an alternating potential difference at the same frequency as the sound waves and this pd can be measured

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What metal is used in a X-ray tube

A

Tungsten

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens in an X-ray tube

A
  • electrons are emitted from a heated filament
  • they are accelerated over a high potential difference
  • they hit the tungsten anode and decelerate, converting there kinetic energy into an X-ray photon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What’s bremmstrahlung

A

When the X-ray tube emits a continuous spectrum of X-ray radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the maximum kinetic energy of an X-ray

A

The production of the potential difference of the tube and the charge of an electron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What’s the maximum energy of a pd 50kv

A

50keV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do you measure the intensity of the beam

A

The power per unit area

The energy per se one per unit area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are two ways of increasing the intensity of the X-rays

A

1) increase the potential difference in the tube

2) increase the current supplied to the filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does increasing potential difference effect the electrons

A

The electrons have a greater kinetic energy, so higher energy electrons can knock off deeper electrons producting more characteristic spikes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the difference in the energy of e photons if you increase the potential difference

A

They have a higher maximum kinetic energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is intensity and voltage related

A

Intensity is proportional to the square of p.d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does increasing the current do

A

This means the filament will emit more electrons per second and therefore produce more photons per second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens to the energy of the photons if you increase the current

A

The energy will stay the same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the relationship between current and intensity

A

They are proportional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does the blood flow into first in the heart

A

The atrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What do valves do in the heart

A

Prevent back flow of the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does the heart work

A

Blood enters the atria, via veins and the atria contract, squeezing blood into the ventricles, which then contract pushing blood out via the arteries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How are electrical signals passed in the heart

A

Cells in the wall of the right atria send electrical impulses, these are passed to the atrioventricular node which delays the signal for about 0.1 before passing it to the ventricles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How many electrical signals occur per min

A

Around 70

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is an electrocardiograph used for

A

To find out about the condition of the heart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does a cardiogram work

A

Electrodes are attached to the chest and a computer plots the potential difference between them against time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Why do we place electrodes on the chest

A

It’s close to the heart and the limbs at a point where arteries are close to the surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Where on the body shouldn't we connect electrodes to
The right leg as its too far away from the heart
26
How should the patient be during the exam and why
They should be relaxed and still to reduce any unwanted signals
27
How should the leads be treated
They should be shielded in order to reduce the interference from any nearby a.c sources
28
What happens to the signals at the electrodes and what is done to reduce this
The signals are attenuated through the body so they must be amplified by a high impedance amplifier
29
How should you reduce electrical resistance between the contact points
Remove hair and dead skin cells, use a conductive gel and make sure electrodes are securely attached
30
What are the 3 different waves on a electrocardiograph
- P - QRS - T
31
What do the p wave relate to
The signal generate which causes the contraction of the atria
32
What causes the QRS wave
The signal which causes the ventricles to contract
33
How long after the P wave does the QRS wave occur
0.2s
34
What causes the T wave
The ventricles relaxing
35
How long after the QRS wave does the T wave occur
0.2s
36
What's fluoroscopy used for
Create moving images
37
What 3'screens are used in fluoroscopy
Fluorescent screen, photocathode and fluorescent viewing screen
38
What do fluorescent screens do
Thy absorb X-ray photons and emit light
39
What does the photocathode do
It absorbs light and emits electrons
40
What changes the path of electrons in fluoroscopy
Electrodes help to focus electrons to produce and image
41
What's a flat panel detector
An digital way to record X-ray images
42
How do flat panel detectors work
1) X-rays excite the scintillator material which produces light of intensity proportional to the energy of the incident photons 2) photodiode pixels create a voltage proportion to the intensity of light which hits them 3) thin film transistors are used to create a digital signal
43
What are advantages of FTP
- lightweight and compact, convenient to move around - higher resolution - less distortion of the image - easily copied, shared and stored - need less exposure to produce a clear image
44
What are advantages of X-rays
- they have good resolution - produce clear images of bones - CT scans are much quicker than MR scans - CT scan is quicker than MR scans
45
What is an MR machine
A huge super magnet
46
How does an MR scan need to be maintained and why is this a disadvantage
It needs to be cooled by liquid helium and this is expensive
47
What is the magnetic field like during an MR scan
The super magnet creates a uniform magnetic field, and smaller electromagnets create small fields which interfere, creating a gradient of magnetic field strengths
48
What does the magnetic field do to our bodies
If affects the protons (hydrogen nuclei), it makes them align and process around the field
49
What affects the precession frequency
The magnetic field strength
50
What is the precession frequency
The angular speed the protons precess at
51
What happens to the protons after they have a gradiated magnetic field
They have different precession frequencies and hence absorb different frequencies of radiation
52
How are radio waves used in MR scans
Radio frequency coils emit short pulses of radio waves the same frequency as the precession frequency which excites the protons and causes the to change alignment, the protons deexcite and emit the photons
53
How can we change what part of the body were looking at
Change the frequency of the radio waves emitted
54
What image is created from an MR scan
A 2D cross section image
55
How can we enhance the response of different tissue types
Alter the time between impulses
56
What type of molecules should have rapid impulses
Fat molecules
57
What are rapid impulses used to image
The internal structure of the body
58
What molecules should you allow more time for
Watery molecules
59
What are slow Impulses used to look at
Diseased areas
60
What are advantages of MR scans
- no known side effects - an image can be made for any slice in any orientation from a single scan - high quality images of soft tissue including the brain - can change contrast to investigate different situations - it gives real time images
61
What are disadvantages of MR scans
- the imagine of bones is poor - people feel claustrophobic - scans can be noisy and take a long time - can't be used on people with pace makes or metal impacts - scanners are very expensive
62
Which is the safest scan to use
Ultrasound or Mr
63
What scan is best for bones
X-rays
64
What two scans can be used to look at soft tissue and which is better
MR Is best but X-rays work as well
65
Which is cheapest and most portable
Ultrasound then X-rays
66
What do medial tracers do?
They are used to show tissue or organ structure and function
67
What three things to eh use for tracers
Technetium-99m Iodine-131 Indium-111
68
How are the tracers put into the body
They're bound to substances the body uses and then injected or swallowed

Physics (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions