X-Rays, ECGs & Oximetry

Question 1

What are x-rays used for?

Answer 1

To produce images of the bones and organs in a body

Question 2

In the process of molecules becoming ionised what happens to the x-rays?

Answer 2

As x-rays pass through body tissue they are absorbed by molecules malik them ionised. In this process x-rays lose energy and eventually cannot ionise any more tissue

Question 3

How are x-rays produced?

Answer 3

A heated cathode produces electrons and the potential difference between this an the anion cause the electrons to accelerate towards the anode.
In the anode is a tungsten target, and when the electrons collide wth this, some of the energy converts to x-rays

Question 4

Only a small amount of energy is converted to x-rays. What is the rest of the energy converted to?

Answer 4

Heat

Question 5

What is the formula (with units) used to calculate the current in an x-ray tube?

Answer 5

Current (ampere, A) = number of particles per second (1/second, 1/s) x charge carried by each electron (coulomb, C)
OR
I = N x q

Question 6

What do the electrons gain in an x-ray electron beam?

Answer 6

Kinetic energy

Question 7

What is the unit of potential difference?

Answer 7

Volts (V)

Question 8

What does one coulomb of electric charge gain when it is accelerated through a potential difference of one volt?

Answer 8

One joule of energy

Question 9

What formulae can be used to calculate kinetic energy?

Answer 9

KE = eV
OR
KE = 1/2mv^2

Question 10

What are x-rays?

Answer 10

Electromagnetic waves with a very short wavelength

Question 11

In KE = 1/2mv^2, what do KE, m and v stand for, with units?

Answer 11

KE = kinetic energy (joules, J)
m = electron's mass (kg)
v = velocity of electron (m/s)

Question 12

True or False: KE = ev = 1/2mv^2

Answer 12

True!

Question 13

What is the mass of an electron?

Answer 13

9.1 x 10^-31kg

Question 14

What is the inverse square law?

Answer 14

Area increases with the square of distance so intensity decreases with the square of distance.

Question 15

Which scan produces a 2D image and which scan produces a 3D image?

Answer 15

Conventional x-rays produce a 2D image and CAT scans produce a 3D image (of the internal structure)

Question 16

What do fluoroscope a (which use x-ray images on a screen) all doctors to do?

Answer 16

See real time image of a patients internal condition

Question 17

What are the advantages of an x-ray?

Answer 17

1) X-rays can help give a reliable diagnosis and make sure treatment is fast and accurate
2) X-rays are non invasive (patients do not require operation to see what’s happening in their bodies

Question 18

What are the disadvantages of an x-ray?

Answer 18

1) X-rays can kill and damage living cells

2) Risks are greater for babies and young children, so exposure is kept to the minimum

Question 19

What are action potentials?

Answer 19

They are electrical signals that control the heart muscles

Question 20

What are action potentials generated by and why?

Answer 20

The hearts natural pacemaker in order to make the heart beat at the correct rate to supply the body with needed oxygen

Question 21

What measures the changing electrical signals in the heart?

Answer 21

An ECG (electrocardiogram)

Question 22

What can an ECG show?

Answer 22

If a heartbeat is abnormal and can allow doctors to diagnose any problems with a patients heart

Question 23

What are the five deflections observed in ones heart beat labelled as?

Answer 23

PQRST

Question 24

A normal ECG shows the heart is beating regularly. The pulse rate is the frequency of this signal. What is the formula to calculate this?

Answer 24

f = frequency (hertz, Hz)
T = time period (seconds, s)
f = 1/T

Question 25

The pulse rate is usually given as bpm, what does this mean and what must you do to calculate the frequency?

Answer 25

bpm means beats per minute. In this case, in order to find the frequency, one must multiply it by 60

Question 26

What is the average resting pulse of an adult?

Answer 26

72bpm

Question 27

How does a pulse oximetry measure the patients heart rate?

Answer 27

As the heart beats, the volume of blood in a fingertip varies, and the amount of light passing through the finger also varies. This allows heart rate to be measured.

Question 28

How does a pulse oximetry measure the patients oxygen levels?

Answer 28

The difference between the amount of infrared light and visible light passing through the fingertips depends on how much oxygen the blood is carrying, allowing oxygen content to be calculated.

Question 29

In KE = ev, what do KE, e and V stand for, with units?

Answer 29

KE = Kinetic Energy (joules, J)
e = charge on electron (coulomb, C)
V = accelerating potential difference (volts, V)