P3.2 X-rays And ECGs Flashcards
How does an x-ray machine produce x-rays?
A cathode is heated until they are released through thermionic emission. The electrons accelerate towards the anode by a potential difference between the cathode and anode. When they collide with the spinning anode, some of the kinetic energy are released as x-rays.
How can you calculate the KE of each electron?
Kinetic Energy= electronic charge * accelerating potential difference
KE= e*v
How can you calculate the size of the current produced?
Current= Number of particles per second * charge on each particle I= N*q
What is the danger of x-rays?
They can remove electrons from molecules in living cells-leaving them as ions. This means cells can be destroyed, leading to cancer.
What is the inverse square law relating to intensity of radiation?
The inverse square law states that if you move twice as far from the radiation source as you preciously were, then the radiation will be 2 squared times less intense.
How does the thickness of a material affect the amount of x-rays it absorbs?
The denser or thicker a material is the more x-rays it absorbs.
What materials can be used to reduce peoples exposure to x-rays?
Lead or Concrete
How does a fluoroscope work?
X-rays are fired through a patient onto a fluorescent plate. Where less is received there will be a contrast, which lets to doctor view a moving image of the patients body.
What is a CAT scan (Computerised axel tomography)?
An x-rays rotates around the body and is picked up by thousands of detectors. A computer works out how many x-rays are absorbed and creates a slice of a patients body.
What are the benefits of x-rays?
- They are the clearest and more accurate form of diagnosis.
- Its better to use x-rays than to risk using the wrong treatment.
- Its non-invasive.
What are the drawbacks of using x-rays?
They are ionising
They can cause cancer
What is the resting potential?
The potential difference across the cell membrane of a muscle cell.
What is an action potential?
The increase in potential difference when an electrical impulse travels along the muscle cell.
What is an ECG?
An ECG (electrocardiogram) measures the action potentials across the heart.
How do you work out heart rate?
Frequency = 1/ time period (s)
What are the 3 main stages of a heartbeat (often referred to as P, QRS and T)?
P- The atria contracting
QRS- The ventricles contracting
T- The ventricles relaxing.
How is the ECG recorded?
Using electrodes on the body which pick up the action potentials travelling along the skin.
What is a pacemaker?
A device that is fitted to the heart to produce action potentials to make the heart beat if your body is no longer able to do it.
What is a pulse oximeter?
A device that is used to quickly measure your pulse and blood oxygen saturation levels.
How does a pulse oximeter work?
It has emitters of IR and red light in the top and a detector on the bottom. If lots of IR and little red light is detected, you blood oxygen saturation is low as oxygenated blood absorbs IR but nor red light. If little IR and lots of red light is detected, your blood saturation is high.
