Topic 6 (Medical Imaging Technology)

Question 1

What is the 4 main component that simple x ray system consist of?

Answer 1

1) High Voltage generator
2) An X- Ray tube
3) Collimator
4) Intensifying screen and film

Question 2

How does the X ray machine work?

Answer 2

it works by generating x rays from the x ray tube and filtering low energy x ray that will not penetrate the body and the collimator will focus the x ray onto and through the body into the screen/film

Question 3

What is A CT? ( Computed tomography )

Answer 3

it is a machine that generates anatomical imaging which is digitally reconstructed

Question 4

How does a CT work?

Answer 4

1) There is a microcomputer dedicated to control the voltage in kV and beam current in mA

2) The High dc power supply drives the x ray tube that can be mechanically rotated along the circumference of the machine

3) the x ray pass through the patient who is lying in the Centre of the tube

4) imaging takes place at different angles with as many as 1000 detectors fixed in the circumference of the tube

Question 5

How is the imaging of CT produce?

Answer 5

it uses a Back projection reconstruction where they add the attenuation values of the image at different angles multiple times and normalize by subtracting by 9 than divide 3

Question 6

What is MRI? ( Magnetic resonance imaging )

Answer 6

It is a medical imaging technique that uses radiology to visualize detailed internal structures

Question 7

How does MRI work?

Answer 7

it uses a powerful magnetic field to align some of the atoms in our body and than uses radio frequency to alter the alignment of the magnetization

Question 8

What is MRI good for?

Answer 8

it provides good contract between different soft tissues of the body and is more useful to scan brain muscle , heart and cancer

Question 9

What is the 4 Advantages of using MRI?

Answer 9

1) uses non ionizing radiation
2) Ability to image in any plane
3) very low incident of side effects
4) can diagnose, visualize and evaluate various illnesses

Question 10

What are the 4 Basic Components of MRI?

Answer 10

1) A magnet that produce very power uniform magnetic field

2) Gradient magnet lower in strength

3) Equipment to transmit Radio frequency

4) A powerful computer system which translate the signals transmitted by the magnetic coils

Question 11

What is an ultrasound scanner? (6 points)

Answer 11

1) any acoustic wave with frequencies above 20kHz
2) typical ultrasound use in medical scan are from 1Mhz to 15Mhz
3) non invasive
4) safe for human body
5) it is more sensitive to soft tissues
6) the wave enter body and reflects with different interfaces in the body to produce image

Question 12

What are the 2 typical components in ultrasonic wave?

Answer 12

1) Phase front
2) Plane waves

Question 13

Why do we need to study reflection of waves at interfaces in ultrasonic scanners and what are the 2 points?

Answer 13

Because it is basic technical understanding of the imaging instrumentation

1) The angle that the reflected wave has as it leaves the interface

2) the angle that the transmitted waves take as it go through into a new region

Question 14

What are the 3 characteristics of reflection coefficient?

Answer 14

1) if Z1=Z2, there is R=0 meaning no reflection of wave at interface.

2) if Z2>Z1, R will be a positive meaning the reflected wave are in phase at the interphase

3) if Z2<Z1, R will be negative meaning the incident and reflection have a 180 degree phase difference

Question 15

What is the 3 requirements of imaging principle and instrumentation?

Answer 15

1) Generation of an ultrasonic beam
2) Reception of a returning echo
3) Processing of the signal for display

Question 16

What is usually used for generation of ultrasonic beam?

Answer 16

1) a piezoelectric device like crystalline materials is used

Question 17

How does the piezoelectric material work?

Answer 17

when a voltage is applied across the conducting plates the molecules twist and turn around to align with the electric fields (+ and -) hence it thickens. if the polarity reverse the molecules twist and turn back the opposite side which decreases the thickness

Question 18

Which part of the piezoelectric device generate the sound waves?

Answer 18

the back and forth flipping of the polarity and molecules cause expansion and contraction which creates mechanical vibration producing sound waves

Question 19

What else can piezoelectric device do?

Answer 19

it cause produce voltage if you mechanically deform the crystal

Question 20

How does the piezoelectric transducer work in ultrasonic scanner?

Answer 20

1) voltage generator send short pulse to piezoelectric transducer inducing a ultrasound wave into the body
2) ultrasonic energy travels into tissue and is reflected at tissue boundaries which cause echo
3) the echoes will travel back to the piezoelectric transducer and the generator is already off but the echo can create an oscillation in the transducer again