Imaging

Question 1

What are X-rays

Answer 1

Electromagnetic packet of energy short wavelength

Question 2

What imaging uses radiation ?

Answer 2

X-rays
Barium
CT

Question 3

What imaging’s don’t use radiation?

Answer 3

Ultrasound

MRI

Question 4

Describe how X-rays work

Answer 4

Inner shell is of electrons is very important. Uses PACS (picture archiving communication system). Electrons are emitted from the cathode with a high velocity and crash into the anode releasing X-rays. Attenuation is the process by which X-rays loose there power as they travel through matter, this increases as the density increases i.e. X-rays pass straight through air but cannot pass through tooth. Dense material i.e. tooth will appear white on the image. X-ray images are produced by a three layer film, silver halide between two luminescent screens. X-rays clump together on silver hide and generate light.

Question 5

What is ultrasound?

Answer 5

Sound pulses of high frequency

Question 6

Where are ultrasounds used?

Answer 6

Used in image guidance biopsy’s.

Question 7

Where are barium imaging used?

Answer 7

Used in barium swalling and meal examinations.

Causes bowel disturbances and colonic perforation at enema

Question 8

What is the contrast agent in barium examination?

Answer 8

Contract agent i.e. Barium sulphate radio-opaque.

Question 9

Describe how barium studies work

Answer 9

Used to outline the GI tract, Barium absorbs more X-rays that surrounding tissue and so appears white. In X-rays more dense tissue appears white.

Question 10

What are CT?

Answer 10

Rotating X-rays

Question 11

What are CTs used for?

Answer 11

Used for imaging trauma, cancer, staging cancer, monitoring treatment, guidance in procedures, bony detail. They are the mainstay for cancer imaging

Question 12

What is the contrast used on CT?

Answer 12

Contract agent i.e. iodinated Contrast (given orally or in IV but IV harms kidneys)

Question 13

Describe how CTs work

Answer 13

As X-rays (A group of photons) pass through the tissue it losses photons (some are absorbed, the denser the tissue the more X-rays or photons that are absorbed) , the number of photons that has been lost can be detected by a scanner. It uses pixels and voxels. Hounsfield unit of water is zero and then all other structures (i.e. bone or blood or fat) are given values relative to that.

Question 14

What is MRI?

Answer 14

Magnetic fields and radiofrequency pulses

Question 15

What is MRI used for?

Answer 15

Used for imaging the brain spinal cord, bony details, soft tissue. Pass makers cannot be imaged. MRIs are taken before a biopsy for prostate cancer but not for kidney

Question 16

What contrast is used in MRI?

Answer 16

Contract agent i.e. gadolinium DTPA

Question 17

How do MRI work ?

Answer 17

Strong magnetic field aligns protons in one direction, then radiofrequency pulses displace proton and the image is created by the movement of protons to ordinal position. Different tissue will have a different return time due to varying weight. Heavier will return first.

Question 18

What unit is radiation measured in?

Answer 18

A sievert

Question 19

What happens when ionising radiation hits healthy cells?

Answer 19

Cell damage

Question 20

How can exposure to radiation be minimised?

Answer 20

Firstly, is by keeping your distance, as the distance from a radiation source doubles, the exposure rate decreases by a factor of four. Minimising the time of contact also helps to protect you. Wearing or use of a shield will also help protect you

Question 21

What are the ALARA principles?

Answer 21

as low as reasonably achievable

Question 22

What is screening?

Answer 22

Used to diagnose conditions at early stages

Question 23

What makes a disease suitable for screening?

Answer 23

Disease that are suitable for screening have to be important health problem, have a latent stage of disease, there must be a test or examination for the condition, and treatment, facilities for diagnosis and treatment. Test should detect disease at an early stage where treatment can alter outcome Test should cause no harm. Test should have high sensitivity and specificity. Benefit to the individual and the population should outweigh the cost.

Question 24

What cancer screening programs are there in the UK?

Answer 24

Breast cancer
Bowel
Cervix
lung in development.

Question 25

What are the three types of molecular imaging?

Answer 25

Radionuclide imaging 
SPECT 
PEP
MRI 
Optical imaging

Question 26

What is radionuclide imaging?

Answer 26

A radiopharmaceutical is injected into a patient it produces gamma rays. These gamma rays are detected by a lead collimator which passes the information to a gamma camera which then sends info the PACS system (digital storage of images). A radiopharmaceutical element is a radioactive and pharmaceutical element that are attached together.

Question 27

What is SPECT

Answer 27

Single photon emission computed tomography is also used. This is the CT version of nuclear medicine. Gamma cameras rotate around the area of interest. This is routinely used for brain and cardiac studies. This can be used to support a diagnosis of Parkinson’s or Alzheimer’s.

Question 28

What is PET?

Answer 28

A trace (molecules) is tracked through the body. The chemical causes positron emitted and comes into contact with an electron and cancel each other out producing 2 gamma rays which are sent in opposite directions and are then detected by the machine. F18 is used because it has a good half-life and it can easily bind to Fluro deoxy glucose. The glucose will be taken up but the tissue will retain the glucose rather than secrete it. They are not used in biopsies or in detecting distant metastasis. A cyclotron is used to produce PET images it is basically a particle accelerator. Cancer will have a large uptake and therefore will show up in the imaging. Excessive uptake will start before there is any abnormality can be seen.

Question 29

What makes an ideal isotope?

Answer 29

half life that is similar to the length of the examination, it need it to release gamma rays or a sufficient energy. It should be readily available and easily bound to a pharmaceutical component. It should be simple to prepare and have be eliminated in a similar length as the half-time.

Question 30

What is the most common isotope?

Answer 30

99m Technecium