CT, MRI and nuclear medicine

Question 1

What is a 3D X-ray adaptix?

Answer 1

• Series of low dose 2D images taken from different positions to build a 3D image using digital tomosynthesis

Question 2

What is a CT?

Answer 2

• Computed tomography
• Produces multiple, highly detailed cross sectional digitalised radiographs
• Can use iodine or barium compound agents for contrast

Question 3

What are the H&S risks for a CT?

Answer 3

• Uses ionising radiation for X-rays
• Mich higher doses of X-rays than conventional radiography

Question 4

What are CT scans good for?

Answer 4

• Imaging skeletal system
• Less prone to movement blur
• Produces better differentiation between soft tissues and fluid than conventional radiography

Question 5

What are the limitations of an CT?

Answer 5

• Images of brain and spinal cord not as good as MRI
• Ionising radiation
• Sedation/GA required
• More expensive than X-ray, but cheaper than MRI

Question 6

How does an MRI work?

Answer 6

• Magnetic fields align all protons in the same direction
• Radiowaves make protons turn on their side
• Radiowaves are then turned off and protons turn back, which emits radiowaves
• Body’s hydrogen atoms line up with the magnetic field and radiowaves cause reorientation of hydrogen ions
• When radiowaves are turned off, hydrogen ions transmit radiowaves which are detected and turned into an image

Question 7

What is time of flight angiography?

Answer 7

• Sequence of radiowaves that allow detection of blood flow

Question 8

What does MRI contrast media do?

Answer 8

• Alter the time taken for hydrogen atoms to realign after radiowaves stop, which improves the visibility of particular tissues
• Gadolinium given IV

Question 9

What are the H&S risks for MRI?

Answer 9

• Strong magnetic field, so no ferrous metal instruments/objects allowed
• Care if personnel have metal implants or old style pacemakers

Question 10

When are MRIs used?

Answer 10

• Brain and spinal cord disease
• Neoplasia
• Inflammation
• Planning for surgery

Question 11

What are the limitations of MRI?

Answer 11

• Time consuming
• Noisy
• Magnets, so no metal allowed in vicinity
• Expensive
• Show everything

Question 12

• What is nuclear medicine?

Answer 12

• Gamma cameras capture and form images from the radiation emitted from radiopharmaceuticals
• Two types: Scinitgraphy and position emission tomography (PET)

Question 13

What is scintigraphy?

Answer 13

• Gamma ray emitting radioactive isotope is injected IV

Question 14

What are the H&S risks for scintigraphy?

Answer 14

• Radiation risk
• Use of radiopharmaceuticals, so licensed needed for keeping substances and accumulation and disposal

Question 15

When is scintigraphy used?

Answer 15

• Detection of tumours
• Used to detect inflammation
• Portosystemic shunt

Question 16

What are the limitations for scintigraphy?

Answer 16

• Lack of anatomical detail
• Subjective
• Affected by movement
• Time consuming
• Expensive