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Year 1 Medicine > Imaging > Flashcards

Imaging Flashcards

1
Q

How does an x-ray work?

A

A beam of x-rays are projected towards the patient. Some of these are absorbed by the patient and the rest that pass through the patient are captured by a detector, which then creates a digital image.

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2
Q

What is gamma radiation?

A

Gamma rays that have occurred due to the radioactive decay of unstable isotopes.
360 degrees of rays that can’t be switched off, have to wait for the half life of the chemical to pass. Higher frequency than x-rays.

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3
Q

What is an isotope?

A

A radioactive element involved in delivery

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4
Q

What is a ligand?

A

A pharmaceutical element involved in binding

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5
Q

Name some properties of an ideal isotope?

A

Gamma emitter
Half life similar to time of examination
Easily bound to pharmaceutical component.
Radionuclide readily available at the hospital site
Radiopharmaceutical simple to prepare

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6
Q

What is the most common isotope currently used in hospital?

A

Technecium99

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7
Q

What is SPECT?

A

Single Proton Emission Computed Tomography
Gamma cameras rotate around area of interest.
Specifically effective for cardio or neurological scanning.

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8
Q

What is PET?

A

Positron Emission Tomography
Form of molecular imaging that uses radionuclides that decay by positron emission ( proton - neutron + positron)
Used to image biologically interesting processes.

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9
Q

Name some common PET radionuclides and their half lives?

A 
18F - 110minutes
68GA - 68minutes
11C - 20minutes
13N- 10minutes
15O - 2minutes
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10
Q

What is the main risk of radiation?

A

Ionising radiation inducing fatal cancer

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11
Q

What is the benefit of using radiation in imaging?

A

Allows for earlier diagnosis , management of change and treatment.

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12
Q

What are the 5 main types of imaging used in hospitals today?

A 
Plain radiographs (x-ray)
Barium Studies
CT
MRI
PET
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13
Q

What is barium sulphate?

A

A radio-opaque contrast used for outlining the gastrointestinal tract.

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14
Q

How does barium outline the GI tract?

A

It has a high atomic number which mean sit absorbs more photons than its surroundings. This makes it appear white on an x-ray.

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15
Q

Describe the different types of barium study and the tissues that each highlights?

A

Barium swallow and meal - oesophagus, stomach and duodenum

Barium follow through - small bowel

Barium enema - large bowel

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16
Q

What is the function of cross sectional imaging?

A

Allows the initial diagnosis and staging of disease, monitoring in response to treatment, evaluation of residual mass after treatment, recognition of complications and ability to check for disease relapse.

17
Q

Describe how a computed tomography works?

A

X-rays used to produce a digital image of a slice of tissue, usually in the axial plane, using computing to create the image.

18
Q

What are the types of contrast agents that can be used before a CT to highlight certain structures?

A

Oral - Iodine based contrast used to outline GI tract

Intravenous - omnipaque iodine based contrast used to outline the blood vessels or the vascularity of different tissues.

19
Q

What factors are important when diagnosing and staging cancers?

A 
Position of tumour
Depth of its penetration 
Relationship with adjacent structures
Involvement with regional lymph nodes
Presence of distant metastases
20
Q

What are the doses of radiation of a chest, abdominal, and pelvic CT?

A

Chest = 8msv

Abdomen & Pelvis = 10msv

21
Q

What is the ALARA principle?

A

As Low As Reasonably Achievable
Must ensure whether the examination is necessary
Adequate clinical information is required before the scan can take place.
Repeat examinations are avoided.

22
Q

What is MRI?

A

Magnetic Resonance Imaging - strong magnetic field aligns all the protons in the body in one direction.
Radiofrequency pulse displaces protons and images created by displaying the time taken for protons to relax back to their original alignment.

23
Q

What are the benefits of MRI?

A

Excellent bone soft tissue detail
Vessels can be demonstrated
Good for brain, spine and musculoskeletal
Abdomen, pelvis and cardiac are also well demonstrated on an MRI.

24
Q

What are some disadvantages of MRI?

A

Claustrophobic and noisy
Motion Artefact
Cannot image patients with pacemakers or aneurysm clips

25
Q

What is the purpose of screening?

A

Diagnose disease at an earlier stage before symptoms are visible.
Cancer is easier to treat and more likely to be curable.

26
Q

What are the principles of screening?

A

Must be an important health problem
Test must be acceptable to the population
Must beg a latent form of the disease
There must be a treatment available for the condition
Test should cause no harm
Test should have high specificity and high sensitivity.

27
Q

What is sensitivity?

A

How many patients with the disease test positive.

28
Q

What is specificity?

A

How many patients without the disease test negative.

29
Q

What is a positive predictive?

A

How many patients who test positive have the disease

30
Q

What is a negative predictive?

A

How many patients who test negative don’t have the disease.

31
Q

What is the rationale for imaging?

A

Faster diagnosis
Roadmap for procedures/treatments
Physical examination is unreliable
Screening

32
Q

What is an x-ray?

A

Electromagnetic packet of energy with an extremely short wavelength between 0.1 and 10 nanometers.

33
Q

What is Attenuation?

A

Process by which radiation loses power as it travels through matter and interacts with it.

34
Q

How does atomic number, density and thickness affect attenuation?

A

Atomic number - increase
Density - increase
Thickness - increase

35
Q

What is ultrasound imaging?

A

Uses high frequency sound pulses to create an image. The probe is placed directly on the skin and jelly is used to get rid of any gas bubbles.

36
Q

What is the rationale for ultrasound imaging?

A

Cheap
Portable
No radiation
Great for soft tissues

37
Q

What is radiation?

A

The process of emitting energy in the form of particles or waves.

Year 1 Medicine (37 decks)

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