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Medical Sciences - Anatomy & Physiology - Level 4 > Introduction: Medical Imaging > Flashcards

Introduction: Medical Imaging Flashcards

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USMLE® Step 1 flashcards
1
Q

What is radiographic anatomy?

A

The study of the structure and function of the body using medical imaging techniques.

Advances include availability and speed of scans.

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2
Q

Five main modalities

A

Plain conventional radiography (X-Ray)

Ultrasound Scan (USS)

Computed Tomography (CT)

Magnetic Resonance Imaging (MRI)

Nuclear Imaging

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3
Q

Why is it important?

A 
Non-invasive
Helps with diagnosis
Disease monitoring
Research
Teaching
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4
Q

Conventional Radiography

X-Rays

A

2D imaging

Highly penetrating beam of X-rays which penetrate the individal and an image is produced on a detector.

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5
Q

How does convention radiography / x-rays work?

A

Different intensities on the film highlight tissues of differing densities.

Highly dense tissues absorb more radiation.

Dense substance - Radiopaque

Less dense - Radiolucent

Contrast is sometimes used. e.g. in an angiogram

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6
Q

Differing Densities - Colours

Air

A

Black

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7
Q

Differing Densities - Colours

Fat

A

Dark Grey

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8
Q

Differing Densities - Colours

Soft tissue / fluid

A

Grey

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9
Q

Differing Densities - Colours

Bone

A

Light grey

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10
Q

Differing Densities - Colours

Metal

A

White

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11
Q

Advantages of X-ray

A

Cheap
Portable
Quick and easy to use
Combined with contrast

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12
Q

Disadvantages of X-ray

A

Exposure to Radiation
Operator dependent
2-dimensional Image
Precautions pregnancy / children

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13
Q

Ultrasound Scan (USS)

A

USS uses technique that visualises superficial or deep structures in the body by recording pulses of ultrasonic waves that reflect off tissues.

Probe placed on patient’s skin with lubricating jelly.

Sound waves emitted fro the probe hit body structures of tissues

Sound waves reflect off the structures. Different tissues will reflect at differing frequencies and times.

Top of Image closest to probe.

Increased density = whiter image (e.g. bone)

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14
Q

Advantages of Ultrasound Scan (USS)

A 
Non-invasive
Cheap
Portable
No ionising radiation
Produce real-time images (doppler)
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15
Q

Disadvantages of Ultrasound Scan (USS)

A

Unable to cross a tissue-gas or tissue-bone boundary.

Operator dependent

Difficult in patients with larger body size.

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16
Q

Uses of Ultrasound Scan (USS)

A

Pregnancy
Abdominal Aortic Aneurysm monitoring
Deep Vein Thrombosis diagnosis
Echocardiogram (heart ultrasound).

17
Q

Computed Tomography (CT)

Description

A

Hounsfield (1972)

X-ray beam and a detector system move through an arc of 360 degrees

Circular doughnut known as the gantry consists of both the beam and the detector.

Gantry rotates and a cross-sectional image is obtained.

Detector is able to measure the intensity of radiation passing through the individual.

Computer system analyses the different intensities and a 3D image is reconstructed.

18
Q

Appearance of CT scan

A

High absorption such as bone appear white and those with little absorption appear black.

Contrast medium can be used to better visualise organs.

CT scans are viewed by looking up a patients feet.

19
Q

Advantages of Computed Tomography

A

Able to generate a 3D image

Able to utilise contrast

Relatively quick

Non-invasive unless IV contrast is used

20
Q

Disadvantages of Computed Tomography

A

Significant radiation exposure

Not easily portable

Requires patients to be still

Relatively expensive

Reactions to contrast

21
Q

Magnetic Resonance Imaging Description

A

Non-invasive imaging which does not use ionising radiation

Magnetic field

Human body up of mostly water

Protons (hydrogen ions) line up within the magnetic field.

Radio frequency pulsed waves are emitted which cause the protons to misalign

22
Q

Magnetic Resonance Imaging (MRI)

How it works

A

As protons return to their aligned position they release energy which can be measured.

Different tissues emit different signals

23
Q

Why we use MRI

A

Scanners are useful for the visualisation of soft tissues.

Intrinsic details of different modalities of MRI such as T1 weighted and T2 weighted

Looking up a patients’ feet

24
Q

Advantages of MRI

A

3D images are created

Differentiating tissues

No radiation exposure

Safe in pregnancy / children

Non-invasive unless contrast is use

25
Q

Disadvantages of MRI

A

Very expensive

Limited resources

Time consuming

Patient has to remain very still for long periods of time

Very loud

Small enclosed space - impossible for claustrophia

Contrast reactions

Metallic impacts are contra-indicated such as metal plates of pacemaker.

26
Q

Nuclear Imaging

Description

A

Nuclear imaging provides metabolic and functional information of the organs.

Small dose of radioactive isotope is injected

Tissues have varying specificities for the different chemicals.

Uptake of compound dependent on the organ.

27
Q

Nuclear Imaging

Types

A

Poistron emission tomography (PET)

Single photon emission computed tomography (SPECT)

28
Q

Nuclear Imaging

PET uses

A

Staging of cancer

Evaluation of an indeterminate lesion

Assessing response to therapy

Biopsy

29
Q

Nuclear Imaging

Advantages

A

Early diagnosis

Accurate

30
Q

Nuclear Imaging

Disadvantages

A

Very expensive

Very limited resources in the UK

Requires radiation

Allergic reactions

Time consuming

31
Q

Radiation doses

Choosing a dose

A

Radiation does compared against background radiation or number of chest X-rays

32
Q

Radiation doses

Measured in

A

Millisievert (mSV)

33
Q

How much background radiation a year?

A

2.7 mSV

34
Q

How much radiation emitted from a Chest X-ray

A

0.04 mSV

35
Q

How long to get rid of radiation?

A

Dependent on half-life

Medical Sciences - Anatomy & Physiology - Level 4 (4 decks)

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