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Forensic Anatomy - Forensic Significance > Imaging Modalities > Flashcards

Imaging Modalities Flashcards

1
Q

Why is William Rontgen important?

A

Discovered Xray radiation

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2
Q

Why is John Halls-Edwards important?

A

First medical use of Xrays

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3
Q

What type of radiation is in Xrays?

A

Electromagnetic

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4
Q

What is the wavelength of X rays?

A

0.01-10 nm

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5
Q

What are the biological properties permitting Xray imaging?

A

Different tissues absorbs Xrays at different rates.
Cause excitation of atoms

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6
Q

What is different between excited vs non-excited atoms?

A

Excited atoms enter reactions not available to non-excited atoms

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7
Q

What can long term exposure to or high dosages of x rays lead to?

A

Somatic or genetic changes.

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8
Q

What does more absorption in X rays result in?

A

White on image

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9
Q

What type of tissue appears white?

A

High density tissue

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10
Q

Give an example of high density tissue

A

Bone

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11
Q

How does low absorption appear on x ray?

A

Black

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12
Q

What does black on an x ray indicate?

A

Low density tissue

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13
Q

Give examples of low density tissue

A

Lungs, air spaces

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14
Q

How does intermediate absorption appear on X ray?

A

Shades of grey

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15
Q

What type of tissue has intermediate absorption/appear grey on x ray?

A

Intermediate density tissue

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16
Q

Give examples of intermediate density tissue.

A

Muscles, some connective tissue (e.g. adipose)

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17
Q

What is important to remember when interpreting an x ray?

A

2D image of 3D space

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18
Q

What tools can be used to help interpret an x ray?

A

Superimposition
Several angles
Colour differences

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19
Q

What type of structures can be seen in an x ray?

A

Normal or abnormal
Calcifications
Tumours/neoplasias
Infections (e.g., pneumonia)
Foreign objects

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20
Q

What can absences of structures in x rays indicate?

A

Air spaces
Pneumo-/hemo-thorax
Fractures

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21
Q

When were CT scans developed?

A

1967

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22
Q

Who developed CT scans?

A

Sir Godfrey Houndsfield

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23
Q

When was the first medical use of a CT scan?

A

1971

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24
Q

What are CT scans used for?

A

Non-invasive imaging and diagnosis

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25
Q

What can CT scans help us do?

A

3D reconstruction of injuries
3D printing of structures for surgical planning

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26
Q

How do CT scans work?

A

X rays from multiple orientations
Computer sums or stacks a complete image

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27
Q

What are the biological properties of CT scans?

A

Same as Xray but at higher doses

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28
Q

What are different types of CT scans?

A

Sequential CT
Spiral CT
Electron beam tomography
Dual energy CT
CT perfusion imaging
With or without contrast

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29
Q

What is attenuation?

A

X rays transmitted - x rays absorbed by body

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30
Q

Differentiate between high and low density tissue in CT scans.

A

High - absorbs more radiation and less detected by scanner; brighter/white
Low: absorbs less radiation and greater signal detected by the scanner; grey to black

31
Q

What is the orientation of a CT scan?

A

Looking superiorly/cranially

32
Q

What does RALP mean in CT scans?

A

Right, anterior, left, posterior

33
Q

What structures can be seen in a CT scan

A

Normal or abnormal
Calcifications
Tumours/neoplasias
INfections
Foreign objects
bleeding

34
Q

What can structure absences indicate in CT scans?

A

Air spaces
Fractures
Pneumo-/hemo-thorax

35
Q

Who invented MRI scans?

A

I. I. Rabi

36
Q

When were MRI scans invented?

A

1930s

37
Q

When did MRIs become common for soft tissue investigations?

A

1980s

38
Q

When did MRIs begin to be used in medical settings?

A

1970s

39
Q

Describe how MRI scans work

A

Images H2O containing tissues
Hydrogen protons have magnetic poles
Without a magnetic field poles align randomly
Turn on magnet - poles line up
Send a radio transmission to disrupt poles
Disruption causes pole switch
Turn off RT and pulse re-emitted
Turn off magnetic - poles return to unaligned position
Different tissues have different return rates
Measuring difference = image processing and reconstruction

40
Q

What are the three types of weight settings for MRIs?

A

T1, T2, Flair

41
Q

What does weighting mean in MRI?

A

Images will appear with different densities with different weight settings

42
Q

What differences in weights of MRIs result in the different densities?

A

Based on length, repetition, and strength of radio transmission pulses

43
Q

What does white indicate in a T1 weighted image?

A

Fat
Protein rich fluid

44
Q

What does white indicate in a T2 weighted image?

A

Water content e.g. inflammation
Tumour
Haemorrhage
Infection

45
Q

What does intermediate colouring indicate in a T1 weighted image?

A

Gray spinal matter darker than white

46
Q

What does intermediate colouring indicate?

A

White spinal matter darker than gray spinal matter.

47
Q

What does dark colouring indicate in a T1 weighted image?

A

Bone
Air
Water content e.g. inflammation, tumour, hemhorrage

48
Q

What does dark colouring indicate in a T2 weighted image?

A

Bone
Air
Fat

49
Q

What are the three anatomical planes in which MRI can produce images?

A

Sagittal, coronal, transverse

50
Q

How do you orient yourself in transverse MRI views?

A

RALP

51
Q

Describe how CSF appears in each MRI weight.

A

T1: Dark
T2: Bright
Flair: Dark

52
Q

Describe how white matter appears in each MRI weight.

A

T1: Light
T2: Dark grey
Flair: Dark grey

53
Q

Describe how the cortex appears in each MRI weight?

A

T1: Gray
T2: Light gray
Flair: light gray

54
Q

Describe how fat within bone marrow appears in each MRI weight

A

T1: Bright
T2: Light
Flair: Light

55
Q

Describe how inflammation appears in each MRI weight?

A

T1: Dark
T2: Bright
Flair: Bright

56
Q

What to determine when interpreting an MRI.

A

Body region
Orientation
Weighting

57
Q

When are MRI scans used medically?

A

Anywhere contrast resolution is required (use tracer or dye to enhance)
Soft tissue imaging

58
Q

What can be determined in MRI soft tissue imaging?

A

Differentiates between muscle, water, fat
Tumours versus healthy tissue
Rupture of structure

59
Q

What are the two types of forensic uses of medical imaging?

A

Antemortem
Postmortem

60
Q

What can antemortem medical imaging help with?

A

Detect injury
Document injury

61
Q

How can medical imaging be used postmortem

A

Virtual autopsy

62
Q

Why might a virtual autopsy be used?

A

Healthcare worker safety
Accommodate religious observance where possible
Can be sufficient but largely ancillary to full autopsy

63
Q

What are the two types of post mortem medical imaging

A

PMCT - post mortem computed tomography
PMMR - post mortem magnetic resonance

64
Q

How do postmortem exams work in Australia?

A

PMCT is the primary exam
Followed by traditional autopsy

65
Q

How do postmortem exams work in Germany?

A

PMCT is secondary exam
At the order of the legal authority
Prosecutor
For homicides or malpractice only

66
Q

How does the forensic pathology service use PMCT?

A

All individuals brought to the Coroner’s Facility in Toronto

67
Q

Who uses PMCT in Ontario?

A

Forensic pathologists, radiologists (more complex cases), anthropologists, odontologists

68
Q

What can PMCT be used for in forensics?

A

Diagnosis
Age estimation (adult and fetal)

69
Q

When can PMCT be used for identification?

A

Where antemortem record is available

70
Q

When was the first time PMCT was used in the US?

A

2012

71
Q

What are the 4 agencies in the US that use PMCT?

A

NM, MD, LA county, AMFEO

72
Q

What is required when PMCT is submitted into court as evidence?

A

Requires testimony to ensure renderings are true.

73
Q
A

Forensic Anatomy - Forensic Significance (5 decks)

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