Imaging and Radiology (Lec 2)

Question 1

Xrays:
Wavelength length

Answer 1

Wave lengths are shorter than visible light (10picometers to 10 nanometers)

Question 2

Why is there darker regions (eg lungs) and lighter regions on Xray

Answer 2

Xrays are stopped by dense tissues such as bones, preventing them reaching and reacting with the Xray sensitive surface

Non dense regions such as lung stop few Xrays and appear darker on the surface

Question 3

Hazards of radiation exposure

Answer 3

Carcinogens, tetratogenesis, abortion, burn

Question 4

Examples of structures/tissues etc that give these colours on xray

White
Grey
Darker grey
Black

Answer 4

White: Calcium, mineral, metal (eg bone)

Grey: Water/tissues (heart, liver)

Darker grey: Fat (eg subcutaneous)

Black: Air (eg lung)

Question 5

What is haemarthrosis

Answer 5

Blood and fat in a joint

Question 6

One drawback of Xray

Answer 6

Soft tissues arent seen well on Xray

Question 7

Where can contrast material for Xrays be injected?

Answer 7

• Radio-opaque compounds are used to increase visualisation of structures
• For x-ray studies:
• introduce into cavities (e.g gut)
• Inject into blood vessels to to outline blood distribution
• Gut studies
• Barium Sulphate
• (Also Iodinated compounds)

All excreted by kidneys

Question 8

What is Angiography

Answer 8

Contrast medium used to show vessels using Xray

Question 9

How many dimensions is xray

Answer 9

single and often to get multiple angles

Question 10

Benefits and risks of plain xray

Answer 10

Benefits:
Can be very imformative
Cheap
Avaiable
Fast to aquire

Risks
Structures are superimpsoed
Poor soft tissue definitaion
Radiation dose
Typically need 2 views

Question 11

CT scans produces what kind of wavelength

Answer 11

Narrow continious fan shaped stream of X rays as it rotates around the head

Question 12

CT scan
- what plane is used
Enables?
comapred to X ray its better how?

Answer 12

use X rays in transverse plane
Enables cross sectional imaging
Better contrast resolution than X rays

Question 13

When to use contrast, thin or thick slices and window images (CT)

Answer 13

Looking at vascular structures or for enhancement: tumor etc use contrast

Looking at chest and lungs for masses use thick slice

Looking at lung parenchyma use thin slice

Window images for MAX contrast

Question 14

Benefits and risks of CT Scan

Answer 14

Benefit:
Cross sectional imaging
Moderately avaiable
Fast to acquire
Can reformat

Risks:
Poor soft tissue def
Radiation in high dose
Moderately expensive

Question 15

Perks of MRI for soft tissue

Answer 15

Gives great detail of soft tissue
- cortical dark bone = low signal

Can alter the manipulating pulse to change soft tissue contrast

Question 16

DTI (diffusion tensor imaging)
what is it

Answer 16

DTI tractography of white matter tracts, uses diffusion anisotrophy to trace axon bundles

In sheer trauma acons are torn and tracts are disrupted

Question 17

Benefits and risks of MRI

Answer 17

No ionising radiation
Excellent tissue contrast and spatial resolution
Ability to image any plane
Provide 3D images

Low avaibaility
Longer imaging time
high cost
Contraindications (pacemakers etc)

Question 18

Nuclear medicine
What is it

Answer 18

Radioactive substances are injected or ingested into patient and gamma rays are detected with gamma camera

Question 19

Examples of use of Nuclear medicine

Answer 19

Bone scans -fractures
V/Q scan for pulmonary embolism
Thyroid scan
White cell scans for infection
liver scans
renal scan
Brain scan - seizures

Question 20

Technetium 99 bone scan

Answer 20

Part of NM where it absorbs onto crystalline hydroxyapatite of bone and degree of uptake depends on blood flow and rate of new bone formation
- shows metases, inflam, infection

Question 21

PET scan (positron emission tomography)

Answer 21

Radioactive tracers (radioisotopes) accumulate in areas of higher metabolic activity

Question 22

Ultrasound perks and risks

Answer 22

No ionising radiation
portable
ability to image in any plane
Easy to use
inepensive
widely avalibale

Longer imaging time
low resolution
operator dependent
Obstructed by air and bone

Question 23

Use for ultrasound

Answer 23

Ab pain
Ab liver function tests
Swelling
palpable mass
renal dysfunction
screening for cancer
vascualr imaging

Question 24

Causes of inappropriate x-ray exposure

Answer 24

• Studies that are unlikely to change patient management
• Repeated investigations
• Wrong investigations for condition
• Failure to provide appropriate clinical information

Question 25

fresh blood is what colour on CT

Answer 25

White

Question 26

how do you know if the scan is MRI or CT

Answer 26

CT = always have white bone
MRI = bone is black