Lecture 3: Imaging Modalities: decisions Flashcards
What are radiographs good at looking at
Bones
Radiographs have limited ___detail but contrast can help with that
Soft tissue
What is the biggest con of radiographs
Superimposed structures
What are some disadvantages for plain film radiographs
Requires processor, money for chemicals, and can have artifacts from processing
How does computed radiography work
Have screen film place into reader and creates digital image
What are the advantages for digital radiology
Fast process, no film required, few artifacts
Identify which X-ray modalities were used and how do you know
Left: plain
Right: CR
Middle: DR- more crisp
Identify which X-ray modalities were used and how do you know
Left: plain
Middle: CR
Left: DR- better at seeing soft tissue
Which X-ray modality is best at seeing soft tissue: plain, CR or DR
DR
Ultrasound is great for looking at ___
Soft tissue
Ultrasound of eye- what wrong
Cataracts- front of eye appears thicker/ whiter on ultrasound
What is the difference between x-rays and gamma rays
- X-rays produced from electron shell- knock out other electrons to make energy
- Gamma rays from nucleus- decays and release energy
What is the most common gamma ray
99mTcO4
How does technetium metastable work in nuclear medicine
Decays to 99Tc which is then taken up by stomach, thyroid glands, salivary glands
Identify 1-4 and what does it tell you
- Salivary glands
- Thyroid glands
- Heart
- Stomach
1 thyroid gland is very bright because hyper functioning whereas other thyroid gland is suppressed
How can you use technetium/ nuclear medicine to evaluate portosystemic shunt
- Give technetium rectally
- Enters blood—> liver—> heart
- Normal should have bright spots in liver, if shunt will bypass over liver
How does a bone scan work
- Bind 99mTc with methylene diphosphate (MDP)
- MDP binds hydroxyapetite which is present during osteoblastic activity
What modality is this and what is wrong
Bone scintigraphy
Tumor on ribs- black spots indicate increased osteoblast activity
What type of imaging is CT
Cross-sectional imaging
How does a CT work
Uses x-ray tube with adjacent detectors that measure amount of attenuation of beam by patient and create 1 image
What is the hounsfield/ CT unit measurement of bone
300-3000
What is the hounsfield/ CT measurement for mineralized disc
100-300
What is the hounsfield/ CT measurement for acute hemorrhage
42-58
What is the hounsfield/ CT unit for gray matter in brain
35
What is hounsfield/ CT measurement for white matter in brain
30
What is the hounsfield/ CT measurement for water
0- used to center it
What is the hounsfield/ CT measurement for fat
-50 to -100
What is the hounsfield/ CT measurement for air
-1000
How would something with a high hounsfield/ CT measurement appear
Brighter
CT is primarily used to evaluate __ but can also evaluate __ if given contrast medium
Bone, soft tissue
What is multiplanar reconstruction
Data sets of CT images can be reconstructed into different images
What is helical scanning
Patient is moved continuously while tube/detectors rotate, produces corkscrew path
How does magnetic resonance imaging work
Manipulates atoms in patient to create image
MRI field strength measures in ___
Tesla
What is the drawback of MRI
Radio waves cause heat production and can increase body temp
How long does a high field strength vs a low field strength MRI take
High field- 1hr
Low field- 3hrs
An average MRI study contains how many images
300-600
What is bright vs dark in a T1 weighting
Fat is bright
Fluid is dark
What is T1 weighting good at analyzing
Anatomy
What is bright in T2 weighting in MRI
Fluid is bright
What is T2 weighting in MRI good for
Inflammation
What is the downside of T2 being used in high field strength magnet
Both fat and fluid will be bright
Which modality is great for 3D reconstructions
CT
MRI is great for looking at __
Soft tissues
