Imaging Modalities

Question 1

X-ray: what is the tissue absorption level dependent on?

Answer 1

It is dependent on:

• calcified structures
• soft tissue
• fat
• gas

Question 2

What does X-ray do to a 3D image

Answer 2

it reduces it to a 2d projection

Question 3

What is Angiography and what is it used to visualize

Answer 3

A contrasting agent is injected into blood vessels to increase their visibility against the surrounding tissue

Question 4

What is Digital Substraction angiography

Answer 4

obscuring bony structures can be removed from the image to a negative of the precontrast radiograph

Question 5

What is nuclear medicine?

Answer 5

a radioactive material is injected and its course is followed by a detector

Question 6

Nuclear medicine: which parts of the body can be targeted by radionucleotides (4)?

Answer 6

• Heart
• Lungs
• Bone
• brain

Question 7

What type of radiation is emitted by the radionucleotides?

Answer 7

gamma radiation

Question 8

How does X-ray differ from nuclear medicine

Answer 8

X-ray visualized structure while nuclear medicine visualizes physiological function

Question 9

Nuclear medicine: what it evaluates in the heart (3)

Answer 9

• visualize heart blood flow and function
• can detect coronary artery disease
• good for evaluating treatment options

Question 10

Nuclear medicine: what it evaluates in the lungs(2)

Answer 10

• scans lungs for respiratory and blood flow problems

- assess differential lung function for lung reduction or transplant surgery

Question 11

Nuclear medicine: what does it evaluate in bone (7)

Answer 11

• evaluate bones for fractures
• evaluates bones for infection
• evaluates bones for arthritis
• evaluates for metastatic bone disease
• evaluate for painful prosthetic joints
• evaluate bone tumors
• identify site for biopsy

Question 12

Nuclear medicine: what does it evaluate in brain (3)

Answer 12

• investigate abnormalities in the brain in patients with certain symptoms such as: seizures, memory loss, and suspected abnormalities in blood flow
• detect early onset of neurological disorders
• assist in surgical planning and localize seizure foci

Question 13

Ultrasound advantages (3)

Answer 13

• good for cysts/cystic structures
• fetus in the amniotic fluid
• good for 2 structures with large difference in acoustic impedance

Question 14

Ultrasound disadvantages (3)

Answer 14

• gas filled and bony structures cannot be imaged
• Ultrasound can’t capture tissue/gas interphase or tissue/bone interphase
• Never used in lung or bony pathology

Question 15

Computer Tomography basics (3)

Answer 15

• transforms 2D qualitative imaging into quantitative 3D format
• overcomes the limitations of plain radiography
• does not superimpose structures

Question 16

Computer Tomography imaging

• Image Based on?
• how the x-ray beams work

Answer 16

• image is based on a mathematical formalism that states that an object is viewed from a # of different angles that a cross sectional image may be computed from
• X-rays are focused into a thin beam that only passes through a slice of tissue
• beam strikes very sensitive detectors that can quantify subtle differences in tissue density

Question 17

Computer Tomography: slice by slice acquisition(2)

Answer 17

• X-ray tube is rotating around patient to acquire a slice

- patient is moved to acquire the next slice

Question 18

Computer Tomography:volume acquisition

Answer 18

X-ray tube is moving continuously along a spiral path and the data is acquired continuously

Question 19

Computer Tomography: multislice system (4)

Answer 19

• parallel system of detectors used
• 4/8/16 slices taken at a time
• Generates large data set of thin slices
• Better spatial resolution is achieved

Question 20

Computer Tomography drawbacks (2)

Answer 20

• high levels of radiation given

- despite high hopes reliable discrimination between normal and pathological tissues using CT number was unsuccessful

Question 21

Magnetic Resonance Imaging basic facts(2)

Answer 21

• principle modality for image guided surgery

- superb ability to discriminate between subtle differences in tissue characteristics

Question 22

Magnetic Resonance Imaging: T1 vs T2

Answer 22

T1: depends on the time protons take to return to the axis of magnetic field

T2- depends on the time the protons take to dephase

Question 23

Magnetic Resonance Imaging: what will be seen in the pathologic process `

Answer 23

-increased numbers of mobile protons

• prolongation of relaxation times- this means:
• – reduced signal intensity on T1 image (blacker)
• – increased signal intensity on T2 image (whiter)