Imaging Modalities Flashcards
X-ray: what is the tissue absorption level dependent on?
It is dependent on:
- calcified structures
- soft tissue
- fat
- gas
What does X-ray do to a 3D image
it reduces it to a 2d projection
What is Angiography and what is it used to visualize
A contrasting agent is injected into blood vessels to increase their visibility against the surrounding tissue
What is Digital Substraction angiography
obscuring bony structures can be removed from the image to a negative of the precontrast radiograph
What is nuclear medicine?
a radioactive material is injected and its course is followed by a detector
Nuclear medicine: which parts of the body can be targeted by radionucleotides (4)?
- Heart
- Lungs
- Bone
- brain
What type of radiation is emitted by the radionucleotides?
gamma radiation
How does X-ray differ from nuclear medicine
X-ray visualized structure while nuclear medicine visualizes physiological function
Nuclear medicine: what it evaluates in the heart (3)
- visualize heart blood flow and function
- can detect coronary artery disease
- good for evaluating treatment options
Nuclear medicine: what it evaluates in the lungs(2)
- scans lungs for respiratory and blood flow problems
- assess differential lung function for lung reduction or transplant surgery
Nuclear medicine: what does it evaluate in bone (7)
- 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
Nuclear medicine: what does it evaluate in brain (3)
- 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
Ultrasound advantages (3)
- good for cysts/cystic structures
- fetus in the amniotic fluid
- good for 2 structures with large difference in acoustic impedance
Ultrasound disadvantages (3)
- 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
Computer Tomography basics (3)
- transforms 2D qualitative imaging into quantitative 3D format
- overcomes the limitations of plain radiography
- does not superimpose structures
Computer Tomography imaging
- Image Based on?
- how the x-ray beams work
- 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
Computer Tomography: slice by slice acquisition(2)
- X-ray tube is rotating around patient to acquire a slice
- patient is moved to acquire the next slice
Computer Tomography:volume acquisition
X-ray tube is moving continuously along a spiral path and the data is acquired continuously
Computer Tomography: multislice system (4)
- 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
Computer Tomography drawbacks (2)
- high levels of radiation given
- despite high hopes reliable discrimination between normal and pathological tissues using CT number was unsuccessful
Magnetic Resonance Imaging basic facts(2)
- principle modality for image guided surgery
- superb ability to discriminate between subtle differences in tissue characteristics
Magnetic Resonance Imaging: T1 vs T2
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
Magnetic Resonance Imaging: what will be seen in the pathologic process `
-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)
