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)
