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Theory Flashcards

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USMLE® Step 1 flashcards
1
Q

Ultrasound definition

A
  • Mechanical oscillation
  • Higher freq (pitch) than 20000 Hz (upper limit human ear)
  • Longitudinal in liquid and gas
  • Both (longit.& transv.) in solids
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2
Q

Direct piezoelectric effect

A

US -> electric energy
- Detection of ultrasound
- Piezoelectric insulators accumulate electric charge and gets polarized when mechanical strain (pressure, tension) is applied on them.
This results in measurable potential difference between electrodes on opposite sides of crystals.

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3
Q

Inverse piezoelectric effect

A

Electric energy -> US

  • In the transducer
  • Electric voltage applied on electrodes of piezoelectric material -> becomes deformed
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4
Q

Transducer

A

Device that converts electric energy into mechanical and vice versa

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5
Q

Damping (US)

A

Parameter that characterises attenuation of US

  • J0: initial intensity
  • J: intensity after passing theough layer
  • Energy lost as heat
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6
Q

Acoustic impedance

A

Characterizes acoustic properties of medium
- Z = density*velocity
- Boundary surface/interface: acoustic impedance changes
(Higher difference=higher reflection)

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7
Q

Reflexivity

A

Ratio of reflected:incident intensity
R=0: no reflection
R=1: total reflection

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8
Q

Pulse echo method

A

d=(c*t)/2
Calculate distance between transducer and reflecting boundary surface
c: sound velocity (known for medium)
t: elapsed time from emission to arrival of sound

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9
Q

Doppler effect

A

Frequency (and wavelength change as a result of relative motion and source of the observer

  • Towards you: shorter wavelength - higher pitch
  • Away: longer wavelength - lower pitch
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10
Q

Use of US

A

1) Diagnostic (ultrasonography, medical sonography)
- Non-invadive
2) Therapy
- Rheumatology
- Musculoskeletal disorders (arthrosis)
- Removal of dental calculus

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11
Q

Source of US

A

Sine wave oscillator conduct electric pulse (MHz) to trancducer containing the piezoelectric crystals (converts electric->US “Inverse piezoelectric effect”)

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12
Q

Ultrasound pulse…

A

Should be short - only a couple of time periods (sine waves)

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13
Q

Eigen-frequency

A

Frequency of largest amplitude vibration of a solid material (own resonance frequency)
*For best US - electric signal should match Eigen-frequency of the piezoelectric material

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14
Q

Detection of US

A
  • US -> transducer (polarizes) -> electric signal (direct piezoelectric effect) -> conducted through cable to electronic amplifier
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15
Q

Diagnostic US imaging methods

A

1) One dimentional A-image (amplitude modulation)
2) One dimentional B-image (brightness modulation)
3) Two-dimentional B-image (2D, brightness modulated)
- Series of one dimentional B-images at diff. angles
4) M image (motion)
- Info: position of the given surface as function of time
5) Reconstructed 3D image (tomography)
6) Reconstructed 4D image
- Time is 4th dimention - US movie created
7) Doppler methods

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16
Q

Brightness

A

Pixels - proportional to amplitude of reflected US signal

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17
Q

Doppler shift

A

= f - f0

Proportional to the relative velocity (v/c) and to the incident frequency

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18
Q

Doppler methods

A

1) Doppler time-velocity image:
- Doppler-frequency-shift plotted as a function of time - corresponds to velocity of observed surface

2) Color-coded Doppler image:
- Color coded velocity information

3) Doppler flow meter
- Can measure velocity of blood flow in larger blood vessels

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19
Q

Digital image

A

Information displayed at different discrete spatial points in the form of color
- 2 or 3 dimentional array or matrix of picture elements

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20
Q

Characteristics of the digital image

A

1) Picture element (pixel)
2) Information associated with the pixel
- XY location: coordinates related to spatial resolution
- Color depth: intensities related to color/gray-scale resolution
3) Spatial resolution
- Number of resolved pixels in the X and Y directions
4) Grayscale/color depth
- Number of resolved colors/grayscale intensities (bit)

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21
Q

Color histogram

A
  • Resolved intensities may be displayed as a function

- Relative frequency of colors or grayscale intensities in the image

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22
Q

Image enhancement techniques

A

1) Contrast manipulation
- Color transfer function: assigns color to pixel densities (expressed in numerical values)
2) Convolution
- Kernel operation - se eget kort
- Blurry vs skarpt
3) Rank operations
- The pixel is exchanged for another from its ranked neighborhood (e.g noise removal - prikker)
- Min, max, median, mean(?)

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23
Q

Convolution

A

Image enhancement technique

  • Kernel operation -> smoothing, sharpening, edge detect.
  • Convolution is the process of adding each element of the image to its local neighbors, weighted by the kernel
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24
Q

Fourier transformation + principle

A

Fourier principle: any function may be generated as the sum of sine function and its harmonics

Fourier transform: decomposes a function of time (a signal) into the frequencies that make it up (FFT, inverse FFT, masked FFT)

Smoothie analogy:

  • What does the Fourier Transform do? Given a smoothie, it finds the recipe.
  • How? Run the smoothie through filters to extract each ingredient.
  • Why? Recipes are easier to analyze, compare, and modify than the smoothie itself.
  • How do we get the smoothie back? Blend the ingredients.
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25
Q

Binary transformation

A

The image is partitioned according to certain parameters

  • Tresholding, segmentation
  • Excecution:
    1: Select a certain grayscale range of the image
    2: The selected pixels form the “foreground”
    3: The rest of the pixels form the “background”
  • Bildet blir svart og hvitt i stedet for gråskala
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26
Q

Binary operations

A

1) Boolean functions (of image a and b):
- a OR b (union)
- a AND b (intersection)
- a NOR b (union+intersection?)
- NOT a (complement of a)
* Boolean operation: separation of touching objects

2) Erosion, Dilatation, Opening, Closing
- Moving pixels from the foreground to the background and vice versa
- Erosion: svarte prikkene blir mindre og mindre
- Dilatation: svarte prikkene blir større og større

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27
Q

DICOM

A

Digital imaging and communications in medicine
- En standard for håndtering, lagring, utskrift og overføring av medisinske digitale bilder og informasjon relatert til disse bildene

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28
Q

X-rays (characteristic, wavel, freq, energy)

A
  • Electromagnetic wave
  • Wavelength: 10 - 0.01 nm (10nm: soft x-r, 0,01: hard)
  • Frequency: 30 * 10^15 - 30 * 10^18 Hz (petaHz-exaHz)
  • Energy: 120 eV - 120keV
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29
Q

Generation of X-ray - rotating anode tube

A
  • X-rays are emitted when a high-speed electron hits a metal target - is decelerated (1 % of electron beam converted to protons, rest to heat)
  • Rotating anode to deal with heating problem
  • Hot-wire cathode (heated by DC circuit)
  • Anode at 45 degrees angle to direct toward window
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30
Q

2 mechanisms of X-ray generation + spectrum

A

1) Bremsstrahlung
- Breaking/deceleration radiation
- Continous energy spectrum

2) Characteristic radiation
- X-ray fluorescence
- Electron collides w/K-shell electron -> K-shell electron ejected -> higher shell electron jumps down -> emission of a single X-ray photon
- Linear energy spectrum

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31
Q

μm

A

Mass attenuation coefficient (cm^2/g)

= the sum of mass attenuation coefficients of the different absorption mechanisms

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32
Q

Attenuation mechanisms

A

1) Photoeffect (=> 1 photoelectron)
2) Compton scatter (=> compton photon+compton elec.)
3) Pair production, annihilation (=> electron + positron and the positron gives 2 photons)
* Energy colliding electron must be > 1022 keV

Se bilde ipad!!!

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33
Q

Diagnostic X-ray contrast mechanism

A

1) between soft tissue and bone: photoeffect (~Z^3)

2) within soft tissue: compton scatter (~density)

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34
Q

X-ray image is a…

A

…summation image

- Contrast arises due to spatially varying attenuation

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35
Q

Spatial resolution x-ray

A

Bidirectional x-ray imaging

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36
Q

CT

A

aka CAT scan
= tomographic digital imaging method that uses x-rays
- Objective: to determine the atten. coeff. of the individual volume elements (voxels)
- Rotation of source and detector

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37
Q

Types of CT techniques

A
  • Conventional (outdated) technique
  • Spiral CT technique
  • Multidetector spiral CT (MSCT - multi slice…)
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38
Q

CT image reconstruction

A

1) Algebraic reconstruction techniques
2) Direct Fourier reconstruction
3) Filtered back projection (current method)

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39
Q

CT image and contrast manipulation

A
  • Density: Hounsfield units
  • water = 0 HU, fat ~ -200, bone ~ 1000
  • Windowing = contrast manipulation
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40
Q

Dual source CT

A
  • Use 2 diff. X-ray sources and detectors simultaneously
  • Placed perpendicular to each other
  • Dual-energy mode: different accelerating voltages
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41
Q

CT contrast agents

A

Water-soluble, iodine-containing macromolecule causing enhanced absorbance at the sites of accumulation

  • Ionic contrast agents are outdated, must be non-ionic
  • Monomeric or dimeric, low osmolality
  • Filtration through kidney (nephrotropic)
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42
Q

Imaging blood vessels

A

CT angiography

  • With iv contrast+conventional tech: vessels>1 cm (aorta)
  • Spiral CT angiography:
    a. Single detector array spiral CT: aorta br.s (>2-3mm)
    b. Multidetector array spiral CT: periph vs (>1mm)
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43
Q

HRCT

A

High resolution CT

  • Very thin slices (1-2 mm)
  • Very high contrast resolution
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44
Q

Limitations of CAT scanning

A
  • Ionizing radiation (x-ray)
  • Irradiation dose 50-100x conventional x-ray
  • Direct exposure to radiation
    • scattered radiation
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45
Q

Hybrid technologies

A
  • NanoSPECT/CT
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46
Q

MRI fundamentals

A

Nuclear magnetic resonance imaging

1) Atomic nuclei with nuclear spin are elementary magnets
- Atomic nuclei have mass, angular momentum, charge and magnetic moment
2) Nuclear spin orient in a magnetic field
3) Oriented nuclear spins display precessional motion
- “Precession is a change in the orientation of the rotational axis of a rotating body”
- Net magnetization - se eget kort
4) The system may be excited with radio frequency radiation
- Resonance condition: Larmor frequency

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47
Q

Proton (aka nuclei) mass and charge

A

Mass: 1.6710^(-24) g
Charge: 1.610^(-19) C

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48
Q

Useful nuclei in MRI

A

H, C, F, N, P

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49
Q

Net magnetization

A

Due to spin access in different energy states

  • Ratio of magnetic spins in high-energy (antiparallel) and low energy (parallel) states
  • Boltzmann distribution
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50
Q

Electromagnetic radiation in MRI

A

Radio waves

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51
Q

T1 and T2 (MRI)

A

The approach to thermal equilibrium is known as relaxation. T1 and T2 are relaxation times.

T1: “Spin-lattice relaxation”

  • Depends on interaction between elementary magnet (proton) and environment
  • Longitudinal relaxation
  • Larmor frequency

T2: “Spin-spin relaxation”

  • Depends on interaction between elementary magnets (protons)
  • Transverse relaxation
  • FID: see free induction decay
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52
Q

Spin-echo sequence

A

Repetitive pulses of excitation and subsequent relaxation

- T2 or transverse relaxation

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53
Q

Contrast in MRI

A

Determined by interaction of spin systems

  • Free water have high mobility
  • Solid have low mobility
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54
Q

Spatial encoding in MRI

A

3D (voxels)

  • Magnetic field gradient
  • Gradient coils: y-, x- and z-coil (of machine)
  • Magnetic field is always in z-direction
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55
Q

Magnetic field direction MRI

A

Always Z-direction

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56
Q

Image reconstruction MRI

A

1) Backprojection

2) 2D Fourier transformation

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57
Q

Color contrast MRI is based on…

A
  • Spin density

- Relaxation times

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58
Q

Contrast agents MRI

A

Positive
- Paramagnetic elements (T1 contrast): Gd, Mn

Negative
- Superparamagnetic, ferromagnetic (T2 contrast): FeIII, MnII

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59
Q

Artifacts and dangers MRI

A

Artifacts: motion, metals

Dangers/contraindications:

  • Metals
  • Gradient field - induced current
  • Radio frequency field (thermal effects - lens, testis)
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60
Q

MRI angiography

A
  • Saturated spins moves out of the image due to flow of blood
  • Non-invasive
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61
Q

MR spectroscopy uses

A
  • Chemical shift
  • Identification of metabolites
  • Tumor diagnostics
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62
Q

Tractography

A

Imaging of neural tracts

MRI - Diffusion imaging

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63
Q

Functional MRI

A

High time resolution images recorded synchronously with physiological processes

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64
Q

MRI and PET

A

Can be superimposed

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65
Q

Molecular imaging definition

A

Molecular imaging is the visualization, characterisation and measurement of biological processes at the molecular and cellular levels in humans and other living systems

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66
Q

Molecular imaging ideals

A

Visualization

  • Signal to noise ratio
  • Accuracy of information (where?)
  • Spatial resolution (yes or no?)

Characterization

  • Time resolution (when? How?)
  • Magnitude and density of information (how?)

Measurement

  • Robustness, repeatability
  • Quantitation, accuracy (how much?)
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67
Q

Molecular sensitivity

A

This quality of any given imaging modality is to be used upon decision of its application. Considers:
- Cell conc
- No. of targeted molecules
- How much contrast reach target vs injected
- Activity
++

68
Q

Examples molecular imaging

A
  • SPECT
  • Immunochemistr, immunofluorescence (microscopy)
  • Dual photon microscopy
69
Q

General structure of molecular probe

A
  • Therapeutic part (?)
  • Targeting part - binds to specific molecules (small molecules, peptides, proteins/subunits, Ab’s/subunits)
  • Signalling/contrasting element
70
Q

Molecular probe examples

A

Chemical

  • PET/SPECT: isotopes (radioactivity)
  • Optical/acoustic: fluorescent dyes
  • MRI: Gd, Fe
  • CT: iodine, barium sulphate

Nano/microparticles

  • Optical: quantum dot, carbon nanotubes, Au particles
  • MRI: iron and Mn-oxide particles
  • CT: golden particles
71
Q

Advantages CT

A
  • Any imaging depth (also disadvantage)
  • Good resolution (also disadvantage)
  • Simple
  • Medium-priced
  • Sub-minute scan times
72
Q

Disadvantages CT

A
  • Radiation
  • Just anatomical and functional images
  • Semi-expensive
  • Soft tissue contrast
  • WB imaging
  • Minute-scanning time
73
Q

Contrast materials CT

A

Ba, I, Kr, Xe, Au

74
Q

Clinical use CT

A
  • Tumor perfusion
  • Ca-score
  • Ventillation
75
Q

US advantages

A
  • No ionizing radiation
  • Fast/RT imaging
  • High sensitivity
  • High resolution
  • Cheap
76
Q

US disadvantages

A
  • No WB imaging
  • Only vascular contrast materials
  • Operator dependency
77
Q

Contrast material US

A

Microbubbles

78
Q

Clinical use US

A
  • Focal liver lesions
  • ECG
  • Blood perfusion
  • Prostate cancer VEGF expression (phase III BR55)
79
Q

MRI advantages

A
  • Any imaging depth and plane
  • WB imaging
  • No ionizing radiation
  • High soft tissue contrast
80
Q

MRI disadvantages

A
  • Expensive
  • Low sensitivity
  • Long imaging time
81
Q

MRI contrast materials

A

Gd3+,iron-oxide particles (SPIO, USPIO)

82
Q

MRI clinical use

A
  • Liver
  • Brain lesions
  • Cardio-MRI
83
Q

MRS advantages

A
  • No ionizing radiation

- WB imaging

84
Q

MRS disadvantages

A
  • Expensive
  • Very low sensitivity
  • External calibration/special knowledge
85
Q

MRS contrast materials

A
  • Cholin
  • Lactate
  • Creatine
  • Lipids
  • N-Ac-Aspartate
86
Q

MRS clinical use

A
  • Brain tumor stratification

- Stroke

87
Q

Optical methods advantages

A
  • No ionizing radiation
  • Short/RT imaging
  • High spatial resolution
  • Very sensitive
  • Semi-quantitative
  • Multiplex
88
Q

Optical methods disadvantages

A
  • Limited transparency

- No WB imaging

89
Q

Optical methods contrast materials

A
  • Fluorescent molecules
  • Light-emitting reactions
  • Dyes
  • QD-s
  • NP-s
90
Q

Optical methods clinical use

A
  • Experimental
  • Sentinel LN
  • Image-guided surgery
  • Retinopathies (OCT)
  • Mammary screening (LumaGem)
91
Q

SPECT advantages

A
  • Any imaging depth
  • WB imaging
  • Quantitative
  • Good resolution
  • Multiplexing
  • Theragnostics
  • Combination w/CT
92
Q

SPECT disadvantages

A
  • Radiation
  • Sub-mm resolution
  • Long imaging times
93
Q

SPECT contrast materials

A
  • Tc-99m
  • Tl-201
  • I-123
  • In-111
  • Ga-67
  • Lu-177
  • Ho-166
94
Q

SPECT clinical use

A
  • Nuclear cardiology
  • Brain perfusion
  • Oncology (Ab, peptides)
  • Receptor T
95
Q

PET advantages

A
  • Any imaging depth
  • WB imaging
  • Quantitative
  • Anatomical co-registration CT, MRI
96
Q

PET disadvantages

A
  • Radiation
  • PRICE
  • Resolution
  • Longer imaging times
97
Q

PET contrast materials

A
  • C-11
  • F-18
  • Ga-68
  • Cu-64
  • Zr-89
98
Q

PET clinical use

A
  • FDG patient staging + follow-up
99
Q

Confocal laser endomicroscopy

A

Mucosa examined at cell level using fiber optic confocal microscope at autofluorescence emission/excitation

  • Esophagus
  • Stomach
  • Bile ducts
  • Ileal/colonic mucosa
100
Q

Bioluminescence

A

Energy-dependent multi-event reporter imaging

- Firefly, jellyfish

101
Q

Tumor targeting

A

Fluorescence (?)

  • Can be passive (in tissue around tumor)
  • or active (targeting tumor cells)
102
Q

Personalized targeted therapy

A
  • SPECT
  • MRI
  • RNT
103
Q

OCT

A

Optical coherence tomography

  • Retina
  • Mucosae
  • Cartilage
  • Blood flow
  • Mm penetration
  • Micron resolution
  • Real time imaging
104
Q

Isotope

A

Same number of protons
- (Bio)chemically same element

2 types:

  • Plus protons
  • Plus neutrons
105
Q

Production isotopes

A
  • Plus protons: in cyclotron

- Plus neutrons: in reactor

106
Q

Types of radiation isotopes

A

Plus protons

  • Positron emission (pos. beta) => annihilation
  • EC (K, L, M…) - avalanche (X-ray, gamma)
  • Alpha particle + gamma

Plus neutrons

  • Beta
  • Gamma
107
Q

Most important isotopes in nuclear medicine

A

Diagnostic (electromagnetic radiation)

  • Plus neutron: Tc-99m (gamma, metastable)
  • Plus proton: Ga-67 (x-r, gamma), C-11 (annihil.)

Therapeutic (particle - absorption)

  • Plus neutron: Y-90 (beta)
  • Plus proton: At-211 (alpha)
  • Se mer bilde ipad
108
Q

Advantages of Tc-99m

A

m = metastable (energy slowly)
Used in 80 % of SPECT examinations

  • Physical: 140 keV (ideal for gamma camera) and monoenergetic (easy for imaging)
  • Biologic: low radiation dose, half-life 6 hrs
  • Practical: from Mo-99 generator, elution by phys saline
109
Q

Theranostic concept

A

Function-specific molecules

  • Diagnostic testing employed for selecting targeted therapy
  • Theranostic concept: The same molecule
110
Q

Detection: imaging in nuclear medicine

A

1) Gamma camera (SPECT, scintigraphy)
2) Positron camera (PET)
* * Shows function of body!

111
Q

Detection: non-imaging in nuclear medicine

A

1) Ex-vivo measurements
- Biological samples: blood, urine (Schilling test)
2) Small dedicated instruments
- Thyroid uptake test
- Intraoperative gamma-probes for localization (ex: LNs)

112
Q

SPECT

A

Single-photon* emission computed tomography

  • Is a nuclear medicine tomographic imaging technique using gamma rays. Provides 3D info (2D: scintigraphy = gamma camera)
  • Double-photon emission = PET
113
Q

PET vs SPECT

A

PET: double-photon

  • More sensitive
  • Better spatial resolution
  • Quantitation is easier
  • Biomolecules! (“Slice of life”)
114
Q

Hybrid systems imaging

A

Function+morphology

1) PET/CT (PET always in hybrid today)
2) SPECT/CT
3) PET/MRI

115
Q

PET/MRI advantages

A
  • Soft-tissue contrast ins excellent

- No ionizing radiation

116
Q

Nuclear molecular imaging advantages and disadvantages

A

Advantages:

  • Functions!!
  • Non-invasive (not toxic, few allergies)

Disadvantages:

  • Geometric resolution limited
  • Anatomy, morphology, details, localization (but hybrid)
  • Radiation (Gamma: 1-7 mSv, annihil.: 5-10 mSv, EC: 15 mSv)
117
Q

Molecular nuclear imaging selection of targets

A
  • Enzymes-subst
  • Receptor-ligands
  • Ag’s-Ab’s
  • Transport proteins-subst
  • Deposits-binding molecules
118
Q

FDG

A

Fluor-deoxy-glucose

  • Most important radiopharmaceutical (PET)
  • Mainly in oncology - tumors need sugar for energy
  • Not tumor-specific
119
Q

Radionuclide therapy general characteristics

A

SELLER:

  • Specific
  • Effective
  • Low dose rate (but high dose)
  • Low side-effects
  • Excellent palliation (reduce sympt./partially treat)
  • Repeatable
120
Q

Wave types in diff media

A

Gas+liquid: only longitudinal

Solid: transverse

121
Q

Timbre

A

Tone color

- Relative strengths of overtones/harmonics (spectrum)

122
Q

Acoustic impedance formula

A

Z=cρ (speed velocitydensity)

123
Q

Human ear audible range

A

20 Hz - 20 000 Hz

  • Below: infrasound
  • Above: ultrasound
124
Q

Phenomena at boundery of different media US

A

Perpendiclar incidence: reflection + transmission

Skew incidence: Snellius-Descartes (refraction)

125
Q

Wavelength piezoelectric crystal vs couplant layer

A

Piezoelectric crystal: λ/2

Couplant layer: λ/4

126
Q

Time sharing mode US

A

Pulses instead of continous wave US (gives band spectrum)

127
Q

Zones US beam

A

Near field: Fresnel zone (straight)

Far field: Fraunhofer zone (fan-shaped)

128
Q

Resolving limit and resolution

A

Resolving limit: Distance between to object detais which can just be resolved as disting objects

  • Smaller is better
  • Axial RL: depend on pulse length
  • Lateral RL: depends on beam width

Resolution: Reciprocal of resolving limit
- Larger is better

129
Q

Focusing US beam

A

Increases the divergence of the beam in the far field and reduces depth sharpness

130
Q

Huygens’ principle

A

Any wave propagates so that each point of a wave serves as a source of a secondary wave with speed and freq equal to the primary wave

131
Q

Electronic focusing

A

Delay units alter the time of emission

132
Q

Color coding US

A

BART

“Blue away red toward”

133
Q

Beating phenomenon

A

Beating frequency equals the difference of the two interfering frequencies
- Addition and deletion

134
Q

Time domain correlation method (CVI)

A

CVI = color velocity imaging

- If the reflecting surface and/or the scatterer are moving then the US signal at a fixed position depends on time.

135
Q

Sono-CT

A

Image reconstruction from several multidirectional B-images

136
Q

Sonoelastography

A

Sonoelastography is an ultrasound imaging technique where low amplitude, low-frequency shear waves are propagated through internal organs, while real-time Doppler techniques are used to image the resulting vibration pattern. When a discrete hard inhomogeneity, such as a tumour, is present within a region of soft tissue, a decrease in the vibration amplitude will occur at its location

  • Check softness/elasticity of tissues
  • Intravascular sonoelastography also exist
137
Q

CHI

THI

A

Contrast harmonic imaging: behaviour of microbubbles
Tissue harmonic imaging
*Se bilde ipad

138
Q

IVUS

A

Intravascular US

139
Q

Image pixel size and distance in analogue vs digital image

A

Analogue: random
Digital: uniform

140
Q

PPI and DPI

A

PPI: pixel per inch - display
DPI: dots per inch - printer

141
Q

Zoom, bitmap, vector

A

Increase pixel size

  • Bitmap: no more information - gets unsharp eventually
  • Vector graphics: unlimited zoom - must be described as curves
142
Q

DSA

A

Digital subtraction angiography

143
Q

Most common source of noise

A

Detector (semiconductor detectors are heat-sensitive - cooling may decrease noise)

144
Q

Fourier transformation and reconstruction

A

FT: spatial domain => frequency domain
FR: frequency domain => spatial domain

145
Q

Application of Fourier transformation

A
  • Noise filtering

- To find edges

146
Q

Aliasing

A

Sampling problem

- Sampling must be the double of the signal frequency at least

147
Q

Filetypes

A

1) Uncompressed: BMP (bitmap)
2) Compressed:
- Lossless: TIFF, GIF
- Lossy: JPG (small storage, loss of info)
3) DICOM: uniform file type + network communication protocol in medicine)

148
Q

DEXA

A

Dual energy x-ray absoptiometry

149
Q

Photoacoustic tomography

A

To diagnose tissue alteration without the application of any harmful radiation
- Photoacoustic tomography combines the advantages of US with the non-ionizing selective laser excitation

150
Q

Radiopharmacons composition

A

Two parts

  • Radioactive isotope as radioactive source
  • Pharmacon responsible for selective delivery
151
Q

Most common isotopes PET and SPECT

A

PET: F-18, C-11, Ga-68
SPECT: Tc99m, I-123, I-125, I-131, Tl-201 and Ga-67

152
Q

Benefits of Tc-99m

A

1) Emit only gamma-radiation
2) Optimal gamma-energy
3) Optimal half-life time
4) Easy to create and bind to different pharmacons
5) Cheap

153
Q

The 2 criteria radiological images must fulfill

A

1) Appropriate spatial resolution

2) Contrast

154
Q

The 2 criteria radiological images must fulfill

A

1) Appropriate spatial resolution

2) Contrast difference

155
Q

Radiopharmacons CNS

A

Catagorized by ability to cross BBB:

1) Hydrophilic and anionic molecules cannot cross BBB unless altered permeability
- DTPA (normally cannot cross - used to detect endothel dysfunction in the brain)
2) Lipophilic - can cross BBB
- Tc-HMPAO - measure organ perfusion (ex: brain)
- F-18-FDG - show speed of brain glucose metabolism

156
Q

Is it possible to detect the distribution of two or more isotopes at the same time?

A

SPECT: Yes, because we can distinguish between two differen radiopharmacons with different isotope, because they have different gamma energy

PET: No! Same gamma energy after annihilation

157
Q

CB1-R

A

Target receptor in diagnosis of epilepsy and alzheimer disease

158
Q

Designing PET ligands

A

Easiest: Change one H of ligand analogue with F18 or a C with C-11

159
Q

CNS imaging

A

Multimodal imaging: can see CNS distribution of a SPECT (not PET!) in front of MRI and CT

Brain blood flow: multi-isotope signaling (Tc-HMPAO)

BBB injury: dual labeling techiques

160
Q

Thyroid imaging

A

Iodine isotopes (I-125, I-131)
99mTc
*Substrates of Na/I symporter

161
Q

Nuclear cardiology examinations + isotope

A

1) Myocardial perfusion (Tc-MIBI - or: Tl-201)
2) Help diagnose AMI
3) Measure myocardial metabolism (FDG or C11 marked glucose)

162
Q

Bone scintigraphy diagnoses

A

1) Oncologic diseases
2) Bone metabolism
3) Fracture
* Show if increased osteoblast and osteoclast activity + pathological hyperaemia
* Phosphate compounds marked with Tc bind to free hydroxyappatite crystals of bones
* *Most frequently used: MDP (methyl-diphosphate)

163
Q

Why is bone scintigraphy preferred over x-ray in pediatrics?

A
  • Higher sensitivity

- Lower dose

164
Q

Liver nuclear molecular imaging

A
  • Liver function
  • Bile-excretion, -flow and -ducts
  • Use derivatives of IDA marked by Tc
  • Kupffer cells: HSA nanobodies
165
Q

PEG

A

Polyethylene glycol

  • On a nanobody
  • Disguise against the immune system
166
Q

Dose requirement

A

ALARA: as low as reasonably achievable

167
Q

High sensitivity

A

Nuclear imaging

Medical Imaging (1 decks)

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