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Introduction to Medical Imaging PowerPoint Presentation

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Description : Check out this medical presentation on Radiology and Imaging, which is titled "Introduction to Medical Imaging", to know about Medical Imaging.

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Published on : Aug 02, 2021 | Views : 3005 | Downloads : 3

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Slide 1-

Introduction to Medical Imaging BME/EECS 516 Douglas C. Noll (edited by JF)
Slide 2-

Medical Imaging Non-invasive visualization of internal organs, tissue, etc. Is endoscopy an imaging modality? Image – a 2D signal f(x,y) or 3D f(x,y,z) Is a 1D non-imaging sensing techniques an imaging modality?
Slide 3-

Major Modalities Projection X-ray (Radiography) X-ray Computed Tomography (CT) Nuclear Medicine (SPECT, PET) Ultrasound Magnetic Resonance Imaging
Slide 4-

Projection X-ray Imaging Image records transmission of x-rays through object The integral is a line-integral or a “projection” through obj m(x,y,z) – x-ray attenuation coefficient, a tissue property, a function of electron density, atomic #, … X-ray Source Object X-ray Detector m(x,y,z) Id(x,y)
Slide 5-

Projection X-ray Imaging X-ray imaging requires interactions of x-ray photons with object – work in a specific energy band Above this band – body is too transparent Below this band – body is too opaque Well below this band – wavelengths are too long One problem with x-ray imaging: no depth (z) info Transmissivity of body Visible EM Spectrum Energy Near IR MRI Diagnostic X-ray Band
Slide 6-

X-ray Imaging Projection vs Tomographic Projection Image Cross-sectional Image Chest Mass
Slide 7-

X-ray Computed Tomography Uses x-rays, but exposure is limited to a slice (or “a couple of” slices) by a collimator Source and detector rotate around object – projections from many angles The desired image, I(x,y) = m(x,y,z0), is computed from the projections X-ray Source Object X-ray Detector m(x,y,z0) Collimator
Slide 8-

X-ray Computed Tomography
Slide 9-

Anatomical vs Functional Imaging
Slide 10-

Nuclear Medicine (Scintigraphy) Detector records emission of gamma photons from radioisotopes introduced into the body The integral is a line-integral or a “projection” through obj Source s(x,y,z) usually represents a selective uptake of a radio-labeled pharmaceutical Gamma Source Object Gamma Detector Id(x,y) Pinhole Camera
Slide 11-

Nuclear Medicine (Scintigraphy) Issue: Pinhole Size Large pinhole – more photons, better SNR Large pinhole – more blur, reduced resolution Issue: Half-life Long half lives are easier to handle, but continue to irradiate patient after imaging is done Issue: Functional Specificity Pharmaceuticals must be specific to function of interest E.g. Thallium, Technicium Issue: No depth info Nuclear Medicine Computed Tomography (SPECT, PET)
Slide 12-

Nuclear Medicine (Scintigraphy) Bone Scan
Slide 13-

SPECT Scanner (3 heads)
Slide 14-

Nuclear Medicine (SPECT) Cardiac (Left Ventricle) Perfusion Scan Short Axis Long Axis Long Axis
Slide 15-

PET Scanner http://upload.wikimedia.org/wikibooks/en/f/fb/PetDiag2.jpg
Slide 16-

PET-CT Scanner
Slide 17-

PET-CT Scan Anatomy Function Both
Slide 18-

Ultrasound Imaging Image reflectivity of acoustic wave, R(x,y,z). Depth – A function of time (ping-echo) Lateral – Focusing of wavefronts Direct imaging (e.g. vs. computed) modality – echo data is placed directly into image matrix Transducer Object Image R(x,y) Depth R(x,y,z) Transducer position
Slide 19-

Ultrasound Imaging Issue: Transmit Frequency Increase in frequency reduces wavelength: Reduced (improved) resolution size (2-3 l) Also improved lateral resolution (diffraction): Increases attenuation (and thus, range of depth) Issue: Flow Can use Doppler effect to image flow Issue: Speckle Most noise in US is speckle (signal dependent)
Slide 20-

Ultrasound Imaging High-Resolution Color Doppler
Slide 21-

Magnetic Resonance Imaging Atomic nuclei and hydrogen nuclei, 1H, in particular, have a magnetic moment Moments tend to become aligned to applied field Creates magnetization, m(x,y,z) (a tissue property) MRI makes images of m(x,y,z)
Slide 22-

Magnetic Resonance Imaging The magnetization is excited into an observable state Magnetization emits energy at a resonant frequency: RF Excitation (Energy into tissue) Magnetic fields are emitted (63 MHz at 1.5 T) 
Slide 23-

Magnetic Resonance Imaging Frequency is proportional to magnetic field We can create a frequency vs. space variation: Use Fourier analysis to determine spatial location Interestingly, l is much larger than resolution – not imaging EM direction, but using its frequency (x,y,z)(x,y,z)
Slide 24-

cardiac cancer stroke neuro function joint lung MRI