Introduction to Biomedical Imaging

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Introduction to Biomedical Imaging

Introduction to Biomedical ImagingAlejandro Frangi, PhDComputational Imaging LabDepartment of Information & Communication TechnologyPompeu Fabra Universitywww.cilab.upf.edu


Nuclear Medicine (SPECT & PET)Introduction to Biomedical Imaging


Radioisotope ImagingNuclear Medicine (SPECT & PET)The imaged property is the distribution of radionuclide-labeled agents injected inthe body: radiopharmaceuticals• Produce functional images of tracer concentrations related to pathophysiologicalprocesses• Isotope Any two or more forms of anelement having identical or very closelyrelated chemical properties and thesame atomic number but differentatomic weights or mass numbers• Radioisotope An unstable isotope ofan element that decays or disintegratesspontaneously, emitting radiation• Radioactive decay of radioisotopesleads to the emission of α-, β-, γ-, and x-radiation depending on theradionuclide involve• The range of α-, β-particles is smallfor in vivo imaging using externaldetectorsIntroduction to Biomedical Imaging


Nuclear Medicine (SPECT & PET)Radioisotope Imaging• Radioisotope imaging is restricted to the use of radio nuclides emitting photonswith energies > 50 keVPhotoelectricabsorptionComptomscatteringIntroduction to Biomedical Imaging


Anger camera (1960s)Nuclear Medicine (SPECT & PET)• Radioisotope imaging is restricted to the use of radio nuclides emitting photonswith energies > 50 keV• Lead collimator (incidence orientation selection)• Scintillation camera of NaI (sodium iodide)• Photomultipliers (PMT)Introduction to Biomedical Imaging


Types of radionuclide imaging techniquesNuclear Medicine (SPECT & PET)• Static planar scintigraphy• Dynamic planar scintigraphy• Emission Computed Tomography (ECT)• Single Photon Computed Tomography (SPECT)• Positron Emission Tomography (PET)Images of the lower limbs taken every 15 s after tracer injectionIntroduction to Biomedical Imaging


Nuclear Medicine (SPECT & PET)Emission Computed Tomography (ECT)• Single Photon Computed Tomography (SPECT)• Same principle of Gamma camera but with 2 or 3 rotating cameras to record projectiondata more efficiently• In CT we know the position of the emitting source and the detection point; in SPECT onlythe detection point• In CT absorption is the essence of the imaging process; in SPECT attenuation degradesthe images• Attenuation must be compensated for (single scan-line of photons to estimatetransmission coefficient)Introduction to Biomedical Imaging


Emission Computed Tomography (ECT)Nuclear Medicine (SPECT & PET)• Gated Single Photon Computed Tomography (Gated SPECT)• Use the repetitive nature of the cardiac cycle and define counters per subintervals of the ECGIntroduction to Biomedical Imaging


Emission Computed Tomography (ECT)Nuclear Medicine (SPECT & PET)• Gated SPECT particularly useful in cardiac perfusion studies• Some systems with slip ring technologyGE Millenium 2-head slip ringtechnologyIntroduction to Biomedical Imaging


Emission Computed Tomography (ECT)• Positron Emission Tomography (PET)Nuclear Medicine (SPECT & PET)• Radiotracer produces positrons, which are annihilated within around 1mmfrom their origin• After annihilation 2 γ-ray photons are emitted along a Line Of Response(LOR)• Electronic coincidence detectors (12ns), which eliminates lead collimatorsand allows higher efficiency• In PET it is easier to correct for attenuationLORIntroduction to Biomedical Imaging


Positron Emission Tomography• Combined CT/PET scanNuclear Medicine (SPECT & PET)Introduction to Biomedical Imaging


Nuclear Medicine (SPECT & PET)Emission Computed Tomography (ECT)• Radioisotope production for PET requires a cyclotron• Some radioisotopes have a very short life time and have to be produced in houseIntroduction to Biomedical Imaging


Nuclear Medicine (SPECT & PET)PET & PET/CT Systems• Some modern systems are in fact a dual PET/CTPETPET/CTIntroduction to Biomedical Imaging


PET & PET/CT SystemsNuclear Medicine (SPECT & PET)Introduction to Biomedical Imaging

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