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Advanced Biomedical Imaging

Advanced Biomedical Imaging. Dr. Azza Helal A. Prof. of Medical Physics Faculty of Medicine Alexandria University. Intended learning outcomes of the course (ILOS). To understand physical principles of imaging modalities. Aiming to apply these modalities in a safe and effective way.

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Advanced Biomedical Imaging

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  1. Advanced Biomedical Imaging Dr. Azza Helal A. Prof. of Medical PhysicsFaculty of MedicineAlexandria University

  2. Intended learning outcomes of the course (ILOS) • To understand physical principles of imaging modalities. • Aiming to apply these modalities in a safe and effective way.

  3. Imaging Modalities

  4. Plain x ray

  5. Structure of the atom a)Attraction 1.(+ve nuc. & –ve e). Prevent ele. from leaving atom 2. Neutron b) repulsion between p -ve Electron mass 1800 time < p or n +ve K shell, L,M,N,O 2n2 Energy levels ZXA potential energy nucleons Binding energy Dr Azza Helal

  6. Types of electromagnetic waves 10-12cm X Rays are high-energy EM radiation and part of EM spectrum

  7. Production of X- Rays, X ray tube High-speed electrons suddenly slowed down releasing part of their energy as X-Rays. Dr Azza Helal

  8. X-Ray tube consists of: Evacuated tube Cathode (tungsten) Focusing cup Copper anode block Tungsten target (high Z material) high melting point high thermal conductivity More efficient X-Ray production

  9. Interactions in a target Bremsstrahlung Characteristic radiation

  10. Therapeutic x-ray tube: Mega electron volts (MeV) are used, a higher conversion of electrons into photons, high KV, larger focal spot, longer duration & stationary anode. Diagnostic x ray tube: (KeV), there is more conversion of the electrons to heat, low KV, small focal spot, short duration & rotating anode. Total number of electrons converted to heat is 99%. Only 1% of the electrons are converted to photons

  11. Computed Axial Tomography (CT) Probing patient from different directions during 360 rotations with x-ray beam of known intensity (I0) & measuring it after it has passed the pt (I). Attenuation depends thickness and density of tissues • Image displays on computer or multiple films New technologies are • Helical CT & • Multiple slice / detector arrays

  12. Ultrasound (US) • Ultrasound machine transmits high-frequency sound into body using a probe. • Sound waves travel into body & hit a boundary between tissues (fluid & soft tissue). • Some waves reflected back to the probe and are detected by probe while some travel on further until they reach another boundary and then reflect back to the probe. • So image depends on transmission characteristics of the interfaces. • Image display on computer or films.

  13. 12cm Time between pulse emission and echo return determines depth Velocity =Distance/ Time Echo Reflection 160Us 20cm 260Us Reflection Echo DR Azza Helal

  14. Magnetic Resonance Imaging(MRI) • Image formed by transmitting and receiving radio waves inside a high magnetic field. • All routine MRI techniques are based on receiving and processing of the signals from protons of hydrogen atom. • The image is mainly related to Patient hydrogen density • MRI makes great pictures because of large no of protons in the body, primarily in water and fat. • Image display on computer or multiple films

  15. Assignments One student will be selected for assignment

  16. Suggested Readings David Sutton’s Radiology Physics for medical imaging by RF Fare & PJ Allisy-Roberts.

  17. Question Mention different components of x ray tube?

  18. Thank you

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