magnetic resonnce imaging (MRI) slides.pptx

MRI

1. Magnetic Resonance Imaging (MRI) Presented By: M.Jalal Uddin M.Mohsin M.Shahood Abdullah Khan Ishban khan

2. What is MRI? Definition : A non-invasive imaging technique that uses strong magnetic fields and radio waves to create detailed images of the body’s internal structures. Full Form : Magnetic Resonance Imaging. Purpose : Diagnoses and monitors conditions affecting organs, tissues, and bones. Non-Invasive : Does not involve surgery or radiation (unlike X-rays or CT scans).

3. History of mri First full-body human MRI scan by Damadian’s team in 1977 . Initial scans took 5 hours to produce a single image 1980s: MRI machines became widely available.

4. Unique MRI Features No Radiation: MRI uses magnetic fields and radio waves, making it safer than X-rays and CT scans. Superior Soft Tissue Imaging: MRI provides highly detailed images of soft tissues like the brain, muscles, and organs. Functional Imaging (fMRI): Measures brain activity by detecting blood flow changes, useful for studying brain functions. 3D Imaging: MRI can produce three-dimensional images, giving a detailed view of complex structures.

5. Cont … Non-Invasive: Provides detailed images without the need for surgery or tissue samples. High Resolution: Offers high resolution, enabling the detection of small abnormalities. Customizable Views: MRI images can be viewed in multiple planes (sagittal, coronal, axial) to get different perspectives of the body.

6. Basic Principles Magnetic Field: Aligns hydrogen atoms in the body. Radio Waves: Disrupts this alignment. Signal Emission : Atoms release energy as they return to alignment. Detection: The MRI machine detects these signals. Gradients: Help create detailed 2D or 3D images. Computer: Processes the signals to form images of body structures.

7. Applications Widely used in neurology & cardiology . Excellent for detailed tissue imaging Brain Imaging Musculoskeletal Imaging Abdomen and Pelvis Imaging Cancer Detection Functional MRI (fMRI) Vascular Imaging

8. Main Components - Strong magnet - Gradient coils - RF transmitter - Computer system

9. Main Magnet Produces a uniform magnetic field . Creates a powerful magnetic field that aligns hydrogen atoms in the body. The strength of the magnet (measured in teslas ) determines the quality of the images. Range: 0.5 to 2.0 Tesla .

10. Gradient Magnets Creates variable fields for spatial localization Produce varying magnetic fields within the main magnet to allow for spatial encoding. Enable the MRI machine to capture images from different angles and slice through tissues. Works alongside the main magnet .

11. RF Transmitter and Receiver Sends pulses to excite hydrogen atoms . Sends radiofrequency pulses into the body, temporarily disrupting the alignment of hydrogen atoms. When the pulse is turned off, the atoms return to alignment, emitting signals that are detected to create images. Detects returning signals

12. Computer System Processes signals into images Processes the signals received from the RF transmitter and gradient coils. Converts the data into detailed images by reconstructing the spatial information from the signals.

13. How MRI Works Magnetic Field MRI (Magnetic Resonance Imaging) uses a strong magnetic field to align hydrogen atoms in your body. Radio Waves A pulse of radio waves is sent into the body, disrupting the alignment of the hydrogen atoms. Energy Release When the radio wave pulse stops, the atoms return to their aligned state, releasing energy.

14. Cont … Signal Detection Sensors in the MRI machine detect the released energy signals. Image Creation A computer processes these signals to create detailed images of the body’s internal structures. No Radiation Unlike X-rays or CT scans, MRI doesn’t use ionizing radiation, making it safer for repeated use.

15. Spin and Alignment Hydrogen Atom Spin Hydrogen atoms in the body have protons that "spin," creating tiny magnetic fields. Magnetic Alignment In the MRI’s strong magnetic field, these spins align either Parallel (low energy) to the field. Anti-parallel (high energy) against the field.

16. Cont … Net Magnetization Slightly more protons align parallel, creating a small overall magnetic effect in the body. Precession The protons don’t stay still but "wobble" around the magnetic field like a spinning top, a movement called precession.

17. Cont … Radio Waves Interaction The MRI uses radio waves to disturb this alignment temporarily, key to generating signals for imaging.

18. Resonance Resonance : Protons absorb energy when radio waves match their natural frequency. Energy Release: Protons release energy as they return to alignment. Signal: Released energy is detected to create images.

19. Relaxation Process T1 Relaxation (Longitudinal) Protons realign with the magnetic field, releasing energy to their surroundings. T2 Relaxation (Transverse) Protons lose phase coherence with each other, reducing the detected signal. Why It Matters The relaxation rates (T1 and T2) vary in tissues, helping create detailed contrast in MRI images.

20. T1 and T2 Relaxation - T1: Spin-lattice relaxation (better resolution) - T2: Spin-spin relaxation (better contrast)

21. Hydrogen Atoms Hydrogen Abundance: The body is mostly water and fat, both rich in hydrogen atoms. Protons' Role: Hydrogen protons produce strong, detectable signals in the magnetic field. Magnetic Sensitivity: Protons align and respond well to the MRI’s magnetic and radio waves, making them ideal for imaging.

22. Gradient Coils Purpose: Gradient coils create small variations in the magnetic field. Spatial Encoding: These variations help locate signals from specific areas of the body. 3 Directions: Coils adjust the field along X, Y, and Z axes for precise imaging. Image Detail: Enable the creation of detailed, slice-specific images.

23. Signal Detection Detectors pick up sinusoidal signals Coils detect energy released by protons. Energy is converted into electrical signals. Signals are processed to create images Converted into images using mathematical methods

24. Importance of Water and Fat Hydrogen-rich: Water and fat provide strong MRI signals. Contrast: Differences in water and fat help create clear images. Diagnosis: Helps identify tissue types and abnormalities.

25. MRI Applications - Neurological imaging - Cardiac assessments - Oncology diagnostics

26. Advantages - High-resolution images - No ionizing radiation - Versatile imaging planes

27. Limitations - Expensive - Time-consuming - Not suitable for patients with metal implants

28. Summary - MRI uses magnetism and resonance - Provides detailed internal body images - Revolutionized medical diagnostics