Presentation on theme: "In The Name of Allah The Most Beneficent The Most Merciful"— Presentation transcript:
1In The Name of Allah The Most Beneficent The Most Merciful
2M.R.I Magnetic Resonance Imaging Group Members:EE M Aqil YousafEE M TalhaM.R.I Magnetic Resonance Imaging
3Introduction In this presentation the topic under discussion will be MRI introductionNuclear Spin PropertiesBlock DiagramApplicationsLimitations
4Intensity wise differentiation MRIMRI introductionMagnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the bodyIntensity wise differentiationFat high (whitish)Muscle intermediate (gray)Ligaments & Tendons low (dark gray)Immature Scar intermediate - low
5MRI introductionHistory BackgroundIn the 1950s, Herman Carr reported on the creation of a one-dimensional MRI image. Paul Lauterbur expanded on Carr's technique and developed a way to generate the first MRI images, in 2D and 3D, using gradients. In 1973, Lauterbur published the first nuclear magnetic resonance image. and the first cross-sectional image of a living mouse was published in January 1974
6Procedure MRI introduction Magnetic nuclei are abundant in the human body (H,C,Na,P,K) and spin randomlySince most of the body is H2O, the Hydrogen nucleus is especially prevalentPatient is placed in a static magnetic fieldMagnetized protons (spinning H nuclei) in the patient align in this field like compass needlesRadio frequency (RF) pulses then bombard the magnetized nuclei causing them to flip aroundThe nuclei absorb the RF energy and enter an excited stateWhen the magnet is turned off, excited nuclei return to normal state & give off RF energyThe energy given off reflect the number of protons in a “slice” of tissueDifferent tissues absorb & give off different amounts of RF energy (different resonances)The RF energy given off is picked up by the receiver coil & transformed into images
8What kinds of nuclei can be used for ? MRI introductionWhat kinds of nuclei can be used for ?Nucleus needs to have 2 properties:SpinchargeNuclei are made of protons and neutronsBoth have spin ½Protons have chargePairs of spins tend to cancel, so only atoms with an odd number of protons or neutrons have spinGood MR nuclei are 1H, 13C, 19F, 23Na, 31P
9Hydrogen atoms are best for MRI Nuclear Spin PropertiesHydrogen atoms are best for MRIBiological tissues are predominantly 12C, 16O, 1H, and 14NHydrogen atom is the only major species that is MR sensitiveHydrogen is the most abundant atom in the bodyThe majority of hydrogen is in water (H2O)Essentially all MRI is hydrogen (proton) imaging
10A Single Proton Nuclear Spin Properties m There is electric chargeon the surface of the proton, thus creating a small current loop and generating magnetic moment m.The proton also has mass which generates anangular momentumJ when it is spinning.J+++Thus proton “magnet” differs from the magnetic bar in that italso possesses angular momentum caused by spinning.
11How do protons interact with a magnetic field ? Nuclear Spin PropertiesHow do protons interact with a magnetic field ?Moving (spinning) charged particle generates its own little magnetic fieldSuch particles will tend to line up with external magnetic field lines (think of iron filings around a magnet)Spinning particles with mass have angular momentumAngular momentum resists attempts to change the spin orientation (think of a gyroscope)
12Machine WorkingMagnetic Resonance Imaging (MRI) is a non-invasive diagnostic technology that produces physiologic images based on the use of magnetic and radio frequency (RF) fields. The MRI system uses powerful magnets to create a magnetic field which forces hydrogen atoms in the body into a particular alignment (resonance). Radio frequency energy is then distributed over the patient, which is disrupted by body tissue. The disruptions correspond to varying return signals which, when processed, create the image.
13Application Clinical neurology – Segmentation and classification – Measuring volumes of brain structures– Multiple sclerosis, stroke, …Cardiology– Either need to image fast, or deal with heart motion!Cancer–colorectal, liver, prostate, …Soft tissue damage– Cartilage, ligaments, …
14Limitations of MRISome patients experience claustrophobia and have difficulty in cooperating with the study. Some obese patients cannot be examined.Some patients, particularly acutely ill patients, cannot cooperate and movement artifacts may result. Patient throughput is slow compared with other imaging modalities. Patients with pacemakers and certain ferromagnetic appliances cannot be studied.Greater technological expertise is required for performance of MRI than for most other imaging modalities. MRI equipment is expensive to purchase, maintain, and operate.Claustrophobia: Fear due to small roomObese: موٹے