Magnetic Material Engineering Magnetic Material Engineering Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic nanoparticles Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic nanoparticles Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic nanoparticles Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic nanoparticles Materials: Fe, Co, Ni, Gd Spins of unfilled d-bands spontaneously align parallel inside a domain below a critical temperature TC (Curie) Laws: B = H +4πχH M = χH χ: Susceptibility Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic nanoparticles Hard Magnets: HC and Mrs have high values Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Superparamagnetism - a size effect Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Superparamagnetism - a size effect Superparamagnetism: • high saturation magnetisation MS • no remanence MR = Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Superparamagnetism The Néel relaxation in the absence of magnetic field Normally, any ferromagnetic or ferrimagnetic material undergoes a transition to a paramagnetic state above its Curie temperature Superparamagnetism is different from this standard transition since it occurs below the Curie temperature of the material Superparamagnetism occurs in nanoparticles which are single domain This is possible when their diameter is below 3–50 nm, depending on the materials In this condition, it is considered that the magnetization of the nanoparticles is a single giant magnetic moment, sum of all the individual magnetic moments carried by the atoms of the nanoparticle Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Nanomagnetic Particle Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic Cell Separation / Cell Labeling Diagram of Immunomagnetically labeled Cell Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic Cell Separation / Cell Labeling Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Capture of bacteria by using Vancomycin-conjugated magnetic nanoparticle Control experiment Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic Drug Delivery Chapter 6: Applications in Medical and Biology Magnetic Material Engineering MRI The principles of MRI rely on the spinning of specific nuclei present in biological tissues In nuclei that have an even mass number, i.e # protons = # neutrons, half spin in one direction and half spin in the other Nucleus has no net spin However, in nucleus with odd mass #, spin directions are not equal and opposite, so the nucleus has net spin or angular momentum These are know as MR active nuclei Chapter 6: Applications in Medical and Biology Magnetic Material Engineering MRI MR active nuclei are characterized by their tendency to align their axis of rotation to an applied magnetic field This occurs because they have angular momentum or spin and, as they contain positively charged protons, they posses electrical charge The laws of electromagnetic induction refer to three individual forces – motion, magnetism and charge – and state that if two of these are present, then the third is automatically induced MR active nuclei that have a net charge and are spinning (motion), automatically acquire a magnetic moment and can align with external magnetic field The strength of the total magnetic moment is specific to every nucleus and determines the sensitivity to magnetic resonance Chapter 6: Applications in Medical and Biology Magnetic Material Engineering MRI - The hydrogen nucleus The hydrogen nucleus is the MR active nucleus used in clinical MRI It contains a single proton (atomic and mass number 1) It is used because it is most abundant in the human body and its solitary proton gives it a relatively large magnetic moment Both of these characteristics enable utilization of the maximum amount of available magnetization in the body Chapter 6: Applications in Medical and Biology Magnetic Material Engineering The hydrogen nucleus as a magnet The laws of electromagnetism state that a magnetic field is created when a charged particle moves The hydrogen atom contains one positively charged proton that spins Therefore it has a magnetic field induced around it, and acts as a small magnet It has a north and south pole Each of which is represented by a magnetic moment Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Alignment Quantum theory describes properties of electromagnetic radiation in terms of discrete quantities called quanta Applying quantum theory to MRI, hydrogen nuclei posses energy in two discrete quantities term low and high Low energy align their magnetic moments parallel to external field (spinup) High energy align anti-parallel (spin-down) Chapter 6: Applications in Medical and Biology Magnetic Material Engineering The MR signal When a patient is placed within and MR scanner, the protons in the patients tissues (primarily protons contained in water molecules) align themselves along the direction of the magnetic field A radiofrequency electromagnetic pulse is then applied, which deflects the protons off their axis along the magnetic field As the protons realign themselves with the magnetic field, a signal is produced This signal is detected by an antenna, and with the help of computer analysis, is converted into an image Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Image formation The process by which the protons realign themselves with the magnetic field is referred to as relaxation Different tissues undergo different rates of relaxation, and these differences create the contrast between different structures, and the contrast between normal and abnormal tissue, seen on MRI scans Chapter 6: Applications in Medical and Biology Magnetic Material Engineering MRI of a Female Rat Before Chapter 6: Applications in Medical and Biology After ... Biology Magnetic Material Engineering Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic. . .Magnetic Material Engineering Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic nanoparticles Chapter 6: Applications in Medical and Biology Magnetic Material. .. moments and easy axis Chapter 6: Applications in Medical and Biology Magnetic Material Engineering Magnetic anisotropy Chapter 6: Applications in Medical and Biology Magnetic Material Engineering