Mri safety

This ppt is related to MRI safety and brief history of MRI

1. MRI SAFETY Anupam Niraula

2. CONTAINS: Introduction Brief History Major Components Safety

3. Introduction: MRI stands for “Magnetic Resonance Imaging”. Originally know as “Nuclear Magnetic Resonance”(NMR) Used in medical field to produce image of internal structures of living organism.

4. HISTORY: Isidor Isaac Rabi an American physicist – First described NMR phenomenon in 1938. A Swiss-American physicist Felix Bloch and an American physicist Edward Purcell independently discovered the magnetic resonance phenomenon during the year (1946 AD) In 1970 AD, another American physician and medical practitioner Raymond Vahan Damadian used NMR for malignant tissues and found difference in NMR parameters. Damadian and his team invented the first NMR scanner named as Indomitable in which the first image of human body was acquired. The first person to undergo NMR was Larry Minkoff who was an assistant of Damadian . Paul Christian Lauterbur an American chemist and Sir Peter Mansfield an English physicist were also working in the same field and were the persons responsible for introducing MRI into the clinical set-up.

5. SIR PETER MANSFIELD RAYMOND DAMADIAN EDWARD PURCELL FELIX BLOCH PAUL LAUTERBUR ISIDOR ISAAC RABI

6. MAJOR COMPONENTS OF MRI: BORE: Magnet Coils (gradient coils , RF coils , Shimming coils) MRI table Chelates Console: Computer hardware Operating system

7. Magnet: A piece of iron or other material which has its component atoms so ordered that the material exhibits properties of magnetism, such as attracting other iron-containing objects or aligning itself in an external magnetic field. Discovery: shepherd named Magnes , in an area of Northern Greece called Magnesia , about 4,000 years ago.  Lodestones contain magnetite , a natural magnetic material Fe3O4. This type of rock was subsequently named magnetite, after either Magnesia or Magnes himself . The most significant difference between the magnetic field and the magnetic flux is that the magnetic field is the region around the magnet where the moving charge experiences a force, whereas the magnetic flux shows the quantity or strength of magnetic lines produced by the magnet. Magnetic flux density is measured in Tesla. One Tesla = 10000 gauss

8. GUASS LINE

9. TYPES OF MAGNET: Permanent Magnet – 0.064 T to 0.3 T Resistive Magnet – up to 0.3 T Super conductive Magnet- up to 12 T

10. SUPER CONDUCTIVE MAGNATE: Utilize the property of Zero electrical resistance exhibited by certain materials like ( Niobium Titanium ) Loop of wire is surrounded with coolant, such as liquid Helium , liquid nitrogen ( cryogen ), to reduce the electric resistance of the wire . At 4 degree kelvin (-269 degree c) wire loses its resistance. High current (760 A) at low voltage is required to convert them into superconductive – Ramping Super conductivity under low temperature was first observed by Argentinean Alex Muller and German George Bednorz.

11. MRI SAFETY MRI ZONES FARADEY CAGE PATIENT SAFETY MAJOR ACCIDENTS PREVENTATION OF ACCIDENT

12. SAFETY SIGN IN ZONE 3

13. FARADAY CAGE : A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields . A Faraday shield may be formed by a continuous covering of conductive material or in the case of a Faraday cage, by a mesh of such materials . Faraday cages come in all shapes and sizes, but all of them use a metal screen that conducts electricity, creating a shielding effect.

14. How faraday cage works? Faraday cage distributes charge or  radiation  around the cage's exterior, it cancels out electric charges or radiation within the cage's interior. In short, a Faraday cage is a hollow conductor, in which the charge remains on the external surface of the cage.

15. Note: In mri faraday cage is build for rf shielding RF shielding is important because: To prevent extraneous electromagnetic field (RF) from contaminating the MR signal. To prevent electromagnetic radiation generated by MR machine from causing interference in nearby medical devices.

16. The ideal room consist of nested components: 1)An outer shell for structural support 2) A middle metallic RF-shield 3)An interior layer made of finish materials. The floor is generally made of monolithic copper covered over with solid material. Door must not allow any RF leakage, being shield by a set of electrical contact strips or continuous metallic pneumatic tube. Window are laminated with blackened copper mesh between two pieces of glass. Virtually any metal can be used including aluminum and steel but copper is generally used because it is more conductive metal.

17. Patient safety: 1)Informed consent 2)Patient history (medical history , claustrophobia) 3)Patient screening 4)Changing in hospital gown 5)Use of MRI compatible devices .

18. RF BURNS RISK DUE TO METALLIC BODY IMPLANTS AND LOOSE METALLIC BODIES

19. MRI Accident : 1 st MRI accident occurred in New-York area hospital in 2001 July . A six year old boy , Michael Colombini lost his life when the machine's powerful magnetic field jerked a metal oxygen tank across the room, crushing the child's head. In India latest MRI accident that took a life of a person named Rajesh Maru happened in 2018 in Nair hospital Mumbai.

20. MRI Machine At Lohiya Hospital Pulls UP textile Min Satyadev Pachauri's guard’s Pistol When He Came For MRI Accident at Nair Hospital ,Mumbai MISSILE EFFECT

21. What to do if accident happens ? Inform authority or higher level officer ASAP. Switch off system and all electronic but remember switching system doesn't mean magnate is off. c) Find alternate of Quenching. d) Do not quench machine in hurry unless its life threatening situation. Ramp –down of machine is often done by service engineer. In a controlled manner, current can be brought down from conductor to bring field zero. Ramping takes approx. 20 min for every 0.5 T.

22. Quench A quench is an event that occurs only in superconducting magnates and results in a loss of magnetic field of the MRI magnet. It is caused by a loss of superconductivity , a rapid increase in the resistivity of the magnet coil windings, which generates heat that results in rapid evaporation, or boil-off of the magnet coolant. There are two situation in which quench may occur: Spontaneously due to some force or disruption to the magnate system. The emergency “Magnet Stop” button is pressed during emergency situation.

23. Emergency stop button: Emergency Magnet Rundown Unit : This initiates a controlled quench and turns off the magnetic field. It is typically a big red button located on the wall of the magnet room near the door. This button should only be used in a life threating situation. Pressing this button makes the scanner out of service costing heavily for replacing lost liquid helium.

24. Emergency shutdown : Does not quench the magnet but turns off most electrical power in the scanner room and operator area, including the console ,computers , patient table , ups etc. It may be simple red button labeled or unlabeled This switch should b used when there is serious equipment fault or hazard ,such as fire , water in the vicinity of the MR scanner

25. Preventation of Accident PATIENT MUST BE SCREENED THROUGH METAL DETECTOR OR PASS THROUGH GATE BEFORE ENTERING 4 TH ZONE INFORMED CONSENT SHOULD BE TAKEN REGARDING HISTORY OF ANY PREVIOUS SURGERY AND METALLIC IMPLANTS WARNING SIGNS SHOULD BE PLACED ON 3 RD ZONE DISPLAYING THE RESTRICTED ITEMS THAT CAN’T BE TAKEN INSIDE MRI ROOM

26. “ MRI CAN BE ACCIDENT PRONE FOLLOW RULES OF SAFETY ZONE ” “MRI CAN TURN INTO MONSTER ,IT IS IN OUR HAND TO STOP DISASTER ”

27. THANK-YOU!!!