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C. U. N. Y. Brooklyn College The Westchester MRI IncidentIndividual projectOctober 15, 2001 Course: Software Methodology – CIS 763 Fall 2001 Instructor: Dr. D. Kopec Student: Ludovic Pop
Contents 1. Introduction. 2. Magnetic Resonance Imaging. 2.1 MRI Description. 2.2 Magnet Intensity. 2.3 Magnet Types. 3. Technology. 3.1 Atoms and Radio – Frequency. 3.2 Visualization. 4. Incident Description. 5. Comments and Recommendations. 6. Conclusions. 7. References.
The Westchester MRI Incident 1. Introduction Medical errors rank among the Nation's leading causes of death and injury. More people die from medical errors than from other causes. My individual project emphasizes a particular case of medical failures. It is about a tragic accident happened in July 30, 2001 at the Westchester Medical Center where a 6 year old boy was killed during the MRI by a metal oxygen tank. The tank, about the size of a fire extinguisher, became magnetized, then flew through the air at 20 to 30 feet per second and fractured the boy's skull. MRI (Magnetic Resonance Imagining) machine combines magnets, pulsed radio- wave transmissions and computers to produce images of how things look inside the body. Despite numerous safety warnings issued by the manufacturers, still, there have been several accidents, some of them fatal, involving ferromagnetic objects being pulled into imaging magnets.
2.Magnetic Resonance Imaging MRI Scheme Shim Coils – Coils used to correct imperfections in the magnet.Gradient Coil – Coils used to change the strength of the magnet field inside the bore of the magnet. RF Coils – Coils that are used to transmit and receive radio frequency.
There is a horizontal tube running through the magnet from front to back. This tube is known as the bore of the magnet. The patient, lying on his or her back, slides into the bore on a special table. Once the body part to be scanned is in the exact center of the magnetic field, the scan can begin. The MRI system goes through the patient's body point by point, building up a 2-D or 3-D map of tissue types. It then integrates all of this information MRI provides an unparalleled view inside the human body. The level of detail we can see is extraordinary compared with any other imaging modality. MRI is the method of choice for the diagnosis of many types of injuries.
MRI scanners vary in size and shape, and newer models have some degree of openness around the sides. It is specially destined for people who can not be scanned with thestandard machine ( too big, claustrophobics, etc.), but the basic design is the same. MRI systems are very, very expensive to purchase. Open edges MRI Machine
Magnetic IntensityThe biggest and most important component in an MRI system is the magnet. The magnet in an MRI system is rated using a unit of measure known as a Tesla. Another unit of measure commonly used with magnets is the gauss (1 Tesla = 10,000 gauss). The magnets in use today in MRI are in the 0.5-Tesla to 2.0-Tesla range. The MRI suite can be a very dangerous place if strict precautions are not observed. Metal objects can become dangerous projectiles if they are taken into the scan room.For example, paperclips, pens, keys, scissors, hemostats, stethoscopes and any other small objects can be pulled out of pockets and off the body without warning, at which point they fly toward the opening of the magnet (where the patient is placed) at very high speeds, posing a threat to everyone in the room.
Credit cards, bank cards and anything else with magnetic encoding will be erased by most MRI systems. Prior to allowing a patient or support staff member into the scan room, he or she is thoroughly screened for metal objects. Often, the patients have implants inside their bodies that make it very dangerous for them to be in the presence of a strong magnetic field. Metallic fragments in the eye are very dangerous because moving those fragments could cause eye damage or blindness. Some people cannot be scanned or even go near the scanner because the magnet can cause problems Eg. People with a fragment of metal in the eye, with clips in the brain, with some dental implants, orthopedic implants, etc.
A fully loaded pallet jack that has been sucked into the bore of an MRI System The magnetic force exerted on an object increases exponentially as it nears the magnet. The more mass an object has, the more dangerous it can be (the force with which it is attracted to the magnet is much stronger). Mop buckets, vacuum cleaners, oxygen tanks, pallet jacks ,etc. have all been pulled into the magnetic fields of MRI machines.
Magnet Types There are three basic types of magnets used in MRI systems: Resistive magnets consist of many coils of wire wrapped around a cylinder or bore through which an electric current is passed. This causes a magnetic field to be generated.If the electricity is turned off, the magnetic field dies out. These magnets are lower in cost , but require huge amounts of electricity to operate. Permanent magnet. It is permanent and its magnetic field is always there and always on full strength, so it costs nothing to maintain the field. A stronger field would require a magnet extremely heavy and it would be difficult to construct.
Permanent magnets are getting smaller,but are still limited to low field strengths. Superconducting magnets are by far the most commonly used. It is somewhat similar to a resistive magnet coils of wire through which a current of electricity is passed to create the magnetic field. The important difference is that the wire is continually bathed in liquid helium at 452.4 degrees below zero. Superconductive systems are still very expensive, but have higher-quality imaging.
A diagram of a superconducting magnet; the main field in a whole-bod superconducting magnet in parallel to the long axis of the patient.
3. Technology Atoms and Radio - FrequencyInside the bore of the scanner, the magnetic field runs straight down the center of the tube in which we place the patient. This means that if a patient is lying on his or her back in the scanner, the hydrogen protons in his or her body will line up in the direction of either the feet or the head. The vast majority of these protons will cancel each otherout Only a couple of protons out of every million are not canceled out. This is not to much, but the whole number of hydrogen atoms in the body gives high quality images. The MRI machine applies an RF (radio frequency) pulse that is specific only to hydrogen. The system directs the pulse toward the area of the body we want to examine.The pulse causes the protons in that area to absorb the energy required to make them spin in a different direction. The RF pulse forces them to spin at a particular frequency, in a particular direction These RF pulses are usually applied through a coil.
The RF pulse forces them to spin at a particular frequency, in a particular direction These RF pulses are usually applied through a coil. MRI machines come with many different coils designed for different parts of the body: knees, shoulders,wrists, heads, necks and so on. These coils usually conform to the contour of the body part being imaged, or at least reside very close to it during the exam. MRI machines are very precise and can "slice" any part of the body in any direction. Visualization MRI machines can image in any plane. CT is limited to one plane, the axial plane. An MRI system can create axial images as well as images in the sagitall plan and coronally.
Gradient coils Gx, Gy, and Gz interact upon the magnetized and collectively create a preselected spatial excitation
4. Incident DescriptionThis description is about a recently accident happened (August 2001) at Westchester Medical Center where a six-year-old boy was killed when the magnet from an MRI machine pulled a metal oxygen tank across a room, crushing the child's head. The patient, a six-year old child, was transferred from Phelps Hospital to Westchester Medical Center on 7/24/01. The record reflects that a CT Scan done before demonstrated a right-sided cystic lesion on the right side of the brain. The patient was scheduled for an MRI in the morning and surgery in the afternoon on 7/25/01. On 7/27/01 at 11:15 AM the patient was taken to MRI by a courier with family members in attendance. The anesthesiologist was working with the child in the patient care alcove and prepared him for the scan.
The patient was transferred into the MRI room. The technologist assisted with preparation of the room and the patient; the oxygen flowmeter was turned on; the pulse oximeter was attached to the patient.The patient was placed into the tunnel of the scanner. The monitor in the room measures oxygen saturation of the patient’s blood, the heart rate and end tidal carbon dioxide. The technologist left the MRI room to go into the Console Room to start the MRI study; the anesthesiologist remained in the MRI room with the patient. Immediately, the anesthesiologist attempted to turn the oxygen flowmeter to 4 Liters without any success. As there was no direct microphone communication between the MRI technologist and the anesthesiologist (lack of communication), the anesthesiologist knocked on the window between the MRI room and the Console Room to get the technologist’s attention.
The technologist responded by leaving the Console Room and going to the door of the MRI room. The anesthesiologist informed the technologist he had no oxygen. The technologist left the MRI room, walked through the Console Room into the Computer Room (which is the location of the oxygen flow into the MRI room). The source of this oxygen was from H cylinders secured to the wall with a connection through a line into the MRI room with a flowmeter on the inside wall of the MRI room. There was a gauge above the tank to indicate the psi of oxygen in the cylinder. There is no gauge to indicate psi attached to the flowmeter in the MRI room. A nurse preparing to leave the MRI suite was passing the door, which she observed to be wide open, saw and heard the anesthesiologist. In response to the apparent urgency of his concern the nurse noticed 2 E cylinders in a hand cart on the floor in the patient care alcove across the hall from the door of the MRI.
She recalls one was empty and one was 3/4 full. The nurse recalls lifting the cylinder by the regulator and transferring it to the anesthesiologist. At approximately 12:15 PM the oxygen cylinderwas introduced into the magnetic field surrounding the MRI machine (MM) and was drawn to the core of the magnet causing head trauma to the patient. The nurse recalls that the anesthesiologist took the oxygen cylinder from her while she was in the hallway. She states she is not certain as to how many inches or feet he may have been from the inside of the MRI room or out of the doorway. The anesthesiologist recalls that a nurse brought the cylinder into the MRI room. As it was being drawn into the bore of the magnet he tried to catch it but could not.
It is uncertain as to exactly where the anesthesiologist was standing at the time of the transfer. After the patient was injured, he was pulled from the MM tunnel and carried to the patient care alcove immediately adjacent to the MM room and was observed to have facial trauma and bleeding around his mouth. He was quickly intubated by the anesthesiologist and ventilated. The patient was transferred to the Emergency Department and after to the Pediatric Intensive Care Unit and was treated with maximal medical therapy; he remained in critical condition with a poor prognosis. The brain death protocol was initiated and the patient was pronounced dead at 5:40PM on 7/29/01.
5. Comments and Recommendation C:The delivery of oxygen safely to the patients during performance of MRI was not effective. 2-H cylinders secured to the wall in the computer room were the source for oxygen for patients during MRI scanning. The practice was to change the cylinder when it was at or below 500 psi. R:Remove the H cylinders as the oxygen source for patients during MRI. Only non-ferrous oxygen cylinders will be used for those patients requiring oxygen during the scan. The patients requiring oxygen will be met at the entrance of the MRI unit by trained personnel who will transfer the patient from the regular hospital cylinder to a non-ferrous aluminum cylinder and escort patient into MRI Suite. When the patient’s study has been completed the patient will be switched from MRI compatible tank to either a hospital cylinder or to the patient’s own tank outside the MRI area.
C:The general practice was to replace the H cylinder when the gauge indicated the tank was at 500 psi. When the patient first entered the MRI room the flowmeter was turned on and indicated oxygen flow. Immediately before the scanning was begun the anesthesiologist attempted to increase the flow without success. R: The source for patient requiring oxygen during a MRI scan will be exclusively non-ferrous cylinders. A full non-ferrous E cylinder will be provided for each patient.It will be the responsibility of the MRI technologist or nurse to ensure a full cylinder for each patient. MRI personnel will monitor pressure readings of the tank in use every few minutes; if the reading reaches 500 psi, the tank will be replaced with a full cylinder.
The Department must write policies and procedures related to MRI scanning and safety ( specifically related to the provision of oxygen during the MRI scan ) also include training of responsible personnel ( current staff and new staff ). C:Communication was no effective. Communication between a person other that the patient in MRI room during the scan was achieved by that knocking on the window between the MRI and Console Room to attract the attention of the MRI technologist. R:Install a compatible communication among MRI responsible personnel ( microphones, speakers and even a hazard pushing button, painted in red, which in case of emergency will turn off the system).
6. Conclusions Regarding the tragic accident at Westchester Medical Center we may conclude that some failures have occurred at that time: - A poorly designed oxygen delivery and monitoring system that filed to ensure the continuous delivery of oxygen - The storage of MRI incompatible material in the MRI Suite. - The failure to safely identify and safely secure the restricted magnetic field area.
- Ineffective education of both hospital and non-hospital staff regarding the dangers associated with MRI magnetic field. - Ineffective communication system impeded the anesthesiologist who tried to communicate his concern for the patient’s safety to others in the MRI Suite. In order to avoid others accidents in the future we have to concentrate more to the tasks that we have to fulfill every day.
7. References1. Vadim Kuperman. Magnetic Resonance Imaging. University of Chicago, Illinois Academic Press. 2000.2 .James Mattson and Merrill Simon. The Pioneers of NMR and MRI. The Story of MRI. Bar-Ilan University Press. Jericho, NY 1996. 3. Rayh Hashemi and William G. Bradley, jr. Harbor City and Long Beach CA. 1997.4. Kenneth S. Meacham. The MRI Study Guide for Technologists. Springer-Verlay.NY. Atlanta GA. 1995.5. David W. Chen. Boy, 6, Dies Of Skull Injury During MRI. New York Times.6.30.01 6. Jose Martinez, Susan Ferraro and Corky Siemaszko. Freak. MRI accident Kills Westchester boy. Daily News Tuesday, July 31.2001.7. Peggy Woodward. MRI for Technologists ( sec. edition). Mc Graw Hill Comp. 2001. 8. M.T. Vlaardingerbroek .Magnetic Resonance Imaging. Springer-Verlay. Berlin 1996.
