MRI Flashcards

Question

What is in place to make aware that helium has leaked?

Answer 1

The monitor will alarm if O2 is below 19% Sensor and filter need to be replaced - if not alarm may go off

Answer 2

Get out oxygen and turn off magnets This is because of risk of combustion in the environment and fire services need to get in so the magnet needs to be turned off because of their equipment

Answer 3

Liquid helium rapidly boils off through quench pipe – slowly eliminating magnetic field Can be spontaneous or deliberate Severe damage to the magnet or gradient coils may occur Cost is 30,000+ Magnet downtime is five days plus

Answer 4

Explosion and asphyxiation - this is why the quench pipe is serviced regularly Liquid helenium boiling off can also cause the volume of helium to increase up to 700 times - Some of the quench pipe feels this may create a huge pressure buildup in magnet room - Should this happen doors that open inwards will not open due to the pressure - that’s why doors in the MR environment should open outwards either fully or partially

Answer 5

Projectiles Implants Magnetohydrodynamic effect

Answer 6

World health organisation International condition or not ionising radiation protection – ICNIRP International electoraltechnical commission

Answer 7

UK medicines and healthcare regularity authority - MHRA UK health protection agency – HPA Institute of physics and engineering in medicine - IPEM British Association of MR Radiographers - BAMRR Society and college of radiographers -SCoR

Answer 8

Radiation safety committee MR safety committee Local rules - implementation of policy - delegation of responsibilities - authorisation of personnel -Standard operating procedures

Answer 9

Clinical Emma I magnets are very strong and produce a powerful attractive force on ferrous metals The magnetic field extend well beyond the board of the magnet Items such as: pens, keys, scissors, mobiles - missals Metal plus magnet that quickly missals into magnet Larger items such as o2 cylinders, wheelchairs … And will be strongly feel towards magnet

Answer 10

Only items that come into the magnet room are tested and marked as MR safe – MR conditional – MR unsafe Anything without with markings must be considered unsafe to take into the MRI environment

Answer 11

Anyone entering the MRI environment with an active implant device such as: Peacemakers Implantable cardiac defibrillator – ICD Cardiac loop recorder Neurostimulator Impossible drug infusion pump Programmable hydrocephalus shunt Middle ear implant Anyone with an Aneurysm clip in the brain Anyone with shrapnel in the globe of the eye

Answer 12

MRI safety questionnaire Authorised personnel Controlled Areas

Answer 13

Everyone active ever environment must be screened prior to entry – there are no exceptions to this Groups include patient Staff including estates and external contractors Screening questionnaires should be signed by the individual and countersigned by an authorised person when they have satisfied themselves that all information is verified

Answer 14

A suitable trained member of staff authorised to have the access to the MR controlled area Authorised person – non-MR environment - May not enter without supervision Authorised person – MR environment - May enter Authorised person – supervisor - May enter and supervise

Answer 15

Delegated the day-to-day responsibility of MRI safety by the chief executive or head of organisation in writing What are the main duties is the train and approve MR authorised persons Often a senior individual such as principal medical physicist or consultant radiologist

Answer 16

This is a separate role from responsible person At the Emma safety expert will have a knowledge of Emma and I technique is an appropriate understanding of the clinical applications – ideally they will be a physicist with expertise in MRI MR safety expert should be in a position to adequately advise on the necessary engineering scientific and administrative aspects of the safe clinical use of MR devices

Answer 17

When I electrically conductive fluid (blood) moves within a magnetic field and electrical current is produced It can cause staff that work in the MR environment: Vertical, nausea, phosphenes Worse at High fields Staff may experience dizziness when leaning into the board of the magnet

Answer 18

Tissue or nerve stimulation Acoustic noise

Answer 19

Specially in called Ama signals also in generate an electric current within the body May cause tingling/twitching sensation in fingers and toes - but the MR systems warn operators when this may occur Most commonly occurs when using echoplanar imaging techniques: Diffusion weighted imaging diffusion tenser imaging functional MRI

Answer 20

Gradient switching generates acoustic noise as a byproduct Sound pressure levers can Reach 115 DB Health and safety legislation requires hearing protection to be worn when exposed to side pressures level over 90 DB This is managed by using earplugs and/or headphones

Answer 21

Specific absorbing rate - SAR Induced loops and RF Burns

Answer 22

RF is used to excite hydrogen Our F – deposit heat in body tissues the heat is then removed removed via blood flow – convection Rate of heat disposition – SAR – watts per kilo should not exceed 2W–KG -1

Answer 23

Induced current may occur in conducting loops in cables, wires and even body parts Where there is a thin area of contact that electrons skin on skin contact this generates heat This is a risk of RF burns

Answer 24

Am I specific fireplug their house to control names of each department Firefighters know that they cannot enter the Emma environment without the advice of a present authorised person Isolate medical gases and quench magnet Fire extinguisher must be done within controlled areas

Answer 25

In cardiac arrest situations the patient must be removed immediately bearing in mind that manual handling procedures should always be adhered to MR safe evacuation trolley On some the couch can be removed Patient taken into the controlled area where resus/CPR can commence Door locked

Answer 26

Superconducting magnets are always on Controlled areas are there for the safety of all users of the department If you doubt - No entry

Answer 27

Always locked Staff ID badge or keypad to unlock Emergency exit

Answer 28

Go through entire screening form and countersign Patient weight and height to determine the power/Safe limit of radio frequency Patient clothes/artefacts are removed Get rid of loose metal – keys coins, phone, wallet, loose jewellery Cannulation if required

Answer 29

Clean Course selection Immobilisation equipment that sandbags cushion Velcro Contrast pump injector – filled up and ready to go Getting equipment for cardiac or respiratory - EKG Tracing oxygen - tube in room Monitoring– MR safe monitor

Answer 30

All metal removed Manual handling equipment required: MR safe wheelchair Turntable Glide sheet Bed ladder Pat slide for lateral transfers Position position of the magnet couch Earplugs and headphones Contact buzzer Place coil over the part to be scanned making sure that cables are not stretched Pads between cables and bear skin Move patient into the magnet slowly dash to the juice dizziness Communicate – are they still okay comfortable happy to proceed

Answer 31

Check the patient can hear over intercom Would the patient like to listen to music Warn of noises before commencing the scan Blinds - privacy

Answer 32

Radio-frequency – hydrogen – signal back Gs – slice direction Gr - readout direction Gp - phase direction Pulse - readout (signal)

Answer 33

Echo time (TE) - raw data - manipulate + record Line of raw data per pulse - repeated multiple times - image ( empty spaces - k-space) Middle - contrast - quick scan dynamic contrast Outer - resolution

Answer 34

Front end up at the back of the image – happens in face directional scan To fix that you did a larger field of view or NPW Oversampling – extra data – get rid of it

Answer 35

Some artefacts can mimic pathologies Artefacts that are easily solved such as motion artefacts and phase wrap Other require engineers to correct such as hardware, electrical or software defects Cosmo magnetic susceptibility differences in tissue can create field inhomogeneities at the interface Made much worse on sequences with long echo times – EPI, DTI, DWI, FMRI Often naturally occurs at air-tissue interfaces such as in the sinuses

Answer 36

Saturation pulses are bursts of RF energy used to actively suppress signal from selected tissues. Selective saturation can be used on the oesophagus to eliminate swallowing artefacts Often placed above and below fields of view (fov) to suppress flowing blood entering the slice. They can also be use to suppress venous flow in Time of Flight (ToF) angiography (MRA) sequences.

Answer 37

Involuntary wave-like motion used to transit food through the bowel. There are 2 methods to restrict this, scanning the patient in a prone position and by using an inhibiting drug such as Hyoscine Butylbromide (Buscopan) Buscopan is also regularly administered by Radiographers via a Patient Group Direction (PGD) for CT procedures and for fluroscopic bowel exams.

Answer 38

There are many ways to attempt to correct for this: Increasing the number of Excitations (NEX) Breath holding Respiratory triggering using bellows (Long TR) – Hardware solution that synchronises the acquisition with the patient’s breath.

Answer 39

This is a software based solution The navigator is placed at the top of the liver to trigger the acquisition whilst the patient breathes freely. This can sometimes take a while to do (up to 9ish minutes per sequence – best put the kettle on) This technique is often used for scanning of the abdominal organs, the chest and mediastinum and whole body imaging.

Answer 40

Cardiac gating is essential for cardiac MR studies 3 or 4 lead ECG devices are attached to the patient’s chest and the sequences pulses are triggered from the r wave of the ECG trace. Alternatively a Peripheral Pulse Unit (PPU) or pulse oximetry sensor can be attached to the patients fingers or toes though this is far less effective for cardiac imaging Can be useful for Neurology applications such as Diffusion Tensor Imaging or CSF flow studies. Cardiac Arrhythmias cause symptoms in Radiographers that include mild profanity up to loudly expressed expletives. (And images like these)

MRI Flashcards

(64 cards)