Magnetic Resonance Eric

8/13/2019 Magnetic Resonance Eric

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Magnetic Resonance

ImagingEric Case

Fall 2013


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History


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History

How old do you think it is?

Basic principles were proposed in the early 1920s.

Investigations continued for over 20 years with no majorbreakthroughs.

Felix Bloch and Edward Purcell separately discovered the

basic principle in solid matter during this time. Blochs technique was commercialized by 1953 and

marketed as nuclear magnetic resonance for evaluatingpharmaceuticals and chemicals.


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History

Paul Lauterbur suggested in 1973 that Blochsdiscovery could be applied to imaging.

1977 brings us the first images using this technique.

Clinical trials as an imaging tool began in 1981.

Advancements in equipment and technology are

continually changing the field even today including

PET/MRI.


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Basic Principles


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Basic principles

Every atom in the body spins on its own magnetic pole.

Hydrogen atoms are used most for imaging

When the protons of atoms are placed in a strong magnetic field, they try

to align themselves in that field

The protons are spinning as well. They start to wobble when they realign.

This is called precession

The precessing protons will absorb RF (radiofrequency) pulses when they

are applied. This absorption is called resonance.


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Basic Principles

Each precessing proton has a natural resonance. It can be

calculated using the Larmor frequency:

= B

is the frequency of precession

is a constant gyromagnetic ratio based on the nucleus

B is the strength of the magnetic field in Tesla


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Basic Principles

The RF pulse is then turned off. When this happens, the

precessing protons will return to a normal state.

As they return, they release energy. This is called relaxation.

There are two states of relaxation.


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Basic Principles

The two types of relaxation are:

Spin-lattice (T1 or longitudinal)energy is released into the generalenvironment around the proton.

This is also the time it takes to return to the net Magnetization

vector (net Mv)

Net Mv is the sum of the directions and magnitudes of themagnetic spins

Spin-Spin (T2 or transverse)energy is released inside the nuclei

Both are used in signal production. Images weighted either way willgive different kinds of information such as tissue vs. fluid


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Basic Principles

This released energy is detected by the gradient coils.

The gradient coils convert the signals to an electrical signal.

Signal strength is dependent on proton density, or the

concentration of protons The electrical signal is sent to a processing computer which

compiles the signals into the image.


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Basic Equipment


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MRI Scanner

Closed MRI


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Magnets

There are two types of magnets used in MRI:

Permanent

Electromagnetic

Magnets used in MRI have field strengths of 1.53 Tesla

Magnetic strength is also measured in gauss. The Earths magnetic field measures 0.5 gauss.

1 Telsa = 10,000 gauss


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Magnets

These are Neodymium Rare Earth Magnets. They have thealmost the same magnetic strength as a scanner, but their size

reduces the magnetic field.

They have a field strength of 1.3 Tesla.


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Equipment cont.

Open MRI Machines


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Other Equipment

Head Coil

Extremity Coils

Torso Coil


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Control Room


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Common Procedures


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Brain MRI is the preferred method for imaging the Central Nervous System

Since it images tissues so well, the radiologists can tell the difference

between white and gray matter

Indicated for tissue pathologies, i.e. tumor, inflammation, distention,

malfunction


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Spine

Indicated for spinal pathologies, i.e. tumor, inflammation, osseousdeformity or trauma


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Chest

Able to provide great definition of the cardiac and lung tissue

Mainly used in Cardiology

Other indications for tissue pathologies, i.e. tumor, inflammation,

distention, malfunction


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Abdomen

Indicated for tissue pathologies, i.e. tumor, inflammation, distention,malfunction


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Pelvis

Indicated for tissue pathologies, i.e. tumor, inflammation, distention,malfunction


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Extremities

Great distinction between soft tissue and bone

Useful in diagnosing tissue injuries


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Typical Activities


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Typical activities

Radiographer

Patient preparation and screening

Equipment inspection and safety

Patient history gathering Communication with radiologists and other staff

Performing exams

Basic housekeeping


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Typical activities

Radiologist

Typically not in the room during the exam

Reads the exam from a PACS workstation with enhanced monitors

Prepares the report and makes findings available to the ordering physician Answers any questions from the ordering physician or their staff


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Patient Care


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Before the exam

Verify order Ensure exam room is ready and get patient

Complete MRI checklist with patient

Properly dress patient

Advise patient on what will happen

Address any concerns with the patient


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During the exam..

Ensure patient remains calm

and still during the exam.

Monitor patient


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Slide Master


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After the exam

Address any concerns the patient had Inform them of any post procedure instructions

Assist patient with getting dressed if necessary

Follow up on any concerns the patient had


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Contrast notes

Gadolinium is the preferred contrast agent Barium is not used because.

It cannot be injected!

It will no appear on some T1 or T2 weighted exams


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Radiation Protection

There is no way to protect the patient from radiation because

There is no radiation!

However, there are some very critical safety concerns with MRI.

Some deal with patient safety, others with equipment safety.


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Device Categories

MRI Safe

Any device that is

safe entering a 1.5T

exam room

Devices must have

been tested and

approved

MRI Conditional

Seven different sub-

categories

Devices are rated

based on their ferrous

affinity May or may not pose a

threat to the patient or

others

MRI Unsafe

Devices pose a

significant danger

in the presence of

a magnetic field

Two different sub-categories

Severe

complications may

arise


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Patient Safety

Patients need to be screened before having an MRI. Why? We need to know what, if any, metal objects are on or in them.

Some possibilities of danger are flying objects, forced removal from

the body, burns from heating and malfunction of implants.

Checklists help the technologists accomplish this.


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Screening Checklist

MRI Checklist Sample!!!!


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Equipment Safety

All ancillary equipment that enters the exam room MUST be MRIcompliant!

This includes carts, oxygen tanks, chairs and IV poles to name a few.


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Safety Videos

http://www.youtube.com/watch?v=lEJ2notNLo0\

http://www.youtube.com/watch?v=byRIwDk21sw
http://www.youtube.com/watch?v=lEJ2notNLo0/http://www.youtube.com/watch?v=byRIwDk21swhttp://www.youtube.com/watch?v=byRIwDk21swhttp://www.youtube.com/watch?v=byRIwDk21swhttp://www.youtube.com/watch?v=lEJ2notNLo0/http://www.youtube.com/watch?v=lEJ2notNLo0/http://www.youtube.com/watch?v=lEJ2notNLo0/


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Back to the Neodymium

This could be interesting!

http://www.youtube.com/watch?v=L00t5nuy2JE
http://www.youtube.com/watch?v=L00t5nuy2JEhttp://www.youtube.com/watch?v=L00t5nuy2JEhttp://www.youtube.com/watch?v=L00t5nuy2JE


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EducationalRequirements


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Basic Requirements

Standards are changing January 1, 2014 Must hold current certification in Radiography, Nuclear Medicine,

Sonography, or Radiation Therapy or have completed a bachelors program

within the last three years

Beginning in 2016, candidates must also complete 16 hours of structured

training


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Clinical Requirements

The Clinical Experience Requirements for MRI consist of 53 procedures in seven

different categories. The seven categories include: A. Head and Neck

B. Spine

C. Thorax

D. Abdomen and Pelvis

E. Musculoskeletal

F. Special Imaging Procedures

G. Quality Control


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Clinical Requirements, Cont.

Candidates must document the performance of complete, diagnostic-qualityprocedures according to the following rules:

Choose a minimum of 25 different procedures out of the 53 availableprocedures

Complete and document a minimum of three and a maximum of fiverepetitions of each chosen procedure; less than three will not be counted.

Complete a total of 125 repetitions across all procedures.

No more than one procedure may be documented on one patient. For example, ifan order requests an MRI of the Head and Neck for one patient, only one of these,including the post-processing procedures, can be documented for clinicalexperience documentation.


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Examination

Application for exam is mailed to the ARRT once requirements are met

Application is reviewed for completeness and a 90 day testing window is

scheduled

Exam is 200 questions

Candidates are allowed three attempts within a three year window


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Comparisons ToDiagnostic Radiography


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Comparisons

Uses ionizing radiation to produce

the image

Uses magnetic fields and RF pulses to

produce the image

Two-dimensional Three-dimensional

Patient manipulation required toshow area of interest

Patient movement is detrimental tothe exam

No new significant progression in

technique

New understanding and technology

has created new techniques, i.e.

PET/MRI

Tissues superimpose on imageCertain frequencies can be omitted

for tissue visualization

Both require anatomical knowledge, computer skills, technological training

and outstanding patient care

Diagnostic Radiography MRI


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Quiz time!!


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Question 1

Radiation protection is important in MRI because:a. Reduces patient dose

b. Reduces radiographer dose

c. ALARA still applies

d. None of the above

Answer : D

i


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Question 2

Magnetic Resonance was first realized in the :a. 1920s

b. 1940s

c. 1960s

d. 1970s

Answer : A

Q i 3


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Question 3

Only MRI ___________ equipment is allowed in the exam room.a. Conditional

b. Compliant

c. Coordinated

d. Any equipment is allowed

Answer : B

Q i 4


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Question 4

Certification requirements for MRI are changing in:a. 2014

b. 2016

c. Both

d. Neither

Answer : C

Q ti 5


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Question 5

The spin-lattice relaxation process is also known as :a. T1

b. Rest time

c. T2

d. Sequestration time

Answer : A

Q ti 6


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Question 6

The spin-spin relaxation process is also known as :a. T1

b. Rest time

c. T2

d. Dizzy time

Answer : C

Q ti 7


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Question 7

Most diagnostic magnets have a strength of:a. 1T

b. 1.5T

c. 5T

d. 5.5T

Answer : B

Q ti 8


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Question 8

The sum of the magnitudes and directions of the magnetic spins is known asthe :

a. Net magnetization vector

b. Additional variable

c. Geometric factor

d. I give up factor

Answer : A

Q ti 9


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Question 9

All of the following are types of MRI units excepta. Open

b. Mobile

c. Fonar

d. Bloch

Answer : D

Q ti 10


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Question 10

Which magnets are used in MRI:1. Permanent 2. Electromagnetic 3. Rare Earth

a. 1

b. 2

c. 3

d. 1 & 2

e. 1, 2 & 3

Answer : D

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Magnetic Resonance Eric