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MAGNETIC RESONANCE IMAGING PART 222-Nov-08

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1-Hour of continuing education forre-licensure

MAGNETICRESONANCEIMAGING:Part 2

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Course Instructions

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Course Instructions

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Course objectives

The multi-planar images of MRI

MRI Shades of gray

T1 and T2 Images

MRI Artifacts

Special MRI Studies

Fat Suppression Studies

Contrast Enhanced Studies

MR Arthrography

Functional MRI

By completing this course, you will learn:

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MULTIPLANAR IMAGES OF MRI

PLANES OFTHE BODY

SHADES OF GRAYSHADES OF GRAY

BRIGHT WHITE = HIGH SIGNAL INTENSITY

DARK GRAY = LOW SIGNAL INTENSITY

MRI SEQUENCE PROTOCOLS

Magnetic Gradients

RF Pulses

Pulse interval

Pulse strength

Pulse duration

COMPARING INTENSITIES

Isointense

If the signal intensities are the same

Hypointense

If the signal intensity is darker

Hyperintense

If the signal intensity is brighter.

WHAT DO WE KNOW SO FAR?

The patient is placed in a strong magnetic field

Apply a Radio Frequency (RF) Pulse to the hydrogenprotons

The RF Pulse is turned off and the protons are allowed toreturn to their equilibrium state

The RF signal emitted by the proton is detected, collectedand analyzed

By varying the sequence of the RF Pulses applied,different types of images are created

On the scan:

Dark = Low Signal Intensity

Bright = High Signal Intensity

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T1 WEIGHTED IMAGE T2 WEIGHTED IMAGE

HIGH SIGNAL FOR FATLOW SIGNAL FOR WATER

HIGH SIGNAL FOR WATERLOW SIGNAL FOR FAT

T1 WEIGHTED IMAGE T2 WEIGHTED IMAGE

HIGH SIGNAL FOR FATLOW SIGNAL FOR WATER

HIGH SIGNAL FOR WATERLOW SIGNAL FOR FAT

T2 Weighted Image

The discs should appearas white because, whenthey are healthy, theyhave a high water content

The L3 and L4 discs arewhite, indicating that theyare healthy

The L5 disc however isdark, indicating that it isundergoing adegenerative process

T2 Weighted Image

The thecal sac (red stars) is the'super white' structure that fillsthe central spinal canal justbehind the posterior vertebralbodies. It is white because ithas a high water content

The ligamentum Flavum(green star) courses betweeneach of the vertebrae.

MRI IMAGE ARTIFACTS

Motion Artifacts

Slice Artifacts

Marrow Artifacts

MOTION ARTIFACTS

Compared to plain film and CT, MRI isa long process making it susceptible tomotion artifacts

Motion can arise from a variety ofsources

Body movement

Patient comfort

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MOTION ARTIFACTSLICE ARTIFACTS

SPEICAL MRI STUDIES

Fat Saturation Studies

Contrast Enhanced Studies

MR Arthrography Studies

Functional MRI

FAT SATURATION STUDIES

AKA: Fat Suppression Studies

There are certain clinical situations in which it isadvantageous to suppress the high signal intensity of fat

Certain pathologies such as recent compression fracturesof the spine produce edema

Edema has a high water content

By suppressing the fat signal small areas of edemabecome more evident because there is no competitionfrom the high signal intensity of fat.

MR with fat suppression is the definitive imaging modalityto differentiate recent versus old compression fractures

L3 COMPRESSIONFRACTURE

T1 WEIGHTEDIMAGE

T2 WEIGHTEDIMAGE

T2 WEIGHTEDIMAGE WITH FATSUPPRESSION

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CONTRAST ENHANCED MRI

The standard contrast agent is Gadolinium

It is also know as:

Gd-Dtpa

Gad

Magnevist is the trade name

Gadolinium enhancement is used on certainstudies to make vascular structures brighter

INDICATIONS FOR GAD

Post-operative spines

Disc material does not enhance whereaspost-operative scar tissue does

Metastasis to the spinal cord

Multiple Sclerosis plaques

MR Arthrography

MR Angiography

POST-OPERATIVE SPINES

The T1 and T2 MRI appearance of discherniation in the postsurgical and nonsurgicalback looks the same.

Surgical cases often cause scar tissue toaccumulate within the epidural spaceadjacent to nerve roots often mimicking discherniations.

Gadolinium will help make this differentiationand therefore plays a key role in selecting theappropriate management for the postsurgicalback pain patient.

Gadolinium-Enhanced MRI This type of MRI is ordered when ever you are

suspecting the build up of scar tissue as thecause of the patient’s symptoms

With a Gadolinium enhanced MRI the patient willfirst have the MRI without the Gadolinium, thenthe patient will receive an injection of Gadoliniumand the MRI will be repeated

The two type of images will then be compared toone another

SAGITTAL AXIAL

PREGd-DTPA

PREGd-DTPA

POSTGd-DTPA

POSTGd-DTPA

CASE STUDY40 Year old man who underwent laminectomy and discectomy 1year prior with recurrent back pain

The MRI images demonstrate how gadolinium will "light-up"a healed anular tear.

Note the L4 disc shows no sign of posterior disc tearing(black arrow);

However, after the administration of gadolinium during theMRI, the same T1 image demonstrates the scar of amassive annular tear (red arrow)

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8 year old male with 4 weeks of right hip pain and limping

T1 IMAGE T2 IMAGE POST GADT1 IMAGE

Be Careful When Ordering GadoliniumEnhanced MRI’s Gadolinium side effects could result in the

development of a rare and potentially fatal disorderfor those with moderate to end-stage renal disease.

For those without a fully functioning kidney, sideeffects of gadolinium contrast agents could lead tothe development of Nephrogenic SystemicFibrosis (NSF)

The rare progressive disorder is associated withfibrosis, or scarring, of the skin and internalorgans. This results in thick, coarse and hard skinwhich severely restricts movement of the joints. Insome cases, the gadolinium skin disorder can lead todeath

MR ARTHROGRAPHY

Specialized MRI study to provide a more detailed imagingof joints than routine MRI

Two part procedure

Distension of the joint with a solution containing dilutegadolinium is extremely useful in detecting certain typesof pathology such as labral tears in the shoulder and hip

Also useful in evaluating knee pain in a patient with aprior history of surgery as it can differentiate betweenmeniscal tear (where the contrast extends into the tearand scar within a healed meniscal tear where the contrastis contained.

FUNCTIONAL MRI

WHAT IS fMRI

Functional MRI is based on the increase in blood flow tothe local vasculature that accompanies neural activity inthe brain

This results in a corresponding local reduction indeoxyhemoglobin because the increase in blood flowoccurs without an increase of similar magnitude in oxygenextraction

Since deoxyhemoglobin is paramagnetic, it alters the T2*weighted magnetic resonance image signal

Using an appropriate imaging sequence, human corticalfunctions can be observed without the use of exogenouscontrast enhancing agents

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ADVANTAGES OF Fmri OVER PET

The signal does not require injections ofradioactive isotopes

The total scan time required can bevery short, i.e., on the order of 1.5 to2.0 min per run and

The in-plane resolution of the functionalimage is generally better thanalternative methods.

FUTURE ROLE IN NEUROSURGICAL PLANNING FUTURE ROLE IN PAIN MANAGEMENT

DISTRACTION AND PAIN PERCEPTION

Distracting a patient decreases pain related brainactivity also seen on Functional MRI scans.

A distracted person process less pain. Whenfocusing on pain the person feels more pain.

Virtual Reality Changes Perception of Pain

Snow World

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Children between the ages of seven and 12 appear tobe naturally inclined to feel empathy for others in pain

Fibromyalgia Pain Isn't All In Patient'sHeads, New Brain Study Finds

Functional MRI study confirms scientifically whatfibromyalgia patients have been telling a skepticalmedical community for years: They're really in pain.

In fact, the study finds, people with fibromyalgia saythey feel severe pain, and have measurable painsignals in their brains, from a gentle finger squeezethat barely feels unpleasant to people without thedisease. The squeeze's force must be doubled tocause healthy people to feel the same level of pain -and their pain signals show up in different brainareas.

FUNCTIONAL MRI AND CHIROPRACTIC

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course

MRI-Part 2

1-Hour

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