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Presentation Transcript

Outline
Outline:

MRI technique enable the student to understand different MRI protocols

Brain

Spine

Upper &lower extremity

Chest & breast

Abdomen &pelvis

Special techniques:

  • MRA

  • MRCP

  • MRU

  • MRSI

  • FMRI


Objectives
Objectives:

  • Explain the MRI scanner types

  • MRI safety &consideration

  • Describe the affects of MRI parameters to image quality.

  • Describe patient preparation for MRI scan procedures.

  • Describe the type of MRI contrast media.

  • Describe the patient position &protocols for each part of the body.

  • At the end of this course the student should be able to understand and explain the following:

  • Describe the image display &manipulation artifacts.


Application
APPLICATION

MRA = Magnetic resonance Angiography , amazed technique which display or show the details of blood vessels ( lumens ), such as circle of wills in brain or any other blood vessel in the body.


Renal mra
RENAL MRA


Angiographic techniques
ANGIOGRAPHIC TECHNIQUES

  • Circle of Willis angiograms without any contrast


Brain
BRAIN

  • Indications:

  • Hemorrhage (stages of)

  • De myelinating disorders (M.S.)

  • Infectious processes (encephalitis, meningitis)

  • Abscesses

  • Neo plasms

  • Trauma

  • Vascular disorders .


Brain cont d
BRAIN (cont’d)

  • Metastasis

  • Internal auditory canal pathology

  • Pituitary pathology

  • Hydrocephalus

  • Cranial nerve pathology

  • Congenital anomalies (for anatomical review)

  • Epilepsy .


Spine
SPINE

  • Radiculopathy

  • Tumors

  • Trauma/contusion

  • Syringomyelia

  • Metastasis

  • Vascular disorders

  • Cord edema

  • M.S. plaques


Spine cont d
SPINE (cont’d)

  • Caudaequina syndrome

  • Tethered cord

  • Arachnoiditis

  • Marrow-replacing processes

  • Degenerative disc disease

  • Discitis

  • Congenital anomalies



Musculoskeltal shoulder knee ankle wrist elbow tmj
MUSCULOSKELTAL(shoulder, knee, ankle, wrist, elbow, TMJ)

  • Meniscal pathology

  • Ligament/tendon injury

  • Muscle/nerve impingement

  • Avascular necrosis

  • Labral tears (shoulder, hip)

  • Chondromalacia

  • Inflammation (osteomyelitis)

  • Primary bone tumours

  • Soft tissue tumours


Abdominal imaging
ABDOMINAL IMAGING

  • Breath-hold scans to overcome motion artifact problem

  • MRCP’s - images of the biliary and pancreatic ductal systems performed non-invasively (no contrast or endoscope!) within seconds

  • Fetal imaging very diagnostic


Abdominal pelvic
ABDOMINAL/PELVIC

  • Liver pathology

  • Kidney pathology

  • Renal artery MRA

  • Fetal abnormalities


Mr spectroscopy mrs
MR Spectroscopy (MRS)

  • Information obtained is in the form of a spectrum which provides the biochemical information contained within a selected voxel of tissue

  • Used to detect the absence or presence of a certain compound

  • Assists in differential diagnosis when standard clinical radiological tests fail or are too invasive


Mrs current applications
MRS Current Applications

  • Multiple Sclerosis

  • Huntington’s

  • Parkinson’s

  • Alzheimer’s

  • Epilepsy

  • other dementias

  • metabolic disorders

  • Stroke

  • ischemic injury

  • Tumours and intracranial lesions

  • Prostate cancer

  • Encephalopathies


Functional mri f mri
Functional MRI (F MRI)

  • Detects changes in blood flow or metabolism associated with specific motor or sensory functions or stimuli

  • Performed by scanning specific areas of the brain/spine while: a) the subject performs a certain motor task or b) exposing the subject to certain external/internal stimuli.



Magnet coil
Magnet coil

A magnet is a material or object that produces a magnetic field. For details about specific types of magnets see:

→ Permanent magnet

→ Resistive magnet

→ Superconductive magnet

An electromagnet whose strong magnetic field (typically at least 0.5 T) is generated using superconductive coils. The conductive wires of the coils are made of a cryogenically cooled Niobium Titanium alloy. Liquid helium is used as the cryogen or liquid nitrogen for pre-cooling.

The most important component of the MRI scanner is the magnet.


A permanent magnet is sometimes referred to as a vertical magnet.

These magnets are constructed of two magnets (one at each pole).


Permanent magnet
Permanent Magnet magnet.

The patient lies on a scanning table between these two plates.

Advantages of these systems are:

1) Relatively low cost, 2) No electricity or cryogenic liquids are needed to maintain the magnetic field, 3) Their more open design may help alleviate some patient anxiety.

Disadvantages are :

1) Low field strength typically 0.02 T .

2) It has a high weight = HEAVY WEIGHT

3) Poor diagnosis


Resistive magnet
Resistive Magnet magnet.

Resistive magnets are constructed from a coil of wire. The more turns to

the coil, and the more current in the coil, the higher the magnetic field.

These types of magnets are most often designed to produce a horizontal

field due to their solenoid design.


Resistive cont
Resistive Cont. magnet.

The main advantages of these types of magnets are:

1) No liquid cryogen, 2) The ability to “turn off” the magnetic field, 3)

Relatively small fringe field.

The main Disadvantages are :

1) Low magnetic field strength .

2) Always producing heat , and this thing is huge problem for imaging .

3) Not enough for imaging.


Superconducting
Superconducting magnet.

Superconducting magnets are the most common. They are made from

coils of wire (as are resistive magnets) and thus produce a horizontal

field. They use liquid helium to keep the magnet wire at 4 degrees Kelvin

where there is no resistance. The current flows through the wire without

having to be connected to an external power source.


Superconducting magnet
SUPERCONDUCTING MAGNET magnet.

  • No resistance to flow of electricity

  • Coils of wire surrounded by cryogen bath (Helium) at -273 C

  • No external source of energy required

  • Magnetic field present ALL THE TIME!!!


Superconducting1

Z magnet.

Y

X

Superconducting

The main advantages are :

The ability of superconducting magnets is to attain field strengths of up

to 3 Tesla for clinical imagers, and up to 10 Tesla or more, & good resolution & most common used.

Disadvantages are :

1- take more time to produce the image .

2- always making noise with scanning .

3-Not suitable for some care patients.

4- Expensive.



Shim coils
Shim coils magnet.

Coils that create weak additional magnetic fields in various spatial directions. Used to correct in homogeneity in the main magnetic field.


Gradient coils
Gradient coils magnet.

Coils used to generate magnetic gradient fields. Gradient coils are operated in pairs in the magnet, at the same current, however, of opposite polarities.

One of the coils increases the static magnetic field by a certain amount, the opposite coil reduces it by the same amount. This changes the magnetic field overall. The change is the linear gradient. According to the coordinate axes, there are x, y, and z gradient coils.


Gradient coils polarization magnet.

Gradient coils


Rf coils
RF coils magnet.

RF coils are the "antenna" of the MRI system that broadcasts the RF signal to the patient and/or receives the return signal. RF coils can be receive-only, in which case the body coil is used as a transmitter; or transmit and receive (transceiver).


  • T1 WEIGHTING magnet.

  • A short TR and short TE will result in a T1 weighted image

  • Excellent for demonstrating anatomy

  • T2 WEIGHTING

  • A long TR and long TE will result in a T2 weighted image

  • Excellent for demonstrating pathology




  • T1 Characteristics magnet.

    • Dark

    • •CSF

    • •Increased Water – edema, tumor, infarct, inflammation, infection, hemorrhage (hyper acute or chronic)

    • •Low proton density, calcification

    • •Flow Void = less saturation

      • Bright

      • Fat

      • Sub acute hemorrhage

      • Melanin = melanoma

      • Protein-rich Fluid

      • Slowly flowing blood

      • Gadolinium

      • Laminar necrosis of an infarct

  • White matter brighter than Gray


  • T2 Characteristics magnet.

    • Dark

    • •Low Proton Density, calcification, fibrous tissue

    • • Paramagnetic substances – deoxy hemoglobin, methemoglobin (intracellular), iron, hemosiderin, melanin

      • •Protein-rich fluid

      • •Flow Void

    • Bright

    • •Increased Water – edema, tumor, infarct, inflammation, infection, subdural collection

    • •Methemoglobin (extracellular) in subacute hemorrhage

    • Gray matter brighter than white


Mri technique rf pulse sequences parameters and artifacts
MRI TECHNIQUE magnet.RF pulse sequences , parameters and Artifacts…


Rf pulse sequences parameters
RF pulse sequences ,parameters magnet.

  • To create an MR image we need to select a pulse sequence and the scan parameters. The pulse sequence controls the transmission and timing of the RF and gradient pulses which then create a measurable signal from a selected slice.

  • Every MRI scan begins with an operator-selected scan protocol which may include several different pulse sequences. The operator enters the patient parameters, including identification, location and orientation.


Imaging pulse sequences
Imaging pulse Sequences magnet.

  • How do we obtain an image with the largest possible contrast between different tissue types?

    Different tissue types have different transverse magnetizations. Where the signal is strong, the image shows bright pixels; weaker signals result in darker pixels


What determines the signal strength? magnet.

Clearly to a large degree from the proton density in the respective voxel: the greater the number of protons contributing to the magnetization, the stronger the signal.

But even more important for medical diagnostics is the effect of the two relaxation constants T1 and T2 on the image contrast.


Imaging pulse sequences1
Imaging Pulse Sequences magnet.

  • Spin Echo

  • Fast Spin Echo

  • Inversion Recovery

  • Gradient Echo

    The other additional sequences are :

    Saturation , EPI , diffusion and perfusion.. ..


Review
Review magnet.

  • T1 contrast (TR short, TE short)

  • T2 contrast (TR long, TE long)

  • Proton density contrast (TR long, TE short)

  • Tissue with longer T1 appears darker in the T1-weighted image, tissue with longer T2 appears brighter.


1 spin echo
1- Spin Echo magnet.

  • The spin echo sequence: A 180 degree pulse is applied at time τ after a 90 degree RF pulse, a spin echo is generated after echo time TE=2τ.

  • This pulse sequence, 90 degrees180 degrees has to be repeated until all phase-encoding steps of the scan matrix have been acquired

  • TE and TR are the most important parameters for controlling the contrast of a spin echo sequence


Spin echo
Spin Echo magnet.


Advantages
Advantages : magnet.

  • Provides overall good-quality image.

  • It is possible to obtain T1, T2, and PD contrast.

  • It has a high clinical value.

  • It is not very sensitive to susceptibility artifacts.Disadvantages:

  • MR acquisition time is quite long.

  • It deposits higher RF power compared to gradient echo sequences.


2 fast spin echo fse
2- Fast Spin Echo[FSE] magnet.

FSE used to make SE much faster , they do have a number of additional 180° RF pulses. Even though those RF pulses can be used to create separate images with different TE times (such as PD and T2) in one excitation

  • FSE used to cover k-space with multiple phase encoding lines in a single excitation.


Fast spin echo fse continued
Fast Spin Echo[FSE] continued magnet.

  • The number of 180° RF pulses in this case does have of significant value for image contrast and it is called as echo train length (ETL) or turbo factor.

  • T1, PD, and T2 weighted images much faster than conventional SE sequence, this is achieved via filling up k-space by a factor proportional to the chosen ETL number.

  • scan parameters: TR-TE- echo train length



Advantages of the fse
Advantages: of the FSE magnet.

  • Provides optimal SNR and CNR.

  • T1, T2, and PD contrast much faster than conventional SE sequences.

  • Reduction in scan time makes it more practical to acquire high resolution images.

  • image contrast similar to SE.


[FSE] Disadvantages: magnet.

  • Images look more blurry than SE images.

  • T2 weighted FSE images show bright fat signal rather than darker fat signal.

  • new hardware required

  • ear protection may be necessary.

  • motion sensitive


Fast magnet.Spin Echoblurring

SE TE 20

FSE TE 20


3 ir inversion recovery pulse sequences
3- (IR) Inversion recovery pulse sequences magnet.

  • Inversion recovery pulse sequences are used to give heavy T1-weighting.

  • In addition, the STIR (short TI inversion recovery) sequence can be used for fat suppression, where a relatively short inversion time is used to null the fat signal while maintaining water and soft tissue signal.

  • inversion recovery sequence is a 180 degree RF pulse that inverts the magnetization followed by a 90 degree RF pulse that brings the residual longitudinal magnetization into the x-y or transverse plane.


Inversion Recovery magnet.

TR







TI

TE

inversion recovery

conventional SE or FSE sequence


Inversion time ti
inversion time TI magnet.

  • (TI) The time between the initial 180 degree pulse and the 90 degree pulse is the inversion time (TI

  • IR has 2 main techniques:

    1-STIR [short TI inversion recovery]

    2-FLAIR [fluid attenuation inversion recovery]


A stir
A-STIR magnet.

  • STIR stands for Short T1 Inversion Recovery and one of the widely used IR sequences. The sequence design is almost identical to an SE or FSE sequence. However, before the 90° excitation RF pulse, we apply an 180° inversion pulse to invert the MR signal.

    STIR advantages

    • works better than fat saturation over a large FOV

    • better at lower field strengths

  • high visibility for fluid

    • long T1 bright on STIR

    • long T2 bright on STIR, given long enough TE

    • The disadvantages are

      It usually takes longer to acquire .


B- magnet.FLAIR[fluid attenuation inversion recovery]

Are also part of IR sequence family with widespread use, The main purpose of T2 FLAIR sequences is to null or suppress the cerebrospinal fluid (CSF) .

Suppressing CSF enables us a much better visualization of adjacent white matter (WM) tissues with possible lesions. Therefore, it is one of very essential sequences of any routine brain imaging.


T1 SCAN magnet.

Anatomic structures

Fat = bright

Water = hypo intense

T2 SCAN

Water weighted sequence

Water = bright

Fat = relatively hypo intense

Good for identifying pathology


Mri findings of acute ischemic stroke
MRI FINDINGS OF magnet.ACUTE ISCHEMIC STROKE

T1 (hypo intense)

T2 (hyper intense)

FLAIR (hyper intense)

FLAIR SCANS ARE T2 SCANS WITH THE FREE WATER SIGNAL NULLED.


SSFSE (Single Shot Fast Spin Echo) or HASTE Sequence(half Fourier acquired single-shot turbo spin-echo sequence)

  • SSFSE or HASTE sequence is one of the ultrafast sequences and it enables us to acquire whole MR data (k-space) in a single RF excitation or single shot.

  • the term single shot means a series of 180° RF pulses are applied following the initial 90° pulse and we do not repeat the 90° pulse excitation pulse again. This

    is simply due to the fact that we acquire the whole k-space needed to form an MR image in a long ETL in a very fast way.



4 gradient echo pulse sequences gre
4-Gradient Echo Pulse Sequences (GRE) longer TE times such as MRCP, urography, myelograpy.

  • smaller than < 90°, is applied in GRE sequences and usually shorter TRs are used as well. Smaller q flip angle means that we end up with less signal in the transverse plane (a bad thing), but at the same time ,the MR magnetization or signal can recover much faster (a good thing) since it is not fully tilted to transverse plane.

  • GRE sequence create faster called as fast and ultrafast GRE sequences. These types of fast GRE sequences are used very frequently where we need the speed such as abdomen, MR angiography applications and musculoskeletal.


Fast gre
fast GRE longer TE times such as MRCP, urography, myelograpy.

GRE sequences can be divided However, into:-

  • (SPGR) T1 weighted spoiled gradient echo sequences or MPGR (Multiplanar Gradient-Recalled).

  • (U FGES)Ultrafast gradient echo sequences.

  • (SSFP) Balanced gradient echo sequences

  • GRASS (Gradient Recalled Acquisition in the Steady State)

  • MPGR (Multiplanar Gradient-Recalled)

  • 3D GRASS.

    7) Echo Planar Imaging (EPI) Sequences


7 echo planar imaging epi sequences
7 longer TE times such as MRCP, urography, myelograpy.) Echo Planar Imaging (EPI) Sequences

Advantages:

  • It is the base sequence for, diffusion weighted imaging (DWI) sequence, perfusion weighted imaging (PWI).

    Disadvantages:

  • require relatively new MR hardware. Therefore,

  • it cannot be used efficiently at older MR scanners and some open MR scanners


Mr spectroscopy pulse sequences
MR Spectroscopy Pulse Sequences longer TE times such as MRCP, urography, myelograpy.

  • known as nuclear magnetic resonance (NMR) spectroscopy, Is a noninvasive technique, which has been used to study metabolic changes in brain tumors, multiple sclerosis, Alzheimer, stroke, and other diseases affecting the brain.

  • MR spectroscopy shows a spectrum graph, which is proportional to the concentration of metabolites, while MR images show a signal proportional to water content and relaxation properties of the tissues and lesions in the brain.


Mr parameters
MR Parameters longer TE times such as MRCP, urography, myelograpy.

Selection of right MR imaging parameters almost always results in better image quality and prevents the typical imaging artifacts seen on daily scanning. Therefore, it is very important to understand the working mechanism of those parameters for the best decision making.In general, we can divide MR parameters into three main groups:

  • MR imaging parameters

  • MR pulse sequence parameters

  • MR imaging options


1 mr imaging parameters
[1] MR Imaging Parameters longer TE times such as MRCP, urography, myelograpy.

1-Field of View (FOV) (24x24) (24x20)cm

  • The FOV is the total area that the matrix of phase and frequency encoding cover. Dividing the FOV by the matrix size gives you the voxel size hence, increasing the FOV in either direction increases the size of the voxels and decreases the resolution.

  • Decreasing the FOV improves the resolution.

  • SNR is proportional to the FOV.


Effect of FOV on spatial resolution and SNR. Note improved visualization of the lens in the 12cm image (B) when compared to the 24cm FOV image (A), achieved at the expense of SNR.


2- visualization of the lens in the 12cm image (B) when compared to the 24cm FOV image (A), achieved at the expense of SNR.Matrix size:(256x256) (512x512)

the higher imaging matrix results in noisier image, it has better resolution.


3- Spatial Resolution visualization of the lens in the 12cm image (B) when compared to the 24cm FOV image (A), achieved at the expense of SNR.

Spatial resolution determines how "sharp" the image looks. Spatial resolution is defined by the size of the imaging voxels.

Since voxels are three dimensional rectangular solids, the resolution is frequently different in the three different directions.

The size of the voxel and therefore the resolution depends on matrix size, the field-of-view (FOV), and the slice thickness.

Resolution = FOV/matrix in mm.


4-Slice Thickness ( TH ): visualization of the lens in the 12cm image (B) when compared to the 24cm FOV image (A), achieved at the expense of SNR.

Slice Thickness ( TH )

is defined in mm and determines the depth of your voxel on slice encoding direction. the thicker the slice is, the higher the SNR becomes. However, the thicker the slice, the lower the resolution becomes.


Sample images acquired with slice thickness of 3 mm ( a ) and 15 mm ( b ) are shown on the same volunteer, so the thicker the slice, the lower the resolution becomes.


5- Slice Spacing or Gap : and 15 mm ( b ) are shown on the same volunteer

can be defined in mm or in % of the [TH] depending on MR manufacturers.

  • This spacing is needed to reduce the crosstalk artifacts caused by the excitation of neighboring slices due to imperfect slice selective RF pulse.


6- and 15 mm ( b ) are shown on the same volunteerNumber of acquisition ( NSA , number of excitations[ NEX ]):

  • NEX is an indication of how many signal averages taken during an MR acquisition. This is usually achieved by repeating the acquisition in frequency direction and taking an average of the sampled signal.

  • SNR increase is directly proportional to the square root of NEX increase factor.

  • Scan time is proportional to NEX



7- (BW) Bandwidth [ b ) are shown on the same volunteer.Hertz]

is a measure of frequency range, the range between the highest and lowest frequency allowed in the signal. For analog signals, which can be mathematically viewed as a function of time, band

higher bandwidth gives :-

1- a much sharper image, reduces ringing artifacts

2- reduce the total scan time .

Total BW= Frequency matrix / Ts (in seconds).

8- Scan time


2 mr pulse sequence parameters
2- MR Pulse Sequence Parameters b ) are shown on the same volunteer.

1- TR 2-TE 3-T1 4-PD

5- T2

6-T2*:It is characterized by loss of transverse magnetization at a rate greater than T2,caused by magnetic field in homogeneity occurs in all magnets.

7- Inversion Time [TI]

8- Echo Train Length ( ETL ) or Turbo Factor :

defined as the number of refocusing 180° RF pulses after the initial excitation RF pulse.

9-Flip Angle ( FA ):


3-MR Imaging Options: b ) are shown on the same volunteer.

In MR imaging, there are several imaging options used to enhance or alter the image contrast and to reduce the MR artifacts.Options such as fat saturation(FS), cardiac gating(CG), and flow compensation (FC) can be combined with certain pulse sequences depending on how they were designed and set up.


Mri artifacts
MRI Artifacts b ) are shown on the same volunteer.


Introduction
Introduction b ) are shown on the same volunteer.

  • There are numerous kinds of artifacts that can occur in MRI.

  • Some effect the quality of the MRI exam.

  • Others may be confused with pathology.

    The definition of artifacts is : Abnormal appearance in the MRI images which may obscure some small lesions.


Chemical shift artifacts
Chemical Shift Artifacts b ) are shown on the same volunteer.

A chemical shift artifact is caused by the difference in Frequency of fat and water.

The artifact manifests itself as a miss registration between the fat and water pixels in an image .

The effect being that fat and water spins in the same voxel are encoded as being located in different voxels.


Chemical shift artifact
Chemical shift Artifact b ) are shown on the same volunteer.

Chemical shift artifact can be reduced by performing imaging at low magnetic field strength, by increasing receiver bandwidth, or by decreasing voxel size.

The artifacts tend to be more prominent on T2-weighted than on T1-weighted images.

Fat suppression methods often eliminate visible artifacts


CSA b ) are shown on the same volunteer.


Aliasing or wrap around
Aliasing or "Wrap-around " b ) are shown on the same volunteer.

  • Occurs when the field of view (FOV) is smaller than the body part being imaged causing the region beyond to project on the other side of the image.

  • Caused by under sampling in the phase or (rarely) frequency direction.


Aliasing or wrap around1
Aliasing or "Wrap-around " b ) are shown on the same volunteer.


Aliasing
Aliasing b ) are shown on the same volunteer.


Aliasing or wrap around2
Aliasing or "Wrap-around " b ) are shown on the same volunteer.

  • Correction Methods :

  • Increase the FOV (decreases resolution).

  • Oversampling the data in the frequency direction (standard) and increasing phase steps in the phase-encoded direction – phase compensation (time or SNR penalty).

  • Use surface coil so no signal detected outside of FOV.


Black line artifact
Black Line Artifact b ) are shown on the same volunteer.

  • An artificially created black line located at fat-water interfaces such as muscle-fat interfaces.

  • Occurs at TE when the fat and water spins located in the same pixel are out of phase, cancelling each other’s signal. Particularly noticeable on GE sequences. Both freq and phase direction.


Black line artifact1
Black Line Artifact b ) are shown on the same volunteer.


Black line artifact2
Black Line Artifact b ) are shown on the same volunteer.

  • Use in-phase TE’s

  • Fat suppression

  • Increase bandwidth or matrix size.


Zipper artifacts
Zipper Artifacts b ) are shown on the same volunteer.

  • Most are related to hardware or software problems beyond the radiologist control. May occur in either frequency or phase direction.

  • Zipper artifacts from RF entering room are oriented perpendicular to the frequency direction.


Zipper artifacts1
Zipper Artifacts b ) are shown on the same volunteer.


Motion artifacts
Motion Artifacts b ) are shown on the same volunteer.

  • Bright noise or repeating densities usually oriented in the phase direction.

  • Extend across the entire FOV.

  • Examples: Arterial pulsations, CSF pulsations, swallowing, breathing, peristalsis, and physical movement.


Motion artifacts1
Motion Artifacts b ) are shown on the same volunteer.

  • Mitigation :

  • Arterial and CSF pulsation artifacts can be reduced with flow compensation and cardiac gaiting.

  • Surface coil localization can reduce artifacts generated at a distance from the area of interest.


Motion artifacts2
Motion Artifacts b ) are shown on the same volunteer.


Slice overlap cross slice artifacts
Slice-overlap (cross-slice) Artifacts b ) are shown on the same volunteer.

  • Loss of signal seen in an image from a multi-angle, multi-slice acquisition.

    Example: Two groups of non-parallel slices in the same sequence, e.g., L4-5 and L5-S1.


Slice overlap cross slice artifacts1
Slice-overlap (cross-slice) Artifacts b ) are shown on the same volunteer.


Slice overlap artifacts
Slice-overlap Artifacts b ) are shown on the same volunteer.


Slice overlap artifacts1
Slice-overlap Artifacts b ) are shown on the same volunteer.

  • Correction:

  • Avoid steep change in angle between slice groups.

  • Use separate acquisitions.

  • Use small flip angle, i.e. GE sequence


Cross talk artifact
Cross-talk Artifact b ) are shown on the same volunteer.

  • May be reduced by using gap, interleaving slices and optimized (but longer) RF pulses.


Entry slice inflow artifact
Entry slice (Inflow) artifact b ) are shown on the same volunteer.

  • Unsaturated spins in blood or CSF entering the initial slices results in greater signal than reduces on subsequent slices.

  • May be confused with thrombus.

  • Can use spatial saturation to reduce.

  • Mechanism for TOF angiography.


Entry slice inflow artifact1
Entry slice (Inflow) artifact b ) are shown on the same volunteer.


Susceptibility artifacts
Susceptibility Artifacts b ) are shown on the same volunteer.

  • Variations in the magnetic field strength that occurs near the interfaces of substance of different magnetic susceptibility such as ferromagnetic foreign bodies.

  • Causes dephasing of spins and frequency shifts of the surrounding tissue.


Susceptibility artifacts1
Susceptibility Artifacts b ) are shown on the same volunteer.

  • Worst with long echo times and with gradient echo sequences.

  • Worst at higher magnetic field strength.

  • Less with fast/turbo spin echo sequences.


Susceptibility artifacts2
Susceptibility Artifacts b ) are shown on the same volunteer.


MRI SAFETY & APPLICATIONS b ) are shown on the same volunteer.


Advantages1
ADVANTAGES b ) are shown on the same volunteer.

  • Superior soft tissue contrast resolution - excellent pathological discrimination

  • No ionizing radiation

  • Direct multi-planar imaging (transverse, coronal, sagittal, any oblique)

  • Non-invasive - vascular studies can be performed without contrast


Disadvantages of mri
DISADVANTAGES OF MRI b ) are shown on the same volunteer.

  • Expensive

  • Long scan times

  • Audible noise.

  • Isolation of patient (claustrophobia, monitoring of ill patients)

  • Exclusion of patients with pacemakers and certain implants


The strong magnetic field of the magnet can turn the following into dangerous projectiles
THE STRONG MAGNETIC FIELD OF THE MAGNET CAN TURN THE FOLLOWING INTO DANGEROUS PROJECTILES:

  • wheelchairs

  • oxygen tanks

  • I.V. poles

  • keys

  • coins

  • scissors

  • trauma boards

  • sandbags

  • safety pins


The changing magnetic fields can do damage to
THE CHANGING MAGNETIC FIELDS CAN DO DAMAGE TO: FOLLOWING INTO DANGEROUS PROJECTILES:

Monitoring equipment

Infusion pumps

Credit cards

Cellular telephones

Any electronic device


Mri bio effects and safety
MRI Bio effects and Safety FOLLOWING INTO DANGEROUS PROJECTILES:

  • Bio effect of Static, Gradient Magnetic and Radiofrequency Electromagnetic Fields

  • Acoustic Noise.

  • Electrically, Magnetically or Mechanically Activated Implants and Devices,

  • Screening Patients with Metallic Foreign Bodies

  • Performing Magnetic Resonance Imaging During Pregnancy

  • Magnetic Resonance Imaging and Claustrophobia, Anxiety and panic Disorders

  • Monitoring Physiologic Parameters During Magnetic Resonance Imaging

  • Safety Consideration of Gadolinium Contrast Agents


Mri safety
MRI Safety FOLLOWING INTO DANGEROUS PROJECTILES:


Metallic implants devices and foreign bodies
Metallic Implants, Devices and Foreign Bodies FOLLOWING INTO DANGEROUS PROJECTILES:

  • Aneurysm and Hemostatic Clips

  • Carrotid Artery Vascular Clamps

  • Dental Devices and Materials

  • Heart Valves

  • Intravascular Coils, Filters and Stents Ocular Implants

  • OrthopedicImplants, Materials and Devices

  • Bullets, Shrapnel, and Other Foreign Bodies

  • Vascular Access Ports

  • Screening patients with Foreign Bodies


Monitoring physiologic parameters during mri
Monitoring Physiologic Parameters During MRI FOLLOWING INTO DANGEROUS PROJECTILES:

  • Blood pressure

  • Respiratory Rate, Oxygenation and Gas Exchange

  • Cutaneous Blood Flow

  • Heart Rate


Safety in contrast agents
Safety in Contrast Agents FOLLOWING INTO DANGEROUS PROJECTILES:

  • Adverse Events

  • Specific Adverse Events

  • Contrast Agents and Renal Failure

  • Chronic and Repeated Use of Contrast Agents

  • Use Contrast Agents During Pregnancy and Lactation


Gadolinium
GADOLINIUM FOLLOWING INTO DANGEROUS PROJECTILES:

USEFUL FOR DETECTION OF:

  • Tumours pre- and post-operative

  • Infection

  • Inflammation

  • Post-traumatic lesions

  • Post-operative changes

  • MRA’s

  • AND ALSO INDICATIONS OF ………


Brain imaging
Brain Imaging FOLLOWING INTO DANGEROUS PROJECTILES:




Suggested protocols
: FOLLOWING INTO DANGEROUS PROJECTILES:Suggested protocols

  • Axial SE T1

  • COR SE T1


Mra mrv
MRA & MRV FOLLOWING INTO DANGEROUS PROJECTILES:


Spine mri

Spine MRI FOLLOWING INTO DANGEROUS PROJECTILES:

Cervical dorsal lumbar


Thank you

Thank you FOLLOWING INTO DANGEROUS PROJECTILES:


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