MIDTERM Flashcards
acts as an antenna to produce/transmit and detect/receive radio waves that are referred to as the MRI signal
RF coil
RF coil acts as an antenna to produce/transmit and detect/receive radio waves that are referred to as WHAT
as the MRI signal
is enclosed in the gantry of the magnet.
typical RF coil
In order to optimize signal-to-noise ratio (SNR), WHAT should cover only the volume of interest. This is because the coil is sensitive to noise from the whole volume while the signal comes from the slice of interest.
the RF coil
In order to optimize signal-to-noise ratio (SNR), the RF coil should cover only WHAT . This is because the coil is sensitive to noise from the whole volume while the signal comes from the slice of interest.
the volume of interest
In order to optimize signal-to-noise ratio (SNR), the RF coil should cover only the volume of interest. This is because the coil is WHAT from the whole volume while the signal comes from the slice of interest.
sensitive to noise
In order to optimize signal-to-noise ratio (SNR), the RF coil should cover only the volume of interest. This is because the coil is sensitive to noise from WHAT
the whole volume while the signal comes from the slice of interest.
Most homogenous coils are of a WHAT design.
‘birdcage’
Can act as Transceivers (transmits and receives radio waves)
Radiofrequency/RF Coils
WHAT IS (transmits and receives radio waves)
Transceivers
is integrated into the scanner bore and cannot be seen by the patient.
Coil
Types of coils
Body coils
Volume/Bird Cage coils
Surface /Local coils
. Paired saddle coils
Shoulder coil
flex coil
spine coil
small body coil
breast coil
foot and ankle coil
prostate coil
Coil is integrated into the scanner bore and cannot be seen by the patient.
Body coils
WHAT TYPE OF COIL Completely surrounds the patient.
Body coils
WHAT TYPE OF COILS Acts as transceivers
Body coils AND Volume/Bird Cage coils
WHAT TYPE OF COIL, Head coil
Volume/Bird Cage coils
WHAT TYPE OF COIL, Being smaller in size provides better SNR.
Volume/Bird Cage coils
WHAT TYPE OF COIL, simple loop designs, either circular or rectangular, and have excellent SNR close to the coil but the sensitivity drops off rapidly with distance from the coil.
Surface /Local coils
WHAT TYPE OF COIL, Provides best RF homogeneity
Volume/Bird Cage coils
WHAT TYPE OF COIL, These are only used as receivers, the body coil acting as the transmitter.
Surface /Local coils
WHAT TYPE OF COIL, used for imaging anatomy near to the coil.
Surface /Local coils
WHAT TYPE OF COIL, The depth of the image of a surface coil is generally limited to about one radius.
Surface /Local coils
WHAT TYPE OF COIL, Commonly used for the knee
WHAT TYPE OF COIL, These coils provide better homogeneity of the RF in the area of interest and are used as volume coils, unlike surface coils.
WHAT TYPE OF COIL, also used for the x and y gradient coils
Paired saddle coils
WHAT TYPE OF COIL,
Paired saddle coils
WHAT TYPE OF COIL,
Paired saddle coils
Required to protect the environment from the effects of fringe fields which surround a magnet
Shielding
To maintain magnetic field homogeneity, shielding is necessary for the field to be protected from being distorted by the external environment.
Shielding
in Shielding, To maintain magnetic field homogeneity, shielding is necessary for the field to be protected from what
being distorted by the external environment.
MRI signal is relatively weak, small external RF interferences can WHAT
can degrade the image quality.
IT can degrade the image quality IF THE MRI SIGNAL IS WHAT
MRI signal is relatively weak, small external RF interferences
Imaging room should be shielded from the WHAT
the external sources of RF energy.
Also prevents the WHAT during the MR measurement from being disturbed by radio signals outside the MR room.
the RF signal generated
Also prevents the RF signal generated during the MR measurement from being WHAT
disturbed by radio signals outside the MR room.
Better homogeneity can be achieved by electrical and mechanical adjustments by a process known as WHAT
“shimming”
Type of shimming:
Active-coils
Passive-bore
An advance technique used to acquire images from moving body parts like chest, abdomen, cardiac and blood vessels studies reducing motion artifacts.
Gating
magnetic field outside the patient aperture.
Fringe magnetic field
IN Gating, An advance technique used to acquire images from moving body parts like chest, abdomen, cardiac and blood vessels studies reducing WHAT
motion artifacts.
WHAT GATING Acquisition is generally triggered by an electrocardiogram. This eliminate the blurring and artifact problem inherent
Cardiac gating
WHAT USES IN CARDIAC GATING to deliver RF pulse and to monitor the cardiac cycle to determine which signal it uses for reconstruction.
Uses programmed TR(time of repetition)
IN CARDIAC GATING, USES by the leads placed on patient’s chest to trigger each RF excitation pulse.
Uses the electrical signal detected
Used in cardiac mri/mra and mri thoracic aortogram
CARDIAC GATING
WHAT GATING, Suppress breathing motion Acquisition takes place only during the gate when respiratory is minimal
Respiratory gating
WHAT GATING, Effective in minimizing breathing motion
But increases imaging time and resolution
Also monitors the breathing of px
. Respiratory gating
WHAT GATING, Used in mri of the chest and abdomen, liver perfusion and dynamics, kidneys, spleen, adrenals and MRCP
Respiratory gating
WHATGATING, Short acquisition sequences but low resolution
Image acquisition every breath hold after exhalation.
Can also be used in mri of the chest and abdomen, liver perfusion and dynamics, kidneys, spleen, adrenals and MRCP
Breath holding
IN BREATH HOLDING PART F MRI PROCEDURE WHAT ARE THE DISEASE INCLUDED
MAGNETIC RESONANCE
CHOLANGIOPANCREATOGRAPHY
ENDOSCOPIC RETICULO
CHOLANGIOPANCREATOGRAPHY
WHAT GATING,Uses a photo sensor attached to either fingers or toes
Monitors the pulse of the px
Used in CSF flow studies, MRA of the head, neck, cardiac, chest, and peripherals and TRICKS.TIME RESOLVED IMAGING OF CONTRAST KINETICS
Peripheral gating/Pegating
WHAT GATING, Used in liver dynamics and cardiac imaging
Fluoro triggering
is a programmed set of changing magnetic gradients. Each sequence will have a number of parameters, and multiple sequences are grouped together into an MRI protocol.
PULSE SEQUENCES
defined by multiple parameters:
PULSE SEQUENCES
WHAT ARE THE Basic parameters:
TE
TR
Flip Angle
FoV and Matrix size
Inversion pulses (TI)
WHAT ARE THE Basic type of pulse sequences
Spin Echo
Inversion Recovery
Gradient Echo
WHAT IS Time required for the external magnetic field to go to two third of its original value
T1 Weighted Images-
WHAT WEIGHTED IMAGES, Gives information about the thermal conductivity of the surrounding tissue.
T1 Weighted Images-
WHAT WEIGHTED IMAGES, Water has low signal and appears dark and fat will appear bright.
T1 Weighted Images-
WHAT WEIGHTED IMAGES, Short TE/TR (10-15ms/300-600ms)
T1 Weighted Images-
WHAT WEIGHTED IMAGES, Gives information about the homogeneity of the surrounding atoms. Water is longer than other tissue.
T2 Weighted Images-
WHAT WEIGHTED IMAGES, USES FOR Anatomy
T1 Weighted Images-
WHAT WEIGHTED IMAGES, time required for the transverse magnetic field to decay to a third of its original value.
T2 Weighted Images-
WHAT WEIGHTED IMAGES,Water appears bright and fat will appear intermediate bright.
T2 Weighted Images-
WHAT WEIGHTED IMAGES, LongTE/TR (100-150ms/2000-6000ms)
T2 Weighted Images-
WHAT WEIGHTED IMAGES, USES FOR Pathology
T2 Weighted Images-
is acquired with a TR/TE of 400-700/10-20 msec.
A typical T1-weighted spin echo (SE) sequence
A typical T1-weighted spin echo (SE) sequence is acquired with HOW MANY MSEC
TR/TE of 400-700/10-20 msec.
IN Tissues and their T1 appearance OF Bone marrow
bright
IN Tissues and their T1 appearance OF Muscles
gray
IN Tissues and their T1 appearance OF Fluids
dark
IN Tissues and their T1 appearance OF White matter
whiter
IN Tissues and their T1 appearance OF Moving blood
dark
IN Tissues and their T1 appearance OF Gray matter
gray
IN Tissues and their T1 appearance OF BONE
DARK
IN Tissues and their T1 appearance OF FAT
BRIGHT
IN Tissues and their T1 appearance OF AIR
DARK
IN Tissues and their T1 appearance OF PATHOLOGIC CONDITIONS
DARK
WHAT IS T1 relaxation times for various ON BRAIN
T1 (ms) 1.5T
WHAT IS T1 relaxation times for various ON GRAY MATTER
921
WHAT IS T1 relaxation times for various ON White matter
787
WHAT IS T1 relaxation times for various ON Tumours
1073
WHAT IS T1 relaxation times for various ON Meningioma
979
WHAT IS T1 relaxation times for various ON Glioma
959
WHAT IS T1 relaxation times for various ON Oedema
1090
A T2-weighted fast spin echo (FSE) MR image can be acquired with a
TR/TE of >2000/80-100 msec.
can be acquired with a TR/TE of >2000/80-100 msec.
A T2-weighted fast spin echo (FSE) MR image
IN Tissues and their T2 appearance ON BONE MARROW
BRIGHT
IN Tissues and their T2 appearance ON MUSCLES
Gray (darker than T1)
IN Tissues and their T2 appearance ON MOVING BLOOD
DARK
IN Tissues and their T2 appearance ON WHITE MATTER
DARKER THAN GRAY
IN Tissues and their T2 appearance ON GRAY MATTER
GRAY
IN Tissues and their T2 appearance ON FLUIDS
BRIGHT
IN Tissues and their T2 appearance ON BONE
DARK
IN Tissues and their T2 appearance ON FAT
BRIGHT
IN Tissues and their T2 appearance ON AIR
DARK
IN Tissues and their T2 appearance ON PATHOLOGIC CONDITIONS
BRIGHT
WHAT T2 relaxation times for various tissues ON BRAIN
T1(ms)1.5T
WHAT T2 relaxation times for various tissues ON GRAY MATTER
101
WHAT T2 relaxation times for various tissues ON WHITE MATTER
92
WHAT T2 relaxation times for various tissues ON Meningioma
103
WHAT T2 relaxation times for various tissues ON TUMOURS
121
WHAT T2 relaxation times for various tissues ON GLIOMA
111
is commonly used in magnetic resonance (MR) imaging to suppress the signal from adipose tissue or detect adipose tissue.
Fat Suppression Pulse Sequence
WHAT T2 relaxation times for various tissues ON Oedema
113
WHAT SEQUENCE It can be applied to both T1 and T2 weighted sequences.
Fat Suppression Pulse Sequence
WHAT SEQUENCE The easiest way to identify fat saturated images is to look for adipose tissues in the body (e.g. subcutaneous fat and fat in bone marrow).
Fat Suppression Pulse Sequence
WHAT SEQUENCE after the administration of gadolinium contrast. This has the advantage of making enhancing tissue easier to appreciate.
Fat Suppression Pulse Sequence
WHAT IS Areas contain adipose tissues appear dark on T1 weighted fat saturated images.
T1 Fatsat
WHAT IS All the other characteristics of the T1 weighted fat saturated images remain the same as the T1 weighted Images
T1 Fatsat
Pathologies with adipose tissues content will appear as WHAT
As dark on T1 weighted fat saturated images
will appear as dark on T1 weighted fat saturated images
Pathologies with adipose tissues content
WHAT IS Areas contain adipose tissues appear dark on T2 weighted fat saturated images.
T2 Fatsat
All the other characteristics of the T2 weighted fat saturated images remain the same as the T2 weighted images
T2 Fatsat
4 kinds of Inversion Recovery Pulse Sequences:
short time inversion recovery(STIR)
fluid attenuation inversion recovery(FLAIR)
turbo inversion recovery magnitude (TIRM)
double inversion recovery(DIR)
WHAT Inversion Recovery Pulse Sequences:
Commonly used:
STIR AND FLAIR