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MRI Brain Sequences

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Nami cml

on 22 September 2013

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Transcript of MRI Brain Sequences

THE BRAIN INTRODUCTION:
Many patients presenting for scans of the head and neck require additional attention as they may be unconscious, confused or otherwise irritated due to their condition.
Extra care and added precautions must be taken when scanning these patients as simple tasks such as screening and positioning may become problematic.

EQUIPMENT, POSITION AND PATIENT CARE:
The patient is positioned supine with the head positioned closest to the magnet (head first).
A specialised head coil is mandatory to gain appropriately SNR and resolution.

CLINICAL INDICATIONS:
Tumours
Some tumours such as metastasis are secondary and so images must include the entire brain.
Other tumours such as pituitary adenomas are benign and so images with a small FOV are acquired so as to maximum detail.
Stroke
To correctly identify a stroke and define its exact location and extent within the head.
it is importnat to investigae why the stroke has occurred (embolus? vessel malformation?)
Infection
Such as meningitis or localised infections are detected and characterised
Multiple sclerosis
Pathologies of the IACs
Temporal lobe epilepsy
MRI excels at looking for small lesions or structural abnormalities
Nerve palsies
Fine structures are imaged verl well on MRI. Tracing the path of nerves
Pituitary sella lesions
Dementia
Hydrocephalus
Tumours of pharynx and neck
Trauma or iatrogenic
MRI's sensitivity and specificity to blood and edema products.

INTRAVENOUS CONTRAST:
Helps detect and characterize many pathologies that result in an increase or decrease in the normal vascularity of structures. Such pathologies and techniques includes:
Tumour/Infection/Inflammation/Post surgery and radiation therapy/Contrast enhanced MRA/Perfusion COMMON SEQUENCES TUMOUR/
INFECTION STROKE TEMPORAL LOBE EPILEPSY
(TLE) INTERNAL AUDITORY CANALS (IACs) - 8TH CRANIAL NERVE Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag FLAIR
axial Being a T2 weighted image, its primary purpose is to assess pathology within the brain Positioning:
Histoy off the T2 Axial.

This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF T2 Axial Positioning:
Hisotry off the FLAIR axial.

This sequence shows the anatomy of the brain in an axial plane.
It also serves as a good reference that can be compared with the same scan acquired after contrast. T1 axial Positioning:
History off the axial scans.

The primary purpose of a DWI is to detect infarcted brain parenchyma (i.e. a stroke). It also helps to characterize other pathology, e.g. tumours.
The DWI run for the brain on a 1.5T magnet usually results in 3 images:
a b = 0 image
a b = 1000 image
an apparent diffusion coefficient (ADC) image DWI Susceptibility weighted image
Positioning:
History off the axial scans

This is a T2 weighted image designed to enhance the appearance of molecules that cause magnetic susceptibility artifacts.
Iron in the blood that is not shielded by oxygen is one such molecules that will cause artifact. SWI Scout/Localiser
Positioning: Isocentre of the magnet
If the patient is positioned oblique images obtained will not be orthogonal. You may choose to re-align the scout to as to begin the examinatio with orthogonal images 3D
TOF 3D Time of flight Magnetic Rsonance Angiogram (MRA)
Positioning:
Sag T1: From the genu to the splenium of the corpus collosum to include above the circle of Willis and below the horizontal portion of the vertebral artery
Con scout: Perpendicular to the Falx cerebri.

The MRA results in bright vessels within a dark background.
It offes good raw images of blood vessels and results in a 3D dataset that can be post processed to show blood vessels in their entirely Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag FLAIR
Axial Being a T2 weighted image, its primary purpose is to assess pathology within the brain Positioning:
Histoy off the T2 Axial.

This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF T2 Axial Positioning:
Hisotry off the FLAIR axial.

This sequence shows the anatomy of the brain in an axial plane.
It also serves as a good reference that can be compared with the same scan acquired after contrast. T1 Axial Positioning:
History off the axial scans.

The primary purpose of a DWI is to detect infarcted brain parenchyma (i.e. a stroke). It also helps to characterize other pathology, e.g. tumours.
The DWI run for the brain on a 1.5T magnet usually results in 3 images:
a b = 0 image
a b = 1000 image
an apparent diffusion coefficient (ADC) image DWI
Axial C+
T1 Axial C+
T1 Cor (+/-) C+
FLAIR Axial The main features of a tumour/infection protocol is the addition of contrast.
Both pathologies are nearly always vascular and so will enhance after the administration of contrast.
It is always advisable to get at least 2 planes post contrast so as to show the exact nature of enhancement.
A Sag C+ T1 scan may also be required when pathology invloves the midline structure of the brain, e.g. 3rd ventricle of the falx cerebri. Tumours suspected in the skull base may require additional, thinner slices for increased resolution.
Fastsat sequences may also be required after administration of contrast due to overlying fat in small structures of the skull base that may mask contrast enhancement. It should be performed and after contrast is given when infections are suspected.
Pathologies such as meningitis and encephalitis will enhance on these sequences. Specialized sequences to visualiszd vascular pathways and assess affected territories. Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag TOF
MRA Being a T2 weighted image, its primary purpose is to assess pathology within the brain T2 Axial Positioning:
Hisotry off the FLAIR axial.

This sequence shows the anatomy of the brain in an axial plane.
It also serves as a good reference that can be compared with the same scan acquired after contrast. T1 Axial Positioning:
History off the axial scans.

The primary purpose of a DWI is to detect infarcted brain parenchyma (i.e. a stroke). It also helps to characterize other pathology, e.g. tumours.
The DWI run for the brain on a 1.5T magnet usually results in 3 images:
a b = 0 image
a b = 1000 image
an apparent diffusion coefficient (ADC) image

A stroke will appear as a hyperintense lesion on the b=1000 image but will have restricted movement of molecules within its cells, and thus be hypointense on the ADC map DWI
Axial T2
high resolution
posterior fossa (+/-) MRV
(2D TOF or CE) If the referring clinician suspecs venous sinus pathology has caused the aptients condition, a magnetic resonance venogram (MRV) may be programmed in addition to the regular stroke sequences.

The 2D TOF MRV is a robust technique that results in valuable information but a contrast enhanced technique generally results in more detail, particularly of the smaller blood vessels. FLAIR
Axial Positioning:
Histoy off the T2 Axial.

This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF 3D Time of flight Magnetic Rsonance Angiogram (MRA)
Positioning:
Sag T1: From the genu to the splenium of the corpus collosum to include above the circle of Willis and below the horizontal portion of the vertebral artery
Con scout: Perpendicular to the Falx cerebri.

The MRA results in bright vessels within a dark background.
It offes good raw images of blood vessels and results in a 3D dataset that can be post processed to show blood vessels in their entirely.

The other crucial sequence to be obtained. Slices used in a TOF sequence produce the best signal when they are positioned perpendicular to the blood sequence produce the best signal when they are positioned perpendicular to the blood flow.
Stenotic vessels are noted at areas where the blood vessel is narrowed whilst occluded vessels show an absence of blood flow. It must be remembered that whilst this technique is robust and results in variable information, there are advantages and disadvantages and artifacts do occur
Data that is acquired is post processed to form maximum intensity projection (MIP) images. Vessels may be removed and rotated so as to obtain as clear an image as possible of the main vessels within the head. A susceptibility weighted image is also a valuable sequence to use when imaging a stroke and will detect the presence of blood after a haemorrhage.
When a haemorrhagic event occurs, the iron in the blood becomes exposed and causes a magnetic susceptibility artifact. (Spin echo sequences may compensate for this artifact and reduce its effect. Gradient sequences and modified techniques enhance the magnetic susceptibility effect and signal the presence of free blood. Like all MRI imaging, particular attention to the clinical details and images acquired may reveal additional pathology that should be investigated. In the case a stroke is caused by a tumour for instance, we must acquire sequences as described above before progressed to administer IV contrast to assess the tumour. Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag TOF
MRA Being a T2 weighted image, its primary purpose is to assess pathology within the brain T2 Axial Positioning:
History off the axial scans.

The primary purpose of a DWI is to detect infarcted brain parenchyma (i.e. a stroke). It also helps to characterize other pathology, e.g. tumours.
The DWI run for the brain on a 1.5T magnet usually results in 3 images:
a b = 0 image
a b = 1000 image
an apparent diffusion coefficient (ADC) image

A stroke will appear as a hyperintense lesion on the b=1000 image but will have restricted movement of molecules within its cells, and thus be hypointense on the ADC map DWI
Axial T2
high resolution
posterior fossa Positioning:
Histoy off the T2 Axial.

This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF 3D Time of flight Magnetic Rsonance Angiogram (MRA)
Positioning:
Sag T1: From the genu to the splenium of the corpus collosum to include above the circle of Willis and below the horizontal portion of the vertebral artery
Con scout: Perpendicular to the Falx cerebri.

The MRA results in bright vessels within a dark background.
It offes good raw images of blood vessels and results in a 3D dataset that can be post processed to show blood vessels in their entirely.

The other crucial sequence to be obtained. Slices used in a TOF sequence produce the best signal when they are positioned perpendicular to the blood sequence produce the best signal when they are positioned perpendicular to the blood flow.
Stenotic vessels are noted at areas where the blood vessel is narrowed whilst occluded vessels show an absence of blood flow. It must be remembered that whilst this technique is robust and results in variable information, there are advantages and disadvantages and artifacts do occur
Data that is acquired is post processed to form maximum intensity projection (MIP) images. Vessels may be removed and rotated so as to obtain as clear an image as possible of the main vessels within the head. FLAIR
Axial FLAIR
Sag MULTIPLE SCLEROSIS This is a debilitating disease that results from myelin in the sheaths of the nervous tissue being replaced by plaques.
Routine sequences help identify the lesions and shoule be programmed for this condition, although T1 axial offers little use and is often omitted This view will better show the plaques as they typically radiate along the venous tracts from the corpus callosum (Dawson's finger) If indicated by the referring clinican or department protocol, contrast may be given to identify active MS lesions.
Only active lesions will enhance up to 3 to 4 minutes after the injection of contrast. Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag T2
high resolution
posterior fossa T2 3D
gradient volume
through IACs Slices currently used in the 3D T2 volume may get as low as 0.5mm or less and so are very capable of detecting small lesions.
The T2 high resolution scan is a major component of this protocl because pathology in the posterior fossa or surrounds may mimic that in the inner ear. FLAIR
Axial Positioning:
Histoy off the T2 Axial.

This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF IACs are fine nerve structures within the ear canal.
Sequences used to look at these structures must have high resolution so as to identify the small nerves and possible athology surrounding them. Other scans are required to screen the rest of the brain ensuring no intra-cerebral pathology is present. Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag 3D T1
volume Being a T2 weighted image, its primary purpose is to assess pathology within the brain T2 Axial Positioning:
Hisotry off the FLAIR axial.

This sequence shows the anatomy of the brain in an axial plane.
It also serves as a good reference that can be compared with the same scan acquired after contrast. T1 Axial T2
Cor Hi-resolution
through
tempraol bone Coronal gradient
or
Susceptibility weighted image FLAIR
Cor FLAIR
Axial Positioning:
Histoy off the T2 Axial.

This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF T1
Inversion recovery
Cor Again, a general survey of the brain is conducted to ensure there is no pathology present. These sequences ensure the finest detail images are acquired capable of detecting and characterizing minute lesions
Again T2 weighted images are best used to show pathology. T1 weighted images using inversion recovery technique will gain maximum resolution and contrast through these regions, particularly to look at the cortex of the brain. Abnormalities through this region are particularly likely to result in seziures and behavioural difficulties. This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF Older adults (classed as >50yrs at MMC) suffering new seziures will likely receive contrast enhanced sequences in addition to many of the above sequences.
This is becaue their condition is more likely to be a result of a toumor rather than cogenital abnormality. NERVE PALSIES Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag +/-
TOF
MRA Being a T2 weighted image, its primary purpose is to assess pathology within the brain T2 Axial
Brain Positioning:
Hisotry off the FLAIR axial.

This sequence shows the anatomy of the brain in an axial plane.
It also serves as a good reference that can be compared with the same scan acquired after contrast. T1 Axial
Fine slices T2 axial
FS
Fine slices 3D T2
gradient fine slices
7th nerve C+ T1 axial
Fine slice T2 cor
FS
Fine slices The 5th cranial nerve (Trigeminal nerve) may be compressed by the internal carotid as it passes from the pons, and so an MRA is required to show the anatomy of the structures through this region. C+ T1 cor
Fine slice Fat saturated FIne nerve structures are well visualised using MRI.
Axial and Coronal are the most informative planes used.
Clinicans are capable of identifying the nerve structures are causing the patients symptoms.
Fine slices through the anatomical area that nerve passes are performed. Typically, the cranial nerves are broken into separate regions based on their location within the skull base.
4th, 6th and 7th cranial are imaged together
9th, 10th, 11th and 12th cranial nerves are imaged together.
5th cranial nerve (trigeminal nerve) is imaged alone
(8th cranial nerve is the vestibulocochlear nerve as discussed in the IAC protocol previously) Exceptions to these protocols is taht the 7th cranial nerve also passes the IAC and so requires a high resolution 3D volume to be programmed in that region as well as the above sequences PITUITARY SELLA MICROADENOMA T1 Sag
Small FOV T2 FS Cor
Small FOV T1 Pre dynamic
Cor Small FOV C+ T1 FS
Cor Small FOV T1 Cor
Small FOV C+ T1 FS
Sag Small FOV C + T1 FS
0/1/2/3 mins
Dynamic Cor
Small FOV As adenomas involving the pituitary sella are benign, it is not necessary to image the entire brain. Sequet of the sella or have origins above the sella however must include sequences of the entire brain to evaluate spread or other intra cerebral pathology The FOV must be small and resolution high otherwise detection is made increasingly difficult.
Dynamic scanning is another method increasing the conspicuity of these lesions.
The pituitary gland is so vascular, enhancement of its cells occurs immediately after administration of contrast.
Enhancement of tumours however is delayed, and so they appear hypointense relative to the surrounding pituitary gland
In the minutes that follow, the signal intensity of the pituitary tissue decreases but the signal intensity of the tumour increases.
It is not possible to obtain high resolution images because these scans must be performed quickly
High resolution images are therefore acquired after the dynamic scans have been performed. MACROADENOMA/SUPRASELLA/POST OPERATIVE Tumours are larger than 1 cm. Suprasella tumors are those that grow upwards of the sella
Again, they do not require dynamic imaging but do require imaging of the rest of the brain to localize the tumour and ensure it is solitary. T1 Sag
Whole brain T1 Cor
Small FOV T2 FS Cor
Small FOV T1 Sag
Small FOV C+ T1 FS
Sag Small FOV T2 Axial
Whole brain C+ T1 FS
Cor Small FOV C+ T1 Axial
Whole brain DEMENTIA Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag Being a T2 weighted image, its primary purpose is to assess pathology within the brain Positioning:
Hisotry off the FLAIR axial.

This sequence shows the anatomy of the brain in an axial plane.
It also serves as a good reference that can be compared with the same scan acquired after contrast. T1 Axial Positioning:
History off the axial scans.

The primary purpose of a DWI is to detect infarcted brain parenchyma (i.e. a stroke). It also helps to characterize other pathology, e.g. tumours.
The DWI run for the brain on a 1.5T magnet usually results in 3 images:
a b = 0 image
a b = 1000 image
an apparent diffusion coefficient (ADC) image

A stroke will appear as a hyperintense lesion on the b=1000 image but will have restricted movement of molecules within its cells, and thus be hypointense on the ADC map T2
high resolution
temporal bone FLAIR
temproal lobes FLAIR
Axial Positioning:
Histoy off the T2 Axial.

This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF T2 Axial DWI
Axial Susceptibility weighted image
Positioning:
History off the axial scans

This is a T2 weighted image designed to enhance the appearance of molecules that cause magnetic susceptibility artifacts.
Iron in the blood that is not shielded by oxygen is one such molecules that will cause artifact. SWI
Axial/Cor
Gradient These sequences invlove careful assessment of the size of the brain structures.
Assessment is made of the brain using the routine sequences.
Two pathology weighted scans are also included to increase the conspicuity of fluid in and around the temporal lobes. In particular, note is made of hippocampus and amygdala, two structures in the temporal lob whose primary function is memory HYDROCEPHALUS Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag Being a T2 weighted image, its primary purpose is to assess pathology within the brain Positioning:
Hisotry off the FLAIR axial.

This sequence shows the anatomy of the brain in an axial plane.
It also serves as a good reference that can be compared with the same scan acquired after contrast. T1 Axial Positioning:
History off the axial scans.

The primary purpose of a DWI is to detect infarcted brain parenchyma (i.e. a stroke). It also helps to characterize other pathology, e.g. tumours.
The DWI run for the brain on a 1.5T magnet usually results in 3 images:
a b = 0 image
a b = 1000 image
an apparent diffusion coefficient (ADC) image

A stroke will appear as a hyperintense lesion on the b=1000 image but will have restricted movement of molecules within its cells, and thus be hypointense on the ADC map T2
high resolution
Sag (+/-)
Flow studies
(in- / through-
plane) FLAIR
Axial Positioning:
Histoy off the T2 Axial.

This sequence is a T2 weighted scan also and so primarily used to detect pathology.
This inversion recovery scan nulls the signal from pure fluid such as CSF, however most of the fluid from pathological processes that has a different relaxation time is not nulled and remains bright.
It is particularly useful to show pathology in or around the ventricles or other areas that may be masked by the bright signal of the CSF T2 Axial DWI
Axial So screening sequences will detect and assess hydrocephalus but additional sequences may be required required to show detail regarding the flow of CSF through the brain It may be caused by obstruction of the pathway of cerebro-spinal flusid (CSF) as it makes its way from ventricles through to the spinal canal. These sequences offer more information about pathology that may be present within the midline structures. The in-plane flow study will assess and display the CSF flow at one Sag slice position through the structures in the midline of the brain.
In-plane flow in one direction will be indicated by dark signal and flow in the opposite direction will indicate bright signal.
The intensity of the signal will be relative to the velocity of the flow.

Through-plane flow studies, usually measuredat the cerebral adequact, require an axial slice to be positioned exactly perpendicular to the flow through the adequct.
CSF moving perpendicular to this slice in both direction will again be displayed bright and dark according to the velocity of flow.
The added feature is that exact quantitative measurements can be taken and plotted on a time V's velocity graph
Careful adjustment of the veolcity encoding setting is required as is a pulse oximeter to measure the heart rate. PHARYNX &
NECK STRUCTURES Positioning:
Axial: lined along the Falx cerebri
Coronal: lined along the Falx cerebri

T1 Sag is usually the first image acquired because it gives a good overview of the anatomy of the brain in a Sag plane.
It should also result in a clear view of the anterior and posterior commissure.
An imaginary line connecting these two points from the angle at which axial scans should be aligned.

Positioning:
Sag T1: aligned along an imaginary line connecting tghe anterior commissure to teh posterior commissure (AC-PC line)
Coronal scout: Aligned perpendicular to the Falx cerebri T1 Sag T1
Cor T2 FS
Cor Positioning:
Hisotry off the FLAIR axial.

This sequence shows the anatomy of the brain in an axial plane.
It also serves as a good reference that can be compared with the same scan acquired after contrast. T1 Axial Positioning:
History off the axial scans.

The primary purpose of a DWI is to detect infarcted brain parenchyma (i.e. a stroke). It also helps to characterize other pathology, e.g. tumours.
The DWI run for the brain on a 1.5T magnet usually results in 3 images:
a b = 0 image
a b = 1000 image
an apparent diffusion coefficient (ADC) image

Cancerous node appear hyperintense on the b=1000 and hypointense on the ADC map.
Post contrast imaging is again crucial to diagnose and characterise lesions within the neck. DWI
Axial C+
T1 FS
Cor C+
T2 FS
Axial T2 FS
Axial The region between the skull base and the neck include the nasopharynx, oropharynx, and hypopharynx. Included are structures such as the parotid gland, base of tongue, larynx as well as the hard and soft palate regions.
Detection and assessment of tumours is the most common clinical indicatino for their referral. Previous imaging and patient history are again important to ensure the exact location of suspected pathology. To localise pathology. Fatsat is important to null the signal from fat and increase the conspicuity of these lesions
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