MRI Flashcards
What is Larmor equation : frequency ?
Magnetic field strength x gyromagnetic ratio
What is gyromagnetic ratio ?
denoted by the symbol γ (gamma) is the ratio of the magnetic momentum in a particle to its angular momentum.
Equation for total scanning time ?
TR x NEX x Number of phase encoding steps
- Number of excitations (NEX) or number of signal averages/acquisitions (NSA) are measurement parameters. They are used to represent the number of times each line of k-space data is acquired and are primarily used to improve the signal-to-noise (SNR) ratio.
What is the coverage and what sequences for MRI Brain and orbits do we use at UHWI?
Normal MRI Brain
Sagittal T1WI fse 5mm
Axial T2WI fse 5mm
Axial FLAIR 5mm
Coronal T2WI fse 5mm
T2* GRE
DWI
MRI ORBITS
At 5mm – BrainT1WI Fse (pre and post Gd): Sagittal
At 3mm – Orbits
(1) Coronal T1/T2WI Fse
(2) Axial T1Fat Sat/T2 WI
T1 Fat Sat WI Fse: Coronal, Axial
*DWI SENSE - sensitivity encoding - increased detection of cranial bone marrow metastases
*Thin - 3mm
* Regular - 5mm
* Survey - 10 mm - axial, coronal, sagittal
Coverage:
Orbits Only Coronal Coverage: Anterior margin of globe to anterior surface of pons, perpendicular to axis of the orbital segment of the optic nerves.
Orbits Only Axial Coverage: Superior margin of orbital rim to inferior margin of orbital rim, angled to be in-plane with the orbital segments of the optic nerves.
Whole Brain Sagittal Coverage: Angle to interhemispheric fissure. Cover at least 1cm above vertex through skull base. Cover entire nose.
Whole Brain Axial Coverage: Angle to corpus callosum. Cover at least 1cm above vertex through skull base. Cover entire nose.
What sequence for MRI Brain with gadolinium do we use at UHWI?
Sagittal T1WI fse 5mm
Axial T2WI fse 5mm
Axial FLAIR 5mm
Coronal T2WI fse 5mm
T2* GRE 5mm
DWI
Post Gad. Sagittal T1WI fse 5mm
Post Gad. Coronal T1WI fse 5mm
Post Gad. Axial T1WI fse 5mm
What sequences for MRI Brain seizures do we use at UHWI?
Normal MRI Brain (Seizure protocol)
Sagittal T1WI fse 5mm
Axial T2WI fse 5mm
Axial FLAIR 5mm
Coronal T2WI fse 5mm
Coronal FLAIR 3mm
T2* GRE
Axial 3D T1 SPGR 1mm
DWI
What is the MRI Brain pituitary fossa UHWI protocol ?
Axial FLAIR 5mm (whole brain)
Coronal T2WI fse 3mm (pituitary fossa)
Coronal T1WI fse 3mm (pituitary fossa)
Coronal T1WI fse 3mm + Gad (pituitary fossa)
Sagittal T1WI fse 3mm + Gad (pituitary fossa)
AxialT1WI + Gad 5mm (whole brain)
Scan extent: The sequences for this purpose should be performed with small FOV (field of view) targeting the sella.
What is the coverage of MRI Temporal bones (IAM/CPA) and what is the UHWI protocol?
Normal MR Temporal Bones
Axial FLAIR 5mm (whole brain)
Axial T1WI fse 3mm (temporal bones)
Axial T2WI fse 3mm (temporal bones)
Axial 3D FIESTA
Coronal T2WI fse 3mm (temporal bones)
Coronal T1WI fse 3mm (temporal bones)
Coronal T1WI fse 3mm + Gad (temporal bones)
Axial T1WI fse 3mm + Gad (temporal bones)
*Scan extent of temporal bones: From arcuate eminence through the mastoid tip
- The arcuate eminence stands out as a prominent rounded elevation on the anterior surface of the petrous part of the temporal bone. It is positioned to the lateral side of the trigeminal impression and the hiatuses for the greater and lesser petrosal nerves. This elevation is caused by the superior, or anterior, semicircular canal’s dome that lies just beneath the surface within the petrous bone. Right next, lateral to the arcuate eminence, there’s a sunken area of bone called the tegmen tympani, which forms the roof of both the tympanic cavity and the mastoid antrum.
What is the coverage of MRI C spine and what is the UHWI protocol?
Normal MRI C Spine
Sagittal T1WI fse 3mm
Sagittal T2WI fse 3mm
Sagittal T2FATSAT 3mm
Axial T2WI 4mm
Axial T2* 4mm
Scan extent:
sagittal images:
angulation: parallel to the cervical spinal axis and the spinous processes
volume: includes the whole vertebral bodies and the facet joints, in a craniocaudal direction, should include the craniocervical junction up to the second thoracic vertebra
slice thickness: ≤3 mm
axial images (long stack):
angulation: perpendicular to the cervical spine
volume:
variable depends on the clinical question and/or the visible pathology
if clinical indication is generic, sufficient to include inferior half of C3 to superior half of T1
may acquire in upper and lower blocks depending on cervical curvature to ensure slices intersect perpendicularly with nucleus pulposus
slice thickness: ≤3 mm
coronal images*
angulation: parallel to the cervical spinal axis and transverse processes
volume: includes the posterior pharyngeal wall and the ligamentum nuchae
slice thickness: ≤3 mm
What is the coverage of MRI T spine and the UHWI protocol
MRI T SPINE:
Sagittal T1 and T2 WI
Axial T2WI
Sagittal T2W Fat Sat
Scan extent:
sagittal images
angulation: parallel to the thoracic spine axis and the spinous processes
volume: includes the whole vertebral bodies and the facet joints
slice thickness: ≤3 mm
axial images (long stack)
angulation: perpendicular to the thoracic spine
volume:
variable depends on the clinical question and/or the visible pathology
if clinical indication is generic, sufficient to include inferior half of T3 to superior half of T7
ensure slices intersect perpendicularly with nucleus pulposus
slice thickness: ≤3 mm
coronal images*
angulation: parallel to the thoracic spinal axis and the costovertebral joints
volume: includes the whole vertebral body and the spinous process
slice thickness: ≤3 mm
axial images (short stacks)*
angulation: perpendicular to the thoracic spine parallel to the intervertebral discs
volume: variable depends on the clinical question and/or the visible pathology
slice thickness: ≤3 mm
What is the coverage of MRI L spine and the UHWI protocol
Sagittal T1WI fse 4mm
Sagittal T2WI fse 4mm
Sagittal T2FATSAT 4mm
Axial T2WI 4mm
Scan extent:
sagittal images:
angulation: parallel to the lumbar spinal axis and spinous processes
volume: includes the whole vertebral bodies and the facet joints
slice thickness: ≤3 mm
coronal images:
angulation: parallel to the lumbar spinal axis and transverse processes
volume: includes the whole vertebral body spinal canal and posterior laminae
slice thickness: ≤3 mm
axial images (long stack):
angulation: perpendicular to the lumbar spine
volume:
variable depends on the clinical question and/or the visible pathology
if clinical indication is generic, sufficient to include upper block (inferior half of L3 to superior half of L5) and lower block (inferior half of L5 to superior half of sacrum)
ensure slices intersect perpendicularly with nucleus pulposus
slice thickness: ≤3 mm
axial images (short stacks)
angulation: parallel to the intervertebral discs in question
volume: variable depends on the clinical question and/or the visible pathology
slice thickness: ≤3 mm
What is the UHWI MRI Hip protocol and the scan extent
MRI Hip:
Sagittal T2* PD fat sat,
T1 Axial
T1 Coronal T2*, T1, PD fat sat.
Scan extent:
coronal images: in case of suspected extraarticular or acetabular pathology, labral or chondral lesions
angulation: strictly coronal
volume: includes everything from the anterior margin of the symphysis to the ischial bone
slice thickness: ≤3 mm
coronal oblique images: in case of proximal femoral pathology e.g. osteonecrosis of the hip, transient bone marrow oedema syndrome or assessment of cam morphology
angulation: parallel to the femoral neck axis
volume: includes whole acetabulum proximal femur and trochanter
slice thickness: ≤3 mm
sagittal images:
angulation: strictly sagittal
slice thickness: ≤3 mm
volume: includes the greater trochanter and the whole acetabulum
axial images: in case of suspected extraarticular pathology,
angulation: strictly axial to the body axis
volume: from the anterior inferior iliac spine to the proximal femur including the lesser trochanter
axial oblique: in case of articular or proximal femoral pathology
angulation: parallel to the femoral neck axis
slice thickness: ≤3 mm
3D imaging
angulation: coronal
spatial resolution: isotropic ≤0.7 mm
- MR arthrography:
The most accurate procedure for the assessment of femoroacetabular impingement, labral and chondral lesions including intraarticular loose bodies.
intermediate weighted (fat-saturated)
technique: IM fast spin echo
plane: coronal oblique
T1 weighted
technique: T1 fast spin echo
planes: sagittal, axial oblique
T1 weighted (fat-saturated)
technique: T1 fast spin echo
plane: coronal oblique
3D imaging
purpose: for radial reconstructions in femoroacetabular impingement, labral or chondral pathology
technique: 3D GRE
acquisition plane: coronal or axial, radial MPRs along the femoral neck axis
What is the UHWI MRI Pelvis protocol and scan extent
Axial, sagittal and coronal T2W1
Sagittal and coronal T1W1
Axial and sagittal T1W1 post gadolinium Coronal and axial T2 fat sat.
Planning
coronal images:
angulation: strictly coronal to the body axis
volume: skin to skin
slice thickness: ≤4 mm
axial images:
angulation: strictly axial to the body axis
volume: from the iliac crest to the lesser trochanter
slice thickness: ≤4 mm
sagittal images:
angulation: strictly sagittal to the body axis
volume: depends on the clinical question
slice thickness: ≤4 mm
coronal oblique images:
angulation: along the axis of the symphysis
volume: includes the whole symphysis
slice thickness: ≤3 mm
What is the UHWI protocol and scan extent for MRI Ankle
MRI ANKLE
Sagittal T2* PD fat sat, T1
Axial T1
Coronal T2*, T1, PD fat sat.
axial images:
angulation: perpendicular to the distal tibia and parallel to the tibiotalar joint
volume: about 3-5 cm above the tibiotalar joint to the plantar fascia
slice thickness: ≤3 mm
coronal images:
angulation: parallel to the malleolar axis
volume: depends on the question but should include at least the whole tibiotalar joint, the talus and navicular bone but could sometimes include also the metatarsal bases
slice thickness: ≤3 mm
sagittal images:
angulation: perpendicular to the malleolar axis
volume: includes medial and lateral malleolus
slice thickness: ≤3 mm
axial oblique images:
angulation: with a posteroinferior tilt of about 45° perpendicular to the posterior facet of the calcaneus
volume: should include the tibiotalar joint and both malleoli
slice thickness: ≤3 mm
sagittal oblique images:
angulation: with an inferolateral tilt about 45° in course of the anterior tibiofibular ligament
volume: about 8 slices, should contain the anterior and posterior syndesmosis
What is the UHWI MRI foot protocol and scan extent
MRI RT FOOT:
Sagittal PD fat sat, T1
Coronal T1, PD fat sat, STIR
Axial T1, PD fat sat, T2*
Entire foot scan extent: https://mrimaster.com/plan-foot/ : The slices must be sufficient to cover the foot from the tip of the toe up to the tarsal bones.
Mid to forefoot:
Planning
A typical MRI of the ankle might look like as follows:
axial oblique images:
angulation: parallel to the long axis of the 1st metatarsal bone
volume: from dorsal skin to plantar skin
slice thickness: ≤3 mm
coronal oblique images:
angulation: perpendicular to the long axis of the 1st metatarsal bone
volume: depends on the question but should include at least the proximal interphalangeal joints up to the midtarsal (Chopart) joint
slice thickness: ≤3 mm
coronal images: (supine position, ankle coil)
angulation: parallel to the tibial axis
volume: depends on the question but should include at least the proximal interphalangeal joints up to the midtarsal (Chopard) joint
slice thickness: ≤3 mm
sagittal images:
angulation: parallel to the axis of the 2nd and 3rd metatarsal bones and the rearfoot
volume: from medial skin to lateral skin
slice thickness: ≤3 mm
