MRI Procedure of IAM

1. MRI PROCEDURE OF IAM
Presenter :Sujan Karki
B.Sc. MIT 3RD Year
National Academy of Medical Sciences, Bir Hospital

2. When and why MRI???
• MRI is directed towards imaging of :
1. Fluid containing spaces in temporal bones
2. Vascular structure and their pathologies
3. Adjacent brain parenchyma
4. Evaluation of 7th and 8th cranial nerves

3. ANATOMY OF THE INNER EAR

6. Oval and round window
• The base of the stapes rocks in and out
against the membrane in the oval window.
•
The vibrations are transmitted from the
oval window via the endolymph to the hair
cells of the organ of Corti in the cochlea.
• The round window dissipates the pressure
generated by the fluid vibrations within the
cochlea and thus serves as a release valve.

7. ANATOMY OF INTERNAL ACOSTIC MEATUS

9. FACIAL NERVE

10. FACIAL NERVE

11. VESTIBULOCOCHLEAR NERVE
• The cochlea is positioned
anteriorly to the vestibule,
and the cochlear nerve
occupies the anteroinferior
aspect of the vestibular nerve
within the IAC.
• The superior and inferior
vestibular nerves, as well as
the cochlear nerve, join
together at the opening of
the IAC, known as the porous
acousticus.

12. Cerebellopontine angle meningioma in a 52-year-
old woman with left sensorineural hearing
loss. Axial 0.8-mm-thick SSFP MR image shows a
tumor that fills the internal auditory canal (arrow)
and extends into the cerebellopontine angle
cistern.

15. ACOSTIC NEUROMA
• Tumor that develops from Schwan
cells(benign)
• Categorized as glial cells which surrounds and
supports the neurons
• In peripheral nervous system Schwann cell
synthesize a fatty substance called myelin
which acts as a insulation sheath.
• Vestibular schwannoma is the compression of
seventh cranial nerve causing hearing loss on
one side, ringing of the ear, balance problem .

16. BELL’S PALSY
• Weakness or paralysis of the muscles of the one
side of face
• Cause is idiopathic(unknown)
• Often associated with viral and bacterial
infections( Herpes Simplex infection)
• A tumour compressing the facial nerve can
result in facial paralysis, but more commonly
the facial nerve is damaged during surgical
removal of a tumour.

17. VERTIGO
• Vertigo is a symptom describing the perception of
space rotating on its own.
• Two types of vertigo
Central
Peripheral
Central vertigo is related to brainstem and cerebellar
lesions
And usually accompanied by vertical movements
Peripheral vertigo is related to lesions related to
vestibular system and is presented with horizontal and
rotational movements

18. SENSORINEURAL HEARING LOSS
• Caused by the lesion in the cochlea or
cochlear nerve
• Conductive deafness is caused due to
the mechanical obstruction of sound
wave

19. TINNITUS
• Tinnitus is a sound in the head with no
external source
• The sound may seem to come from one
ear or both, from inside the head, or from
a distance.
• It may be constant or intermittent, steady
or pulsating.
• One of the most common causes of
tinnitus is damage to the hair cells in the
cochlea

20. Meniere’s Diseases
• Blockage of cochlear duct
• Recurrent attacks of tinnitus, hearing
loss and vertigo
• Sense of pressure in ear
• Distortion of sounds and sensitivity to
noises
• Sign: ballooning of cochlear duct, utricle
and saccule due to increase in
endolymphatic volume.

21. MICHEL ANOMALY
complete absence of inner ear structures

22. MICHEL ANOMALY

23. MONDINI ANOMALY

24. LABIRINTHITIS (Vestibular Neuritis)
• INFLAMMATION OF THE PERILYMPATHIC
SPACE OF INNER EAR
• MAY OCCUR DUE TO INFECTIONS( VIRAL OR
BACTERIAL) OR MAY BE AUTOIMMUNE.
• THREE STAGES
• ACUTE: CT appears normal ,contrast
enhanced MR shows faint enhancement
• FIBROUS: CT appears normal ,T2 weighting
MR shows loss of fluid signal
• OSSIFICATION : inner ear structure are
replaced by bones,( CT will show bone in
labyrinth with loss of fluid signal on T2
weighted MR

25. Acute Stage

26. FIBEROUS STAGE

27. OSSIFICATION STAGE

28. SUPERSEMICIRCULAR CANAL DEHISCENCE SYNDROME

29. Cholesteatoma
• A cholesteatoma is a skin growth that occurs in
an abnormal location, the middle ear behind
the eardrum
• Cholesteatomas often take the form of a cyst or
pouch that sheds layers of old skin that builds
up inside the ear.
• usually occurs because of poor eustachian tube
function as well as infection in the middle ear

30. Physics of CISS(green sequence)
• In GRE when TR <T2 relaxation time, residual transverse magnetization is left
over after radiofrequency pulse.
• This residual transverse magnetization is not wasted but fed back in longitudinal
magnetization with next RF pulse
• After the train of RF pulse, the repeated flipping of longitudinal magnetization
into transverse magnetization and vice versa results in a non-zero steady state
for both LM and TM
• For SSFP image formation, two types of signal are generated after each RF pulse
include the free induction decay signal which has mixed T1 and T2* weighting
and spin echo from prior RF pulse which has T2 weighting signal .
• In balanced steady state both FID and ECHO are used for image formation.

31. Continue…
• Gradient applied in slice selection, phase encoding and frequency encoding are
balanced by gradient of opposite polarity so that there is no net dephasing of
the transverse magnetization within each TR
• This gradient symmetry allows balanced steady state free precession to have
decreased pulsation, motion and susceptibility artefact,.
• CISSFIESTA-C are equivalent sequences with further modification of balanced
SSFP.
• 2 successive 3D bSSFP sequences are acquired one with alternating flip angle (+
and -) and another with + flip angle only, which helps in the reduction of banding
artefact.

32. Contrast of CISSFIESTA-C
• Contrast is the ratio of T2T1 of the tissue.
• Tissue with long T2 value such as water and CSF
appears bright compared to sold tissue with lower T2.
• While fat has shorter T2 value than fluid ,its high
T2T1 ratio also results in high signal on CISS
GE( GENERAL ELECTRONICS) FIESTA-C (FAST IMAGING EMPLOYING STEADY STATE ACQUISTION CYCLED
PHASE)
SIEMENS CISS(CONSTRUCTIVE INTERFEARENCE IN STEADY STATE)
PHILIPS BALANCED FAST FIELD ECHO(B-FFE)

33. Things to do before MRI examination at waiting room ……
• Review the form with the patient and ask additional questions if they do have any
stimulator (neuro, bone, etc.), aneurysm clips, cardiac valves, pacemakers, and any
type of metallic implants such as cochlear (hearing aid) or ocular.
• If the patient has been or had been held a relevant job such as working in a metal
factory, be extra cautious and question the patient regarding any work-related
accidents.
• Ask patient to change clothes with MR gown and remove any metallic objects including
jewelry, hair pins, watch, mobile devices, etc.
• Is recheck/final check necessary???Scan the patient with a metal detector one more
time before taking them into the MR room
• What about pregnant patient???? decision makers are patients or legal guardians, but
the potential advantages and risks must be explained
• Unconscious patient from Emergency or ICU should be screened carefully to remove
metallic objects such oxygen cylinders
• Take the weight of the patient ????

34. PATIENT PREPARATION FOR MRI :
Things to do during MRI exam at the scanner room
• After the screening if the patient have implants do not take him/her to
scanner room until the implants MR safety is confirmed. If safe to scan then:
• Give and instruct the patient how to insert MR compatible spongy ear plugs to
reduce the noise experienced by the patient.
• When you place coil, straighten the cables to avoid any loop and avoid direct
contact between the cable and bare skin.
• Give the patient the patient alarm bell and explain them that they should
press whenever they feel like they need it (burning sensation, claustrophobia,
pain, nausea, etc.).
• To reduce the potential PNS in MRI, avoid any closed circuits or loops in
patient body resulting from crossing the legs or holding hands above the
head.

36. PATIENT POSITIONING

37. Localizer

38. T2 TSE AXIAL
• SAGITTAL: POSITION THE BLOCK PARALLEL TO GENUE AND SPLEENIUM OF CORPUS CALLOSUM.
• CORONAL: POSITION THE BLOCK PERPENDICULAR TO THIRD VENTRICLE AND BRAINSTEAM.
• AXIAL : COVER WHOLE OF BRAIN FROM VERTEX TO THE LINE OF FORAMEN MAGNUM.
TR TE FA MATRIX FOV ST SG NEX
3000+ 100+ 130-150 320X320 210-230 3MM 10% 2

39. T2 TSE CORONAL
• AXIAL: POSITION THE BLOCK PARALLEL TO LEFT AND RIGHT IAMS.
• SAGITTAL: POSITION THE BLOCK PARALLEL TO THE BRAINSTEM.
• CORONAL :COVER THE IAMS FROM POSTERIOR BORDER OF SPHENOID
SINUS TO THE LINE OF FORTH VENTRICLE
TR TE FA MATRIX FOV ST SG NEX
3000-4000 110 130-140 256x256 150-180 3MM 10% 2

40. 3D CISS ( 3D SPACE OR 3D FIESTA)
• CORONAL: POSITION THE BLOCK PARALLEL TO LINE ALONG RIGHT AND LEFT IAMS
• SAGITTAL : POSITION THE BLOCK PERPENDICULAR TO BRAINSTEM.
• AXIAL : COVER THE IAMS FROM HIPPOCAMPUS TO THE LINE OF C1 VERTEBRAL
BODY
TR TE FA MATRIX FOV ST SG NEX
12-15 6-7 80 384x320 210-230 >1MM 10% 1

41. T1 TSE CORONAL
• AXIAL: POSITION THE BLOCK PARALLEL TO LEFT AND RIGHT IAMS.
• SAGITTAL: POSITION THE BLOCK PARALLEL TO THE BRAINSTEM.
• CORONAL: COVER THE IAMS FROM POSTERIOR BORDER OF SPHENOID SINUS TO
THE LINE OF FORTH VENTRICLE
TR TE FA MATRIX FOV ST SG NEX
400-600 15+ 90 320X320 210-230 3MM 10% 2

42. T1 TSE AXIAL
• SAGITTAL: POSITION THE BLOCK PARALLEL TO GENUE AND SPLEENIUM OF CORPUS CALLOSUM.
• CORONAL: POSITION THE BLOCK PERPENDICULAR TO THIRD VENTRICLE AND BRAINSTEAM.
• AXIAL: COVER WHOLE OF BRAIN FROM VERTEX TO THE LINE OF FORAMEN MAGNUM.
TR TE FA MATRIX FOV ST SG NEX
400-600 15-25 140 256x256 170-180 3MM 10% 2

43. Ice-cream cone appearance in CT and MRI

44. Michel’s deformity
Axial 3D FIESTA showing Michel's deformity on right side (red arrow) in the
form of complete absence of inner ear structures.

45. Axial 3D FIESTA showing dilated endolymphatic duct on
both sides

46. Cochlear ossification on both sides

47. Narrowed IAC on either side with absent B/L VCN complex

48. Vestibular Schwannoma
• Vestibular schwannomas represent 80-85% of
the CPA tumors.
• Most common site of schwannoma is Scarpa's
ganglion where the highest concentration of
Schwann cells.
• The growth rate of schwannoma is variable, but
usually it is slow, 1-2 mm/year.
• Homogenous contrast enhancement in most
cases.

49. Meningioma
• Meningiomas are solid, well-
circumscribed, and slow-growing tumors
that are composed of neoplastic
meningothelial cells originating from the
arachnoid layer of the meninges with a
broad attachment to the adjacent dura.
• Meningiomas are second most frequent
CPA tumor
• Hypointense on CISS sequence
obliterating the vestibulocochlear nerve
• Meningiomas show homogenous
enhancement on postcontrast T1WI

50. Arachnoid cysts
• Arachnoid cysts are benign, congenital, intra
arachnoidal space-occupying lesions representing
1% of all intracranial masses.
• They have clear CSF as its contents and do not
communicate with the ventricular system.
• MRI is the diagnostic technique of choice as it can
demonstrate the exact location, extent, and the
relationship of the arachnoid cyst to the adjacent
brain or spinal cord.
• Determination of whether the arachnoid cyst is
communicating to the CSF spaces is important in the
preoperative evaluation

51. Epidermoid cysts
• Epidermoid cysts are congenital intradural lesions
arising from the inclusion of ectodermal epithelial
elements during neural tube closure.
• They are the third most common CPA masses
after acoustic schwannomas and meningiomas.
• On T1WIs, these lesions are generally slightly
hyper- or iso-intense relative to the gray matter.
• The lesions are usually isointense relative to CSF
on T2WIs, but they may be slightly hyperintense
• Compression of the vestibulocochlear nerve seen
on CISS image
• Diffusion MR imaging sequence is the most
important sequence in differentiating epidemoid
and arachnoid cysts.
• Epidermoid cyst show restricted diffusion on DWI

52. Intra-axial tumors
• Intra-axial tumors at CPA include medulloblastoma,
ependymoma, hemangioblastoma, and metastasis.
• Medulloblastoma is a brain tumor of neuroepithelial
origin, which represents 15-30% of a pediatric brain
tumor and <1% of adult brain tumor.
• These are hypointense on T1WI and hyperintense
on T2WI
• he majority of intracranial ependymomas located in
the posterior fossa, which arise from the floor of the
fourth ventricle.

54. References
• Applications of 3D CISS sequence for problem solving in neuroimaging.
Divyata Hingwala, Somnathhatterjee, Chandrasekharan Kesavadas, Bejoy
Thomas, and Tirur Raman Kapilamoorthy. Indian J Radiol Imaging. 2011 Apr-
Jun; 21(2): 90–97
• Appearance of Normal Cranial Nerves on Steady-State Free Precession
MR Images. Sujay Sheth, Barton F. Branstett, IV, Edward J. Escott. Jul 1
2009
• High-field MRI versus high-resolution CT of temporal bone in inner ear pathologies
of children with bilateral profound sensorineural hearing loss: A pictorial essay. P.
Digge1 , R. K. N. Solanki2 , S. M. Paruthikunnan3 , D. S. Shah2 ; 1Manipal,
Karnataka/IN, 2 Ahmedabad/IN, 3Manipal/IN. ECR 2015, Educational Exhibit
• Magnetic resonance imaging of cerebellopontine angle lesions. Pratiksha
Yadav, Mansi Jantre, Dhaval Thakkar. : 2015 : 8 : 6: 751-759
• Practical applications of CISS in MRI Imaging. Yingming Amy Chen, Daniel
Chow, Jason Talbott, Christine Glastonbury, Vinil Shah. (2019) 231–242
• www.kenhub.com
• www.medviz.com
• www.radiologykey.com

55. Questions
• Which protocol will you go for, if the patient comes for the MRI examination
with the history of unilateral sensorineural hearing loss ?
• Explain ice-cream cone appearance in CT and MRI ?
• What are the common CP angle Lesions?
• What are the indications and contraindication of MRI IAM ?
• Why should we include CISS sequence in MRI of IAM?