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Imaging of the Paranasal Sinuses

Bettlach

24.08.2018

14. Sommerschule

Christoph Schlegel

https://www.orl-hno.ch/home.html

Christoph Schlegel Sommerschule 2018

Conventional Radiology

NNH-Status: okzipito-frontal: frontal sinus, anterior ethmoid

okzipito-nasal : maxillary and frontal sinus

axial: sphenoid and ethmoidal sinus

Radiation exposure:

2 mGy per exposure

(dose for cataract 2 Gy)


Conventional Radiology

inadequate sensivity and specifity

superseded by CT

Single detector row CT

2 Zeilen 1990

4 Zeilen 2000

8 Zeilen 2002

16 Zeilen 2004

64 Zeilen 2005

2x 64 Zeilen 2006

2x 128 Zeilen 2009

Multi detector row CT

4

16

Multislice Spiral CT


Paranasal Sinus CT Protocol

high resolution axial scan from alveolar process to frontal sinus

collimation 0.6mm

overlapping slice reconstruction 0.6/0.4mm, mAs <200

reconstruction: axial, coronal, sagittal

iv contrast*: tumor, inflammation, vascular lesion

not required for preop assessment of anatomy


Review: Radiation Dose

• radiation dose paranasal sinus CT 0.5-1mGy

• conventional x-ray paranasal sinus 0.2 mGy/expos.

• average diagnostic dose /per capita CH: 1mGy, GB 0.33mGy

• transatlantic flight (round trip) 0.1mGy

• cataract of eye lens: > 2 Gy


• preoperative anatomy, residual mucosal disease

• pattern of bone destruction, skull base defects

• navigation- CT , CT guided biopsies

CT

MRI

• soft tissue differentiation: retention, tumor, cellularity,

vascularity

• meningeal, neural, vascular involvement


Complementary Role CT MR


Meningo-Encephalocele



Clival Chordoma


Angiography

diagnostic use for selected cases

superselective embolisation: intractable epistaxis; M. Osler

embolisation of tumors


Juvenile Nasopharyngeal Angiofibroma


Orbital Complication: Subperiostal Abscess


Endocranial Complikation: Epidural and Soft Tissue Abscess in Frontal Sinusitis


Chronic Rhinosinusitis (without Nasal Polyps)

N.B.: after medical treatment


Chronic Rhinosinusitis (with Nasal Polyps)

N.B.: after medical treatment


Red Flags…

Consider other diagnosis:

unilateral symptoms

bleeding, crusting

cacosmia

orbital symptoms( oedema, displaced globe, double

vision)

severe frontal headache, frontal swelling

signs of meningitis

neurological signs

urgent investigation and intervention


Granulomatose mit Polyangiitis (M. Wegener)


Aspergilloma (fungus ball)


Odontogenic Sinusitis


Inverted Papilloma


Inverted Papilloma


Mucocele of Maxillary Sinus


Mucocele of Sphenoid Sinus

Dehiscent Internal Carotid Artery


Complicated Nose Fracture


Zygomatic Fracture


CSF-Leak

High resolution CT

MRI (T2)

β2-transferrin or β-trace

In selected cases: Intrathecal fluorescein injection


CSF-Leak


Dacryo CT Scan


Dacryo CT Scan


FESS: Preoperative Evaluation (CT Checklist)

uncinate process

ethmoidal roof, skull base

ethmoidal arteries

orbit, optic nerve

internal carotid artery

anatomical variations of ethmoidal cells


Uncinate Process

Simmen D, Jones N: Manual of Endoscopic Sinus Surgery. Thieme 2014

A B1 B2


Preoperative Checklist: Uncinate Process

Typ A (~ 75%): Insertion at Lamina

papyracea

«Recessus terminalis»

Frontal sinus drainage

pathway directly in middle

meatus



Typ B1: Insertion at skull base


pathway in ethmoidal

infundibulum



Typ B2: Insertion at middle turbinate


pathway in ethmoidal

infundibulum

Wormald PJ: The agger nasi cell: the key to understand the anatomy of the frontal recess Otolaryngol Head Neck Surg 2003; 129:497-507

Frontal Recess

Anatomy of the Frontal Recess

"frontal drainage pathway"

"fronto-ethmoidal cell"

"agger nasi cell"

Frontal Recess: Sagittal Reconstruction

Fronto-ethmoidal cells:

• Agger nasi cell

• K1 to K4 cells

• Suprabullar cells

• Frontal bullar cells

• Interfrontal sinus septal cell



anterior

posterior

(medial)


Preoperative Checklist: Ethmoid Roof Cribriform Plate

Preoperative Checklist: Anterior Ethmoidal Artery

Preoperative Checklist: Optic nerve

Preoperative Checklist: Internal Carotid Artery

Concha bullosa media

Haller Cell

Haller Cell

Onodi Cell

Pneumatized Inferior Turbinate

3 Nervs ???

Nervus opticus

Nervus maxillaris

Nervus vidianus

Cone Beam CT (Digitale Volumentomographie)

http://www.google.ch/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjl3qnygb3cAhXJ_aQKHQAxBmMQjRx6BAgBEAU&url=http://newtom.dev.cefla-srv.redturtle.it/en/products/newtom-5g&psig=AOvVaw2JgpwTR96Zf0OvKT3DMHd9&ust=1532703021936826


Cone Beam CT

Corresponds to a C-arm with 3D images

Digital volume tomography

Cone revolves around patient for 360°

Since 2000

Office use, no need for a radiologist


Low dose multislice CT Cone beam CT

MSCT DVT

Acquisition time ( motion artefacts)

2 sec 20-40 sec

Radiation exposure 0.2-0.5 mSV (+ 30-40%)

0.1-0.3 mSV

Image homogenity + +

Bone window Soft tissue window

+ +

+ -

Cost - +

Image reconstruction + +

De Cock et al. A comparative study for image quality and radiation dose of a cone beam computed

tomography scanner and a multislice computed tomography scanner for paranasal sinus imaging.

Eur Radiol (2015) 25:1891–1900

Al Abduwani et al. Cone beam CT paranasal ainuses versus low dose meltidetector CT studies.

Am J Otolaryngol (2016)37:59-64

Navigation: Localization Systems

Optical tracking systems Electromagnetic tracking systems

+ cordeless + free movement of surgeon

- line of sight - magnetic interference


Accuracy

Depends on: CT scan and its reconstruction

Registration !

Patient motion, motion of reference points !

Generally accepted range: ± 1 mm (=2 mm)

Shift in accuracy from anterior to posterior

up to 9 mm (z axis)

Intraoperative Manual Registration Refinement

New feature to adjust disaccuracy i.e. in the depth

Before After

Navigation starts the day before surgery by:

Analysis of the CT-scan (coronar,axial,sagittal):

where is the frontal drainage pathway?

Step by step surgical plan


Suggested Reading

Simmen D, Schuknecht B: Computed tomography of paranasal sinuses.

A preoperative checklist. Laryngo-Rhino-Otology 1997; 76:8-13

Simmen D, Jones N: Manual of endoscopic Sinus and Skull Base

surgery. Thieme 2014, second edition

Wormald PJ: Endoscopic Sinus Surgery: Anatomy, Three-Dimensional Reconstruction, and Surgical Technique . Thieme 2018, fourth edition