14. Sommerschule Imaging of the Paranasal Sinuses Bettlach 24.08.2018 Christoph Schlegel
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Conventional Radiology inadequate sensivity and specifity superseded by CT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 Multi detector row CT Multislice Spiral CT 4 16 2 Zeilen 1990 4 Zeilen 2000 8 Zeilen 2002 16 Zeilen 2004 64 Zeilen 2005 2x 64 Zeilen 2006 2x 128 Zeilen 2009
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 conventional x-ray paranasal sinus average diagnostic dose /per capita transatlantic flight (round trip) 0.5-1mGy 0.2 mgy/expos. CH: 1mGy, GB 0.33mGy 0.1mGy cataract of eye lens: > 2 Gy
CT preoperative anatomy, residual mucosal disease pattern of bone destruction, skull base defects navigation- CT, CT guided biopsies 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 A B1 B2 Simmen D, Jones N: Manual of Endoscopic Sinus Surgery. Thieme 2014
Preoperative Checklist: Uncinate Process Typ A (~ 75%): Insertion at Lamina papyracea «Recessus terminalis» Frontal sinus drainage pathway directly in middle meatus
Preoperative Checklist: Uncinate Process Typ B1: Insertion at skull base Frontal sinus drainage pathway in ethmoidal infundibulum
Preoperative Checklist: Uncinate Process Typ B2: Insertion at middle turbinate Frontal sinus drainage pathway in ethmoidal infundibulum
Frontal Recess Wormald PJ: The agger nasi cell: the key to understand the anatomy of the frontal recess Otolaryngol Head Neck Surg 2003; 129:497-507
Anatomy of the Frontal Recess "frontal drainage pathway" "fronto-ethmoidal cell" "agger nasi cell"
Frontal Recess: Sagittal Reconstruction Suprabullar cells Frontal bullar cells Interfrontal sinus septal cell Fronto-ethmoidal cells: Agger nasi cell K1 to K4 cells
anterior (medial) posterior
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)
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 Acquisition time ( motion artefacts) Radiation exposure MSCT DVT 2 sec 20-40 sec 0.2-0.5 msv (+ 30-40%) Image homogenity + + Bone window Soft tissue window Cost - + Image reconstruction + + + + 0.1-0.3 msv + - 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