Introduction to Computed Tomography of the Chest and Paranasal Sinuses Carolina Souza MD, PhD Associate Professor Diagnostic Imaging The Ottawa Hospital

Introduction to Computed Introduction to Computed Tomography of the Chest and Tomography of the Chest and

Paranasal SinusesParanasal Sinuses

Carolina Souza MD, PhDCarolina Souza MD, PhDAssociate ProfessorAssociate ProfessorDiagnostic ImagingDiagnostic ImagingThe Ottawa HospitalThe Ottawa Hospital

Learning ObjectivesLearning Objectives

• Demonstrate a basic understanding of how a CT scan is Demonstrate a basic understanding of how a CT scan is obtainedobtained

• Describe the normal anatomy of the chest, including the lungs Describe the normal anatomy of the chest, including the lungs and mediastinum and paranasal sinus on CT scan and mediastinum and paranasal sinus on CT scan

• Recognize a mediastinal and a lung window on a CT of the Recognize a mediastinal and a lung window on a CT of the chestchest

• Recognize airspace disease, interstitial disease, a lung nodule Recognize airspace disease, interstitial disease, a lung nodule or mass and a pleural effusion or mass and a pleural effusion

• Enumerate 3 indications for performing a CT of the chestEnumerate 3 indications for performing a CT of the chest

What is Computed Tomography?What is Computed Tomography?

• Patient lies on table which advances slowly through Patient lies on table which advances slowly through

the gantry which houses the x-ray tube and detectors the gantry which houses the x-ray tube and detectors

X-ray beam of a defined thickness rotates around the X-ray beam of a defined thickness rotates around the

patient, detectors are on opposite sidepatient, detectors are on opposite side

• Yields axial images of the body Yields axial images of the body

• Images in multiple other planes can be reconstructed Images in multiple other planes can be reconstructed

without distortion of anatomywithout distortion of anatomy

Typical CT ScannerTypical CT Scanner

Patient on CT TablePatient on CT Table

Axial CT ImageAxial CT Image

RIGHT LEFT

Coronal ReconstructionCoronal Reconstruction

3D Color Surface Rendered 3D Color Surface Rendered ReconstructionReconstruction

CT of the ChestCT of the Chest• Two kinds of images for each identical axial slice (different from CT abdomen Two kinds of images for each identical axial slice (different from CT abdomen

and head) and head)

• Mediastinal windowMediastinal window

• Computer reconstructs images so that different shades of gray seen are in Computer reconstructs images so that different shades of gray seen are in

a narrow window of densitiesa narrow window of densities

• Good for muscles, contrast, bone, fat and vesselsGood for muscles, contrast, bone, fat and vessels

• Lungs not well seen: they look blackLungs not well seen: they look black

• Lung windowLung window

• Computer reconstructs images to see a much wider spectrum of graysComputer reconstructs images to see a much wider spectrum of grays

• Good to see lungs (Good to see lungs (but mediastinal structures, bones, soft tissues all but mediastinal structures, bones, soft tissues all

appear white)appear white)

Mediastinal WindowMediastinal Window

RIGHT LEFT

Narrow Range of Visible Grays

Fat

Contrast

Air

Bone

Softtissue

Lung WindowLung Window

RIGHT LEFT

Wide Range of Visible Grays

Lunginterstitium

Use of ContrastUse of Contrast

• Iodine-basedIodine-based

• Injected intravenouslyInjected intravenously

• Appears white (hyperdense) on CTAppears white (hyperdense) on CT

• Makes assessment of vascular abnormalities and Makes assessment of vascular abnormalities and

mediastinal anatomy easiermediastinal anatomy easier

• Different pathological processes may show Different pathological processes may show

differential uptake of contrast which helps in differential uptake of contrast which helps in

diagnosisdiagnosis

Use of ContrastUse of Contrast

• Problem:Problem:

• Excreted by kidneysExcreted by kidneys

• NephrotoxicityNephrotoxicity

• Abnormal renal functionAbnormal renal function

• Diabetes, multiple myelomaDiabetes, multiple myeloma

• MetforminMetformin

• Always look at patients’ creatinine before ordering Always look at patients’ creatinine before ordering

CTCT

Normal Anatomy - MediastinumNormal Anatomy - Mediastinum

R. innom vein

L. innom veinL. brachiocephalicartery L.common

carotid art

L. subclavianartery


R. innom vein

L .innominate vein

Aortic arch

Esophagus


SVC Aortic arch


Right mainstembronchus

SVCAscending aorta

Azygous vein


ThymusL pulmonary artery

Descending aortaRight mainstembronchus

SVCAscending aorta


Descending aorta

Ascending aorta

Main pulm artery

Right PA


Left lower lobe PARight lower lobe PA


Left atrium

Right ventricleRight atrium

Ascending aorta

Descending aorta


Left Atrium

Rt Atrium Rt ventricle Lt ventricle

Top of liver

Lobar Anatomy ReviewLobar Anatomy Review

Normal Anatomy – Airway and LungsNormal Anatomy – Airway and Lungs

Trachea

Right upperlobe

Left upper lobe

Left upper lobe

Right upperlobe

Carina

Normal Anatomy – Airways and LungsNormal Anatomy – Airways and Lungs

Right mainstembronchus

Left mainstembronchus

Minor fissure

Right interlobar bronchus

Major fissureRight lower lobe

Left upper lobe

Left lower lobebronchusMajor fissure

Left lower lobe

Major fissureMajor fissure

Normal Anatomy - LungsNormal Anatomy - Lungs

Major fissure

Major fissure

Major fissure

Major fissure

Left lower lobe

Lingula

Right lower lobe

Right middlelobe

Right lower lobe

Right middlelobe

Left lower lobe

Lingula

Normal Anatomy - LungsNormal Anatomy - Lungs

Top ofrighthemidiaphram

Approach to CT of the ThoraxApproach to CT of the Thorax• Assess mediastinumAssess mediastinum

• Look around vessels for abnormal soft tissue density Look around vessels for abnormal soft tissue density • Lymph nodesLymph nodes

• Mediastinal massMediastinal mass

• Look inside vessels for abnormal soft tissue densityLook inside vessels for abnormal soft tissue density• Pulmonary emboliPulmonary emboli

• Aortic dissectionAortic dissection

• Assess lungsAssess lungs• Too white (hyperdense)Too white (hyperdense)

• Too black (hypodense)Too black (hypodense)

Approach to CT of the ThoraxApproach to CT of the Thorax

• Assess pleuraAssess pleura• FluidFluid• ThickeningThickening• PneumothoraxPneumothorax

• Assess bones and soft tissuesAssess bones and soft tissues• FractureFracture• Bone destructionBone destruction• Soft tissue massSoft tissue mass

• Assess upper abdominal structuresAssess upper abdominal structures

Assessment of the MediastinumAssessment of the Mediastinum

• Best assessed with IV contrastBest assessed with IV contrast

• Lymph nodesLymph nodes

• Right paratracheal (beside the trachea)Right paratracheal (beside the trachea)

• Hilar (around pulmonary arteries and mainstem Hilar (around pulmonary arteries and mainstem

bronchi)bronchi)

• Subcarinal (below carina)Subcarinal (below carina)

• Aortopulmonary window (under aortic arch but Aortopulmonary window (under aortic arch but

above left pulmonary artery)above left pulmonary artery)

Lymph NodesLymph Nodes

Normal Right Paratracheal Node

Lymph NodesLymph Nodes

Normal Left Hilar Node

Lymph NodesLymph NodesRight Hilar and Subcarinal NodeNormal

MediastinumMediastinum

• Mediastinal compartmentsMediastinal compartments• Anterior Anterior • MiddleMiddle• PosteriorPosterior

Anterior MediastinumAnterior Mediastinum

• Anterior to great vessels and heartAnterior to great vessels and heart• Terrible T’sTerrible T’s

• TeratomaTeratoma• ThymomaThymoma• Thyroid enlargementThyroid enlargement• Terrible lymphoma (lymph nodes)Terrible lymphoma (lymph nodes)

Anterior MediastinumAnterior Mediastinum

Anterior Mediastinal MassAnterior Mediastinal Mass

Lymphoma

Middle MediastinumMiddle Mediastinum

• Hila, heart, great vessels, ascending Hila, heart, great vessels, ascending aorta and archaorta and arch• Lymph nodesLymph nodes• AneurysmAneurysm• DissectionDissection

Middle MediastinumMiddle Mediastinum

Middle Mediastinal AbnormalityMiddle Mediastinal Abnormality

Aortic dissection

Posterior MediastinumPosterior Mediastinum

• Posterior to tracheaPosterior to trachea• EsophagusEsophagus• Paravertebral regionsParavertebral regions• Descending aortaDescending aorta



• Esophageal tumoursEsophageal tumours

• Descending aortic aneurysm, dissectionDescending aortic aneurysm, dissection

• Neurogenic tumoursNeurogenic tumours

• Enlarged lymph nodes (metastases, Enlarged lymph nodes (metastases, lymphoma)lymphoma)

Posterior Mediastinal LesionPosterior Mediastinal Lesion

Neurogenic tumor

Evaluation of the LungsEvaluation of the Lungs

• Too white (increased opacity, hyperdensity)Too white (increased opacity, hyperdensity)

• Too black (decreased opacity, hypodensity) Too black (decreased opacity, hypodensity)

Evaluation of the Lungs – Too WhiteEvaluation of the Lungs – Too White

• Airspace consolidationAirspace consolidation

• AtelectasisAtelectasis

• Interstitial diseaseInterstitial disease

• Nodule or massNodule or mass

Airspace ConsolidationAirspace Consolidation

• Fairly homogeneous opacity obscuring vesselsFairly homogeneous opacity obscuring vessels

• Caused by filling of airspaces with fluid, cells or bothCaused by filling of airspaces with fluid, cells or both

• No associated volume lossNo associated volume loss

• Visible air-containing bronchi (air bronchograms)Visible air-containing bronchi (air bronchograms)

• Most common cause – bacterial pneumoniaMost common cause – bacterial pneumonia

Evolution of the Air-bronchogramEvolution of the Air-bronchogram

As fluid-filled alveoli coalesce, only the bronchus contains air and appears as a black column

CT Air-bronchogramCT Air-bronchogram






No air in the alveoli No air in the alveoli

• Increased opacityIncreased opacity

• Loss of volume Loss of volume

• Elevated hemidiaphragmElevated hemidiaphragm

• Mediastinal/tracheal shift to abnormal sideMediastinal/tracheal shift to abnormal side

• Fissure displaced towards opacityFissure displaced towards opacity

AtelectasisAtelectasis

AtelectasisAtelectasis

Collapsed lower lobeNo air-bronchograms

OpacityDisplaced major fissure towards opacityLoss of volume






Interstitial DiseaseInterstitial Disease

• Disease that primarily affects pulmonary Disease that primarily affects pulmonary interstitiuminterstitium• Too many linesToo many lines• Too many dots (nodules)Too many dots (nodules)• Too many lines and dots (both)Too many lines and dots (both)

Interstitial DiseaseInterstitial Disease

Lines Dots

Too Many LinesToo Many Lines

Metastases to the Lung Lymphatics

Too Many DotsToo Many Dots

SarcoidosisSarcoidosis

Idiopathic Pulmonary FibrosisIdiopathic Pulmonary Fibrosis






Spiculated margin

Lung NoduleLung Nodule

Lung cancer

Lung MassLung Mass

Lung cancer

Multiple Lung NodulesMultiple Lung Nodules

Metastastes

Benign Lung NoduleBenign Lung Nodule

Smoothcontour

Benign Lung NoduleBenign Lung Nodule

Complete calcification

Lung Nodules – Benign Lung Nodules – Benign FeaturesFeatures

• Lack of growth > 2 yrsLack of growth > 2 yrs

• Extensive calcificationExtensive calcification

• Smooth marginsSmooth margins

• Small size (< 2 cm)Small size (< 2 cm)

Evaluation of the PleuraEvaluation of the Pleura

• FluidFluid

• Free flowing (meniscus)Free flowing (meniscus)

• Loculated (convex margin)Loculated (convex margin)

• ThickeningThickening

• Smooth (benign)Smooth (benign)

• Nodular (malignant)Nodular (malignant)

Pleural FluidPleural Fluid

Meniscus

Uncomplicated Pleural Effusion

Loculated Pleural EffusionLoculated Pleural Effusion

Empyema (complicated pleural effusion)

Convex margin

Pleural Thickening/FluidPleural Thickening/Fluid

Nodular

Nodular

Malignant Mesothelioma

Evaluation of the Bones and Evaluation of the Bones and Soft TissuesSoft Tissues

• FractureFracture

• Bone destructionBone destruction

• Soft tissue massSoft tissue mass

Bone DestructionBone Destruction

Lung cancerinvadingchest wall

Indications for Thoracic CTIndications for Thoracic CT

• Lung nodule on CXRLung nodule on CXR

• Staging of lung cancerStaging of lung cancer

• Mediastinal or hilar abnormality on CXRMediastinal or hilar abnormality on CXR

• Interstitial lung disease on CXRInterstitial lung disease on CXR

• ?Aortic dissection?Aortic dissection

• ?Pulmonary embolism?Pulmonary embolism

• Pleural effusion/thickening ? CausePleural effusion/thickening ? Cause

Spiculated margin

Malignant Lung NoduleMalignant Lung Nodule

Lung cancer

Indications for ThoracicCTIndications for ThoracicCT








Lung Cancer StagingLung Cancer Staging

Mediastinalinvasion









Posterior Mediastinal Lesion Posterior Mediastinal Lesion

Esophageal Carcinoma









Indications for CTIndications for CT








Aortic DissectionAortic Dissection

Intimal flap

Intimal flap









Acute Pulmonary EmboliAcute Pulmonary Emboli

Normal









Pleural Fluid/ThickeningPleural Fluid/Thickening

Pleural Metastases

CT of the Paranasal SinusesCT of the Paranasal Sinuses

Paranasal Sinuses – Axial Paranasal Sinuses – Axial AnatomyAnatomy

Frontal sinus Top of orbit


Sphenoid sinus

Globe Ethmoid sinus Lens


Maxillary sinus

Nasal septum

Paranasal Sinuses – Coronal Paranasal Sinuses – Coronal AnatomyAnatomy

Nasal septum

Frontal sinus


Sphenoid sinus Globe

Turbinate


Ethmoid sinus

Maxillary sinus


Sphenoid sinus

Indications for Paranasal Indications for Paranasal Sinus CTSinus CT

• Unresolving sinus infectionUnresolving sinus infection

• Suspicion of sinusitis complicationSuspicion of sinusitis complication

• Anatomical deliniation prior to sinus Anatomical deliniation prior to sinus surgery for chronic sinusitissurgery for chronic sinusitis

• If staging of neoplasm required – If staging of neoplasm required – consider MR consider MR

Acute SinusitisAcute Sinusitis

Sinusitis with Orbital Sinusitis with Orbital ExtensionExtension

Bone destruction

Opacified maxil-lary sinus

What You Need to KnowWhat You Need to Know

• Demonstrate a basic understanding of how a CT Demonstrate a basic understanding of how a CT scan is obtainedscan is obtained

• Identify some basic anatomy of the chest, neck and Identify some basic anatomy of the chest, neck and paranasal sinusesparanasal sinuses

• Recognize a mediastinal and a lung window on a CT Recognize a mediastinal and a lung window on a CT of the chestof the chest

• Recognize airspace disease, a lung nodule or mass Recognize airspace disease, a lung nodule or mass and a pleural effusion and a pleural effusion

• Enumerate 3 indications for performing a CT of the Enumerate 3 indications for performing a CT of the chest and paranasal sinuseschest and paranasal sinuses

Thank youThank you

[email protected]@ottawahospital.on.ca

Documents

Introduction to Computed Tomography of the Chest and Paranasal Sinuses Carolina Souza MD, PhD Associate Professor Diagnostic Imaging The Ottawa Hospital