CT CHESTCT CHESTGiselle Revah

University of Toronto Class of 0T7

Dr. N. Jaffer Staff Radiologist MSH and University of Toronto

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO

THE BASICSTHE BASICS

1. The different options for CT imaging of the lung

2. An approach to looking at chest CT’s

3. A few disease patterns that will help you impress

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO

CT TYPESCT TYPES1. Standard2. High Resolution3. Low Dose4. CT Angio

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO

1. STANDARD CT1. STANDARD CT• Slice thickness: 3-10 mm • scans a large volume, very quickly • Covers the full lung• +/- contrast

Indications• CXR abnormality • Pleural and mediastinal abnormalities• Lung cancer staging• F/U metastases• Empyema vs abscess

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO • narrow x-ray beam collimation: 1-1.3mm vs. conventional 3-10mm

• cross sections are further apart: 10 mm• high definition images of lung

parenchyma: vessels, airspaces, airway and interstitium

• No contrast

2. HIGH RESOLUTION 2. HIGH RESOLUTION (HRCT)(HRCT)

STANDARD CT HRCT

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO

2. HIGH RESOLUTION 2. HIGH RESOLUTION (HRCT)(HRCT)Indications• Hemoptysis • Diffusely abnormal CXR• Normal CXR with abnormal PFT’s • Baseline for pts with diffuse lung disease• Solitary pulmonary nodules• Reversible (active) vs. non-reversible

(fibrotic) lung disease • Lung biopsy guide• F/U known lung disease • Assess Rx response

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO• Premise: lower dose radiation will not

reduce the diagnostic functionality of the scan (eg. 250 mAs 50 mAs)

• Detail is decreasedUses• Screening

– ongoing trials • F/U

– infections– post lung transplant– metastases

3. LOW DOSE3. LOW DOSE

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO• contrast injected into peripheral vein • injection timing/rate controlled automatically • dye is where you want it during scan• replaced conventional catheter angiogram

Indications• Pulmonary embolism• Aortic aneurysms• Aortic dissection

Risks• Iodinated contrast:

– Allergic/ nephrotoxic

4. ANGIOGRAPHY 4. ANGIOGRAPHY (CTA)(CTA)

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO Three Windows1. Soft Tissue

APPROACHING THE APPROACHING THE ANATOMYANATOMY

2. Bone

3. Lung

DISEASE PATTERNS

CT TYPE

ANATOMY

INTROLook at these structures• Thyroid• Chest wall• Pleura

Heart• Chambers• CA calcifications• Pericardium

Vessels• Aorta• PA• Smaller vasculature

Nodes • mediastinal • axillary

1. SOFT TISSUE 1. SOFT TISSUE WINDOWWINDOW

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO

Ascending aorta

Descending aorta

Main pulmonary artery

L pulmonary artery

R pulmonary artery

SVC

Azygous vein

Esophagus

What is this duct?

DISEASE PATTERNS

CT TYPE

ANATOMY

INTROManubrium/ Sternum

VertebraeR Ribs L Ribs

2. BONE WINDOW2. BONE WINDOW

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO

3. LUNG WINDOW3. LUNG WINDOWAIRWAYS Bronchial Tree

Central

LLL

LUL

Fissure

RUL

RLL

PARENCHYMA

Fissure

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO 1. Air Bronchograms2. Bronchiectasis3. Septal Thickening4. Ground Glass Opacity5. Emphysema6. Nodules7. Filling Defect

COMMON COMMON PATHOLOGIC PATHOLOGIC FEATURESFEATURES

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRODescription• Bronchi become visible due to increased

attenuation of surrounding lung

• Implies proximal bronchi patency

• Excludes pleural or mediastinal lesion

DDx• Non-obstructive atelectasis

• Pneumonia

• Pulmonary edema

• Hemorrhage

• Bronchioloalveolar carcinoma

• Lymphoma

1. AIR 1. AIR BRONCHOGRAMSBRONCHOGRAMS

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRODilatation of medium-sized bronchi (>2 mm) impaired clearance recurrent infection bronchial

damage

Types1. Cylindrical2. Cystic3. Varicose

HRCT is diagnostic tool of choice

DDx• Infection• Bronchial obstruction• Cystic fibrosis • Primary ciliary

dyskinesia

2. BRONCHIECTASIS2. BRONCHIECTASIS

What type is this?

• Immunodeficiency states • alpha 1-Antitrypsin deficiency • RA and Sjögren• Pulmonary fibrosis

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO • abnormalities of interlobular septa or peripheral alveoli

• thickening and outlining of the secondary pulmonary lobules is best seen on HRCT

• often well depicted in the apices

Most Common Causes • pulmonary edema • pulmonary hemorrhage • lymphangitic cancer spread

3. SPETAL 3. SPETAL THICKENINGTHICKENING

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO• common nonspecific finding

• decreased air content without totally obliterating the alveoli

• increased lung opacity not sufficient to obscure pulmonary vessels

4. GROUND GLASS 4. GROUND GLASS OPACITIESOPACITIES

DDx• Alveolitis or interstitial

pneumonitis– Hypersensitivity pneumonitis– IPF– Sarcoidosis

• Pulmonary edema• Resolving pneumonia/

hemorrhage

Early

Dense

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO• permanent enlargement of air

spaces distal to the terminal bronchioles

• destruction of the walls without obvious fibrosis

Young pt with bullous emphysema at the lung bases.

What’s the diagnosis?

DDx• smoking • alpha 1-Antitrypsin deficiency• IV drugs• Immundeficiency• Vasculitis • Connective tissue disorders

5. EMPHYSEMA5. EMPHYSEMA

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO3 Types1. Centriacinar/lobular • respiratory bronchioles periphery• upper half of lungs • smoking

2. Panacinar• destroys entire alveolus uniformly • lower half of lungs• homozygous alpha1-antitrypsin

deficiency

3. Distal acinar/paraseptal• distal airway, alveolar ducts, and alveolar sacs• around the lung septae or pleura• apical bullae may spontaneously

pneumothorax

5. EMPHYSEMA5. EMPHYSEMA

What 2 types are found here?

DISEASE PATTERNS

CT TYPE

ANATOMY

INTROCT can detect nodules 3-4 mm

Benign• Small, unchanged over 2 years• Less than 15-20 HU • fat within (hamartoma) • halo sign: ground-glass surrounding nodule

indicates infection

Malignant• Enhancement of greater than 20 HU• Caution: active granulomas/ infectious lesions• Spiculated• Multiple

6. NODULES6. NODULES

Can you spot the nodule?

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO

Circumscribed nodules suspect metastatic disease

Septated nodules, suspect primary lung malignancy

Neoplastic Infectious InflammatoryBenign (hamartoma)Bronchogenic CaMetsLymphoma

GranulomaAbscess

Rheumatoid arthritisWegener’s Sarcoidosis

6. NODULES6. NODULES

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO• Pulmonary Embolism is a well defined hypodensity in the

pulmonary artery • CTA sensitive for PE (90%) • can’t evaluate arteries below 4th segmental level

DDx: • Anatomical landmarks and variants eg intersegmental

nodes• Vascular tumor invasion • Technical psuedo filling defects (eg flow artifact)

7. FILLING DEFECTS7. FILLING DEFECTS

DISEASE PATTERNS

CT TYPE

ANATOMY

INTRO1. Engeler CE, Tashjian JH, Trenkner SW, and Walsh JW.

Ground Glass Opacity of the Lung Parenchyma: A Guide to analysis with High Resolution CT. AJR 1993; 160: 249-251.

2. Collins, J. CT signs and patterns of lung disease. Radiol Clin North Am. 2001 Nov;39(6):1115-35.

3. Lee JKT, Sagel SS, Stanley RJ, Heiken JP. Computed Body Tomography with MRI correlation. 3rd ed. Raven Press NYC, 1998.

REFERENCESREFERENCES