CHEST RADIOLOGYAlex Nguyen FSU College of Medicine MS4

12/09/13

Discovery of X-Rays

Wilhelm Conrad Röntgen German physicist Won the first Nobel

Prize in Physics in 1901 for study of X-rays

Basic Radiographic Densities Able to distinguish

four densities: Air Fat Soft tissue (water) Bone (metal)

Only four densities, otherwise all looks the same

Difficult to tell difference between types of same density (muscle vs. artery)

One View = No View

Standard Radiographs are 2D images of three-dimensional objects Structures overlay

each other in same plane

No depth with one view

Standard Posterior-Anterior View

Whenever possible, chest x-rays are done in PA View Heart closer to film

(less magnification) Patient able to fully

inspire (show more lung)

Sharper image Moves scapulae out

of the way

Alternate Anterior-Posterior View When patients are

too sick and unable to stand for a PA View, we resort to an AP View Heart further away

from film (magnified) Cannot measure

cardiothoracic ratio Patient cannot take

deep breath Image less sharp

PA vs. AP View

Lateral CXR

Difficult to see behind the heart with frontal views

Lateral view allows better view of mediastinum and gives depth (two views)

Can see lower lung fields that are behind diaphragm on frontal views

Other Views

Lateral Decubitus Helps identify pneumothorax or pleural

effusions Air rises, water falls

Chest Anatomy

Important to know anatomy of the chest to help read chest x-rays and identify locations of pathology Lobes of the lung Mediastinum structures Heart locations Diaphragm

Chest Anatomy

Chest Anatomy

Right lung – 3 lobes

Left lung – 2 lobes

RLL

RML

RUL

LUL

LLL

Chest Anatomy

Right lung (3 lobes) Minor horizontal

fissure Frontal and lateral

view Major oblique fissure

Lateral view Left lung (2 lobes)

Major oblique fissure Lateral view CHF producing increased fluid in minor fissure

Chest Anatomy

Chest Anatomy

Aorta starts on right anterior, courses to left posterior

Abdominal aorta lies slightly left of midline

Chest Anatomy

Diaphragm normally higher on right due to liver

Upper abdomen may show gas in stomach or colon (hepatic or splenic flexure)

Reading a CXR

Compare to baseline previous radiographic studies

Helps differentiate normal from disease in complicated cases

Reading a CXR

Assess quality first: Rotation –

clavicular heads aligned with spinous processes

Penetration – vertebral bodies behind heart barely visible

Inspiration – diaphragm down to 9-10th posterior rib or 5-7th anterior rib

*Posterior ribs are straight, anterior ribs are curved

Reading a CXR

Have a standard method and use it every time

Divide chest into three vertical zones – helps eyes focus

Leave the most important last – the lungs Check bony anatomy,

upper abdomen first

Mediastinum

Main structures: Trachea Carina Aortic arch Left and Right Hilum Right atrium Left ventricle

Knowing which lobes of the lung contact each part of the contours can help identify location of pathology (silhouette sign)

Mediastinal Contours

Mediastinal Contours

Silhouette Sign

X-Rays able to show differences in radiographic densities by location

If similar radiographic densities contact each other, will not show a difference

Thus, the basis for the Silhouette Sign

There are normal anatomic silhouette signs Left diaphragm and

left heart border There are many

abnormal silhouette signs Pneumonia in RML and

right heart border Both are water density

Silhouette Sign

Name derived from disruption of normal silhouette of anatomic structures

Silhouette Sign

Left Heart Border obscuring Left DiaphragmRML Pneumonia obscuring Right Heart Border

Anatomic Pathologic

Silhouette Sign

Helps diagnose and localize lung pathology

Air Bronchogram Sign

The opposite of the Silhouette Sign

Silhouette sign takes advantage of similar radiographic densities

Air Bronchogram uses the idea of dissimilar radiographic densities

Normally, bronchi are not seen in lung periphery due to air on air contact

When lungs become consolidated, if bronchi are aerated, they will appear on film

Air Bronchogram Sign

Seeing bronchi on CXR is abnormal – Air Bronchogram Sign

CT Scan demonstrating Air Bronchogram Sign

Air Bronchogram Sign

Causes include: Lung consolidation Pulmonary edema Non-obstructive pulmonary atelectasis Neoplasm Normal expiration

Air Bronchogram Sign

If bronchi are also obstructed, will not see Air Bronchogram Sign – pneumonia with secretions filling bronchi, asthma, bronchi tumor obstruction

Cross Sectional Radiology

CT Scan MRI

Planes: Axial (Transverse) Sagittal Coronal

Computed Tomography (CT)

CT Scanner takes multiple X-Rays in different angles and computer constructs them together

IV contrast dye may be added to distinguish vessels

Exposed to higher radiation than typical CXR

Computed Tomography (CT)

CT Scanner routinely produces Axial images

Same data is reconstructed to produce: Coronal Sagittal images

Same data is reconstructed in Subsets to optimize viewing of certain tissues

Lung window Mediastinal window Bone window

Computed Tomography (CT)

Computed Tomography (CT)

CT has better contrast discrimination than conventional X-rays Able to distinguish different types of soft

tissue (muscle vs. fluid) Hounsfield Units (HU) measurements:

Lung -800 Fat -80 Fluid 0 Muscle +40 Bone > 350

Computed Tomography (CT)

Coronal view with accessory bronchus Sagittal view with coarctation of aorta

Computed Tomography (CT)

High-resolution CT scan: Thinner sections Reconstruction algorithms to sharpen

edges Evaluates interstitial lung disease

Chest Radiology Pathology

Atelectasis Pulmonary Edema Pneumonia Pleural Effusion Pneumothorax Interstitial Disease Emphysema & COPD Mediastinal Mass

Atelectasis

Collapse or incomplete expansion of the lung

Surrounding structures will deviate towards collapsed lung Trachea Fissures Mediastinum Diaphragm

Can also see vascular or bronchial crowding

Pleural Effusion

Can have similar appearance to Atelectasis

Surrounding structures will deviate away from pulmonary effusion (must be large)

Can move with gravity Lateral decubitus

view

Pleural Effusion

Amount of fluid: Erect PA: 175 ml Erect lateral: 75 ml Lateral Decubitus: >5

ml Supine: >500 ml

Clues: Blunted CVA Meniscus Thick fissure

Easier to see on lateral with small effusions

Pleural Effusion

If unable to stand erect, can do Lateral Decubitus on affected side – must be free, not loculated

Pleural Effusion

Loculated pleural effusion in minor fissure

Also called “Pseudotumor” because it often resolves over time

Pleural Effusion

Ultrasound now commonly used to estimate fluid amount and plan for thoracentesis

Pneumothorax

Causes: Spontaneous Iatrogenic (surgery,

central line placement)

Asthma Trauma

Clues: Radiolucent air in

pleural space Visceral pleura line

Pneumothorax

Can have a ball-valve like mechanism only allowing air in and not out Tension Pneumothorax Compromise venous

return flow Pushes mediastinum

away Medical emergency

requiring needle decompression

Pneumothorax

Signs of Tension PTX: Rapid onset

respiratory failure Decreased breath

sounds Deviated trachea Jugular venous

distention Treatment:

Immediate needle decompression

Pneumonia

Lung consolidation without volume loss Bacteria Viral Mycoplasma Fungi

Usually no structural shift towards lesion

Often confused with Atelectasis – volume loss, structural shift ipsilateral

Types: Lobar – Strep

pneumo Lobular - Staph Interstitial -

Mycoplasma Aspiration

pneumonia

Pneumonia

Lobar Pneumonia

Interstitial Pneumonia

Interstitial Disease

Alveoli vs. Interstitium Supporting structures:

Vessels Lymphatics Bronchi Connective tissue

Normally visible within 2/3rd of lung, outer third beyond resolution of typical CXR

Appears white on film, alveoli black when aerated

Normal CXR

Interstitial Disease

Causes: Idiopathic pulmonary

fibrosis (most common)

Autoimmune disease Occupational exposure Medications Radiation

A type of restrictive lung disease

Interstitium becomes inflamed, scarred

Interstitial Disease

Interstitial Disease

Hazy, ground-glass appearance

Volume loss Honey-comb

appearance Broad category of

diseases High resolution

CT scan helpful to differentiate

Pulmonary Edema

Two types: Cardiogenic

CHF Non-cardiogenic

Adult Respiratory Distress Syndrome, ARDS

Near-drowning Acute

glomerulonephritis Allergic reaction Inhalation injury Aspiration

Cardiogenic Fluid backs up

into pulmonary veins, leaks out

Non-cardiogenic Altered capillary

membrane permeability

Pulmonary Edema

Cardiogenic Pulmonary Edema Cephalization of

pulmonary vessels Kerley B lines –

interlobar septa “Bat wing” pattern Large

cardiothoracic ratio

PA View helpful

Pulmonary Edema

Kerley B Lines CHF with Batwing Appearance

Pulmonary Edema

Non-Cardiogenic Pulmonary Edema Can have similar

appearance to cardiogenic edema

More widespread and diffuse

Will not resolve as quickly as cardiogenic edema

Air bronchograms more common

Non-Cardiogenic Pulmonary Edema

Emphysema & COPD

Emphysema – loss of elastic recoil of lung due to destruction of alveolar wall Hyperinflation of

lung Flattened

diaphragms Bullae Barrel chest

Mediastinal Mass

Anterior (4 T’s): Thymic tumors Thyroid mass Teratoma Terrible

lymphadenopathy Middle:

Lymphadenopathy Hiatal hernia Aortic aneurysm

Posterior: Lymphadenopathy Aortic aneurysm Nerve tumor

Mediastinal Mass

Watch for silhouette signs Anatomy helps localize lesions – watch

for shift

ICU Radiology

Films taken in ICU are often AP views

Identify correct tubes and line placement Endotracheal

tubes Nasogastric tubes Central venous

catheters Swan-Ganz

catheter

ICU Radiology

Correct placement of ET tube Correct placement of NG tube

ICU Radiology

NG tube into Right Lung Bronchi Central Venous Catheter into SVC

References

1. Goodman, LR. Felson’s Principles of Chest Roentgenology: Third Edition. Philadelphia: Saunders; 2007.

2. http://www.med-ed.virginia.edu/courses/rad/cxr/