CP Week 14: Chest imaging and Cardiopulmonary Implications of Diseases

Why is a chest radiograph (CXR) considered a mainstay of basic healthcare?

It is quick, cheap, noninvasive, and provides valuable diagnostic information for many pathologies.

Radiographic anatomy of the chest x-ray

Bony thorax

Respiratory organs

The heart

The mediastinum

Hilum

diaphragm

Review of Bony Thorax

What you see on a CXR of the bony thorax is incidental but still useful

Bones help to identify soft tissue anatomy and the location of lesions

High vs Low contrast

high = T-spine radiographs to see bones

low = Used in CXR to see vessels and organs

What is the standard patient position for a CXR and why?

Posterior-Anterior (PA) position; it places the heart and lungs closer to the receptor, minimizing magnification.

When is an AP (Anteroposterior) chest radiograph typically used?

When a patient is too ill to stand, requiring the receptor to be placed behind them while sitting or lying in bed.

How many ribs are typically visible on a standard CXR?

6 anterior ribs and 10 posterior ribs.

Bronchogram

x-ray record of the bronchus produced by bronchography

What is the difference between the parietal and visceral pleura?

The parietal pleura lines the chest wall, while the visceral (pulmonary) pleura covers the lung surface and dips into fissures.

What is the cardiothoracic ratio used for in a CXR?

It is a radiographic estimate of heart size; the heart width should be less than half the width of the chest at the diaphragm level.

normal cardiothoracic ratio

<1/2

What structures are contained within the mediastinum?

The heart, great vessels, trachea, and esophagus.

What does hilar enlargement on a CXR typically represent?

Inflammation of the lymph nodes or pulmonary hypertension.

In radiographs, what's called the diaphragm is actually the

sum of all densities of the organs under the sheet of muscle that is the diaphragm

What is the costophrenic sulcus?

A recess between the diaphragm and the chest wall where pleural fluid can gravitate.

On inspiration the dome of the diaphragm is at the

10th rib intercostal space

What is the significance of seeing free air below the hemidiaphragms on a CXR?

It indicates a perforated bowel, potentially due to cancer, diverticulitis, peptic ulcer disease, or trauma.

Free air is easiest to see in the

right hemidiaphragm interposed between the diaphragm and the liver

phrenic nerve injury or ascites

elevation of diaphragm

Indications for CXR per ACR

Evaluate s&s potentially related to respiratory, CV and upper GI systems

Eval of extrathoracic diseases secondarily involving chest

FU of known thoracic dz processes

Monitoring of pts with life-support devices

Surveillance studies required by law like TB or occupational lung exposure screenings

Routine chest exam projections

Erect PA

Erect left lateral

Mediastinal shift

abnormal movement of the structures within the mediastinum to one side of the chest cavity

How can you assess for rotation on a PA chest radiograph?

Compare sternoclavicular joints to midline distance

Compare rib cage margin to midline distance

Sternum should be midline, superimposed over thoracic spine

Trachea should be midline

What is the 'silhouette sign'?

The loss of the normal radiographic border between air in the lungs and the soft tissues of the heart or diaphragm.

Assess the Diaphragm

normal. elevated R hemidiaphragm due to liver

What does the 'air bronchogram' sign indicate?

Fluid accumulation around terminal airway vessels, which can be caused by infection (pneumonia), blood (hemorrhage), or serous fluid (pulmonary edema).

If a silhouette sign is present at the superior mediastinum, which lung lobe is likely affected?

Upper lobes

If a silhouette sign is present at the right heart border, which lung lobe is likely affected?

The right middle lobe.

If a silhouette sign is present at the left heart border, which lung lobe is likely affected?

Left upper lobe or lingula

If a silhouette sign is present at the Right/left hemidiaphragm, which lung lobe is likely affected?

The Right/left lower lobe.

The CXR ranks first in the diagnostic investigation for all pathologies because the radiographic findings will

separate cardiac from pulmonary disease

may define the pathology sufficiently to begin treatment

may exclude some differential diagnoses, narrow the diagnostic choices, and thus direct the subsequent imaging evaluation

What are the four primary diagnostic categories assessed on a CXR?

Abnormally white lung field

abnormally black lung field

abnormally wide mediastinum

and an abnormally shaped heart.

Lung field is abnormally white

pneumonia, atelectasis, pleural effusion

pneumonia

A general term representing dozens of pulmonary infections arising from diverse etiologies

May involve any lobe or the entire lung, unilateral or bilateral

As the body releases white blood cells to fight infection, fluid fills up around and within the alveoli and bronchi producing the characteristic infiltrate or consolidation

Pneumonia, Radiographic Findings

A water density consolidation in one or more lobes

A silhouette sign if the consolidation is in a lobe that borders the heart or diaphragm

Air bronchogram signs due to fluid accumulation around the terminal airway vessels

Define atelectasis.

A volume loss of a portion of the lung caused by obstruction, compression, or traction.

What are three common causes of atelectasis?

Obstruction (e.g., foreign object), compression (e.g., pleural effusion), and traction (e.g., scarring/fibrosis).

Why is atelectasis a common postoperative complication?

Due to poor inspiratory efforts from pain and the retention of secretions causing obstructed airflow.

What does abnormal flattening of the diaphragm suggest?

Increased volume in the lungs.

What is a hiatal hernia?

A condition where the stomach pushes through the esophageal hiatus in the diaphragm.

Why are airway vessels usually invisible on a normal CXR?

Because their walls are thin and they are filled with air, providing no contrast against the surrounding air-filled alveoli.

What radiographic changes occur in the mediastinum and diaphragm during atelectasis?

The mediastinum shifts toward the collapsed lobe, and the hemidiaphragm elevates on the affected side.

Why does a collapsed lobe appear abnormally white on a radiograph?

The lobe is no longer filled with air, increasing its density.

What are the four types of fluid that can accumulate in a pleural effusion?

Serous fluid (hydrothorax), blood (hemothorax), chyle (chylothorax), and pus (pyothorax or empyema).

Thoracentesis

the surgical puncture of the chest wall with a needle to obtain fluid from the pleural cavity

Pleural Effusion, Radiographic Findings

blunting of the normally sharp costophrenic angles as fluid accumulates in costophrenic sulcus

blunting of posterior costophrenic angle seen on upright lateral radiograph

What is the minimum amount of fluid required to detect a pleural effusion on an upright radiograph?

At least 300ml.

Why is a lateral decubitus radiograph more sensitive for detecting pleural effusion?

It allows for the visualization of a fluid-air level, making it possible to detect as little as 50ml of fluid.

Lung field abnormally black

pneumothorax, COPD

What is the primary difference between tension and non-tension pneumothorax?

Tension pneumothorax involves ongoing air accumulation that cannot escape, creating positive pressure and mediastinal shift

whereas a non-tension pneumothorax does not have ongoing accumulation or mediastinal pressure.

What radiographic signs are associated with pneumothorax?

Affected side appears blacker

Deep sulcus signs

Mediastinum shifts away

What are the two main conditions categorized under COPD?

Emphysema (enlargement of air spaces and destruction of alveolar walls) and

chronic bronchitis (inflammation of airway walls with increased mucus).

List three radiographic findings characteristic of COPD.

Barrel Chest

Increased Radiolucency

Bullae (pockets of trapped air)

Increased vertical height of lungs

Flat (scalloped) diaphragm

Narrowed mediastinum

Airspace below the heart

Increased retrosternal airspace

bullae

air trapped in lungs

Mediastinum is abnormally wide

aortic dissection

mediastinal lymphadenopathy

What is an aortic dissection?

A tear in the inner layer of the aorta that allows blood to separate the inner and middle layers of the vessel wall.

If the outer aorta is ruptured what can happen

death

most common site of aortic dissection

ascending arorta

Type A aortic dissection

ascending aorta

Type b aortic dissection

involves descending aorta

What are the radiographic signs of an aortic dissection?

-Widened mediastinum

-Obliteration of the normal shape of the aortic arch

-Downward slant of the left mainstem bronchus due to aortic compression

-Tracheal deviation to the right due to aortic compression

-Predominant symptom is chest pain, which must be differentiated from a myocardial infarct

mediastinal lymphadenopathy

enlargement of the lymph nodes located within the mediastinum

mediastinal lymphadenopathy is a sign of

TB

Infections

Malignancies

What does mediastinal lymphadenopathy typically indicate on a CT scan?

It appears as lobulated round masses in the hilar region

Heart is abnormally shaped

- congestive heart failure (CHF)

- heart valve disease

What is the definition of Congestive Heart Failure (CHF)?

A syndrome where the heart is unable to pump out adequate amounts of blood due to weakened heart muscle or increased oxygen demand.

diseases that increase O2 demand

Hypertension

Valve disease

Thyroid disease

Kidney disease

Diabetes

Congenital heart defects

CHF, Radiologic findings

Cardiomegaly (based on the cardiothoracic ratio)

Vascular redistribution (blood vessels in the upper lobes become larger than in the lower lobes

Kerley B lines (small horizontal white lines that extend to the pleura, caused by fluid accumulated in the interlobular septa as a result of pulmonary edema

Peribronchial cuffing (bronchi seen head-on are surrounded by fluid—a sign of pulmonary edema)

Pleural effusion

Bat-wing or butterfly pattern (the replacement of lower lobe airspace with fluid produces white lung fields, leaving the air-filled upper lobes dark; the bilateral dark areas resemble wings

What are Kerley B lines in the context of CHF?

Small horizontal white lines extending to the pleura, caused by fluid accumulation in the interlobular septa due to pulmonary edema.

What is 'peribronchial cuffing' in chest radiography?

A sign of pulmonary edema where bronchi seen head-on appear surrounded by fluid.

Describe the 'bat-wing' or 'butterfly' pattern seen in CHF.

The replacement of lower lobe airspace with fluid produces white lung fields, while the air-filled upper lobes remain dark, resembling wings.

Imaging for valve dz

Ct angiography

Echocardiography

Bat-wing or butterfly pattern is seen

What is the primary diagnostic value of an echocardiogram?

It provides information on blood flow patterns, cardiac output, ejection fractions, valve function, heart wall thickness/motion, and the state of the pericardium.

What is the standard method for performing an echocardiogram?

Transthoracic echocardiography (TTE).

What is the primary difference between a standard echocardiogram and a transesophageal echocardiography (TEE)?

A standard echocardiogram uses a transducer on the chest wall, while TEE places the transducer on an endoscope inserted into the esophagus for a clearer image.

TEE requires

pulmonary fasting and sedation

What is the primary purpose of a stress echocardiography?

To compare blood flow to the heart at rest versus under stress (exercise or pharmacologic) to assess for ischemia due to coronary artery disease (CAD).

What does Doppler echocardiography measure within the heart?

It measures the velocity and direction of blood flow to assess valve function, abnormal communications, valve leaks, and cardiac output.

What is the most common indication for a V/Q scan of the lungs?

To diagnose a pulmonary embolism (PE).

In a V/Q scan, what does a result of normal ventilation with impaired perfusion indicate?

A pulmonary embolism (PE).

Normal Perfusion + impaired ventilation

Shunt

What are the four possible results of a nuclear myocardial perfusion study?

Normal perfusion, reversible defect, nonreversible defect, and a combination of defects.

What does a 'reversible defect' in a nuclear stress test indicate?

Normal perfusion at rest but decreased perfusion with exercise means some degree of blockage on one or more arteries

What does a 'nonreversible defect' in a nuclear stress test indicate?

Decreased perfusion during both rest and exercise, suggesting a complete blockage and permanent damage to the heart muscle.

What does a 'combination defect' in a nuclear stress test indicate?

Combination of reversible and non reversible defects is common in patients with coronary artery disease, since different degrees of blockages will be present in different arteries

Spect planes

short axis

horizontal and vertical long axes

SPECT Short axis

Anterior, lateral and septal images of the heart

SPECT Horizontal long axis

Septal and lateral walls + apex

Moves from anterior to inferior wall

SPECT Vertical long axis

Anterior wall+apex+inferior wall

Scan moves from Septum to lateral wall

computed tomography pulmonary angiography (CPTA)

tandard of care for diagnosis of acute PEs

V/Q vs CPTA

V/Q scanning is still indicated for those who are young, pregnant or can't have contrast

What is the gold standard for assessing the extent of narrowing and blockages in coronary arteries?

Conventional coronary angiography.

Conventional coronary angiography.

Contrast +fluoroscopy

What is considered the new gold standard for assessing heart structure and function?

Cardiac magnetic resonance (CMR) imaging.

CMR advantages

Superior imaging to echos and less invasive than Coronary angiography

What is the standard of care for the diagnosis of an acute pulmonary embolism (PE)?

Computed tomography pulmonary angiography (CTPA).

MR angiography/Cardiac MRI

group of pulse sequences that generate a high signal from flowing blood

Obesity is defined as

excessive accumulation of adipose tissue or body mass index ≥30 kg/m2

How is obesity clinically defined based on BMI?

A body mass index (BMI) of 30 kg/m2 or greater.

8 cals more a day taken in than expended over the span of 30 years can lead to

a 10 kg weight gain over 30 years