Chest RadiologyPart 1:

The Normal Chest X-Ray

Omar M. Albustami, MD.Pulmonary Disease and Critical Care Medicine Fellow.

Brody School of Medicine.East Carolina University.

July 06, 2010

MS3 Medicine Core Conference

Outline

Section A:How to look at a CXR

Basic interpretation is easyTechnical quality Scanning the PA filmHow to look at the lateral film.

Section B:Localizing lesions

LungsHeart

Ground rules that must be applied when interpreting the CXR.

CXR

• Powerful investigation mass of info about the cardioresp disease.

• Easily available.

• Cheap.

• Safe.

• Value depends on the quality of the clinician viewing the film.

Section A: How to look at a CXRBasic interpretation is easy

• Adopt the following procedure:– Name & date.– Technical quality.– Scan & mentally list any abnormalities. Do not stop

when you find the first abnormality.– If abnormalities are found, work out where they are.– Mentally describe the abnormality. Which category

does it fall into:• Too white.• Too black.• Too large.• In the wrong place.

Technical quality

PA AP

Technical quality

• Always check the technical quality of any film before interpreting it further.

• Examine:– Projection.– Orientation.– Rotation.– Penetration.– Degree of inspiration.

Technical qualityProjection: defined by the direction of the x-ray beam in

relation to the pt.

Portable (AP or Antero-posterior) PA (Postero-anterior)

Technical qualityOrientation

• Check the left/right markings (can be wrong).

• Do not assume the heart is always on the left:– Dextrocardia.– The mediastinum can be pushed or pulled to the right

by lung pathology.

Technical qualityRotation

• Medial ends of the clavicles should be equidistant from the spinous process.

• If one clavicle is nearer than the other pt is rotated the lung on that side will appear whiter.

Technical qualityPenetration

• Look at the lower part of the cardiac shadow.

• The vertebral bodies should only just be visible through the cardiac shadow at this point.

• Too clearly visible: film is over penetrated may miss low density lesions.

• Cannot see them: under penetrated lung fields will appear falsely white.

• When comparing x-rays, the level of penetration should be taken into consideration.

Technical quality Degree of inspiration

• Count the number of ribs above the diaphragm.

• Midpoint of the right hemidiaphragm should be between 5th -7th ribs anteriorly.

• Anterior end of 6th rib• Post end of 10th rib

• Poor inspiration will:– make the heart look larger, – give the appearance of basal shadowing & – cause the trachea to appear deviated to the right.

should be above the diaphragm.

Scanning the PA film

• Find a decent viewing box with a functioning light that does not flicker.

• Lower the ambient light.

• Survey the x-ray from a distance (4 feet) then close up.

• Check list:– Lung fields.– Hilum.– Heart.– Rest of mediastinum.– Diaphragms & costophrenic angles.– Trachea.– Bones.– Soft tisuues.

Anatomy

Check list

– Lung fields: • Equal transradiancy.• Horizontal fissure: should run from hilum to 6th rib in the axillary line.• Any discrete or generalized shadows.

– Hilum: Left should be higher than right (< 1 inch difference): should be concave in shape and have similar density.

– Heart:• Shape.• Diameter: <50% transthoracic diameter.• Margins should be sharp.• Dense areas.

– Rest of mediastinum: Edge should be clear though some fuzziness is acceptable at the angle between heart & diaphragm, apices & Rt hilum.

– Trachea:• Should be central but deviates slightly to the right around the aortic

knuckle.• Right side white edge width <2-3 mm on an erect film.

Check list…cont’d.

– Diaphragms & costophrenic angles:• Right diaphragm is higher than left (< 1.2 inch difference).• Outline should be smooth.• Costophrenic angles: Well defined & acute.

– Bones:• Density. • Compare both sided.• Areas of blackness.

– Soft tisuues: • Enlargment. • Gas.

How to look at the lateral film

• Name & date.

• Step back.

• Identify diaphragms:

– 1: right hemidiaphragm: can be seen to stretch across the whole thorax & clearly seen passing through the heart border.

– 2: left hemidiaphragm: seems to disappear when it reaches the post border of the heart.

– Costophrenic angles.

• 3: Gastric air bubble.

How to look at the lateral film

• Lung fields: – compare appearance in front of &

above heart to those behind (equal density).

– Discrete lesions.

• 4: Retrosternal space: ? Ant mass.

• 5: Horizontal fissure: faint white line passing horizontally from the midpoint of the hilum to the ant chest wall.

• 6: Oblique fissure: T4/T5 vertebrae, through the hilum, ending at the ant third of the diaphragm.

• 7: Hila.

• Vertebral bodies: – all same shape & size.– Density: get more translucent

(darker) caudally.

Section B:Localizing lesions: Lungs

To accurately localize a lesion on CXR, we need to look at both the PA & lateral films.

PA film:

•Horizontal fissure.

•Borders of the lesion: if the lesion is next to a dense (white) structure, the border will be lost silhouette sign.

•RML lesion obscures part of the heart border.

•RLL lesion obscures the border of the diaphragm.

Lateral film: Right Sided Fissures

RUL

RML

RLL

Lateral film: Left Side Fissure

LUL

LLL

Localizing lesions: Heart

• PA film: • Right heart border up from the diaphragm:

– Edge of right atrium.– Above the hilum: SVC.

• Left heart border up from the diaphragm:– Left ventricle.– Concavity: left atrial appendage.– At the level of the hilum: pulmonary artery.– Aortic knuckle.

Cardiac Silhouette

1. R Atrium2. R Ventricle3. Apex of L Ventricle

4. Superior Vena Cava5. Inferior Vena Cava6. Tricuspid Valve

7. Pulmonary Valve8. Pulmonary Trunk9. R PA 10. L PA

Lateral film: Heart

Post border:

Left ventricle.

Ant border:

Right ventricle.

Location of cardiac valves is best determined on

the lateral CXR. • Draw an imaginary line from the

apex of the heart to the hilum.

• The pulmonic & aortic valves generally sit above this line and the tricuspid & mitral valves sit below.

Thank you.