CHEST INTRODUCTION
Technical Adequacy
In trying to determine if pathology is present in a chest radiograph
several factors have to be considered in the overall judgment of the
radiograph to determine if the visual findings are pathologic or in
part are related to the radiograph itself.
Factors to be considered on all chest x-rays include:
Inspiration
Penetration
Rotation
Angulation
Orientation
• Inspiration: The volume of air in the hemithorax
will affect the configuration of the heart with
question of cardiac enlargement with a shallow
level of inspiration. The vascular pattern in the
lung fields will be accentuated with a shallow
inspiration since the same amount of blood flow is
now distributed to a smaller volume of lung.
• The level of inspiration can be estimated by
counting ribs. Visualization of nine posterior ribs,
or seven anterior ribs on an upright PA radiograph
projecting above the diaphragm would indicate a
satisfactory inspiration.
Inspiration
Expiration
Inspiration
4
Expiration
NOTE CHANGE IN HEART SIZE AND
VASCULARITY DUE TO EXPIRATION.
• Penetration: Refers to adequate photons traversing
the patient to expose the radiograph. This is often
limited in patients of large size such that there is
poor visualization of structures in the lower lung
fields and in a retro-cardiac location. The lack of
penetration renders the area “whiter” than with an
adequate film and can simulate pneumonia or
effusion. In an ideal radiograph the thoracic spine
should be barely perceptual viewing through the
cardiac silhouette. The soft tissues at the shoulder
can also give an estimate of the relative degree of
penetration of the film.
Penetration
CASE #1
IS THE DIFFERENCE DUE TO CHF OR PENETRATION?
Penetration
CASE #2
DID YOU SEE THE NODULE ON
THE PREVIOUS FILM?
• Rotation of the patient distorts mediastinal anatomy
and makes assessment of cardiac chambers and the
hilar structures especially difficult. Chest wall
tissue also contributes to increased density over the
lower lobe fields simulating disease. Rotation of the
radiograph is assessed by judging the position of the
clavicle heads and the thoracic spinous process.
Ideally the clavicle heads should be equidistant from
the spinous process.
Rotation
DISTORTED MEDIASTINUM DUE
TO TORTOUS AORTA AND
ROTATION.
• Orientation: In this we are making reference to the position
of the patient and the xray beam. A PA radiograph is
obtained with the x-ray traversing the patient from posterior
to anterior and striking the film. Similarly an AP radiograph
is positioned with the xray traversing the patient from
anterior to posterior striking the film. The cardiac border or
silhouette will appear larger on an AP radiograph due to the
magnification effect of the more anteriorly located heart
relative to the film.
• Typically portable radiographs are obtained AP, as the
patient is not able to stand. Standing radiographs in the
department are typically obtained PA with a corresponding
lateral radiograph. The PA and lateral radiograph best
demonstrate the actual cardiac size with minimal
magnification compared to the AP exam.
Orientation
PA
AP
PA
AP
• Angulation: With the patient in a more
lordotic projection the clavicles will project
superiorly relative to the upper thorax again
causing some distortion of the normal
mediastinal anatomy. With the lordotic
projection of the ribs assume a more
horizontal orientation. Occasionally a lordotic
xray can be obtained intentionally to better
visualize structures in the thoracic apex
obscured by overlying boney structures.
Angulation
PA
AP LORDOTIC
EXAMPLE OF
GOOD
INSPIRATION
PENETRATION
ROTATION
ORIENTATION
ANGULATION
WAS THIS FILM TAKEN
IN THE UPRIGHT
POSITION?
The Rt. Shoulder!
WHAT’S MISSING ?