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

Expiration 4 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?

WHAT’S MISSING ? The Rt. Shoulder!