Introduction to Radiographic Interpretation Special Emphasis on CXRs

Differential Absorption of X-rays Dependent upon Physical density Atomic number Thickness Determine the gray scale of the radiograph Absorb few x-rays = film black many x-rays = film white

Five Radiographic Opacities Air Fat Soft tissue Bone Metal least opaque to most opaque most lucent to least lucent Black to White

Radiographic Opacities & Contrasts Air Air Fat Mineral oil Water Water Bone Tums Metal ???

Five Radiographic Opacities

Five Radiographic Opacities

Standard Radiographic Positions

Standard Radiographic Positions

Standard Radiographic Directions As seen when viewing Dorsal Proximal Cranial Cranial Rostral Dorsal Right Caudal Palmar Plantar Left Ventral Distal Caudal

Radiograph: two-dimensional image of a three-dimensional object So . . . What is it? Lateral view Cranial-caudal view

Radiograph: two-dimensional image of a three-dimensional object So . . . What is it? Dorsoventral view

Interpretation Challenges Magnification Distortion Image of a familiar object is unfamiliar Loss of depth perception Summation Silhouette effect

Interpretation Challenges: Magnification Enlargement of the radiographic image of an object relative to its actual size Increased film-subject distance

Interpretation Challenges: Magnification

Interpretation Challenges: Magnification

Interpretation Challenges: Distortion Distortion:Misrepresentation of the true shape of an object

Interpretation Challenges: Unfamiliar image of a familiar object

Interpretation Challenges: Depth perception

Interpretation Challenges: Summation Superimposition of structures in different planes Resultant image = summation of opacities

Interpretation Challenges: Summation

Interpretation Challenges: Silhouette Effect Two structures of the same radiopacity in contact – their margins cannot be identified

Interpretation Challenges: Silhouette Effect

Interpretation Challenges: Silhouette Effect

CXR Interpretation Have a system!! Method 1: “Outside-to-inside” Soft tissues Bony framework Lungs & hila Diaphragm & pleura Mediastinum & heart Method 2: “Are There Many Lung Lesions?” Abdomen & diaphragm Thorax Lung (single) Lungs (both)

CXR Interpretation Have a system!! Method 1: “Outside-to-inside” Soft tissues Bony framework Lungs & hila Diaphragm & pleura Mediastinum & heart Method 2: “Are There Many Lung Lesions?” Abdomen & diaphragm Thorax Lung (single) Lungs (both) T L L M A

CXR Interpretation Beware the poor-quality film!! Poor inspiration High diaphragms, crowded lung markings “Penetration”: Disappearing thoracic vertebral details through the heart. Rotation: Note equal distances from the vertebral spines to the medial ends of the clavicles.

CXR Interpretation Beware the poor-quality film: Inspiration

CXR Interpretation Normal structures visible Tracheal air column. Carina. First rib. Peripheral lung fields have no markings except: The minor fissure. Top of the R diaphragm is usually between the anterior 6th & 7th ribs, and overlying the posterior 10th & 11th ribs. Left diaphragm is lower (in 90-95%) by roughly half an interspace. Inferior margins of the posterior ribs. Anterior mediastinal line. Superior vena cava. Azygous vein. Right descending pulmonary artery. Pulmonary arteries and veins. Right atrium. Inferior vena cava. Aortic arch. Left pulmonary artery. Border of the left ventricle. Descending aorta. Fat density lines in the intermuscular fascial layers

CXR Interpretation Normal structures visible Costophrenic angle Diaphragm Heart Aortic arch Trachea Hilum Main carina Stomach bubble Ascending aorta

CXR Interpretation Normal structures visible Costophrenic angle Diaphragm Heart Aortic arch Trachea Hilum Main carina Stomach bubble Ascending aorta

CXR Interpretation Normal structures visible Tracheal air column. Carina. First rib. Peripheral lung fields have no markings except: The minor fissure. Top of the R diaphragm is usually between the anterior 6th & 7th ribs, and overlying the posterior 10th & 11th ribs. Left diaphragm is lower (in 90-95%) by roughly half an interspace. Inferior margins of the posterior ribs. Anterior mediastinal line. Superior vena cava. Azygous vein. Right descending pulmonary artery. Pulmonary arteries and veins. Right atrium. Inferior vena cava. Aortic arch. Left pulmonary artery. Border of the left ventricle. Descending aorta. Fat density lines in the intermuscular fascial layers

CXR Interpretation PA vs. AP views

CXR Interpretation PA & Lateral views

CXR Interpretation Hyperexpansion = “Air Trapping”

CXR Interpretation “Big Lungs” & “Little Lungs”

CXR Interpretation Interstitial Infiltrates Generalized interstitial thickening = linear (“reticular”). Discrete interstitial thickening = nodules. Interstitial & alveolar filling = silhouette.

CXR Interpretation Interstitial Infiltrates

CXR Interpretation Interstitial Infiltrates

CXR Interpretation Alveolar Infiltrates Alveolar-filling, or “airspace” disease: “Pointillist” patterns. Air bronchograms.

CXR Interpretation Alveolar Infiltrates