Introduction to Radiographic Interpretation Special Emphasis on CXRs.

Introduction to Radiographic InterpretationSpecial 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 BoneMetal

least opaque to most opaquemost lucent to least lucentBlack to White

Radiographic Opacities & Contrasts

Air Air

Fat Mineral oil

Water Water

Bone Tums

Metal ???

Five Radiographic Opacities

Standard Radiographic Positions

Standard Radiographic Directions

As seen when viewing

DorsalProximalCranial

VentralDistalCaudal

CranialRostralDorsalRight

CaudalPalmarPlantarLeft

Lateral view Cranial-caudal view

Radiograph: two-dimensional image of a three-dimensional object

So . . . What is it?

Dorsoventral view

Radiograph: two-dimensional image of a three-dimensional object

So . . . What is it?

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: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

CXR InterpretationHave 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– Mediastinum & heart– Lung (single)– Lungs (both)

CXR InterpretationHave 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– Mediastinum & heart– Lung (single)– Lungs (both)

A

T

M

L L

CXR InterpretationBeware 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 InterpretationBeware the poor-quality film: Inspiration

CXR InterpretationNormal structures visible

1. Tracheal air column. 2. Carina. 3. First rib.4. Peripheral lung fields have no markings except: 5. The minor fissure. 6. Top of the R diaphragm is usually between the

anterior 6th & 7th ribs, and overlying the posterior 10th & 11th ribs.

7. Left diaphragm is lower (in 90-95%) by roughly half an interspace.

8. Inferior margins of the posterior ribs.9. Anterior mediastinal line.10. Superior vena cava.11. Azygous vein.12. Right descending pulmonary artery. 13. Pulmonary arteries and veins. 14. Right atrium. 15. Inferior vena cava. 16. Aortic arch. 17. Left pulmonary artery. 18. Border of the left ventricle. 19. Descending aorta. 20. Fat density lines in the intermuscular fascial

layers


A. Costophrenic angleB. DiaphragmC. HeartD. Aortic archE. TracheaF. HilumG. Main carinaH. Stomach bubbleI. Ascending aorta


1. Tracheal air column. 2. Carina. 3. First rib.4. Peripheral lung fields have no markings except: 5. The minor fissure. 6. Top of the R diaphragm is usually between the

anterior 6th & 7th ribs, and overlying the posterior 10th & 11th ribs.

7. Left diaphragm is lower (in 90-95%) by roughly half an interspace.

8. Inferior margins of the posterior ribs.9. Anterior mediastinal line.10. Superior vena cava.11. Azygous vein.12. Right descending pulmonary artery. 13. Pulmonary arteries and veins. 14. Right atrium. 15. Inferior vena cava. 16. Aortic arch. 17. Left pulmonary artery. 18. Border of the left ventricle. 19. Descending aorta. 20. Fat density lines in the intermuscular fascial

layers

CXR InterpretationPA vs. AP views

CXR InterpretationPA & Lateral views

CXR InterpretationHyperexpansion = “Air Trapping”

CXR Interpretation“Big Lungs” & “Little Lungs”

CXR InterpretationInterstitial Infiltrates

A. Generalized interstitial thickening = linear (“reticular”).

B. Discrete interstitial thickening = nodules.

C. Interstitial & alveolar filling = silhouette.

CXR InterpretationInterstitial Infiltrates

CXR InterpretationAlveolar Infiltrates

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

CXR InterpretationAlveolar Infiltrates

Introduction to Radiographic Interpretation Special Emphasis on CXRs.

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