PHTY208 Lecture Notes - Lecture 14: Sternum, Clavicle, Heart
Introduction to CXR
• Why do we take chest x-rays
o To assess pathology of the thorax
• Lungs
• Heart e.g. enlarged heart
• Pleura e.g. inflammation
• Bones e.g. fractures
o To check for correct placement of tubes and lines (e.g. endotracheal, tracheostomy,
CVP, ICC, etc).
• Physics of x-rays
o X‐rays ‐ioisig eletroageti radiatio
o High frequency
o Short wavelength
o X‐rays travel i straight lies ad a ea of X‐rays diverges fro its soure.
o X‐rays are asored y ody tissues aordig to desity ad thikess of those
tissues
o Structures the beam hits first will be magnified in relation to those which are nearer
the detector (plate)
o Structures that need to be measured accurately should be placed closer to the
detector (plate)
o X rays pass through air and are absorbed by more dense structures
o The more dense the structure the whiter it is
• Structures that are white
o Bone
o Heart
o Diaphragm
o Blood vessels
o Lymphatics
o Artificial devices
• Soft tissue
o Male and Female breast shadows
o Presence of gas (Sx emphysema) or calcification
o Skin folds and muscle
o Trachea
• Midline or deviated
• Bifurcates at about T5, some of each main bronchus visible
o Diaphragm
• Diaphragmatic hernia
• Shape
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• Heart and mediastinum
o Size
o Position
o Outline
o If the edges of the heart shadow are not clear and sharp it is a clear indicator of
disease in the surrounding lung tissue since lung tissue should be air density not
water density
• This is called the SILHOUETTE sign
o Mediastinum
• Midline position
• Hilum
o The hilum is the area where the major bronchi and pulmonary vessels and lymph
nodes JOIN the lung
o Pulmonary arteries and veins, major bronchi, and lymph nodes.
o It appears as a water density on either side of the mediastinum.
o Left usually higher than right
• Lymphatics and blood vessels
o Kerley B lines
o Aorta
o Pulmonary artery
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Document Summary
Introduction to cxr: why do we take chest x-rays, to assess pathology of the thorax. Lungs: heart e. g. enlarged heart, pleura e. g. inflammation, bones e. g. fractures, to check for correct placement of tubes and lines (e. g. endotracheal, tracheostomy, Structures that are white: bone, heart, diaphragm, blood vessels, lymphatics, artificial devices. Soft tissue: male and female breast shadows, presence of gas (sx emphysema) or calcification, skin folds and muscle, trachea, midline or deviated, bifurcates at about t5, some of each main bronchus visible, diaphragm, diaphragmatic hernia. Shape: heart and mediastinum, size, position, outline. It appears as a water density on either side of the mediastinum: left usually higher than right. Lymphatics and blood vessels: kerley b lines, aorta, pulmonary artery. Silhouettes: two densities which are superimposed so you can"t see outline clearly. Left: deformed chest from polio, difficulty to determine location of lungs, trachea is distorted. Large hump - severe kypho-scoliosis: right, newborn, ribs horizontal - normal.
