3. XRAY DENSITIES
• Air – Black
• Fat – Dark gray
• Soft tissue –Light gray
• Bone – White
• Metal – Very white
4.
5. Chest X-ray Quality
• It is important to assess the quality of the image before
interpreting a chest X-ray
• Without this step you may diagnose disease that is not
genuine or you may be wrongly reassured
• Quality is influenced by radiographic technique and
patient factors
• Check the image for
• Anatomical inclusion
• Projection
• Rotation
• Inspiration and lung volume
• Penetration
• Artifact
6. ANATOMICAL INCLUSION
• Are all the necessary anatomical
structures included?
• Image quality - anatomy inclusion
• First ribs?
• Lateral edges of ribs?
• Costophrenic angles?
8. PROJECTION
• Posterior-Anterior (PA) projection
• Standard projection
• Not always possible
• Higher quality and more accurately assess heart
size than AP images
• Anterior-Posterior (AP) projection
• If the patient is too unwell to stand
• Lower quality than PA images
9.
10. AP projection :
Heart size is exaggerated because the heart is relatively farther from the detector, and also
because the X-ray beam is more divergent as the source is nearer the patient
PA projection :
The apparent heart size is nearer to the real size, as the heart is relatively nearer the detector
Magnification of the heart is also minimised by use of a narrower beam, produced by the
increased distance between the source and the patient
11. AP VS PA
• Due to AP magnification:
• Superior mediastinum appears widened
• Heart appears enlarged
• Diaphragm is higher – underinflation
• Scapulas overlap the lungs
• In the lower lung zones there appears to be a bilateral
interstitial infiltrate – also due to underinflation
12. PA VS AP
• In PA view
• Clavicles don’t project too high into the apices or
thrown above the apices (more horizontal)
• Heart wont be magnified
• Scapula are away from the lung fields
• Ribs are obliquely oriented in PA view
• Spine and posterior ends of ribs are clearly seen
13.
14.
15.
16. ROTATION
• The spinous processes of the thoracic vertebrae are in
the midline at the back of the chest
• They should form a vertical line that lies equidistant from
the medial ends of the clavicles, which are at the front of
the chest
• Rotation of the patient will lead to off-setting of the
spinous processes so they lie nearer one clavicle than
the other
• Rotation may lead to misinterpretation of heart contours,
tracheal position and lung appearances
19. • Rotation and the lungs
• Thickness of soft tissues of the chest,
such as breast tissue, is altered by rotation
• This may give the misleading impression
of pathology in the lungs
21. ROTATED FILM
Pseudo-blunting of the costophrenic angle
•At first glance the left costophrenic angle appears blunt
•The patient is rotated which results in greater thickness of breast tissue overlying
the costophrenic angle on the left compared with the right
•You may be misled into thinking there is a pleural effusion or other pathology
causing costophrenic angle blunting
22. INSPIRATION AND LUNG VOLUME
• Chest X-rays are conventionally acquired in the
inspiratory phase of the respiratory cycle
• The radiographer asks the patient to, breathe in and hold
his breath
• If the image is acquired in the expiratory phase
• Lungs Relatively airless
• Lung density Increased
• Position of the diaphragm Raised
• Exaggeration of heart size
• Obscuration of the lung bases
23. • Assessing inspiration
• Count ribs down to the diaphragm
• The diaphragm should be intersected by the 5th to 7th
anterior ribs in the mid-clavicular line
• Less is a sign of incomplete inspiration
• Assessing for hyperexpansion
• >7th anterior rib intersecting the diaphragm at the mid-
clavicular line
• Sign of obstructive airways disease
• Flattening of the hemidiaphragms
24. INSPIRATORY FILM
•Anteriorly the fifth rib intersects the diaphragm at the mid-clavicular line
•The lungs are not consolidated
•The heart size is clearly normal
25. EXPIRATORY FILM
• Anteriorly only the third rib intersects the diaphragm at the mid-clavicular line
• The lung bases are white
• Heart size is increased
26.
27. NORMAL EXPANSION
•This patient has taken a good breath in such that the diaphragm is intersected by
the 6th rib in the mid-clavicular line
•The hover over image shows an imaginary dotted line between the costophrenic
and cardiophrenic angles
•The distance between this line and the diaphragm (green lines) should be
greater than 1.5 cm (asterisk) in normal individuals
28. HYPEREXPANSION
• >7th anterior rib intersecting the diaphragm at the mid-clavicular line
• Flattening of the hemidiaphragms
29. PENETRATION
• Penetration is the degree to which X-rays have passed
through the body
• A well penetrated chest X-ray is one where the vertebrae
are just visible behind the heart
• The left hemidiaphragm should be visible to the edge of
the spine
• Digital correction may compensate for an incorrectly
penetrated X-ray
• Loss of the hemidiaphragm contour or of the
paravertebral tissue lines may be due to lung or
mediastinal pathology
30. • Under penetration
• The left hemidiaphragm is not visible to the spine
• Lung tissue behind the heart cannot be assessed
• Re-windowing (hover over image)
• The diaphragm (long arrows) is visible to the spine
• The left paravertebral soft tissues are visible (short arrows) ,right side of the spine is
clear (arrowheads)
• There is no abnormality of lung tissue behind the heart
33. ARTIFACT
• Artifactual appearances seen on a chest X-ray may be due to
radiographic technique, patient factors, or the presence of
external or internal non-anatomical objects
• Radiographic artifact
• This is spurious or unclear appearance of an anatomical
structure due to radiographic technique
• Examples :
• Rotation, incomplete inspiration and incorrect penetration
• Clothing or jewellery not removed
• Patient artifact
• Examples:
• Poor co-operation with positioning or movement
• Very often obesity exaggerates lung density
• Occasionally normal anatomical structures such as hair or skin
folds can cause confusion
36. HAIR ARTIFACT
• At first glance the soft tissues at the base of the neck on the right look abnormal
• Appearances simulate surgical emphysema
• This artifact is due to hair which was draped around the patient's neck
37. • Medical/surgical artifact
• Some chest X-rays are performed solely to
assess the position of medical devices
• External medical devices not part of the X-ray
assessment should be removed by
radiographers prior to image acquisition, unless
it is dangerous to do so
38. Naso-gastric (NG) tube placement
•Clinicians are often required to check the position of a naso-gastric tube
•The tube tip should be below the level of the diaphragm (dotted line), and ideally
should be at least 10cm beyond the gastro-oesophageal junction (asterisk)
•This tube is only just in the stomach and so was advanced and the position
rechecked prior to using it for feeding
•The tip of a naso-gastric tube should also lie on the left
•If it crosses the midline it has entered the duodenum
