in this tutorial i am speaking about chest x-ray quality that include : 1- Inclusion 2- inspiration/lung 3- volume 4- projection 5- penetration 6- Rotation 7- artifact i try to make it easy and simple for medical students and junior doctors to help them in clinical life.

1. Chest x-ray
How To Interpret Chest x-ray
By
Yusuf Shieba
Specialist of cardiothoracic surgery

2. Chest X-ray (CXR), or chest film, is radiograph of
the chest used to diagnose conditions affecting
the chest, its contents, and nearby structures.
Chest radiographs are the most common film
taken in medicine.
Chest radiography employs ionizing radiation in the
form of X-rays to generate images of the chest.
Chest radiographs
• Simple ( just black and white film )
• Low cost
• Sensitive
• Excellent resolution

3. Chest X-ray Quality
Inclusion inspiration/lung volume projection
penetration Rotation artifact
Steps For Optimal Chest x-ray
• Accurate patient positioning
• Tube – film distance
• Full inspiration
• Adequate penetration
Inclusion
A chest X-ray should include the entire thoracic cage. Occasionally, important anatomical structures
are not included. If the clinical question can still be answered then acquiring another image is
not always necessary.
Image quality - anatomy inclusion
• First ribs?
• Costophrenic angles?
• Lateral edges of ribs?

4. Projection
Posterior-Anterior (PA) projection
The standard chest radiograph is acquired with the patient standing up, and with the X-ray beam passing through the patient
from Posterior to Anterior (PA).
The chest X-ray image produced is viewed as if looking at the patient from the front, face-to-face. The heart is on the right
side of the image as you look at it.

5. Anterior-Posterior (AP) projection
Sometimes it is not possible for radiographers to acquire a PA chest X-ray. This is usually because the patient is too
unwell to stand.
The chest X-ray image is still viewed as if looking at the patient face-to-face.
AP v PA - Heart size
The heart, being an anterior structure within the chest, is magnified by an AP view. Magnification is exaggerated
further by the shorter distance between the X-ray source and the patient, often required when acquiring an AP
image. This leads to a more divergent beam to cover the same anatomical field.
As a rule of thumb, you should never consider the heart size to be enlarged if the projection used is AP. If however
the heart size is normal on an AP view, then you can say it is not enlarged.

6. The 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.
The 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.

7. AP v PA - Scapular edges
Radiographers will often label a chest X-ray as either PA or AP. If the image is not labelled, it is
usually fair to assume it is a standard PA view. If, however, you are not sure, then look at
the medial edges of each scapula.
AP projection - example
• AP projection images are of lower quality than
PA images. Compare this image with the PA view
below.
• The image has been acquired by a mobile X-ray
unit in the resuscitation room. Note the AP
SITTING label.
• The scapulae are not retracted laterally and they
remain projected over each lung.
• Heart size is exaggerated (cardiothoracic ratio
approximately 50%).

8. In order to take a PA view the patient places his or her arms around the side of the
detector plate, or stands with hands on hips. This ensures the scapulae are rotated
laterally and no longer overlap the lungs.
PA projection - example
This PA X-ray is of the same patient as the image
above.
The edges of the scapulae are retracted laterally
with only a small portion projected over each
lung. The lungs are therefore more easily seen.
The cardiothoracic ratio is clearly well within the
normal limit of 50%.

9. Rotation
If the patient is very rotated and you do not recognise this, certain appearances may become
misleading.
Principles of 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.
Well-aligned PA chest X-ray
• Find the medial ends of the clavicles
• Find the vertebral spinous processes
• The spinous processes should lie half way between the
medial ends of the clavicles

10. Does rotation matter?
If the patient is rotated then interpretation may become difficult. Firstly, it may be difficult to
know if the trachea is deviated to one side by a disease process. It also becomes difficult to
comment accurately on the heart size. Changes in lung density due to asymmetry of
overlying soft-tissue may be incorrectly interpreted as lung disease.
Rotation and heart size
Heart size can be assessed accurately with a well-aligned posterior-anterior (PA) chest X-ray. If
the patient is rotated to the left the heart may appear enlarged and if rotated to the right its
size may be underestimated.
Well-aligned patient
An accurate assessment
can be made

11. Rotated patient - Left
Heart size is exaggerated
Rotated patient - Right
The true size of the heart may be
underestimated

12. 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
your breath!' Patients who are short of breath, or those who are unable to
follow the instructions may find this difficult.
When interpreting a chest X-ray it is important to recognise if there has been
incomplete inspiration. If the image is acquired in the expiratory phase, the
lungs are relatively airless and their density is increased. Also, the raised
position of the diaphragm leads to exaggeration of heart size, and obscuration
of the lung bases.
Assessing inspiration
To assess the degree of inspiration it is conventional to 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.

13. Expiration
• (Same patient as next image)
• Anteriorly only the third rib intersects the
diaphragm at the mid-clavicular line
• The lung bases are white - Is there
consolidation?
• How big is the heart.
Inspiration
• (Same patient as previous image)
• Anteriorly the sixth rib intersects the diaphragm
at the mid-clavicular line
• The lungs are not consolidated
• The heart size is clearly normal

14. Assessing for hyperexpansion
While checking for adequate inspiration you may notice that a patient's lungs are hyperexpanded
(>7th anterior rib intersecting the diaphragm at the mid-clavicular line). This is a sign of
obstructive airways disease.
It is possible to assess for hyperexpansion by counting ribs, or by checking for flattening of the
hemidiaphragms.
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 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. In practice this is rarely
measured and a quick assessment of diaphragm shape is all
that is necessary.

15. Hyperexpansion
• It is often quicker to assess for hyperexpansion
by looking at the hemidiaphragms. These are
clearly flattened in this patient.
• The ribs are difficult to count as they have lost
density. This is due to long term steroid treatment
for the patient's emphysema.
• There is also consolidation of the lung bases due
to pneumonia.

16. Penetration
Penetration is the degree to which X-rays have passed through the body. Assessment of
penetration is traditionally a standard part of assuring chest X-ray quality. With modern
digital systems over or under penetrated/exposed images are rarely a problem. Image data
can be 'windowed' to optimise visibility of anatomical structures. This is often performed by
radiographers after they have acquired the image or can be performed using imaging
software on the wards.
A well penetrated chest X-ray is one where the vertebrae are just visible behind the heart.
Although X-rays are still occasionally over or under exposed, a discussion of penetration now
best serves as a reminder to check behind the heart. The left hemidiaphragm should be
visible to the edge of the spine. Loss of the hemidiaphragm contour or of the paravertebral
tissue lines may be due to lung or mediastinal pathology.

17. Under penetration
• The left hemidiaphragm is not visible to the
spine
• Lung tissue behind the heart cannot be assessed
• Re-windowing the image using digital software
can compensate
• The diaphragm (long arrows) is visible to the
spine.
• The left paravertebral soft tissues are visible
(short arrows) , and the right side of the spine is
clear (arrowheads).
• There is no abnormality of lung tissue behind
the heart.

18. Artifact
Key points
• Some artifacts are unavoidable
• A chest X-ray may be obtained to assess position of medical devices
• Ask yourself if artifact limits image interpretation
• Can the question clinical question still be answered.
Radiographic artifact
This is spurious or unclear appearance of an anatomical structure due to radiographic technique.
As previously discussed, examples include rotation, incomplete inspiration and incorrect
penetration. Other radiographic artifact includes clothing or jewellery not removed.
Patient artifact
Artifact may be due to patient factors such as 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.

20. 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.
Medical/surgical artifact
Some chest X-rays are performed to assess the position of medical devices. It is a common task of a
junior doctor to be asked to assess the position of such devices on a chest X-ray.

21. Naso-gastric (NG) tube placement
• Junior doctors 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. A tube in this position is correctly
termed a naso-enteric tube.

22. Chest X-ray Quality
Tutorial conclusion
• Complete assessment of a chest X-ray requires consideration of image quality. This involves
inclusion, projection, rotation, inspiration/lung volume, penetration and artifact.
• A poor quality chest X-ray does not always need to be repeated. You should see if the clinical
question can be answered and only request a repeat if the patient is likely to benefit.
• You should assess the entire image even if is quickly seen to be less than perfect. Many
technically sub-optimal chest X-rays show life-threatening abnormalities that require urgent
action!

23. Hand mit Ringen (Hand with Rings): print
of Wilhelm Röntgen's first "medical" X-ray, of his
wife's hand, taken on 22 December 1895 and
presented to Ludwig Zehnderof the Physik
Institut, University of Freiburg, on 1 January 1896