you can think of x-rays as photos made
from high-energy photons that penetrate
the body tissues so that we can see
what's going on inside just like visible
light x-rays are less likely to
penetrate denser materials conventional
x-rays that show white bones on a black
background are like photographic
negatives the darkest parts of the film
like the lungs are areas where more
photons can penetrate the body
in contrast the sharp bright white areas
are where the dense bone material blocks
photons from getting through let's go
through this chest x-ray using an
easy-to-remember checklist associated
with the first seven letters of the
alphabet abcdefg
a stands for assessment to avoid errors
and wasted time you should always begin
by assessing the patient and exam data
you want to verify the patient's data
with the exam data or the medical record
number date of the exam etc to ensure
that you are looking at the right study
in patient you also need to assess image
quality because this will impact the
accuracy of the test in detecting
pathology for example to ensure there is
an excess rotation of the patient you
should make sure that the medial ends of
the spinous processes are equally
distant from the border of the vertebral
bodies rotation throws off the usual
x-ray anatomy and introduces unwanted
variation next a good inspiration film
should show at least the 10th or 11th
posterior ribs if the lungs are not
fully expanded we might miss important
diseases finally we need to make sure
that the exposure isn't too bright or
too dark to check for this you can look
for fine markings in the lung fields to
make sure they're visible if the fine
lung markings aren't visible then the
x-ray may fail to detect some diseases a
also reminds us to make sure there is an
air where it shouldn't be
finding air where it should not be or
more commonly ruling it out remains one
of the most important uses of medical
x-rays diagnoses like pneumothorax
pneumomediastinum pneumoperitoneum and
subcutaneous emphysema are all examples
of air where it shouldn't be
all of these are surgical emergencies
and can be diagnosed by a simple chest
x-ray
finally if the major Airways like the
trachea are bent or deviated another
example of air where it shouldn't be it
may signal an underlying mass B is for
bones start by looking at both clavicles
and all twelve pairs of ribs one at a
time to make sure that there are no
fractures deformities or missing bones B
is also for the body wall and soft
tissues outside of the chest this is an
easily overlooked part of the chest
x-ray and it should be checked for
swelling masses and other things
see is for cardiac silhouette and size
this is the cardiac silhouette and
there's an atrial appendage the right
atrium and the left ventricle
remember in chest x-rays we define
features relative to the patient so the
right atrium is on the left side of this
x-ray and the left ventricle is on the
right side measuring across a normal
heart is less than 50% of the greatest
diameter of the ribcage measured from
the inner portion of each rib any larger
and there may be cardiac pathology d is
for the diaphragms which shouldn't be
too flat but appear fairly symmetric you
can assess flatness on the lateral view
by estimating that the hemidiaphragm is
1.5 centimeters above the line
connecting the costophrenic angle
posteriorly and sterno phrenic angle
anteriorly e is for equipment such as
lines tubes and wires involved in life
support it's important to note exactly
where they're located relative to other
structures and whether they're in
functional position for example an
endotracheal tube should be in the
middle of the trachea and its tip should
be more than 2 centimeters from the
tracheal bifurcation or that a
nasogastric tube should have its tip
well within the stomach he is also a
reminder to check for a pleural effusion
which is a common but subtle form of
pathology that you can see on an x-ray
pleural effusions are fluid that
collects at the costophrenic angle and
causes blunting of the normally sharp
costophrenic angle F is for lung fields
which should look symmetric there
shouldn't be any haziness white dots or
blotches while looking at lung fields
having a frontal and a lateral x-ray
allows us to determine in which lobe of
which lung and abnormality is located in
this case a nodular mass is visible in
the inferior lateral and anterior left
lung meaning it's most likely within the
and remedial basal sub segment of the
lower left lobe this can be confirmed
with the chest CT
lastly G is for great
vessels which includes the superior vena
cava inferior vena cava ascending aorta
aortic arch pulmonary artery and
descending aorta you want to make sure
that all of these structures are in the
right location and is the right size on
the left side of the heart the aortic
arch should be the highest up followed
by the pulmonary artery of note since
the heart is three-dimensional the
atrial appendage actually sits behind
the central formation in frontal x-ray
on the right side the superior vena cava
ascending aorta right ventricle left
ventricle and inferior vena cava should
all be visible deviation may be the
result of congenital abnormality or
disease okay to recap using ABCD efg a
is for the assessment of data and
quality as well as looking for air where
it should not be B is for bones in the
body wall C is for cardiac silhouette
and size D is for diaphragms E is for
equipment and diffusions F is for lung
fields and G is for great vessels
you