Transcript Introduction to chest radiologyr.ppt

INTRODUCTION TO
CHEST RADIOLOGY
CHI S. ZEE, M.D.
Professor OF Radiology
Director of International Education
KECK SCHOOL OF MEDICINE
Know Your Limitations Evaluate Film for Technique
1.
Inspiratory vs. Expiratory
- A good inspiration is completely through the
5th Anterior ribs.
- Expiratory films often have bibasilar
compressive changes and crowding of
vasculature which may simulate disease.
Same patient taken in forced expiration and
inspiration demonstrating compressive
changes that mimic disease
2. Rotation/Position
Clavicles Symmetric - equidistant from spinous
process.
- A-P vs. P-A chest films
Describes direction of x-ray beam and which
surface is closest to film. I.e. AP film - x-ray
from Anterior to Posterior with film behind
patient’s back. Will magnify cardiac
silhouette.
- Lordotic vs. Apical view- techniques to
visualize the apices.
- Move the patient vs. angling the x-ray beam
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same patient rotated, distorting cardiac silhouette. Note
appearance of clavicles
Expiratory vs Inspiratory images, distorts cardiac
silhouette and mimics enlargement
Lordotic positioning, Xray beam angled towards
patient’s head, projecting clavicles off chest,
paralleling ribs, obscuring lul nodule
3. Penetration
-
Should be able to see the thoracic spine
through the cardiac silhouette.
Technique for viewing bones different for
technique to visualize lung.
Images on a computer
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Dicom images on a radiology workstation
allow significant variability in image
viewing.
Few images are over or under penetrated
Develop a checklist Evaluate each system with each
film with same priority
1.
Bones
- Shoulders
- Ribs/Clavicle
- Spine
SEVERE SCOLIOSIS, OBSCURING HEART BORDER,
LUNGS ETC
HOW TO COUNT RIBS, EITHER ANTERIOR OR
POSTERIOR RIBS
Missing rib
EMPHYSEMA- SEVERE LACK OF LUNG MARKINGS,
MIMICS A PNEUMOTHORAX OR AIR IN THE
PLEURAL SPACE
2. Mediastinum
-
Heart - size, particular chamber enlargement
Trachea/Bronchi - size and positions
Aorta - course and caliber
Hila - position and size, left usually slightly
higher than right
ONE VIEW OF THE CHEST CANNOT LOCALIZE DISEASE- IF
HAVE ONLY ONE VIEW, NEED TO THINK OF ALL THE
PATHOLOGY THAT MIGHT EXIST IE DID THE BULLET HIT
THE SPINE OR THE HEART?
MASS AT RIGHT HEART BASE- DIFFERENTIAL INCLUDES
CYSTIC LESIONS, PLEURAL OR MEDIASTINAL MASSES,
LUNG MASSES.
DIAGNOSIS? PERICARDIAL CYST
AIR IN THE MEDIASTINUM- PNEUMOMEDIASTINUM
AIR UNDER THE DIAPHRAGM- PNEUMOPERITONEUM
3. Pleura
-
Effusions
Masses/Thickening
Air - pneumothorax
Sharpness of costophrenic angles
Fluid is free only if it layers on decubitus
DOES THE MASS DESTROY RIB? HAVE OBTUSE ANGLES?
SIGNS THAT IT IS GROWING INTO THE CHEST RATHER
THAN GROWING FROM THE LUNG OUTWARD
AIR IN THE PLEURAL SPACE O/W KNOWN AS A
PNUEMOTHORAX. COMPARE THIS WITH SEVERE
EMPHYSEMA
FLUID IN THE PLEURAL SPACE- CAN BE BLOOD,
WATER, PUS, TUMOR
4. Diaphragm
-
Contour - smooth, flattened
Right usually slightly higher than left
5. Abdomen
-
Organomegaly
Gas pattern - any dilatation, air-fluid levels.
Free air - pneumoperitoneum
SMALL BOWEL AIR FLUID LEVELS INDICATED
DILATATION AND OBSTRUCTION, AIR UNDER THE
RIGHT DIAPHRAGM, INDICATING PERFORATION
7. Save the best for last: LUNGS
-
Silhouette sign - 2 contiguous tissues of equal
density will obscure a normally visualized
border.
Method to localize lesions/disease
Lobar/segmental anatomy
Interstitial vs. Alveolar disease
Prior chest x-rays and history always helpful
Volumes - collapse vs. hyperexpansion
e.g. COPD
MULTIPLE LUNG NODULES- METASTATIC TESTICULAR
CARCINOMA
MASS AT RIGHT LUNG BASE WITH A FEEDING
VESSEL. THIS IS A VASCULAR STRUCTURE KNOWN
AS AN AVM (ARTERIOVENOUS MALFORMATION)
RUL INFILTRATE. DOES THE PATIENT HAVE A WHITE
COUNT AND PRODUCTIVE COUGH? FEVER?
RUL COLLAPSE- NEED TO EXCLUDE AN
OBSTRUCTING LESION
LUL COLLAPSE
RML COLLAPSE
RLL COLLAPSE
RUL COLLAPSE
Flail Chest: Communited fractures of ≥3 ribs
Blunt
Trauma
Pitfalls:
 Paradoxical
movement
clinically hard
• Older/larger
patients
• Contusion/htx
 Poor film
need  index
of suspicion
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Sharp
Outline Ptx
Computed Tomography
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X-ray
Computer
Computed tomography
With CT scanning, numerous x-ray beams and a
set of electronic x-ray detectors rotate around
you, measuring the amount of radiation being
absorbed throughout your body. At the same
time, the examination table is moving through
the scanner, so that the x-ray beam follows a
spiral path. A special computer program
processes this series of pictures, or slices of your
body, to create two-dimensional cross-sectional
images, which are then displayed on a monitor.
Computed Tomography
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Readily available modality that is first line study
for evaluation of CNS pathology.
Particularly useful in setting of trauma due to
excellent resolution of bony structures
Sensitive for parenchymal lesions, but less so
than MRI
Recent advances with multidectector CT and
post processing capabilities have expanded
diagnostic uses.
Computed Tomography
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Multidector CT is acquired using a spiral
acquisition of a volume of data, as opposed to
older generations that acquired one slice at a
time.
The number of detectors is essentially the width
of the tube that spins around the patient. Thus,
more detectors can cover a larger volume with
one rotation and reduce scan time.
Computed Tomography
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Once data is acquired, then images can
be post-processed in any imaging plane
and in any slice thickness down to the
minimum of each particular machine.
Rapid scan times have enabled
advanced imaging such as CTA and CT
perfusion to become standards.
Computed Tomography
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CT works the same as conventional x-ray, in that
it depends on the attenuation of the X-ray beam
through various different tissue densities to
generate an image.
CT assigns units, called Hounsfield units, to each
pixel on the image, based on their attenuation.
Air = -1000
Water = 0
Bone = +1000
Fat = approximately –50 to -100
Soft tissue = approximately +40 to +80
Computed Tomography
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The human eye cannot distinguish 2000 shades of gray,
so a window level and window width are assigned, thus
creating different “brain” and “bone” windows.
The level is the central HU displayed and the width
defines the scale.
If WL = 100 and WW = 200, then the gray scale will
span 0 to 200.
Any pixel above 200 will be white and any below 0 will
be black.
RISKS OF CT
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The effective radiation dose is about 2
mSv, which is about the same as the
average person receives from background
radiation in 8 months
Patient shielding
Pregnant women
Allergic reaction to contrast
Normal Chest CT Anatomy
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Coronary arteries
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Mediastinal
Hematoma
s/p R IJ
Pneumomediastinum
CTA – Active Extravasation
Bochdalek Hernia
Pulmonary Embolus
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CXR – non-specific
CONCLUSION
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Chest radiology consists of interpreting
chest X-ray and chest CT
To be familiar with normal findings
To have a basic understanding of the
common chest diseases
Thank you