CHEST RADIOGRAPHS, A WAYANG KULITPart Three

Second Edition February 2012

IMAGE QUALITY OF THE CHEST RADIOGRAPHDr Ng Kian Seng

MBBS (Singapore) MCGP (Malaysia)Master Of Medicine (Internal Medicine,

Singapore)FAFP (Malaysia) Cert In Occupational Medicine

Ph D (Theology, USA)

IMAGE QUALITY OF THE CHEST RADIOGRAPH

Before interpreting the Chest Radiograph, it isimperative that you assess the quality of theimage. If you skip this step, you may diagnosea “phantom” disease or you may be wronglyreassured that all is well when in reality alife threatening condition is lurking like a ghost in the pixelated shadows of a poorly created Image.

To assess the quality of the imageof the Chest Radiograph, you haveto scrutinize the CXR in the following areas:I. InclusionP. ProjectionI. InspirationE. ExposureR. Rotation.These areas are circled in GreenIn the next slide, “I PIER at A to J” (i.e. I peer at A to J of the alphabet.)

In addition to the 5 above areas, you may want to look atA1. Angulation & A2. Artifacts.

We will look at these 7 areas in thisPowerPoint…

SYSTEMATIC READING

OF THECHEST

RADIOGRAPH

Systematic (methodical) approach to the reading of the CXR is necessary to help us avoid overlooking

an abnormality. Use this simple mnemonic to help you, “I PIER at A to J” (i.e. I peer at A to J of the alphabet.)

Letter Description

I 1I 2

I 3

Initial SurveyIdentity

Inclusion

P Position

I Inspiration

E Exposure

R Rotation

Letter Description

A Airways

B Bones

C Cardiac Silhouette

D Diaphragm

E Edges of Heart, theSurrounding Mediastinum

F Fields Of Lungs

G Gastric Bubble

H Hilar RegionsHardware

I In case U Forgetareas

J Jolting Your Patient’s Memory

First Rib Cut off

Lateral edge of Ribs Not Included

Costophrenic Angle NotVisualized

I = INCLUSION (Anatomy Inclusion)A Chest X-ray should include the entire thoracic cage. Occasionally, important anatomical structures like the first rib, lateral edges of ribs& the costophrenic angles are not visualized.

I

P = Position PA, AP, Lateral. The Standard Position or Projection is the Erect PAThe ICU patient will have a supine AP view and the image will be “fuzzier”, a firstlook gives you the impression that it is a poor quality image.P

PA View Supine AP View “Fuzzier”

P

(1)“Fuzzier” AP Projection images are of lower Quality than PA views. The image is “Fuzzier”

(2) “Pseudocardiomegaly” Heart is further away from the film and therefore Magnified.

(3) “Scapulae” The scapulae are not retracted laterally and they remain projected over each lung.

(4) “Equalization” In the Supine AP view, there is more equalization of the pulmonary vasculature when the size of the lower lobe vessels are compared to the upper.

Characteristics of AP Projection of a Chest Radiograph

P

AP Projection: Heart is further away from the film and therefore Magnified

AP & PA Projections of the Chest Radiograph

12

3

4

5

6

7

8

9

10

12

3

4

5

6

7

I = Inspiration. Exposure should be made on deep suspended inspiration. Count the visible ribs. Lung fields should extend to about 10th or 11th posterior ribs. The anterior end of approximately 6-7 ribs should be visible above the diaphragm in the mid clavicular line.

I

Sometimes we ask forA CXR in expiration…

When?

The difference between an Inspiration and an Expiration Film. The one taken in Expiration looks “stunted”…(on the right).I

The Difference between Normal Expansion and HyperexpansionI

Normal Expansion Hyperexpansion “Elongated”

(1) “Stunted” When the exposure is notmade in deep suspended inspiration, theimage appears stunted.(2) “Pseudocardiomegaly” The volume of air in the hemithorax will affect the configuration & dimensions of the heart . With shallow inspiration there is a smaller volume of air in the thorax & this results in an apparently “larger heart”. (3) “Diaphragm” The raised position of the diaphragm leads to exaggeration of heart size, and obscuration of the lung bases.(4) “Vascular Pattern” The vascular pattern in the lung fields will be accentuated because the same amount of blood flow is now distributed to a smaller volume of lung.(5) “Crowding” Crowding of lung markings may be mistaken for air space disease

I

EXPIRATION ORSHALLOW INSPIRATION

Inadequate Inspiratory Effort, Expiration Phase, Or Shallow Inspirationwill result in an image that has these characteristics…

HyperexpansionI

(1) “Taller” image appearstaller than usual

(2) “7th Rib” More than the mandatory 7th anterior rib atthe diaphragm in the Mid Clavicular Line

(3) “Hemidiaphragms” areFlattened

(3) “Costophrenic Angles”Apparent Blunting of Costophrenic angles

(5) “C.O.L.D” Usually in the patient with Chronic Obstructive Lung Disease

E = Exposure If the film is penetrated enough, you should be able to make out the spinous processes “inside” the vertebra. And you should be able to see the lower thoracic vertebral bodies through the heart.E

Correct Exposure or Penetration

Under Exposed, Film is “Too White”

(1) “Too White” Image is “Too White”

(2) “Vertebrae” The spinousprocesses in the vertebrae are not visualized. Lower thoracic vertebra are not seen throughthe heart

(3) “Lower Zones” There is poor Visibility of the lower zone structures,retrocardiac region, lower lung fields& left hemidiaphragm.

(4) “Pulmonary Markings” The pulmonary markings will appear more prominent than they actually are and can simulate pneumonia or effusion

If the Film is Under Exposed, it will look “Too White”…E

Over Exposed, “Too Black”

(1) “Too Black” Image appears“Too Black”

(2) “Bones” Bony details of ribs are not visualized.

(3) “Lungs” Lung markings are Not visualized.

(4) “Pitfall” Over penetration results in loss of visibility of low density lesions, such as an early consolidation, a coin lesion, an early malignancy

E If the Film is Over Exposed, it will look “Too Black”…

 R = Rotation Be careful to Xray the patient “ flat “against the cassette, if there is rotation, the mediastinum will look unusual. Look for rotation by observing the clavicle heads and determine if they are equidistant from the spinous process of the thoracic vertebra. If they are not, there is rotation.

R

Centered RotatedR

If spinous process appears closer to the right clavicle (red arrow), the patient is rotated toward his own left side .

If spinous process appears closer to the left clavicle (red arrow), the patient is rotated toward his own right side

R

RO

TATIO

N

RGreen arrows

Point to medialHeads

Of clavicleYellow point to

Distorted Mediastinum

If there is significant rotation, the side that has been lifted appears narrower and denser (whiter) and the

cardiac silhouette appears more in the opposite lung field.

Rotation Causes Distortion Of The Mediastinal Anatomy

RRotation Causes These Aberrations

(1) “Distortion” Rotation of the patient distorts mediastinal anatomy and makes assessment of cardiac chambers and the hilar structures difficult. (2) “Deviation” It may be difficult to know if the trachea is deviated to one side by a disease process.(3) “Transradiant” The “darker” lung field is the side nearer to the film.(4) “Magnification” Severe rotation may make the pulmonary arteries appear larger on the side farther from the film.(3) “Asymmetry” Changes in lung density due to asymmetry of overlying soft-tissue may be incorrectly interpreted as lung disease.

R

Rotated patientThe true size of the heart may be underestimated

Rotated patientHeart size is exaggerated

Well centred patient An accurate assessment can be made

THE HEARTSIZEIN ROATATION

A1Correct Angulation. The beam of the x-ray should be perpendicular to the erect chest film, if it is, you will see the Medial end of Clavicle at the level of 3rd posterior rib. If the beam of x-ray is not perpendicular to the film, you will get a "distorted" image, perhapsEnding up with a lordotic view.

ArtifactsThe appearance of anatomical structures may be artifactual because of radiographic technique, patient factors, or the presence of external or internal non-anatomical objects. Artifact is often unavoidable, but some artifact can lead to misinterpretation of the image.

A2

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. Click to see.

Summary : Image Quality of a Chest Radiograph

Remember the Mnemonicfor the Quality of a CXRI PIER A1A2Inclusion : The whole thoracic Anatomy to be included.

Position : Supine AP gives a Low quality “fuzzier” Image

Inspiration : 6 to 7 anterior ribs intersecting the diaphragm in the mid-clavicular line

Exposure : Spine visible behind the heart

Rotation : Spinous processes at midpoint between medial ends of the clavicles

Angulation : Medial end of Clavicle at the level of 3rd posterior rib

Artifacts : Cause difficultiesIn interpretation

Exp HyperexpInspiratoryEffort

Inclusion ofWhole Thorax

SUPINE AP

ERECT PA

Projection

WHITE BLACK

Exposure

Artifacts

Rotation

Angulation

I M A G E

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Collage, Shanghai Girl Series By Ng Kian Seng