chest x ray techniques and positioning

7/30/2019 Chest x Ray Techniques and Positioning

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Dr. Pankaj agarwal


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For a good radiograph to be produced a setof exposures factors are to be selected

. The miliampere seconds(mAs)

The kilo voltage

The focus to film distance


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Region being examined

Thickness

Density

Pathology

Types of screens and films used

Grid

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Product of x ray tube current(mA)and time(s)

indicates amount of radiation being used

Determines film blackening

mA should be larger to reduce exposure time

mAs underexposed film

mAs overexposed film

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Determines contrast of the film

Max contrast can be obtained if lowest kVp possible is used

As kVp is increased not only is radiation more penetrating butmore radiation is produced

Thus increased kV allows mAs and thus exposure time tobe reduced


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For a given kVp and mAs greater the FFD less theintensity of radiation reaching the film

FFD should not be too less, so as to preventradiation damage to skin.

And should not be to large to prevent high tubeloading .

FFD is sometimes increased to reduce geometricalunsharpeness, magnification, and distortion

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In trying to determine if pathology is present in

a chest radiograph following factors are to beconsidered on all chest x-rays:

Inspiration

Penetration

Rotation Angulation

Orientation

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The vascular pattern in the lung fields will beaccentuated with a shallow inspiration sincethe same amount of blood flow is now

distributed to a smaller volume of lung. The level of inspiration can be estimated by

counting ribs. Visualization of nine posteriorribs, or seven anterior ribs on an upright PA

radiograph projecting above the diaphragmwould indicate a satisfactory inspiration.

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The lack of penetration renders the area whiterand can simulate pneumonia or effusion. In anideal radiograph the thoracic spine(T8/9) shouldbe barely viewing through the cardiac silhouette.

On the lateral view, we can look for properpenetration and inspiration by observing that thespine appears to be darker as we move caudally.

This is due to more air in lung in the lower lobesand less chest wall. The sternum should be seenedge on and posteriorly we should see two sets ofribs.

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Rotation of the patient distorts mediastinalanatomy and makes assessment of cardiacchambers and the hilar structures especiallydifficult.

Chest wall tissue also contributes to increaseddensity over the lower lobe fields simulatingdisease.

Rotation of the radiograph is assessed by judgingthe position of the clavicle heads and the thoracicspinous process. Ideally the clavicle heads shouldbe equidistant from the spinous process.

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In this we are making reference to theposition of the patient and the x-ray beam.

A PA radiograph is obtained with the x-raytraversing the patient from posterior toanterior and striking the film.

Similarly an AP radiograph is positionedwith the x-ray traversing the patient fromanterior to posterior striking the film. Thecardiac border or silhouette will appearlarger on an AP radiograph due to themagnification effect of the more anteriorlylocated heart relative to the film

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With the patient in a more lordoticprojection the clavicles will projectsuperiorly relative to the upper thorax

With the lordotic projection of the ribsassume a more horizontal orientation.

Occasionally a lordotic xray can beobtained intentionally to better visualizestructures in the thoracic apex obscuredby overlying bony structures.

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Posterio anterior (PA view)

Anterio posterior (AP view)

Lateral projection(R or L position)

PA Oblique projection(RAO and LAO)

AP Oblique projection (RPO and LPO)

AP axial (lordotic view)

Lateral decubitus (R or L)

Dorsal decubitus(R or L)

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If possible, always examine patients in uprightposition.

Place the patient ,with arms hanging at sides,

before a vertical grid device. Adjust the height of IR so that its upper border

is about 1.5 to 2 inches above relaxedshoulders.

Center the midsagittal plane of the patientsbody to midline of IR.

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Extend the patients chin upward and adjusthead so that midsagittal plane is vertical.

Ask the patient to flex the arms and to rest back

of hands low on hips below level ofcostophrenic angles.

In female patients ask her to pull breastupward and laterally.

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Exposure is made after second full inspirationto ensure max.expansion of lungs.

Central ray should be centered at T7,

perpendicular to center of IR.

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Entire lung fields from apices to cpa

There should be no rotation

Scapulae projected outside lung fields

9 posterior ribs or 7 anterior ribs visible

Sharp outlines of heart and diaphragm

Faint shadow of ribs and superior thoracic

vertebrae visible through heart shadow

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Patient is in supine or upright position withback against grid.

Center midsagittal plane of chest to IR

Upper border of IR should be 1.5 to 2 inchesabove relaxed shoulders.

Adjust the shoulders to lie in the same

transverse plane.

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Exposure is made after second full inspirationto ensure max. expansion of lungs.

Perpendicular to the long axis of sternum and

center of IR. Central ray should enter 3 inches below jugular

notch.

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Magnified and engorged heart and greatvessels.

Lung fields appear shorter.

Clavicles are projected higher. Ribs assume horizontal position.

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Entire lung fields from apices to cpa.

Medial portion of clavicles equidistant fromvertebral column.

Trachea in midline. Faint shadow of ribs and superior thoracic

vertebrae visible through heart shadow

Equal distance from vertebral column to lateralborder of ribs on each side.

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If possible always examine in upright standingposition.

Turn the patient to true lateral position ,

midsagittal plane being parallel to IR. Midcoronal plane being perpendicular to grid.

Extend the arms directly upwards ,flex the

elbows, and with forearms resting on elbowshold the arms in position.IR should be 1.5 to 2inches above shoulder.

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Exposure is made after second full inspirationto ensure max. expansion of lungs.

Central ray should enter the patient onmidcoronal plane at level of T7 or inferioraspect of scapula , perpendicular to center of IR

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Lateral projection (R or L)-Exposure


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LUL

LLL


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Superimposition of ribs posterior to vertebralcolumn

Arm or soft tissue not overlapping the

superior lung field Lateral sternum with no rotation

Open thoracic IV disc spaces and intervertebralforamina

hilum in the center of radiograph

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Place the patient on either affected or unaffectedside, as indicated, for at least 5 minutes beforeexposure.

Extend the arms well above head and adjustthorax in a true lateral position.

Adjust IR so that it extends approx. 1.5 to 2

inches beyond shoulders.

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After second full inspiration

Central ray is horizontal and perpendicular tothe center of IR at a level 3 inches below jugular

notch for AP or at T7 for PA. This view helps in demonstrating any change

in fluid level and reveals obscured pulmonaryareas.

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No rotation of patient

Affected side is shown completely

Patients arm not visible in field of interest

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Arrows showing pleural effusion

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keep patient in prone or supine position,centering thorax to grid , keeping for at least 5min. in the same position.

Extend arms well above head.

Place the affected side against a vertical grid,adjusting it so that top of IR extends to level of

thyroid cartilage.

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After second full inspiration

Central ray is horizontal and perpendicular tothe center of IR at a level of midcoronal plane

and 3 inches below jugular notch for dorsal orat T7 for ventral decubitus.

This view helps in demonstrating any changein fluid level and reveals obscured pulmonary

areas.

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Place the patient in upright position ,facing X-ray tube and standing 1 feet in front of verticalgrid, with midsagittal plane centered to

midline of grid. Adjust the IR so that its upper margin is about

3 above upper border of shoulders (when thepatient is adjusted in lordotic view.

For oblique lordotic positions rotate the patient30 degrees away from the position used for APposition, with affected side towards the grid.

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After second full inspiration.

Central ray being perpendicular to the center ofIR at level of midsternum.

This view helps in demonstrating the apicesand interlobar effusions.

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Clavicles lying horizontaly and superiorly toapices.

Sternal end of clavicles equidistant from

vertebral column. Apices and lungs completely.

Ribs distorted with anterior and posterior endsomewhat superimposed.

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clavicle Lung apex


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Maintain the patient in the position used for PAprojection.

Have the patient turn approx. 45 degrees towardsleft side for LAO ,towards right side for RAO.

The side of interest being the farther from the IR.

Top of IR should be placed 1.5 to 2 inches abovevertebral prominence.

Exposure is done in full inspiration with centralray perpendicular to center of IR at level of T7

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Maximum area of right lung along withthoracic viscera .

Left lung superimposed by the spine.

Trachea and its bifurcation(carina) Right branch of bronchial tree.

Heart

Descending aorta (lying in front of spine) Arch of aorta .

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Maximum area of left lung along withthoracic viscera .

Right lung superimposed by the spine.

Trachea and left branch of the bronchial tree. Right retrocardiac region .

Anterior portion of apex .

Left atrium

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Left lung

heart

R main bronchus

carina

Trachea


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One point to remember is that RPOcorresponds to LAO position and LPO

corresponds to RAO position The side of interest being closestto IR.

With the patient in supine position ,adjust theIR so that upper border is about 1.5 to 2 inchesabove vertebral prominence or about 5 inchesabove jugular notch.

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Rotate the patient toward the correct side,adjust the body at a 45 degree angle ,andcenter thorax to the grid.

Adjust the shoulders to lie in the sametransverse plane in a position of forwardrotation.

Exposure is made in second full inspiration

perpendicular to center of IR at a level 3 inchesbelow jugular notch .

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This view presents AP oblique projection of

thoracic viscera similar to corresponding PAoblique projection .

RPO being comparable to LAO ,LPO to RAO.

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chest x ray techniques and positioning

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