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Posterior-Anterior (PA) projectionThe 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. PA projectionClick image to align with top of page PA 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 projectionClick image to align with top of page AP projection
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. AP v PA projectionClick image to align with top of page AP v PA projection
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 you are not sure then look at the medial edges of each scapula. AP projection - exampleHover on/off image to show/hide findings Tap on/off image to show/hide findings Click image to align with top of page AP projection - example
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 - exampleHover on/off image to show/hide findings Tap on/off image to show/hide findings Click image to align with top of page PA projection - example
When performing an AP projection of the humerus how far above the level of the shoulder should the top of the IR be placed?Positioning for a lateral projection of the humerus
Place the top margin of the cassette approximately 1½ inches (3.8 cm) above the level of the head of the humerus. Unless contraindicated by possible fracture, internally rotate the arm, flex the elbow approximately 90°, and place the patient's hand on their hip.
How many degrees should a to be angled for an AP axial projection of the clavicle on an average patient?The central-ray angle for an AP axial projection of the clavicle when performed on a patient in the supine position is 15-30 degrees caudal.
What is the proper Cr angle and direction on the AP axial projection of the clavicle?Central ray: The central ray should be directed to the scapulohumeral joint perpendicular to the image receptor. For an AP Axial, a cephalic angle of 35 degrees.
How much should the CR be angled for an AP axial projection of the clavicle on an asthenic patient?Chapter 6. |