Tuesday, February 10, 2009

How to do R & L Chest Posterior Obliques?

The patient stands erect facing the tube, from here the patient is rotated 45degrees with the affected side on the film, both arms are raised and placed across the head which may need to be turned towards the affected side for comfort and ease of positioning.
If the pathology is suspected on the right side, then the right posterior chest should be on the cassette. If the lesion is suspected on the left, then it is the left posterior chest should be on the cassette.

The film focus distance is 100cm (instead of 180cm). 

The kV should be reduced because the FFD is now shorter but the mA should be increased because the tissue is now thicker when the patient is oblique cf PA view.

Radiation protection:
Wear lead apron for waist level protection.

Central Ray:
The horizontal central ray is centered at mid clavicular line at a point midway between the sternal notch and the xiphisternum.
Exposure is made on suspended deep inspiration.

Evaluation of the Image:
ID and markers must be present and correct in the appropriate area of the film. Remember it is now AP and not PA anymore. 
Limits of examination, superiorly the 1st rib, inferiorly the 12th rib, medially the spine, laterally the distal ends of the ribs and skin surface (affected side).
The elongated axillary portion of the ribs being investigated (affected side) should
be clearly seen.
There should be no evidence of respiratory movement.
The exposure should penetrate the cardiac shadow sufficiently to demonstrate
detail in the ribs in its shadow, and the ribs below the diaphragm

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