POSTERIOR OBLIQUE : RPO AND LPO

Pathology Demonstrated:

• Pathology involves the lung fields, trachea, and mediastinal structures, including the size and contours of the heart and great vessels.

Technical Factors:

• IR size - 35 x 43 cm ( 14 x 17 inches), lengthwise
• Moving or stationary grid
• 110 - 125 kV range

Shielding:

• Secure lead shield around waist to shield gonads.

Patient Position:

• Patient erect, rotated 45degrees with right posterior shoulder against IR for RPO and 45degrees with left posterior shoulder against IR for LPO
• Arm closest to IR raised resting on head; other arm placed on hip with palm out
• Patient looking straight ahead

Patient Position: (Recumbent)

• If patient cannot stand or sit, take posterior obliques on table.
• Place support under patient's head and under elevated hip and shoulder.

Part Position:

• Top of IR about 1inch (2cm) above vertebral prominens or  about 5 inches(12 cm) above level of jugular notch (2 inches or 5cm above shoulder)
• Thorax centered to CR and to IR

Central Ray:

• CR perpendicular, to the level of T7
• SID of 72 inches (180)

Collimation:

• Collimate to area of lungs.

Respiration:

• Exposure made after second full inspiration.

Note:

• Posterior obliques provide best visualization of the side closest to the IR.
• Posterior positions show the same anatomy as the opposite anterior oblique positions. Thus the LPO position corresponds to the RPO to the LPO.