P97 Chest Lateral decubitus positionClinical Indications • Small pleural effusions are demon-strated by air-fluid levels in pleural space ▪ Small amounts of air in pleural cavity may demonstrate a possible pneumotho-rax (see Notes) Technical Factors • Minimum SID-72 inches (183 cm) • IR size-35 x 43 cm (14 x 17 inches), landscape (with respect to patient position) • Grid • Analog and digital systems—istl 0 to 125 kV range • Use decubitus (decub) marker Shielding Shield: radiosensitive tissues outside region of interest Patient Position • Cardiac board on the cart or radiolucent pad under patient • Patient lying on right side for right lateral decubitus and on left side for left lateral decubitus (see Notes)• Patient's chin extended and both arms raised above head to clear lung field; back of patient firmly against IR; cart secured to prevent patient from moving forward and possibly falling; pillow under patient's head (Fig. 2.67)• Knees flexed slightly and coronal plane parallel to IR with no body rotation Part Position • Adjust height of IR to center thorax to IR (see Notes) • Adjust patient and cart to center midsagittal plane and T7 to CR (top of IR is approximately 1 inch [2.5 cm] above vertebra prominens) CR • CR horizontal, directed to center of IR, to level of T7, 3 to 4 inches (8 to 10 cm) inferior to level of jugular notch. A horizontal beam must be used to show air-fluid level or pneumothorax Recommended Collimation Collimate on four sides to area of lung fields (top border of light field to level of vertebra prominens) (see Notes) Respiration Make exposure at end of second full inspiration Alternative PositioningSome department protocols state that the head be 10° lower than the hips to reduce the apical lift caused by the shoulder, allowing the entire chest to remain horizontal (requires support under hips)NOTES: Place appropriate decubitus marker and R or L to indicate which side of chest is down. Radiograph may be taken as a right or left lateral decubitus. To produce the most diagnostic images, both lungs should be included on the image. For possible fluid in the pleural cavity (pleural effusion), the suspected side should be down. Do not cut off that side of the chest. The anatomic side marker must correspond with the patients left or right side of the body. The marker must be placed on the IR before exposure. It unac-ceptable practice to indicate the side of the body either digitally or with a marking pen after the exposure For possible small amounts of air in the pleural cavity (pneumothorax), . the affected side should be up, and care must be taken not to cut off this side of the chest. Evaluation Criteria Anatomy Demonstrated: •Entire lungs, including, apices, bo costophrenic angles, and both lateral borders of ribs, should be included (Figs. 2.68 and 2.69). Position: • No rotation: Should show equal distance from the vertebral column to the lateral borders of the ribs on bot sides; sternoclavicular joints should be the same distance fro the vertebral column. • Arms should not superimpose upper lungs. • Collimation field (CR) should be centered to the area of 77 on average-sized patients.Exposure: • No motion; diaphragm, rib, and heart borders and lung markings should appear sharp. • Optimal controst Gale and exposure shoulc result in faint visualization of vertebrae and ribs through heart shadow.