Show February 28, 2002 -- This article continues our series of white papers on radiologic patient positioning techniques for x-ray examinations. Appearing each month on AuntMinnie.com, the series will explore each of the major modalities. If you'd like to comment on or contribute to this series, please e-mail .The dorsal decubitus (right or left) position is a good alternative to obtaining a lateral decubitus or erect abdominal x-ray image when a patient cannot stand or lie on their side. It can provide information regarding pneumoperitoneum and air fluid levels in cases of suspected acute abdominal trauma. The examination can be performed at the patient’s location, such as the ICU, with a mobile x-ray unit. This view can also help to evaluate an incisional hernia or the diameter of a calcified aortic aneurysm.
Position of the patient Place the patient in the supine position on a radiolucent pad with the right or left side against the grid device. Elevate their arms and place them along side their head or across the upper chest. Placing a support under the knee helps to relieve strain when a patient is in the supine position. Position of abdomen
Film holder placement Adjust the height of the vertical grid so the long axis of the cassette is centered to the mid-coronal plane. A 14 x 17 inch (35 x 43 cm) film or image receptor (IR) should be positioned crosswise. Central ray The central ray (CR) should be horizontal and perpendicular to the center of the cassette and directed to the mid-coronal plane, 2 inches (5 cm) above the level of the iliac crests. Collimation Collimation is adjusted to center mid-coronal plane of the patient to the IR margins, making sure that upper and lower soft tissue borders the abdomen are included. Close collimation is important because of the increased scatter from a high kVp and the need for soft tissue visibility. Imaging technique
Evaluation criteria for a good dorsal decubitus projection
Left lateral decubitus AP abdominal exam The left lateral decubitus position is usually performed on patients who are too ill to stand and are lying on a transportation cart. Special care must be exercised to ensure that patient does not fall off the cart. Lock all the wheels securely in position. Remove any opaque objects in the clothing or gown that can cause artifacts in the area to be x-rayed. Use gonadal shielding on males; the upper edge of the shield should not be above the pubic symphysis. In female patients, an ovarian shield can obscure pelvic anatomy, so one should not be used unless the physician requests it. Position of the patient
Position of abdomen
Film holder placement The long axis of the film should be parallel with the long axis of the body and film is centered to the CR. A 14 x 17 inch (35 x 43 cm) film or IR should be positioned lengthwise, with its lower edge at the symphysis pubis. Crosswise cassette placement is appropriate if the patient is very large. The proximal margin of the cassetteshould be approximately at the level of the axilla. Central ray The CR is directed to the midpoint of the mid-sagittal plane at the level of the iliac crest, in some patients a slightly higher CR, 2 inches (5 cm) above the iliac crest may be needed to include the diaphragms. The CR is directed perpendicular to the film. Collimation Collimation is adjusted to center mid-sagittal plane of the patient to the IR margins, making sure that upper side of the abdomen is clearly included. Imaging technique
Evaluation criteria for a good left lateral decubitus projection
Supplemental projections of the abdomen When a patient with an acute abdominal trauma is evaluated, the following radiographic projections may be ordered.
AuntMinnie.com contributing writer February 28, 2002 Related Reading AP abdominal projection x-ray positioning techniques, January 16, 2002 Tips and techniques for decubitus and oblique chest x-rays, December 21, 2001 Mastering AP and lateral positioning for chest x-ray, November 20, 2001 Good positioning is key to PA chest x-ray exams, October 19, 2001 Copyright © 2002 AuntMinnie.com How is the patient positioned for a dorsal decubitus projection?Patient Position:
Supine on radiolucent pad, side against table or vertical grid device; secure cart so that it does not move away from table or grid device. Pillow under head, arms up beside head; support under partially flexed knees may be more comfortable for the patient.
What is the dorsal decubitus position?dorsal recumbent position position of patient on the back, with lower limbs flexed and rotated outward; used in vaginal examination, application of obstetrical forceps, and other procedures.
What is the lateral decubitus position?Medical Definition of lateral decubitus
: a position in which a patient lies on his or her side and which is used especially in radiography and in making a lumbar puncture.
How should the patient be positioned for a dorsal left decubitus radiograph?Position of the patient
Place the patient in the left lateral recumbent position on a radiolucent pad. The patient's back should be against the grid device. Before films are obtained, the patient should be in the left side down position for at least 10 minutes.
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