Where is the central ray location for an upright ap projection of the abdomen?

Upright AP Projection - Abdomen

Upright xray examination of the abdomen is usually suggested when the Kidneys, Uriters and Bladder (KUB) are not the primary interest to be examine. Abdominal masses, air fluid levels and accumulation of intraperitoneal air under the diaphragm is best demonstrated in this position. 

Technical Factors:

• IR size - 35 x 43cm (14 x 17 inches), lengthwise
• Moving or stationary grid (use erect markers)
• 70 to 80 kV range

Marker and Shielding:

Place erect marker on IR.
Used gonadal shield on males. An adjustable freestanding mobile shield can be used as for chests.

AP Projection Abdomen (Erect)

AP Upright Position

Patient and Part Position:

• Upright, legs slightly spread, back against table or grid device (see note below for weak or unsteady patients)
• Arms at sides away from body
• Midsagittal plane of the body centered to bucky.
• No rotation of pelvis and shoulders.
• Adjust height of the bucky so that the center of IR is approximately 2 inches or (5cm) above iliac crest (this is to include the diaphragm). On the average patient this will place the top of the IR at approximately in the level of the axilla.

Central Ray, Collimation and Respiration

CR is horizontal and center of IR
Minimum SID of 40 inches or (100 cm)
Collimate closely on all four sides of the part being examine; be sure not to cut off the upper abdomen to included diagphragm.
Exposure should be made at end of expiration.

Note: Before making an exposure, the patient should be in an upright position for about 5 minutes. But it is advisable that 10 to 20 minutes is usually done if the patient can tolerate. In this length of time, the small amount of air in the intraperitoneal cavity of the lung, eventually will go up and become visible if present on the radiograph. Otherwise, if the patient is too weak, and cannot maintain its erect position for a long period of time, a lateral decubitus can be use. Also for hypersthenic patients, two crosswise radiographic film may be required to include the entire abdomen on the radiograph.

16

ABDOMEN

Abdominopelvic Cavity

The abdominopelvic cavity consists of two parts: (1) a large superior portion, the abdominal cavity, and (2) a smaller inferior part, the pelvic cavity. The abdominal cavity extends from the diaphragm to the superior aspect of the bony pelvis. The abdominal cavity contains the stomach, small and large intestines, liver, gallbladder, spleen, pancreas, and kidneys. The pelvic cavity lies within the margins of the bony pelvis and contains the rectum and sigmoid of the large intestine, the urinary bladder, and the reproductive organs.

The abdominopelvic cavity is enclosed in a double-walled seromembranous sac called the peritoneum. The outer portion of this sac, termed the parietal peritoneum, is in close contact with the abdominal wall, the greater (false) pelvic wall, and most of the undersurface of the diaphragm. The inner portion of the sac, known as the visceral peritoneum, is positioned over or around the contained organs. The peritoneum forms folds called the mesentery and omenta, which serve to support the viscera in position. The space between the two layers of the peritoneum is called the peritoneal cavity and contains serous fluid (Fig. 16-1). Because there are no mesenteric attachments of the intestines in the pelvic cavity, pelvic surgery can be performed without entry into the peritoneal cavity.

The retroperitoneum is the cavity behind the peritoneum. Organs such as the kidneys and pancreas lie in the retroperitoneum (Fig. 16-2).

Citation, DOI & article data

Citation:

Morgan M, Hayes J, Sheikh Y, et al. Abdomen (AP supine view). Reference article, Radiopaedia.org (Accessed on 27 Dec 2022) https://doi.org/10.53347/rID-38090

The AP supine abdominal radiograph can be performed as a standalone projection or as part of an acute abdominal series, depending on the clinical question posed, local protocol and the availability of other imaging modalities.

On this page:

This view is useful in assessing abdominal pathologies, including bowel obstructions, calcifications and neoplastic changes. It is also used as a scout/baseline image for contrast studies of the abdomen (i.e. small bowel follow-through).

• the patient is supine, lying on his or her back, either on the x-ray table (preferred) or a trolley
• patients should be changed into a hospital gown, with radiopaque items removed (e.g. belts, zippers, buttons)
• the patient should be free from rotation; both shoulders and hips equidistant from the table/trolley
• the x-ray is taken on full inspiration
  • this causes the diaphragm to contract, hence compressing the abdominal organs, allowing all abdominal contents to be visualized on a single image

• AP projection
•  centering point
  • the midsagittal plane, equidistant from each anterior superior iliac spine (ASIS) at the level of the iliac crest
• collimation
  • laterally to the lateral abdominal wall
  • superior to the diaphragm
  • inferior to the inferior pubic rami
• orientation
  • portrait
• detector size
  • 35 cm x 43 cm
• exposure
  • 70-80 kVp
  • 30-120 mAs; AEC should be used if available
• SID
  • 100 cm
• grid
  • yes

• if possible, the diaphragm should be included superiorly
• the abdomen should be free from rotation with symmetry of the:
  • ribs (superior)
  • iliac crests (middle)
  • obturator foramen (inferior)
• no blurring of the bowel gas due to respiratory motion

For larger patients, it may be necessary to perform two x-rays using a landscape orientation of the detector to include the entire abdomen.

Exposure will need to be adjusted according to the imaging system (CR or DR) and patient size. Where possible, mAs should be manipulated to ensure adequate image density and appropriate image contrast.

References

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