Radiographic Techniques of The Abdomen PDF

Radiographic techniques  Abdomen Planes & regions and Image parameters, Abdomen , AP supine, PA erect , lateral view positions  :BY Ahmed Jasem Abass  MSC of Medical Imaging Radiographic Techniques of The abdomen Planes and regions (Figs 1...

Radiographic techniques  Abdomen Planes & regions and Image parameters, Abdomen , AP supine, PA erect , lateral view positions  :BY Ahmed Jasem Abass  MSC of Medical Imaging Radiographic Techniques of The abdomen Planes and regions (Figs 10.1a, 10.1b)  The abdominal cavity extends from the inferior surface of the diaphragm to the pelvic inlet inferiorly and is contained by the muscles of the abdominal walls.  To mark the surface anatomy of the viscera, the abdomen is divided into nine regions by two transverse planes and two parasagittal (or vertical) planes. Fig 10-1a (Planes of abdomen)  The upper transverse plane, called the transpyloric plane, approximately midway between the upper border of the xiphisternum and the umbilicus, passes through the tips of the right and left 9th costal cartilages; also in most cases the plane also cuts through the level of the pylorus of the stomach.  The lower transverse plane, called the transtubercular plane is at the level of the tubercles of the iliac crest anteriorly and near the upper border of the 5th lumbar vertebra posteriorly.  The two parasagittal planes are at right-angles to the two transverse planes. They run vertically passing through a point midway between the anterior superior iliac spine and the symphysis pubis on each side, in the midclavicular line.  These planes divide the abdomen into nine regions centrally from above to below epigastric, umbilical and hypogastric regions and laterally from above to below right and left hypo- chondriac, lumbar and iliac regions. Fig 10-1b (Radiographic image of planes and region)  The main factors affecting the position and surface markings of organs are: (a) body build, (b) phase of respiration, (c) posture (erect or recumbent), (d) loss of tone of abdominal muscles that may occur with age, (e) change of organ size due to pathology, and (f) the presence of an abnormal mass and normal variants within the population.  Individuals have been classified according to body build, into four types – hypersthenic, sthenic, hyposthenic and asthenic.  Hypersthenic – massively built. The dome of the diaphragm is high and the lower costal margin is at a high level with a wide angle, resulting in the widest part of the abdomen being its upper part. The stomach and transverse colon are in the upper part of the abdomen as shown in Figure 10- 2a.  Asthenic – thin and slender. The elongated narrow thorax with a narrow costal angle is associated with a low position of the dome of the diaphragm. The abdominal cavity  is shallow being widest in its lowest region. The pylorus of the stomach is low and the long stomach may reach well below the iliac crests, while the transverse colon can loop down into the pelvic cavity as shown in Figure 10- 2b.  Between these two extremes of body build are the sthenic (tending towards hypersthenic, but not as broad in proportion to height) and the hyposthenic (tending towards asthenic, but not as thin and slender. Hypersthenic Asthenic Most common referral criteria  Radiographic examination of the abdomen and pelvic cavity is performed for a variety of reasons. These include:  Obstruction of the bowel.  Perforation.  Renal pathology.  Acute abdominal pain (with no clear clinical diagnosis).  Foreign body localization  Toxic mega colon.  Aortic aneurysm.  Prior to the introduction of a contrast medium, e.g. intravenous urography (IVU) to demonstrate the presence of radio- opaque renal or gall stones.  To detect calcification or abnormal gas collections. Typical imaging Protocols  The following table illustrates projections used to diagnose common clinical conditions.  Recommended Projectio Image parameters  Although the radiographic technique used will depend on the condition of the patient, there are a number of requirements common to any plain radiography of the abdomen and pelvic cavity. Maximum image sharpness and contrast must be obtained so that adjacent soft tissues can be differentiated.  Essential image characteristics  Coverage of the whole abdomen to include diaphragm to inferior to the symphysis pubis and lateral fat stripe.  The whole of the urinary tract (kidneys– ureters–bladder (KUB) should be demonstrated.  High resolution and the adequate contrast to demonstrate the interface between air-filled bowel and surrounding soft tissues.  Radiation protection  Exclusion of pregnancy unless it has been decided to ignore it in the case of an emergency.  Gonad shielding can be used for males.  Antero-posterior – supine (Figs 10.6a, 10.6b)  A 35 × 43 cm CR cassette is selected.  Position of patient and image receptor  The patient lies supine on the imaging table with the median sagittal plane at right-angles and coincident with the mid- line of the table.  The pelvis is adjusted so that the anterior superior iliac spines are equidistant from the tabletop.  If a CR cassette is selected it is placed longitudinally in the cassette tray and positioned so that the region below the symphysis pubis is included on the lower margin of the image.  The center of the image receptor will be approximately at the level of a point located 1 cm below the line joining the iliac crests. This will ensure that the region inferior to the symphysis pubis is included on the image. Fig. 10.6a Patient positioning.  Direction and location of the X-ray beam  The collimated vertical beam is directed to the centre of the image receptor to include the lateral margins of the abdomen.  Using a short exposure time, the exposure is made on arrested respiration. Ideally respiration should be arrested on full expiration to allow the abdominal contents to lie in their natural position.  Fig. 10.6b Fig. 10.6b Normal abdominal radiograph  Common faults and solutions  (Fig. 10.7a, Fig. 10.7b )  Failure to include the region inferior to the symphysis pubis and the diaphragm on the same image. This may be due to patient size, in which case two images are acquired, i.e. if using CR the cassettes are placed transversely (landscape) across the abdomen to include upper and lower abdominal regions.  Respiratory movement unsharpness may be reduced by rehearsal of the arrested breathing technique prior to exposure.  Rotation may be evident when the patient is in pain.  Presence of artifacts such as buttons or contents of pockets if the patient remains clothed for the examination.  Fig. 10.7a Inadequate/incomplet e abdomen radiograph with right ureteric stent lower abdominal margin not visualized. Fig.  Fig. 10.7b Rotated abdomen radiograph with distended small bowel loops with faecal loading and gas in rectum indicative of small bowel obstruction.  Antero-posterior – erect (standing or sitting)  (Figs 10.8a–10.8c)  If possible the patient is examined standing or seated against a vertical Bucky, or alternatively may be examined on a tilting table. If necessary the patient may be examined sitting on a trolley or on a chair using a 35 × 43 cm CR cassette.  Position of patient and image receptor  The patient stands/sits with their back against the receptor/ vertical Bucky.  If standing the patient’s legs are placed well apart so that a comfortable and steady position is adopted.  If seated care must be taken to ensure the flexed knees are not obscuring the lower abdomen.  The median sagittal plane is adjusted at right-angles and coincident with the midline of the vertical Bucky.  The pelvis is adjusted so that the anterior superior iliac spines are equidistant from the image receptor.  The upper edge of the image receptor (35 × 43 cm CR cassette) is positioned at the level of the middle of the body of the sternum so that the diaphragms are included.  Direction and location of the X-ray beam  The collimated horizontal beam is directed so that it is coincident with the centre of the receptor in the midline.  An exposure is taken on normal full expiration. Antero-posterior – left lateral decubitus  This projection is used if the patient cannot be positioned erect to confirm the presence of sub diaphragmatic gas. It should only be undertaken as a specific request when other modalities such as ultrasound/CT cannot be used. It may also be used for con firming a bowel obstruction.  With the patient lying on the left side, free gas will rise to be located between the lateral margin of the liver and the right lateral abdominal wall. To allow time for the gas to collect the patient should remain lying on the left side for a short while (e.g. 10 minutes) before the exposure is made. Antero-posterior – left lateral decubitus  Position of patient and image receptor  The patient lies on their left side, on a trolley, with the elbows and arms flexed so that the hands can rest near the patient’s head.  The patient is positioned with the posterior aspect of the trunk against a vertical Bucky with the upper border of the image receptor high enough to project above the right lateral abdominal and thoracic walls. Alternatively, a 35 × 43 cm CR grid cassette is supported vertically against the patients back.  Direction and location of X-ray beam  The collimated horizontal central beam is directed to the anterior aspect of the patient and centred to the centre of the image receptor. Patient positioning for antero- posterior Fig.10.9b Antero- posterior left lateral decubitus images of the abdomen Showing free air in the abdominal cavity  left lateral decubitus. Lateral – dorsal decubitus (supine) (Figs 10.9c, 10.9d)  Occasionally the patient is unable to sit or even be rolled on to their side, thus the patient remains supine and a lateral projection is taken using a horizontal central ray.  Position of patient and image receptor  The patient lies supine with the arms raised away from the abdomen and thorax.  A 35 × 43 cm CR grid cassette is supported vertically against the patient’s side to include the  thorax to the level of mid-sternum and as much of the abdomen as possible. Care should be taken that the anterior wall of the trunk is not projected off the resultant image.  Direction and location of the X-ray beam  The collimated horizontal central beam is directed to the lateral aspect of the trunk at right angles to the receptor. Urinary tract – kidneys– ureters–bladder  Plain radiography of the abdominal and pelvic cavity is undertaken to visualize:  The outline of the kidneys surrounded by their perirenal fat.  The lateral border of the psoas muscles.  Opaque stones in the kidney area.  Calcifications within the kidney or within the bladder.  The presence of gas within the urinary tract.  Any other acute abdominal pathology. Antero-posterior (Figs 10.10a, 10.10b)  Position of patient and image receptor  The patient lies supine on the X-ray table with the median sagittal plane of the body at right-angles to and in the mid- line of the table.  The patient’s hands may be placed high on the chest or the arms may rest by the patient’s side slightly away from the trunk.  The Bucky detector used should be large enough to cover the region from above the upper poles of the kidneys to the symphysis pubis (or a 35 × 43 cm CR cassette is used).  The image receptor is positioned so that the symphysis pubis is included on the lower part of the image.  The center of the image receptor will be approximately at the level of a point located 1 cm below the line joining the iliac crests. This will ensure that the symphysis pubis is included on the image.  Direction and location of the X-ray beam  The vertical collimated beam is directed to the center of the image receptor with the lateral margins collimated within the margins of the image receptor.  The exposure is made on arrested expiration. Thank You