Abdominal Positioning in Radiography

Abdominal Positioning in Radiography The abdominal cavity extends from the under surface of the diaphragm above to the pelvic inlet below.

Introduction

Transpyloric plane is midway b/w supra sternal notch & symphisis pubis & posteriorly through body of L 1 anteriorly through tip of rt & Lt 9th costal cartilage.Nine regions of the abdominal cavity

Trans tubercular plane at the level of tubercles of iliac crest anteriorly upper border of L5 posteriorly.2 Parasaggital planes at right angles to transverse planes passing through a point midway b/w ant sup iliac spine and symphysis pubis dividing abdominal cavity into 9 regions.Intestinal obstructionPerforationRenal pathologyAcute abdomenForeign body localizationToxic mega colonAortic aneurysm.Prior to introduction of contrast medium.Referral criteriaMaximum image contrast and sharpness should be obtained so that adjacent soft tissues can be differentiated.Standard imaging table and a moving grid is usually used. Patient is immobilized and exposure is made on arrested respiration usually after full expiration.Image ParametersCoverage of the whole abdomen to include diaphragm to pubic symphysis.Visualization of the whole urinary tract i.e KUB.Sharp reproduction of bones and the interface between air filled bowel and surrounding soft tissues with no overlying artefacts e.g. clothing.In calculus disease good tissue differentiation is necessary to visualize small or low opacity stones.Essential image characteristicsPregnancy rule: unless it has been decided to ignore pregnancy in case of emergency.Gonad shielding.Follow a well planned procedure to avoid repetition and thus limit patient exposure.Radiation Protection:

1,11th rib.2,Vertebral body (TH 12).3,Gas in stomach.4,Gas in colon (splenic flexure).5,Gas in transverse colon.6,Gas in sigmoid.7,Sacrum.8,Sacroiliac joint.9,Femoral head.10,Gas in cecum11,Iliac crest.12,Gas in colon (hepatic flexure).13,Psoas margin.

A-P Projection of Abdomen

Patient supine with the MSP(median sagittal plane) at right angle and coincident with the midline of the table.Pelvis adjusted so that ant sup iliac spines are equidistant.Antero posterior supine position of patient and cassetteCassette is placed longitudinally in the cassette tray and positioned such that the symphysis pubis is included in the lower part of the film.Centre of the cassette is 1cm below the line joining the iliac crests.Vertical central ray is directed to the centre of the cassette.Exposure is made on arrested respiration.Bowel pattern should be demonstrated with minimal un sharpness.

Direction and Centring of X ray Beam

Evaluation criteria of a good AP projectionLarge abdomen- use immobilization band to compress soft tissue and reduce scatter.Beam should be collimated according to size of cassette.Ensure markers are included on cassette.If patient too ill use stationary grid and cassette is placed in tray under trolley. Lead rubber is placed under cassette to reduce grid cut off.Take Home LessonFailure to include symphysis and diaphragm on same image maybe due to large patient - two images are acquired.Failure to visualize the lateral extent of abdominal cavity due - to pt size and poor positioning.Respiratory movement un sharpness- rehearsal of breathing technique before exposure.Common Faults and RemediesPatient rotation when patient is in bed.Underexposure patient size or incorrect exposure control.Artefacts buttons or pocket contents.Grid cut off trolley or ward patients vertical central beam is at 90 degrees and cantered at middle of grid cassette.Poor image contrast: high kvp poor collimation stationary grid poor abdominal compression

Patient with back against erect Bucky legs well apart so that patient is steady.The MSP is adjusted at 90 degrees and coincident with midline of table.Pelvis is adjusted such that the ant sup iliac spines are equidistant.AP Erect Patient StandingThe cassette is placed in the Bucky tray with its upper edge at level of middle of body of sternum so that the diaphragms are included.Horizontal beam is directed so that it is coincident with the centre of the cassette in the midline.An exposure is made in full expiration.

Direction and Centering of X Ray BeamExposure factors High mA Short exposure time 7-10 kvp more than for supineIn case of suspected perforation patient should be kept erect for at least 20 mins prior to exposure to allow free gas to rise.

Notes A-p erect patient sitting.A p left lateral decubitus.Lateral dorsal decubitus.Other Common PositionsThank You