Radiographic Contrast Procedures and Radiation Safety D A Feeney DVM MS Diplomate ACVR Professor of Radiology College of Veterinary Medicine University Of Minnesota St Paul MN 55108 INTRODUCTION This discussion is a guide to special but relevant radiographic procedures that can be used in almost any private practice situation No specialized equipment is required except the option to direct the x ray beam away from the floor but don t aim it at any occupied area when using the proposed horizontal beam techniques Properly performed imaging procedures minimize surprises at laparotomy or necropsy and foster accurate diagnosis and prognosis with minimal patient discomfort and client expense A HORIZONTAL BEAM RADIOGRAPHY The object of horizontal beam radiography x ray beam directed parallel to the floor is to use the influence of gravity on fluid or the lack of gravitational influence on air to clarify findings suspected on routine recumbent lateral or VD DV views made with the x ray beam directed toward the floor without the use of contrast media The most common uses of horizontal beam radiography are a to position the patient so this fluid if it is free movable in a cavity i e pleural space may be moved away from the area of interest so regional pathology can be visualized b to position the patient so free fluid may be serially quantitated to determine if it is increasing of decreasing with less confusion than routine views NOTE if you see a flat parallel to ground fluid line there must be free air as well as free c to position the patient to permit differentiation of free fluid from trapped fluid which is usually associated with inflammatory or possibly neoplastic processes or a mass d to position the patient to determine if air seen in a cavity is free or within normal viscera B CARDIOVASCULAR RADIOGRAPHY 1 Non selective Angiogram Venogram A Contraindications dehydrated patient oliguric patient patient with history of contrast media reactions Considerations worthwhile considering use of meglumine rather than sodium cation if restricted sodium intake worthwhile using nonionic contrast media if high risk patient e g old cat critically ill patient of any species B Patient Preparation SURVEY RADIOGRAPHS No special preparation but the less stool and ingesta present the better Use sedation as necessary for adequate patient restraint within risk benefit judgment of patient s presenting problem C Contrast Media Dose Route of Administration Give 200 up to 400 mg of Iodine as sterile sodium diatrizoate or sterile sodium iothalamate CONRAY 400 per lb of body weight as a rapid intravenous bolus injection through a preplaced catheter in the cephalic vein for cranial vena cava or lateral saphenous vein for caudal vena cava Catheter should remain usable for at least 15 minutes in case of reaction to contrast media requiring venous access for fluid drug administration If you use the nonionic contrast media iohexol or iopamidol use the same mg of Iodine lb as for ionic agents Watch for thrombus formation with nonionics D Radiographic Views Filming Sequence AFTER SURVEY RADIOGRAPHS Expose radiograph usually lateral view 2 4 seconds after injection for best vena caval opacification from the respective catheter placement sites Expose radiograph 3 5 seconds after cephalic vein injection for best right heart or pulmonary artery opacification Expose radiograph 4 8 seconds after cephalic vein injection for best left heart or intrathoracic aorta opacification Wait 8 seconds for abdominal aortic studies C URINARY TRACT RADIOGRAPHY 1 Excretory Urography A Contraindications dehydrated patient oliguric patient patient with history of contrast media reactions Considerations worthwhile considering use of meglumine rather than sodium cation if sodium intake worthwhile using nonionic contrast media if high risk patient e g old cat critically ill patient of any species B C D 2 Patient Preparation SURVEY RADIOGRAPHS withhold food NOT water for 24 hours unless emergency cleansing enema at least 2 hours before radiography unless emergency don t sedate unless necessary may delay excretion phases 2 to hypotension Contrast Media Dose Route of Administration Give 400 mg of Iodine as sterile sodium diatrizoate or sterile sodium iothalamate per lb body weight as a rapid intravenous bolus injection through a preplaced cephalic vein catheter Can use meglumine or eglumine sodium cation mixtures but pyelographic won t be as good Catheter should remain usable for at least 15 minutes in case of reaction to contrast for fluid drug administration If you use the nonionic contrast media iohexol or iopamidol use the same mg of Iodine lb as for ionic agents Radiographic Views Filming Sequence AFTER SURVEY RADIOGRAPHS Expose a VD view 15 20 seconds after bolus injection expose a Lateral and VD view 5 minutes after injection expose VD oblique views also 5 minutes ectopic ureter suspects only expose a VD lateral optional 20 minutes after injection and expose a VD lateral optional 40 minutes after injection Cystography positive negative double contrast A Contraindications Don t use room air in the presence of gross hematuria carbon dioxide or nitrous oxide instead B Patient Preparation SURVEY RADIOGRAPHS withhold food NOT water for 24 hours unless emergency cleansing enema at least 2 hours before radiography unless emergency sedate as necessary 3 C Contrast Media Dose Route of Administration After emptying the bladder distend urinary bladder via aseptic retrograde catheterization of the urethra bladder until palpably turgid usually 3 5 ml lb body wt This applies to either positive use solution containing approximately 100 mg ml of Iodine as sterile diatrizoate or iothalamate or negative usually use room air see contraindications contrast studies For double contrast puddleogram studies perform negative contrast study as above but follow air etc with 1 3 ml of positive contrast media use solution containing approximately 100150 mg ml of Iodine as sterile diatrizoate or iothalamate D Radiographic Views Filming Sequence AFTER SURVEY RADIOGRAPHS Expose a lateral VD view immediately after administration expose oblique or DV opposite lateral views to clarify attached filling defects Retrograde Urethrography Distension Retrograde Urethrocystography A Contraindications Don t use room air in the presence of gross hematuria because it can cause fatal air embolism Use either carbon dioxide or nitrous oxide instead Don t use distension technique if