Frode Laerum

Water-soluble contrast media in radiography of small bowel obstruction: Comparison of ionic and non-ionic contrast media

Fifty patients with possible gastrointestinal obstruction, referred for enteric follow-through examination, were randomized for a double-blind, parallel comparison of the hyperosmolar contrast medium Gastrografin and the low-osmolar Omnipaque. The result was that Omnipaque retained its radiographic density in the small bowel better than Gastrografin. Omnipaque was thus a better alternative than Gastrografin in follow-through examinations of intestinal obstruction. Also, 23 patients out of 28 with small bowel obstruction due to peritoneal adhesions, had spontaneous relief of symptoms during the observation period following contrast medium ingestion with no significant difference between the two media. This indicated that enteric follow-through procedures may have a therapeutic efficacy similar to the treatment of small bowel obstruction using nasogastric suction and gastrointestinal rest. Possible mechanisms for this action of the contrast media are discussed.

Truly hybrid interventional MR/x-ray system: Investigation of in vivo applications

RATIONALE AND OBJECTIVES The purpose of this study was to provide in vivo demonstrations of the functionality of a truly hybrid interventional x-ray/magnetic resonance (MR) system. MATERIALS AND METHODS A digital flat-panel x-ray system (1,024(2) array of 200 microm pixels, 30 frames per second) was integrated into an interventional 0.5-T magnet. The hybrid system is capable of MR and x-ray imaging of the same field of view without patient movement. Two intravascular procedures were performed in a 22-kg porcine model: placement of a transjugular intrahepatic portosystemic shunt (TIPS) (x-ray-guided catheterization of the hepatic vein, MR fluoroscopy-guided portal puncture, and x-ray-guided stent placement) and mock chemoembolization (x-ray-guided subselective catheterization of a renal artery branch and MR evaluation of perfused volume). RESULTS The resolution and frame rate of the x-ray fluoroscopy images were sufficient to visualize and place devices, including nitinol guidewires (0.016-0.035-inch diameter) and stents and a 2.3-F catheter. Fifth-order branches of the renal artery could be seen. The quality of both real-time (3.5 frames per second) and standard MR images was not affected by the x-ray system. During MR-guided TIPS placement, the trocar and the portal vein could be easily visualized, allowing successful puncture from hepatic to portal vein. CONCLUSION Switching back and forth between x-ray and MR imaging modalities without requiring movement of the patient was demonstrated. The integrated nature of the system could be especially beneficial when x-ray and MR image guidance are used iteratively.

Multiple Emboli and Filter Function: An in Vitro Comparison of Three Vena Cava Filters!

PURPOSE To establish the influence of number of emboli on the trapping ability of vena cava filters in vitro. MATERIALS AND METHODS Three filters, the titanium Greenfield, Vena Tech-LGM, and Günther Tulip retrievable, were studied with use of 20- or 26-mm-diameter tubes to simulate the inferior vena cava. In the first protocol, five small (4 x 20-mm) or medium (6 x 10-mm) emboli were delivered in sequence, and the fate of each was recorded. In the second protocol, medium or large (6 x 30-mm) clots were sequentially introduced until filter occlusion occurred or 50 clots had been delivered. RESULTS For the first protocol, 82% of first small clots and 60% of second clots were trapped in 20-mm tubes (P = .001) and 63% and 45%, respectively, were trapped in 26-mm tubes (P - .02). With medium clots, the proportion trapped also dropped significantly with ascending clot rank. In the second protocol the proportion of clots captured was invariably higher for the first 10 clots (P < .001 for all combinations of covariables). CONCLUSION Filter function deteriorates with number of emboli delivered, irrespective of embolus size and simulated vein caliber.

The acquisition of skills in interventional radiology by supervised training on animal models: a three-year multicenter experience.

ConclusionsThese training courses, which have been going on for 3 years, have shown us that using an animal model for such training is an efficient way to teach the techniques. All radiology departments with animal research facilities can make use of this approach to train their own interventional radiologists and to assist in training those from institutions without such facilities.By refining our techniques we hope to reduce the high complication rate that inevitably accompanies the initial performance of new procedures. Moreover, clinicians will gain confidence in the ability of radiologists.Our courses have provided young radiologists with the opportunity to learn new techniques and improve their skills in interventional techniques. Once resistance to the use of animals for training is overcome, these physicians can be more actively involved in starting projects on their own and will feel encouraged to do so.

Ultrasound ‘electronic vivisection’ in the teaching of human anatomy for medical students

Abstract Real-time ultrasound (US) was evaluated as a tool for medical students to learn human anatomy by examining each other. Second-year students participated. US was regarded as a useful tool for anatomy studies by 95.7% of the students. Thus, real-time US seems to be a helpful tool for learning about human anatomy. This may give increased knowledge both in anatomy and ultrasonography, skills the students may benefit from in their professional life.

Cytotoxic Effects of Six Angiographic Contrast Media on Human Endothelium in Culture

Human endothelial cells in cultures derived from the veins of fresh umbilical cords were incubated for 24 hours with angiographic contrast media added to the cell culture medium. The cells were preincubated with Na2(51Cr)O4 for subsequent 51Cr-release test. Four different concentrations of the contrast media were used. Cell toxicity as judged by measuring the release of 51Cr was, in decreasing order, as follows: Sodium/meglumine diatrizoate, meglumine metrizoate, ioxaglate, iopamidol, metrizamide, iohexol. The highest concentration of sodium/meglumine diatrizoate (Urografin) led to 99 per cent cell death after 24 hours, while the same concentration of iohexol (Omnipaque) induced about 40 per cent cell lysis. The assay system with human endothelial cells thus seems to be useful for evaluation of the toxicity of contrast media. The osmolality was measured in all the solutions. Hyperosmolality accounted for a major part of the cell toxicity, but additional toxic effects of the substances were observed. The strongest osmolality-independent toxic effect was caused by ioxaglate.

Water-soluble contrast media in radiography of small bowel obstruction

Fifty patients with possible gastrointestinal obstruction, referred for enteric follow-through examination, were randomized for a double-blind, parallel comparison of the hyperosmolar contrast medium Gastrografin and the low-osmolar Omnipaque. The result was that Omnipaque retained its radiographic density in the small bowel better than Gastrografin. Omnipaque was thus a better alternative than Gastrografin in follow-through examinations of intestinal obstruction. Also, 23 patients out of 28 with small bowel obstruction due to peritoneal adhesions, had spontaneous relief of symptoms during the observation period following contrast medium ingestion with no significant difference between the two media. This indicated that enteric follow-through procedures may have a therapeutic efficacy similar to the treatment of small bowel obstruction using nasogastric suction and gastrointestinal rest. Possible mechanisms for this action of the contrast media are discussed.

Water-soluble contrast media compared with barium in enteric follow-through. Urinary excretion and radiographic efficacy in rats with intestinal ischemia.

The local effects and radiographic efficacy of four water-soluble contrast media, barium and saline were evaluated in 91 anesthetized rats with a ligature applied to the anterior mesenteric artery and vein via laparotomy. The rats were observed for 8 hours after instillation of 3 mL of test substance via oro-gastric tube. Radiographs were taken after 1, 4 and 8 hours of observation. After 8 hours, the intestines were weighed, a biopsy was done for light microscopy, and blood and urine were sampled for testing. The roentgen contrast media caused dehydration and increased influx of fluid into the small bowel lumen in proportion to their osmolality. They diluted the bowel contents, enhanced their progression and distended the bowel walls. The diagnostic qualities of radiographic films were better using the new, low-osmolal contrast media than using either barium or sodium diatrizoate. The water-soluble contrast media were excreted in the urine, as demonstrated by dense opacification of the urinary bladder on abdominal films, and increased iodine concentrations at x-ray fluorescence analysis of the urine. This may be useful clinically in detecting bowel ischemia.

Induced Thrombosis in the Pig Inferior Vena Cava: A Model of Deep Venous Thrombosis

PURPOSE To establish a new animal model of deep venous thrombosis. MATERIALS AND METHODS Fifteen young pigs underwent temporary interruption of the inferior vena cava (IVC) below the entry of the right renal vein by means of either a silicone band (surgical technique, n = 6) or an intraluminal balloon catheter (endovascular technique, n = 9), followed by injection of absolute ethanol. Lumbar veins within 3 cm below the obstruction were ligated or occluded interventionally. The iatrogenic caval obstruction was relieved after 2 days. RESULTS Procedure-related mortality was 33% (n = 2) and 11% (n = 1) for the surgical and endovascular groups, respectively. An adherent, occlusive thrombus was found in all four of the remaining surgically treated animals and in six of eight animals treated percutaneously. The IVC remained patent in two animals in whom balloon migration occurred. Severe caval stenosis invariably occurred after surgical banding. CONCLUSION IVC thrombi suitable for the study of various recanalization therapies can be reliably created with this pig model.

WATER-SOLUBLE CONTRAST MEDIA COMPARED WITH BARIUM IN ENTERIC FOLLOW-THROUGH Local effects and radiographic efficacy in rats with simple obstruction of the small bowel

The local effects and radiographic efficacy of 4 water-soluble contrast media, barium and saline were evaluated in 86 anaesthetized rats with the distal ileum ligated. The rats were observed for 8 hours after instillation of 3 ml of the test substance via orogastric tube. Radiographs were taken after 1, 4 and 8 hours of observation. After 8 hours the intestines were weighed and biopsied for light microscopy, and blood and urine were sampled for testing. Sodium diatrizoate caused increased fluid influx to the bowel lumen and, like barium, provided poorer radiographic images as compared with iohexol, ioxaglate or iodixanol. Barium showed slower progression through the small bowel than the other agents, while sodium diatrizoate was the most rapidly progressing contrast medium and caused the greatest distension. Correlation to osmolality was obvious. No significant morphologic effects on the small bowel mucosa were seen in any of the groups. Low-osmolar, water-soluble contrast media may have prospects for clinical use in patients with suspected small bowel obstruction.