[Ultrasonography in primary health care--new technology of increasing use].
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Family Practice↗
Biomedical subjects
F Laerum
Publications and source records attributed to F Laerum.
From PACS to image management systems: PACS matures into a tool supporting imaging across the care continuum.
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Delivery of Health Care↗
Demand for a new main speciality in image-guided therapy.
As image-guided and minimally invasive therapy advances in complexity and volume, it becomes more obvious that none of the existing main specialities in medicine offer the ideal clinical or technological training for the responsible physicians at this time. The radiologists lack a clinical basis, and do not have adequate opportunities for proper pre- and post-procedural follow-up of their patients. The clinical doctors, i.e. cardiologists or vascular surgeons, do not have the proper technological background, or the training in 2D/3D imaging diagnostics or radiation hygiene. Radiology 'possesses' the technology, while the clinical specialities 'possess' the patients. Integrated use of various imaging modalities (fluoroscopy, computed tomography, ultrasound, magnetic resonance imaging, endoscopy or video-assisted techniques) may also be exploited more effectively for guidance and control of surgical or minimally invasive intervention. To pursue the progress and secure the quality and efficiency of future medical developments in the field, a fusion of clinical medicine and radiology into a new speciality is proposed. A basic training of 2 years in surgery or internal medicine, and 2 years of radiology can be followed by organ-wise (gastrointestinal, vascular, cardiology, etc.) subspecialisation. In this way, devastating turf battles and conflicts of interests in the hospital system may be neutralised and the traditional specialities join forces to the best of patients. Proposed terms for this new kind of specialist could be 'Clinical Surgical Radiologist', 'Clinical Cardiological Radiologist', etc., or simply 'Image-guided Therapist'.
Clinical Medicine↗
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.
Animals↗
Intestinal permeability of x-ray constrast media iodixanol and iohexol during bacterial overgrowth of small intestines in rats.
To investigate the recovery of iodinated water-soluble contrast medium from small bowel with small morphological alterations, iohexol or iodixanol was instilled through an orogastric tube in rats 14 days after surgery that established a self-filling blind loop in the jejunum. This rat model induced small bowel bacterial overgrowth with only minor abnormalities observed on histology and scanning electron microscopy. Animals with end-to-end anastomosis of the jejunum or unoperated rats served as controls. Compared with unoperated animals, urinary recovery of iohexol and iodixanol was significantly higher in both groups that underwent surgery. Moreover, the contrast medium recovery was numerically higher in the self-filling blind loop group given iodixanol than in the end-to-end anastomosis group, although not statistically significant, P = 0.09. Our results indicate that iohexol and iodixanol may detect small barrier impairments in the intestines. Iodixanol, the largest of the two, may seem to differentiate better between normal and minimally impaired intestinal barrier.
Animals↗
Selective venous thrombolysis with the nipple-balloon catheter: comparative evaluation in vivo.
PURPOSE: To compare in an animal model of deep vein thrombosis, an intramural drug delivery catheter, the nipple-balloon catheter, with an occlusion balloon-infusion guide wire system. MATERIALS AND METHODS: Ten juvenile pigs were used for the study. Deep vein thrombosis was induced in both hind limbs by using a previously described technique. Heparin was administered 30 minutes later (2,500 IU intravenously) and bilateral thrombolysis was attempted with use of 8 mg of alteplase as a 0.25 mg/mL solution containing heparin 50 IU/mL (n = 10) and sodium/meglumine ioxaglate 40 mgI2/mL (n = 5). In one limb, the external iliac vein was endoluminally occluded, and 0.8 mL of alteplase was administered every 3 minutes through a multisideport infusion wire placed coaxially through the balloon catheter. On the other side, a nipple-balloon catheter was used: alteplase was injected as two 0.4-mL aliquots every 3 minutes in overlapping segments of the vessel. Blood samples were taken at predetermined intervals to determine the partial thromboplastin time and plasma fibrinogen concentration. At autopsy, the thrombus mass in the iliofemoral veins was measured, and the extent of residual thrombosis in the venous tributaries was graded at four sites. The heart and the lungs were also examined for thromboemboli (n = 5). Venous specimens were then subjected to X-ray fluorescence spectrometry to determine iodine content (n = 5). RESULTS: Bilateral thrombolysis could be successfully completed in all animals. No procedural problem associated with the use of the nipple-balloon catheter was encountered. The mass of residual thrombus in the axial veins was significantly lower in this group (P = .005). The drug delivery system used did not appreciably influence thrombolysis in the tributaries. Signs of macroscopic damage to the veins were not observed in any animal. None of the venous specimens had detectable levels of iodine. Small thromboemboli were found in the pulmonary circulation in three of five animals. Fibrinogen levels did not decrease during the procedure. CONCLUSIONS: The significantly lower residual thrombus burden associated with use of the nipple-balloon catheter suggests that the device may have the potential to be an effective delivery system for selective thrombolysis in veins.
Animals↗
In vivo evaluation of the adjustable temporary venous spring filter and the RF02 temporary filter: comparative study.
RATIONALE AND OBJECTIVES: The authors performed this study to compare the in vivo efficacies of the temporary venous spring filter and the RF02 filter in an animal model. MATERIALS AND METHODS: Either the spring filter or the RF02 filter was placed in the inferior vena cava of 10 pigs each, and two clots (5 x 20 mm) were funneled into the filters at 1-hour intervals. The second clots were funneled without removing the first clots captured by the filters. Clot-trapping ability, caval occlusion associated with the clot-trapping procedure, arterial blood gas concentrations, and changes in arterial and iliac venous pressures were evaluated. RESULTS: Placement of the RF02 filter caused elevation of iliac venous pressure with a maximum of 2.2 mm Hg (median) (n = 13, P = .003). Placement of the spring filter parallel to venous flow enabled capture of 90% (nine of 10) and 100% (six of six) of the first and second clots, respectively. The RF02 filter captured clots consistently. The difference between filters was not statistically significant. Both filters equally contributed to elevation of iliac venous pressure (median, 9.3 and 7.2 mm Hg [n = 9] with the spring filter and RF02 filter, respectively). Caval occlusion occurred in 17% (one of six) and 67% (six of nine) of animals after two clots were trapped in the spring filter and RF02 filter, respectively (P = .06). Other parameters were not influenced by the clot-trapping procedure. CONCLUSION: Although a larger version should be developed and better stability of the filter is needed, the spring filter proved to be an efficient filtering device and had a lower rate of caval occlusion compared with the RF02 filter.
Animals↗
Transcatheter aspiration: the key to successful percutaneous treatment of deep venous thrombosis?
RATIONALE AND OBJECTIVES: The purpose of this study was to examine transcatheter aspiration as an adjunct to local thrombolysis in a porcine model of acute deep venous thrombosis (DVT). MATERIALS AND METHODS: DVT was induced in both hind limbs of five pigs. Thirty minutes later, bilateral thrombolysis was performed by using infusion guidewires placed coaxially through occlusion balloon catheters. A temporary venous filter was then placed in the inferior vena cava. The balloon catheters and infusion wire were removed, a 14-F sheath was placed on the right side, and aspiration of residual thrombi was attempted with 8- and 6-F catheters. At autopsy, the mass of any thrombus in the iliofemoral veins was measured, and residual thrombosis in the venous tributaries was graded at four sites. Thromboemboli in the inferior vena cava and the pulmonary circulation were also collected and weighed. RESULTS: With aspiration and lysis, the iliofemoral veins were cleared of thrombus in three of five limbs; from the remaining two, only 0.09 and 0.15 g of thrombus were harvested. Except for the deep femoral vein in two legs, tributaries were free of thrombus. After thrombolysis alone, thrombi ranged in mass from 0.54 to 1.14 g (median, 0.70 g). Some thrombi were observed in most tributaries. One or two small emboli were found trapped by the caval filter and in the pulmonary circulation in four and three pigs, respectively. CONCLUSION: The primary axial veins and their tributaries can be rapidly cleared of thrombus by using thrombolysis with transcatheter aspiration, but this procedure is associated with the risk of pulmonary embolism.
Acute Disease↗
Placement of a spring filter during interventional treatment of deep venous thrombosis to reduce the risk of pulmonary embolism.
PURPOSE: To assess the efficacy of the Spring filter during interventional treatment of deep venous thrombosis in vivo. MATERIAL AND METHODS: A model of inferior vena cava thrombosis was used. Part I: The thrombus was treated by the pulse-spray technique (PT) (urokinase 250,000 IU; n=7) or a rotatory basket catheter, Thrombolizer (MT) (activated with compressed air at 7 atm; n=5). Part II: Following placement of a Spring filter, the animal underwent PT (n=5) or MT (n=5). Based on the results of part I, the treatment protocol was modified (PT, urokinase 500,000 IU; MT, compressed air at 8 atm). Embolus volumes trapped by the filter and found in the lungs were calculated and the filtering efficacy quantified. RESULTS: Part I: Pulmonary emboli (1 to 4 mm in diameter) were observed in 3 animals in the PT group and 1 animal in the MT group, respectively. Median reduction in thrombus volume was 21% and 4% by PT and MT, respectively. Part II: In the PT group, 58% and 100% of the total embolus load was trapped in 2 animals, while the filter failed to trap emboli (1 to 1.5 mm in diameter) in 1 animal. In the remaining 2 animals, no embolus was found trapped by the filter or in the lungs. In the MT group, 55 97% (median 83%) of the embolus load was trapped. Emboli found in the lungs did not exceed 4 mm in diameter. CONCLUSION: Preceding interventional treatment of venous thrombosis with placement of the Spring filter reduced the embolic burden on the lungs.
Angiography↗
Quantitative evaluation of selective thrombolysis techniques: influence of catheter characteristics and delivery parameters.
Here, we evaluate in vitro the site-specific delivery ability of thrombolysis catheters and compare continuous infusion (CI) and periodic injection (PI) protocols with reference to this parameter. Thrombotic occlusion was simulated by placing a porcine blood clot proximal to an eccentric stenosis in a flow phantom. Iodinated contrast agent was used as the marker. Part I-Evaluation of thrombolysis catheters: four CI and three PI catheters were tested. The marker was delivered as an infusion at 1 ml/min for 1 min (CI), or as two 0.25 ml boluses 30 sec apart (PI). Iodine content of the clot was then estimated with x-ray fluorescence spectrometry. This value as a ratio of the delivered dose was defined as the targeting efficiency. Part II-Evaluation of thrombolysis protocols: CI and PI were compared. The marker was delivered for 3 or 5 min using one of seven protocols. The iodine content of both clot and effluent were estimated. Among PI catheters, the Jet-Lysis catheter proved to be the best (P = 0.02). The EDM catheter had the lowest targeting efficiency in the CI group (P = 0.01). With CI, median iodine recovery dropped from 0.21 (95% confidence interval: 0.08, 0.25) for 1 min to 0.13 (0.05, 0.16) for 3 min and 0.07 (0.03, 0.10) for 5 min; for PI the values remained unchanged. The fraction lost in the effluent increased with the duration of regimen with both CI (P = 0.014) and PI (P = 0.004). Reducing the rate of infusion or the bolus frequency resulted in major improvements with respect to this parameter (P = 0.005). For CI, the targeting efficiency increased as well (P = 0.03). We conclude that currently used thrombolysis protocols do not fully exploit the delivery advantage offered by CI or PI. Fortunately, simple modifications offer the possibility of overcoming these drawbacks.
Animals↗
In vitro function of an adjustable temporary venous spring filter: comparison with the temporary RF02 filter and the permanent Greenfield vena cava filter.
RATIONALE AND OBJECTIVES: The authors compared in vitro function of a temporary venous spring filter with that of a temporary RF02 filter and a permanent Greenfield filter. MATERIALS AND METHODS: All three types of filters were placed in thin polyethylene tubes (diameters, 10.0-18.0 mm). Physiologic saline was substituted for flowing blood, and blood clots of three sizes (6 x 10 mm, 6 x 20 mm, 9 x 20 mm) were funneled to the filters. Clot-trapping ability of each filter and elevation of intraluminal pressure after clot trapping were assessed for each tube size. RESULTS: No statistically significant elevation in intraluminal pressure was detected immediately after placement of any filter. The clot-trapping ability of the spring filter and of Greenfield filter were slightly lower than that of the RF02 filter, but the differences were not statistically significant. After filters had trapped large clots, a high pressure gradient was detected in the 10.0-mm tube for all filters. The spring filter was associated with a higher pressure than the other filters in the 12.0-mm tube (P < .05). CONCLUSION: In vitro function of the spring filter was satisfactory in comparison with that of the RF02 filter and the Greenfield filter. For efficient filtering in the inferior vena cava, development of a larger version of the filter may be necessary.
Equipment Design↗
[The intervention center at the Rikshospital. Experiences from the first year of activity].
In order to co-ordinate and promote the development of new clinical applications by structuring collaboration and communication across traditional specialty boundaries, a first of its kind hospital department was opened at Rikshospitalet in June 1996. The Interventional Centre is a multidisciplinary centre for research and development, teaching and quality management of imaging-guided minimally invasive therapy, endoscopic surgery and interventional radiology. The department is a full fusion of state-of-the art operating theatre with an advanced radiology department and with fully up-to-date ultrasound and endoscopy facilities for integrated use in the treatment of the patient. The department is cross-disciplinary organised. A small staff of 14 persons are responsible for the day-to-day running of the centre. Specialists from other hospital departments work together with the centre's permanent staff to develop new procedures. During the first year, 19 research projects were started and a total of 510 procedures performed within the fields of Radiology, Neurosurgery, Gastroenterology, Cardiology, Cardiovascular surgery and Paediatric cardiology, and also within the fields of image processing and telecommunication.
Centralized Hospital Services↗
Adjustable temporary venous spring filter: in vitro assessment.
RATIONALE AND OBJECTIVES: The authors performed an in vitro study to evaluate a temporary venous spring filter that can extend vessels of a wide range of diameters to a slit-shaped canal. MATERIALS AND METHODS: Filters were placed in thin polyethylene tubes or in porcine inferior vena cava specimens (diameter, 10.0-16.0 mm). Physiologic saline was substituted for blood flow, and blood clots of three sizes (6 x 10, 6 x 20, and 9 x 20 mm) were funneled to the filter. Clot-trapping ability was assessed by the degree of luminal extension. RESULTS: When the luminal extension was increased from 2.6r to 2.8r (where r is the original radius of the vein models), clot-trapping ability increased significantly (61.1%-87.5% in polyethylene tubes and 15.8%-77.5% in venous specimens, P < .001). When the luminal extension was increased to 3.0r, more than 90% of the clots were trapped in all tubes. After trapping the small, medium, and large clots, mean intraluminal pressure elevation was 1.0, 1.0, and 17.0 cm of saline, respectively. CONCLUSION: Despite its simple design, the spring filter proved to be an efficient filtering device.
Animals↗
Cost-benefit considerations in establishing a multidisciplinary center for minimally invasive therapy (interventional clinic).
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Cost-Benefit Analysis↗
The X-ray contrast medium iodixanol detects increased colonic permeability equally well as 51Cr-labeled ethylenediaminetetraacetic acid in experimental colitis of rats.
BACKGROUND: Non-ionic, water-soluble radiographic contrast media have been suggested as intestinal permeability probes. We studied the permeability of the isosmolar contrast medium iodixanol and 51Cr-labeled ethylenediaminetetraacetic acid (EDTA) from the non-perforated colon after induction of colonic inflammation. METHODS: Colonic inflammation and ulcerations were induced by luminal colonic instillation of trinitrobenzenesulfonic acid, dissolved in 40% ethanol. Controls received saline. Fourteen days later iodixanol, 320 mg I/ml, and 51Cr-EDTA were given as an enema. Urine was collected for the subsequent 6 h and subjected to high-performance liquid chromatography and gamma activity counting. RESULTS: Urinary recovery of iodixanol and 51Cr-EDTA increased gradually with severity of the colonic inflammation. The correlation between iodixanol and 51Cr-EDTA recovery was strong (corr.coeff = 0.97). CONCLUSIONS: Iodixanol shows as good properties as 51Cr-EDTA when used as intestinal permeability probe in the inflamed and ulcerated rat colon. Use of the radiopaque properties of iodixanol enable intestinal probe exposure registration by film or fluoroscopy.
Animals↗
Intestinal permeability measurements - a new application for water soluble contrast media?
The detection and quantification of altered intestinal barrier function (intestinal permeability) have been addressed frequently during the last year, but the tests available for determination of intestinal permeability are both flawed and have limitations. The new water-soluble roentgen contrast media (CM) of low- and iso-osmolar type have been proposed as intestinal permeability probes. In this article this possible new application for water-soluble CM is discussed in terms of their inherent properties and the experimental and clinical results obtained so far. The 2 iso-osmolar dimers, iodixanol (Visipaque) and iotrolan (Isovist), seem to be as good as the well-documented radio-labeled permeability probe (51)Cr-EDTA in detecting injury of the intestinal mucosal barrier. The CM offer the advantage of allowing direct control of bowel wall exposure with the aid of fluoroscopy. Current permeability probes lack this quality. Iodine-containing substances may be analyzed by the rapid, simple and reliable X-ray fluorescence technique, which is suitable for application in routine clinical practice. We conclude that the new water-soluble roentgen CM have properties which may be of use in the diagnosis and quantification of altered intestinal barrier function.
Animals↗
Increased intestinal permeability for the isosmolar contrast medium iodixanol during small-bowel ischaemia in rats.
BACKGROUND: Intestinal ischaemia may be difficult to recognize in the early stages. Increased urinary recovery of water-soluble contrast medium during and intestinal follow-through has been suggested as a sign of bowel ischaemia. METHODS: Urinary excretion of the isosmolar water-soluble X-ray contrast medium iodixanol was measured after instillation via an orogastric tube in 56 rats with occlusion of the mesenteric blood vessels. RESULTS: Mesenteric venous occlusion caused only minor histologic alterations of the mucosa. High-performance liquid chromatography (HPLC) and X-ray fluorescence analysis measured urinary iodixanol concentrations 10 and 13 times higher than in the groups with mesenteric arterial occlusion than in controls (p < 0.001), and 3 and 4 times higher than in the group with venous occlusion (p < or = 0.05). Correlation between HPLC and X-ray fluorescence measurements of contrast medium in urine was strong (r = 0.98). CONCLUSION: Measuring urinary contrast medium levels during intestinal follow-through may aid in distinguishing bowel ischaemia following mesenteric arterial occlusion from mesenteric venous occlusion and from the normal bowel.
Animals↗
Coronary angioplasty using a low osmolar nonionic contrast medium. A retrospective angiographic and clinical evaluation.
This study was performed to investigate the occurrence of acute angiographic and clinical complications following PTCA using a low osmolar nonionic contrast medium. Five hundred consecutive PTCA procedures were analyzed retrospectively. The incidence of acute in laboratory complications during PTCA as well as complications occurring during the hospital stay 24 to 48 hours after the procedure were recorded. Occlusion of the dilated artery or a side branch was observed in 19 (3.8%) of the procedures, major dissection in 34 (6.8%), and thrombus in 14 (2.8%). One patient died, 6 (1.2%) required emergency coronary artery bypass grafting (CABG), 4 (0.8%) required an emergency PTCA, and 7 (1.4%) suffered myocardial infarction (MI). Our results show that angiographic findings of thrombus, major dissection and occlusion were serious conditions that related to the clinical complications MI, emergency CABG and re-PTCA. Patients with unstable angina were risk patients for both angiographic and clinical complications. Low rates of intraarterial thrombus formation and coronary artery occlusion indicate good angiographic technique and anticoagulant and antiplatelet medication.
Angioplasty, Balloon, Coronary↗