E. Rinast

Non-absorbable fat-dense oral contrast agent for abdominal computed tomography

Opacification of the gastrointestinal tract for CT scanning is usually achieved by oral administration of a diluted iodine solution or barium suspension. As high-density contrast agents often cause image degrading artifacts, we investigated the value of a paraffin-methylcellulose emulsion as an oral CT scanning agent. Diseases of the intestinum were clearly outlined with paraffin emulsion, and image degrading artifacts were virtually not encountered.

Initial clinical experience with a new pulsed dye laser device in angioplasty of limb ischemia and shunt fistula obstructions

Selective plaque ablation with laser radiation at 405-530 nm in vitro has been reported. We investigated the possibilities of a new pulsed dye laser device for in vivo recanalization of arteries in ischemic lower limbs and stenoses/occlusions of arterio-venous hemodialysis shunt fistulae. A specially designed 9F or 7F multifiber catheter was used for treatment of 10 patients with lower limb artery obliterations and 11 patients with malfunctioning hemodialysis access fistulae (HAF). The recanalization technical success was 5/5 in the iliac arteries (IA), 4/5 in the superficial femoral arteries (SFA), and 11/11 in the HAF. Early re-occlusions occurred in one SFA and one IA, respectively, caused by very bad run-off. There was one clinically insignificant SFA perforation. Additional balloon angioplasty was considered necessary in 10/16 lesions. Mean ankle-arm index increased from 0.68 to 0.97. With two exceptions all HAF patients were re-integrated in the dialysis program. Pulsed dye laser angioplasty promises to be an effective and fast method for plaque ablation/debulking. The first clinical experience confirms previous in vitro results. In particular laser recanalization may become the method of choice for treatment of rigid HAF obstructions and it seems to be superior to vascular surgery or balloon angioplasty alone.

Neural network approach for computer-assisted interpretation of ultrasound images of the gallbladder

Multi-formatted films of 90 ultrasound examinations of the gallbladder (stones 56 cases, sludge 20 cases, hydrops five cases, normal gallbladder nine cases) have been digitalized and stored in a personal computer. Image data of each examination was processed to extract a 19-dimensional vector that represents the essential diagnostic information of each examination. This vector was evaluated by three different classification algorithms: (1) classical nearest neighbor principle, (2) classical linear discriminant analysis, (3) multilayered backpropagation neural network. The correct classification rate was 64% (58/90) for the nearest neighbor principle, 97% (87/90) for the linear discriminant analysis, and 99% (89/90) for the backpropagation neural network. We conclude that, (1) automated classification of ultrasound images is possible for limited diagnostic problems, (2) a neural network approach can be used successfully for that goal, and (3) the efficiency of the more flexible neural network approach is comparable to large-scale classical methods.

Angiography and angioscopy with injector-applied carbon dioxide

In 10 laboratory swines we investigated an automatic gas injector for angiography and angioscopy that allows the reproducible injection of variable quantities of gas, with variable pressure and injection times. With small volumes of carbon dioxide (CO2; 10–50 cc; 850–1250 mbar application pressure) a column of gas can be created, which facilitates digital subtraction angiography comparable to conventional contrast media (CM) or an angioscopy within a sufficiently bloodless visual field. A total of 93 of 127 angiographies of the abdominal aorta and 49 of 57 angiographies using CO2 were successful. A lack of success was obtained in selective angiographies. The use of injector-controlled CO2 application is an alternative for angiography in patients who are at increased risk using conventional CM. This technique was an unexpectedly excellent method of performing a renal venogram as well as a fast splenoportogram. Petcutaneous transluminal CO2 angioscopy affords a bloodless inspection of the aorta and side branches for a period of several minutes.

The value of computed tomography and ultrasound in cases of inflammatory aneurysms of the abdominal aorta

In a retrospective study 344 CT examinations of patients with suspected aneurysms of the abdominal aorta were evaluated with respect to the inflammatory character of the aneurysm. In 207 cases surgical therapy was conducted. In 144 of those 207 cases preoperative ultrasound examination results were also available. Frequency of inflammatory aneurysms, as classified by CT, was 10.2% (35/344) and in the subgroup of surgically treated aneurysms, 14.0% (29/207). Sensitivity and specifity of CT to realise the inflammatory type of aneurysm was 86.2% and 97.2%. The respective figures for ultrasound examinations on the basis of 144 surgically treated aneurysms were 26.1% and 100%. We conclude that even in cases of sonographically unequivocal abdominal aneurysms CT should be performed because ultrasound is not sufficiently sensitive to realise an inflammatory character of the aneurysm, which can have great impact on surgical strategy.

Follow-up study of renal transplants by duplex Doppler and gray-scale ultrasound

In the early postoperative period after renal transplantation 388 follow-up ultrasound examinations were performed in 77 patients. Over a period of 18 months standardized duplex indices (resistive index, pulsatility index) and gray-scale parameters (parenchyma/sinus index; medulla/cortex index) were sampled. These data were correlated retrospectively with clinical and pathological diagnoses. To delineate the individual course of duplex and gray-scale indices during different transplant diseases we created a new parameter: the MID (maximal index difference) which is a result of the difference between the highest index during the phase of renal dysfunction and the lowest index during the phase of normal renal function. This MID, calculated for duplex indices and for the parenchyma/sinus index, indicated significant differences in the behavior of renal transplants during the four main diseases: interstitial rejection, vascular rejection, acute tubular necrosis and Cyclosporine A nephrotoxicity. Using the MIDs, a table of cut-off values was established, which enables to differentiate retrospectively these four transplant complications with a sensitivity of 84% and specificity of 81%. In our opinion consequent follow-up examinations with duplex and gray-scale sonography should be performed, enabling sonography to become a helpful diagnostic instrument in the monitoring of renal transplants.

Bilateral renal embolization as a therapy in proteinuria

In patients with nephrotic syndrome and life-threatening protein loss resistant to therapy, a percutaneous transfemoral kidney ablation can be performed as a last measure. In three patients, one with membrano-proliferative glomerulonephritis and two with amyloidosis, a bilateral renal artery embolization was able to terminate proteinuria successfully. Nevertheless, one patient died 14 days later because of septicaemia and sepsis, due to prolonged loss of gamma globulin. The other two patients survived, although for permanent haemodialysis. In life-threatening desperate situations, catheter-aided renal embolization is a fast and effective alternative to nephrectomy.

Insufficient hemodialysis access fistulas: 18 months' experience in laser-supported dilation

Patients with end-stage renal failure disease frequently develop venous stenoses or occlusions in their hemodialysis access fistulas caused by intimal fibrosis. A complete dilation with high pressure balloons up to 20 atm may be unsuccessful in those cases. We investigated two new pulsed dye laser devices for the ablation of obstructions, which were not adequately treatable with a previous balloon angioplasty. From November 1990 to April 1992 a total of 154 percutaneous transluminal angioplasties (PTAs) of hemodialysis access fistulas were performed. In 23 of them an additive laser angioplasty was necessary. Twenty patients with Cimino fistulas presented 28 stenoses and two occlusions, and three Goretex loops presented all occlusions. Two pulsed dye laser devices emitting at 504 nm and 595 nm wavelength were tested. Technical success was achieved in 22/23 cases, but clinical success was obtained in 20/23 patients because two early reocclusions caused by thrombosis appeared. Five restenoses occurred 2, 3, 10, and in two cases 14 months after angioplasty with a mean follow-up period of 13.5 (5-18) months. Pulsed dye laser ablation in hemodialysis access fistula lesions due to intimal fibrosis is a valuable enrichment of radiological recanalization techniques and an alternative to surgery if stand alone balloon PTA fails.

Combined laser and balloon angioplasty of venous obstructions in patients with insufficient hemodialysis access fistulas

In 19 patients with insufficient hemodialysis access fistulas combined laser and balloon angioplasty of two occlusions and 17 stenoses of the shunt vein was performed. In 13 of those 19 cases the procedure was preceded by balloon angioplasty, which was insufficient because of resistant subintimal fibrosis. After using the pulsed dye laser a complete dilatation was possible in all cases.The new method is a valuable addition to percutaneous interventional techniques in patients with shunt problems, and better long term results may be expected in selected cases.

Brisant — Ein System zur Analyse von Hirntumoren in multispektralen MR-Bildfolgen

In der neuroradiologischen Diagnostik von Hirntumoren werden MR-Bildfolgen mit unterschiedlichen Gewebekontrasten generiert. Diese bilden die Basis fur das Analysesystem Brisant (Brain Image Sequence ANalysis Tool). Brisant umfast Komponenten zur Vorverarbeitung (Korrektur von Intensitatsinhomogenitaten, Registrierung) und zur automatischen Segmentierung von Gewebestrukturen (gesunde Hirnsubstanz, Hirntumor) sowie Merkmalsextraktionsverfahren zur Quantifizierung bildmorphologischer Eigenschaften von vier haufig auftretenden Hirntumorarten. Eine relationale Datenbank speichert die berechneten Merkmale gemeinsam mit der zugehorigen Diagnose. Die Datenbank umfast aktuell die Analyseergebnisse von 51 Hirntumoren. Bei der Analyse eines neuen Falles ermoglicht Brisant die Suche nach ahnlichen, in der Datenbank gespeicherten Fallen und einen Diagnosevorschlag durch eine automatische Tumorklassifikation.