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M Prokop

Publications and source records attributed to M Prokop.

At least 73 records · Page 4Linked to original sources
PubMed1994

[Evaluation of the aorta and supra-aortic vessels with spiral CT and 3-dimensional vascular reconstruction after operation of aortic isthmus stenosis].

Aneurysm formation, restenosis, and hypertension are well known complications after surgery for coarctation of the aorta (CoA). In order to assess long-term results, 46 patients were studied by spiral computed tomography and three-dimensional reconstruction after an interval ranging from 1 to 21 years (median 10 years) after surgery for coarctation. Spiral computed tomography showed pathological changes of the aorta in the majority of patients. Typical findings were ectasy or aneurysm formation of the ascending aorta, hypoplastic aortic arch, ectasy or aneurysm formation of the supraaortic vessels, circumscript aneurysm of the descending aorta at the side of surgery, restenosis of the descending aorta and malformations and anomalies of arterial vessels. In order to initiate adequate treatment of such specific complications as restenosis, aneurysm and/or arterial hypertension, regular controls are necessary in patients after surgery for aortic coarctation. In addition to clinical examination and besides magnetic resonance imaging and angiography, spiral computed tomography is an effective non-invasive imaging method for follow-up.

Adolescent↗
PubMed1994

[Basic principles of vascular imaging with spiral CT].

Vascular investigations by CT have experienced a decisive advance and found a high acceptance since the introduction of fast volume scanning (spiral CT). We have investigated the underlying physical foundations and optimized the operational aspects of the method now introduced as CT angiography (CTA). Investigations are carried out with a table feed of 1-10 mm/s. Images are reconstructed at 1-2 mm separations by use of algorithms which optimize the layer profile. The parameters must be adapted to the region being investigated. The diagnosis is generally made with interactive cine runs; for this the original images, multiplanar reformations, 3D surface shaded displays (SSD), and maximum intensity projection (MIP) images are used. The 3D representations are discussed in the context of the principle and illustrative examples. Important applications for CTA are the evaluation of aortic aneurysms and dissections, pulmonary vessels, renal arteries, and vessel stents. CTA is characterized by short examination times, low invasiveness, and relatively low cost; in typical cases it is associated with an effective dose of 2-10 mSv. The advantages and disadvantages of the new method are discussed in terms of diagnostic value, image quality, patient dose, contrast medium techniques, and practical aspects in comparison to other angiographic methods.

Algorithms↗
PubMed1994

The Budd-Chiari syndrome: clinical presentation and diagnostic findings in 45 patients treated by surgery.

We report on the clinical presentation and diagnostic findings in 45 patients with Budd-Chiari syndrome. The diagnosis was confirmed by histology at the time of liver transplantation (n = 37) or shunt surgery (n = 8). An underlying disorder could be established only in half of the patients, oral contraceptives as predisposing factor were known in 18 cases. Clinically, abdominal pain and distension as well as hepatomegaly and ascites were most frequent findings, whereas changes in laboratory data were more or less unspecific. By use of repeated ultrasound, a definite diagnosis of a Budd-Chiari syndrome could be confirmed in all cases by obligatory demonstration of obstruction or thrombosis of at least one major liver vein. Hepatic venography revealed only one false-negative result. Celio-mesenteric arteriography plus portography, cavography and preoperative liver biopsy did not present additional diagnostic information. These techniques may contribute to treatment planning of portosystemic shunt surgery or hepatic transplantation. In conclusion, the presence of hepatosplenomegaly, ascites, abdominal pain and distension, especially in combination with a known hypercoagulable state, should alert to the possibility of a Budd-Chiari syndrome. Ultrasound is the diagnostic tool of choice. Hepatic venography should only be performed if even repeated ultrasound is not conclusive.

Adolescent↗
PubMed1994

[Unilateral left superior vena cava in absent right superior vena cava. Modern imaging diagnosis and clinical relevance].

Cardiological and radiological findings in a 64-year-old patient with persistent left superior vena cava and absent right-sided superior vena cava are described. Presence of a persistent left superior vena cava (PLSVC) is considered to be one of the most frequent anomalies of the systemic venous return. It occurs most often in association with a right-sided superior vena cava and only in rare cases with an absent or atretic right-sided superior vena cava. This malformation is often associated with other congenital heart defects, but without major hemodynamic significance. The variation may cause difficulties in venous catheterization, pacemaker electrode insertion or during cardiopulmonary bypass. The diagnosis can be confirmed by angiography, computed tomography and nuclear magnetic resonance imaging.

Diagnostic Imaging↗
PubMed1993

High incidence of aneurysm formation following patch plasty repair of coarctation.

Repair of aortic coarctation was performed in 152 adolescent and adult patients (mean age 28.5 years, range 14-67 years). Ninety patients were treated with patch plasty, 33 with end-to-end anastomosis, 18 with interposition of a tubular graft, 6 with prosthetic bypass and 5 with direct plasty. There were two (1.3%) early and ten (6.6%) late deaths after 2.9 to 11.8 (mean 6.6) years. Of the remaining 140 patients, 129 (92.1%) were reexamined with computed tomography and angiography after 1.5 to 17.2 (mean 9.1) years postoperatively. In 27 patients (35.1%) of the patch plasty group significant dilatation at the operative site was observed and reoperation for aneurysm formation was required in 15 patients (19.5%). Resection of the intimal crest did not increase the probability of aneurysm formation, whereas Dacron as patch material and late hypertension had a significant influence. Six of the ten late deaths occurred in the patch plasty group. Rupture of an aneurysm at the operative site was proved in two of these patients, and three patients died suddenly for unknown reasons. In the other groups significant dilatation was observed in 13 patients and 3 local aneurysms required reoperation (2 after end-to-end anastomosis and 1 after direct plasty). We conclude that patch plasty repair of coarctation should be abandoned in adults. End-to-end anastomosis is advisable only if possible without excessive tension. Reoperation with interposition of a tubular graft on left heart bypass proved to be a safe method.

Adolescent↗
PubMed1993

Three-dimensional vascular imaging--an additional diagnostic tool.

Angiography is still the standard for imaging of vascular structures. However, since the number of projections is limited, complex pathoanatomy may not be sufficiently visible. This study presents two patients in whom 3D reconstruction from Spiral CT data revealed combined vascular lesions undisclosed by angiography. In one case the combination of coarctation and chronic dissection type B, in another the combination of two aneurysms of the celiac trunk in series was disclosed. We conclude that 3D reconstruction can be a valuable asset in the diagnosis of complex vascular pathoanatomy.

Adult↗
PubMed1993

Improved parameters for unsharp mask filtering of digital chest radiographs.

Observer performance with four unsharp mask filtering algorithms for storage phosphor chest radiographs was compared with that with conventional screen-film radiographs in the detection of three types of simulated lung disease: nodules, fine lines, and micronodule clusters. Previously studied parameter sets (small [1.4-mm] and medium [5-mm] filter masks) and two new parameter sets (large [2.5-cm] and ultralarge [7-cm] masks) were compared by means of receiver operating characteristic analysis. With medium and small masks, nodule detection was inferior to that achieved with other modes. Use of ultralarge masks decreased the detection of lines compared with detection with conventional screen-film radiographs. Although detection of micronodule clusters was worse with digital images than with conventional screen-film radiographs, results with large and ultralarge masks were better than with small masks. Overall, filtering with large masks was best suited for simultaneously matching linear, nodular, and micronodular structures. These results suggest that lesion-specific processing of digital chest images is not necessary.

Humans↗
PubMed1993

Renal arterial stenoses: spiral CT angiography.

PURPOSE: To evaluate the role of spiral computed tomography (CT) in diagnosis of renal arterial stenoses. MATERIALS AND METHODS: In 22 patients with suspected renovascular hypertension, spiral CT angiography of the renal arteries was compared with arterial digital subtraction angiography (DSA). For each patient, the peak transit time t (from intravenous injection to maximum enhancement of the abdominal aorta) was determined with a bolus injection of 15 mL of contrast medium. Spiral scanning started at the level of the superior mesenteric artery with a delay of t + 5 seconds after the start of injection of 100-150 mL of contrast medium. RESULTS: Spiral CT angiography demonstrated multiple renal arteries in five patients. A renal artery stenosis or occlusion was found in 15 of 22 patients (22 of 54 arteries). All findings were confirmed with arterial DSA. Vessel contrast on spiral CT scans was good to excellent in 19 of 22 patients. For diagnosis, axial-section and multiplanar reformatted images were superior to three-dimensional surface reconstructions and maximum-intensity projections. CONCLUSION: Spiral CT angiography is a promising screening method for renal artery stenosis.

Adult↗
PubMed1993

[Vascular imaging with spiral-CT. The path to CT-angiography].

Spiral CT is a technique that allows for high-quality two-dimensional angiographic projections and 3D imaging of vascular structures. The authors present the technical and methodological principles of the technique, including scan parameters and parameters of contrast application for various clinical imaging tasks. They present their experience with over 150 clinical cases using spiral CT angiography. Suitable applications of this technique include congenital anomalies, aneurysms, dissections, stenoses, thrombi and vascular tumor involvement. Given a problem-adapted examination technique, pathologic changes in vessels of as little as 2 mm can be visualized. In some cases with complex vascular anatomy, spiral CT angiography can be superior to arterial angiography.

Forecasting↗
PubMed1993

Current status of the imaging modalities in the pre- and postoperative diagnostic workup of liver transplant patients.

Before transplantation, imaging procedures are mainly used to exclude factors which may serve as contraindications, render surgery difficult, or necessitate a modification of the operative technique. In addition, assessment of liver volume is necessary before segmental liver transplantation. Sonography or other cross-sectional imaging modalities are sufficient for these purposes. After transplantation, imaging is principally required in cases with suspected complications. Sonography, including Duplex and Doppler sonography, is an excellent first investigative modality for this purpose in addition to assessment of the clinical and biochemical parameters. Sonography can diagnose not only vascular complications but also biliary and infective complications; the former may also be a concealed cause of the latter. In unclear infections sonography often has to be supplemented by other modalities like CT. In equivocal cases a puncture is indicated. Invasive procedures are necessary in only selected cases, in particular when an intervention is under consideration. At present MR plays a limited role in the diagnostic workup as it rarely offers additional information except in very few cases. The early diagnosis of rejection cannot be reliably made by any of the imaging modalities and is essentially dependent on the biopsy.

Diagnostic Imaging↗
PubMed1993

The kissing balloons technique. Simultaneous dilatation of stenoses of branch arteries at the bifurcation of the renal artery.

Whereas dilatation of a single stenosis of the main renal artery is a routine intervention, a narrowing of the renal artery at its bifurcation extending into the branch arteries poses a more complex problem. The procedural risks of renal artery dilatation are compounded by the danger of occlusion of one of the branch arteries during maneuvers to dilate the other. Long-term results of surgical vascular reconstruction at a renal artery bifurcation are not satisfactory. Untreated, these stenoses lead to intractable hypertension and impairment or loss of renal function. We present a patient with hypertension and impaired function of the right kidney on account of a renal arterial bifurcation stenosis. Using a bilateral transfemoral arterial approach 2 balloon catheters were simultaneously placed into the origins of the renal artery branches and both arteries were successfully dilated by the kissing balloons technique. This method provides an elegant alternative to difficult surgery to save an endangered kidney.

Angioplasty, Balloon↗
PubMed1992

[Morgagni's hernia: diagnosis and therapy].

A 35-year-old man reported persistent exertional dyspnoea and pressure sensation over the left chest for the last six weeks. On auscultation there were diminished breath sounds over the right base. Chest X-ray demonstrated a 10 cm large ventral paracardiac shadow on the right. Computed tomography suggested a hernia of the foramen of Morgagni; persisting symptoms indicated a laparotomy. This revealed an opening of about 1.5 cm in the right substernocostal triangle through which the entire greater omentum had herniated into the thorax. The omentum was repositioned and the hernial defect closed by direct suture. The postoperative course was without complication and the patient was discharged after seven days.

Adult↗
PubMed1992

[The visibility of a central venous catheter using digital luminescence radiography in intensive care radiology].

The aim of the following study was to assess the impact of dose alterations on the detection of catheters. We compared the performance of well-exposed conventional and digital portable chest radiographs in the detection of thin catheters and tested the influences of dose alterations. Portable chest radiographs of 20 patients were obtained with conventional film/screen (FR) and with storage phosphors at 50% (SRL), 100% (SRN), and 250% (SRH) of the conventionally required exposure dose. The region of the mediastinum was subdivided into an average of 18 fields, 50% of which were superimposed with thin catheter segments. ROC analysis of 11,600 observations by 8 readers found only SRH equivalent to FR in catheter visualisation. Performance decreased significantly with SRN and SRL. Detection of low contrast catheters was found to be significantly decreased in storage phosphor radiographs obtained with standard exposure dose. A dose reduction is not feasible with current equipment if performance equivalent to conventional radiography is to be achieved.

Catheterization, Central Venous↗
PubMed1992

Impact of hard-copy size on observer performance in digital chest radiography.

To determine the impact of reduced hard-copy size on diagnostic performance of digital radiography, screen-film chest radiographs were compared with isodose digital storage phosphor radiographs in the detection of simulated nodules, fine pulmonary lines, and micronodular opacities superimposed on the chests of 10 healthy volunteers. Digital radiographs were laser-printed in a full-size conventional format and in image lengths of two-thirds, one-half, and five-elevenths of the conventional format. Eighteen thousand observations by eight radiologists were analyzed by use of receiver operating characteristics. The detectability of lines and micronodular opacities decreased with declining image format size. In the detection of micronodular opacities, only the nearly full-size digital images were equivalent to conventional images. In the detection of linear opacities, reduction of image length by one-half or more reduced performance (analysis of variance, P less than .05). Only for the detection of nodules was no major difference found.

Humans↗
PubMed1992

[Chemoembolization of hepatocellular carcinoma in cases of isolated liver involvement].

Chemoembolization is an effective treatment for hepatocellular carcinoma, giving results equally as good as surgical therapy for T2 tumours. Survival can be prolonged and side-effects can be reduced by combining Lipiodol and Gelfoam for chemoembolization, employing a modified technique, with repeated procedures, and using appropriate follow-up treatment. The toxicity of the procedure is acceptable, but it requires supportive therapy necessitating an intense interdisciplinary co-operation.

Aged↗
PubMed1991

[Digital radiography: optimization of chest radiographs using a modified exposure control].

Phototiming over the lung fields frequently compromises the signal-to-noise ratio available in the mediastinal and diaphragmatic regions of the chest. A moderate dose increase would be justified if a significant improvement in diagnostic performance could be achieved. We compared the impact of mediastinal phototiming (150 kVp, 150 cm FFD, 1.0 mm focus, 12:1 grid [higher kVp chosen to minimize dose increase]) to standard lungfield phototiming (125 kVp, 150 cm FFD, 1.0 mm focus, 12:1 grid) on the detectability of simulated pulmonary nodules (wax, 0.5-2.5 cm in diameter) superimposed on human volunteers in storage phosphor radiographs (1744 x 2144 pixels, 10 bit). ROC analysis of 1920 observations by 8 readers showed a significantly higher (p less than 0.03) detectability of simulated pulmonary nodules with mediastinal phototiming (ROC area = 0.89) than standard lungfield phototiming (ROC area = 0.84).

Humans↗