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M Prokop

Publications and source records attributed to M Prokop.

At least 37 records · Page 2Linked to original sources
PubMed1997

Digital image processing.

The image quality of a radiograph is determined by the local contrast, spatial resolution, latitude and the image noise. The goal of digital processing is to improve the visualisation of pathology by optimising these physical parameters. Processing parameters need to be chosen correctly in order to overcome the inverse relationship between contrast and latitude while producing images that retain a conventional appearance. Unsharp mask filtering (UMF) is a simple technique for improving image quality. This technique, however, suffers from serious drawbacks, such as the suppression of pathologic lesions or artifacts that may simulate pathology. Manufacturers have developed different approaches in order to overcome problems and artifacts derived from this technique.

Artifacts↗
PubMed1996

[Spiral CT of the lung. Technique, findings, value].

Spiral CT allows for examination of the whole chest within a single breathhold. As compared to standard CT, spiral CT has an increased sensitivity for the detection of pulmonary nodules, of small mediastinal and bronchopulmonary lymph nodes, and of pleural plaques improves characterization of lesion morphology. New diagnostic applications include the detection of very subtle diffuse lung disease and the diagnosis of pulmonary embolism and vascular malformations. For the diagnosis of tracheobronchial pathology, spiral CT is an ideal supplement to bronchoscopy.

Bronchial Diseases↗
PubMed1996

Selenium radiography versus storage phosphor and conventional radiography in the detection of simulated chest lesions.

PURPOSE: To compare selenium detectors with three conventional and digital detector systems for the detection of simulated pulmonary lesions. MATERIALS AND METHODS: Templates containing nodules, linear structures, and micronodular opacities were superimposed over an anthropomorphic chest phantom. The authors compared lesion detection with use of storage phosphor radiography (250 speed), selenium radiography (250 speed) with an antiscatter grid, selenium radiography (450 speed) without an antiscatter grid, an asymmetric screen-film system (400 speed), and a conventional screen-film system (250 speed). Detection performance of 10 radiologists was compared by using a multireader-multicase receiver operating characteristic analysis of variance. RESULTS: For the detection of nodules, no statistically significant differences between imaging modes were seen. For the detection of micronodules and linear lesions, both selenium techniques were superior to all other modes (P < .05). In addition, the asymmetric screen-film radiographs were inferior (P < .05) to the conventional screen-film radiographs and to storage phosphor radiographs for the detection of micronodules. CONCLUSION: The selenium detector improves detection of simulated fine linear and low-contrast micronodular details and appears to be superior to other detector systems for chest radiography.

Humans↗
PubMed1996

Clinical course of hypophosphatemic rickets in 23 adults.

Twenty-three adult patients (19 females, 4 males) with x-linked hypophosphatemic rickets (HPR) underwent a retrospective evaluation of the clinical course and a clinical examination by a nephrologist, orthopedic surgeon and dentist. Blood and urine analysis, bone density measurements with QCT and DEXA, ultrasonic examination of the kidneys were performed and the patients were asked to fill in a standardized questionnaire on pain and psychosocial rehabilitation. Mean final height was 152.4 cm +/- 8.5 SD in females and 157.3 cm +/- 8.9 SD in males. Decreased joint mobility was seen in all patients, deviations of the normal leg axis in 18/23 patients in spite of 69 correcting osteotomies in the past. Dental (n = 14) and psychosocial problems were associated with inability to work (n = 8). There was a trend that patients with a very low Tp/GFR had a more severe course of the disease. Early therapy with vitamin D metabolites and phosphate had a beneficial effect on growth, bone density and deformations. Eight patients had nephrocalcinosis due to vitamin D and phosphate therapy and had normal kidney function. Four patients had urinary tract abnormalities. We conclude that patients with HPR should receive continuous interdisciplinary care given by nephrologists, orthopedic surgeons, physiotherapists and dentists not only during childhood but also as adults.

Adult↗
PubMed1996

[Results and complications of intrauterine transfusion in fetuses with and without hydrops].

The group comprises 50 intrauterine transfusions in 15 patients with a severe form of foetal erythroblastosis. The authors describe the results and complications in hydropic and non-hydropic foetuses, diagnosed by ultrasound before transfusion treatment was started. In the group of non-hydropic foetuses the success rate of transfusion treatment was 90.1% and 10 neonates were born with a mean weight of 2030 g. The mean gestation period was 34 weeks. From four hydropic foetuses it proved possible to save only one, the success rate in this group was only 25%. The mean weight of hydropic foetuses was 1650 g and the gestation period at delivery 29 weeks. The rate of Caesarean sections in both groups was as high as 80%. Serious complications included thrombosis of the umbilicus, thromboembolism of the a. axillaris in a hydropic neonate and acute hypoxia of the foetus after transfusion. Four of six serious complications were recorded in hydropic foetuses.

Blood Transfusion, Intrauterine↗
PubMed1996

[Spiral CT and 3-dimensional reconstruction in evaluation of systemic venous obstruction after atrial switch operation for complete transposition of great vessels].

We report findings in spiral-CT from 11 adolescent or adult patients after atrial switch operation. The results demonstrate that computed tomography, particularly with the use of three-dimensional surface reconstruction, is very useful as a highly sensitive procedure for the detailed depiction of residua and sequelae after inflow correction for complete transposition. Especially systemic venous obstruction (SVO) is a well know complication following Mustard procedure for transposition of the great arteries. Demonstration of such obstruction is important, since the recognition and quantification of caval obstruction by clinical techniques is unreliable and indeed often impossible. Imaging procedures such as spiral computed tomography are important for this purpose. Advantages of spiral computed tomography, particularly with three-dimensional reconstruction, are discussed. The images were compared with findings in echocardiography and/or angiography affecting the site of operation.

Adolescent↗
PubMed1995

Minimally invasive diagnosis of renal artery stenosis by spiral computed tomography angiography.

We prospectively compared in a blinded fashion spiral computed tomography angiography (CTA) with arteriography in 62 consecutive patients with suspected renal artery stenosis (RAS). For CTA 150 ml of contrast material were injected intravenously. Arteriography was performed by DSA technique with selective catheterization of renal arteries. Of the 157 visualized renal arteries 155 could be evaluated with DSA and a total of 157 with CTA. Sensitivity of CTA for RAS > or = 50% was 98% and the specificity was 94%. Comparison of the grade of stenosis as evaluated by DSA versus CTA showed: identical gradation in 59 arteries (DSA > or = 50%/CTA > or = 50%), underestimation by CTA in one artery (DSA 50 to 75%/CTA < 50%), and overestimation by CTA in six arteries (DSA < 50%/CTA 50 to 75%). Factors that may contribute to these differences include impaired renal function and possibly "underestimation" of ostial RAS by arteriography. One artery not evaluable by arteriography showed a 70% stenosis by CTA. CTA showed no major side effects. We conclude that CTA has the same accuracy for the diagnosis of RAS > or = 50% as arteriography. However, CTA is only minimally invasive, safe, and causes less discomfort to patients.

Adult↗
PubMed1995

Detection of simulated chest lesions: comparison of a conventional screen-film combination, an asymmetric screen-film system, and storage phosphor radiography.

PURPOSE: To compare a high-contrast asymmetric screen-film system with a conventional screen-film combination and storage phosphor radiographs for detection of simulated chest lesions. MATERIALS AND METHODS: To test the diagnostic performance of these three systems, the authors used three types of simulated lesions that were superimposed over the chests of 10 patients and an anthropomorphic phantom. In the patient and phantom study, a total of 1,350 observations by each of the eight radiologists were analyzed by means of receiver operating characteristics. RESULTS: In the patient study, mediastinal nodules were better visualized with high-contrast asymmetric screen-film and storage phosphor radiographs compared with the conventional screen-film system. For visualization of pulmonary nodules, the high-contrast asymmetric screen-film system was best. Micronodules were poorly visualized on high-contrast asymmetric screen-film and storage phosphor radiographs, but only in the phantom study. CONCLUSION: The high-contrast asymmetric screen-film system combines the advantages of conventional screen-film radiographs with improved visualization of the mediastinum.

Adult↗
PubMed1995

[Diagnostic imaging in follow-up of surgically treated stenosis of the aortic isthmus in adolescents and adults].

Local abnormalities of the ascending aorta, especially at the site of correction are well known complications after surgical correction of aortic coarctation. Regular follow-up is therefore necessary. Besides chest X-ray, transesophageal-echocardiography and substraction angiography, magnetic resonance imaging (MRI) and computertomography (CT) provide a complete and noninvasive examination of the great vessels. MRI and CT are ideally suited for this purpose.

Adolescent↗
PubMed1994

Bifurcate tracheal stent with foam cuff for tracheo-esophageal fistula: utilization of reconstruction modes of spiral computed tomography.

Malignant tracheo-esophageal fistulae can be palliated with bifurcate tracheal stents. However, stents must be manufactured according to the individual anatomy. In these instances a foam cuff can result in better sealing of the fistulized area. We present a successful implantation of a bifurcate tracheal stent with foam cuff. To facilitate preoperative planning reconstruction possibilities offered by spiral computed tomography were used.

Adult↗
PubMed1994

[Accuracy of CT angiography in the diagnosis of renal artery stenosis].

Spiral CT in the form of CT angiography (CTA) provides a new method for the investigation of the large vessels. 52 patients with suspected renovascular hypertension were examined by CTA and arterial DSA. The computer tomographic and angiographic findings in 124 renal arteries were compared. Sensitivity of CTA for demonstrating renal artery stenosis was 95%, and for relevant stenoses it actually reached 100%. Specificity was 92%. Positive/negative prediction value was 85% and 100%. CTA proved outstandingly good for demonstrating or excluding renal artery stenosis and was superior to other imaging methods in several respects. CTA requires high contrast values, optimal timing and careful evaluation. Amongst various forms of image reconstruction, interactive viewing of the primary axial images and multiplanar reconstruction in a cine mode are essential and MIP projections are valuable.

Adult↗
PubMed1994

Application of AMBER in single- and dual-energy digital imaging: improvement in noise level and display dynamic range.

The combination of computed radiography (CR) and advanced multiple beam equalization radiography (AMBER) was evaluated for both single- and dual-energy chest radiography. The improved signal-to-noise ratio found with CR and AMBER resulted in a better visualization of structures in the mediastinum and basal lung than that found with CR alone. For the central lung, no improvement was seen. Because of the compressed dynamic range with CR and AMBER, contrast on hard copies and video monitors could be high without a sacrifice in image latitude. Dual-energy images showed a considerably lower noise level. The combined use of AMBER and CR promises to overcome the dynamic range limitations of digital displays while improving signal-to-noise ratio.

Artifacts↗
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↗