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M Prokop

Publications and source records attributed to M Prokop.

At least 55 records · Page 3Linked to original sources
PubMed1997

MRI contrast media - new developments and trends. CTA vs. MRA.

Recent developments in the non-invasive techniques of magnetic resonance angiography (MRA) and computerised tomographic angiography (CTA) are challenging conventional catheter angiography. Current indications for both techniques are discussed, such as their ability to diagnose aortic, pulmonary, renal, carotid and peripheral vascular diseases. Both tools provide almost identical clinical results, although each has their own advantages and disadvantages. MRA should be the technique of choice in young patients or those with real impairment since the gadolinium-based contrast agents are non-ionising and do not cause nephrotoxicity. On the other hand, MRA examination times are longer than those typically required for CTA, and therefore MRA is less suited to examinations of acute conditions.

Angiography↗
PubMed1997

Accuracy of single-energy quantitative computed tomography in the assessment of bone mineral density of cervical vertebrae.

Earlier studies have shown that single-energy quantitative computed tomography (SEQCT) is a reliable method for bone mineral density (BMD) measurements in thoracic and lumbar vertebrae. Moreover, SEQCT has proved to be a useful parameter in the selection of appropriate implants in cervical spondylodesis. The aim of this study was to determine the accuracy of SEQCT in cervical vertebrae BMD measurement. BMD with reference to calcium hydroxyapatite (Ca10[PO4]6[OH]2) was assessed by SEQCT in 100 human vertebral bodies of the cervical spine. Bone cylinders were then cut from the appropriate region of interest. The cylinder volume was determined by the liquid displacement technique. The density of the mineral component was measured following incineration at 1100 degrees C for 24 h. The calculated BMD was correlated with the SEQCT values, resulting in a coefficient of r = 0.79 (P < 0.01). Mean SEQCT values were significantly lower than those determined by direct density assessment (t-test for coupled sampling, P < 0.02). This result was in agreement with studies on thoracic and lumbar vertebrae. These data suggest that SEQCT can reliably measure BMD in the cervical spine.

Bone Density↗
PubMed1997

[Evaluation of congenital vena cava anomalies and acquired vena cava obstructions after atrial switch operation using spiral computerized tomography and 3-dimensional reconstruction].

We report spiral-CT findings in adult patients with congenital abnormalities of the vena cava and systemic venous obstructions after atrial switch operation. Especially systemic venous obstruction is a well-known complication following Mustard procedure for transposition of the great arteries. The results demonstrate that computed tomography, particularly with the use of 3-dimensional surface reconstruction, is very useful as a highly sensitive procedure for the detailed depiction of abnormalities of the vena cava or of residua and sequelae after inflow correction for complete transposition. Demonstration of such abnormalities or obstructions after atrial switch operation is important, since the recognition and quantitation of caval anomalies 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 3-dimensional reconstruction, are discussed.

Adolescent↗
PubMed1997

Storage phosphor radiography.

Storage phosphor radiography is a digital technique that uses photo-stimulable, phosphor screens to substitute for conventional screen-film combinations. While the technique is more than 15 years old, it is only recently that technological and economic aspects of these systems have become favourable enough to envisage a more widespread clinical application.

Equipment Design↗
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↗