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M Pocek

Publications and source records attributed to M Pocek.

18 recordsLinked to original sources
PubMed1992

[Synchrotron radiation: a new source in x-ray mammography].

This work was aimed at evaluating the image quality obtainable in X-ray mammography using synchrotron radiation monochromatic lines. After a short review of the current mammographic techniques, the main features of synchroton radiation in the X-ray field are analyzed, especially of that emitted by the Adone storage ring. Its features are then compared with the radiation emitted by a Coolidge tube. The experimental unit used in this study, including beamline, monochromator and mammograph, is then described together with the experimental method for carrying out a series of experiments in the mammographic field employing both monochromatic lines (E = 17 keV) and white radiation from conventional sources. The first series of experiments is described, which employed standard phantoms: the dependence of resolution and contrast on both wavelength and thickness of breast specimens is reported. Several mammograms of neoplastic breast specimens were obtained after mastectomy: they were acquired using both synchrotron monochromatic lines and radiation emitted by a conventional tube and employing the same acquisition system. The comparison of the two series of images shows that synchrotron radiation can demonstrate a high number of anatomopathologic details with high definition, contrast and resolution which cannot be obtained by means of a conventional source. Our results appear very promising and suggest synchrotron radiation as the major tool in the early diagnosis of neoplastic breast lesions.

Breast Neoplasms↗
PubMed1992

[The stenotic-occlusive anatomy and pathology of the renal arteries. Their evaluation by magnetic resonance angiography].

Magnetic resonance angiography of the renal arteries was performed in 10 healthy subjects, 10 patients with renal artery stenosis and 2 patients with accessory renal artery (1 unilateral, 1 bilateral). All patients selected among 35 subjects with suspected renovascular hypertension had previously undergone digital subtraction angiography. Four patients were studied before and after percutaneous transluminal angioplasty. MRA was performed with time-of-flight technique, with 2D and 3D FISP and 2D FLASH gradient-echo sequences. Digital subtraction angiography demonstrated stenoses ranging 40% to 90% in 10 cases, 7 unilateral (1 transplanted kidney) and 3 bilateral. RA correctly depicted > 90% stenoses in 5 cases, between 50% and 90% stenoses in 2 cases and < 50% in 2 cases. Four stenoses were not properly graded (3 over-graded and 1 not visualized because distal to ostium). Diagnostic accuracy was 71% for unilateral stenoses and 66% for bilateral stenoses (overall accuracy 69.2%).

Adult↗
PubMed1992

[The use of the single-pulse RARE sequence in the study of the cerebrospinal axis].

The authors describe a fast MR sequence allowing to obtain a myelographic-like, markedly T2-weighted, image quite similar to conventional myelographies. Relative to conventional spin-echo sequences, in which echoes are encoded so as to achieve the same phase, each echo of the sequence here employed is given a different phase encoding. The sequence, called MYUR (myelography-urography) is based on the generation, after a 90 degrees pulse, of a "train" of 256 echoes, each one phase-encoded differently, by multiple 180 degrees pulses, producing a single image. The total duration of such a sequence, with 2 repetitions, is 21 seconds. The MR myelographic sequence allows to univocally study tissues with a very long T2 relaxation time; under normal conditions, only cerebrospinal fluid, urine and bile are demonstrated. A resistive MR unit operating at 0.28 T was employed in the present study. MR myelography is capable of pointing out an eventual dural sac compression or a space-occupying mass, thus allowing an effective scout-view to center the subsequent pulse sequences; all MR-myelographic exams need to be completed with other short and long TR sequences.

Brain↗
PubMed1992

[Vascular radiology and physics of fluids].

In the cardiovascular system, morphology and functionality are closely related. The observation that atherosclerotic lesions appear with different incidence in the various sites and prefer bifurcations, suggested that vascular architecture might be an important pathogenic factor. Vascular geometry deals with the evaluation of the "form" element from a theoretical point of a view, pointing out the angles and diameters which can make the arterial system physiologically more efficient. The key element of the system is the bifurcation: depending on whether bifurcations are considered as a single entity or as a whole, either "local" or "global" geometry is employed. The morphology of the bifurcation directly affects blood flow patterns, influencing both blood flow velocity and wall shear stress. Experimental studies evidenced that high blood flow velocities and low wall shear stress have, respectively, a preventive or favorable role in atheroma development. By observing these altered flow sites, the areas which are most likely to develop atherosclerotic damage have been detected in the various bifurcations; the areas correspond to angiographic and autoptic findings. Based on their experience, the authors discuss the contribution that the different imaging techniques can give to the study of vascular geometry.

Angiography↗
PubMed1991

[Role of computerized tomography in endosseous implantology].

The Authors are proposing the use of computerized tomography for the evaluation of osseous structures of the maxilla and mandible before installation of titanium fixtures. The results indicate that the CT scan can give information about the structure and bone density. The height and the width of the alveolar osseous crests and the relationship with the incisive canal and the mandibular canal are clearly demonstrated. The CT scan can facilitate the measurement of the space available in order to install the titanium fixtures.

Alveolar Process↗
PubMed1991

[Interventional radiology of the digestive system].

The authors report on the use of interventional radiology modalities in the treatment of some gastrointestinal diseases (intussusception, stenosis, hemorrhage, etc). The results are compared with literature data relative to both interventional radiology and conventional therapeutic procedures. In our series, hydrostatic reduction of ileocolic intussusception was successful in 60% of cases. Transluminal dilatation with a balloon catheter was attempted in 108 patients with alimentary tract stenosis and was successful in 93. Hemorrhage and ischemia can be treated by means of transcatheter therapy (vasopressin, embolization) and percutaneous angioplasty. Percutaneous gastrostomy appears to be an effective alternative to surgical gastrostomy. Tapeworm infections can be cured by intraduodenal injection of "Gastrografin" (Schering). The success achieved in the different applications is such as to suggest a wider use of interventional radiology procedures, for they offer a more favorable cost/benefit ratio and often yield better results than conventional techniques.

Digestive System↗
PubMed1990

Optimal branching of human arterial bifurcations.

The area ratio, defined as the combined cross-sectional areas of the daughter branches divided by that of the parent artery, is an important indicator of "expansion" or "narrowing" in an arterial tree. In 120 morphologically normal human arterial bifurcations, angiographically studied, we measured branch artery diameters at and away from the bifurcation point to obtain "beta" and "D" ratios, respectively. These results were compared with optimal curves. Area ratio D values showed better agreement than area ratio beta with theoretical curves; for area ratio D, the positive regression line showed the same trend as expected from theory (y = 1.26 + 0.153x); for area ratio beta, the regression line was negative, showing a trend opposite to theory (y = 0.962 - 0.191x). Area ratio beta showed a significant correlation coefficient (r = 0.194; P less than 0.05) associated with aging, while for area ratio D it was not the same (r = 0.023; P less than 0.05). A significant correlation coefficient was also found between both of the area ratios and total branching angle. The new area ratio D, reflecting the branching geometry nearer to the bifurcation, is more promising than area ratio beta in the evaluation of optimal arterial bifurcation.

Adolescent↗
PubMed1988

The vascular geometry of human arterial bifurcations.

We used angiography to evaluate the branching characteristics of 69 morphologically normal human arterial bifurcations. Each angiographic picture was enlarged photographically and traced on paper. The diameter of the parent vessel (d0), the diameters of the two daughter vessels (d1 and d2-d1 denote the larger vessel), and the angles at which the two branches arise from the parent vessel (teta 1 and teta 2) were measured on each bifurcation. Because theoretically there are optimal values for angles and diameters that render an arterial bifurcation more efficient physiologically, the measured data were compared with predicted values. Branch diameters correlated better with predicted values than did branching angles. Twenty-six per cent of teta 1 and only 7.2% of teta 2 angles were within the optimal range; 68.2% of teta 1 and 79.7% of teta 2 were within 2% of optimal values in terms of physiologic efficiency. On the average, teta 1 angles were smaller than teta 2 angles (17.0 degrees vs. 29.5 degrees). Morphologic and hemodynamic pecularities of vessels and errors in the measuring technique must be considered in analyzing the data obtained. Moreover, branching angle measurements changed slightly with age: teta 1 became larger and teta 2 narrower. In the cardiovascular system branching angles and branch diameters follow, to some degree, the principles predicted by theory. Branching angles diverging considerably from those principles may indicate the presence of vascular disease although a direct connection has not been established.

Adolescent↗
PubMed1987

[Use of digital subtraction angiography in the study of thoracic outlet syndrome].

Thoracic outlet syndrome (TOS) is characterized by neural and vascular symptoms of the upper extremity, caused by abnormal compression on the brachial plexus, subclavian-axillary artery and/or vein, when the patient makes some movements. Compression can occur on various anatomic levels: interscalene triangle, costoclavicular passage, pectoralis minor tendon. The authors describe the various stress position to point out the place of compression, etiology and the most common methods of study. They refer also their experience about TOS obtained using selective digital subtraction angiography (DSA) of both subclavian arteries in 6 patients. Thanks to DSA, that allows the dilution of contrast medium, it is possible to carry out all the stress maneuvers using a little amount of contrast medium.

Adolescent↗
PubMed1986

[Role and possibility of intravenous digital substraction angiography in problems of renal transplantation].

Intravenous Digital Subtraction Angiography (IVDSA) was used to evaluate 6 renal allograft recipients and 3 potential renal donors. In 4 potential renal donors and in 2 allograft recipients, angiographic data were confirmed by surgery. IVDSA is a safe, accurate, easily performed, outpatient procedure; in our opinion DSA should became the procedure of choice to study vascular anatomy in renal transplant evaluation.

Angiography↗
PubMed1984

[Morphological lesions of the choledochus studied with combined percutaneous transhepatic cholangiography and hypotonic duodenography].

Twenty two patients obstructive jaundice were investigated by combined fine needle percutaneous cholangiography and hypotonic duodenography. The association of the two techniques enables prompt localization of the site of obstruction and definition of the nature of the lesion. It proves to be of particular use in the differential diagnosis of carcinoma of the head of the pancreas, carcinoma of the distal choledochus and carcinoma of the socalled choledochoduodenal junction.

Bile Duct Neoplasms↗
PubMedDate not supplied

Computed tomography detection of gastrointestinal neoplasms.

Gastrointestinal (GI) tract neoplasms can be detected, evaluated and staged by computed tomography (CT), especially from high-resolution examinations, but routine CT scanning may occasionally discover GI neoplasms in patients with non-specific symptoms. We therefore evaluated the sensitivity and main signs of CT examinations resulting from routine sessions. In 46 out of 1560 patients who underwent abdominal CT, it was possible to obtain a diagnosis of primitive gastric or colo-rectal tumour by means of barium X-ray and/or endoscopy. The sensitivity rate of CT obtained from the present study was 86% in gastric tumours and 87% in colonic tumours. In gastric lymphoma, infiltrating carcinoma of stomach and rectal carcinoma, the sensitivity rate was 100%. The CT diagnosis of GI neoplasms was based on diffuse or local thickening of the gut on a solid dishomogenous mass showing contrast enhancement. The prevalence of various patterns depends on site of origin and on macroscopic features of the neoplasia. In conclusion the results suggest that abdominal CT, even if performed with a method not specifically devoted to GI tract, has high sensitivity rates and then a high probability of detecting GI neoplasms when unsuspected at time of the examination. In our series 11% of GI neoplasms were initially diagnosed by routine CT examination.

Adult↗
PubMedDate not supplied

[Use of coronal sections in computerized tomography].

The authors emphasize the use of coronal cut in CT in sellar and parasellar lesions; in tumors involving the tentorium; in differential diagnosis between meningiomas of falx and parasagittal ones and in those lesions with extension into paranasal sinus and face. The purpose of this method is to evaluate the exact relationship of these type of lesions with adjacent structures in a tridimensional view.

Adenoma↗