Biomedical subjects

J Vassileva

Publications and source records attributed to J Vassileva.

10 recordsLinked to original sources

PubMed2006

Bulgarian experience in the establishment of reference dose levels and implementation of a quality control system in diagnostic radiology.

Results from a Bulgarian patient dose survey in diagnostic radiology are presented. Reference levels for entrance surface dose (ESD) were 0.9 mGy for chest radiography (PA), 30 mGy for lumbar spine (Lat), 10 mGy for pelvis, 5 mGy for skull (AP), 3 mGy for skull (Lat) and 13 mGy for mammography. Quality control (QC) programmes were proposed for various areas of diagnostic radiology. Film processing QC warranted special attention. Proposed QC programmes included parameters to be tested, level of expertise needed and two action levels: remedial and suspension. Programmes were tested under clinical conditions to assess initial results and draw conclusions for further QC system development. On the basis of international experience, measurement protocols were developed for all parameters tested. QC equipment was provided as part of the PHARE project. A future problem for QC programme implementation may be the small number of medical physics experts in diagnostic radiology.

Bulgaria↗

PubMed2006

Radiation protection and safety in medical use of ionising radiation in Republic of Bulgaria--harmonization of the national legislation with Euratom directives.

From February 2002 to November 2003 the National Centre of Radiobiology and Radiation Protection conducted a PHARE twinning project 'Radiation Protection and Safety at Medical Use of Ionising Radiation'. The main purposes of the project were the harmonization of Bulgarian legislation in the field of radiation protection with EC Directives 96/29 and 97/43 Euratom, and the establishment of appropriate institutional infrastructure and administrative framework for their implementation. This paper presents the main results of the project: elaboration of Ordinance for Protection of Individuals from Medical Exposure; performance of a national survey of distribution of patient doses in diagnostic radiology and of administered activities in nuclear medicine and establishment of national reference levels for the most common diagnostic procedures.

Bulgaria↗

PubMed2005

Implementation of the European protocol for quality control of the technical aspects of mammography screening in Bulgaria.

The results from the national pilot project on implementation of the European protocol for the quality control (QC) of the technical aspects of mammography screening as well as the European protocol for dosimetry in mammography in Bulgaria are presented. A QC programme for mammography equipment and a standardised measurement protocol were created. The full QC programme was tested on four mammography units of different types and ages. A national survey was performed for entrance surface air kerma (ESAK) on 20 units using a 45 mm PMMA standard phantom. Average glandular dose (AGD) was calculated using the conversion coefficients from the European dosimetry protocol. The survey demonstrated considerable differences in the technical condition of the mammography units that resulted in varying image quality. The measured values of ESAK showed significant variations. Doses for approximately 45% of the units were found to be below the European reference level. The values for AGD ranged from 0.35 to 3.47 mGy. The main problems found were film processing, optical density (OD) control settings and AEC adjustment. The results showed the importance of film OD measurements parallel to dose measurements. The X-ray mammography in the country needs optimisation. Comprehensive quality assurance programme should be adopted in all departments covering permanent QC of the equipment, image quality and breast dose.

Breast↗

PubMed2004

A phantom approach to find the optimal technical parameters for plain chest radiography.

A simple approach based on phantom measurements is proposed in this study to find the filtration, tube potential and antiscatter device that are optimal in respect of patient dose and image quality, at constant film-screen combination, film processing and viewing conditions. An original quasi-anthropomorphic chest phantom was exposed with 18 different beam qualities and three antiscatter devices. The entrance surface dose, organ doses and effective dose were estimated for each radiograph. The image quality was compared using two objective quality indexes, a contrast index and a scatter fraction, as well as two subjective indexes, a low contrast visualization index and a high contrast visualization index. It was found that for this X-ray unit, routinely using a 7:1 antiscatter grid, the optimal imaging technique is added filtration of 0.1 mm Cu+1 mm Al at a tube potential 100 kVp. Using a 25 cm air gap instead of the grid allows the tube potential to be increased to the upper limit of 120 kVp for this unit. The entrance surface dose of 0.075 mGy at 120 kVp with an air gap is less than half the value of the same quantity with a grid at 100 kVp and is significantly below the European reference level of 0.3 mGy. This phantom method, comprising both objective measurements and subjective estimation, is suitable for dose-image quality optimization in a clinical environment.

Anthropometry↗

PubMed2002

A phantom for dose-image quality optimization in chest radiography.

Optimization in chest radiography requires evaluation of patient dose and image quality. This study is aimed at proposing a simple geometrical phantom that realistically simulates the important anatomical regions of the thorax. For this purpose, the standard LucAl chest phantom is modified by adding an "anthropomorphic" insert and image quality test plate. Different test objects are arranged on the plate in three important anatomical areas; lung, cardiac, and subdiaphragmal regions. The aim is to simultaneously find two types of image quality index, objective and subjective, which can be used to compare different images in order to select the better image. Two objective indices are proposed, areal contrast index DeltaC(a) and scatter fraction P(s) and two subjectively estimated, a low contrast visualization index P(low) and a high contrast visualization index P(high). To demonstrate the potential of this phantom method it was applied to an X-ray unit to find the optical film density that ensures optimal visualization in different anatomical areas. It was found for the X-ray system under investigation that the automatic exposure control could be set to produce an optical density of about 1.8 in the lung field. The reported method is easily implemented in any clinical situation where optimization of chest radiography is needed.

Humans↗

PubMed2001

Patient dose, image quality and radiographic techniques for common X ray examinations in two Greek hospitals and comparison with European guidelines.

The radiographic technique factors and the quality of each radiographic image for three common examinations (chest PA, pelvis AP and lumbar spine LAT) were compared with the European criteria and entrance surface dose (ESD) was measured for each radiograph in two Greek hospitals. The measurements were carried out using calibrated LiF thermoluminescence dosemeters. The patients were selected so that their weight was close to 70 +/- 10 kg and their height to 170 +/- 10 cm. Effective dose values were calculated using a PC-based Monte Carlo program. All four X ray rooms in the survey achieved mean doses well below the European reference doses. However the mean doses in the X ray rooms differed by a factor of about 3.

Dose-Response Relationship, Radiation↗

PubMed1998

Differential sensitivity to alcohol reinforcement in groups of men at risk for distinct alcoholism subtypes.

The present study examines the relationship of familial and personality risk factors for alcoholism to individual differences in sensitivity to the positively and negatively reinforcing properties of alcohol. Sixteen sons of male alcoholics with multigenerational family histories of alcoholism (MFH) and 11 men who self-report heightened sensitivity to anxiety (HAS) were compared with 13 age-matched family history negative, low anxiety sensitive men (FH-LAS) on sober and alcohol-intoxicated response patterns. We were interested in the effects of alcohol on specific psychophysiological indices of "stimulus reactivity," anxiety, and incentive reward. Alcohol significantly dampened heart rate reactivity to aversive stimulation for the MFH and HAS men equally, yet did not for the FH-LAS group. HAS men evidenced idiosyncrasies with respect to alcohol-induced changes in electrodermal reactivity to aversive stimulation (an index of anxiety/fear-dampening), and MFH men demonstrated elevated alcohol-intoxicated resting heart rates (an index of psychostimulation) relative to the FH-LAS men. The results are interpreted as reflecting a sensitivity to the "stimulus reactivity-dampening" effects of alcohol in both high-risk groups, yet population-specific sensitivities to the fear-dampening and psychostimulant properties of alcohol in the HAS and MFH groups, respectively.

Adaptation, Psychological↗

PubMed1989

Two hundred intrauterine exchange transfusions in severe blood incompatibilities.

Two hundred intrauterine exchange transfusions were performed under local anesthesia in 107 cases of blood incompatibilities (60 fetuses with severe anemia and 47 with hydrops). Under sonographic guidance, depending on fetal and placental position, an optimal puncturing site was selected along the umbilical vein: placental insertion, fetal insertion, or fetal intraabdominal segment. Tests were immediately performed to confirm fetal origin of blood obtained and estimate hemoglobin level. Blood used for exchange transfusion was compatible with maternal blood and had a hematocrit value of 75%. Exchange transfusion was continued until a hemoglobin level of 16 gm/dl was reached. This procedure was first associated with intraperitoneal transfusions and was subsequently used independently once a month to maintain an adequate hemoglobin level. In 4 fetuses with hydrops, antenatal regression of this sign was observed in 33 cases (70.2%). Overall outcome of 107 fetuses after exchanges was 84 living neonates (78.5%), 15 deaths in utero, and eight neonatal deaths. The survival rate was 91.6% for fetuses without hydrops and 61.7% for those with hydrops. The advantage of exchange transfusion appears to be rapid and efficient correction of anemia with elimination of incompatible fetal red blood cells.

Birth Weight↗

PubMed1984

Characteristic sonographic features of schistosomal periportal fibrosis.

The hepatic sonograms of 22 patients with the features of schistosomal periportal fibrosis (PPF) were reviewed retrospectively. Dense echogenic bands were seen when scanning along the long axis of the intrahepatic portal vein radicles. Rounded densities resulted from scanning across these bands as they radiated from the porta hepatis to the liver's edge. Scanning across central and peripheral bifurcation points of the portal veins produced a branching pattern of high echogenicity. Associated findings were ascites and splenomegaly secondary to the liver disease. The hepatic sonographic features were characteristic of portal tract thickening from schistosomal PPF.

Adult↗

PubMedDate not supplied

Passive protection against heterologous gram-negative bacteria mediated by antiserum to epimeraseless Rc mutant of Salmonella minnesota.

Antiserum to the epimeraseless Rc mutant of Salmonella minnesota was prepared by immunization of rabbits. The antiserum provided good protection in mice i.p. challenged with 125 and 25 LD50 doses of live heterologous Gram-negative bacteria i. e. S. typhimurium, Escherichia coli and Pseudomonas aeruginosa. The protection against Klebsiella pneumoniae was negligible. Pre-immune rabbit serum produced only marginal protection. The protective effect of S. minnesota Rc antibodies was entirely abolished upon absorption of Rc antiserum with homologous bacteria. Pre-immune and absorbed sera exhibited a similar protective effect at lower LD50 values, namely 5 and 1 LD50.

Animals↗