Biomedical subjects

E Vañó

Publications and source records attributed to E Vañó.

At least 19 recordsLinked to original sources

PubMed2005

A survey of patient dose and clinical factors in a full-field digital mammography system.

In this work, we analyse the dose to 5034 patients (20 137 images) who underwent mammographic examinations with a full-field digital mammography (FFDM) system over a 2-y period. The information relevant to this study has been extracted from the image Digital Imaging and Communications in Medicine (DICOM) headers. Entrance surface air-kerma (ESAK) without backscatter and average glandular dose (AGD) were estimated following the methodology proposed in the European Protocol on Dosimetry in Mammography. Mean values for patient age and compressed breast thickness were 56 +/- 11 y and 52 +/- 13 mm, respectively. The mean ESAK value was 8.1 mGy and the mean AGD was 1.9 mGy. In addition, the dose values from both FFDM and screening-film mammographic (SFM) examinations were compared. The third quartile (TQ) of the ESAK values delivered by the FFDM system was 33% lower and 32% higher than the TQ for SFM with slow and fast screen/film receptors. Differences between dose values for cranio-caudal (CC) and medio-lateral oblique (MLO) images (about 27% for SFM) decreased to 11% for FFDM.

Adolescent↗

PubMed2005

Estimation of the peak entrance surface air kerma for patients undergoing computed tomography-guided procedures.

The purpose of this work was to develop a method for estimating the patient peak entrance surface air kerma from measurements using a pencil ionisation chamber on dosimetry phantoms exposed in a computed tomography (CT) scanner. The method described is especially relevant for CT fluoroscopy and CT perfusion procedures where the peak entrance surface air kerma is the risk-related quantity of primary concern. Pencil ionisation chamber measurements include scattered radiation, which is outside the primary radiation field, and that must be subtracted in order to derive the peak entrance surface air kerma. A Monte Carlo computer model has therefore been used to calculate correction factors, which may be applied to measurements of the CT dose index obtained using a pencil ionisation chamber in order to estimate the peak entrance surface air kerma. The calculations were made for beam widths of 5, 7, 10 and 20 mm, for seven positions of the phantom, and for the geometry of a GE HiSpeed CT/i scanner. The program was validated by comparing measurements and calculations of CTDI for various vertical positions of the phantom and by directly estimating the peak ESAK using the program. Both validations showed agreement within statistical uncertainties (standard deviation of 2.3% or less). For the GE machine, the correction factors vary by approximately 10% with slice width for a fixed phantom position, being largest for the 20 mm beam width, and at that beam width range from 0.87 when the phantom surface is at the isocentre to 1.23 when it is displaced vertically by 24 cm.

Air↗

PubMed2004

Monte Carlo simulations in CT for the study of the surface air kerma and energy imparted to phantoms of varying size and position.

A Monte Carlo computational model of CT has been developed and used to investigate the effect of various physical factors on the surface air kerma length product, the peak surface air kerma, the air kerma length product within a phantom and the energy imparted. The factors investigated were the bow-tie filter and the size, shape and position of a phantom which simulates the patient. The calculations show that the surface air kerma length product and the maximum surface air kerma are mainly dependent on phantom position and decrease along the vertical axis of the CT plane as the phantom surface moves away from the isocentre along this axis. As a result, measurements using standard body dosimetry phantoms may underestimate the skin dose for real patients. This result is specially important for CT fluoroscopic procedures: for an adult patient the peak skin dose can be 37% higher than that estimated with a standard measurement on the body AAPM (American Association of Physicists in Medicine) phantom. The results also show that the energy imparted to a phantom is mainly influenced by phantom size and is nearly independent of phantom position (within 3%) and shape (up to 5% variation). However, variations of up to 30% were found for the air kerma to regions within the AAPM body phantom when it is moved vertically. This highlights the importance of calculating doses to organs taking into account their size and position within the gantry.

Adult↗

PubMed2004

Suitability of resin-coated photographic paper for skin dose measurement during fluoroscopically-guided X-ray procedures.

The need for mapping skin doses during fluoroscopically-guided X-ray procedures has been described by a number of institutions and experts. Different large photographic or X-ray films placed on the patient's skin have been found to be useful for recording doses up to 1.0-2.0 Gy - depending on the film - and up to 15 Gy using radiochromic films. Though the upper limit of the film sensitivity is seldom exceeded during interventional procedures, the main disadvantage of the X-ray films is still the excessive sensitivity for long, high dose procedures. Radiochromic films show poor definition for doses below 0.5 Gy and are expensive. The goal of the present paper is to analyse the possibilities of using common resin-coated photographic paper for this purpose. Sensitometric curves obtained with different paper types processed in conventional X-ray film automatic processors demonstrate that some of them can be used with better results than X-ray films at a very low cost. Doses from about 10 mGy to near 3.0 Gy can be measured with good accuracy using a variety of glossy photographic papers.

Dose-Response Relationship, Radiation↗

PubMed2001

Approaches to establishing reference levels in interventional radiology.

Reference levels in radiodiagnostics are a requirement stated by the Council Directive 97/43/EURATOM. Reference levels are also relevant for interventional procedures, in accordance with this Directive, which claims special attention to quality assurance programmes, including quality control and patient dose evaluations for special practices such as interventional radiology, to assess the convenience of corrective action depending on the measured doses. The present paper addresses a method of establishing reference levels in interventional radiology, in the framework of optimisation, discussing the ways of putting forward values with a degree of tolerance, to allow for procedure complexity, depending on patient pathology. The need for several estimators used together, namely fluoroscopy time, total number of images per procedure and dose-area product, is also emphasised, proposing a further skin dose estimate in case of risk of deterministic effects. Finally, a brief summary of principles is given for the correct management of reference levels in interventional radiology.

European Union↗

PubMed2001

Training and accreditation in radiation protection for interventional radiology.

Training in radiation protection is a basic aspect of the optimisation of medical exposures. Council Directive 97/43/EURATOM establishes the need for an adequate theoretical and practical training of the staff working in radiological practices, and competence in radiation, for which Member States shall ensure the establishment of appropriate curricula. Keeping in mind the different specialities and professional responsibilities, training curricula must be proposed and endorsed to achieve a common core of knowledge in radiation protection throughout Europe, for different groups of health workers. In interventional radiology, previous initiatives led to the definition of a syllabus of educational objectives and to its testing in a specific course. The present paper presents educational objectives for interventional radiology, developed in the framework of the DIMOND European concerted action.

Accreditation↗

PubMed2001

The use of dynamic phantoms in interventional radiology.

The authors have constructed a 2D motor-controlled test object phantom holder to simulate clinical situations in which patient movement could be a cause of image degradation. The PAtient MOvement SImulation Test Object (PAMOSITO) has been constructed with modular parts to use different mobile test objects and static structures. The system allows the programming of different cycles of movement along two axes. PAMOSITO has been used in X ray equipment dedicated to interventional radiology. Those systems usually allow for different values for frame rate, pulse width or weighted frame averaging methods. The influence of selecting different values of the parameters, patient movement and its relation to patient dose and image quality has been studied. Image blurring due to motion has been evaluated with Leeds test objects TO.10 and 18FG. Spatial resolution limits and the threshold contrast detail detectability performance have been studied.

Absorptiometry, Photon↗

PubMed2001

A method based on DIMOND quality criteria to evaluate imaging in diagnostic and interventional cardiology.

Image quality criteria (IQC) for cine-angiography were recently settled. The aim of this study was to test whether these criteria allow a measurement of the quality of cine-angiograms. A questionnaire was derived from IQC where a binary response was required regarding the degree of visibility of anatomic or pathologic structures. Scores were given on a ranking scale. Two quality scores were defined (total score and minimum score) and standard deviation (SD) was assumed to be an indicator of the method's reproducibility. Data of the total score are presented for the first nine angiograms. Six experts obtained thirty-nine readings. The total scores ranged between 83 and 99% (SD 0.8-18.7%); 89% of the readings were within 4% of SD. This preliminary experience indicates that quality criteria can be translated into a scoring system that yields reproducible data in most instances. The analysis of the remaining angiograms will help in understanding how to improve these results.

Cardiology↗

PubMed2001

Patient dose related to the complexity of interventional cardiology procedures.

In interventional cardiology (IC) the PTCA (percutaneous transluminal coronary angioplasty) procedure is the most frequent procedure with the highest dose to the patient. The procedure is usually performed by cardiologists having, in general, insufficient knowledge of radiation physics, radiation technology and radiation protection. The need for radiation protection is of paramount importance in this field of interventional radiology. Correlation between the complexity of PTCA procedure and irradiation parameters (fluoroscopy time, number of images and dose-area product--DAP) has been demonstrated. The presence of severe tortuosity and occlusion of > or = 3 months play a major role. Fluoroscopy time is better correlated with technical factors than DAP, which also includes the influence of patient size, collimation, operation modes, and X ray beam orientation. The number of acquired images is less correlated with the complexity of the PTCA procedure. A complexity index was conceived and procedures were divided into three groups, defined as: simple, medium and complex, which were significantly different in terms of patient dose.

Angioplasty, Balloon, Coronary↗

PubMed2001

Deterministic effects in interventional radiology.

Since the development of interventional radiology, the number and complexity of procedures has increased significantly and continues to grow. Interventional radiology procedures offer substantial health care benefits. However, associated with the increasing complexity as well as a lack of quality control programmes and specific training in radiation protection, there is an increase in the occurrence of deterministic effects in both patients and staff. There is a growing literature of case reports describing deterministic effects. A review of some case reports and the response of various international organisations is presented. It is important that workers in interventional radiology are aware of the potential for deterministic effects and the dose threshold for their onset, so that patients can be followed up appropriately.

Adolescent↗

PubMed2001

Reference doses in dental radiodiagnostic facilities.

The present work describes an experiment undertaken using thermoluminescent dosemeters to obtain a local reference dose level in orthopantomography, based on patient measurements in 11 dentistry installations. In addition, a critical audit of the dose recommended by the International Atomic Energy Agency for intraoral X-ray diagnostics is performed, based on data gathered from over 300 intraoral X-ray facilities. The provisional local reference levels proposed are 0.7 mGy entrance surface dose at the occipital region for orthopantomography and 3.5 mGy entrance surface dose for intraoral radiology.

Adult↗

PubMed1999

Preliminary safety evaluation of a cyclotron facility for positron emission tomography imaging.

This work describes the design characteristics of a medical imaging centre which uses positron emission tomography, with a cyclotron for fluorine-18 and nitrogen-13 production, and which has provided experimental information on operational data recorded by area dosimetry since 1995. Doses to radiopharmacy and medical staff have been measured both in normal work and in some handling incidents. Data on radiation levels in the installation have also been obtained and related to design details and shielding. Area dosimetry was carried out using a five-stationary detector network, with a sampling rate of 2 min(-1), and by thermoluminescent dosimetry (TLD). Staff were also monitored by TLD, using extra chips for finger dosimetry and to duplicate individual whole-body dosimetry in order to measure doses in certain single operations. For normal work, average whole-body doses to radiopharmacy staff were between 0.03 and 0.28 mSv/month, wrist doses were between 0.42 and 2.67 mSv/month, and finger doses were between 1.4 and 7.7 mSv/day for the left hand and 0.8 and 2.4 mSv/day for the right hand; such variation reflects the differing expertise of staff and the role played by optimisation. Finger doses between 16 and 131 mSv were measured in handling incidents, and finger doses of 20.2 and 20.7 mSv for the left hand and 22.0 and 22.3 mSv for the right hand were measured during handling of a syringe without shielding, containing 3 GBq. For medical staff, contributions to the whole-body dose of 2.0 and 1.9 microSv/procedure were measured for injection and placing the patient on the examination couch, respectively. Dose measurement on the middle finger of the right hand gives an average of 70 microSv during the injection. The provisions regarding the shielding design have proved to be adequate and effective during a 3-year operational period. Operational doses to medical staff are comparatively low, while radiopharmacy staff are the most exposed. The finger doses in these professionals may exceed the annual limit, unless operational restrictions in daily practice are adopted. On-line area dosimetry records based on dose rate probes have proved to be effective both for monitoring radiation levels during the operation and for detecting changes in the behaviour of the facility in the irradiation process.

Cyclotrons↗

PubMed1999

Report of an image quality and dose audit according to directive 97/43/Euratom at Spanish private radiodiagnostics facilities.

An audit of Spanish private medicine radiodiagnostics facilities has been carried out, based partly on Spanish legislation relating to European Directives on health protection against ionizing radiation risks in medical exposure. The study included an appraisal of infrastructure and equipment, and aspects of quality assurance and radiation protection, by means of data collected through surveys. Of the 51 centres audited, a sample of 24 X-ray rooms was chosen, then an external evaluation with regard to image quality and patient dose was performed, by an advisory board of radiologists and medical physicists. The methodology used was similar to that of the group of European Union experts in European dose evaluation and image quality trials. Chest, abdomen, lumbar spine and breast examinations were monitored. Doses were measured with thermoluminescent dosimeters. A third of the X-ray rooms evaluated reached or exceeded dose reference values, and in a third of the cases the image quality left considerable room for improvement. Breast and chest examinations showed themselves to be the hardest to perform, not only as a result of exceeding the reference doses, but also due to failure to meet good image quality standards.

European Union↗

PubMed1998

Dosimetric and radiation protection considerations based on some cases of patient skin injuries in interventional cardiology.

Recently, several cases of skin injuries have been detected in patients undergoing cardiac radiofrequency catheter ablation. These procedures were performed on a biplane X-ray system used in a large Spanish hospital for interventional cardiology procedures. Interventional procedures performed and radiation lesions produced on patients are described. The radiation lesions were mainly erythematous lesions and chronic radiodermatitis. Results of the dosimetric evaluations and an analysis of the operational aspects of radiological protection are discussed. Poor image quality could have influenced the length of the procedures. Dose rate at the image intensifier entrance was within usual reported values in literature. However, the focus-to-skin distance for the horizontal X-ray beam was too short, resulting in a high skin dose rate. Additionally, X-ray beams are of fixed orientation, and accumulated skin dose in the patient's right side has been estimated as 11-15 Gy per procedure. In conclusion, practical radiation protection considerations to avoid further incidents of this sort are proposed, concerning the use of X-ray systems specially designed for interventional radiology, the improvement of cardiologists' training in radiation protection and routine patient dose measurements for complex interventional procedures.

Adolescent↗

PubMed1998

Lens injuries induced by occupational exposure in non-optimized interventional radiology laboratories.

Several cases of ophthalmologically confirmed lens injuries, caused by occupational radiation exposure, have occurred in two X-ray rooms devoted to vascular and visceral interventional radiology procedures. Both laboratories were equipped with overcouch X-ray systems not designed for interventional radiology and without specific tools for radiation protection of the eyes. Typical workloads ranged from between two and five procedures per day. For the two radiologists affected, estimates for the dose to eye lens ranged from 450 to 900 mSv per year, over several years. Once the incidents had been detected, the X-ray systems in both rooms were removed and new equipment specifically designed for interventional radiology was installed, including suspended shielding screens. Since these lens injuries were only detected accidentally, measures to avoid similar occurrences in the future are discussed.

Cataract↗

PubMed1998

Radiation exposure to medical staff in interventional and cardiac radiology.

The aim of this work has been to determine typical occupational dose levels in interventional radiology and cardiology installations and to relate doses to patient and occupational dosimetry through the dose-area product. An experimental correlation between environmental dosimetric records and dose-area products in the centres studied was established. The study covered a sample of 83 procedures performed by 10 specialists in six laboratories. The radiologists and cardiologists monitored wore nine thermoluminescent chips next to eyes, forehead, neck, hands, left shoulder, left forearm and left arm during each single procedure. In addition, direct reading electronic devices for environmental dosimetry were placed in the C-arm of the X-ray system, to estimate roughly the occupational radiation risk level. Typical shoulder doses derived from electronic dosimetry range between 300 and 500 muSv per procedure, assuming no lead protective screens were used. Using these values and patient dose-area data from two laboratories, averaged ratios of 84 and 120 muSv per 1000 cGy cm2 are obtained for cardiology procedures. Finally, occupational dose reductions of approximately 20% when using highly filtered X-ray beams with automatic tube potential (kV) reduction (available in some facilities), and by a factor of about three when using ceiling mounted screens, have been found.

Cardiology↗

PubMed1998

Design of a PC controlled test device for the study of patient motion in X-ray radiology: first applications and results.

Simulation and study of patient motion should be undertaken for different imaging techniques since all new radiological techniques or equipment must pass through evaluation processes to verify their functional capability and assess their performance compared with other equipment. A device to study the effects of motion on X-ray image quality was designed and built. The main goal of the PC controlled device developed by our group is to allow the adaptation of different phantoms and test objects. Preliminary experiments for the evaluation of different thorax screen-film systems were carried out by simulating respiratory motion. It is concluded that moving objects should be included for the comparison of screen-film systems since predictions based only on findings in stationary test conditions could lead to false conclusions.

Artifacts↗

PubMed1997

Patient dosimetry in interventional radiology using slow films.

A method for the evaluation of patient doses in interventional radiology procedures is presented and discussed. The method requires the analysis of slow non-screen films such as those used in radiotherapy. Dose area product and patient skin dose can be estimated with fair accuracy depending on the interventional procedure type. The agreement between the slow film method and diamentor measurement is better than 5% after the application of appropriate corrections. The cost is reasonable (pounds 5 per film) making it a worthwhile option in patient dosimetry, especially when the X-ray equipment does not include any fixed dose-area measuring device. Additional valuable information which may be applied to optimization of procedures (e.g. irradiated areas, number and types of projections check of appropriate use of beam limiting devices) is achieved by examining the different irradiation fields on the film.

Angiography↗