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Biomedical subjects

E Guibelalde

Publications and source records attributed to E Guibelalde.

At least 19 recordsLinked to original sources
PubMed2006

Evaluation of risk of deterministic effects in fluoroscopically guided procedures.

A methodology for the evaluation of skin dose distribution and possible skin injuries on patients undergoing interventional procedures has been developed as part of the European DIMOND programme. Relevant dosimetric data from the procedures are recorded and other specific measurements for skin dose evaluation (slow films for therapy, radiochromic films, thermoluminescence dosemeters and optically stimulated luminescence dosemeters) have been carried out. For non-cardiac and for some cardiac procedures, dose-area product values of 200 and 300 Gy cm2 were proposed, respectively, as a trigger level for further detailed skin dose investigation and possible clinical follow-up. Results from a survey of 191 selected complex procedures are reported. Out of all the patients included in the trial, 16% received skin doses > or =1.5 Gy. No skin injuries were found in any of the patients followed.

Dose-Response Relationship, Radiation↗
PubMed2006

Patient dosimetry and image quality in digital radiology from online audit of the X-ray system.

The present work describes an online patient dosimetry and an image quality system in digital radiology. For the patient dosimetry audit, current mean values of entrance surface dose (ESD) were compared with local and national reference values (RVs) for the specific examination type evaluated. Mean values exceeding the RV trigger an alarm signal and then an evaluation of the technical parameters, operational practice and image quality was begun, using data available in the DICOM header to derive any abnormal settings or performance to obtain the image. The X-ray tube output for different kVp values is measured periodically, to allow for the automatic calculation of ESD. The system allows also for image audit, linking the dose imparted, the image quality and the alarm condition, if produced. Results and the benefits derived from this online quality control are discussed here.

Humans↗
PubMed2006

Quantification of motion unsharpness in digital fluoroscopy.

The objectives of this work were first to develop a convenient method to quantify persistence in digital fluoroscopy systems, then to quantify the effect of variable temporal averaging on the detection of moving low-contrast test details within digital fluoroscopic and pulsed fluoroscopic images. The results were analysed to clarify the relationship between the optimum persistence required to see the lowest contrast for circular test details for a range of diameters and their speed of movement. The optimum persistence values obtained are compared with the limited data available on speeds of movement of patient organs during fluoroscopy. It is tentatively concluded that for imaging the abdomen, the optimum imaging system persistence time constant is approximately 0.15 s. For the much greater speeds associated with cardiac motion, no additional frame averaging is necessary, i.e. just the persistence provided by the observer's visual system appears to be optimal for small objects.

Fluoroscopy↗
PubMed2006

Influence of patient thickness and operation modes on occupational and patient radiation doses in interventional cardiology.

Patient and staff dose values in an interventional cardiology laboratory for different operational modes and several patient thicknesses (from 16 to 28 cm, simulated using polymethylmethacrylate) are presented. When increasing patient thicknesses and depending on fluoroscopy and cine modes, occupational doses can increase >30 times the baseline level. Scatter dose rates at the cardiologist's position with no radiation protective tools ranged from 1 to 14 mSv h(-1) for fluoroscopy, and from 10 to 47 mSv h(-1) during cine acquisition. Patient entrance surface air kerma rates increased by nearly 3 and staff dose rates by up to 2.6 when fluoroscopy was moved from the low to the high mode, for a typical 20 cm thickness. The respective increase factors were 6 and 4.2 when patient thickness rose from 16 to 28 cm, and by 10 and 8.3, when comparing cine acquisition with the low fluoroscopy mode. The knowledge of typical dose rates for each X-ray system in use in catheterisation laboratories is essential in order to optimise protection of patients and staff.

Body Constitution↗
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↗
PubMed2004

Optimization of variable temporal averaging in digital fluoroscopy.

In modern X-ray fluoroscopy systems, the amount of temporal averaging (i.e. persistence) applied to the image is often user selectable. The objective of this work is to quantify the effect of variable temporal averaging on the detection of low contrast test objects moving at a range of known speeds within the digital fluoroscopic image. An image intensifier system with a short-persistence television camera was used to record image sequences of a moving threshold contrast-detail diameter test object onto broadcast-standard U-matic videotape. The image sequences were replayed through an image processing system allowing different amounts of temporal averaging to be applied. The test images were scored by an experienced observer. The temporal averaging time constants produced by the added image processing were measured using a method based on noise correlation. Results are presented showing the trends of threshold contrast with test detail diameter and movement speed. The optimum value of temporal averaging time constant is presented as a function of detail diameter for a range of speeds. By comparison with the limited information available in the literature on organ movement, it is tentatively concluded that for the organ movement speeds expected in the abdomen, the optimum imaging system persistence time constant should be approximately 0.15 s. For the much greater speeds associated with cardiac motion no additional frame averaging, i.e. just the persistence provided by the observer's visual system, appears to be optimal.

Algorithms↗
PubMed2003

Short communication: Practical aspects for the evaluation of skin doses in interventional cardiology using a new slow film.

Mapping skin doses in complex fluoroscopy interventions is useful to determine the probability of a possible injury, to detect areas of overlapping irradiation fields and to obtain a permanent register of the most exposed patient skin areas. To fulfil this task, large films with slow X-ray response can be used. Recently, Kodak has introduced a new radiotherapy verification film, named EDR2 (Extended Dose Range). The aim of this paper is to analyse the possibilities of using this new film for estimating skin dose distributions in interventions with potentially higher doses, such as complex percutaneous transluminal coronary angioplasty (PTCA), intravascular brachytherapy procedures (IVB) or cardiac ablations. The EDR2 film by Kodak is an improved option to be used in interventional cardiology to obtain maps of patient skin doses and to estimate maximum skin doses up to 1400 mGy. Film kVp dependence is negligible and the processor conditions can be standardized to obtain skin dose estimations. The linear range for accurate dose measurements is from 50 mGy to 500 mGy.

Angioplasty, Balloon, Coronary↗
PubMed2001

Skin dose and dose-area product values for interventional cardiology procedures.

Coronary angiography and percutaneous transluminal coronary angioplasty procedures performed in four different facilities were monitored in the present study by measuring maximum skin dose, dose-area product and other operational parameters. Radiographic slow film, thermoluminescent dosemeters and transmission ion chambers were used to measure dose related quantities. Values of 107-711 mGy for maximum skin dose and 27.3-370.6 Gy cm2 for dose-area product were found, together with cumulative skin dose estimates of 110-3706 mGy. A discussion of the relationship of measured dose-area product and skin dose values is made using a field concentration factor defined as a way to interpret the findings. No general correlation was observed between dose-area product and maximum skin dose. Cumulative skin dose estimates throughout a procedure should be discarded as a realistic method for assessing deterministic risk in cardiology procedures. Slow film in addition to thermoluminescent dosemeters for measurement of maximum skin dose is a good alternative, especially for complex interventional procedures. For repeated procedures, combining film and dose-area product monitoring favours optimization of radiation protection for the patient.

Angioplasty, Balloon, Coronary↗
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↗
PubMed1996

Short communication: use of the European image quality criteria for screen-film comparison--application for asymmetric systems.

The aim of this study is the comparison of two different techniques of image evaluation: by phantom simulation and by patient anatomical criteria using those proposed in a European Union working document. Both methods of evaluation were applied to asymmetric and conventional screen-film systems. The European image quality criteria as a tool for comparing the use of image systems is a reasonably valid and objective method. However, a complete practical description of a system using complementary phantom images and test object is a convenient means of obtaining a comprehensive description of the system. Results show that sharpness of mobile organs and the visualization of the retrocardiac and retromammal lung, in posteroanterior projection, and vertex in lateral projection is improved with the InSight system. The phantom images suggest, however, an important loss of resolution and contrast.

European Union↗
PubMed1996

Patient doses in hysterosalpingography.

The results of a survey of doses imparted on 41 patients undergoing hysterosalpingography is presented. Dosimetric evaluations were carried out by measuring both the dose-area product using a transmission ionization type chamber, and the entrance surface dose using thermoluminiscent dosimeters. As a result, a local reference dose value was obtained for this examination. Correlations between the dose-area product and the entrance surface dose data were analysed and compared in order to find the most appropriate dosimetric procedure. The median dose-area product obtained was 713 cGy cm2 (range 247 cGy cm2-1623 cGy cm2). Ovarian doses were also calculated, and a median value of 4.6 mGy was obtained for the whole examination. Effective doses were estimated with a median value of 3.1 mSv, and a range of 1.0 mSv-8.1 mSv.

Adult↗
PubMed1995

Patient dose values in interventional radiology.

Large exposures incurred in interventional radiology procedures make it advisable to establish reference dose values. These dose values should be quoted in quantities representative of the radiological risk to the patient. In Spain, measurement methods were developed to comply with the European Directive on Patient Protection. Dose-area product and, when feasible, surface dose using thermoluminescent dosimetry chips were measured. Both approaches are discussed, as well as their potential use in patient protection programmes. Initial results are presented for a sample of 680 patients in 10 hospital centres in Spain. Mean, median and range are reported for some specific procedures. Mean values of 8750, 6651, 6663, 9292 and 6816 cGy cm2 are reported for percutaneous transluminal coronary angioplasty, coronary angiography, low extremity, renal and cerebral arteriographies, respectively.

Humans↗
PubMed1995

Image quality and dose in lumbar spine examinations: results of a 5 year quality control programme following the European quality criteria trial.

The large dose values found for lumbar spine examinations in a centre participating in the European quality criteria trial have been investigated within a 5 year quality control programme. Actions focused mainly on optimizing the focus-to-film distance, tube potential (kV), film optical density and X-ray beam filtration. These actions lead to overall dose reductions of up to 75% in lumbo-sacral joint examinations and prove the need for a regular survey of patient skin doses.

Humans↗
PubMed1995

Evaluation of the European image quality criteria for chest examinations.

The European Commission has published guidelines for image quality, radiographic technique and patient dose. These could be easily checked by staff either during the examination or when reporting the resulting radiographs. The objective was to achieve comparable image quality throughout Europe using optimum techniques. This paper presents an application of the image criteria for chest examinations. The application of criteria to a large number of films helps to correlate scoring films using this method with other alternatives such as the evaluation of physical parameters using phantoms or test objects. The advantages and limitations of the image quality list of criteria are discussed. As a result of its application, some modifications of image quality criteria, based upon simple essential indicators (minimizing the number of criteria) are formulated and presented.

Adult↗
PubMed1994

Image quality and patient dose for different screen-film combinations.

Comparisons of image quality and estimations of dose reductions were made for several new screen-film combinations including conventional and rare-earth systems under conditions similar to abdomen radiography. The evaluation was carried out using an ANSI type phantom and the TOR(CDR) image quality object developed by the University of Leeds. The parameters employed for the comparison were: entrance dose, high and low contrast threshold sensitivity and resolution. The advantages and limitations of the method are also discussed. Results show that images with high quality can be obtained with comparatively low patient doses, and that there are still wide differences in image quality for similar speed systems, depending on the manufacturer and on the chosen combination.

Calcium Compounds↗