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R Van Loon

Publications and source records attributed to R Van Loon.

11 recordsLinked to original sources
PubMed2006

Data analysis from a multi-centre, comparative study of angiographic examinations leading to practical guidelines for the optimisation of patient doses.

In this study, patient doses were analysed against exposure parameters and procedure protocol. Patient doses were measured in seven hospitals for a standard diagnostic vascular examination. Image quality was assessed using the contrast-detail phantom from Nijmegen (CD-DISC 2.0). A link between dose and image quality was investigated. Image quality strongly depends on the preset dose level. The higher the dose level, the better the image quality, but also the higher the patient dose. However, no clear correlation was found between total dose-area product (DAP) or effective dose and image quality. A large range in patient dose was found: DAP (22-130 Gy cm2) and effective dose (3.9-16.8 mSv). A difference in number of frames was also found in the different centres, owing to different frame rates (3-2-1 frames per second) and use of oblique projections. Differences in doses and exposure settings offer the possibility of optimising patient doses in angiography and interventional radiology.

Angiography↗
PubMed2005

Skin dose measurements on patients for diagnostic and interventional neuroradiology: a multicentre study.

The present study reports on the skin dose measurements on patients undergoing diagnostic and interventional neuroradiology procedures. Grids of thermoluminescence dosemeters were attached on the head of the patient. The exposure parameters of the X-ray systems and the clinical procedures were fully documented. While for the diagnostic procedure, the dose threshold of 2 Gy for deterministic effects was not reached, this situation was much different for the embolisations. For angiography of the carotid arteries, no skin doses were measured >320 mGy. For the cerebral embolisations, maximum skin doses up to 5.4 Gy were measured. Doses to the patients varied largely between different hospitals and within the same hospital for similar procedures. On the one hand, the complexity of the pathology for interventional procedures was responsible for the large variability in dose. On the other hand, large differences in clinical protocol and technical parameters of the X-ray systems, explaining the dose variations, were also observed. A correlation was found between the maximum skin dose measured on a patient and the total dose-area product (DAP) value for cerebral embolisations. This correlation makes it possible to estimate the maximum skin dose from these DAP values and to determine a trigger level. In conclusion, management of patient doses in interventional radiology requires training, specialisation and well-documented procedure guidelines.

Brain↗
PubMed2005

Effective doses in angiography and interventional radiology: calculation of conversion coefficients for angiography of the lower limbs.

The present study reports on investigations that we have performed to allow the calculation of effective doses (E) in interventional radiology. The use of published conversion tables might not allow sufficient guidance for the establishment of optimization strategies for procedures in interventional radiology. With the Monte Carlo N-Particle transport code (MCNP4B), conversion coefficients, linking dose-area product (DAP) measurements with E, are calculated for angiography of the lower limbs in six hospitals. The influence of various parameters on the calculation of these conversion coefficients is studied in a systematic way using the 2(n) factorial design. In this design the effect of different parameters and their pair-wise interactions on a certain variable is explored. In our study, the relevant parameters are tube potential, total filtration and field size and position. We concluded that the influence of radiation spectrum (kVp + filtration) is large and that the effect of field position and size is moderate, except when differences are observed in respect of the gonads. In that case, the variation in conversion coefficients is large. The results of this statistical analysis are then applied to the differences observed between the conversion coefficients, calculated for angiography of the lower limbs in the six hospitals. Recommendations for optimization of patient doses are given.

Adolescent↗
PubMed2000

Periaortitis and aortic dissection due to Wegener's granulomatosis.

We describe here a patient with abdominal periaortitis and intramural dissection as early manifestations of Wegener's granulomatosis (WG). Surgical biopsies taken from the retroperitoneal inflammatory tissue surrounding the aorta showed granulomatous vasculitis. The patient had antiproteinase-3 antibodies and suffered from nasal, pulmonary, nervous and renal WG involvement. Although being a vasculitis of medium size and small vessels, WG should be included in the systemic vasculitides which can give rise to (peri)aortic inflammation.

Adult↗
PubMed1997

Quality assurance in conformal radiotherapy: DYNARAD consensus report on practice guidelines.

BACKGROUND AND PURPOSE: Conformal radiotherapy has only recently been widely implemented. Although not all aspects have yet been adequately proven, it is generally recognized that maintaining a high degree of precision throughout the process is critical to the treatment outcome while the focus for quality assurance and quality improvement will need to concentrate more on human factors, procedures, communication, organization and training. A general consensus document on quality assurance guidelines for institutions that deliver conformal radiotherapy treatments to patients has been elaborated within the framework of the DYNARAD/BIOMED concerted action on conformal radiotherapy. The present paper aims to highlight those issues that were identified as of specific importance to conformal radiotherapy. The work reported here further details this guidance by direct correlation with the issues involved in the special case of conformal radiotherapy. METHODS: The DYNARAD document has been drafted in the form of a desktop guide comprising six sets of guidelines and is based on the ESTRO advisory report on 'Quality Assurance in Radiotherapy'. RESULTS AND CONCLUSIONS: The document has been endorsed by the DYNARAD group of institutions. As such it can form the basis for further discussions and enter into the subsequent phase of expanding its consensus basis.

Consensus Statements as Topic↗
PubMed1997

The role and contribution of a medical physicist in a radiology department.

This report aims to present the rationale for the integration of a medical physicist in large radiology departments, based on legal regulations and underlying scientific arguments. Examples of contributions of medical physicists are given in the field of radiation monitoring of the patient, occupational exposure of staff, quality assurance programs and technical quality control, together with the role of the physicist in education and in medical research and his contribution to the economics of the department.

Cost Control↗
PubMed1995

Quality control in mammography: practical implications.

The programme "Europe against cancer" stimulated, among other activities, breast screening activities in the member states. From the beginning, it was clear that a rigorous and efficient approach required the highest possible quality of the three major components of a breast screening programme: the medical performance (correct positioning, training of the medical staff, double reading of the mammograms and feedback from the pathologist and the epidemiologist), the organisation (attendance rate, data base) and the quality of the imaging process (compliance of the image quality and the breast dose with the CEC document of 1990). The first part of this paper will be limited to the latter component and the second part to the subject of correct positioning of the breast.

Female↗
PubMed1995

Technical quality control in mammography screening: first results in Belgium.

In this paper the first results of the application in Belgium of the European protocol for the technical quality control of mammography screening are presented. Twelve mammography screening units were submitted to an acceptance test: one fourth complied with the criteria after a second visit. A daily quality control procedure has been run since eighteen months. The most important detected problems are given and discussed. The European Commission, in the framework of "Europe Against Cancer", recently published the "European Guidelines for Quality Assurance in Mammography Screening" (1). In another contribution (2), a brief overview of the important appendix "European Protocol for the Quality Control of the Technical Aspects of Mammography Screening" was given. In this paper the first results for the application of this protocol in Belgium are presented.

Female↗
PubMedDate not supplied

The influence of the ambient temperature on tumour growth, metastasis and survival in mice.

The effect of ambient temperature was analysed on the behaviour of MO4 cells which are malignant, invasive and metastasizing C3H mouse fibroblastic cells when implanted in the tail of the syngeneic animal. Raising the ambient temperature to 28 degrees C increases growth of the primary tumour, incidence of metastases and shortens survival. Lowering the ambient temperature to 13 degrees C prevents all these phenomena. Measurements at the implantation site show that the temperature of the tail remains in a range +/- 2-3 degrees C in accordance with the environment. From these results we conclude that room temperature may be important when experiments are performed in vivo.

Animals↗