Search PubMed⌕ Search

Biomedical subjects

H Gfirtner

Publications and source records attributed to H Gfirtner.

At least 19 recordsLinked to original sources
PubMed2005

Estimation of patient doses for common diagnostic X-ray examinations in Latvian hospitals, analysis of radiographic techniques and comparison with European guidelines.

This article deals with the estimation of doses received by patients undergoing radiological examinations in order to establish dose reference levels (DRLs) in Latvia. Several large hospitals, small hospitals and private practices were selected for patient dose measurements. The measurements were carried out using calibrated thermoluminiscence dosemeters attached to the patient's skin. Exposure parameters and patient's data were recorded. The entrance surface doses (ESDs) to patients undergoing several common X-ray examinations (chest AP/PA, chest LAT, lumbar spine AP/PA, lumbar spine LAT and pelvis) were measured. Data concerning the kV(p) settings, used type of films, focus-film distance and the ESD values were analysed and compared with those recommended by the European Community (EC). Among the different hospitals and private practices, discrepancies in the patient doses and techniques used for the examination were found, where the doses exceeded the EC recommended values owing to a very low kV(p) and a very low sensitivity of the screen film combinations used.

Body Size↗
PubMed2004

[Staff requirements in medical radiation physics for diagnostic radiology in Germany: results of a questionnaire].

To get a general idea of the actual staffing situation in medical radiation physics, all active members of the German Society of Medical Physics (DGMP) were surveyed by the task force "staff requirements" ("Personalbedarf") of the DGMP in 1999. Of the 322 forms sent out, 173 could be evaluated. The staff requirements in medical radiation physics were calculated from the major elements of the radiology equipment and from the staff responsibilities as defined in the DGMP Reports 8 and 10, and compared with the actual number of staff members. The data of this spot check were then extrapolated for the entire Federal Republic of Germany. The calculation revealed a deficit of 89% for the entire staff in diagnostic radiology and of 84% for physicists. Considering the age distribution of the DGMP members, a training capacity of about 100 medical physicists per year is needed to eliminate the calculated deficit within the next 10 years.

Germany↗
PubMed2004

[Investigation of the entrance dose of standardized chest radiographs].

In 50 chest radiographs obtained in PA projection with the patient erect and the radiographic techniques kept constant, entrance dose, entrance surface dose and dose area product were measured and compared with the measurements obtained with Plexiglas and Alderson phantoms. Following the recommendations of the International Commission on Radiological Protection, the "absorbed dose in air" at the point of intersection of the X-ray beam with the surface of the patient was used as reference. For patients with the same diameter, the measured dose deviated up to +/- 50 % from the "Reference Man" according to the ICRP 23 as well as from the "Representative Patient" according to the ICRP 73. The exposure data produced by the equipment corresponded to the measured values with minor deviations, but the dose values expressed as entrance surface dose showed major deviation in comparison with the entrance dose due to differences in the back-scatter factor. The values of entrance dose calculated from the dose area product measurements showed additional uncertainties due to different field sizes. Moreover, a sex-specific dose area product value was identified. These results reveal that the values of the "ICRP Reference Man" differ in many situations from the values produced by the examined patient due to differences in radiation transmission. This has consequences for determining diagnostic reference values and investigating recorded radiation exposure. This will be explained and substantiated.

Humans↗
PubMed2002

[Examination of the constancy of the medium optical density of conventional chest radiographs].

PURPOSE: To determine whether the medium optical density of conventional chest radiographs is constant. MATERIALS AND METHODS: 47 PA chest radiographs were digitized to measure the optical density and its dynamic range of normal and pathologically altered lungs. RESULTS: For constant exposure factors and a correctly positioned region of interest, the medium optical density deviates only minimal despite differences in AP chest diameter, entry dose and dynamic range, and is largely independent of the pathologic pulmonary findings. CONCLUSION: Digitization of the radiograph enables the determination of the physical parameters used to operate the imaging system, such as medium optical density, image contrast, image latitude and density distribution, in accordance to the guidelines of the German Medical Association. If the region of interest encompasses the clinically relevant region of the lung, the measured value of the optical density corresponds with only minor variation to the average value of the entire lung region.

Absorptiometry, Photon↗
PubMed1997

A new Diamentor for measuring kerma-area product and air-kerma simultaneously.

The new M4KDK Diamentor (PTW-Freiburg) for measuring the air-kerma-area product (KAP) and air kerma (AK) simultaneously was evaluated. The special design of the Diamentor chamber influences the variation of the calibration factor with respect to the field size somewhat differently to what is the case with the classic Diamentor. It is therefore recommended that calibration be performed for a larger field size. If the M4KDK Diamentor is calibrated for a field size of 3.8 cm x 3.8 cm (at the chamber), an uncertainty in the AK value of better than 15% for a field size larger than the calibration field, can be expected. The influence of backscattered radiation on the calibration factor is equivalent to that for the classic Diamentor chamber. The variation in response in accordance with tube potential, is also comparable with that of the classic Diamentor. Dramatic changes in response have to be expected if additional filters are introduced in close proximity to the Diamentor chamber.

Biophysical Phenomena↗
PubMed1996

Quality assurance in radiotherapy: the importance of medical physics staffing levels. Recommendations from an ESTRO/EFOMP joint task group.

The safe application of ionising radiation for diagnosis and therapy requires a high level of knowledge of the underlying processes and of quality assurance. Sophisticated modern equipment can be used effectively for complicated diagnostic and therapeutic techniques only with adequate physics support. In the light of recent analyses and recommendations by national and international societies a joint working group of representatives from ESTRO (European Society for Therapeutic Radiology and Oncology) and from EFOMP (European Federation of Organisations for Medical Physics) was set up to assess the necessary staffing levels for physics support to radiotherapy. The method used to assess the staffing levels, the resulting recommendations and examples of their practical application are described.

Europe↗
PubMed1996

[The personnel needs of health physics in radiotherapy].

METHODS AND RESULTS: Using a questionnaire, mean occupation time values for the different medical physics activities were derived in 1992; they formed the basis for recommendations of minimum physics staffing levels in radiotherapy. The recommended staffing levels were compared with the actual staffing levels and to other national and international recommendations.

Germany↗
PubMed1995

[ROKO--computer-assisted roentgen quality control].

To guarantee the quality of 30 x-ray machines and 8 photographic processors 24,000 data are collected yearly. A computer system is introduced (ROKO-Röntgenkonstanzprüfung) which helps to collect the monthly data easily and to measure on-line dose and voltage. If given tolerance values are exceeded acoustic and graphic warnings appear, a trend analysis is made to assure the correctness of the collected data, a generator to design the layout of check form facilitates the controlling and an on-line documentation for each x-ray machine is available. All these features help save time and money.

Computer Graphics↗
PubMed1981

Radiotherapy planning using computed tomography.

A critical look at the use of computed tomography (CT) for radiation therapy planning shows problems which all arise from incorrect positioning of the patient. CT is an excellent tool for therapy planning if the patient is positioned identically at the CT scanner and on the therapy couch. This is accomplished by installing matching laser systems at the CT scanner and at the therapy machine. The authors' planning procedure is discussed in detail.

Humans↗
PubMed1981

[Monitoring of radiation via CT (author's transl)].

The results presented in this article lead to the conclusion that it would be appropriate to demand control or monitoring of radiation via CT whenever complicated exposure to radiation is required. Such control appears mandatory in order to guarantee a sufficiently high tumour dosage and satisfactory protection or minimum burdening of the surrounding tissue. At first sight, it may seem that such CT operations are relatively costly. However, once the teamwork has been properly established, both the time required and the cost involved remain within reasonable limits and will probably not be greater than control via therapy simulator. The decisive factor is that computerised tomography should offer sufficient possibilities of translating such control into reality by effecting the necessary dosage adjustments in accordance with given requirements.

Esophageal Neoplasms↗
PubMed1979

[Therapy planning at the CT (author's transl)].

A therapy planning system was installed in a computer tomography hardware. This configuration has some advantages for treatment planning: 1. CT-images and isodoses can be overlaid. 2. Using skin markers in the computer tomography the actual therapy can easily be checked. 3. This method offers a good method for recording isodoses and anatomic cross sections simultaneously.

Humans↗