Calibration of dosemeters used in mammography with different X ray qualities: EUROMET project no. 526

The effect of different X ray radiation qualities on the calibration of mammographic dosemeters was investigated within the framework of a EUROMET (European Collaboration in Measurement Standards) project. The calibration coefficients for two ionization chambers and two semiconductor detectors were established in 13 dosimetry calibration laboratories for radiation qualities used in mammography. They were compared with coefficients for other radiation qualities, including those defined in ISO 4037-1, with first half value layers in the mammographic range. The results indicate that the choice of the radiation quality is not crucial for instruments with a small energy dependence of the response. However, the radiation quality has to be chosen carefully if instruments with a marked dependence of their response to the radiation energy are calibrated.     

Culture of Helicobacter pylori from gastric biopsies transported in biopsy urease test tubes

Gastric biopsy specimens of 57 consecutively observed dyspeptic patients were studied for the presence of Helicobacter pylori by histological examination, biopsy urease test (BUT) and culture. For culture, biopsy samples were transported in both Stuart media and BUT tubes. All 15 isolates could be cultured from both Stuart and BUT tubes. Thus, if the main reason for culture of Helicobacter pylori is for antimicrobial susceptibility testing, only positive BUT tubes need to be submitted. This would reduce both the expense and the number of biopsies needed.     

A multicarrier QAM modulator for WCDMA base-station with on-chip D/A converter

In this paper, design and implementation of a multicarrier quadrature amplitude modulation (QAM) modulator for a wideband code division multiple access (WCDMA) base-station with a 14-bit on-chip D/A converter is described. The modulator is capable of modulating four carriers with four independent in phase (I) and quadrature (Q) data streams. The proposed modulator structure consists of an interpolation chain for data streams and four digital frequency synthesizer/modulators, which are based on a coordinate rotation digital computer (CORDIC) vector rotation algorithm. The interpolation chain consists of a root-raised cosine pulse shaping filter and three half-band filters for image filtering. The modulated carriers are combined to form a multicarrier WCDMA signal. The SINC-attenuation effect of a digital/analog (D/A) converter is canceled by an inverse-SINC predistortion filter. The multicarrier signal is converted to the analog domain with a 14-bit current steering D/A converter, which is integrated on the same silicon chip. The modulator is implemented with a 0.35-mum BiCMOS process with CMOS transistors only     

A 14-bit Current-Steering DAC with Current-Mode Deglitcher

A 14-bit current-steering DAC utilizing parallel current memories operating as a deglitcher is presented. The high linearity of the current memories is based on a memory MOS transistor biased in the triode region and a bootstrapped sampling switch. The prototype circuit is implemented using a 0.35-m BiCMOS (SiGe) technology and it occupies 5.7 mm² of silicon area. According to measurements, THD is –66.8 dBc with a 9.1-MHz input signal and 30-MHz clock frequency. Two-tone test gives intermodulation levels below 68 dBFS at 40-MS/s sampling rate. The power dissipation is 370 mW from a 3-V supply.     

A simple method for measurement of angiotensin II in plasma

A simple radioimmunological (RIA) method for the determination of angiotensin II in 0.5-1.0 ml samples of plasma is described and carefully evaluated. Before RIA was performed, the interfering plasma proteins were eliminated by ion exchange chromatography, and recovery from every column was checked with a small amount of [125I]angiotensin II. The sensitivity of the method was 4.0 ng/l; the coefficient of intra-assay variation was 10.0% and that of inter-assay variation 12.1%. Accuracy was studied both by adding various amounts of angiotensin II to plasma samples and by diluting plasma containing angiotensin II with the RIA buffer. Both studies gave very good correlations between found and expected values (r=0.998 and r=0.987). In a normal material (n=36), the mean angiotensin II concentration at 8 a.m. after 2 h ambulation 42.4 +/- 12.8 (S.D.) ng/l. Because the present method is accurate, precise, and practical, and allows measurement of angiotensin II in small samples, it seems useful for routine as well as for research work.     

A direct digital synthesizer with an on-chip D/A-converter

A direct digital synthesizer (DDS) with an on-chip D/A converter is designed and processed in a 0.8 μm BiCMOS. The on-chip D/A converter avoids delays and line loading caused by interchip connections. At the 150 MHz clock frequency, the spurious free dynamic range (SFDR) is better than 60 dBc at low synthesized frequencies, decreasing to 52 dBc worst case at high synthesized frequencies in the output frequency band (0-75 MHz). The DDS covers a bandwidth from DC to 75 MHz in steps of 0.0349 Hz with the frequency switching speed of 140 ns. The chip has a complexity of 19100 transistors with a die/core area of 12.2/3.9 mm². The power dissipation is 0.6 W at 150 MHz at 5 V. The maximum operating clock frequency of the chip is 170 MHz     

Development of training syllabi for radiation protection and quality assurance of dual-energy X-ray absorptiometry (DXA) systems

The use of dual-energy X-ray absorptiometry (DXA) scanners for measuring bone mineral density (BMD) is on the increase. A single DXA scan is a relatively low-dose diagnostic X-ray examination; however, radiation protection (RP) issues should not be trivialised. One objective of the EU 6th Framework SENTINEL co-ordination action was to develop training syllabi in RP and quality assurance (QA) for BMD, and this study presents the results. An EU-wide survey was carried out which confirmed that there was a need for an accredited DXA RP training course in many EU states. There is also limited published guidance on acceptance testing/QA for DXA. Two training syllabi were developed: one on RP and one on QA of DXA systems. A training course was delivered in Ireland in 2006 by the Medical Physics & Bioengineering Department of St James's Hospital, Dublin. Following the training course, a PC-based training CD was developed and will be made available. A harmonised approach to training will promote consistent approaches to radiation safety across the EU.     

Proposal for a patient database on cardiac interventional exposures for epidemiological studies

Relatively high organ doses absorbed by patients in interventional cardiology suggest the opportunity to define these patients as a cohort to be followed forward in time in an epidemiological study of the cancer risks associated with exposure to low-dose ionising radiation. In this paper, the UNSCEAR 2000 Report risk estimates for the most exposed organs/tissues in cardiac interventional procedures are reviewed, as well as the critical features of such an epidemiological study that is anticipated to have an intrinsically low statistical power because of the low levels of risk and possible confounding factors. To overcome these limitations, data collected in different institutions can be combined provided that a common design and conduct are used for dose assessment. A minimum dataset to be collected on a patient basis is proposed that can be implemented routinely in most facilities. This data should be linked to the local patient information system in order to retrieve all the exposures of a given patient.     

Results of a European survey on patient doses in paediatric radiology

Paediatric patients represent a very specific group within the radiology department. Compared to adult patients, they are more sensitive to radiation. As they are sometimes submitted to several radiology procedures, dose and image quality should be well balanced. Nowadays, only a few centres specialize in paediatric imaging, and knowledge of paediatric patient doses is, therefore, very scattered. The effect of the introduction of digital technology on paediatric patient doses remains largely undocumented. Data collected in the present survey illustrate that there is a clear need for standardisation in this domain. The proposal of a European diagnostic reference level (DRL) is quite difficult. Preliminary DRLs, based on typically 5-7 radiology centres per examination are proposed. The 'effective dose' may or may not be a very rigorous parameter, but it still remains useful nowadays to calculate a parameter that summarises the possible radiation-induced detriment to these young patients. However, conversion factors for calculation of the effective dose should be harmonised. Future studies should include an image quality evaluation study, using criteria that account for digital equipment. Data collection would be straightforward and could be performed in a systematic and automatic way if DICOM headers of digital images would include appropriate as well as relevant information for the particular case of paediatric examinations.