[en] The use of borosilicate-glass-capillary optics at a chosen wavelength for low scattering has been explored using an undulator beam at the ESRF. With a 2.3 μm beam at 0.092 nm wavelength, a silver behenate powder sample was scanned in two dimensions with a 2 μm step width. Scattering from single crystallites with d₀₀₁ = 5.83 nm could be observed. The limit for observation, at low angles, was ca s ≅ 0.1 nm^-1 (s = l/d for d ≅ 10 nm). (au) 10 refs

[en] With the opening of the first real 'third-generation' synchrotron source in Grenoble, in fall 1994, X-ray sources of unprecedented brilliances and qualities became available to the scientific community. Different X-ray analytical techniques could now be applied on a level that was unimaginable only a decade ago. Here are some preliminary results from an experiment where different analytical techniques have been applied on a micrometer level carried out at the most powerful synchrotron microbeam currently available in the world, the microfocus beamline (BL1) at ESRF. This beamline can now provide micrometer-sized X-ray beams with a flux density up to 10¹⁰ photons μm^-2 at an energy of 13keV and with a bandwidth of 10^-4. In this experiment, X-ray diffraction and X-ray fluorescence have been combined in order to obtain a precise and comprehensive micro-analytical description of micrometer-sized fly-ash particles. These types of particles are heavily inhomogeneous with a very irregular shape that makes them inaccessible to conventional micro-analysis. The experiment was performed in a scanning mode and two-dimensional images of different analytical information were reconstructed from the data recorded during the scan. The major features and limitations of this micro-analytical technique will be outlined and different examples on how the analytical information can be used for generating two-dimensional images of the sample will be demonstrated and discussed. (au) 15 refs

[en] Short communication

[en] Full text: To investigate the feasibility of using polymer gel for verifying the 3D dose distribution generated by intensity modulated treatment planning. A gel-filled spherical glass phantom was CT-scanned. A C-shaped target that circumscribed an organ at risk was defined and an intensity modulated treatment plan with seven coplanar fields was generated using the Helios software (Varian Medical Systems). Intensity modulation was achieved by the sliding-window technique and irradiation of the phantom was performed using a linear accelerator (Varian 2300 C/D) with a 120 leaf dynamic MLC. The prescribed dose to the target volume was 7.35 Gy (±5%, 7 to 7.7 Gy). The dose to the organ at risk (OAR) was planned to be below 7 Gy and no more than 30% of the OAR volume received above 80% of the prescribed target dose. After irradiation the gel phantom was evaluated in an MR scanner (Magnetom Vision, 1.5 T) using a multi echo sequence and a slice thickness of 3 mm. The measured gel dose distribution was compared with the calculated dose distribution with regard to absorbed dose distribution, dose volume histograms (DVHs) and dose profiles. The separation in absorbed dose between the target region and the OAR is larger for the calculated plan than for the measurement made using polymer gel. This can be seen both in dose distributions, DVHs and dose profiles. There are several factors that can explain these discrepancies, including methods for MR-evaluation, image processing and matching. There are also uncertainties in the calculation of the treatment planning system when the target size is small in relation to the MLC leaves, as is the case in this study. We conclude that the method presented is promising for verification of 3D dose distributions in IMRT applications. However, further studies are needed as well as comparisons with other detector systems such as ionisation chamber, film and TLD. Copyright (2000) Australasian College of Physical Scientists and Engineers in Medicine

[en] Complex intensity-modulated radiation therapy (IMRT) treatment plans require rigorous quality assurance tests. The aim of this study was to independently verify the delivered dose inside the patient in the region of the treatment site. A flexible naso-gastric tube containing thermoluminescent dosimeters (TLDs) was inserted into the oesophagus via the sinus cavity before the patient's first treatment. Lead markers were also inserted into the tube in order that the TLD positions could be accurately determined from the lateral and anterior-posterior electronic portal images taken prior to treatment. The measured dose was corrected for both daily linac output variations and the estimated dose received from the portal images. The predicted dose for each TLD was determined from the treatment planning system and compared to the measured TLD doses. The results comprise 431 TLD measurements on 43 patients. The mean measured-to-predicted dose ratio was 0.988 ± 0.011 (95% confidence interval) for measured doses above 0.2 Gy. There was a variation in this ratio when the measurements were separated into low dose (0.2-1.0 Gy), medium dose (1.0-1.8 Gy) and high dose (>1.8 Gy) measurements. The TLD-loaded, naso-oesophageal tube for in vivo dose verification is straightforward to implement, and well tolerated by patients. It provides independent reassurance of the delivered dose for head and neck IMRT.

[en] A compact, light weight and relatively inexpensive μ-XRF instrument that allows for non-destructive and local analysis of sub-mm samples with minor/trace level sensitivity was developed. Two versions of this prototype instrument exist: a table-top version that can be used in a laboratory environment while for in situ measurements a readily transportable version was constructed. Polycapillary lenses are used to focus the primary X-ray beam down to the level of 70-100 μm in diameter. Relative detection limits of transition elements in biological and glass matrices are situated at the 10-100 ppm level. These instruments are useful for characterization of various materials from the cultural heritage and forensic sector

[en] A novel capillary optics technique for focusing synchrotron X-ray beams has been applied in an experiment performed at the DORIS storage ring at HASYLAB. This new technqiue, which utilizes the total reflection properties of X-rays inside small capillaries, has recently been applied to generate microbeams of X-rays, with a beam size down to about 10 μm using conventional X-ray tubes. The result from our recent experiment shows that capillary optics can also be used to generate a submicron beam of X-rays from a synchrotron light source. A description of the capillary unit, and the alignment procedure is given. The influence of the thermal load on the device caused by the intense flux of synchrotron radiation will be discussed. Future perspectives of the capillary techniques as applied to synchrotron radiation will be discussed. (orig.)

[en] The fluorescence X-ray scanning 2D microprobe based on a Bragg-Fresnel multilayer lens (BFML) has been tested at the ESRF, Grenoble (France) for the first time. A single elliptical BFML has been used for two-dimensional focusing of the X-ray synchrotron beam of an undulator source in the energy range of 12 keV. A spatial resolution of 2.4 μm and a photon intensity of about 10¹⁰ photons per second have been measured using a Cr knife-edge test object. ((orig.))