[en] Absolute magnitudes and slope parameters for 69 asteroids have been derived with data from the Asteroid Photometric Catalogue. We present a generalized HG-system allowing calculation of a separate H-value for each opposition with a slope parameter G in common to all apparitions. The mean slope parameters for asteroids in our sample are (G)_s = 0.23±0.02, (G)_M = 0.23±0.01, and (G)_C = 0.05±0.02 for taxonomic types S, M, and C, respectively. The magnitude data in the Asteroid Photometric Catalogue is in general well described by the HG-system

[en] This is the first in a series of papers where we use data in the Asteroid Photometric Catalogue to derive physical information about asteroids. Here we describe the basic reduction technique performed to obtain composite lightcurves and their Fourier expansions. Special attention is paid to the error analysis which is of high importance for applications since the data base is very inhomogeneous in quality

[en] A comprehensive tabulation of asteroid pole orientations is presented. The information given includes asteroid number, pole coordinates, sense of rotation, sidereal period, and model on which pole determination is based. 104 refs

[en] In external radiation therapy, treatment planning is routinely performed on 3D Treatment Planning Systems (TPS). The absorbed dose distribution in the patient is calculated with the TPS and the treatment is administered according to the plan. Considering that the TPS-calculated dose has been shown to deviate from the actual dose distribution in various situations, there is doubtless a need for a realistic verification system. The dosimeter gel, based on ferrous sulphate and agarose and evaluated using Magnetic Resonance Imaging (MRI), can be used to measure the complete dose distribution in many situations. It is a mouldable tissue equivalent dosimetry system which has previously lacked a sufficient overall precision for verification purposes (5-10%). Using the same gel composition as previously with a new MRI system and a new MRI acquisition protocol, dose distributions from both photons and electrons were measured. The precision in the dose determination was evaluated. Comparison with TPS calculated results as well as diode measurements were performed. In this study the system's relative dose determination precision has been significantly improved and was found to be better than 3%. When examining the potential of the gel dosimetry system as a verification tool of TPS calculations, measured and calculated depthdose curves, dose profiles and isodose lines were compared for both photons and electrons. In the depthdose curves, only small variations were found (<2% at treatment depth). Larger deviations (>5%) were seen in the penumbra region of the electron beam when comparing measured and calculated profiles. The dosimeter gel seems to be a promising tool for verification of TPS calculations as measurements can be performed with high precision

[en] The principles of asteroid light-curve inversion are discussed together with basic principles involved in approaches for deriving asteroid pole and shape parameters from photometry data. The merits of various pole determination techniques are described and compared. Results obtained so far on the pole orientations and shapes of asteroids are presented. 78 refs

[en] Purpose: To investigate whether three-dimensional rotational angiography (3D-RA) of the transplant renal artery performed with an extended angle of rotation can reduce beam-hardening artifacts in 3D reconstructed images without image quality being lost or side effects to the transplanted kidney being increased. Material and Methods: 3D-RA with a C-arm rotation of 180 deg was performed consecutively in 12 renal transplanted patients with suspicion of renal artery stenosis. A 1.7-mm balloon occlusion catheter was placed using the crossover technique and this was compared to a protocol with 160 deg rotation and a traditional 1.4-mm catheter in 10 patients. The occurrence of beam-hardening artifacts was registered and the effects of the reduced contrast load on image quality and of arterial occlusion on renal function were assessed. Results: The extended angle of rotation, from 160 deg to 180 deg, reduced the beam-hardening artifacts. Artifacts were observed in 4/11 patients (36%) in the study group and in all 10 (100%) of the controls. There was no statistical difference regarding image quality between the two protocols. Renal function was equally affected in both protocols. Conclusion: 3D-RA with an extended C-arm rotation reduced the beam-hardening artifacts. Image quality was not reduced despite the reduced contrast medium load. The different protocols had no effect on patient outcome

[en] Extensive fuel fragmentation of high burnup fuel may occur in a LOCA transient. SCIP III studies fuel fragmentation and successfully delivers new experimental data on the thresholds and new understanding of the mechanism. SCIP III also delivers data on cladding behaviour in overheating transients and axial strength during quench. The program include san integrated modeling effort.

[en] The data on 37 asteroids obtained with the Calsberg Automatic Meridian Circle at La Palma have been used to obtain the photometric parameters G and H and to draw phase diagrams. This supplements data on 51 asteroids and on 31 asteroids using the same techniques. Synodic periods were obtained for 6 asteroids and composite lightcurves drawn. For 10 Hygiea our value of 17.5 hours is different from that of Vesely and Taylor (1985) but in agreement with the result reported by Harris and Young (1983). 24 asteroids were of type S and the mean value of 0.19 agrees very well with that of Lagerkvist and Williams (1987) and Lagerkvist et al. (1988). For the 6 asteroids of type C we get a mean G value of 0.04 agreeing well with earlier results

[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] A method for analysing and comparing treatment planning system (TPS) data and ferrous dosimeter gel measurements evaluated with MRI (FeMRI) was developed, including image processing to final absorbed dose images. Measurements were analysed according to this method and FeMRI data were thereby compared with the TPS-calculated dose distribution. For photons, differences between FeMRI- and TPS dose data were mainly within ±2%. Minor shortcomings found in both the FeMRI system and the TPS are explained and discussed. For electron beams, there was an overall good agreement. It was found that the TPS underestimates the lateral scattering dose outside the primary beam, but the reported dose difference corresponds to a small spatial deviation (less than 2 mm). It is important to consider this single beam data comparison when the method is extended to more complicated situations, for example when using several beams. (orig.)