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BACKGROUND: Prostate brachytherapy consists in placing radioactive seeds for tumour destruction under transrectal ultrasound imaging (TRUS) control. It requires prostate delineation from the images for dose planning. Because ultrasound imaging is patient- and operator-dependent, we have proposed to fuse MRI data to TRUS data to make image processing more reliable. The technical accuracy of this approach has already been evaluated. METHODS: We present work in progress concerning the evaluation of the approach from the dosimetry viewpoint. The objective is to determine what impact this system may have on the treatment of the patient. Dose planning is performed from initial TRUS prostate contours and evaluated on contours modified by data fusion. RESULTS: For the eight patients included, we demonstrate that TRUS prostate volume is most often underestimated and that dose is overestimated in a correlated way. However, dose constraints are still verified for those eight patients. CONCLUSIONS: This confirms our initial hypothesis.

Cadmium is known to accumulate in the human body and chronic exposures have been clearly linked to adverse health effects, showing the kidney as the critical target organ. However, there is evidence of an association between extensive environmental exposure to cadmium and alterations in bone/calcium metabolism. Therefore, it is desirable to be able to measure bone cadmium non-invasively in humans. Tibia was selected as a measurement site and source-excited K-shell x-ray fluorescence was investigated both experimentally and computationally. Initially the 88 keV gamma-rays from Cd-109 were used to assess minimum detectable level (MDL) of cadmium in phantoms comprising plaster of Paris (bone) and wax (soft tissue). An MDL of 3-4 mu g g(-1) was achieved for overlying tissue thicknesses of up to 5 mm. Alternative sources were I-125 and Am-241. Monte Carlo simulation showed that the spectral contrast for I-125 would be poor. The 60 keV gamma-rays from Am-241 were more promising, provided that the 26 keV gamma-rays were filtered out. Experiments with Am-241 confirmed that a lower MDL could be achieved. However, the product of MDL and square root of dose (a figure of merit) was not improved. Since effective doses for these source-excited x-ray fluorescence procedures are low (typically of the order of 0.1 mu Sv or less), it may be that lower MDL would be preferred over lower dose. Nevertheless, development continues as a further reduction in MDL is highly desirable. Copyright (c) 2005 John Wiley & Sons, Ltd.

Paz, Teatro (2ª ed.), Te digo, Nuño, que nuestro amo (p. 3)... ¡Ah! (p. 206), Aprobada

Paz, Teatro (2ª ed.), Necio de mí, y que haya tenido atrevimiento (p. 3)... señores, si en algo les ofendí! (p. 147), Aprobada