The feasibility of in vivo quantitative imaging in (223)Ra therapy was confirmed. The lesion uptake of (223)Ra-dichloride was significantly correlated with that of (99m)Tc-MDP. The D RBE to lesions per unit administered activity was much higher than that of other bone-seeking radiopharmaceuticals, but considering a standard administration of 21 MBq (six injections of 50 kBq/kg to a 70-kg patient), the mean cumulative value of D RBE was about 19 Gy, and was therefore in the range of those of other radiopharmaceuticals. The macrodosimetry of bone metastases in treatments with (223)Ra-dichloride is feasible, but more work is needed to demonstrate its helpfulness in predicting clinical outcomes.
The 64-MDCT scanner diagnostic performance for coronary CT angiography is further improved with better spatial and temporal resolution and faster scan times; besides, initial clinical results are promising. The use of dose-reducing acquisition techniques is mandatory to limit radiation exposure to the patient.
A method is introduced for the evaluation of x-ray spectra from x-ray machines operating in the range 50-100 kVp using a cadmium telluride (CdTe) detector with low detection efficiency. The pulse height distribution obtained with this kind of detector does not represent the true photon spectra owing to the presence of K-escape, Compton scattering, etc.; these effects were evaluated using a Monte Carlo method. A stripping procedure is described for implementation on a Univac 1100/82 computer. The validity of our method was finally tested by comparison with experimental results obtained with a Ge detector and with data from the literature; the results are in good agreement with published data.
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