The use of photostimulable phosphor systems for periodic quality assurance in radiotherapy.

The fusion of radiological and optical images can be achieved through charging a photostimulable phosphor plate (PSP) with an exposure to a field of X- or gamma-rays, followed by exposure to an optical image which discharges the plate in relation to the amount of incident light. According to this PSP characteristic, we developed a simple method for periodic quality assurance (QA) of light/radiation field coincidence, distance indicator, field size indicators, crosshair centering, coincidence of radiation and mechanical isocenter for linear accelerators. The geometrical accuracy of radiological units can be subjected to the same QA method. Further, the source position accuracy for an HDR remote afterloader can be checked by taking an autoradiography of the radioactive source and simultaneously an optical image of a reference geometrical system.

Effective radiation dose to the patient and to the general population from nuclear medicine procedures: variations in the last twenty-year period.

We have evaluated how changes in nuclear medicine (NM) techniques over the last twenty-year period have modified radiation exposure to the patient and population. For this purpose, we estimated the variations in the mean effective dose to the patient, and both the collective and the per capita effective dose to the population of the province of Varese, derived from radioisotope examinations carried out in the four NM Centers of this province in the years 1972, 1981, and 1991. Dosimetric calculations were based on ICRP Publication 53 for most of the radiopharmaceuticals used, and tissue weighting factors were based on ICRP Publication 60. The total number of NM exams carried out was 19,744 in 1972, 31,973 in 1981, and 23,623 in 1991. Between 1972 and 1991 there has been a substantial decrease in the effective irradiation to the patient and to the general population (mean effective dose to the patient: from 21.2 to 6 mSv; per capita mean effective dose: from 0.58 to 0.18 mSv), and in the per capita equivalent dose to some target organs, such as the thyroid (9.6-->1.5 mSv) and liver (0.51-->0.07 mSv). At the same time, there has been a significant increase in the per capita equivalent dose to the bladder (0.05-->0.48 mSv), skeleton (0.08-->0.36 mSv), and testes (0.02-->0.15 mSv), and a less marked increase to the ovaries (0.03-->0.06 mSv). The per capita equivalent dose to red marrow (0.13-->0.1 mSv) and to the large intestine (0.1-->0.12 mSv) did not change significantly.

[A method of image enhancement in the use of hydrosoluble uro-angiographic contrast media]. / Un metodo di ottimizzazione dell'immagine nell'impiego di mezzi di contrasto idrosolubili uro-angiografici.

The radiographic contrast, when using hydrosoluble uro-angiographic contrast media, depends on several factors. A phantom and a new method are proposed to assess and optimize the contrast. The phantom allows to simulate three pseudovessels with diameter of 2 mm, 5 mm, and 10 mm, placed in a water-equivalent layer of 20/cm thickness. The phantom is exposed to a photon beam produced by a conventional X ray tube, and the images are obtained using conventional screen film system. The aim of the study is to assess the radiographic contrast between the vessel and the background when modifying the optical density of the radiograph (by different settings of the mAs switching), the X-ray tube high voltage and the diameter of the vessels; the contrast was studied with four different contrast media (Uromiro 24%, Conray 36%, Iopamiro 300 and Iomeron 400) and three X-ray tube high voltages (60 kV, 80 kV, 100 kV). The curve fitting the contrast as a function of the optical density of the background (in each condition of high voltage, diameter of the vessel and contrast media used) is a parabola. A quite narrow distribution of abscissas of the maxima of the parabolas was found, ranging from the minimum optical density 1.21 in the case of 100 kV high voltage and 2 mm diameter to the maximum optical density 1.58 in the case 60 kV and 10 mm. The mean value (1.40) is proposed as the optical density of the background optimizing the contrast according to the screen-film system used. In conclusion, the authors suggest to optimize the use of contrast media, trying to obtain radiographs with an optical density approaching the optimal value in any clinical situation. Therefore tables of the settings of the X-ray tube and generator are required; the tables must take into account the main parameters influencing the settings, such as the source-film distance, the water-equivalent thickness of the patient and the film-screen system used.

[Medico-surgical evaluation of 71 reoperations in abdominal surgery]. / Bilan médico -chirurgical de 71 réinterventions de chirurgie abdominale

The authors thoroughly checked 71 reinterventions in abdominal surgery. They again found the importance of the factor of infection, respiratory, complications and oligoanuria. The overall percentage of deaths was 58 p. 100, age and associated defects made the prognosis worse.