Analytic representation of the backscatter correction factor at the exit of high energy photon beams.

In high energy X-ray beams, the dose calculated near the exit surface under electronic equilibrium conditions is generally overestimated since it is derived from measurements performed in water with large thickness of backscattering material. The resulting error depends on a number of parameters such as beam energy, field dimensions, thickness of overlying and underlying material. We have systematically measured for four different energies and for different combinations of the above parameters, the reduction of dose due to the lack of backscatter. This correction is expressed as a multiplicative factor, called "Backscatter Correction Factor" (BCF). This BCF is larger for lower energies, larger field sizes and larger depths. The BCF has been represented by an analytical expression which involves an exponential function of the backscattering thickness and linear relationships with depth, field size and beam quality index. Using this expression, the BCF can be calculated within 0.5% for any conditions in the energy range investigated.

A 3-D beam subtraction method for inhomogeneity correction in high energy X-ray radiotherapy.

Most methods of inhomogeneity correction in high energy X-ray beams, assume an infinite lateral extent of the heterogeneous volumes ("slab models") or require sophisticated time-consuming computer algorithms. We present here a method, developed for parallelepiped inhomogeneities based on a beam subtraction concept combined with a conventional "slab model". Provided that the conventional model is appropriately chosen, this method gives agreement with experimental results better than 1% in most cases. It accounts properly for the scatter modification according to the size and position of the inhomogeneous volume. One example of a computer application is also presented.

Theoretical and experimental analysis of scatter from inhomogeneous slabs in a 60Co beam: the differential tissue-air ratio method (DTAR).

A theoretical and experimental analysis of scatter from inhomogeneous slabs in a 60Co beam has been developed. This analysis has been used to examine the differential scatter-air ratio method (DSAR). It has been found that a simplification of this method gives more accurate results than the original one. Thus, a method which takes advantage of this simplification has been developed, called the 'differential tissue-air ratio method (DTAR)'. It is compared with experimental results. The accuracy is satisfactory for a wide range of applications (usually approaching the limits of the precision of the measurements, about 2%) and leads to calculation times not significantly longer than any conventional method (e.g. Batho).

A system for the management of codified medical database.

The basis, around which a health database system is structured, consists of the patient record, which has to contain all the basic information to support clinical diagnosis and therapy, as well as those which concern the programming of insurance organizations. Two new methods are introduced for the facilitating of the medical staff in data entry and transferring of information through a wide area network.

Possible disease-modifying effects of naproxen in the adjuvant-arthritic rat.

Naproxen was evaluated for possible disease modifying effects in the Freund's adjuvant injected rat (AIR). Oral administration of the clinical dose, 7 mg/kg/day, lead to an almost complete inhibition of hindpaw swelling and cartilage and bone erosion. This was noted in animals maintained on drug as well as those in which therapy was discontinued. AIR, comparable to arthritic patients, demonstrate a reduced lymphocytic response to T cell mitogens. This response was normalized in naproxen-treated rats. These results suggest that naproxen has a disease modifying effect in the AIR.