Tissue compensation using dynamic collimation on a linear accelerator.

PURPOSE: The availability of computer-controlled collimators on some accelerators has led to techniques for dynamic beam modification, mainly to simulate beam wedge filters. This work addresses the practical aspects of dynamic tissue compensation in one dimension using available treatment-planning software. METHODS AND MATERIALS: Data derived from the treatment-planning program is used with an iterative calculational routine to determine the monitor unit settings needed for the collimator-controlling computer. The method was first tested by simulating a 60 degrees physical wedge. Further studies were carried out on a specially fabricated plastic phantom that modeled the sagittal contour of the upper torso, neck, and lower head regions. RESULTS: Dynamic wedge point doses generated by the planning program agreed within 1% with the values directly measured in a polystyrene phantom. In the patient phantom, dynamic collimation achieved calculated dose uniformity within 0.5% in a reference plane near the phantom midline. A comparison of computer-generated and measured point doses in this case showed agreement within 3%. CONCLUSIONS: Dynamic collimation can provide effective compensation for contours that vary primarily along one direction. A conventional treatment-planning program can be used to plan dynamic collimation and deliver a prescribed dose with reliable accuracy.

[Acute basophilic leukemia in a 75-year-old man. A clinical and cytological study with a review of the literature]. / Ostra bazofilna levkoza u 75-godishen muzh. Klinichno i tsitologichno prouchvane s pregled na literaturata.

The authors present a rare clinical case of cytomorphologically and cytochemically confirmed acute basophil leukosis ( ABL ) in a male, aged 75. A comprehensive review of the present-day literature on the problem is made with detailed discussions of the differential diagnostic criteria upon which the diagnosis is made. The discussion emphasized some aspects of the cytomorphological characteristic, not finally solved, and on the nozological belonging of ABL .

Experiments on the preparations and testing of associated vaccine against foot and mouth disease and vesicular disease in swine.

Tests for associated immunization of swine against Foot and Mouth Disease (FMD) and Vesicular Disease (SVD) of swine were carried out. As a result of this investigation, it was established that the prepared and tested inactivated oil vaccine is harmless and immunogenic in sensitive animals. In investigating the course of immunity, the presence of antibody against both antigens was demonstrated in vaccinated animals. All once-vaccinated animals were defended against the virus of SVD during challenge, and 75% of them were defended against FMD. After revaccination, all immunized swine were defended against infection with both viruses. The question of the quality of the associated vaccine and the possibilities of its massive use in industrial swine rearing was discussed.

[Use of indirect complement fixation test for studying foot and mouth disease virus]. / Izpolzvano na indirektnata reaktsiia za svurzvane na komplementa pri prouchvane na shapnite virusi

The indirect complement-fixation test was used in experiments for the subtype differentiation, and with the agar gel diffusion and the serum neutralization test was studied the immunity in cattle that had already recovered from foot-and-mouth disease or were immunized against the disease. It was found that the indirect complement-fixation test is instrumental in the demonstration of the antigenic differences between the foot-and-mouth viruses. Comparative experiments have shown that the indirect test in this case is more expedient and of higher economic value than the direct CF reactions after Traub and Möhlmann and after Marucci. The assessment of the results of comparative investigations of sera carried out by the indirect complement-fixation test, the agar gel diffusion test, and the serum neutralization reaction revealed that the indirect reaction is a convenient, quick, and prompt method of work. Discussed is the sensitivity of the reaction and its advantages and its advantages in studies on a large scale on the immune status of animals immunized against F.M.D. or animals that have recovered from the disease.

[Attempts to adapt BNK cells to cultivation in suspension and study of the antigenic properties of foot-and-mouth diseases viruses obtained from them]. / Opiti za adaptirane na BNK kletki kum suspenzionno kultivirane i prouchvane antigennite kachestva na dobitite ot tiakh shapni virusi

Experiments were carried out to cultivate the foot-and-mouth disease virus under laboratory conditions in a suspension of the BHK-21 cell line. Results showed that the number of cells cultivated in a susfor 48 to 72 hours of incubation reaches up to 2.2 X 10(6). It was also found that certain conditions should be observed for the successful cultivation of the cells in suspension, such as aeration, pH, and respective temperature. It was demonstrated that foot-and-mouth diseases viruses obtained from BHK cells propagating in suspension possess good antigenic and immunogenic properties.

[Study of foot-and-mouth disease virus inhibitors in cell cultures and experimental animals]. / Prouchvane na niakoi inkhibitori na shapniia virus v kletuchni kulturi i opitni zhivotni

Studied was the inhibiting action of some synthetic agents conditionally denoted No. 3 (benzamidazol), No. 76, and No. 78 (imidazolins) on the reproduction of the foot-and-mouth disease virus in cell cultures, newborn mice and guinea pigs. It was irrefutably demonstrated that all three agents produce an inhibiting effect on the virus. This effect was enhanced by the combined use of these inhibitors. It was found that best effect on the virus' replication produced the combination of agent No. 3 and some of the other two inhibitors. Discussed is the mechanism of action of these compounds.

[Study of the immunity in swine vaccinated with type C anti-foot-and-mouth disease vaccine]. / Prouchvane na imuniteta u svine, vaksinirani s protivoshapna vaksina tip C

Experiments were carried out to adapt a cell culture strain of the foot-and-mouth disease virus, type C, to the organism of susceptible pigs. It was established that 4 to 5 passages are needed to adapt the virus, all treated animals showing the symptoms of the disease from the 24 hour following infection which assumed a generalized course. In determining the index of protection (P) of a given F.M.D. vaccine through challenging immunized pigs its value proves to be 4.5. It is stressed that this is a suitable and economic method to evaluate the immunogenic properties of F.M.D. vaccines for pigs.

[Comparative study of immunity in swine vaccinated with foot-and-mouth disease vaccines prepared with various adjuvants]. / Sravnitelni prouchvaniia na imuniteta pri svine, vaksinirani s protivoshapni vaksini, prigotveni s razlichni adzhuvanti

The vaccines used were prepared with saponin, an oil adjuvant and a DEAE-dextran adjuvant. Comparative studies revealed that vaccines containing DEAE-dextran at the rate of 50 mg pro dosi confer weaker immunity as compared with vaccines containing saponin or an oil adjuvant. Pointed out is the lack of correlation between the antibody level in the vaccinated animals and the effectiveness of the immunity conferred, which was established through challenge. Discussed is the quality of the DEAE-dextran containing vaccine in comparison with the other two F. M. D. vaccines. The practical use of the oil containing vaccine is also discussed. Studies revealed that it confers the best immunity in the vaccinated pigs.

[Study of the indirect complement fixation test for use in the differentiation of foot-and-mouth disease viruses and the determination of immunity]. / Prouchvaniia na nepriakata RSK s ogled diferentsiraneto na shapnite virusi i opredelianeto na imuniteta

Studies were carried out to establish the optimal conditions for the indirect complement-fixation test (ICFT) and explore the possibility to use the test in differentiating the foot-and-mouth disease (FMD) viruses and checking the immunity obtained in survivals or in animals that had been vaccinated against FMD. It was demonstrated that the proper use of ICFT necessitates in turn the use of a minimal amount of antigen, which in the presence of 1-2 E homologous hyperimmune serum completely binds the 1 E complement. Results showed that the sera of survived or vaccinated animals contain specific antibodies of titers of 1:4 up to 1:256. The latter depended on the type of vaccine, the amount of antigen in the vaccinal dose, and the time period from the immunization or survival up to the time of taking the serum samples. It is pointed out that ICFT is a sensitive and specific method for the differentiation of FMD viruses and the study of animals' immunity against FMD.

[Passive immunity in calves born of cows that have recovered from foot-and-mouth disease or been vaccinated against it]. / Prouchvane na pasivniia imunitet pri teleta, proizkhozhdashti ot preboleduvali i ot vaksinirani sreshtu shap kravi

It has been found that the antibody titers in the case of passive immunity in calves from cows that have recovered from foot-and-mouth disease or have been vaccinated against it rise immediately following the intake of colostrum. They have been found to reach a peak level, displaying maximal values for a long period of time. Later on the antibody titers decline gradually. Specific antibodies have also been demonstrated at the age of more than two months following birth. Higher values of passive immunity have been established in calves from survivals and from cows that have been vaccinated twice and this is explained by the presence of a higher content of foot-and-mouth disease antibodies in the dams. The importance of passive immunity for the prevention of the disease in growing animals is discussed.

[Comparative testing of methods for the control of foot-and-mouth disease vaccines on guinea pigs]. / Sravnitelno izpitvane metodite za kontrol na protivoshapnite vaksini v'rkhu morski svincheta

It was found that the so-called direct methods for the control of vaccines give better idea about the immunogenic properties of the F. M. D. vaccines. The direct method for the determination of the value for guinea pigs is to be preferred to the method determining the protection index C, and is convenient, fast and readily applicable in terms of economy and preciseness. Discussed is the problem of employing the method in the research and production activities under laboratory conditions.