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Biomedical subjects

J Major

Publications and source records attributed to J Major.

At least 19 recordsLinked to original sources
PubMed2005

Comparison of the effects of immediate-release omeprazole powder for oral suspension and pantoprazole delayed-release tablets on nocturnal acid breakthrough in patients with symptomatic gastro-oesophageal reflux disease.

BACKGROUND: Many patients treated with a proton-pump inhibitor for gastro-oesophageal reflux disease or erosive oesophagitis still have substantial night-time gastric acidity. A previous trial of a new immediate-release omeprazole oral suspension suggested that nocturnal gastric acidity could be more effectively controlled with a bedtime dose of immediate-release omeprazole than with a delayed-release proton-pump inhibitor administered before dinner or at bedtime. AIM: To compare the ability of immediate-release omeprazole with pantoprazole to control nocturnal gastric acidity, when they were dosed once daily and twice daily. METHODS: Thirty-six patients with nocturnal gastro-oesophageal reflux disease symptoms received immediate-release omeprazole and pantoprazole in this open-label, randomized-crossover trial. Median gastric pH, the percentage of time with gastric pH > 4 and the percentage of patients with nocturnal acid breakthrough, were evaluated with 24-h pH monitoring. RESULTS: Repeated once daily (bedtime) dosing with immediate-release omeprazole suspension produced significantly better nocturnal gastric acid control than repeated once daily (predinner) or twice daily (prebreakfast and bedtime) dosing with pantoprazole delayed-release tablets (median pH: 4.7 vs. 2.0 and 1.7; percentage of time pH > 4: 55 vs. 27 and 34; nocturnal acid breakthrough: 53 vs. 78 and 75). Twice daily dosing (prebreakfast and bedtime) with immediate-release omeprazole 20 and 40 mg achieved the best night-time control of gastric acidity. Repeated once daily bedtime dosing with immediate-release omeprazole 40 mg and twice daily dosing with pantoprazole 40 mg gave similar 24-h pH control. No safety issues were associated with either drug in this trial. CONCLUSIONS: Dosed once daily at bedtime, immediate-release omeprazole reduced nocturnal gastric acidity to a degree not observed with once daily dosing of delayed-release proton-pump inhibitors.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2004

Magnetic field dependent ordering in ferrofluids at SiO2 interfaces.

We report pronounced smecticlike ordering in a ferrofluid adjacent to a SiO2 wall. In the presence of small magnetic fields perpendicular to the interface, ordered layers of magnetite nanoparticles form that can extend up to 30 layers. We also show that short ranged ordered structures emerge when the magnetic field direction is parallel to the interface; however, the layering is strongly perturbed. These results have been obtained by in situ neutron reflectometry which gives a detailed microscopic picture of these ordering phenomena. They also reveal the formation of a wetting double-layer which forms the magnetic template for the observed ordering sheets. The implications of these findings are discussed.

Journal Article↗
PubMed2002

Identification of lattice vacancies on the two sublattices of SiC.

The identification of atomic defects in solids is of pivotal interest for understanding atomistic processes and solid state properties. Here we report on the exemplary identification of vacancies on each of the two sublattices of SiC by making use of (i) electron irradiation, (ii) measurements of the positron lifetimes, (iii) coincident Doppler broadening studies of the positron-electron annihilation radiation, and (iv) a comparison of the experimental data with theoretical studies. After 0.3 MeV electron irradiation, carbon vacancies V(C) are identified, where, after 0.5 MeV electron irradiation, predomi-nantly silicon vacancies V(Si) are observed. After 2.5 MeV irradiation, divacancies V(Si)-V(Si) are detected. The present results are expected to be of general importance for reliable identification of defects and atomic processes in complex solids.

Journal Article↗
PubMed2001

Follow-up genotoxicological monitoring of nurses handling antineoplastic drugs.

Most of the antineoplastic drugs used in the treatment of tumors are carcinogenic to humans. Hospital nurses are often subject to possible occupational carcinogen exposure. Exposure may occur during handling and administration of infusion solutions containing cytostatics. A genotoxicological monitoring system to detect genotoxic changes was developed in our laboratory, helping to improve working conditions and subserving primary prevention. Multiple-endpoint follow-up genotoxicological monitoring was performed in peripheral blood lymphocytes (PBLs) among 4 groups of 95 nurses (152 investigations) occupationally exposed to cytostatics. The results were compared to those of historical and industrial controls. The genotoxicological endpoints were the determination of the frequency of sister chromatid exchanges (SCEs) and the cells with high-frequency SCEs (HFC), the frequency of structural and numerical chromosome aberrations. and the measurement of ultraviolet-light-induced unscheduled DNA-repair synthesis (UDS). In Hospital 1, where nurses worked without a safety cabinet, the percentage of cells with chromosome aberrations (AC) was significantly higher than that of the controls. In Hospital 2, where nurses used inadequate safety cabinets (with horizontal airflow), significantly elevated levels of AC, SCE, HFC, and UDS were detected. During follow-up, in Hospital 2 at the time of the second investigation AC was still significantly higher, although safety conditions had been improved. The results indicate the presence of genotoxic damage in hospital nurses working with no or inadequate safety equipment. In Hospitals 3 and 4 where nurses using biological safety cabinets, the results were lower than those in the previous two groups. In Hospital 3 in the first year of the study AC was as at the level of industrial controls. During follow-up in the course of the repeated investigations a fluctuation in AC above the control level and an increase in HFC in yr 4 and 6 of the study were observed. In this group, the fluctuation in AC and HFC during the study points to the possibility of genotoxic exposure with cytostatics despite of the use of suitable safety cabinets, drawing attention to other possible routes of exposure. In Hospital 4, both AC and HFC were elevated. These data corroborate the need to maintain safety measures to avoid exposure, and the necessity of intervention in the case of exposure when using and handling hazardous carcinogenic agents. The results also indicate a certain expression time for genotoxic changes, which can lead to late somatic mutations as well as to a possible higher risk of cancer.

Adolescent↗
PubMed2001

Working condition-related improvement in genotoxicological parameters of Hungarian road pavers.

Multiple-endpoint follow-up genotoxicology monitoring was performed in a group of 22 Hungarian road pavers between 1996 and 1999. The studied endpoints were the determination of structural and numeric chromosome aberration (CA), sister chromatid exchange (SCE), high-frequency SCE and HPRT mutation frequencies, and ultraviolet (UV)-light-induced unscheduled DNA synthesis in peripheral blood lymphocytes (PBLs). The workers (8 hand pavers and 14 finishers, mean age 37 yr) used tar-free asphalt. The results were compared with those of 6 work-site controls (35 yr), 101 historical controls (38 yr), and 87 industrial controls (38 yr). The most marked changes were found in the CA frequencies. In the control, the mean CA frequency was 1.6%. In the first study, increased CA frequencies were found in the donors that either had been exposed to hot asphalt fumes or had cleaned the equipment with crude oil. The mean CA frequency of the 14 finishers working in closed cabins was 3.67% in 1996. The increased CA frequency was attributed to the high level of hot asphalt fumes due to insufficient ventilation. By 1999 the mean CA frequency decreased to 1.23%. For the 8 hand pavers working in open air the mean CA frequency was 3.6% in 1996. The obtained data suggested that the increase in CA frequencies was due to the use of petroleum and crude oil; therefore, these substances were replaced with harmless detergents. By 1999 the mean CA frequency decreased to 1%. In finishers the mean CA frequency returned to the control level 1 yr later (1999) than in the case of hand pavers. The chromosome-type aberrations remained predominant during the follow-up. The individual variations observed were attributed to smoking and inadequate personal protection. The obtained results suggest that the use of tar-free asphalt and harmless detergents with adequate personal protection does not increase the frequencies of the genotoxicological parameters compared to controls. Consequently, an improvement in working conditions can prevent further exposures and thus decrease the cancer risk of road pavers.

Adult↗
PubMed2000

The somatostatin analogue peptide TT-232 induces apoptosis and chromosome breakage in cultured human lymphocytes.

Somatostatin receptors are supposed to be important in the regulation of apoptosis. In this study, we measured apoptosis occurring spontaneously, or induced by the synthetic somatostatin analogue, the peptide TT-232. We examined isolated human peripheral blood lymphocytes (PBL) from 32 nurses exposed bedside to cytostatic drugs, 12 chronic lymphoid leukaemia (CLL) patients prior to treatment, and 19 unexposed, healthy donors without anamnestic occupational exposure to genotoxic agents. Cells were stimulated by phytohaemagglutinin-P (PHA) and cultured for 69 h with or without 15 microg/ml TT-232, respectively. Cell kinetic parameters and apoptosis were determined by flow cytometry after staining with FITC-labeled anti-BrdU and propidium iodide (PI) and the results on spontaneous and peptide-induced apoptosis were compared with the obtained chromosome aberration frequencies (CA). The peptide TT-232 unexpectedly induced chromosome breakage in addition to apoptosis. The mean spontaneous apoptotic fractions were 6.65+/-0.89%, 6.46+/-0. 53%, and 3.07+/-0.57%, and the mean CA yields in the samples without TT-232 were 1.74+/-0.46%, 2.44+/-0.40%, and 4.50+/-1.05%, for healthy subjects, nurses, and CLL patients, respectively. A total of 15 microg/ml TT-232 treatment in healthy subjects increased the mean CA frequency (10.38+/-1.57%), as well as the apoptotic cell fraction (2.63+/-0.45 times higher than the corresponding untreated sample). In TT-232-treated PBLs of nurses, CA remained unchanged and the mean apoptotic cell fraction showed only a slight increase (1.24+/-0.11 times higher than the untreated). Among CLL patients, TT-232 treatment significantly increased both CA (up to 17.83+/-4.04%) and the ratio of apoptotic cells (21.78+/-11.00 times higher than the untreated). These results demonstrated significant differences in apoptosis sensitivity in controls, nurses and CLL donors, after 15 microg/ml TT-232 treatment. Data also indicate that the induced CA yields in CLL donors with high CA are in correlation with TT-232-induced apoptosis.

Antineoplastic Agents↗
PubMed1999

The frequency of induced premature centromere division in human populations occupationally exposed to genotoxic chemicals.

Premature (early) centromere division (PCD, i.e., the separation of centromeres during the prometaphase/metaphase of the mitotic cycle) seems to be a possible manifestation of chromosome instability in human chromosome-breakage syndromes. Chromosome instability also frequently occurs in the peripheral blood lymphocytes (PBL) of humans occupationally exposed to clastogenic agents, and is considered an etiologic factor of neoplastic diseases. In order to investigate the importance of PCD in cancer risk assessment, we studied the frequency of PCDs in PBL of 400 Hungarian subjects. The various groups comprised 188 control donors and 212 subjects occupationally exposed to different genotoxic chemicals, such as acrylonitrile (ACN) and/or dimethylformamide (DMF), benzene, cytostatic drugs, ethylene oxide (ETO), mixed exposure in the rubber industry, mixed organic solvents including CCl4, hot oil-mist, bitumen, and polychlorinated biphenyls (PCB). Data were compared with chromosomal aberration frequencies determined in the same samples. PCD yields are significantly higher in populations exposed to mixed chemicals, crude oil and cytostatic drugs, compared with controls. PCDs involving more than three chromosomes are also more frequent in ETO- and oil mist-exposed groups than in the others. The results indicate that the induction of PCDs is neither incidental nor artificial. As a consequence, we suggest that PCD can be developed into a new, exposure-related cytogenetic biomarker for a more adequate occupational cancer risk assessment. A further, follow-up epidemiological and cytogenetic investigation of PCD is in progress.

Adult↗
PubMed1999

Regulation of macrophage chemokine expression by lipopolysaccharide in vitro and in vivo.

The host response to Gram-negative LPS is characterized by an influx of inflammatory cells into host tissues, which is mediated, in part, by localized production of chemokines. The expression and function of chemokines in vivo appears to be highly selective, though the molecular mechanisms responsible are not well understood. All CXC (IFN-gamma-inducible protein (IP-10), macrophage inflammatory protein (MIP)-2, and KC) and CC (JE/monocyte chemoattractant protein (MCP)-1, MCP-5, MIP-1alpha, MIP-1beta, and RANTES) chemokine genes evaluated were sensitive to stimulation by LPS in vitro and in vivo. While IL-10 suppressed the expression of all LPS-induced chemokine genes evaluated in vitro, treatment with IFN-gamma selectively induced IP-10 and MCP-5 mRNAs, but inhibited LPS-induced MIP-2, KC, JE/MCP-1, MIP-1alpha, and MIP-1beta mRNA and/or protein. Like the response to IFN-gamma, LPS-mediated induction of IP-10 and MCP-5 was Stat1 dependent. Interestingly, only the IFN-gamma-mediated suppression of LPS-induced KC gene expression was IFN regulatory factor-2 dependent. Treatment of mice with LPS in vivo also induced high levels of chemokine mRNA in the liver and lung, with a concomitant increase in circulating protein. Hepatic expression of MIP-1alpha, MIP-1beta, RANTES, and MCP-5 mRNAs were dramatically reduced in Kupffer cell-depleted mice, while IP-10, KC, MIP-2, and MCP-1 were unaffected or enhanced. These findings indicate that selective regulation of chemokine expression in vivo may result from differential response of macrophages to pro- and antiinflammatory stimuli and to cell type-specific patterns of stimulus sensitivity. Moreover, the data suggest that individual chemokine genes are differentially regulated in response to LPS, suggesting unique roles during the sepsis cascade.

Animals↗
PubMed1999

Is breast cancer cluster influenced by environmental and occupational factors among hospital nurses in Hungary?

An unusual cluster of 8 breast cancer and 8 other malignant tumor cases (ovarian, uterus, lung, colon and brain tumors and malignant melanoma) developed in a period of 12 years among 98 nurses exposed to ethylene oxide (EtOx) for 5 15 years in a unit using gas sterilizer in a hospital of the archiepiscopal city of Eger, Hungary. EtOx concentration in air samples of the working area varied from 5 to 150 mg/m3. The question was, if there was any causal relationship between the elevated incidence of breast cancer and the EtOx exposure, the other possibility was, that this cluster appeared accidentally. EtOx is a human carcinogen, however, no increased breast cancer incidence in EtOx-exposed subjects was reported in the literature. We followed up for two consecutive years the 27 non cancer patients, EtOx-exposed nurses and 11 unexposed hospital controls with the aid of a multiple genotoxicology monitor including chromosomal aberration, sister-chromatide exchange, HPRT point mutation and DNA repair studies. The results were compared with data from 30 local historical controls, 48 historical controls from Budapest, 14 hospital controls and 9 EtOx exposed nurses from Budapest. Significantly high chromosome aberration yields (especially chromosome type exchanges) were alike detected in EtOx-exposed and the two other control groups in Eger. These results could not be interpreted as a consequence of EtOx exposure only, since in the EtOx-exposed group from Budapest, beside an increased total aberration frequency, the obtained exchange type aberration yields were as low as the historical controls. A plausible explanation can be the natural low dose radioactivity (222Rn) of the local tap-water due to a specific geological situation in Eger. The spontaneous breast cancer incidence in Hungary doubled in the last 10 years compared with the previous 20 years (1960 1980), especially in Eger. The appearance of the high breast cancer incidence in the hospital of Eger indicates the combined effect of EtOx and a more common local etiologic factor, such as the naturally radioactive tap-water. However, since the reported studies did not involve the investigation either of the genetic predisposition, or the effects of other possible environmental, occupational, and/or life style confounding factors, further studies (partly in progress) are necessary to clarify the importance of these factors.

Age Distribution↗
PubMed1998

Genotoxicological monitoring of 175 subjects living in the green belts, inner town or near chemical industrial estates in Greater Budapest agglomeration, Hungary.

We studied the effects of chronic low dose exposure to environmental pollutants on the peripheral blood lymphocytes (PBL) of subjects living in the green belts and the inner town, and/or working in the surrounding of industrial estates of Greater Budapest agglomeration, Hungary. The effects of some biological (gender, age, hematocrit and white blood cell counts), lifestyle (smoking, drinking habits and residential areas), and seasonal confounding factors were also considered. PBLs of 175 Hungarian donors of Budapest agglomeration, i.e. 45 subjects living in the green belts without significant genotoxic exposure (C1), 43 donors living in the inner town (C2), and 87 individuals living and/or working near chemical industrial estates (C3), were analysed for structural and numeric chromosome aberrations (CA), sister-chromatid exchanges (SCE), cell proliferation indices (lectine stimulation, LI; and proliferation rate index, PRI), and UV-light-induced unscheduled DNA synthesis (UDS). Each subject was interviewed personally and also investigated clinically. The three populations were matched for age, smoking and drinking habits. We excluded all donors with acute infectious and/or chronic non-infectious diseases, and/or with exposure to any known chemical hazard. For C1s, the base line CA and SCE frequencies were 0.25% and 6.41 per mitosis, respectively; in C2, these frequencies were 0.48% and 6.07 per mitosis, respectively, and in C3, these data were 1.60% and 5.71 per mitosis, respectively. A significant increase of CA due to chromosome type acentric fragments was demonstrated in the donors living in the inner town (C2), compared to those living in the green belts (C1). In C3s, significant (p < 0.05) elevations were found in the frequencies of gaps, aberrant cells, total aberrations (excluding gaps), chromatid and chromosome type aberrations, and in UDS, compared to C1s. Results indicate an increased genotoxicologic risk in donors living and/or working in industrial areas. Gender-related differences in SCE frequencies were demonstrated in C2 and C3; in the latter smoking-induced changes in UDS were also found. Light drinking did not appear to influence the results.

Adult↗
PubMed1998

Follow-up biological and genotoxicological monitoring of acrylonitrile- and dimethylformamide-exposed viscose rayon plant workers.

In order to investigate the genotoxic effects of occupational acrylonitrile (ACN) and dimethylformamide (DMF) exposures, clinical serum and urine parameters and genotoxicological endpoints such as chromosome aberration (CA), sister chromatid exchange (SCE), high frequency SCE (HFC), cell cycle kinetics, and UV-induced unscheduled DNA synthesis (UDS) were followed up three times during a 20-month period in peripheral blood lymphocytes (PBL) of 26 workers (13 maintainers and 13 fiber producers) occupationally exposed to ANC and/or DMF in a viscose rayon plant, 26 matched control subjects, and six industrial controls (all males). Six of the 26 exposed subjects were hospitalized because of liver dysfunction that had developed due to inhalative DMF exposure. The rate of smoking was estimated on the basis of serum thiocyanate (SCN) levels. Average peak air ACN and DMF concentrations were over the maximum concentration limits at the time of both investigations. Urine ACN and monomethyl-formamide (MMF) excretions of the exposed subjects were almost doubled after work shifts. An increase in lymphocyte count (in months 0 and 7), and severe alterations in the liver function were observed in the exposed subjects. In PBLs the proliferative rate index (PRI) was already increased in month 0 compared with the controls. In each study, significant increases in CA and SCE frequencies, as well as increases in UDS were found in PBLs of the exposed subjects. The frequencies of chromatid breaks and acentric fragments further increased in month 7 and remained constantly elevated in month 20. Increased yields of both chromatid and chromosome-type exchange aberrations first appeared in month 20, when HFCs were 2.72 times more frequent in fiber producers than in maintainers. The role of some important biological confounding factors (age, white blood cell count, and hematocrit) and lifestyle confounding factors (smoking and drinking habits) were subjected to an analysis of variance during the second study. Increased CA, SCE, and UDS were found both in control and exposed smokers when current smoking was established on the basis of the serum SCN levels. The cytogenetic data suggest that occupational exposures to ACN and DMF induce considerable genotoxic consequences and may increase the cancer risk in the exposed human populations.

Acrylonitrile↗
PubMed1996

Genotoxicological investigation of hospital nurses occupationally exposed to ethylene-oxide: I. Chromosome aberrations, sister-chromatid exchanges, cell cycle kinetics, and UV-induced DNA synthesis in peripheral blood lymphocytes.

Structural, and numeric chromosome aberrations (CA), sister-chromatid exchange (SCE), phytohemagglutinin stimulation (LI), proliferative rate index (PRI), and UV light-induced unscheduled DNA-synthesis (UDS) were investigated in peripheral blood lymphocytes (PBL) of 48 historical controls ("Controls"); of 14 hospital controls in Budapest, Hungary ("Budapest controls"); of 9 nurses occupationally exposed to low-dose ethylene-oxide in Budapest ("Budapest exposed"); of 10 hospital controls in Eger, Hungary ("Eger controls"); and of 27 high dose ETO-exposed nurses in Eger ("Eger exposed"), where neoplasias, mainly breast cancers, were observed. ETO concentrations in the ambient air samples varied from 5 to 20 mg/m3 in Budapest; and from 5 to 100 mg/m3 in Eger. Bothe LI and PRI were depressed in Budapest exposed, indicating ETO-induced cytotoxicity and, however, normal in Eger exposed. SCE was slightly elevated in Budapest exposed, but significantly increased in Eger exposed. The yields of cells with high frequency SCE (HFC) were only increased in Eger exposed. The expected low CA frequencies were found in Controls and in Budapest controls. ETO exposures significantly increased the CA frequencies in Budapest and Eger exposed. In Budapest exposed, as expected, we found deletions; in a lesser extent chromatid exchanges and dicentrics; but no rings were detected. These results are in a good accordance to the published data of other investigations carried out on ETO-exposed human populations. However, in Eger exposed, beside the increased yields of deletions, the frequencies of dicentrics and rings showed a significant excess compared to the reviewed data. An unexpected, significant increase of dicentric and ring frequencies was also detected among the hospital controls in Eger controls without known clastogenic exposure. The role of confounding factors (age, smoking and drinking habit, total leukocyte count and hematocrit) was investigated by an analysis of variance on CA and SCE frequencies in Controls and in Eger exposed. Leukocyte count and mean age showed only significant effects on CA in Eger exposed and on SCE in Controls, respectively. A possible active confounding factor could be the temporary natural radioactivity of the local tap water. UDS in Budapest exposed and in Eger control were significantly higher then in the Controls and in Budapest controls. In Eger exposed UDS was significantly decreased compared to the Budapest exposed and Eger control groups. The explanation of the present results is difficult on the basis of the reviewed data on ETO-induced CA frequencies in exposed human populations, and it raises an issue of an independent genotoxic effect in Eger, which is common both in Eger controls and in Eger exposed, such as natural radioactivity.

Adult↗
PubMed1996

Treatment planning for bicentric stereotactic irradiation.

We have investigated a bicentric stereotactic convergent beam irradiation technique for the treatment of irregularly shaped, especially elongated, target volumes. Depending on the size and shape of the target volume optimum values for the isocenter distance, collimator apertures and dose inhomogeneity have been determined which serve as starting parameters for the interactive optimization of dose distribution. The treatment planning system of the stereotactic unit SRS-200 (Philips) has been used to calculate the parameter tables. However, the presented results are also applicable to other stereotactic systems.

Film Dosimetry↗
PubMed1996

[Stereotaxic convergent-beam irradiation. Initial experiences with the SRS 200 system].

BACKGROUND: The system SRS 200 for the stereotactic convergent beam irradiation described in this paper has a stereotactic floor stand, which allows the high precision rotation of a secondary collimator around an isocenter. This system is used since 1991 at the University Hospital of Tübingen for the treatment of patients with solitary brain metastases, acoustic neurinomas and arteriovenous malformations. PATIENTS AND METHODS: The attainable accuracy of the mechanics and dosimetry was studied within the scope of extensive quality assurance measures during its installation and before each patients' irradiation. The individual treatment steps from radiotherapy planning to irradiation were evaluated by means of a specially developed head phantom. Since the installation of the SRS 200 a total of 50 patients (21 solitary brain metastases, 12 acoustic neurinomas, 17 arteriovenous malformations) has been treated with the system. RESULTS: With 0.3 mm +/- 0.2 mm an excellent accuracy of the target point transfer and isocenter stability during irradiation was attained. The difference between calculated dose and dosimetric control measurements was smaller than 3%. The physical accuracy, however, is limited by the imaging resolution (CT and digital subtraction angiography). Of the patients 15% with solitary brain metastases developed complete remission, 20% partial remission and with 50% no further neurological deterioration was observed. Imaging revealed for 88% of the patients a reduced uptake of contrast medium or a regression of the tumor size. Six patients with acoustic neurinoma had anacusis already before radiotherapy. Regarding the other patients in the follow-up, hearing improved in 1 patient, 1 patient showed hearing deterioration, and all other patients hearing remained constant. MR and CT imaging revealed in 10 patients with acoustic neurinoma a reduced uptake of contrast medium and in 1 patient a tumor diminution. From the patients with arteriovenous malformation only 4 have been followed for more than 2 years after treatment. Therefore, statements about the rate of obliteration are not possible yet. Concerning pretherapeutic symptoms (headache 22%, convulsion 28%, neurological deficits 11%) 8/17 (47%) of the arteriovenous malformation patients showed an improvement, in 8 patients clinical findings were unchanged and 1 patient showed neurological deterioration. CONCLUSION: The stereotactic system SRS 200 allows an excellent mechanical accuracy in the radiosurgery with linear accelerators.

Adolescent↗
PubMed1995

Stereotactic convergent beam radiosurgery versus stereotactic conformation beam radiotherapy.

By means of preliminary results in the treatment of patients with acoustic neurinoma the achievable accuracies, dose distributions and time consumption of stereotactic LINAC-based convergent beam radiosurgery are compared to those achieved with fractionated stereotactic conformation beam radiotherapy. Characteristics of both techniques are described. With the Tübingen radiosurgery system a good adaptation of the dose distribution to spherical or oval target volumes with a steep dose gradient was achieved, whereas homogeneity and adaptation of the dose distribution to irregularly shaped targets were better with the Heidelberg conformation technique. The mechanical accuracy of the Tübingen floorstand system was 0.3 mm +/- 0.2 mm, and that of the Heidelberg mask fixation system < 1 mm. Both methods require similar total treatment times. Nine patients were treated by the Tübingen radiosurgery system. The results are compared with 12 patients treated by conformation radiotherapy in Heidelberg. In both patient groups no further tumour growth occurred. Four of 9 single dose treated patients developed side-effects, such as temporary trigeminal and facial paraesthesia hearing deterioration and oedema. In contrast, patients treated by fractionated radiotherapy showed no side-effects. Relating to the short follow-up the results indicate that single dose application has certain drawbacks for special indications. Further studies have to work out which method gives the best treatment results.

Adolescent↗
PubMed1995

Does the photon beam quality factor depend on the type of ionization chamber?

The photon beam quality factor Q of 6- and 15-MV photon beams has been measured using different types of thimble ionization chambers with various wall, electrode and insulator materials. Some types of chambers seem to overestimate the corresponding Q-value by 0.4% (6 MV) and 0.7% (15 MV), respectively. The effect on the stopping power ratio water to air and on the pertubation correction will be discussed.

Photons↗