PubMed Health⌕ Search

Biomedical subjects

B Zackrisson

Publications and source records attributed to B Zackrisson.

28 records · Page 2Linked to original sources
PubMed1994

Acute effects of accelerated radiotherapy in combination with carbogen breathing and nicotinamide (ARCON).

Combining accelerated radiotherapy with carbogen and nicotinamide (NAM) has been proposed as a strategy to overcome the sparing effect of tumour clonogen repopulation and hypoxia. Six patients with squamous cell carcinomas of the head and neck were given accelerated radiotherapy, carbogen breathing and high dose nicotinamide in order to evaluate the feasibility of this treatment regimen. The patients received radiotherapy in two daily fractions of 1.8-1.9 Gy, five days/week, total dose 54-57.6 Gy, in an overall treatment time of 19-22 days. The interfraction intervals were 7-8 hours between the two fractions on the same day. Carbogen breathing was started 5 minutes before and went on during each radiation fraction. a variety of NAM doses were administered orally in conjunction with radiation therapy and analyses of plasma concentrations of NAM and its metabolites were performed. The most common side-effect from NAM was nausea and vomiting, which in one case hampered further NAM administration. The side effects were not related to plasma levels of NAM or its main metabolites. Additionally, one patient with preexisting heart disease developed a severe hypotension and renal dysfunction. All acute reactions healed without further complications. The mucosal reactions were generally brisk. Thus, the combination of accelerated radiotherapy with carbogen and NAM seems to be tolerable.

Administration, Inhalation↗
PubMed1994

Tolerance to accelerated fractionation in the head and neck region.

To improve efficacy of radiotherapy in head and neck carcinomas, shortening the treatment time by accelerated fractionation is one possible method. However, there is a risk of enhancing side-effects. To study the tolerance to accelerated fractionation a study was thus performed where 2.0 Gy/fraction was given twice daily with 7-8 h interval between fractions. The total dose was 60 Gy and the overall treatment time 19-22 days. Thirteen patients with tumours in the head and neck region were consecutively included in the study. The treatment volumes ranged from encompassing the primary tumour with a margin to including the oral cavity and neck nodes bilaterally. Evaluation has been done by means of scoring the mucosal reactions, subjective estimation of pain, and functional impairment. Furthermore, the late radiation effects have been assessed by scoring of telangectasia, fibrosis of subcutaneous tissues and necrosis. The median follow-up time was 37 months. The treatment was generally well tolerated and could be completed without interruptions. However, in most cases the acute mucosal reactions appeared to be severe for a longer time than after standard fractionation. Restitution of normal mucosa without persistent complications has been achieved in all cases. The toxicity of this treatment schedule seems to be acceptable. No severe late complications have occurred during the follow-up period. A comparison with other treatment schedules has been made, using the linear-quadratic (LQ) model to calculate biologically effective dose (BED). In the present schedule it is shown that the early reacting normal tissue and tumour effects are predicted to be similar to the EORTC schedule whereas the late effects would be less pronounced. The CHART protocol gives less effects on early responding tissues due to the low total dose.

Acute Disease↗
PubMed1993

Matching of electron and photon beams with a multi-leaf collimator.

Multi-leaf collimators (MLCs) are offered as an accessory to many accelerators for radiation therapy. However, beam edges generated with these collimators are not as smooth as can be achieved with individually made blocks. The clinical drawbacks and benefits of this ripple were evaluated both for single field treatments and for combined adjacent fields of different beam qualities. In this investigation the MLC-collimated beams of the MM50 racetrack microtron were studied. The distance between the field edge and the 90% isodose was measured at the reference depth for four beam qualities (20 MV photons and 10, 20 and 50 MeV electrons). This distance was found to vary from approximately 6 mm for straight beam edges (i.e., all collimator leaves aligned) to approximately 2 mm from the tip of the leaves for a saw-tooth shaped beam edge. The over- and under-dosage in the joint between combined adjacent fields was found to be typically +/- 10% in small volumes. Improved clinical techniques using adjacent photon and electron fields with the same isocentre and source position (without moving the gantry) have been developed. For treatments of the breast, including the mammary chain, a uniform dose distribution was created with special attention given to the irradiation of the heart and lung outside the target volume. A method for head and neck treatments was optimised to give uniform dose distribution in the joint between the photon and electron fields and a method of treating the mediastinum, including the chest wall in front of the left lung, was analysed with respect to dose uniformity in the tumour and shielding of the lung.

Breast↗
PubMed1992

The effect of ondansetron on radiation-induced emesis and diarrhoea.

Fractionated radiotherapy of malignancies in the abdomen induces nausea and vomiting in approximately 50% of the patients. During abdominal irradiation the damaged gastrointestinal mucosa releases 5-HT with ensuing activation of 5-HT3 receptors which may explain the nausea and vomiting. Ondansetron is a new 5-HT3-antagonist with antiemetic properties. In this consecutive study, 33 patients receiving fractionated upper abdominal irradiation (> or = 100 cm2, 1,8-4 Gy daily dose for a mean of 13 days) were treated with ondansetron (8 mg t.d.s. p.o.). Emesis was completely controlled in 26/33 (79%) patients throughout their radiation course, which embraced 628 (94%) treatment days. Ondansetron was well tolerated. Eleven patients developed mild constipation. No patients experienced diarrhoea (a common distressing side-effect of abdominal irradiation). It is suggested that ondansetron can be of value in preventing emesis in patients receiving fractionated radiotherapy. The possible beneficial effect in preventing diarrhoea must be further evaluated.

Abdominal Neoplasms↗
PubMed1992

Radiobiological cell survival models. A methodological overview.

A central issue in clinical radiobiological research is the prediction of responses to different radiation qualities. The choice of cell survival and dose-response model greatly influences the results. In this context the relationship between theory and model is emphasized. Generally, the interpretations of experimental data depend on the model. Cell survival models are systematized with respect to their relations to radiobiological theories of cell kill. The growing knowledge of biological, physical, and chemical mechanisms is reflected in the formulation of new models. The present overview shows that recent modelling has been more oriented towards the stochastic fluctuations connected to radiation energy deposition. This implies that the traditional cell survival models ought to be complemented by models of stochastic energy deposition processes and repair processes at the intracellular level.

Cell Survival↗
PubMed1992

Relative biological effectiveness of 50-MV X rays on jejunal crypt survival in vivo.

Earlier in vitro studies of relative biological effectiveness (RBE) of 50-MV X rays show an RBE of approximately 1.1 compared to 4 MV. No difference in RBE has been found for 20-MV X rays or 50-MeV electrons. The higher RBE for 50 MV can be explained to some extent by the small high linear energy transfer contribution from photonuclear reactions at high X-ray energies. To investigate the validity of the results in vitro, a study of the RBE of 50-MV X rays has been performed in vivo using the jejunal crypt microcolony assay in mice. The reference radiation used in this case was 20-MV X rays. The results confirm the earlier in vitro studies. The RBE for 50-MV X rays was estimated to be 1.06, calculated as the ratio between the slopes of the response curves.

Animals↗
PubMed1991

Relative biological effectiveness of high-energy photons (up to 50 MV) and electrons (50 MeV).

In vitro studies of the relative biological effectiveness (RBE) of 50-MV X rays have shown an RBE of 1.1 relative to 4-MV X rays. This will be important in clinical radiotherapy. The aim of this study was to verify these results and to investigate whether photonuclear processes might cause the difference in RBE. To do so, 50- and 20-MV X rays and 50-MeV electrons were investigated with respect to RBE. Chinese hamster V79 cells were irradiated in a specially designed system which allows for a high reproducibility of geometry and dosimetry. Fractionation experiments were also carried out to establish the RBE at the clinically relevant dose level, 2 Gy. Fricke dosimetry was used, and the results were confirmed with ionization chamber measurements. The RBE for 50-MV X rays was estimated to be 1.14 at a surviving fraction of 0.1 and 1.12 at a surviving fraction of 0.01. The RBEs for the other qualities were equal to one. The RBE calculated for the 2 Gy/fraction experiments was 1.17.

Animals↗
PubMed1989

Relative biological effectiveness and oxygen enhancement ratio of 50 MV X-rays.

Experiments in vitro, using V-79 Chinese hamster fibroblasts, were carried out in order to establish whether or not there was a difference between the relative biological efficiency (RBE) and/or the oxygen enhancement ratio (OER) of 50 and 4 MV bremsstrahlung photons. Dosimetry was performed with both Fricke dosimetry and ionization chamber. Cells were irradiated in all glass-metal system under both oxic and anoxic conditions and subsequently plated for cloning assay. Dose corrections were made for the backscatter from the glass to which the cells were attached during irradiation. A statistically significant difference between RBE of the two energies was found. The RBE was estimated to be 1.1 for 50 MV photons. No difference in OER was found. This RBE difference is of clinical interest as it is generally accepted that it should be possible to determine the dose level with a precision of about +/- 5% in radiation treatment.

Animals↗
PubMedDate not supplied

Cell kinetic analysis of non-Hodgkin's lymphomas using in vivo iododeoxyuridine incorporation and flow cytometry.

The aim of this study was to analyse dynamic cell proliferation parameters in non-Hodgkin's lymphomas. Sixty-one patients with newly diagnosed or with recurrent disease were given iododeoxyuridine (IdUrd) intravenously near 4 h prior to tumour biopsy. After staining with an IdUrd reactive antibody and propidium iodide, S-phase fraction (SPF), labelling index (LI), S-phase duration time (Ts) and potential tumour doubling time (Tpot) were determined by flow cytometry. Thirty-eight samples, 15 low grade (LGM) and 23 high grade (HGM) malignant lymphomas, were possible to evaluate. Twenty-three cases were excluded due to aneuploidy, insufficient amount of material or technical problems. Tpot values varied between 0.8-32.9 days (mean 7.0 days). HGM lymphomas had shorter mean Tpot times than LGM lymphomas (4.8 versus 10.4 days, p = 0.05). For Ts the range was 4.2-20.1 h (mean 9.1 h), and a difference between the two histological groups was demonstrated with a longer mean Ts for HGM compared with LGM cases (10.0 versus 7.8 h, p = 0.04). Tpot showed a negative correlation with SPF (P = 0.003), and Ts demonstrated a positive correlation to SPF (p = 0.02). The clinical significance of the dynamic cell proliferation parameters studied remains to be clarified, but the interrelationships between Ts/SPF and Ts/morphologic subtype might be factors of interest for future prognostic studies in malignant lymphomas.

Cell Cycle↗