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At least 919 records · Page 51Linked to original sources
PubMed1990

Repair inhibition in tumours irradiated with fast protons and negative pions.

Solid Ehrlich mouse tumours were irradiated in the 80 MeV proton beam of the Paul-Scherrer-Institute. The tumour volume was measured as a function of time after irradiation and two experimental endpoints were determined: local tumour control and minimal tumour volume after irradiation. The application of 2-deoxy-D-glucose (2-DG; 2 mg/kg) increased the radiation effect of protons by a factor of 1.4. The same tumour system was used with negative pions. Human tumours are usually irradiated with a mixed radiation produced by the "spot-scan-technique". This radiation quality was simulated in the mouse experiment by two successive irradiations with a spot of densely ionizing peak pions and a spot of sparsely ionizing plateau pions. Application of 2-DG raised the radiation effect due to the sparsely ionizing component again by a factor of 1.4. This indicates that clinical results in radiotherapy might be improved by application of 2-DG during the treatment.

Animals↗
PubMed1990

Pion irradiation at Paul Scherrer Institute. Results of dynamic treatment of unresectable soft tissue sarcoma.

Since November 1981, when pion irradiation was introduced for deep seated tumors at the Swiss Institute for Nuclear Research (SIN; now Paul Scherrer Institute, PSI) a dynamic, three-dimensional spot scan application technique has been in use. To exploit this technique a special planning system for optimisation of the dose distribution has been designed. From November 1981 to December 1988 a total of 406 patients have been treated with pions. From April 1983 to October 1987 a total of 35 patients were prospectively treated for unresectable soft tissue sarcomas in a phase I/II-study. In 32/35 patients, tumor sites were retroperitoneal, pelvic or in the groin or thigh. 27 patients received a high, curative total dose of 30 to 36 Gy. After a median follow-up time of 19 months (13 to 68) the actuarial five-year rate of local tumor control for these 27 patients was 64%; the actuarial five-year survival rate of the 20 patients treated without metastases was 58%. Late reactions appeared in 5/27 patients: 2/8 patients with extremity/groin sarcomas (1/2 caused by biopsy) and 3/19 patients with retroperitoneal/pelvic sarcomas (one a skin reaction after Actinomycin-D, one a small bowel reaction after 36 Gy, a dose no longer given). Dynamic spot scan pion irradiation proves to be a successful treatment technique for unresectable sarcomas with a high rate of tumor control and a very low rate of severe late reactions.

Aged↗
PubMedDate not supplied

The asymmetry of biological molecules and the symmetry CPT.

Due to the interference of weak nuclear and electromagnetic forces, a specific relationship exists between the electric polarization of the covalent bonds and the spatial orientation of certain atoms and chemical groups in the framework of matter. The symmetric in the mirror corresponding to this relationship is in antimatter (symmetry CP). In this transformation, time preserves its direction of development (symmetry CPT).

Chemical Phenomena↗
PubMed1988

[Pion radiation therapy of non-resectable bone- and soft tissue sarcomas at the Swiss Institute for Nuclear Research].

A dynamic, tumor conforming treatment technique ("spot scan") for deep-seated tumors using pions (negative pi-mesons) has been in use at the Swiss Institute for Nuclear Research (SIN) since November 1981. This technique, with a favorable integral dose distribution, allows curative irradiation especially for large, unresectable tumors in the retroperitoneal and pelvic region. Between 1983 and 1986, 26 patients with sarcomas were treated: 18 had soft tissue sarcomas and 8 bone sarcomas. The tumor volumes ranged from 36 to 3400 cc. After previous therapy (23/26 patients) 14 out of 23 patients had progressive disease. In 20 fractions over 5 weeks a total dose of 30-36 Gy (90%-isodose) was administered. In a follow-up period of 9-50 months (median 14 months), the two year local control rate (Kaplan-Meier) for the soft tissue sarcomas was 93.3% and the two year survival rate 67.9%. Each of the 6 patients with bone sarcomas treated with curative intent showed clinically local tumor control. After a total dose of 30-36 Gy, no severe radiation induced morbidity was found.

Adolescent↗
PubMed1989

Effect of different stopping volumes of clinical pion beams at TRIUMF on the mouse small intestine.

The survival of mouse jejunal crypt cells was measured using a microcolony assay following irradiation with one of three different pion stopping volumes. All treatments were done using the beam spot scanning system developed for clinical therapy at TRIUMF. Treatment volumes were Small, 10 ml of volume using 4 beam spots with a narrow stopping peak; Moderate, 40 ml of volume using 4 beam spots with an extended peak; Large, 1.2 liters of volume using 37 spots with an extended peak. The dose rate fluctuated considerably during treatment because of the scanning procedure. The relative biological effectiveness (RBE) values of pions were 1.11, 1.04, and 1.16 for the small, moderate, and large volumes, respectively. As the width of the stopping peak increased, from the narrow 4-cm peak of the small volume to the 12-cm peak of the moderate volume, the effectiveness of the pion beam decreased. This presumably reflects the low linear energy transfer contribution of the large number of passing pions in the wider stopping peak. The results indicate, however, a greater biological effectiveness for the large volume than for the moderate volume. Even though these fields had stopping peaks of similar width, the field size and dose rate were different. Although the increase in RBE may be partly due to an increased neutron flux from the larger volume, our results suggest that much of this apparent increase could be explained by differences in dose rate as a function of time for pions versus X rays.

Animals↗
PubMed1989

Superstring theory.

Explore the source record for details and available documents.

Elementary Particles↗
PubMed1989

Biological effectiveness of neutrons and pi-mesons in gut, bone, and transplantable tumours.

At the Munich RENT-facility a screening project was performed to define the biological characteristics of a fission neutron beam envisaged for radiotherapy. The quantitative endpoints used were jejunal crypt survival, late rectal stenosis in rats, osseous healing in traumatized rat femur and regrowth delay of murine transplantable tumours. The results obtained in normal tissues (with the possible exception of bone) demonstrate a high RBE, in accordance with the well documented dependence of RBE on neutron energy. The RBE-values measured in tumours after single dose treatment endorsed the high effectiveness, although--as has been the case with other beams--they gave no conclusive evidence of a therapeutic advantage. Nevertheless, the specific beam characteristics, i.e. a high RBE at the surface and a fast decline of the biologically effective depth dose suggest possible advantages of the RENT beam when applied in the treatment of selected superficial tumours.

Animals↗
PubMed1989

Tolerance of spinal cord, lung and rectum after fractionated pions and X-rays.

The chronic and late effects of fractionated negative pi-mesons (pions) and X-rays were investigated in rat spinal cord and rectum, and in mouse lung. Range modulated pions with a 6 cm Bragg peak were used at an average dose-rate of 0.2 Gy/min. Control studies were performed with 250 kV or 300 kV X-rays. The following functional and histological endpoints were used: paralysis and white matter necrosis after spinal cord irradiation, ulceration and fibrosis of the rectum, breathing frequency and pneumonitis after lung irradiation. The presence of a large low-LET component was reflected by a significant dose-rate effect for spinal cord and lung. This resulted in RBE values smaller than unity for single doses, since the reference X-irradiations were done at high dose-rate. For small fraction sizes and short exposure times the influence of the dose-rate is insignificant. The RBE values at pion doses of 1 to 2 Gy per fraction were found to be not higher than 1.5 for all tissues studied. These values are similar compared to published data for acute effects. This is in contrast to the effects of neutrons, which in general show higher RBE's for late effects. It can be concluded from our studies that the radiobiological characteristic of pions in a spread Bragg peak are influenced by the low-LET component of the beam. Unlike with neutrons, there are no significant differences between the RBE values for late and acute effects.

Animals↗
PubMed1985

Preparatory clinical studies of Pi-mesons at TRIUMF.

Eighty patients have been treated with Pi-mesons (pions) at TRIUMF between 1979-1984. The patients had tumors rarely curable by standard methods and had no prior radiotherapy. The distribution by site included skin, metastatic nodules (13), brain, glioblastoma multiforme (32), pelvis, rectosigmoid (15), prostate (12), bladder (7), and ovary (1). The studies involve serial escalations of pion dose until maximum tissue tolerance is reached, monitoring the response at each dose increment. Sites were chosen for study where lack of local control is a significant cause of treatment failure with conventional radiation therapy. The low dose rate and the available beam access at TRIUMF limit the number of patients treated and the volume treatable. A 3-D treatment planning program is in use, and a 3-D display of the dose distribution delivered in brain tumor treatments has been developed using the PET scanner. In practice, new methods introduced for measurement of tissue response include tumor growth delay curves, fine-needle biopsy mapping, and PET scanning of brain tumors. The use of endoscopic assessment of the rectosigmoid region is emphasized. Treatment results of glioblastoma multiforme show that the median survival for patients treated to 125 pion cGy/fx is in the range of 187-198 days; for patients receiving 170 cGy per dose/fraction (fx) the range is 290-315 days, and for those receiving 200-220 cGy/fx the median survival is in excess of 290 days. For pelvic malignancies the local control obtained with doses of 2500 cGy or less was 50% in 12 assessable patients; it was 75% in 20 patients who had 3000 cGy or more.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1979

Transverse-sectional imaging with Na18F in myocardial infarction.

The potential utility of Na18F for acute infarct imaging was assessed in a canine model with a positron camera. Transverse-section imaging of radiofluoride in five dogs with acute myocardial infarction, using a multicrystal positron camera, clearly demonstrated the zones of damage as areas of increased activity. The F-18 uptake in the infarct zones was found to peak at 48 to 72 hr after coronary ligation, as does Tc-99m pyrophosphate. Preliminary in vitro studies indicate that the relative F-18 uptake, 48 after ligation, is an inverse linear function of regional blood flow.

Ammonia↗
PubMed1988

[Pion therapy at SIN--7 years' experience].

At SIN (Swiss Institute for Nuclear Research) cancer treatment with negatively charged pi-mesons was initiated in 1980, and 331 patients have been treated by the end of 1987. Patients were treated in a individually-made cylindrical couch with three dimensionally optimized dynamic tumor-conforming technique (spot scanning technique). Especially for retroperitoneal and pelvic soft tissue sarcomas pions seem to be promising with 3-year local control rate 94 percent and 3-year survival rate 70 percent (15 patient, 17 manifestations). And also prostate cancers seem to be well controlled by pions without any severe complications. From these results at least for these tumors it seems worthwhile to conduct phase III prospective trials.

Brain Neoplasms↗
PubMed1987

Clearance of chlamydial elementary bodies from the conjunctival sac.

The rate of disappearance of inactivated Chlamydia trachomatis elementary body (EB) preparations from the conjunctival sac was studied in monkeys. Direct fluorescent antibody (DFA) cytology showed that the majority of EB had been cleared from the eye within 24 hr of the inoculation of 1 X 10(6) inactivated EB, although small numbers of EB could be detected for up to 144 hr. The rate of clearance in normal and ocular immune animals did not differ, and formalin-killed and UV-inactivated EBs disappeared at a comparable rate. These studies suggest that chlamydial EB are cleared relatively quickly from the eye and support the notion that EBs detected by DFA cytology indicate the presence of current infection.

Animals↗
PubMedDate not supplied

Introduction to pion radiotherapy.

In recent years, radiation therapy has seen an influx of experimental treatment beams. The negative pi meson, or pion, is one such beam. It exhibits complex phenomena that may prove to be a major advance in the radiation therapy of some tumors. This paper discusses the pion beam at the Los Alamos Scientific Laboratory, Los Alamos, New Mexico.

Clinical Trials as Topic↗