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At least 109 records · Page 6Linked to original sources
PubMed1983

[Cancer therapy using particle radiation].

Radiation therapy, which has significantly been on progressed by introduction of high energy X-ray and gamma-ray machines, is reaching to a turning point in order to improve further the results of the treatment. The treatment with particle radiations, characterized by either the high energy transfer to the surrounding tissues or the excellent dose distributions, i.e. Bragg peak, are in clinical trials. The results up to date show that the locally advanced, and radioresistant cancers have been more successfully controlled by applying fast neutrons than use of x-rays and that the damage to the normal tissues was less in the proton therapy compared with the conventional radiations. It is suggested from this clinical trial that the effect of particle radiations be more enhanced when the heavy ions, i.e., Neon ions and Silicon ions, become available.

Elementary Particles↗
PubMed1985

Particle radiation therapy.

Current interest in attempting to identify any therapeutic advantages of beams of heavy particles (heavier than electrons) over photons is based on differences in physical absorption and radiobiologic interactions. The article discusses: dose distributions in tissue, which are markedly different for particles than for high energy photons and so may be clinically advantageous for the former; differences in radiobiologic responses, which could lead to increased tumor cell killing and a possible increase in the therapeutic ratio for particles; clinical experience to date; directions for and impediments to future research.

Dose-Response Relationship, Radiation↗
PubMed1978

Proposal for a program in particle-beam radiation therapy in the the United States. A report from the Committee for Radiation Oncology Studies (CROS) and its Particle Subcommittee.

The Program for Particle Therapy proposes utilization of hospital-based particle generators in a nationwide program to evaluate, through meaningful clinical trials, particle radiation therapy and the impact its utilization can have in cancer care. The scientific rationale for use of particle therapy compared to conventional radiation in the effort to achieve uncomplicated local control of cancer, to heal, cure and palliate the patient, indicates the advantages of particle therapy consist of either or both a) enhanced biological effect and b) physical properties leading to improvement in dose distribution. It has been estimated that in tho control local-regional cancer. Any new modality enabling the therapist to increase dose to tumor, while sparing critical normal tissue, can enhance local control and benefit systemic therapy. Limited clinical trials to date warrant further definitive clinical study of particle beams. Physical and biologic considerations of fast-neutron beams have been essentially completed; equipment design, availability, and predicted reliability are good; and the medical community has indicated support of further study. A major clinical investigation can be implemented to provide the scientific basis for judging clinical merit of use of high LET radiations. Concurrently, the first phase of work can be started with protons, negative pions, and heavy ions. It is anticipated that clinical results will accrue much more rapidly with hospital-based units for clinical trials; this Program proposes this transfer of particle technology from the laboratory to such hospital-based facilities in two phases, over a 10-year period.

Clinical Trials as Topic↗
PubMed1987

Treatment planning for particle radiation therapy.

Fast neutrons beams from the new medically dedicated cyclotrons in the US have depth dose characteristics comparable to photon beams from a 6-MV linear accelerator, at best. Treatment planning will have specific difficulties related to the relatively increased radiosensitivities of the brain, spinal cord, lens of the eye, and salivary gland. Therefore, exploitation of the potential biologic advantages compared to high energy photons will extract the price of increased difficulties in treatment planning. Dosimetric advantages of protons and helium ions compared to high energy photons are real and make possible the high-dose irradiation of cancers immediately adjacent to sensitive critical normal structures. Treatment planning and delivery with a precision of less than 2 mm is necessary. Such methods are already operational. Particle radiation therapy facilities are national resources, which can help the clinical radiation oncologist in the unique management of a few, specific problems.

Elementary Particles↗
PubMedDate not supplied

[Evaluation of biological effectiveness of high-energy accelerated particles based on the study of cytogenetic disorders in murine sex cells].

The frequency of reciprocal translocations in spermatogonia of F1(CBAxC57Bl6) mice irradiated with 50 MeV protons, 4.2 GeV deuterons, 1.8 GeV/nucleon helium ions or 60Co gamma-rays was investigated. The relative biological effectiveness of these particles calculated by comparing the equieffective doses of reference and experimental radiations was less than 1.0 under the assumption of the linear dose-effect relationship. The RBE of the particles calculated by means of the nonparametric method largely depended on the doses applied.

Animals↗
PubMed1984

Possible biomedical applications of antiproton beams: focused radiation transfer.

A calculation of the energy lost by antiprotons stopping in water shows that the radiation transferred is localized within 1 mm of the stopping point. This "focusing" of the radiation is mainly due to heavily ionizing particles emitted from the nuclei on which the annihilation takes place. At present antiproton beams for medical purposes may not be cost effective compared to other charged particle beams, but the sharpness of their radiation transfer combined with antiprotonic radiography are highly attractive and unique features that may invite special applications.

Elementary Particles↗
PubMed1979

Particle radiation therapy: requiem or reveille.

The 1960s and 1970s witnessed a surge of many institutions devoted to electron therapy. Currently, many facilities are adding or have added particle types of radiation to their armamentarium against cancer. The authors review the concepts, problems, and potentials of this form of therapy.

Elementary Particles↗
PubMed1981

Multiple scattering distributions for therapeutic pion beams.

Accurate treatment planning for therapeutic beams of negative pions requires knowledge of the multiple scattering of pions in biologically relevant materials. Complete spatial and angular scattering distributions have been measured for pions in scatterers of carbon, water and calcium. Measurements were made for targets varying in thickness from 0.5 to 21 g cm-2 and for pions with ranges of approximately 12 and 20 g cm-2. An array of scintillators, multiwire drift and multiwire proportional chambers was used to record the scattering of individual particles. These data are compared with the results of Molière scattering theory. The implications for pion treatment planning are discussed.

Elementary Particles↗
PubMed1980

Lung clearance of particles in two strains of rats.

Two strains of commonly used experimental rats were compared with regard to lung clearance of TiO2 particles. The Fisher 344 inbred rats retained predictably fewer particles after a 7-hr exposure than the larger outbred Long-Evans rats. This fact can be expected in view of the different lung size of the two strains. In addition, clearance of the retained particles was significantly slower in Fisher 344 rats. Differences in lung clearance capacity of different animal strains should be considered when experiments in inhalation toxicology are performed.

Aerosols↗
PubMed1983

Response of colony-forming units-spleen to heavy charged particles.

Survival of colony-forming units-spleen (CFU-S) was measured after single doses of photons or heavy charged particles from the BEVALAC. The purposes were to define the radiosensitivity to heavy ions used medically and to evaluate relationships between relative biological effectiveness (RBE) and dose-averaged linear energy transfer (LET infinity). In in vitro irradiation experiments. CFU-S suspensions were exposed to 220 kVp X rays or to 20Ne (372 MeV/micron) or 40Ar (447 MeV/micron) particles in the plateau portion of the Bragg curve. In in vivo irradiation experiments, donor mice from which CFU-S were harvested were exposed to 12C (400 MeV/micron). 20Ne (400 or 670 MeV/micron), or 40Ar (570 MeV/micron) particles in Bragg peaks spread to 4 or 10 cm by spiral ridge filters. Based on RBE at 10 survival, the maximum RBE of 2.1 was observed for 40Ar particles characterized by an LET infinity of approximately 100 keV/micron. Lower RBEs were determined at lower or higher estimated values of LET infinity and ranged from 1.1 for low energy 40Ar particles to 1.5-1.6 for low energy 12C and 20Ne. The responses of CFU-S are compared with responses of other model systems to heavy charged particles and with the reported sensitivity of CFU-S to neutrons of various energies. The maximum RBE reported here, 2.1 for high energy 40Ar particles, is somewhat lower than values reported for fission-spectrum neutrons, and is appreciably lower than values for monoenergetic 0.43-1.8 MeV neutrons. Low energy 12C and 20Ne particles have RBEs in the range of values reported for 14.7 MeV neutrons.

Animals↗
PubMed1981

New modalities in cancer treatment: heavy charged particles.

Heavy charged particles represent the ultimate that the physicist can contribute to the development of radiation sources for therapy. Of the heavy charged particles, protons are the least expensive to accelerate and can be manipulated to give a sharply defined high-dose volume with a rapid fall-off of dose outside the target area. The biological properties of protons do not differ significantly from X or gamma rays. Negative pi mesons require an elaborate accelerator for their production. Pions offer the possibility of concentrating energy, some of it densely ionizing with a reduced oxygen enhancement ratio and elevated biological effectiveness within the designated tumour volume, while minimizing the dose of sparsely ionizing radiation to the normal tissues traversed. High-energy heavy ions offer the greatest flexibility and allow localized dose distributions and also, with the higher Z particles, a substantial reduction of the oxygen enhancement ratio can be achieved. The ultimate choice of particle depends upon what turns out to be the most important factor in radiotherapy--an improved localization of dose or a reduction in the dependence of cell killing on the presence of molecular oxygen.

Elementary Particles↗
PubMedDate not supplied

Basic and applied research at the TRIUMF meson factory.

The TRIUMF 520 MeV H- cyclotron produces intense beams of protons, pions and muons supporting basic research in nuclear, particle and solid-state physics, nuclear chemistry and biomedicine, and applied research in electromagnetic breeding of nuclear fuel, proton radiography, radioisotope production and cancer treatment.

Animals↗
PubMed1987

Influence of the physical state and straggling on the computation of the radiation dose due to radon daughters deposited in the lung.

The effect of the physical state (phase) of the absorbing medium and the energy straggling of the alpha particles on the calculation of the radiation dose due to the daughter products of radon deposited in the lung have been studied in detail. The stopping power data for alpha particles in water and water vapour have been used. It has been found that the effect of straggling on the stopping power calculations is small, and therefore its contribution to dose calculations is negligible. The phase effect has been found to be dependent on the energy of the alpha particles and the depth in the medium. If the stopping power of water vapour is used instead of that for liquid water, the dose may be overestimated by 5-20 and 1-11% for 6 and 7.7 MeV alpha particles, respectively, at the beginning of alpha range, and underestimated by 15 and 40% respectively for the above energies at the end of the range.

Dose-Response Relationship, Radiation↗
PubMed1986

Induction of proline prototrophs in CHO-K1 cells by heavy ions.

Using an established mammalian cell line, Chinese hamster ovary cells (CHO-K1), we have observed the induction of prototrophs by various heavy ions. This cell line requires proline for normal growth in medium with low serum concentration. X-rays, three types of heavy particles (600 MeV/u iron, 670 MeV/u neon, and 320 MeV/u silicon ions), ethylmethane sulphonate and 5-azacytidine were used to induce revertants which were proline independent. Log-phase cells treated with 5-azacytidine showed a very high reversion frequency. The induction frequency per viable cell appears to be dose dependent for these four types of radiation, and the dose-response curves are approximately linear. Our results also indicate that the effectiveness of high-LET particles in inducing proline prototrophs is much greater than that of low-LET radiation. The RBE value for the induction of prototrophs was calculated for neon, silicon, and iron particles and found to be about 1.3, 1.7 and 4.5, respectively. At equal survival level, the reversion frequency for X-rays and EMS was about the same.

Animals↗
PubMedDate not supplied

Measurement of the effect of inhomogeneities and compensating bolus in clinical pion beams.

Measurement of the effects of Telfon and air inhomogeneities on the ionization distributions of clinical negative-pion beams have been made at the Los Alamos Meson Physics Facility. Inhomogeneity location and pion-beam energy vary the effect of multiple coulomb scattering on the dose distribution lying in the penumbra of the inhomogeneity. CH2 bolus adequately corrects for the effects of these inhomogeneities. Bolus misalignment less than 0.5 cm does not seem critical because of large multiple coulomb scattering of the pion beam. However, this and secondary particles emitted from pion stars prevent the pion beam from being precisely shaped with sharp edges, as demonstrated by measurements under a patient bolus.

Elementary Particles↗