Radiation research. Supplement最新文献

Between 1956 and 1977, the former synchrocyclotron in Uppsala was used for biological experiments and clinical tests with 185-MeV protons. Therapeutic irradiations have been performed since 1957 by cross-firing with pencil beams through small intracranial structures for the treatment of Parkinsonism and intractable pain and with the spread-out Bragg peak for the treatment of large malignant tumors. Radiological and radiophysical aspects of the use of charged-particle beams were studied in detail. The former accelerator is now being converted to a sector-focusing, frequency-modulated cyclotron, SFSC-200, to permit acceleration of protons up to 200 MeV and other light ions to corresponding energies. Production of spallation neutrons and radionuclides for biomedical uses is expected to start this year. Experiments with charged-particle beams will begin in 1986. This paper presents a discussion of accelerator developments for planned experimental and clinical programs.

The present method for predicting the radiocurability of individual human tumors is based upon considerations of tumor size, site, histological type and grade, and host factors such as sex and age. Small tumors located such that normal tissues do not seriously limit total dose and those with "favorable" histology are more radiocurable than large tumors located over a critical normal tissue. However, the precision of prognosis based upon those features is relatively low. The need for other parameters for more accurate predictability is greater than ever because of the existence of different radiation modalities, including neutrons, and the development of a broad range of chemotherapeutic drugs that can be used alone or in combination with radiation and surgery. In this laboratory we are testing the micronucleus (MN) assay for measuring the relative biological effectiveness of high- and low-LET irradiations in mouse tumors and a new primary human tumor cell culture system for making direct measurements of tumor cell radiosensitivity. The potential usefulness of these two systems in predicting human tumor response to radiotherapy is discussed.

Negative pi mesons (pions) were used to treat 227 patients at the Los Alamos Meson Production Facility (LAMPF) between 1974 and 1981. Persisting local control values for 129 patients treated with pions alone in the following tumor sites were recorded at a minimum post-treatment observation interval of 2.5 years in the following tumor sites: cerebral gliomas 3/29; head and neck, 8/31; lung, 1/7; pancreas, 0/17; large bowel, 3/13; cervix, 2/45; bladder, 3/4; prostate, 18/20; miscellaneous sites, 0/4. Late severe sequelae ranged from none to 30% for major sites. A dose-response relationship was seen for late severe sequelae with a high probability following dose levels of 4750 cGy (max) in approximately 38 fractions. RBE values for pions appeared to lie in the range of 1.4-1.6 for both acute normal tissue reactions and late sequelae. At the Swiss Institute for Nuclear Research (SIN), 126 patients were treated in Phase I-II protocol studies between 1982 and 1984 with a new technique of scanning with a focused spot of pions. With minimum observation intervals of only 6 months, the local complete response values in 67 evaluable patients treated with pions alone to selected sites are gliomas 1/15 (9 months); pancreas, 3/11; cervix, 4/8; bladder, 18/26 (at 1 year, 9/22); sarcomas, 4/5; biliary tract, 3/4. Late severe sequelae ranged from none to 50% for major sites. A steep dose-response relationship is seen for late severe sequelae with high probability following doses exceeding 3800 cGy (max) in 20 fractions and very low probability with doses below 3500 cGy (max).

The Harvard Cyclotron Laboratory in collaboration with the Department of Radiation Medicine of the Massachusetts General Hospital and the Retina Service of the Massachusetts Eye and Ear Infirmary provides low-LET heavy particle therapy with 160 MeV protons. The improved dose distribution of protons results from their physical characteristics. A total of 965 patients have been treated as of December 31, 1984. Dose is expressed in units of cobalt gray equivalent (CGE) which is the dose in Gy multiplied by the RBE (1.1) for modulated protons relative to 60Co radiation. Sixty-seven patients with chordomas or low-grade chondrosarcomas of the base of skull or cervical spine have received proton treatment. Forty-three of these patients have been followed for at least 8 months with a median follow-up of 27 months. The median dose is 69 CGE. The 3-year actuarial local control rate is 89%. Seven patients with gliomas, eight with craniopharyngiomas, and six with meningiomas have also received proton radiation treatments. A total of 615 patients with uveal melanomas have received a median dose of 70 CGE in five fractions. Tumor regression has been seen in 94% with 66% having vision of 20/100 or better.

We report on the first decade of the helium-ion radiotherapy clinical trial being carried out at the Lawrence Berkeley Laboratory. Over 500 patients have now been treated. We have had very good results to date in treating patients with small tumors critically located near a radiation-sensitive organ which would preclude delivering a curative dose with conventional radiotherapy. On the other hand, patients with larger tumors where the tumor dose cannot be increased more than 10% over conventional radiotherapy have not responded well to helium ion radiotherapy. This is illustrated by discussing selected patient groups in detail, namely those with uveal melanoma, small, low-grade tumors near the central nervous system, carcinoma of the pancreas, and carcinoma of the esophagus.

An overview is presented of the early production of water radicals due to the passage of fast charged particles. It starts with energy deposition in tracks followed by the time scale of events of importance to radiation chemistry and radiobiology. Primary radical yields and reaction schemes, considered independent of particle LET but functions of the phase of the medium, are discussed within the framework of diffusion kinetics. Taking these primary G values (i.e., 100-eV yield) of OH, e-aq, and H as 5.70, 4.78, and 0.62, respectively, in liquid water, simple examples are provided for the evolution of the radical species. Finally, attention is drawn to some special physical features of fast, heavy charged particle tracks.