Acta radiologica: therapy, physics, biology最新文献

An extrapolation ionization chamber was constructed and used to measure depth absorbed dose distributions of electron beams from the electron therapy units in Finland. Particular attention was payed to the surface dose, the build-up region, and the energy calibration. Differences between various units are discussed.

The relative light output per Gy in polystyrene for roentgen beams of 6 and 42 MV and electrons between 2.2 and 34.5 MeV relative to 60Co gamma radiation is reported for different kinds of LiF dosemeters. The distribution of the absorbed dose inside a 0.25 and 0.4 mm thick LiF-teflon disc surrounded by polystyrene and irradiated with 60Co, 42 MV roentgen radiation and 39 MeV electrons was measured using 0.01 and 0.02 mm thick Lif-teflon discs. The measurements show that the absorbed dose distribution in the dosemeter depends on the energy of the radiation. When flat dosemeters were used, differences between the signals measured at the two orientations possible during read-out could easily amount to several per cent, and for this reason 0.4 mm and 0.5 mm LiF-Teflon discs were not trusted when the highest accuracy was required. The cavity theory by Burlin does not account for the phenomena caused by differences in electron scattering properties of the dosemeter and the phantom material. Some suggestions are presented for a different cavity theory for flat dosemeters dealing also with these phenomena. It describes the results to about the same degree of approximation as the Burlin theory, and fails to explain the observed energy dependence for electrons.

Survival rates for mammary carcinoma, based on the data of the Danish Cancer Registry for women admitted 1960 to 1966, show about the same values for women aged under 55 in stage I, whether surgical treatment has been combined with radiation therapy or not. For women aged over 55, combined treatment is followed by better survival rates than surgery or radiation therapy alone. For stage II, this applies both to younger and older women.

The 60Co applicator for treatment of retinoblastoma, described in 1963, has the advantage of exact local positioning. It is suitable in cases with solitary small tumours. The complications and the results of treatment in 20 patients followed up for at least 2 years are reported and discussed.

Combination chemotherapy (vincristine, adriamycin, cyclophosphamide, methotrexate with leucoverin rescue) in 32 patients with metastatic carcinoma of the breast resulted in an overall response rate of 81 per cent (9/32 complete remission, 17/32 partial remission). No serious side effects were noted. Karnofsky performance index improved in 24/26 responders.

The quantitative distribution of 90Y to 90Sr was affected after surgical removal of the parathyroids, adrenals, and male and female gonads. The activity ratio of 90Y to 90Sr (Q) and the concentration in bone of 90Sr, expressed in per cent of injected dose per 100 mg of bone ash, were determined. Parathyroidectomy and adrenalectomy reduced while ovariectomy raised the value of Q. Adrenalectomy and ovariectomy increased the concentration of 90Sr in bone. Some aspects of the metabolism of the two nuclides are discussed.

The first 22 MeV micron installation for radiation therapy is described with regard to the general design, the beam transport and the gantry. The first measurements of the electron depth dose curves indicate that the distributions obtained are superior to those of most betatrons and linear accelerators. For the same electron beam energy the depth of dose maximum and the 90 or 80 per cent dose level is considerably increased. The 20.9 MV photon beam has similar depth dose characteristics as a 20 MV betatron.

New Clambda-values (Cair,lambda) are proposed which should be applied for ionization chambers with an inner wall of air-equivalent material, air eq. plastic or graphite. The new values are up to approximately 3 per cent lower, and apply for a chamber with an inner wall lining of water-equivalent material.er cent higher than those published in the ICRU Report No. 14 and here named Cwater,lambda as the inner wall is considered water-equivalent. Also two sets of CE-values are proposed, namely Cair,E which is given in ICRU No. 21 and Cwater,E which is approximately 3 p