Acta radiologica: therapy, physics, biology最新文献

In 14 healthy volunteers a method has been evaluated for simultaneous estimation of liver size and blood flow by dynamic gamma camera recording of Tc-sulfur colloid uptake in R--E cells of the liver. The reproducibility and convenience of the method was found to be such as to make it suitable for both scientific and routine clinical work.

Histology demonstrated new bone formation and bone destruction in rabbit mandibles irradiated with 20 Gy in a single exposure, but no abnormality following 10 Gy in a single exposure. Gamma camera examination of the 99Tcm-DP distribution could not demonstrate any abnormalities, and is concluded not to be effective in demonstrating early radiation injury to bone tissue. Radiation therapy is considered a negligible source of false positive findings in scintigraphy of the facial skeleton.

A similar distribution of 99Tcm, 45Ca and 85Sr was obtained when injected in rats as 99Tcm-labelled pyrophosphate or ethylene-1-hydroxy-1,1-diphosphonate (EHDP), 45Ca-chloride and 85Sr-choloride respectively. The highest concentrations occurred in bone and teeth. In EHDP-treated rats, isotopes were accumulated at sites of ectopic calcifications in the lung, kidney and stomach wall as well as in mineralized tissues. These results indicate that 99Tcm, when administered as 99Tcm-labelled EHDP accumulates predominatly in the inorganic rather than organic tissue components.

A roentgen ray fluorescence method was developed for the quantitative determination of iodine concentration in tissue. The method is based on the use of two beams, of which one excites the K roentgen rays of iodine, while the other does not. The concentration of iodine was determined from the difference between the counting rates of the fluorescent and the scattered radiation. The measurements were carried out with standard equipment consisting of a generator, a NaI)Tl)-detector and a scaler. An accuracy of 0.1 mg I per g was obtained with the radiation exposure of about 1 R.

The lymphatic transport of a radioactive tracer injected intralymphatically on the dorsum of the foot was determined before and after surgery in 3 patients with vulvar carcinoma. The centrally recorded activity curves showed different time courses before and after inguinal lymphadenectomy, suggesting that the lymphatic transport is short-circuited via lymphovenous anastomoses after lymphadenectomy. Thus, non-radical surgery for primary carcinoma combined with lymphadenectomy will increase the risk of haematogenous spread.

Mice were whole-body-irradiated with 5 fractions of roentgen rays in 5 days, 5 fractions of cyclotron neutrons in 5 days, or with mixed neutron-photon fractionated radiation, in the sequence n-n-x-x-x or n-x-x-x-n. The LD50/4 day values were determined. Roentgen rays and neutrons interact in the additive manner in the mixed fractionation schemes: effective dose per fraction is as predicted from the roentgen ray-only and neutron-only experiments. This essentially agrees with HENDRY et coll. (1976). However, no trend was found towards a less-than -additive effect which was observed by those authors and has also been suggested in skin response to mixed schemes (NELSON et coll. 1975).

The relative central absorbed dose preceding and following air layers and channels in a polytetrafluorethylene (teflon) phantom has been measured with LiF-teflon dosimeters. Focus phantom distance is set to 100 cm and the field sizes range from 3 cm X 3 cm to 6 cm X 6 cm. Absorbed dose decrease and build-up factors in front of and behind the air cavity are evaluated. The build-up factor is strongly dependent on field size. Measurements of absorbed dose in water and polystyrene yield approximately the same results as in teflon if the linear dimensions of the irradiation geometry (including depth in phantom) in water and polystyrene are equal to 1.84 and 1.99 respectively times the corresponding parameter in teflon. The underlying transformation procedure is derived. The absorbed dose correction factors in the region behind the slab are discussed in terms of tissue-air-ratio and effective attenuation formulae.