Kurt Liden

99mTc-labelled human serum albumin: A study of the labelling procedure

Abstract The procedure for labelling human serum albumin (HSA) with 99m Tc has been examined in detail. The labelling efficiency was determined by separating the labelled HSA from free 99m Tc on a Sephadex column. The best labelling was achieved by adding at least 5 mg FeCl 3 ·6H 2 O and about 10 mg ascorbic acid to 5 ml of the 99m Tc0 4 − eluate from a 99m Mo column and by adjusting the pH value to 6·8–7·0 prior to addition of HSA. The pH must then be adjusted to 2·3–1·9. The incubation time was found to be important for labelling efficiency when less than 100 mg HSA was used. The best anion exchange material for washing the solution from free 99m Tc was found to be Dowex 1X8. A simplified procedure for labelling HSA with 99m Tc is also given.

The yield of characteristic X-rays excited by β-rays

Abstract The intensity of the K X-ray peak from β-ray sources of Pr143 (Eβmax 0·92 MeV) and Ce144-Pr144 (Ebmax 2·98 MeV) sandwiched by tin or lead radiators was measured with a NaI (TI) scintillation spectrometer. The following maximum yields given as photons per disintegration were found: tin + Pr143, (15–35 keV): 0·028 at a radiator thickness of 68 mg/cm2, lead + Pr143, (60–100 keV): 0·043 at 120 mg/cm2, and lead + Ce144−Pr144 (60–100 keV): 0·21 at 270 mg/cm2. These results together with those of Liden and Starfelt show that: (1) The ratio between the number of photons in the K X-ray peak and the total number of high energy bremsstrahlung photons for optimum radiator thickness is about 3:1 for low-energy betas + tin, and about 1:1 for high-energy betas + lead. (2) The K X-ray peak intensity increases with Eβmax and with the Z of the radiators; but so does the high-energy bremsstrahlung. The radiator thickness for maximum yield increases with Eβmax at low energies and levels off at a value of about 300 mg/cm2 for high-Z radiators and Eβmax > 3 MeV. Some practical applications are commented upon, particularly the possibilities of Kr85.

Semi-Portable Whole-Body Counter for Cesium 137 and Other Gamma-Emitting Isotopes

A whole-body counter for determination of body burdens of Cs/sup 137/ and other isotopes is described. The counter, easily assembled and disassembled, has small dimensions and the weight is less than 1500 kg. The background reduction is obtained by lead shielding. Effect on the background of the nadioactive environment and of the size of the subject was studied. The measuring geometry, a 5 in. x 4 in. NaI(Tl) crystal in a 42 cm chair geometry, has been calibrated by comparison with a static iron-room counter. The sensitivity is 2.76 cpm/nC/sup 137/Cs. Measuring accuracy as a function of body burden and background is analyzed. (auth)