C. Ediss

Some aspects of the measurement of 32P Cerenkov radiation in water by a liquid scintillation spectrometer

Abstract The shift of the pulse height spectrum and the relative counting efficiency of 32P Cerenkov radiation in water were examined using a liquid scintillation spectrometer. This shift was related to the spectrophotometric absorbancy of samples containing various dyes. The isotope channels ratio method of producing a counting efficiency correction curve was found to be effective for coloured samples. It was observed that although the addition of some chemicals to the sample caused little change in the counting efficiency, a suspending agent (Cabo-sil∗®) produced a counting efficiency and spectral shift different from those obtained for the samples containing dyes. The absolute counting efficiency for 32P in water was found to be 30·5 per cent.

Toxicity, tissue distribution and excretion of 46ScCl3 and 46Sc-EDTA in mice

Abstract The acute toxicity, differential distribution in tissue, and elimination of ScCl3, 46ScCl3, Sc-EDTA and 46Sc-EDTA, in mice, has been investigated. The LD5024 hr doses for ScCl3 were 440 and 24 mg kg−1 respectively after intraperitioneal and intravenous injection, and 720 and 108 mg kg−1 respectively for Sc-EDTA. 46ScCl3 was extensively deposited in the liver and the spleen. 46Sc-EDTA was rapidly taken up by the kidney with subsequent elimation via the urine. Whole-body desaturation kinetics for 46Sc-EDTA were found to fit a three compartmental model. The fast elimination phase ( T 1 2 = 12.75 min ; K = 0.01722 min −1 ) accounted for 74.6% of the dose; the intermediate phase ( T 1 2 = 40.2 min ; K = 0.01722 min −1 ) for 21.8%, and the slow ( T 1 2 = 5351 min ; K = 0.00013 min −1 ) for 3.6% of the dose.

Liquid scintillation counting of radionuclides emitting high-energy beta radiation

Liquid scintillation counting of radionuclides emitting beta radiation with Emax>2 MeV has been investigated. Fluor volume effects were similar to those for low energy beta radiation, and pulse height spectra broadened in a predictable manner with no pulse clipping up to 4.913 MeV. Large changes in sample channels ratio due to color quenching resulted in progressively smaller losses of counting efficiency as beta energy increased. Counting efficiences were estimated to be near 100 percent for34Clm,36Cl,32P and38Cl. Cerenkov counting of38Cl by liquid scintillation counter was volume dependent for both counting efficiency and pulse height spectrum. Counting efficiencies for34Clm,36Cl,32P and38Cl were estimated to be 57.0, 7.5, 42.7 and 66.3%, respectively. Pulse height spectra were shifted to greater pulse heights as a function of beta Emax, supporting the possibility of energy discrimination for beta emitters by Cerenkov pulse height spectrum analysis. The advantage of singles Cerenkov counting over coincidence Cerenkov counting was greatest for36Cl and least for38Cl; this advantage was amplified more for samples of36Cl which had been color quenched than for similarly quenched samples of38Cl or32P.

Use of Aquasol scintillator micture for liquid scintillation counting of beta radioactivity in biological tissue

Abstract The preparation of biological tissues for liquid scintillation counting, by ultrasonic disruption, decoloration with hydrogen peroxide, and solubilization in Aquasol ® scintillation fluor, has been described. The high tissue-dependent background counts recorded at 25°C were found to decrease to satisfactory levels by cooling and assaying at 2°C. The isotope channels ratio method was found to be a suitable means of quench correction for both tritium and 14 C. External standard channels ratio quench correction was considerd to be unsuitable under these experimental conditions for both tritium and 14 C. Maximum counting efficiencies for tritium and 14 C were 19·5 and 80·4 per cent respectively. Up to 598 mg of tissue, 186 mg of feces and 1·13 ml of urine were radio-assayed using this method.

Implementation of the coincidence method for determining125I activity with an estimate of error

The established coincidence method of determining125I activities has been adapted for use with a multisample gamma counter. The method has been extended to include a formula which has been derived to indicate the precision of the measured activities. The validity of this formula has been tested and found to be satisfactory. The techniques used to select appropriate counting conditions are described.

Investigation of 113Inm-Indium oxinate as a possible lung-scanning agent☆

Abstract A rapid , simple method is described for the preparation of 113 In m -labelled indium oxinate particles. The radiopharmaceutical was evaluated as a potential lung-scanning agent by various animal studies including tissue distribution, organ scanning, toxicity and whole-body counting. Over 90 per cent of an intravenously administered dose in mice localized rapidly in the lungs. Lung scans performed on dogs afforded good visualization of pulmonary arterial capillary perfusion.

Some performance characteristics of modern liquid scintillation counters

Abstract Three examples of modern liquid scintillation counters were tested and several of their performance characteristics measured. Color and chemical quenched samples were counted in a Beckman LS 9000, a Packard 460C and a Tracor Mark III to test the reproductbility of different quench monitoring techniques. Instrumental differences and similarities are discussed and related to the performance of these counters. All three counters operated reliably over a wide range of sample quenching.

A broad spectrum colour quencher for liquid scintillation counting

Abstract A photon absorbing quencher (PAQ) has been developed to facilitate the testing of liquid scintillation counting systems. The components of this mixture have been selected so that all wavelengths of light emitted by a toluene based flour are uniformly absorbed. The use of dried filter paper carrier discs greatly simplifies the addition of this colour quencher to counting vials.

A pulse amplitude dividing circuit for nuclear applications

Abstract A pulse dividing circuit has been developed to provide analogue and digital outputs proportional to the ratio of the amplitudes of two nuclear pulses. Input pulses ranging from 200 mV to 10 V may be processed by the device. The pulse dividing circuit has been successfully incorporated as part of a small gamma camera.

High current pulser for transmural and field stimulation

The determination of the requirements and the design of a constant current pulse generator with low internal resistance capable of providing the high currents required for transmural and field stimulation of biologic tissues are described. It is concluded that direct measurement of current flowing and voltage applied to electrodes is the best way of monitoring stimulus parameters.