Sören Mattsson

Ferrous sulphate gels for determination of absorbed dose distributions using MRI technique: basic studies

Two gels have been found to be suitable to load with ferrous sulphate solution. In these soft tissue equivalent phantoms, the absorbed dose distribution can be measured after irradiation in clinically used MR imaging equipment. The present studies were carried out using a 0.25 T NMR analyser without imaging properties. A ferrous sulphate solution, 0.05 M with respect to sulphuric acid, can be gelled with 4% gelatin to give a dosemeter which has a response which is linearly correlated (r = 0.998) with the absorbed dose in the interval 0-40 Gy. Ferrous sulphate solution can also be gelled with 1% agarose, but this gel has to be purged with oxygen to obtain a linear relationship (r = 0.997) in the same absorbed dose interval. The ferrous sulphate loaded gels have a sensitivity which is a factor of 2.2 or 4.0 times higher for gelatin and agarose, respectively, than the ordinary dosemeter solution. Because the standard deviation of background measurements is higher for the gels than for the dosemeter solution, the minimum detectable absorbed dose is about the same, or 1.0 Gy, for the two gels and the dosemeter solution. The sensitivity of the ferrous sulphate loaded gels shows no dependence on dose rate if the mean dose rate and the absorbed dose per pulse are within the limits normally used by accelerators for radiotherapy.

Decrease of skeletal lead levels in man after end of occupational exposure

Lead levels in finger bone were monitored using an in vivo X-ray fluorescence technique in retired lead workers. Eight subjects followed for 2-5 yr directly after end of exposure all displayed a decrease. Their average half-time was 7 (range 3-15) yr. In a second group of six persons, followed from year 7 to year 13 after finishing lead work, a decrease was seen in all but one. The average half-time for this group was 8 (range 2 infinity) yr. The mean value for both groups was 7 yr. The results show that there is a decrease of lead in bone after the end of exposure and that it is considerably faster than estimated earlier from various data on lead metabolism.

A method for in vivo analysis of platinum after chemotherapy: with cisplatin

A method to quantify the concentration of platinum in vivo by x-ray fluorescence (XRF) analysis is described. The measurement system consists of a roentgen apparatus, operated at 155 kV and 25 mA, and a high-purity germanium detector. In order to reduce the amount of scattered radiation in the detector the connecting links between the roentgen tube and scatterer, scatterer and patient, patient and detector, are arranged in a three-axial geometry with mutually orthogonal directions. With this system, quantification of platinum can be achieved with a minimum detectable concentration of 8 micrograms/g, for a measuring time of 30 min and an organ depth of 4 cm. The method can be used to follow the uptake and retention of platinum in patients treated with cisplatin, a frequently used cytostatic agent for tumour therapy.

Effective dose equivalent from radiopharmaceuticals

The concept of “effective dose equivalent”, which was introduced by the International Commission on Radiological Protection (ICRP) for occupationally exposed workers, has also created the possibility of expressing by means of a single figure, the radiation risk to patients undergoing different medical radiodiagnostic procedures. In this study, we present the effective dose equivalent for various nuclear-medicine investigations. The figures given are primarily based on a review of data contained in the literature on the mean absorbed dose to various organs. In many cases, however, our own calculations, using biokinetic data derived from the literature, have been used.It was found that for the different radiopharmaceuticals, the effective dose equivalent per activity unit administered extends over an interval of five orders of magnitude, from 0.00015 to 20 mSv/MBq. For the technetium-labelled compounds, the absorbed dose for 90% of the substances lies within the narrower interval between 0.0060 and 0.025 mSv/MBq. With the aid of the figures presented, each nuclear medicine department will be able to estimate the effective dose equivalent and, hence, the risk to patients undergoing different investigation.

Biological monitoring, by in vivo XRF measurements, of occupational exposure to lead, cadmium, and mercury

In vivo X-ray fluorescence (XRF) techniques were used for biological monitoring of lead, cadmium, and mercury. Lead accumulates in bone, the level of which may thus be used for monitoring of exposure. However, there was no close association between lead levels in bone and exposure time, partly because of differences in exposure patterns and partly, probably, because of variations in the toxicokinetics of lead. There are at least two separate bone lead compartments. The average over-all half-time is probably 5–10 yr. The finger bone level may be an index of the lead status of the total skeleton. In lead workers, the mobilization of bone lead causes an “internal” lead exposure and affects the blood lead level considerably. In cadmium workers, in vivo XRF is a sensitive and risk-free method for assessment of accumulation in kidney cortex, the critical tissue as to toxic effects; workers displayed increased levels. However, there was no clear association with duration and intensity of exposure, cadmium levels in urine, or microglobulinuria. Determinations of kidney cadmium may add important information on the state of accumulation and, thus, risk of kidney damage. Workers exposed to elemental mercury vapor, as well as fishermen exposed to methyl mercury, had mercury levels in bone below the detection limit of the XRF method.

Efficiency calibration of Ge spectrometers for measurements on environmental samples

Abstract A new method is described for the preparation of standard gamma-ray sources of various geometries and matrices using ion-exchange resin.

A sensitive method for quantitative measurements of the concentration of various gamma-emitting radionuclides in reactor plumes using a germanium detector

Abstract The Gaussian plume model has been adapted to calculate the primary photon fluence rate for a given release rate, height and distance over long periods and during different types of weather conditions. Corrections due to the varying efficiency of a Ge detector for different photon energies, angle of incidence and plume configuration have been developed. Using these, together with background measurements, minimum detectable release rates from nuclear power stations during normal operation have been estimated for radioactive inert gases. A carefully calibrated Ge detector, with proper lead shielding, is a sensitive instrument for long-term average measurements of radioactive plumes and is far superior to GM counters and ionizing chambers.The release rate may be evaluated more accurately than before by means of different dispersion models.

Environmental radiation protection studies related to nuclear industries, using AMS

14C is produced in nuclear reactors during normal operation and part of it is continuously released into the environment. Because of the biological importance of carbon and the long physical half-life of 14C it is of interest to study these releases. The 14C activity concentrations in the air and vegetation around some Swedish as well as foreign nuclear facilities have been measured by accelerator mass spectrometry (AMS). 59Ni is produced by neutron activation in the stainless steel close to the core of a nuclear reactor. The 59Ni levels have been measured in order to be able to classify the different parts of the reactor with respect to their content of long-lived radionuclides before final storage. The technique used to measure 59Ni at a small accelerator such as the Lund facility has been developed over the past few years and material from the Swedish nuclear industry has been analyzed.