Method and apparatus for measuring the intensity of preferably gamma radiation of radiation active deposit contained within a liquid sample

A method and an apparatus for isolating and measuring the intensity of gamma radiation or other type of radioactive radiation from a radiation active deposit contained within a liquid sample, in which the measurement is performed in step with a previous isolation of a sample by an intermittent advance (10) of the sample from an isolation station to a measuring station. The measurement is made in step with the intermittent advance of the sample in a plurality of immediately succeeding partial measurements in a measuring unit which comprises a plurality of successively arranged radiation detectors (36) corresponding to a predetermined number of partial measurements. Each partial measurement constitutes a part of the total measurement of the same corresponding to the step of advance. The measuring results from the individual partial measurements of the sample are summed up (60), and the sum is registered. The sample may be deposited on disc-shaped membrane filter carriers.

The invention relates to a method for isolating and measuring the intensity 
of gamma radiation or other type of radioactive radiation from a radiation 
active deposit contained within a liquid sample, the measurement being 
performed in step with a previous isolation of a sample by an intermittent 
advance of the sample from an isolation station to a measuring station. 
The measuring process is carried out in the way that the radiation active 
deposit contained in the liquid sample is isolated on a filter material by 
means of a filtration, whereafter the radiation intensity of the deposit 
is measured. 
Such measurements are e.g. made in connection with medical-analytical 
purposes, but are also used industrially. In practice, a considerable 
number of samples is usually examined successively. 
With this end in view one has previously proceeded in the manner that the 
individual samples are treated in succession each per se in such a manner 
that their radiation active deposit is isolated on a pre-manufactured 
strip-formed film roller with filter areas glued thereto through which the 
sample is filtered. The sample areas were hereafter covered with tape in 
order to prevent set-off, when the film is rolled up for the later 
measurement. When all samples are filtered, the film roller is transferred 
to a measuring apparatus which now starts a measurement of the samples, 
one sample at a time, in a single set of detectors. It is also known in 
principle for transportation of the samples to use a turn table. 
A finished measurement per sample lasts e.g. two minutes, while a 
filtration only takes about 20 seconds. The measurement can only be 
accelerated by reducing this time which would influence the accuracy of 
the measurement. 
The object of the invention is to provide a substantial acceleration of the 
measuring process so that the total time to perform a measurement for a 
great number of samples can be reduced considerably. 
This object is according to the invention obtained by making the 
measurement in step with the intermittent advance of the sample in a 
plurality of immediately succeeding partial measurements each constituting 
a part of the total measurement corresponding to the step of advance, 
summing the measuring results from the individual partial measurements and 
registering the sum. 
In other words the invention is due to the recognition that it is not 
necessary to perform a finished measurement for one sample at a time, but 
that the measuring process can be divided into a plurality of immediately 
succeeding steps and that the measurement of a plurality of samples can be 
performed simultaneously with each sample being at its own step. For 
instance the measurement can be carried out in six steps of 20 seconds 
each, so that six samples are treated simultaneously. Hereby the measuring 
work can be brought in a rhythm which substantially corresponds to the 
rhythm by an effected filtration without affecting the measurement 
accuracy. 
The invention relates also to an apparatus for carrying out the method. The 
apparatus being of the type which has a conveyor device for deposits on a 
filter, a filtering unit and a measuring unit for measuring the intensity 
of gamma radiation or other type of radioactive radiation, the conveyor 
device containing means for intermittent advance of a plurality of 
individual deposit samples past the filtering unit and thereafter past the 
measuring unit, and the apparatus is according to the invention 
characterized by the measuring unit comprising a plurality of radiation 
detectors corresponding to a predetermined number of partial measurements, 
said detectors being beside each other successively arranged opposite to 
the advance path of the samples and connected with a summing and 
registration apparatus for the measuring results of the detectors. 
In other words the apparatus is adapted for intermittent treatment of 
deposits in such a manner that the individual samples are advanced from 
station to station during the measurement process for carrying out an 
accurate total measurement of the radiation intensity of the isolated 
active substances. According to the invention the conveyor device can 
comprise a number of filter carriers, each for a membrane filter, and each 
filter carrier can preferably have the form of a disc being open in the 
middle thereof, the outer dimensions thereof being substantially greater 
than the membrane filter. Such a filter carrier can be mounted quickly and 
safely advanced and forms a suitable carrier means for the membrane 
filter, and if the filter carrier is formed with the stated outer 
dimensions, an edge portion would be available which partly ensures the 
arrangement of the filter carrier in the advancing conveyor means and 
partly contributes to shielding during the positioning of the samples at 
the detectors. According to the invention the membrane filter can also be 
an integral part of the filter carrier.

The shown embodiment for the apparatus is intended for isolating and 
measuring the gamma radiation intensity of gamma active deposits contained 
within a liquid sample which should be used for medical-analytical 
purposes. 
As shown in FIG. 1, the apparatus has a turn table 10 with twelve identical 
outwards open recesses 12 arranged along the edge thereof and occupying 
equal angles of arc. In these recesess filter carriers 14 in the form of a 
disc can be inserted from the outside parallel to the turn table 10, said 
discs having a plurality of central openings 16. The bottom of each recess 
12 has an opening 18 which can be positioned opposite to a vacuum source. 
The turn table 10 is adapted for stepwise turning over an arc of an angle 
corresponding to the length of the arc of an angle between the individual 
recesses 12 In the resting position each recess is thereby positioned by 
one of the stations A-M. 
At station A a filter carrier 14 for a sample is inserted which is to be 
treated. The filter carriers are supplied one by one from a magazine 20 by 
means of a slide 22, such as appears schematically from FIG. 2. 
At station C a piece of membrane filter 24 is deposited on the filter 
carrier 14, vide FIG. 3. The membrane filter material is supplied by means 
of advancing rollers 26 and cut in suitable lengths by means of a knife 
28. From station C to station D the openings 18 of the turn table move 
over an upwards open channel which is connected with a source for vacuum 
which through the openings 16 retains the filter material on the filter 
carrier 14. The cut piece of filter material 24 is smaller than the filter 
carrier 14. 
At station E a liquid sample from a liquid glass 32 is supplied to the 
filter material piece by means of a peristaltic pump 34, vide FIG. 4. The 
gamma active substances contained in the sample are isolated by filtration 
as deposits by use of an effective vacuum through a lower channel 30. 
The stations F-L constitute the measuring unit of the apparatus. Each 
station is formed by two oppositely arranged gamma detectors 36, vide FIG. 
5. The detectors are connected with the summing and registration apparatus 
for the measuring results of the detectors shown in FIG. 7. The summing 
and registration apparatus is adapted to sum the measuring results for 
each sample which successively passes the stations F-L, and thereafter to 
register the total measuring result, and the result being e.g. printed or 
shown on a viewing screen. 
At station M a finger 38 is pushed through a recess 40 in the turn table 10 
up behind the filter carrier 14 and pushes this one free from the recess 
12, such as appears schematically from FIG. 6. The recess 12 is thereafter 
prepared to receive a filter carrier for a new sample. 
The measurement of the gamma active deposits contained in the liquid 
samples is thus made with a rate corresponding to the time interval 
between the stepwise advance of the turn table 10 from station to station. 
The total measurement constitutes six times the time interval and can thus 
be very accurate. 
In the present example there is a total measurement result from a sample 
every 20 seconds with a total treatment time per sample of 2 minutes. This 
means a great measurement accuracy together with a quicker working rhythm. 
FIG. 7 shows a very schematized embodiment of a summing and registration 
apparatus which can be used to sum the measuring results of each 
individual sample, as it passes through the measuring stations F-L. In 
each measuring station F-L two detectors 50f and 52f respectively are 
arranged which are connected to a common analyzer 54f. (The small letters 
behind the reference numerals show in which station the means in question 
is arranged or to which station it belongs). The counting signals which 
from the two detectors 50f and 52f in each station are passed through the 
analyzer 54f of the same station are passed from the analyzer to a counter 
56f which alternately with succeeding latching circuits 58f is arranged in 
a common bus 60. The counters 56f and the latching circuits 58f are 
governed by common governing conduits 56 and 58 respectively in accordance 
with the advancing movement of the samples through the measuring stations. 
At the end of the bus 60 a collecting unit 62 is arranged which sums the 
signals of the bus 60 coming from the individual stations (counting 
values) for each individual sample and transfers the result to a 
registration unit 64 where the results are written out and/or shown. 
The applied detectors 50f and 52f can be of the same kind as previously 
used by this kind of measurements. The other parts can be of the kind 
which is usually known within the digital technique, for which reason 
their structure and equipment is not further described. 
The above described isolated and measuring technique can also be applied by 
other radiation types than gamma radiation.