Apparatus for distribution evaluation of regional lung ventilation

Distribution evaluation of regional lung ventilation is obtained by placing a radionuclide and an array of scintillation detectors on opposite sides of a subject from evaluation units. Each of the signals from evaluation units of the detectors is stored in a memory. The signals are compared in a comparison block, and the comparison is recorded by a recorder.

BACKGROUND OF THE INVENTION 
The present invention relates to apparatus for the distribution evaluation 
of regional lung ventilation by means of the absorption of radioactive 
radiation emitted by an enclosed radionuclide which after passing through 
the subject being measured, is sensed by a set of scintillation detectors. 
At present, the nonuniform distribution of regional lung ventilation is 
most frequently judged from the prolonged mixing time, when breathing 
gaseous mixtures, while tracing the change in the concentration of a 
selected gas. In this case, the so-called wash-out or wash-in method can 
be employed. During tracing either nitrogen, inert gases, or 
radiopharmacons can be used. The methods employing the direct 
concentration measurement of nitrogen or inert gases, however, have a 
common disadvantage which consists in the fact that these methods are not 
sufficiently precise and therefore, can be used only for a general 
orientation. The location of the disorder is, however, impossible if these 
examinations are not carried out by gas sampling by means of gas analyzers 
corresponding to the gas used for the given purpose, the samples of the 
alveolar gas being taken from the bronchial tree. Another disadvantage of 
the examination of the regional function resides in the fact that the 
detected radiation of an isotope applied on the patient's body is also 
strongly influenced by the radiation absorption in the chest-wall and in 
the pleural effusion and so on, the magnitude of which cannot be 
designated, whereby the absolute and the relative evaluation of the 
regional ventilation is changed by a substantial fault making the result 
inaccurate. 
The introduction of catheters is, however, unphysiological and pretentious 
for both the examining doctor and the patient. The application of 
radiopharmacons permits the localization of the changes to be determined, 
e.g. by means of a gamma camera. However, economically it is very 
pretentious and owing to the use of open radionuclides, it is possible 
only in special medical situations. The application of open radionuclides 
is also disadvantageous environmentally, and of the radiation loading of 
both the patient being examined and the examining physician. A certain 
contribution to remedying these insufficiencies of the methods mentioned 
above could be obtained from the application of the modified apparatus as 
described in the Czechoslovak Patent Specification, No. 196 123 
(Simecek-Ryba: "The Apparatus for the Examinations of the Regional Lung 
Function"). By that apparatus regional ventilation can be registered but 
without the possibility of comparing and more exactly evaluating the 
changed distribution. The deficiency in that apparatus, however, can be 
seen in the fact that the number of the lung fields to be observed 
simultaneously is limited due to the low number of the available tracks of 
the lung fields to be observed simultaneously is limited due to the low 
number of the available tracks of the used recorder so that, in this case, 
the operations should be repeated during routine examinations. Owing to 
that, the accuracy of the evaluation has been considerably decreased with 
respect to the nonreproducibility of the conditions of the individual 
examinations following one another while simultaneously both the medical 
division and the patient being examined are exceedingly exposed to stress. 
SUMMARY OF THE PRESENT INVENTION 
The object of the present invention is to create apparatus for the 
distribution evaluation of regional lung ventilation by means of the 
absorption of radioactive radiation emitted by an enclosed radionuclide 
and after passing through the subject being measured, sensed by a set of 
scintillation detectors in which the output of every scintillation 
detector is connected to an associated input of an evaluation unit, the 
output of which is connected to an associated sector of a memory, and 
thereafter to a comparison block, the output of which is connected to a 
recorder in which both the comparison block and the memory are connected 
to a controlling unit. 
It is a further object of the present invention to connect a spirometer to 
the associated sector of the memory and that the respective output of the 
memory is connected to the comparison block. 
It is another object of the present invention that the output of the memory 
is on-line connected to a computer. 
It is still a further object of the present invention to arrange a 
radiopaque stop between the radionuclide and the subject being measured 
and a control system of the radiopaque stop to be connected to the 
controlling unit. 
It is still another object of the present invention to place the 
radionuclide into a collimator. 
When compared to the devices which have been employed up to the present, 
the apparatus according to the present invention is more accurate and 
economically more advantageous. 
Due to the fact that an enclosed radionuclide is employed, the application 
of this apparatus is not limited only to radioisotopic clinical divisions, 
and the radiation loading of the patient being examined and the attending 
personnel is relatively very low. When compared with the apparatus in 
which radiopharmacons are used, the apparatus according to the present 
invention is independent of the transport of the short half-life 
disintegration radioisotopes from the producer to the place of their 
future application so that thus any contamination of the environment can 
be prevented. The possibility of evaluating the regional distribution as 
well as the phase shifts of the regional breathing cycles is advantageous 
from the viewpoint of the diagnosis and the most efficient 
pharmacotherapy. The independence of the apparatus according to the 
present invention of employing the short half-life disintegration 
radioisotopes and a very low-degree radiation loading of the patient as 
well as the attending personnel permit repeated examinations to be carried 
out at any time, as required. The simultaneous tracing of both the 
regional lung ventilation and the spirometric curve permits the on-line 
converting of the relative values to the absolute ones. 
Further details of the invention will now be explained with reference to 
the accompanying drawing showing the embodiments thereof.

DESCRIPTION OF THE INVENTION 
A radionuclide 1 is located on one side of the subject 4 being examined 
while a set of the scintillation detectors 5 is placed on the opposite 
side of the subject 4 . The output of every scintillation detector 5 is 
connected to the input of an associated evaluation unit 6 in which the 
electric signal of the scintillation detector 5 is processed and a signal 
suitable to be stored in a memory 7 is generated. The output of every 
evaluation unit 6 is connected to an associated sector of the memory 7. As 
a memory it is possible to employ, for example, a multitrack tape recorder 
for the recording of slowly variable analogue signals. The outputs of the 
individual sectors of the memory 7 are connected to a comparison block 8. 
The memory 7 and the comparison block 8 are connected to a controlling 
unit 10 which ensures a gradual evaluation of the records stored in the 
memory 7 through the comparison block 8 by a recorder 9 which is connected 
to the output of the comparison block 8. The on-line connection of both 
the memory 7 and a spirometer 11, which is connected to the memory 7, to a 
computer 12 permits the processing of the signals together with the 
converting of the relative values to the absolute ones and the display of 
the signals according to a preset program. 
It is of an advantage to arrange a radiopaque stop 23 with a control system 
2a between the radionuclide 1 and the subject 4 being measured. The 
control system 2a is used for opening the radiopaque stop 2 only during 
the radioactive exposure. The control system 2a of the radiopaque stop 2 
is connected to the controlling unit 10. Further, the radionuclide 1 can 
be placed in a collimator 3 which collimates the radioactive radiation 
beam only within the required solid angle. 
The detectors are set in an array during examinations so that individual 
detectors evaluate the distribution in selected portions of the lung. As 
seen in FIG. 2, half of the detectors 5 are preferably spaced over the 
left lung and the second half over the right lung. When using six 
detectors, one pair of them is usually located at the upper fields of the 
lungs, the remaining two parts are placed at the middle and the low lung 
fields, respectively. During the breathing, the air contents of the lungs 
changes and the disturbed regional ventilation in each field of the lung 
results in changes of the absorbed radiation. By comparison of the changes 
in the quantity of the absorbed radiation as to the quantity and as to the 
time course, evaluation of the disturbed distribution of the ventilation 
of the quantity and time course can be carried out by mean of the computer 
or by means of a coordinate-recorded. 
Although the invention is described and illustrated with reference to a 
single of embodiment thereof, it is to be expressly understood that it is 
in no way limited to the disclosure of such preferred embodiment but is 
capable of numerous modifications within the scope of the appended claims.