JPS5853302B2 - Device for preparing blood films on microscope slides - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for preparing blood smear slides for analysis, particularly within a period of time, which time is a function of the blood concentration of the blood, and is related to the rotation of the slide.

In analyzing a blood sample, the blood is smeared onto a laboratory slide and the smear is colored.

A laboratory technician counts the white blood cells on a colored smear and performs a method called leukocyte subtraction.

Since this subtraction method is frequently used in hospitals, automation of this subtraction method has important economic benefits.

One automated device is described in J. W. Bekus, ``Automatic Classification of Leukocytes in Peripheral Blood by Digital Image Processing, 1'', submitted by the University of Illinois at Chicago in 1971.

Pending U.S. Patent Application No. 353,004 to Douglas A. Kotter, filed April 20, 1973, entitled "Image Scanning Converter for Automated Analysis of Slides," describes a method developed by a co-investigator of the present inventors. An apparatus is described for automatically scanning and determining the relative numbers of different types of white blood cells on colored smears.

American Journal of Clinical Pathology Vol. 51, No. 214-22, 1969
M, Ingram and F listed on page 1.

M. Minter's article ``Semi-automatic preparation of coverslip blood smears using a centrifuge'' describes the creation of a blood monolayer by centrifugally spinning a slide wet with blood.

The method described in the text includes a method in which blood flows down a cover glass, the cover glass is placed on a plane parallel to the rotating plane of a centrifuge, and centrifugal force is rapidly applied. The cells are blown away, leaving a well-spread monolayer of blood cells on the coverslip.

Centrifuges for spinning blood smear slides are commercially available.

Such equipment is available from the Pratt General Company, 947 Old York Road, Abington, Pennsylvania.
Certain commercially available blood rotation devices available from PerkinElmer Company, 50 Danbury Road, Wilton, Conn., and Shanton Scientific Company, 515 Broad Road, Seewickley, Pennsylvania, have a rotation time of Although having a control device to adjust the rotation time, it is practical to set this rotation time in one location and keep it the same during subsequent blood slide preparation.

After using the centrifuge and blood spinning techniques described above, the inventor made the following observations.

Separation of red blood cells is not the same for all blood samples.

In some blood, due to the rotation, the blood film is in a state where the blood cells are clustered together and the blood cells are diluted.

For other blood, this technique causes the blood cells to overlap on the slide.

As mentioned in Ingram's paper, the morphology of red blood cells often changes.

The blood cells become very flat and no longer round.

White blood cells (especially neutrophils) are often seen in a damaged state.

A large amount of blood had to be used in order for the blood film to be uniform.

Typically, blood was flooded onto the surface of the slide before it was rotated.

If the entire surface was not wet, the irregular “
A sun-shaped pattern occurs.

Manual methods of obtaining blood smears (wedge slide and coverslide methods) require a skilled operator;
Results are not reproducible and the distribution obtained is not uniform and often contains a high percentage of broken blood cells.

U.S. Patent Application No. 3,577,267 to Breston et al. and U.S. Patent Application No. 3,705,048 to Staunton
The patents describe centrifuges that can be used to prepare blood slides; however, the devices described in these patents produce blood with good cell morphology and distribution for all blood samples. The problem of making a smear cannot be solved.

Preparation of slides suitable for automated leukocyte subtraction is therefore a critical task, and to obtain reproducible results it must be operated by an operator that does not require subjective judgment. This is the conclusion of the inventor.

According to the invention, a blood film with good blood morphology and blood distribution can be obtained for a short period of time, determined as a function of the red blood cell concentration.
It is created by applying a centrifugal force field to a slide at a constant rotational speed.

According to the invention, an apparatus for preparing blood slides includes a drive circuit that controls the rotation time of a centrifuge that rotates the slide.

The variable control device for the drive circuit can be adjusted manually using a scale displayed as a function of the red blood cell concentration of the blood.

In using this device, the operator observes the percentage of hematocrit (the percentage of blood volume filled by red blood cells) either by test or visual observation.

The operator sets the manual control to the indicated blood hematocrit rate.

When the device starts running, the rotation time is automatically adjusted to match the blood to blood percentage.

The objects, features and advantages of the present invention as described above, as well as other objects,
The features and advantages will become more apparent from the following more detailed description and claims.

In FIGS. 1 and 2, a blood smear slide 11 is placed in a recess in a plate 12. In FIGS.

The flat plate is fixed to the output shaft of a high torque, low inertia DC motor 13.

A drive circuit 14 controls the motor 13.

The variable control device 15 of the drive circuit includes a variable resistor that is adjusted in relation to a scale expressed as a function of the red blood cell concentration in the blood.

Start switch 16 starts the centrifuge motor and the motor is immediately accelerated to the selected rotational speed.

The motor maintains this selected speed for a period of time determined by variable controller 15.

Two safety interlock switches 11 and 18 operate the centrifuge.
It is driven by a closed lid.

The centrifuge motor only runs when the lid is closed.

This is a safety device that prevents the slide from exiting the confines of the machine in the unlikely event that the slide slides out of the recess in the plate.

An on-off switch 19 sends power to drive circuit 14 .

FIG. 3 depicts the housing 20 of the device.

The outer jacket includes a lid 23 with chimney mating,
You can reach into the plate through the lid.

The hinged lid 23 is the safety interlock switch 11
and 18.

A start button 21 is provided to start the rotating motor.

Knob 22 adjusts the variable control according to a scale displayed as a percentage of hematocrit.

FIG. 4 shows the turnover time as a function of the percentage of blood hematocrit, which the inventors have found is a good measure of red blood cell concentration.

After knowing the hematocrit percentage in advance, the slide can be rotated at a constant speed for a time that is a linear function of the hematocrit percentage to obtain a good membrane.

Other measures of red blood cell concentration can also be used.

For example, hemoglobin concentration can be used as one scale.

As the red blood cell concentration increases, it is important to apply centrifugal force to the blood for a longer time or more forcefully.

It is therefore possible to keep the rotation time constant and vary the rotation speed as a function of the red blood cell concentration, but the rotation speed should be kept at an optimum in order not to change the morphology of the blood cells.

The present inventor found that the faster the rotation speed, the more easily the blood cells are destroyed.

Rapidly accelerate until the final rotation speed is reached, only 200-
300ms or \ru), 5000R.

Motor rotation speeds P and M can be used.

At this speed the time can be adjusted to obtain a good blood monolayer as shown in FIG.

FIG. 5A depicts a microscope slide subjected to centrifugal force at too high a speed or for too long a time.

The normal red blood cell morphology is disrupted, and the large and small blood cells become extremely flattened and spread out.

(For convenience, only part of the slide when blood was smeared is shown in Figures 5A, B, and C.

In fact, after applying centrifugal force, the entire slide is uniformly covered with blood.
).

Figure 5B depicts a slide that has been properly centrifuged.

Normal blood cell morphology is maintained.

In Figure 5C, the distribution of blood cells is too dense as a result of the rotation time being too short or the velocity being too low.

Often the operator can use a blood analysis result that provides a percentage of hemadcrit.

However, when an accurate hematocrit percentage cannot be obtained, it is possible to estimate whether the hematocrit percentage is low, normal, or high based on the redness of the blood.

FIG. 6 shows a variable control device for adjusting the rotation time.

When the start button 24 is pressed, the capacitor 25 is discharged.

This causes transistor 26 to conduct.

This causes capacitor 21 to then discharge.

Immediately, the output of the operational amplifier 28 shifts to a positive level.

Because of the large resistance of resistor 29, transistor 26 cannot remain conductive after capacitor 25 has discharged.

Transistor 26 is therefore cut off, thereby recharging capacitor 2T through variable resistor 30.

When the voltage vT applied to the input of operational amplifier 28 returns to vR/, the output returns to a low level.

This stops the motor.

The resistance value of resistor 30 can be varied to vary the recharging time and therefore the motor drive time.

Resistor 30 is placed in relation to a scale calibrated in percentage of blood hemadocrit.

Another variable resistor 31 varies the input voltage to the motor drive circuit, thereby controlling the speed.

The output to the motor drive circuit is provided by transistor 32.

FIG. 1 shows the motor drive circuit.

The input to this circuit is supplied by the control circuit of FIG.

Its input is applied to an amplifier 33 whose output drives a DC motor 34 via transistors 37,38.

DC motor 34 includes a resistor (R). When current i flows through the resistor, a voltage drop iR occurs.

DC motor 34 also includes an inductance.

When the motor rotates, a back electromotive force proportional to the rotational speed is generated in the inductance.

The amplifier 35 inputs the voltage drop jl in the motor to the negative input terminal (-
) and generates a signal proportional to the negative number.

Resistors 36, 39, 40 combine the output of amplifier 35 and the voltage applied to the motor to produce a feedback signal indicative of the back emf that is directly proportional to motor speed.

This feedback signal is then applied to the negative input of operational amplifier 33.

Transistors 37 and 38 provide the actual motor drive current.

The operation is performed as follows. When the input from the drive circuit is positive, motor 34 rotates at a speed related to the voltage of the input signal.

The motor stops when the input voltage becomes zero.

Amplifier 33 compares the desired speed at its positive input with the actual speed indicated by the back emf signal applied to its negative input.

The output of operational amplifier 33 is an error signal that either conducts transistor 31 to accelerate the motor or conducts transistor 38 to decelerate the motor.

In summary, when the start button is pressed, the input to the circuit of FIG. 1 becomes positive.

This makes transistor 31 conductive and therefore motor 3
4 to the required speed within a short period of time.

Operational amplifier 35 and its associated resistor sense the motor back emf and generate a feedback signal proportional to the actual motor speed.

This feedback signal is applied to a feedback loop which drives the motor at a controlled rotational speed.

When the input to the circuit of FIG. 1 returns to a zero level, transistor 38 becomes conductive.

This action sends a reverse polarity current to the motor 34, and the motor stops within a short time.

Although particular embodiments of the invention have been shown and described, various modifications are possible within the true spirit and scope of the invention.

The claims are intended to encompass such modifications in their meaning.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the blood rotation device of the present invention. Figure 2 shows the kema plate and blood slide. FIG. 3 is a pictorial diagram of the apparatus. FIG. 4 shows the hemadcrit percentage as a function of rotation time. Figure 5A depicts a blood slide that has been centrifuged for too long. Figure 5B depicts a blood slide that has been centrifuged for approximately the correct amount of time. Figure 5C depicts a blood slide that has not been centrifuged for sufficient time. FIG. 6 is a schematic diagram of the variable control device. FIG. 1 is a schematic diagram of the drive circuit. 11... Blood smear slide, 12... Child plate, 13... DC motor, 14... Drive circuit, 15... Variable control device , 16...
・Start switch, 11゜18...Safety interlock switch, 19...On-off 4'/chi, 20...
... Outer cover, 21 ... Start button, 22 ...
...Notsupu, 23...Futa, 24...
...Start button, 25... Capacitor, 26.
...transistor, 21 ... capacitor, 28 ... operational multiplier, 29 ... resistor, 30, 31 ... variable resistor, 32...
・Transistor, 33... Operational amplifier, 34.
...DC motor, 35... operational amplifier,
36...Resistor, 37,38...Transistor, 39゜40...Peep resistor〇

Claims (1)

[Scope of Claims] 1. A centrifuge that rotates a slide with the surface of the slide perpendicular to the axis of rotation, a drive circuit for the centrifuge that controls the rotation time of the centrifuge, and a scale as a function of the concentration of red blood cells in the blood. A device for preparing a blood film on a microscope slide, comprising a variable control of said drive circuit for regulating said rotation time, which is manually adjustable using a graduated scale. 2. A centrifuge that rotates the slide with the surface of the slide perpendicular to the axis of rotation, a centrifuge drive circuit that controls the rotation time of the centrifuge, and a scale that is graduated as a function of the red blood cell concentration of the blood. a variable control device of the drive circuit for adjusting the rotation time, which can be manually adjusted; blood on a microscope slide, comprising: a device for sensing the back emf of a motor and driving the motor at a controlled rotational speed; and a device for applying a reverse polarity current to said motor to stop the motor for a short period of time. A device that adjusts the membrane.