Drug infusion device with tissue identification using pressure sensing

[0001] The present invention relates generally to improvements in drug delivery, especially to subcutaneous injection / aspiration systems. More specifically, the invention relates to a method and apparatus for identifying specific types of tissues (or different soft tissue densities) based on the use of pressure measurement.

b. Description of the Related Art [0002] Devices and systems with infusion pumps are well known in the medical field when used to administer or dose a prescribed drug to a patient. Management of prescribed drugs has been described in the literature as interacting with a patient via infusion ducts with a catheter connected or similar device, as a result of which the drug is injected intravenously. These systems are usually capable of determining the extent of infusion line occlusion. Line occlusion increases the pressure in the syringe. The prior art systems have been developed to identify the achievement of a predetermined threshold value or monitor pressure in order to determine the means for selecting occlusion pressure ranges to ensure patient safety. U.S. Patent Documents No. 5,295,967; 4,731,058 and 5,080, 653 show systems (with syringe pumps or the like) that are suitable for their intended intravenous drug delivery, and more specifically for monitoring occlusion during infusion. However, these systems do not provide means for subcutaneous aspiration or drug delivery using hypodermic needles.

[0003] The accurate placement of a needle with a through-hole in the tissues for drug delivery into tissue structures has long been a major challenge in both medicine and dentistry. The inability to accurately position a needle with a through hole in certain tissues (i.e. soft tissues) or organs may result in the goal of treatment not being achieved. Localization of pathological tissues (e.g. cancer, tumors, cysts and the like) is critical for the aspiration of these tissues, as well as for the infusion of drugs for local therapy of these lesions in the body. For this reason, anatomically appropriate places have been located so far by means of ionizing radiation, ultrasound, magnetic resonance imaging, electrical stimulators and other invasive diagnostic devices that require

- 2 use of secondary techniques to help determine the accuracy of needle placement in tissue.

[0004] For a long time, pain, tissue damage and post-surgery complications have been tolerated as adverse side effects from the use of subcutaneous drug injection systems. This fact has been well documented in the dental and medical literature. Pain and tissue damage are a direct result of the uncontrolled flow rate combined with the excessive pressure generated during the administration of drug solutions into the tissue spaces. The patient's subjective pain response has been shown to be minimized at certain flow rates during drug administration. In addition, it has been scientifically proven that certain pressures (excessive as such without occlusion) cause tissue damage of a particular type. However, the present inventor has discovered that the severity of pain experienced by a patient can be minimized by using a specific range of flow rates in combination with a specific range of output pressure when administering fluids (drugs). In addition, when drugs are administered within the prescribed low pressure ranges and fluid flow rates, tissue damage is also minimized. It is also necessary for this system to be able to aspirate under controlled conditions of speed and pressure to prevent the same negative side effects during fluid movement. U.S. Patent No. 5,180, 371, Spinello discloses an invention for determining the rate of drug flow when administered through a hypodermic needle. However, this invention did not disclose means for determining, detecting or monitoring pressure during drug administration. US Patent No. 6,113,574 Spinello discloses an injection device that utilizes a pressure sensor switch to determine if fluid is injected into the right place during PDL injection or leaking into the patient's mouth or other location. However, according to this patent, the problem of identifying the tissue being injected is not addressed.

[0005] In the early 1980s, several researchers (see, for example, Rood, The Pressure Created by Inferior Alveolar Injections, British Dental J. 144: 280-282 (1978); Walton and Abbot, Periodontal Ligament Injection; a Clinical Evaluation JADA. (October 1981); Smith and Walton, Periodontal Ligament Injection; Distribution of Injected Solution Oral Surg 55: 232-238 (1983)) clearly demonstrated and stated that the pressure generated by the injected fluid is critical to preventing tissue damage and the onset of a pain response. Different types of collagen and different connective tissue densities lead to variations in tissue expansion and their susceptibility to injection. This type of variation is observed both among patients and in individual patients. In an article published in 1978, Rood states that "the relationship between the injection rate and the increase in pressure, clearly visible in smaller volumes, disappeared with the injection of 2.0 ml. In several cases high pressure values ​​have been reported; in a few cases unexpectedly low values ​​were also noted. Many of the obtained graphs of dependence were characterized by a characteristic course for tissue disruption and it is possible that the mentioned low pressures were caused by the spread of fluid outside the wing-mandibular space,

- 3 because the injected volumes were similar to previously estimated tissue space volumes. " Therefore, there seems to be no direct relationship between flow rate and pressure during interstitial injection.

[0006] Smith and Walton described in the article mentioned above their histological examination of animal (canine) tissues using the pressure calibration technique exerted by manual injections. They concluded that "injected volume and needle placement were not always associated with distribution. Injection of dye under moderate or strong back pressure resulted in deeper and more extensive penetration of the tissue. " This observation is another confirmation of the fact that the pressure value is a critical variable for the distribution of the solution in tissues, and the volume of distribution is not always related to the pressure generated.

[0007] Pashley, Nelson and Pashley in the article "Pressures Created by Dental Injections" (J Dent Res 1981) described the use of a pressure transducer and a constant flow rate of fluid pumped through a classic motor-driven syringe and clearly demonstrated that different tissues have different susceptibility Interstitial pressure variability was characterized by statistical and clinical significance even at established flow rates. Thus, it can be concluded that large pressure changes are generated using the measured flow rate.

[0008] Pertot and Dejou in the article "Effects of the force developed during periodontal ligament injections in dogs" (Oral Surg. Oral Med, Oral Pathol. 1992) described the use of a syringe coupled with a miniature force transducer and observed a positive correlation between osteoclast number and strength exerted on the syringe plunger, indicating that the build-up of tissue pressure in PDL increases osteoclast activity. This experiment again indicates that pressure is a critical factor responsible for tissue damage and depends on the resistance encountered and not on the flow rate of the solution into the tissue.

[0009] Previous documents are known in which attempts have been made to use pressure transducers for measuring pressure in a syringe (see, for example, US Patent No. 5,295,967). A major drawback of these systems is the inability to adjust the flow rate and / or fluid pressure to compensate for changes in resistance throughout the system or changes in output pressure. (Output pressure means the fluid pressure in the patient's body just below the tip of the needle.) In addition, the works included in the current state of knowledge do not provide any means to determine this output pressure.

[0010] US Patent No. 6,200,289 shows an automatic injection device consisting of a drive mechanism for causing the flow of therapeutic fluid from a cassette placed in a housing through a conduit and an injection needle handle. The drive mechanism is connected to the electric motor and the sensor connected at the motor output measures the force exerted by the motor on the drive mechanism. This force is then used to determine the internal properties of the system, e.g. force or pressure

- 4 internal exerted during injection. These properties are then used as control parameters of the microprocessor or control device issuing appropriate commands for the drive mechanism. In a particularly preferred embodiment of the invention, these properties are used to calculate the output pressure at which fluid is discharged from the syringe through the elongated conduit. The operation of the electric motor is managed in such a way as to maintain the output pressure at a predetermined level to ensure that the patient will not suffer from pain and / or tissue damage.

[0011] US 6,171,276 describes an automatic feeding device and how it works. This device has been described as being particularly suitable for administering preparations to the appropriate target tissue.

Summary of the Invention [0012] The present invention relates to a device enabling a practitioner to simultaneously use the diagnostic and therapeutic function. This device uses internal tissue density, i.e. resistance to fluid pressure in tissue, to determine the accuracy of needle location in specific tissue. Each tissue has its own pressure density characteristics, expressed as measurable pressure values ​​that can be generated in a given tissue. Density or tissue resistance is measured by the pressure / pressure of the fluid infused through a computer-controlled drug delivery system capable of detecting pressure resistance during the infusion. The measured pressure resistance is continuously converted into a visual and audible signal. The measurement results are presented to the doctor so that he / she can determine if the injection is done in the right tissue. Measurement results are also recorded for later analysis and for documentation of clinical events. It is possible to predefine upper pressure limits and to control flow rates to ensure that excessive pressure and / or flow rates are not used in the injection process.

[0013] Accordingly, the invention relates to the device according to claim 1. Preferred embodiments of the invention are detailed in the respective dependent claims.

[0014] The present invention also relates to alternative methods for determining the pressure or pressure in an automatic injection device. In one embodiment of the invention, the parameter indicating the magnitude of the pressure force is the electric energy or power consumed by the motor. In another embodiment of the invention, the dimension values ​​of the various elements of the fluid delivery system are used as parameters. This dimensional change is then converted into a signal indicating the amount of pressure / internal pressure. For example, components subject to dimensional changes due to external forces or pressures include the cassette or reservoir housing, including housing wings, cartridge supply hose from the cartridge, needle cap, and / or components. The sensor for determining this dimensional change may be, for example, an optical sensor.

[0015] A third method is to determine the force or tension of the motor housing and / or auxiliary drive elements. The measurement can be made using a standard electronic strain gauge.

[0016] Briefly, the system of the invention for administering fluid by injecting it to a patient comprises a mechanical assembly and an electric control device. The mechanical assembly consists of a drive mechanism and a disposable part consisting of a fluid storage device, e.g. a syringe, a carpule, etc., and a fluid delivery section containing a conduit coupled to this fluid storage device and terminated with a needle adapted to enter the patient's tissue. The drive mechanism consists of a housing with a motor inside and a holder for mounting the fluid storage device on the housing. The fluid storage device is equipped with a reciprocating piston. The piston is moved by this engine through a permanent clutch. If a carpoule is used as the fluid storage device, the kit also includes a connector for attaching the carpoule to the same holder. The design and construction of the holder allows the immobilization of syringes or carpules of various dimensions.

[0017] A transducer is used to sense the force or pressure exerted by the engine and transmitted by the pressure of the piston in the fluid storage device. In one aspect of the present invention, the transducer measures the force between the carpoule connector and the rest of the device housing. In another aspect of the invention, the transducer is equipped with a dimension recording device sensing a change in the dimensions of the device element, which change indicates the value of the drug's strength or internal pressure in the system, and output pressure. For example, an indicator of this force or pressure can be a change in the dimensions of the duct. In another embodiment of the invention, external pressure measurements in the line are used to determine the output pressure.

[0018] The engine, motor-related clutch and electronic control device are at least partially housed in a housing for protection.

[0019] The fluid storage device is filled and then the preparation process begins, in which various parameters of the device's operation are calculated, measured or obtained from the clinician. The clinic doctor also determines the fluid flow rates, peak output pressure, and total fluid to be administered. The clinician then turns the fluid flow on using a pneumatic regulator, such as a pedal. The clinic's doctor may also issue orders via electronic system or voice. During fluid delivery, the current fluid output pressure is calculated based on the transducer output signal. If the exit pressure approaches a certain threshold, the fluid flow rate will be immediately reduced to prevent excessive exit pressure, thereby ensuring that the patient does not experience excessive pain and that no tissue damage occurs. The system can also be equipped with optional functions, including the function of aspiration, purge or loading of substances with or without air.

[0020] Alternatively, the system may operate in a biopsy sampling mode, in which the appropriate control parameters are the inlet pressure and the flow rate of the fluid being withdrawn or flowing.

[0021] Throughout the duration of the procedure, the clinician receives continuously, through visual and auditory signals, current information about the process, including current flow rate, total volume of fluid pumped or drawn, output or input pressure, and other parameters. The slave microprocessor receives commands from the main microprocessor and generates drive signals controlling the operation of the motor.

Short description of the drawing [0022]

Fig. 1 is a diagram illustrating the main components of a drug infusion device according to the invention.

Fig. 2 is an orthogonal view of the drive mechanism of Fig. 1.

Fig. 3 shows the interior details of the drive mechanism shown in Fig. 1.

Fig. 3A is a block diagram of the electronic control device of Fig. 1

Figure 4 is a side view of the housing of another type of drug infusion device with a pressure sensing connector.

Figure 5 is a rear view of the housing of figure 4.

Fig. 6 is an enlarged view of the connector of Fig. 4.

Fig. 7 is a partial schematic cross-sectional view of the housing of Fig. 4.

Fig. 8 shows an alternative embodiment of a pressure gauge based on the dimensions of the duct.

Fig. 9 shows yet another embodiment of a pressure gauge based on the dimensions of the duct.

Figure 10 is a graph of typical pressure ranges for ranges of up to four tissue types.

Detailed description of the invention [0023] The present invention relates to a system for pressure administration of drugs, for example anesthetics, into the tissues of a patient. Importantly, due to a variety of factors, the injected fluid is distributed in tissues at different rates, which leads to differences in fluid output pressure values. The inventor discovered that this

- the value of the output pressure (or internal pressure associated with the output pressure) can be significant for the tissue and thus can be used to identify several types of tissue.

[0024] The mechanical assembly of the present system is shown in Figs. 1 and 2, and the electronic system control device 150 is shown in Fig. 3.

[0025] The drug delivery system 10 constructed according to the invention has a drive mechanism 12, a delivery tube 14 and a handle 16 with a needle 17. More specifically, a syringe 90 (or other fluid storage device) is mounted on the drive mechanism such that one end of the tube 14 it is connected to the syringe 90. The drive mechanism 12 acts on the piston 94 to selectively pump fluid through the conduit 14, handle 16 and needle 17, or alternatively to aspirate the fluid. The drive mechanism 12 is connected to an external control device for selecting various operating parameters, discussed in more detail below. This external control device may be mounted in the housing of the drive mechanism or be provided as a separate control unit 18 connected to the drive mechanism 12 by cable 20. The control unit may be a desktop PC or notebook. Alternatively, the control unit 18 may be an indoor unit.

[0026] Details of the drive mechanism 12 are shown in Figure 2. The drive mechanism 12 has a housing 22 with an upper surface 24 and an intermediate surface 26 located below the upper surface 24. On surface 26 a rail 28 is formed extending along the longitudinal axis of the housing 22. Platform 30 positioned on rail 28, it can slide back and forth parallel to the longitudinal axis as detailed below.

[0027] The upper surface 24 has a clamp 40. The clamp 40 has a general C-shape. A head screw 48 passes through the threaded hole (not shown) in the clamp 40. The platform 30 has a socket 56.

[0028] Inside the housing 22 there is a motor 66 (Fig. 3). The worm screw 72 passes through the motor 66. The worm screw 72 is positioned so that when the motor 66 is turned on, it can move in one direction or the other, depending on the direction of rotation, parallel to the longitudinal axis of the housing 22. One of the ends of the worm screw 72 is attached is in a non-rotating penholder 74 connected to platform 76. In order to prevent the transmission of rotational forces generated by the motor 66 to the platform 76, the holder 74 is connected to the platform 76 using two short rods 80.

[0029] Between the platforms 30 and 76 extend two columns or rods 82, 84 connecting both platforms. These rods are supported by the sliding fasteners sleeve 68, 70 in housing 22. With the exception of these sleeve fasteners, platforms 76 and 30 are freely embedded inside and outside the housing 22. Rods 82, 84 pass through holes (not shown) in the wall 86 connecting surfaces 24 and

26. The rail 28 is hollow and laid over the worm screw 72, allowing the worm screw 72 to move along its axis through the housing 22.

[0030] Typically, the syringe barrel 92 is on the surface 24. The finger wings on the barrel 92 rest in the gap on the surface 24. The wings and gap are not included in the drawing for the sake of clarity. The syringe 90 is also equipped with a piston 94 moved forwards and backwards inside the cylinder 92 through the shaft 93. The shaft is terminated with a finger pad resting in the seat 56 on platform 30. The syringe 90 is attached to the housing 22 by means of a clamp 40 and a screw 48. The syringe is terminated with a Luer 95 tip intended for connecting the syringe to the conduit 14.

[0031] When turned on, the motor 66 causes the worm screw 72 to move in one direction or the other, as described below. The worm screw 30, in turn, causes the platforms 30 and 76 and the rods 82 and 84 to move in unison, which leads to the piston 94 moving in the cylinder 92. The only elements moving in and out of the housing are the rods 82, 84. Thanks to this, most critical elements system is protected against manipulation or leakage of liquids inside the housing. The mechanism 12 is further adapted for mounting and working with syringes of various diameters and lengths. Also, the delivery tube 14, handle 16 and needle 17 can have any desired size. For more details on the syringe and motor drive, worm screw and its connection to platform 30, see US Patent No. 6,200,289. The patent further describes a load cell 78 located between the platform 76 and the cap 74 to transfer and measure force between the mount 74 and the platform 76. This load cell is a two-way cell for measuring both pressure and stress, depending on whether the worm screw 72 moves to the left or to the right, as in Fig. 3. In the present invention, other means to replace this load cell are disclosed.

[0032] In one embodiment of the invention, the device is equipped with a pair of pressure sensors 78A placed between the finger pad 96 and the walls of the socket 56. The sensors 78A are arranged to measure the force exerted between the platform 30 and the pad 96.

[0033] In another embodiment of the invention, the sensors 78B are located between the sleeve attachments 68 and the side walls of the housing 22. In this way, the sensors 78B can measure the pressure (or stress) exerted by the motor on the syringe plunger 94. Alternatively, it is possible to arrange a similar link the load cell between the wings of the syringe barrel and the housing 22. The sensors can be load cells, for example Model S400 load cells, manufactured by SMD, Inc. in Meridien, Connecticut.

[0034] In yet another embodiment of the invention, shown in Figure 1, the conduit 14 passes through an opening in the 54 meter. The conduit 14 expands under pressure, so the dimension of the conduit is a reflection of the pressure exerted on the conduit by the piston. The 54 dimension meter monitors the dimensions of the cable 14 (e.g., its cross-sectional dimension or diameter) and gives the measured value as a parameter to the main control device 18. The meter 54 may for example consist of one or

- 9 more LEDs and matrix of photosensitive cells, with a wire placed between these elements. The dimension of the cable is determined by the number and / or location of the photosensitive cells covered by the cable.

[0035] Fig. 8 shows a cross-section of another 54A meter that can be used instead of 54. This meter consists of a base B with a slot S in which the T cable is located. The T cable is held in place by the hinged cover C A commercially available FS pressure sensor is inserted through the H opening and rests against the T line. As the line expands or narrows under pressure, it exerts pressure on the sensor. Experimental data indicate that this type of 54A meter is characterized by fairly good linearity of the output signal and is easy to calibrate for different pressures. [0036] Fig. 9 shows another 54B meter that can be used instead of the 54 meter. This meter is similar to the meter shown in Fig. 8, except that the cover C has a groove and the wire rests on the movable plane P located above the pressure sensor. The force exerted by the pressure in the conduit is transmitted through the movable platform P to the pressure sensor FS. Also in this case the meter response is linear and easy to calibrate.

[0037] Figure 3A is a block diagram of the electronic control device 150. Control device 150 includes two microprocessors: the main microprocessor 152 and the sub-processor 154. The sub-processor 154 is used to output signals used to control the motor 66 and collect information about the position of the platforms 30 and 76.

[0038] The main microprocessor 152 is used to collect information about the rest of the system, including the syringe 90 and its contents, cable 14, handle 16, etc., and to generate control signals for the sub-processor 154 required to control the motor 66 providing the content syringes 90.

[0039] The slave microprocessor and the associated circuitry are physically located inside the housing 22. The main microprocessor 152 is included in the control unit 18 connected to the housing 22 by cable 20, as shown in Fig. 1. The microprocessor 152 is connected to the memory 160, input devices 162, display devices 164 and connector 164.

[0040] Memory 160 is used to store programs and data for the main microprocessor 152. More specifically, the memory 160 is used to store six or more data banks, each of which is designed for one of the following categories of information: (a) syringes; (b) wires; c) needles; (d) liquids; (e) regulatory parameters; and (f) profiles consisting of numerous parameters required to perform a particular procedure. Each of the above-mentioned parameters is used to determine the control signals generated for the subordinate microprocessor 154. Each of these databanks contains relevant parameters for various commercially available products or parametric data determined using a specific algorithm.

- 10 Information regarding the various components of a given configuration is entered using input devices 102 and confirmed on the display device 164. These input devices may include a keyboard, a touch screen, a mouse and a microphone. If a microphone is used, voice commands are interpreted by the 162A speech recognition circuit.

[0041] The display device 164 is further used to provide directions and instructions regarding the operation of the system 10. Commands for the operation of the motor 66 are generated in the main microprocessor 152 and transmitted to the connector 166. The microprocessor 152 is also equipped with a loudspeaker 165, used to provide voice messages, including pre-recorded or synthesized (generated in the 165A speech synthesis circuit) voice messages, ringtones, etc., providing instructions to the clinician and other information about the current state of the entire system and its items without having to constantly watch the display device.

[0042] Slave microprocessor 154 receives the above discussed commands via cable 20 or other type of connection, and via connector 170.

[0043] One or more position sensors 172 and the drive circuit with interrupter 174 are also connected to the slave microprocessor. As previously mentioned, the force or pressure generated in the system is measured by sensors 78A, 78B, 54, 54A, 54B.

[0044] Furthermore, a foot switch or pedal 176 is connected to the slave microprocessor. In a preferred embodiment of the invention, the pedal 176 consists of an air chamber with a flexible sidewall, said sidewall being arranged to vary the volume of air and pressure in this chamber in response to switching on by the operator. Part of the pedal is a pressure sensor (not shown) arranged to provide information about this pressure through the appropriate analog-to-digital converter to the slave microprocessor 154. Pedals of this type are well-known devices, therefore detailed information about them is omitted. these.

[0045] The sequence of operations in system 10 is similar to the sequences described in US Pat. No. 6,200,289 and its description will not be repeated here. In addition, the algorithm disclosed in this patent also applies to the processing of parameters obtained from sensors 78A, 78B or 54 into appropriate output pressure values.

[0046] In another embodiment of the invention, the power required to drive the motor 66 is monitored. For example, the main control device 150 may be equipped with a power meter P monitoring this power by, for example, measuring the voltage and current applied to it. The power in question corresponds, of course, to the force exerted by the engine; its value is used in the same way as the output values ​​of sensors 78A, 78B or 54.

[0047] Until now the subject system has been described as an injection system. However, it is obvious to a person skilled in the art that this arrangement can also be used

- effective when performing a biopsy, for example when performing a lumbar puncture or similar operation performed without air access. In the biopsy process, essentially the same parameters can be used, with minor modifications. For example, instead of determining the exit pressure, the clinician will determine the entry pressure.

[0048] In the embodiment of the invention discussed so far, it was assumed that the fluid was administered from the syringe 90, and therefore that the syringe 90 had to be filled with this fluid beforehand, either by the manufacturer or on site by the clinician or assistant before starting any actions. For many procedures, however, it is more desirable to provide the fluid to be administered in the form of a cassette. In US Pat. No. 6,152,734, co-owned by the applicant of the present invention, an injection device consisting of a housing and a motor-driven shaft is described. On the top of the housing is a container that can receive the cassette holder. An anesthetic drug cassette is placed in the cassette holder. The upper wall of the fitting has a connection with the near end of the cable. The distal end of the tube is used to administer the anesthetic. According to this invention, a sensor module has been added on top of the housing. As shown in Figs. 4, 5 and 6, the housing 300 includes an upper surface 302 and a front surface 304. On the front surface 304 there are a number of indicator diodes and one or more control buttons 308. According to the invention, on the top surface 302 is attached sensor module 310. Module 310 has its own top surface 312 and rear surface 314. On the front surface 314 there is a LCD 316 display.

[0049] On surface 312 there is a container 318 and an opening 320 of the same shape and size as the respective elements on top of the housing 300, shown and illustrated in US Patent No. 6,152,734. As shown in turn in Fig. 7, with module em 310, a cassette 322 connected to the near end of the 324 tube is connected. The distal end of the tube is connected to a syringe, catheter or similar injection device (not shown). When not in use, this injection device can be stored in the opening 320. The underside 326 of the cassette holder 322 is shaped to allow quick and easy insertion into the container 312 with an interference fit. According to US Pat. No. 6,152,734, it is preferable to connect the underside of the housing 328 and the container 318 by means of a quick coupling so that the cartridge can be quickly and easily installed in the container and removed from the container. The cassette holder is used to hold a cassette (not shown) with an anesthetic or other medicinal substance.

[0050] It is important according to this invention that one or more sensors 328 are located between the bottom part 326 of the cassette holder and the walls of the container 318. These sensors can be pressure sensors or similar sensors used to monitor the force exerted on the fluid extruded through the conduit 324 .

[0051] As described above, a piston 332 is disposed on the housing 300. The module 312 optionally includes a piston sensor 330 located in the direct

- 12 near piston 332 or in contact with it. As the piston moves upwards, its end enters the cassette located in the cassette holder 322 and causes the contents of the cassette to be pressed through the conduit 324. The downward movement of the piston 322 causes suction. The piston sensor 330 measures the direction and conveniently the movement speed of the piston 322.

[0052] This piston 332 is reciprocally moved vertically by a motor 334. The motor 334 is controlled by a control device 336. Sensors 328 and 330 are connected to a connector 338. This connector sends information from sensors 348, 330 to control device 336. The control device then directs the engine to cause the piston 332 to move in the same manner and according to the same algorithm as for piston 94 in FIGS. 1-4. Information regarding this operation, as well as any other information, is displayed on a 316 display.

[0053] In the arrangement shown, the sensors can also be used to detect basic types of operations, e.g. purge or automatic piston retraction. When inserting the cassette holder into the socket in the drive unit, pressure sensors detect the placement of the holder and then automatically blow air out of the pipes, preparing the system for operation. When removing the cassette from the unit, pressure sensors can detect the removal of the housing and allow the piston to automatically withdraw to its starting position. So pressure sensors are multifunctional components that detect output pressure and basic drive unit operations.

[0054] It is important that pressure can also be used as a criterion in determining the tissue into which the device injects fluid. Earlier mentioned authors investigated the clinical effect of interstitial pressure during dental injections. The inventor has carried out studies showing that using the device described herein, it is possible to accurately measure and record subcutaneous interstitial pressure in real time. It has also been found that a specific range of pressures measured with the device can be easily identified and associated with a particular type of tissue. Correlations of interstitial pressures with tissue densities were made at specific anatomical locations.

[0055] Highly organized, densely packed collagen fibers, for example those found in some oral tissues such as the ligaments near the teeth or hard palate, reduce the possibility of diffusion of injected fluids, which means that these fluids remain limited in smaller volumes. The reduced ability of denser tissues to allow rapid drug redistribution results in higher internal pressure values ​​during injection. In turn, loosely organized tissues with a connective tissue framework composed of a collagen matrix filled with interstitial fluid and adipose tissue, for example, the tissues of the buccal fold or the subcutaneous fossa lead to the formation of lower internal pressures due to the spread of the drug to a larger area of ​​the tissue.

[0056] Based on this observation, it has been concluded that there is a correlation between the density of a given type of tissue and the injection process. More specifically, studies have been performed using the following injection groups.

Group 1 - ligament injections (PDL) (also injections into the ligament at the teeth), Group 2 injections into the anterior, medial, upper areas of the gums and palate s (PI), Group 3 - infiltration injections above the periosteal cheek (SBI) and Group 4 - lower gum block (IANB). Fig. 10 shows the different pressures obtained for the respective injections. The graph clearly illustrates the concept of using pressure values ​​(in a preferred embodiment of output pressure) to identify tissues.

[0057] In general, the following tissue types can be distinguished:

Type 1 - Low density tissues, composed of a loosely organized connective tissue matrix filled with adipose tissue, intercellular fluid and a small volume of organized collagen fibers. Examples of this type of tissue are subcutaneous connective tissues of the maxillofacial mucosa and subcutaneous pit. Examples of injections into this type of tissue are infiltration cheek injections and lower gum nerve block.

Type 2 - moderate density tissues, composed of densely packed collagen fiber bundles and a small amount of glandular and / or adipose tissue. There is a relatively small amount of intercellular fluid in this type of tissue. Moderate density tissues are also represented by muscular tissues within the mouth. Moderate collagen organization is found in this type of tissue. Tissues of this type include keratinizing gingival palate tissue, keratinizing gingival tissue or muscular tissue within the mouth. Examples of injections into this type of tissue are palate injections or injections into keratinized gingival tissue.

Type 3 - High density tissues, mainly composed of dense matrices of highly organized collagen fibers. Examples of this type of tissue are ligament at the teeth and muscle tendon trailers; an exemplary type of injection into this type of tissue is injection

PDL.

[0058] In addition, the scope of application of these techniques can be extended to identify mineralized and non-mineralized tissues, as well as fluids, according to the following classification:

Non-mineralized tissues:

Soft tissues, connective tissues, dermis (skin)

Ligaments

Fat tissues (fat)

muscles

tendons

Brain tissues

- 14 dishes

Mineralized tissues:

Cortical bone tissue. Marrow bone tissue. Cartilage tissue

In order to

Tumor tissues:

Hard and soft changes

Fluid filled changes:

hematomas

cysts

Fluids: Extracellular and intracellular fluids. Joint fluid in joint capsules Intracranial fluid

Cerebrospinal fluid Lymph [0059] As described above, the injection device continuously monitors the pressure and preferably the fluid output pressure during injection. Based on the tables stored in memory, the device is able to determine the type of tissue in which injection occurs. This information is transmitted on the display to the doctor (or other clinic employee). The doctor can then confirm that the injection is performed in the correct tissues. In addition, pre-set maximum allowable pressure and / or flow rates are set for each type of tissue, which specify either the maximum recommended pressures that are usually tolerated by patients or other criteria. These parameters are stored in memory 160. When the pressure approaches this limit, a visual and / or audible alarm is generated for the clinic employee. In addition, data describing the entire injection process is stored for later analyzes, as discussed above.

[0060] The techniques described herein apply to both human and animal tissues.

[0061] Although the invention has been described with reference to several specific embodiments, it should be understood that these embodiments are merely illustrative of the principles of the invention. Accordingly, the embodiments described in detail are to be considered exemplary and not restrictive with respect to the following claims.

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