Abstract
A coupling liquid for ultrasound devices, preferably high intensity focused ultrasound (HIFU). The coupling liquid comprises a liquid aqueous solution of at least one hydrophilic polymer having an average molecular mass of between 30,000 and 70,000 and at least one alcohol with a carbon chain of 1 to 7 carbon atoms. Also disclosed is a container (10) for an ultrasound coupling liquid having a thin wall.
Claims
1. An ultrasound coupling liquid comprising: a liquid aqueous solution of at least one hydrophilic polymer, wherein the hydrophilic polymer is or comprises polyvinylpyrrolidone having an average molecular mass of between 30,000 and 70,000; and at least one alcohol with a carbon chain of 1 to 7 carbon atoms for reducing reflection of ultrasound waves at the boundary between the coupling liquid and at least one of skin and a cover member covering an ultrasound transducer, wherein the at least one alcohol is present in a concentration of 5% to 20% by weight, and the coupling liquid has a viscosity between 1.Math.10.sup.−4 Pa.Math.s and 2.Math.10.sup.−4 Pa.Math.s at 20° C.
2. The ultrasound coupling liquid as claimed in claim 1, wherein the at least one alcohol is selected from a group consisting of ethanol, propanol isopropanol, benzyl alcohol.
Description
(1) Additional aspects and details of the present invention will be apparent from the following description of figures and examples.
(2) FIG. 1: Diagram showing the difference in speed of sound in a coupling liquid with alcohol compared to a coupling liquid without alcohol;
(3) FIG. 2: An exploded view of an embodiment of a coupling liquid container according to the present invention;
(4) FIGS. 3a, 3b and 3c: The coupling liquid container of FIG. 2 viewed from different sides;
(5) FIG. 4: Schematic representation of a preferred method of manufacturing of a coupling liquid according to the present invention;
(6) FIGS. 5a and 5b: Fixation means for fixing a container of the present invention to an ultrasound device;
(7) FIG. 6: An ultrasound device comprising connection and cooling means for a container according to the present invention.
(8) FIG. 1 shows the difference in the speed of sound at various temperatures between a coupling liquid comprising 10% w/v of polyvinylpyrrolidone in water, shown as line B, compared to a coupling liquid additionally comprising 5% by weight of ethanol, shown as line A. As can readily be seen, the addition of alcohol increases the speed of sound in the coupling medium.
(9) Additionally, the reflection coefficient of the ultrasound waves between the liquid and the skin or cover member decreases, thus allowing increased transmission of the sound waves from the liquid into the tissues of a patient. Exemplary values for different physical characteristics of a coupling liquid of the present invention compared to a coupling liquid without alcohol and with plain water are shown in table 1:
(10) TABLE-US-00001 TABLE 1 Coupling liquid Water Coupling liquid with 5% ethanol Density ρ 1 1.006 0.9935 [g/cm3] Impedance Z 1,457 1,465 1,482 [MRay] Reflection 12 * 10.sup.−4 9.85 * 10.sup.−4 6.64 * 10.sup.−4 coefficient R of sound on cover member made of silicon
(11) The development of bacterial contamination was tested both for a coupling medium comprising 10% weight by volume polyvinylpyrrolidone in water as well as a coupling liquid additionally comprising 5% by weight of ethanol. Further, a coupling liquid comprising alcohol was inoculated with a bacterial culture of Pseudomonas aeruginosa at 80 CFU/100 mL. The coupling liquid probes were filled in a pouch container excluding any air and the pouches were stored for 5 months at room temperature. Samples of the liquid were taken and incubated for 3 days at 22° C.±2° C. After this time, bacterial contamination was determined. The results are shown on table 2:
(12) TABLE-US-00002 TABLE 2 Contamination Contamination Container Ethanol Innoculation after 1.5 mts after 5 mts 1 — — overgrown 500000 UFC/mL 2 — — overgrown 740000 UFC/mL 3 — — overgrown 570000 UFC/mL A 5% — 1 CFU/100 mL 0 CFU/100 mL B 5% — 0 CFU/100 mL 0 CFU/100 mL C 5% — 0 CFU/100 mL 0 CFU/100 mL D 5% 80 CFU/ 34 CFU/100 mL 0 CFU/100 mL 100 mL E 5% 80 CFU/ 40 CFU/100 mL 0 CFU/100 mL 100 mL F 5% 80 CFU/ 58 CFU/100 mL 0 CFU/100 mL 100 mL
(13) As can be seen, addition of an alcohol with a carbon chain of 1 to 7 carbon atoms, in this case ethanol, hinders bacterial growth in a coupling liquid. Even if the coupling liquid was not manufactured under aseptic conditions and therefore contains low levels of bacterial contamination, overgrowing of the liquid by bacteria can be avoided by addition of ethanol.
(14) In a test, the focal point of an imaging transducer was shifted from 11 mm to 13.7 mm from the tip of the probe using a coupling liquid with 5% ethanol.
(15) FIG. 2 shows an exemplary embodiment of a container of the present invention in exploded view. The container 10 comprises a first frame element 1 and a second frame element 2. In this embodiment, the frame elements 1,2 are generally of rectangular shape. On both sides of the frame elements 1,2 two wall elements 3,4 are affixed. Preferably, the frame elements 1,2 provide passages 11 for the insertion of tubes 5,6 into the cavity formed between the two walls 3,4. Identification means 7, exemplarily shown as RFID chip, may be inserted between the two frame elements 1,2. Between the walls 12 a cavity is formed.
(16) FIG. 3a shows a top view of an assembled container 10. Both wall elements 3,4 are fixed on the frame elements 1,2. This creates a border 8 at the edges of the wall elements 3,4. Wall elements 3,4 may be affixed to frame elements 1,2 by means of gluing or plastic welding. Frame elements 1,2 are also fixed together by means of gluing or plastic welding. Between the wall elements 3,4 cavity 9 is formed. Tubes 5,6 are inserted into cavity 9 through passages 11. By means of the tubes 5,6 the container 10 may be connected to an ultrasound device or to a liquid circuit of an ultrasound device.
(17) FIGS. 3b and 3c are side and front views, respectively, of the assembled container 10 as shown on FIG. 3a. Both wall elements 3,4 have a height H.sub.w. The overall height H of the container 10 is the sum of the height H.sub.w of the two wall elements 3,4 and the thickness of both frame elements 1,2. The height H.sub.w of the wall elements 3,4 is a maximal height. If the walls 12 are flexible and the cavity 9 is not completely filled, then the walls 12 may not extend to their full height H.sub.w.
(18) Both the frame elements 1,2 and the wall elements 3,4 are made of a polymeric material, preferably poly(vinyl chloride). Alternative embodiments may also provide for a container where the frame elements 1,2 comprise or are made of another material than the wall elements 3,4.
(19) The thickness of the wall elements 3,4 and hence of the walls 12 preferably is 0.1 mm. The frame elements 1,2 are preferably thicker than the wall elements 3,4. Preferably, thickness of the frame elements 1,2 is between 0.1 mm an 1.5 mm, more preferably between 0.2 mm and 1 mm. Most preferably, the frame elements 1,2 are 0.25 mm thick.
(20) The cavity 9 preferably has a with W.sub.c in the range of 90 mm to 150 mm, more preferably of 100 mm to 125 mm. Most preferably width W.sub.c is 110 mm. The length L.sub.c of cavity 9 is in the range of 180 mm to 250 mm, more preferably of 200 mm to 225 mm. Most preferably, the length L.sub.c is 210 mm.
(21) The with of the container W is preferably in the range of 120 mm to 180 mm, more preferably of 140 mm to 160 mm. Most preferably width W is 150 mm. The length of the container L preferably is in the range of 250 mm to 350 mm, more preferably of 280 mm to 320 mm. Most preferably, length L is 295 mm.
(22) Height H.sub.w of the wall elements 3,4 preferably is in the range of 5 mm to 20 mm, more preferably of between 10 mm to 15 mm, most preferably height H.sub.w is 12 mm.
(23) The height H.sub.w of the container 10 when filled is preferably in the range of 12 mm to 50 mm, more preferably of between 20 mm and 35 mm, most preferably the height H of container 10 is 22 mm.
(24) The total volume of the cavity 9 of container 10 most preferably is 500 mL.
(25) FIG. 4 shows a preferred method of manufacturing of a coupling liquid according to the present invention. In a first mixing step 19, an alcohol 15 is added to a powder of a hydrophilic polymer 16. Preferably, alcohol 15 is ethanol and polymer 16 is polyvinylpyrrolidone. The amount used may vary depending on the wanted characteristics of the coupling liquid. Preferably, 10 grams of a polyvinylpyrrolidone, preferably with an average molecular weight of about 58,000, e.g. as available under the name PLASDONE K29-32 (ISP Corp.), are dissolved in 50 grams of ethanol in the first mixing step 19. This solution is then mixed with water, preferably purified or distilled water in a second mixing step 20. The amount of water should be chosen such as to yield 1 liter of coupling liquid 18. Alternatively, additional compounds may be added to the coupling liquid 18 during any of the manufacturing steps, e.g. in first mixing step 19. Exemplarily, 1 ml of a 0.2% solution of a dye, preferably methylene blue, may be added. Depending on the desired characteristics of the coupling liquid 18, any suitable compound may be additionally added to the coupling liquid 18.
(26) FIGS. 5a and 5b exemplarily show fixation means to fix a container 10 to an ultrasound device. The fixation means preferably are in the form of an adaptor element 20 having a base member 22 and a lid member 21 which is pivotably coupled to the base member 22. FIG. 5a shows the adaptor member 20 in an open state. The base member 22 is configured such that a container 10 may be inserted between the outer walls of the member. For ease of handling, the adaptor member 20 may further comprise a handle 24. Additionally, the base member 22 comprises at least one fixation means 23 to reversibly secure lid member 21 to base member 22 in a closed state. Such a closed state is shown in FIG. 5b. By pivoting lid member 21 back onto the base member 22, the container 10 is securely connected in the adaptor member 20, preferably through clamping of the border 8 of the container 10 between the lid member 21 and the base member 22. The lid member 21 is secured to the base member 22 by means of fixation means 23. The fixation means 23 may be of any suitable form and configuration, such as screws, pins or a form fit connection. Both the base member 22 and the lid member 21 are configured in such a way as to allow connection means, here shown as tubes 5,6, to be freely connected e.g. to a probe head.
(27) FIG. 6 is a representation of an ultrasound device 25 comprising cooling and/or connection means for the container 10. In this example, the cooling means are provided within the ultrasound device 25. Adaptor member 20 with a container 10 mounted therein is inserted in a receptacle 30 provided on the ultrasound device 25. The cooling means are arranged in such a way as to provide optimal cooling of the container 10 once inserted in the receptacle 30. The ultrasound device 25 preferably further comprises an ultrasound probe head 26, a pivot arm 27 as well as input/output means, such as screen 28. Most preferably, the ultrasound probe head is covered by a cover member 29. In a special embodiment, container 10 and cover member 29 are comprised in a kit. Cover member 29 and the container 10 may then be brought in fluid connection by means of tubes or the like. Further, the ultrasound device may comprise at least one pump to allow cycling of the coupling liquid between the container 10 and the cover member 29.
