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PubMed2003

44-MHz LiNbO3 transducers for UBM-guided Doppler ultrasound.

In the post genome-sequencing era, physiological phenotyping of genetically engineered mice is critical to further our understanding of the functional consequences of specific genetic defects. We have developed a 40-50 MHz ultrasound biomicroscopy-(UBM) guided, pulsed Doppler system for the sensitive detection of in vivo blood velocity waveforms in the mouse embryonic cardiovascular system. Our approach uses separate transducers for simultaneous imaging and Doppler blood flow measurements. To this end, unfocused, air-backed lithium niobate (LiNbO3) transducers provide sensitive Doppler detection and the flexibility of adjusting the axial position of the pulsed Doppler sample volume over many millimeters depth range of the collimated ultrasound beam. In this paper we describe the fabrication and characterization of the electromechanical and ultrasonic beam properties of 44-MHz LiNbO3 Doppler transducers. We further demonstrate the utility of these Doppler transducers for interrogating blood vessels such as the dorsal aorta over a range of mouse embryonic stages and axial range-gate depths.

Animals↗

PubMedDate not supplied

Effect of occlusal morphology on the accuracy of bite force measurements using thin film transducers.

PURPOSE: Occlusal transducer foils using piezoelectricity or pressure-dependent electric resistance are potential candidates for a measurement system for both absolute levels and changes in bite force. This preliminary in vitro study evaluated the possible usefulness of such transducer foils in the assessment of occlusal forces in centric occlusion. MATERIALS AND METHODS: Piezoelectric force transducer foils 33 microm thick were placed between pairs of teeth with the dentition in centric occlusion. Occlusal forces were recorded in five patients, who were instructed to bite as hard as possible for about 1 second. Acrylic resin casts of each pair of antagonistic teeth were aligned with the help of interocclusal records. The casts were mounted in a jig, where a defined load could be applied. The ratio of applied force and measured sensor signal permitted a set of calibration factors. RESULTS: A correction factor for each pair of teeth helped determine the ratio by which measured occlusal force exceeded actual tooth load. Differences in occlusal morphology gave rise to a wide span of correction factors (1.01 to 2.80). Steep cusp angles resulted in a wedge action that gave rise to a strong increase in occlusal forces, which were about twice as high as actual tooth load, with wide variation. CONCLUSION: This method of bite force measurement eliminated the influence of occlusal morphology by individual correction for each pair of opposing teeth. To measure the absolute load of antagonistic teeth with thin film transducer foils, one must take into account individual occlusal morphology. Forces measured with the films are a function of both actual tooth load and occlusal morphology.

Bite Force↗

PubMed2004

[Clotting induction in the mesenterium and erosive stomach mucosa in wistar rats as the result of a catenoidal ultrasonic transducer].

The ultrasonic transducers and instruments used in surgery operate in the range of 1-10 MHz and release significant heat in the surroundings. They need additional cooling system which significantly raises the cost and impedes the equipment operation. Hemostasis can be successfully achieved by employing ultrasonic transducers that operate in the kilohertz range, avoiding the occurrence of inadmissible tissue overheat outside the area of the transducer performance. The paper presents results of the approbation of the effect of a periodical acoustic signal with frequency of 60 kHz over the erosive stomach mucosa and mesenterium of 28 rats, "Wistar" breed, and the period of tissue exposure is 1-10 min. A transducer-catenoidal semi-wave concentrator that provides maximum emitted power of the ultrasonic wave is used and thermal effects are avoided. It is proved that the use of a powerful and localized ultrasonic signal results in erythrocyte diapedesis and forms microhaemorrhagies together with an out-vessel coagulation in the rat stomach mucosa The tissue damages are strictly limited within the area of the emitter contact and they are subject to control during the ultrasonic performance.

Animals↗

PubMed2005

Extramembranous placement of an air-coupled vs. transducer-tipped intrauterine pressure catheter.

OBJECTIVE: To compare the rate of extramembranous placement between 2 types of intrauterine pressure catheter. STUDY DESIGN: Women were randomized to a transducer-tipped intrauterine pressure catheter or an air-coupled intrauterine pressure catheter from October 1998 to August 1999. Women were eligible for the study if their attending physicians decided to place an intrauterine pressure catheter. Our primary outcome variable was extramembranous placement. The intrauterine pressure catheter was left in place during cesarean delivery, and the position was documented. RESULTS: A total of 257 women entered the trial. Eight were excluded due to removal of the catheter before cesarean delivery, leaving 249 evaluable patients. Of those 249, 105 (44.3%) received cesarean delivery, with 41 in the air-coupled group and 64 in the transducer-tipped group. There were no significant differences in maternal age, gestational age, gravidity, duration of membrane rupture, birth weight, pharmaceutical drug use, cocaine use, oxytocin use or catheter removal due to poor function. The transducer-tipped catheter was placed outside the membranes significantly more frequently than was the air-coupled catheter (12.5% vs. 2.4%, p = 0.02). CONCLUSION: Transducer-tipped catheters were significantly more likely to be placed in the extramembranous space than were air-coupled catheters.

Adult↗

PubMedDate not supplied

Development of an automatic control algorithm for the electrohydraulic total artificial heart without transducers.

To achieve a reliable and simple implantable total artificial heart, the number of implanted transducers providing the physiologic information required for automatic control should be minimized. To address this need, a new automatic control algorithm, based on a transducerless electrohydraulic total artificial heart (EHTAH) system, is proposed. The current EHTAH physiologic control algorithm relies on two implanted pressure transducers. Without these transducers, the information required for automatic control must be extracted from the running motor's parameters. These parameters correlated with the differential pressure across the axial flow pump used to actuate the EHTAH. Changes in this differential were chosen as a cue for cardiac output control. This algorithm can be viewed as depending upon systemic vascular resistance determined by subtracting mean right atrial pressure (RAP) from mean aortic pressure (AoP) and dividing the result by total cardiac output (CO). The difference between mean AoP and mean RAP was confirmed to correlate with the differential hydraulic pressure across the energy converter during the left systolic phase. As an interim configuration, a single differential pressure transducer measuring the differential hydraulic pressure across the energy converter was tested on a Donovan mock circulation system. The resultant CO response shows good sensitivity according to changes in both preload and afterload.

Algorithms↗

PubMed1991

Design of 20 MHz wideband piezoelectric transducers for close proximity imaging.

Quarter wave matching of ultrasonic transducers with two layers (glass and parylene) were studied with computer simulation. These layers are located between the piezoelectric transducer and the acoustic load. The purpose is to achieve a short impulse response and high efficiency broadband transfer in a practical manner for high frequency transducers. The acoustic impedances of these layers were chosen based on transmission line theory. A method to measure acoustic properties of the matching layers and a method to choose the material are discussed. The advantages in using a quarter wavelength of glass and parylene as the matching layers are given. The 6 dB fractional bandwidth of the simulated transmission-reception transfer was found to be 0.75, which is a factor of at least 6 improvement over a nonmatched transducer.

Computer Simulation↗

PubMed1985

Optimal siting of heat flux transducers for the assessment of body heat loss when immersed in water.

Regional heat flux (intensity of heat flow rate, W m-2) was measured using heat flux transducers affixed to the skin surface at 14 sites on the left arm and 15 sites on both the left leg and the trunk (total of 44 locations) of human subjects during head-out immersion in water at temperatures between 11 and 28 degrees C. The heat flux data and skin temperature data were collected continuously over a 30-min period taking approximately 2.5 min to scan through all transducers in sequence before repeating the process. There were 3 immersions per individual, monitoring the arm or the leg or the trunk. The local measurements of heat flux from each of the body segments were summated and meaned to obtain a value of overall flux for each area of the body for each 2- to 3-min interval. This mean value was taken as the optimal value (Hopt) for any particular body segment. Every permutation of the positions of any 1, 2, 3, 4, or 5 heat flux transducers from the possible 14 or 15 sites was used to obtain a mean value which could be compared to the Hopt over the total duration of each immersion. Comparisons could be made between the best individual sites (Iopt) and Hopt as well as between the overall best site for the group of 10 people (Gopt) and Hopt. All possible permutations could be ranked in ascending order of preference based on a decreasing sum of the squares of the differences between Hopt and either Iopt or Gopt. Confirmation of the validity of this simple ranking system was based on an analysis of the percentage differences between Iopt or Gopt and Hopt. Such an analysis indicated that the better choice of discs when using a small number of transducers was between 3 and 5 sites, affording both reasonable accuracy and practicality. It is recommended that between 3 and 5 discs be used per body segment at specific locations and the calculated heat loss from each segment be weighted according to its area of representation to give a value for the mean rate of total body heat loss. A reasonable level of accuracy was demonstrated using Gopt permutations for measuring both the rate of heat flow as well as the integral of the data to obtain a value of the quantity of heat (Joules) lost from the body.

Adult↗

PubMed1978

[Measuring intracranial pressure with a fontanelle palpation transducer (author's transl)].

The accuracy and reliability of a non-invasive method for the measurement of intracranial pressure through the fontanelle without puncture was tested during 12 or even 24 hours recordings. Wealthall and Smallwood modified aplanation transducer was first used. A metal frame had to be developed in order to secure the transducer rigidly over the fontanelle so that the recording could take place with the infant in any position and completely free of its movements. Simultaneous recordings of extradural or intraventricular pressure have shown the measurements were accurate to about 1 or 2 cm H2O in a neurosurgical environnement (i.e large fontanelles with pressure over 10 cm H2O). For smaller fontanelles or low or even negative intracranial pressure, a smaller transducer seems to be needed. The preliminary test of a plane strain gauge transducer that partially fills this need is shown.

Circadian Rhythm↗

PubMed1980

Capacitive blood pressure transducer.

A capacitive transducer was developed to measure blood pressure using a catheter interfaced to the body. The transducer was made of fused quartz in order to achieve a low temperature coefficient and it consists of a circular body and a 1.25 mm thick sensing diaphragm that mates concentrically with the body. The body of the transducer has a 10 micron deep circular cavity, plasma etched into it. One of the electrodes of the sensing capacitor is vacuum deposited in the etched cavity and the other, which is an oversized electrode, is similarly deposited on the underside of the diaphragm. To obtain a stable reference capacitor, a ring electrode is also deposited in the cavity that forms a capacitor with the oversized electrode. The diaphragm and body are brazed together using a tin-gold alloy. A typical transducer has a full scale of 300 mm of Hg with an overpressure capacity of 3000 mm; a TC sensitivity of 0.015% of FS/degrees C; a thermal zero drift of 0.01% of FS/degrees C; linearity and hysteresis of 0.5% of FS; a volume displacement of 0.02 mm3/100 mm Hg. The pressure module is 29.3 mm in diameter and 7.6 mm high.

Blood Pressure Determination↗

PubMedDate not supplied

Artifactually elevated basal uterine tonus resulting from measurement of hydrostatic pressure by transducer-tipped intrauterine catheters.

Accurate measurements of uterine activity are a valuable adjunct in the management of parturition. Recently transducer-tipped intrauterine pressure catheters (IUPC) have been advocated because of their accurate recording of uterine contraction pressures. We hypothesized that the transducer-tipped IUPC may record elevated basal uterine pressures because of measurement of additional hydrostatic pressures within the uterus. Eight laboring patients received intrauterine placement of a transducer-tipped IUPC. Catheters were zeroed to air pressure, electronic zero was checked, and monitors were calibrated before insertion. Catheters were not rezeroed during labor. Basal resting uterine pressures were recorded at insertion and before IUPC removal. After removal, electronic zero and catheter accuracy were tested in a specially designed pressure chamber (21 and 60 mm Hg). Electronic zero averaged -3 mm Hg before insertion and after removal. Baseline uterine resting tone averaged 15 +/- 1 mm Hg in seven patients, and one patient had a measurement of 34 mm Hg. Uterine resting tone remained stable in five patients and decreased to 20 mm Hg in the one patient with elevated basal tone. Uterine resting tone increased markedly to 36 and 41 mm Hg in two patients with normal pressures on insertion, in spite of no evidence of uterine hyperstimulation. Extrauterine pressure testing recorded pressures of 23 +/- 1 and 62 +/- 1 mm Hg, respectively. Because of the measurement of the amniotic fluid column above the catheter, transducer-tipped IUPCs may artifactually elevate uterine pressure measurements and basal levels may shift during the course of labor.(ABSTRACT TRUNCATED AT 250 WORDS)

Artifacts↗

PubMed1995

Placental abruption after insertion of catheter tip intrauterine pressure transducers: a report of four cases.

BACKGROUND: Although intrauterine pressure transducers have proven efficacious in the management of certain laboring women, their use has been associated with small but definite risks to both mother and fetus. The introduction of catheter tip pressure transducers has facilitated the evaluation of intrauterine pressure, but there has been a paucity of data regarding complication rates with these newer devices. CASES: We report four cases of placental abruption following insertion of catheter tip intrauterine pressure transducers. Two were associated with placental lacerations. None of these patients had definite risk factors for abruption, but they developed signs and symptoms typical of it after insertion of the catheters. Perinatal outcomes were good except in one neonate, who developed shock secondary to anemia. Three of the four cases occurred when 599 patients at our institution were monitored with catheter tip pressure transducers. CONCLUSION: Although the risk of injury is small, neonatal morbidity can be severe, and an evaluation of risk versus benefit should be made prior to insertion of these devices.

Abruptio Placentae↗

PubMedDate not supplied

[Inductance transducers for borderline localization of metallic foreign bodies].

The paper outlines the advantages and disadvantages of a ferroprobe inductance transducer used in the borderline localization of a foreign ferromagnetic body. To eliminate the ferroprobe transducer-inherent disadvantages, a whirl-current inductance transducer has been developed. The transducer localizes a foreign nonferromagnetic and ferromagnetic body in its borderline localization in the eye and in the whole body.

Eye Foreign Bodies↗

PubMed1997

Strain-gauge force transducer method for evaluating urethral motility in conscious dogs.

A new method has been developed that is suitable for physiological studies of urethral motility in the conscious state with a strain-gauge force transducer (force transducer). In anesthetized dogs, the contractile or relaxing responses of the urethral smooth muscle in the direction of the circular layers measured with the force transducer, elicited by either phenylephrine or isoproterenol, were significantly correlated to the increase or decrease in the intra-urethral pressure (r = 0.998 and 0.780, respectively). In conscious dogs, the fluctuation in the urethral tone was observed to be less than in the intra-urethral pressure, and a dose-dependent response to phenylephrine (1-30 micrograms./kg. i.v.) and isoproterenol (0.1-3 micrograms./kg. i.v.) was clearly recognized. Moreover, this conscious model provided a fairly reproducible pattern with the urethral contraction or relaxation related to the filling or voiding phase of the cystometrogram, which was abolished by anesthetization. These results indicate that the present force transducer method makes it possible to evaluate the further physiological characteristics of urethral motility in conscious dogs.

Animals↗

PubMedDate not supplied

Novel design of a regional myocardial force transducer.

A novel force transducer was designed to measure the circumferential regional force developed in the ventricular myocardium in vivo. The transducer is composed of a frame, a carrier bar, and a cantilever spring. Two resistance strain gauges embedded on the spring serve as force-sensing elements. The output of a Wheatstone-bridge circuit, containing these two gauges and a temperature compensation resistor, is connected to a preamplifier. The main advantages of this prototype include the initial stretch-adjustment ability (physiologic 0) low temperature drift, high linearity (r = 0.99) with loads ranging from 0 to 100 g, and moderate sensitivity of 0.232 mV/V/g at room temperature. The transducer was validated with in-vivo canine experiments. The experimental results showed that this transducer can be used to reliably measure the myocardial force development during altered cardiac conditions, such as myocardial stunning and myocardial ischemia.

Animals↗

PubMed1999

MCA106 fibrosarcoma cells transduced with granulocyte/macrophage colony-stimulating factor are not superior to the wild-type cells in suppressing the growth of hepatic metastases.

BACKGROUND AND OBJECTIVES: Vaccination with cytokine gene-modified tumor cells augments the immune response against established tumors and protects against tumor challenges. In this study, we investigated the vaccine potential of GM-CSF-transduced MCA106 fibrosarcoma (MCA-GMCSF) cells in the C57BL/6 (B6) murine hepatic metastasis model. METHODS: Experimental mice received one to three weekly vaccines (subcutaneous/intramuscular, s.c./i.m.) of irradiated, parental, or GM-CSF-transduced MCA106 tumor cells. One week after the last immunization, hepatic metastases were established through the intrasplenic injection of live MCA106 parental (MCA106P) tumor cells. The animals were then sacrificed 3-4 weeks after surgery for evaluation of hepatic tumor burden. RESULTS: Based on in vivo experiments, both GM-CSF-modified and parental MCA106 tumor cell vaccines induced strong protection against hepatic tumor growth with grossly visible tumors rarely identified. This protection was evident even at a single vaccine dose of as low as 1x10(5) irradiated cells. Unimmunized control mice, on the other hand, consistently developed substantial hepatic tumors. Cytotoxicity assays on splenocytes (cultured in vitro for 4-5 days) showed that both groups of vaccinated mice developed strong tumor-specific cytotoxic T-lymphocyte (CTL) responses. Immunohistochemical analysis of injection sites showed infiltration of dendritic cells (DCs) and macrophages into subcutaneously injected MCA-GMCSF cells. Mostly macrophages, however, were seen at the injection site of MCA106P cells. Furthermore, the MCA106P cells expressed high levels of MHC class I antigens and the level of expression was not significantly altered by transduction with the GM-CSF gene. The high expression of MHC class I antigens probably contributed to the strong immunogenicity of the MCA106P cell vaccine. CONCLUSIONS: This study demonstrates that MCA106 parental cells are as effective as the GM-CSF-transduced cells in suppressing the growth of hepatic metastases. The cellular immune responses induced by these two vaccines, however, are probably mediated by different subsets of host effector cells. These results have important implications for the use of GM-CSF-transduced cell vaccines in the immunotherapy of tumors that have the propensity to metastasize through the lymphatic channels and the circulatory system.

Animals↗

PubMed2003

Dendritic cells transduced with TAT protein transduction domain-containing tyrosinase-related protein 2 vaccinate against murine melanoma.

Incorporation of an 11 amino acid region of the HIV TAT protein transduction domain (TAT PTD) into proteins facilitates rapid, efficient entry into cells. We previously showed that rTAT-PTD-OVA-transduced dendritic cells (DC) stimulated antigen (Ag)-specific CTL and Th cells, and vaccinated against OVA-expressing tumors. Here we studied B16 melanoma in C57BL/6 mice, using murine tyrosinase-related protein 2 (Trp2) as a candidate tumor Ag. We produced a 472-amino acid N-terminal fragment of Trp2 protein (rTrp2Delta) with or without PTD. Although PTD-deficient rTrp2Delta was ineffective, mice given rTAT-PTD-Trp2Delta-transduced DC were efficiently primed for Trp2(180-188) peptide-specific and B16-reactive CTL. In 58% of such mice, growth of melanomas was prevented. Trp2(180-188) peptide-pulsed DC protected 35% of recipients, and irradiated GM-CSF-producing B16 cells protected 75%. rTAT-PTD-Trp2Delta-transduced DC induced a more vigorous memory response to B16 rechallenge than the other regimens, and protected 30% of recipients from progressive tumor development in treatment studies. In this setting, Trp2 peptide-treated DC protected 20% and irradiated GM-CSF-producing cells protected 0%. Both tumor prevention and tumor treatment were CD8(+) T cell dependent. Vaccination with rTAT-PTD-Trp2Delta-transduced DC induced a robust CTL response and durable anti-melanoma immunity. This approach should be clinically applicable, and offers theoretical and practical advantages to those that are in current use.

Animals↗

PubMed1996

Alterations in enzymatic functions in hepatocytes and hepatocellular carcinomas from Ras-transduced livers resemble the effects of insulin.

An understanding of how oncogenes affect differentiated liver functions might lead to improved treatments for liver cancer or other disorders where liver-specific functions are compromised. A retroviral vector that coexpressed beta-galactosidase (beta-gal) and activated Ras genes (Ras-gal) was transduced into a small fraction of adult rat hepatocytes in vivo. Hepatocytes from Ras-gal-transduced diethylnitrosamine-untreated livers and hepatocellular carcinomas (HCC) from Ras-gal-transduced diethylnitrosamine-treated rats were analyzed for liver functions by performing histochemical assays on liver sections. Ras-gal-transduced hepatocytes failed to express gluconeogenic, ketogenic, and urea pathway enzymes. In contrast, several enzymes involved in fat synthesis were strongly activated, and microvesicular fat accumulated. These metabolic changes are induced in normal livers by insulin, a hormone that activates p21-ras. The deregulation of p21-ras may inhibit these liver-specific functions and may induce fat synthesis in both malignant and nonmalignant liver diseases. Furthermore, treatment with drugs that inhibit the attachment of p21-ras to the plasma membrane might reverse these changes. The alterations in enzymatic functions in the HCCs were similar to those observed in the hepatocytes, although each of the two cancers had a region that abruptly lost its expression of liver-specific enzymes and acquired the expression of genes that are more characteristic of oval or bile ductule cells. This suggests that a single genetic event in a malignant cell may dramatically alter its apparent phenotype. The identification of this putative gene might lead to insights into the regulation of the phenotype of normal cells in the liver.

3T3 Cells↗

PubMed2003

In vivo expansion of transduced murine hematopoietic cells with a selective amplifier gene.

BACKGROUND: Hematopoietic stem-cell-directed gene transfer has achieved limited success in transducing clinically relevant levels of target cells. The expansion of gene-modified cells is one way to circumvent the problem of inefficient transduction with current vectors. To this end, we have developed 'selective amplifier genes' (SAGs) that encode chimeric proteins that are a fusion of granulocyte colony-stimulating factor receptor and the steroid-binding domain. Prototype SAGs conferred estrogen-responsive growth on murine hematopoietic progenitors. METHODS: We constructed a retroviral vector coexpressing an SAG for 4-hydroxytamoxifen (Tm)-specific proliferation and the enhanced green fluorescent protein (EGFP). Murine bone marrow cells were transduced with this vector and transplanted into myeloablated mice. Subsequently, recipients were challenged with Tm, and EGFP(+) cells were enumerated. RESULTS: The challenge induced a significant increase in EGFP(+) leukocytes (21 +/- 4% to 27 +/- 5%), while EGFP(+) cells decreased in untreated animals (21 +/- 5% to 10 +/- 3%). Three months later, bone marrow cells were transplanted from the unchallenged mice to secondary hosts. Again the administration of Tm resulted in an increase of EGFP(+) cells (16 +/- 4% to 35 +/- 3%), contrasting to a decrease in controls (22 +/- 4% to 12 +/- 4%), and the difference was significant for more than 3 months. A detailed study of lineage showed a preferential expansion of EGFP(+) cells in granulocytes and monocytes following Tm administration. CONCLUSIONS: Long-term repopulating cells were transduced with the SAG, and the transduced granulocyte/monocyte precursors were most likely to be expandable in vivo upon Tm stimulation.

Animals↗