Author
Douglas R. Hansmann
Other affiliations: University of California, Irvine
Bio: Douglas R. Hansmann is an academic researcher from Cedars-Sinai Medical Center. The author has contributed to research in topics: Ultrasound & Ultrasonic sensor. The author has an hindex of 15, co-authored 23 publications receiving 1005 citations. Previous affiliations of Douglas R. Hansmann include University of California, Irvine.
Papers
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TL;DR: An optical fluorescence based intravascular blood gas monitoring system has been developed which is particularly suited for the critical care and surgical settings and which has a sensor probe that can be introduced into the patient via a radial artery catheter.
Abstract: Optical fluorescence has an extensive history of application in the laboratory to the measurement of ionic concentrations and the partial pressures of oxygen and carbon dioxide. The use of optical fluorescence based sensors to fulfill a recognized need for continuous invasive monitoring of arterial blood gases offers a number of inherent advantages. However, the requirements placed upon a blood gas probe and supporting instrumentation appropriate for use in the clinical environment result in significant design challenges in selection of suitable fluorescent dyes, maintenance of mechanical integrity while obtaining required miniaturization of sensors, and in the transmission, acquisition, and processing of low level light signals. An optical fluorescence based intravascular blood gas monitoring system has been developed which is particularly suited for the critical care and surgical settings and which has a sensor probe that can be introduced into the patient via a radial artery catheter. This system has shown an excellent agreement of measured with true values of pH, pCO2, and P02 in both in vitro and animal studies. Linear regression analysis of typical in vitro data, where true levels were established via tonometry and standardization to a high accuracy laboratory pH measuring instrument, shows slope/intercept values very close to 1.0/0.0 and correlation coefficients of greater than 0.99 for all three parameters.
298 citations
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12 Apr 2006
TL;DR: In this paper, a method of applying ultrasonic energy to a treatment site within a patient's vasculature comprises positioning an ultrasound radiating member at the treatment site and activating it to produce pulses at a cycle period T ≤ 1 second.
Abstract: In one embodiment of the present invention, a method of applying ultrasonic energy to a treatment site within a patient's vasculature comprises positioning an ultrasound radiating member at a treatment site within a patient's vasculature. The method further comprises activating the ultrasound radiating member to produce pulses of ultrasonic energy at a cycle period T ≤ 1 second. Each pulse of ultrasonic energy has a first peak amplitude for a first duration, and a second reduced amplitude that is less than the first peak amplitude for a second duration.
161 citations
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TL;DR: Lysis and drainage of spontaneous ICH and IVH with a reduction in mass effect can be accomplished rapidly and safely through sonothrombolysis using stereotactically delivered drainage and ultrasound catheters via a bur hole.
Abstract: Object Catheter-based evacuation is a novel surgical approach for the treatment of brain hemorrhage The object of this study was to evaluate the safety and efficacy of ultrasound in combination with recombinant tissue plasminogen activator (rt-PA) delivered through a microcatheter directly into spontaneous intraventricular (IVH) or intracerebral (ICH) hemorrhage in humans Methods Thirty-three patients presenting to the Swedish Medical Center in Seattle, Washington, with ICH and IVH were screened between November 21, 2008, and July 13, 2009, for entry into this study Entry criteria included the spontaneous onset of intracranial hemorrhage ≥ 25 ml and/or IVH producing ventricular obstruction Nine patients (6 males and 3 females, with an average age of 63 years [range 38–83 years]) who met the entry criteria consented to participate and were entered into the trial A ventricular drainage catheter and an ultrasound microcatheter were stereotactically delivered together, directly into the IVH or ICH Recom
92 citations
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17 Feb 2011
TL;DR: In this article, a method of treating a vascular occlusion located at a treatment site within a patient's vasculature comprises positioning an ultrasound catheter at the treatment site.
Abstract: In one embodiment of the present invention, a method of treating a vascular occlusion located at a treatment site within a patient's vasculature comprises positioning an ultrasound catheter at the treatment site. The method further comprises delivering a microbubble therapeutic compound from the ultrasound catheter to the vascular occlusion during a first treatment phase. The method further comprises pausing the delivery of the microbubble therapeutic compound and delivering ultrasonic energy from the ultrasound catheter to the vascular occlusion during a second treatment phase while the delivery of microbubble therapeutic compound remains paused.
78 citations
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TL;DR: The accuracy of the retracted probe was evaluated in 4 subjects who breathed varying fractions of inspired oxygen and carbon dioxide and the mean in vivo 90% response times for step changes in inspired gas were 2.64, 3.88, and 2.60 minutes, respectively, for pHi, PiCO2, and PiO2.
Abstract: In vitro and in vivo animal studies have shown accurate measurements of arterial blood pH (pHa), carbon dioxide tension (PaCO2), and oxygen tension (PaO2) with small intravascular fluorescent probes. Initial human clinical studies showed unexplained intermittent large drops in sensor oxygen tension (PiO2). Normal volunteers were studied to elucidate this problem. In the first part of this study, the probe and cannula were manipulated and the probe configuration and its position within the cannula were varied. The decreases in PiO2 were judged to be primarily due to the sensor touching the arterial wall. Retraction of the sensor tip within the cannula eliminated the problem. In the second part of this study, the accuracy of the retracted probe was evaluated in 4 subjects who breathed varying fractions of inspired oxygen and carbon dioxide. The arterial ranges achieved were 7.20 to 7.59 for pH, 22 to 70 mm Hg for PaCO2, and 46 to 633 mm Hg for PaO2. Linear regression of 48 paired sensor (i) versus arterial values showed pHi = 0.896 pHa + 0.773 (r = 0.98, SEE = 0.017); PiCO2 = 1.05 PaCO2-1.33 (r = 0.98, SEE = 2.4 mm Hg); and PiO2 = 1.09 PaO2-20.6 (r = 0.99, SEE = 21.2 mm Hg). Bias (defined as the mean differences between sensor and arterial values) and precision (SD of differences) were, respectively, -0.003 and 0.02 tor pHi, 0.77 and 2.44 mm Hg for PiCO2, and -2.9 and 25.4 mm Hg for PiO2. The mean in vivo 90% response times for step changes in inspired gas were 2.64, 3.88, and 2.60 minutes, respectively, for pHi, PiCO2, and PiO2.
56 citations
Cited by
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01 Oct 2010TL;DR: A control circuit of a surgical device is described in this paper, which includes a first circuit portion coupled to at least one switch operable between an open state and a closed state.
Abstract: A control circuit of a surgical device is disclosed. The control circuit includes a first circuit portion coupled to at least one switch operable between an open state and a closed state. The first circuit portion communicates with a surgical generator over a conductor pair to receive a control signal to determine a state of the at least one switch.
1,056 citations
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30 Mar 2012TL;DR: In this paper, a transducer and an end effector are configured to provide vibrations along a longitudinal axis at a predetermined frequency and may comprise a piezoelectric stack positioned along the longitudinal axis.
Abstract: A surgical instrument. The surgical instrument may comprise a transducer and an end effector. The transducer may be configured to provide vibrations along a longitudinal axis at a predetermined frequency and may comprise a piezoelectric stack positioned along the longitudinal axis. The transducer also may comprise a first metallic end mass positioned along the longitudinal axis adjacent a first end of the piezoelectric stack and a second metallic end mass positioned along the longitudinal axis adjacent a second end of the piezoelectric stack. The length of the transducer may be greater than or equal to of one wavelength and less than ½ of one wavelength. The end effector may be coupled to the transducer and may extend along the longitudinal axis. The length of the transducer and the end effector may be a multiple of ½ of one wavelength.
954 citations
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TL;DR: Important advances have been made in animal models of this disorder and in the understanding of mechanisms underlying brain injury after haemorrhage, and several therapeutic targets have subsequently been identified that are now being pursued in clinical trials.
Abstract: Summary Intracerebral haemorrhage accounts for about 10–15% of all strokes and is associated with high mortality and morbidity. No successful phase 3 clinical trials for this disorder have been completed. In the past 6 years, the number of preclinical and clinical studies focused on intracerebral haemorrhage has risen. Important advances have been made in animal models of this disorder and in our understanding of mechanisms underlying brain injury after haemorrhage. Several therapeutic targets have subsequently been identified that are now being pursued in clinical trials. Many clinical trials have been based on limited preclinical data, and guidelines to justify taking preclinical results to the clinic are needed.
837 citations
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03 Aug 2009TL;DR: In this article, a generator coupled to an ultrasonic transducer is used to generate a first ultrasonic drive signal for a first period, followed by a second drive signal subsequent to the first period.
Abstract: Various embodiments are directed to an apparatus, system, and method for driving an end effector coupled to an ultrasonic transducer in a surgical instrument. The method comprises generating a first ultrasonic drive signal by a generator coupled to an ultrasonic drive system, actuating the ultrasonic transducer with the first ultrasonic drive signal for a first period, generating a second ultrasonic drive signal by the generator, and actuating the ultrasonic transducer with the second ultrasonic drive signal for a second period, subsequent to the first period. The first drive signal is different from the second drive signal over the respective first and second periods. The first and second drive signals define a step function waveform over the first and second periods. The apparatus comprises a generator configured to couple to an ultrasonic instrument. The system comprises a generator coupled to an ultrasonic instrument. The ultrasonic instrument comprises an ultrasonic drive system comprising an ultrasonic transducer coupled to a waveguide and an end effector coupled to the waveguide, and wherein the ultrasonic drive system is configured to resonate at a resonant frequency.
792 citations
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14 Jun 2013TL;DR: In this article, a proximally positioned straight section extending along a longitudinal axis and a distally positioned curved section coupled to the straight section and curved away from the longitudinal axis are described.
Abstract: Various embodiments described herein are directed to ultrasonic blades. For example, an ultrasonic blade may comprise a proximally positioned straight section extending along a longitudinal axis and a distally positioned curved section coupled to the straight section and curved away from the longitudinal axis. The curved section may define a radius of curvature and subtend a first angle. A point of tangency between the curved section and the straight section may be positioned at either a node of the ultrasonic blade or an anti-node of the ultrasonic blade.
778 citations