Search results for "doppler"
showing 10 items of 637 documents
Transcranial Doppler and Cortical Microcirculation at Increased Intracranial Pressure and during the Cushing Response
1995
The effect of increased intracranial pressure on the flow velocity of the basilar artery was measured with transcranial ultrasonic Doppler in New Zealand White rabbits under alpha-chloralose anesthesia and artificial respiration. Laser Doppler flowmetry served to study changes of the cortical microcirculation. The results confirm a high inverse correlation of the diastolic flow velocity, the pulsatility index, and the resistance index with the cerebral perfusion pressure (CPP). During acute intracranial hypertension, however, these parameters do not show a good correlation with the local cortical blood flow. The absence of a correlation was evident over a wide CPP range down to values of 35…
Does transvaginal color Doppler sonography differentiate between developing and involuting ectopic pregnancies?
1995
The objective of this study was to assess the addition of transvaginal color Doppler imaging to transvaginal ultrasonography and beta-human chorionic gonadotropin values to differentiate between developin and involuting ectopic pregnancies. Forty surgically confirmed ectopic pregnancies were classified into developing or involuting according to histopathologic findings. Results were compared retrospectively with the plasma beta-human chorionic gonadotropin values as well as the resistive index and pulsatility index obtained in corpora lutea and peritrophoblastic flow in serial examinations. Student's t-test was used for comparison of means. Logistic regression analysis was applied to predic…
A Channel-Aware Adaptive System for Underwater Acoustic Communications
2021
In recent years, underwater communications have seen a growing interest pushed by marine research, oceanography, marine commercial operations, offshore oil industry and defense applications. Generally, underwater communications employ audio signals which can propagate relatively far. However, acoustic underwater channels are very challenging, because of limited bandwidth, long propagation delays, extended multipath, severe attenuation, rapid time variation and large Doppler shifts. A plethora of underwater communication techniques have been developed for dealing with such a complexity, mostly tailoring specific applications scenarios which can not be considered as one-size-fits-all solution…
Value of color doppler jet area for grading regurgitation severity in patients with secondary mitral regurgitation - better than its reputation?
2013
High-intensity transient signals during laparoscopic surgery in children.
2009
Background Laparoscopic interventions in children gain increasing popularity. Pneumoperitoneum as applied during laparoscopic surgery can induce gas emboli formation, but it is unclear whether this is associated with cerebral embolic events. To investigate the hypothesis that pneumoperitoneum causes cerebral emboli in children, the number and intensity of high-intensity transient signals (HITS) detected using transcranial Doppler ultrasonography were assessed before and after induction of pneumoperitoneum. Methods Twenty children were monitored during laparoscopic surgery. General anaesthesia was performed using sevoflurane and sufentanil or alfentanil. Pressure-controlled ventilation was a…
The role of Doppler ultrasonography in determining the proper surgical approach to the management of varicocele in children and adolescents
2006
In a study from Italy, colour-Doppler ultrasonography was a reliable diagnostic tool in the preoperative assessment of patients with varicocele. The authors also found that it helped to distinguish those who could be treated laparoscopically from those who should be treated by microsurgical subinguinal ligature. OBJECTIVE To investigate whether colour Doppler ultrasonography (CDUS) is a reliable diagnostic tool for selecting patients with varicocele to undergo either laparoscopy or open microsurgical subinguinal ligation. PATIENTS AND METHODS In a 3-year period, 42 boys affected by left varicocele were evaluated before surgery by inguinal and scrotal CDUS. Using this method it was possible …
Remote Photoplethysmography for Evaluation of Cutaneous Sensory Nerve Fiber Function
2021
About 2% of the world’s population suffers from small nerve fiber dysfunction, neuropathy, which can result in severe pain. This condition is caused by damage to the small nerve fibers and its assessment is challenging, due to the lack of simple and objective diagnostic techniques. The present study aimed to develop a contactless photoplethysmography system using simple instrumentation, for objective and non-invasive assessment of small cutaneous sensory nerve fiber function. The approach is based on the use of contactless photoplethysmography for the characterization of skin flowmotions and topical heating evoked vasomotor responses. The feasibility of the technique was evaluated on volunt…
Implementation of laser speckle contrast analysis as connection kit for mobile phone for assessment of skin blood flow
2014
Laser speckle contrast analysis (LASCA) offers a non-contact, full-field, and real-time mapping of capillary blood flow and can be considered as an alternative method to Laser Doppler perfusion imaging. LASCA technique has been implemented in several commercial instruments. However, these systems are still too expensive and bulky to be widely available. Several optical techniques have found new implementations as connection kits for mobile phones thus offering low cost screening devices. In this work we demonstrate simple implementation of LASCA imaging technique as connection kit for mobile phone for primary low-cost assessment of skin blood flow. Stabilized 650 nm and 532 nm laser diode m…
A simple technique for measurement of corneal thickness.
1998
Measurement of corneal thickness has potential benefit both in the fitting of contact lenses and in monitoring any pathology that could affect corneal thickness. Corneal thickness measurement is undertaken using an accessory to the biomicroscope, the optical pachometer, or by means of expensive apparatus such as the ultrasonic pachometer. There are other complex methods, such as laser Doppler interferometry, or ultrasonic rasters of the cornea. In this study, an easier and low cost method, based on the measurement of the optical section formed of the cornea by the biomicroscope illumination system, is proposed. The advantages of this new method are the simplicity of its experimental set-up …