Biomedical subjects

Francisco Gayá

Publications and source records attributed to Francisco Gayá.

4 recordsLinked to original sources

PubMed2006

Compact laser radar and three-dimensional camera.

A novel three-dimensional (3D) camera is capable of providing high-precision 3D images in real time. The camera uses a diode laser to illuminate the scene, a shuttered solid-state charge-coupled device (CCD) sensor, and a simple phase detection technique based on the sensor shutter. The amplitude of the reflected signal carries the luminance information, while the phase of the signal carries range information. The system output is coded as a video signal. This camera offers significant advantages over existing technology. The precision in range is dependent only on phase shift and laser power and theoretically is far superior to existing time-of-flight laser radar systems. Other advantages are reduced size and simplicity and compact and inexpensive construction. We built a prototype that produced high-resolution images in range the (z) and x-y.

Journal Article↗

PubMed2005

Vesicoureteral reflux: can the urethra be adequately assessed by using contrast-enhanced voiding US of the bladder?

PURPOSE: To prospectively evaluate contrast material-enhanced voiding ultrasonography (US) for assessment of the urethra by using voiding cystourethrography (VCUG) as the reference standard. MATERIALS AND METHODS: This study was approved by the ethics committee on human research. Written informed consent was obtained for all patients. A total of 146 pediatric patients suspected of having vesicoureteral reflux underwent US with a galactose-based contrast agent. The bladder was instilled with contrast agent and then filled with saline. US images of the urethra were videotaped before catheterization and during voiding. VCUG was subsequently performed in all patients. In female patients, the probe (a 3.5- or 5-MHz sector array or a 7.5-MHz linear transducer) was positioned longitudinally between the labia. In male patients, the transducer was placed longitudinally on the scrotum and then displaced distally toward the penile urethra. During voiding, attention was focused on the distention of the urethral walls and on the caliber of both the posterior and anterior urethra, which were measured with calipers. Sensitivity and specificity were estimated by using a confidence interval (CI) of 95%. RESULTS: All female patients and 75 male patients showed a normal urethra at both US and VCUG. Posterior urethral valves (PUV) were diagnosed in three patients at voiding US and were confirmed with findings from VCUG. Urethral stenosis was diagnosed in two male patients at voiding US and was confirmed with findings from VCUG. Seven male patients who had undergone surgery for PUV were adequately evaluated with both modalities. Sensitivity of voiding US was 100% (CI 95%: 96.5%, 100%); specificity was 100% (CI 95%: 69.9%, 100%). CONCLUSION: Voiding US is a reliable imaging modality for studying the urethra.

Adolescent↗

PubMed2005

Cardiovascular support for low birth weight infants and cerebral hemodynamics: a randomized, blinded, clinical trial.

BACKGROUND: Maintaining adequate organ blood flow is the target of vasopressor treatment, but the impact of these measures on cerebral perfusion has not yet been evaluated systematically in a randomized, blinded, clinical trial. OBJECTIVES: To explore the effects on brain hemodynamics of 2 different inotropic agents used to treat systemic hypotension among low birth weight (LBW) infants. DESIGN AND METHODS: Newborns of <1501 g birth weight or <32 weeks' gestational age, with a mean blood pressure (MBP) lower than gestational age in the first 24 hours of life, were assigned randomly to receive dopamine (DP) (2.5, 5, 7.5, or 10 microg/kg per minute; n = 28) or epinephrine (EP) (0.125, 0.250, 0.375, or 0.5 microg/kg per minute; n = 32), at doses that were increased in a stepwise manner every 20 minutes until the optimal MBP (MBP-OP) was attained and maintained. OUTCOME MEASURES: Continuous monitoring of quantitative changes in cerebral concentrations of oxyhemoglobin and deoxyhemoglobin, cerebral intravascular oxygenation (HbD) (the difference between oxyhemoglobin and deoxyhemoglobin), and cerebral blood volume (CBV) were assessed with near-infrared spectroscopy. MBP, heart rate, transcutaneous Pco2 and Po2, and peripheral oxygen saturation were recorded continuously and analyzed at baseline, 20 minutes after each dose increase (T1, T2, T3, and T4) until MBP-OP was reached, and then every 20 minutes up to 1 hour of stable MBP-OP. RESULTS: Fifty-nine infants were considered for analysis. Patients did not differ in birth weight or gestational age (1008 +/- 286 g and 28.3 +/- 2.3 weeks, respectively, in the DP group and 944 +/- 281 g and 27.7 +/- 2.4 weeks in the EP group). Studies were performed at a mean age of 5.3 +/- 3.7 hours of life (range: 2-16 hours). MBP-OP was attained for 96.3% of patients with DP and 93.7% with EP (responders). For those patients, MBP, heart rate, CBV, and HbD increased from baseline throughout the study period, with no differences between groups except for a higher heart rate with EP. Changes in MBP were correlated significantly with changes in HbD. Dose escalation of drugs produced no differences between groups in the behavior of the variables, except for a greater heart rate with EP from 20 minutes after dose 2 (T2) onward. Drug-induced changes in cerebral hemodynamics varied with gestational age; the EP-induced increase in CBV was greater among less mature patients (<28 weeks), whereas the DP-induced increase in CBV was greater among patients of > or =28 weeks. CONCLUSIONS: Among hypotensive LBW infants, cardiovascular support with low/moderate-dose DP or low-dose EP increased cerebral perfusion, as indicated by the increase in both CBV and HbD. Low-dose EP was as effective as low/moderate-dose DP in increasing MBP among LBW infants.

Blood Pressure↗

PubMed2002

Noninvasive continuous monitoring of the effects of head position on brain hemodynamics in ventilated infants.

HYPOTHESIS: Laying supine with the head in midline position improves cerebral venous return by preventing functional occlusion of the vessels of the neck. OBJECTIVES: To assess changes in cerebral blood volume (DeltaCBV) and cerebral blood flow (CBF) with the position of the head in ventilated patients using a noninvasive method. The influence of the type of ventilation and birth weight was evaluated. METHODS: Thirteen conventionally ventilated and 8 high-frequency oscillatory ventilated infants, with mean gestational ages and birth weights of 31 +/- 5 weeks (24--38) and 1575 +/- 803 g (560--3000), respectively, were studied 5.8 +/- 7.8 days (1--33) after birth. DeltaCBV (mL/100 g) and CBF (mL/100 g/min) were measured by near-infrared spectroscopy with the head in supine midline position (DeltaCBVs, CBFs) and rotated 90 to one side (DeltaCBVlat, CBFlat). Heart rate, peripheral saturation, transcutaneous PCO(2), and blood pressure were monitored continuously. Ventilatory settings remained constant throughout the study period. RESULTS: Mean DeltaCBVs was lower than mean DeltaCBVlat, although no changes in blood pressure, transcutaneous PCO(2), oxygenation, or heart rate occurred. This change in DeltaCBV was not associated with the type of ventilation or birth weight, but the differences tended to be greater (dDeltaCBV = DeltaCBVlat-DeltaCBVs) in the smallest infants (<1200 g). In contrast, CBF did not vary. CONCLUSION: The supine midline position of the head favors cerebral venous drainage and helps to prevent elevation of CBV. SPECULATION: This finding may be important in the first days of life, particularly in tiny preterm infants recovering from lung disease with improving lung compliance, in which functional obstruction of cerebral venous drainage should be avoided.

Birth Weight↗