Theo Z. Pavan
University of São Paulo
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Publication
Featured researches published by Theo Z. Pavan.
Ultrasound in Medicine and Biology | 2013
Sílvio Leão Vieira; Theo Z. Pavan; Jorge Elias Junior; Antonio Adilton Oliveira Carneiro
Paraffin-gel waxes have been investigated as new soft tissue-mimicking materials for ultrasound-guided breast biopsy training. Breast phantoms were produced with a broad range of acoustical properties. The speed of sound for the phantoms ranged from 1425.4 ± 0.6 to 1480.3 ± 1.7 m/s at room temperature. The attenuation coefficients were easily controlled between 0.32 ± 0.27 dB/cm and 2.04 ± 0.65 dB/cm at 7.5 MHz, depending on the amount of carnauba wax added to the base material. The materials do not suffer dehydration and provide adequate needle penetration, with a Youngs storage modulus varying between 14.7 ± 0.2 kPa and 34.9 ± 0.3 kPa. The phantom background material possesses long-term stability and can be employed in a supine position without changes in geometry. These results indicate that paraffin-gel waxes may be promising materials for training radiologists in ultrasound biopsy procedures.
Ultrasound in Obstetrics & Gynecology | 2013
A. H. Miyague; Theo Z. Pavan; F. W. Grillo; Danielle M. Teixeira; C.O. Nastri; Wellington P. Martins
Three-dimensional (3D) power Doppler indices (vascularization index (VI), flow index (FI) and vascularization flow index (VFI)) have been shown to correlate with flow and vascularity1; however, these indices are highly susceptible to machine settings and attenuation2. In this study, we sought to verify whether the volumetric pulsatility index (vPI) based on spatiotemporal image correlation (STIC) power Doppler3 is less dependent on attenuation than the original 3D power Doppler indices obtained from both static 3D and STIC datasets by evaluating a flow phantom. The study model is the same as that described in a previous publication4; essentially, it comprises a flow phantom in which a blood-mimicking fluid flows through a silicon tube, powered by an electric pulsatile pump (Figure 1). We inserted one of two different attenuation blocks, made from the same substances used in the flow phantom structure, each measuring 10 mm in thickness, between the ultrasound probe and the flow phantom5. These blocks had different concentrations of glass beads (1.8% and 4.4%) and therefore different coefficients of attenuation: 0.6 dB/MHz/cm (‘low attenuation’ experiment) and 1.0 dB/MHz/cm (‘high attenuation’ experiment). The preset ‘gynecologic’ was used and the following machine settings were maintained for all acquisitions: depth, 4.2 cm; power, 100%; gain, 0.0; WMF, mid1; PRF, 3.2 KHz;
Journal of Ultrasound in Medicine | 2013
A. H. Miyague; Nick Raine-Fenning; Theo Z. Pavan; Lukasz T. Polanski; Miriam N. Baumgarten; C.O. Nastri; Wellington P. Martins
Spatiotemporal image correlation can be used to acquire 3‐dimensional power Doppler information across a single cardiac cycle. Assessment and comparison of the systolic and diastolic components of the data sets allow measurement of the recently introduced “volumetric pulsatility index” (vPI) through algorithms comparable with those used in 2‐dimensional Doppler waveform analysis. The vPI could potentially overcome the dependency on certain machine settings, such as power, color gain, pulse repetition frequency, and attenuation, since these factors would affect the power Doppler signal equally throughout the cardiac cycle. The objective of this study was to compare the effect of color gain on the vascularization index (VI), vascularization‐flow index (VFI), and vPI using an in vitro flow phantom model. We separated gains into 3 bands: −8 to −1 (no noise), −1 to +5 (low noise), and +5 to +8 (obvious noise). The vPI was determined from the 3‐dimensional VI or VFI using the formula vPI = (maximum − minimum)/mean. Using no‐noise gains, we observed that although the VI and VFI increased linearly with gain, the vPI was substantially less dependent on this adjustment. The VI and VFI continued to increase linearly with gain, whereas the vPI decreased slightly using low‐noise gains. When gain was increased above the lower limit of obvious noise (+5), the VI and VFI increased noticeably, and there were marked reductions in both vPI values. We conclude that the vPI is less affected by changes in color gain than the VI and VFI at no‐noise gains.
Revista Brasileira De Otorrinolaringologia | 2012
Theo Z. Pavan; Martha Funabashi; José Ailton Oliveira Carneiro; Taiza Elaine Grespan dos Santos Pontelli; W. Tedeschi; Antonio Adilton Oliveira Carneiro
UNLABELLED Spatial orientation in relation to the gravitational axis is significantly important for the maintenance of the posture, gait and for most of the humans motor activities. The subjective visual vertical exam evaluates the individuals perception of vertical orientation. OBJECTIVES The aims of this study were (1) to develop a virtual system to evaluate the subjective visual vertical exam, (2) to provide a simple tool to clinical practice and (3) to assess the subjective visual vertical values of healthy subjects using the new software. STUDY DESIGN observational cross-sectional study. METHODS Thirty healthy volunteers performed the subjective visual vertical exam in both static and dynamic conditions. The exam consisted in adjusting a virtual line in the vertical position using the computer mouse. For the static condition, the virtual line was projected in a white background. For the dynamic condition, black circles rotated in clockwise or counterclockwise directions. Six measurements were taken and the mean deviations in relation to the real vertical calculated. RESULTS The mean values of subjective visual vertical measurements were: static -0.372º; ± 1.21; dynamic clockwise 1.53º ± 1.80 and dynamic counterclockwise -1.11º ± 2.46. CONCLUSION This software showed to be practical and accurate to be used in clinical routines.
Physics in Medicine and Biology | 2017
Luciana C. Cabrelli; Pedro I.B.G.B. Pelissari; Alessandro M. Deana; Antonio Adilton Oliveira Carneiro; Theo Z. Pavan
Phantoms mimicking the specific properties of biological tissues are essential to fully characterize medical devices. Water-based materials are commonly used to manufacture phantoms for ultrasound and optical imaging techniques. However, these materials have disadvantages, such as easy degradation and low temporal stability. In this study, we propose an oil-based new tissue-mimicking material for ultrasound and optical imaging, with the advantage of presenting low temporal degradation. A styrene-ethylene/butylene-styrene (SEBS) copolymer in mineral oil samples was made varying the SEBS concentration between 5%-15%, and low-density polyethylene (LDPE) between 0%-9%. Acoustic properties, such as the speed of sound and the attenuation coefficient, were obtained using frequencies ranging from 1-10 MHz, and were consistent with that of soft tissues. These properties were controlled varying SEBS and LDPE concentration. To characterize the optical properties of the samples, the diffuse reflectance and transmittance were measured. Scattering and absorption coefficients ranging from 400 nm-1200 nm were calculated for each compound. SEBS gels are a translucent material presenting low optical absorption and scattering coefficients in the visible region of the spectrum, but the presence of LDPE increased the turbidity. Adding LDPE increased the absorption and scattering of the phantom materials. Ultrasound and photoacoustic images of a heterogeneous phantom made of LDPE/SEBS containing a spherical inclusion were obtained. Annatto dye was added to the inclusion to enhance the optical absorbance. The results suggest that copolymer gels are promising for ultrasound and optical imaging, making them also potentially useful for photoacoustic imaging.
Clinics | 2012
Martha Funabashi; Taiza E. G. Santos-Pontelli; Theo Z. Pavan; Antonio Adilton Oliveira Carneiro; Osvaldo Massaiti Takayanagui
OBJECTIVE: The aim of this study was to assess the subjective visual vertical in patients with bilateral vestibular dysfunction and to propose a new method to analyze subjective visual vertical data in these patients. METHODS: Static subjective visual vertical tests were performed in 40 subjects split into two groups. Group A consisted of 20 healthy volunteers, and Group B consisted of 20 patients with bilateral vestibular dysfunction. Each patient performed six measurements of the subjective visual vertical test, and the mean values were calculated and analyzed. RESULTS: Analyses of the numerical values of subjective visual vertical deviations (the conventional method of analysis) showed that the mean deviation was 0.326±1.13° in Group A and 0.301±1.87° in Group B. However, by analyzing the absolute values of the subjective visual vertical (the new method of analysis proposed), the mean deviation became 1.35±0.48° in Group A and 2.152±0.93° in Group B. The difference in subjective visual vertical deviations between groups was statistically significant (p<0.05) only when the absolute values and the range of deviations were considered. CONCLUSION: An analysis of the absolute values of the subjective visual vertical more accurately reflected the visual vertical misperception in patients with bilateral vestibular dysfunction.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control | 2015
Alexandre Colello Bruno; Diego R. T. Sampaio; Theo Z. Pavan; Oswaldo Baffa; Antonio Adilton Oliveira Carneiro
Gastric emptying reflects a diversity of important physiological functions. Alternating current biosusceptometry (ACB) is an inexpensive, radiation-free, and minimally invasive method to evaluate gastric emptying, but its response depends on the spatial distribution of the magnetized material and does not provide precise anatomical information. The hybrid transducer, which combines ACB and an ultrasound probe, is an alternative to improve susceptometry measurements, namely the spatial localization of the magnetized source. In this study, initial stomach emptying, in rats, was monitored with the aid of the hybrid transducer. Yogurt mixed with ferrite particles was injected into the rats stomach. The hybrid transducer was placed on the rats abdomen during experiments, and the susceptometry signal and magnetomotive ultrasound (MMUS) images were saved and postprocessed. MMUS highlighted the movement of magnetic particles due to magnetic force from ACB excitation coils, and showed the rats stomach location. In this feasibility study, we monitored the stomach emptying of 4 rats for 20 min. The mean relative ACB signal decayed by 4.6 ± 0.1%, and the mean relative area of MMUS images decreased by 4.5 ± 0.2%, after 20 min postingestion of the magnetic meal due to stomach emptying. In a second experiment, 3-D MMUS images from axial sequences were obtained by spatially translating the hybrid transducer, providing details of the stomach wall, which may enable minimally invasive detection of abnormalities. In conclusion, the MMUS image increased ACB spatial resolution and furnished additional anatomical information.
Journal of Ultrasound in Medicine | 2015
A. H. Miyague; Theo Z. Pavan; C. A. Soares; Luc De Catte; C.O. Nastri; A.W. Welsh; Wellington P. Martins
To determine the influence of the pulse repetition frequency (PRF) and wall motion filter on the 3‐dimensional (3D) power Doppler vascularization‐flow index (VFI) and volumetric pulsatility index (PI) obtained from spatiotemporal image correlation (STIC) data sets acquired from a common carotid artery of a healthy participant.
pan american health care exchanges | 2011
Jorge Elias; Fernando Marum Mauad; Valdair Francisco Muglia; Eduardo Caetano; José Sebastião dos Santos; Rafael Kemp; Theo Z. Pavan; Antonio Adilton Oliveira Carneiro
The present study provides preliminary data of the usefulness of elastography applied in intraoperative pancreatic ultrasound for diagnosis and staging of pancreas tumors. We have studied six cases of pancreatic tumors, four adenocarcinomas and one insulinoma, which have been submitted to surgery. Tumor resection was considered based on preoperative evaluation and also in intraoperative findings. Only one patient had no surgical excision of the tumor. All tumors were presented as a “hard” mass in elastography. At least in one case, elastography imaging contributed significantly to demonstrate that there was no vascular invasion when compared to intraoperative gray scale ultrasound alone. There were no identified postoperative complications related to compression during the elastographic evaluation. We conclude that ultrasound elastography is a safe technique to evaluate pancreas intraoperatively and may be useful to diagnose and stage pancreatic tumors.
Journal of Ultrasound in Medicine | 2018
Maricy R. Martins; Wellington P. Martins; C. A. Soares; A. H. Miyague; M.J. Kudla; Theo Z. Pavan
Although power Doppler imaging has been used to quantify tissue and organ vascularity, many studies showed that limitations in defining adequate ultrasound machine settings and attenuation make such measurements complex to be achieved. However, most of these studies were conducted by using the output of proprietary software, such as Virtual Organ computer‐aided analysis (GE Healthcare, Kretz, Zipf, Austria); therefore, many conclusions may not be generalizable because of unknown settings and parameters used by the software. To overcome this limitation, our goal was to evaluate the impact of the flow velocity, pulse repetition frequency (PRF), and wall motion filter (WMF) on power Doppler image quantification using beam‐formed ultrasonic radiofrequency data.