M. Guarini - Academia.edu (original) (raw)
Papers by M. Guarini
2006 IEEE 3rd Latin American Robotics Symposium, 2006
... Xk = (Xk Yk Sk Vk Uk Sok) (7) where Xk is used to denote the state vector, and should no be c... more ... Xk = (Xk Yk Sk Vk Uk Sok) (7) where Xk is used to denote the state vector, and should no be confused with the position coordinate Xk. ... This is done in the same fashion as in [1], were thea's are calculated to reflect the acceleration that the robots are limited due to the wheel slip. ...
BioMedical Engineering OnLine, 2010
Background It is known that tight control of glucose in the Intensive Care Unit reduces morbidity... more Background It is known that tight control of glucose in the Intensive Care Unit reduces morbidity and mortality not only in diabetic patients but also in those non-diabetics who become transiently hyperglycemic. Taking advantage of a recently marketed subcutaneous glucose sensor we designed an Automatic Insulin Infusion System (AIIS) for inpatient treatment, and tested its stability under simulated clinical conditions. Methods The system included: reference glucose, glucose sensor, insulin and glucose infusion controllers and emergency infusion logic. We carried out computer simulations using Matlab/Simulink®, in both common and worst-case conditions. Results The system was capable of controlling glucose levels without entering in a phase of catastrophic instability, even under severe simulated challenges. Care was taken to include in all simulations the 5-10 minute delay of the subcutaneous glucose signal when compared to the real-time serum glucose signal, a well-known characteris...
C. A. Tejos, M. Guarini, P. Irarrazaval Department of Electrical Engineering, Pontificia Universi... more C. A. Tejos, M. Guarini, P. Irarrazaval Department of Electrical Engineering, Pontificia Universidad Catolica de Chile, Santiago, Chile Introduction In medical imaging studies that analyse the evolution of structures through time, measurements of anatomical parameters must be preceded by a registration and a segmentation process, to provide the location correspondence of equivalent structures on different images, and the selection of the object of interest, respectively. Clearly both processes have a strong dependency between each other. For example, in MRI scans of articular joints, a single rigid-body registration cannot be applied, since the relative movements among bones provide additional degrees of freedom. Thus, a rigid-body registration can only be done analysing each articular structure independently, and therefore, image segmentations are needed in advance. Several authors [1]-[4] have successfully developed joint segmentation and registration schemes, however, those techn...
This paper describes an expert system for the supervision of flotation plants that uses ACEFLOT, ... more This paper describes an expert system for the supervision of flotation plants that uses ACEFLOT, a real-time analyzer of the dynamic characteristics of flotation froth. The ACEFLOT analyzer, based on image processing, measures several physical parameters of the froth that forms on the cell surface. The expert system detects abnormal operation and suggests corrective actions, supporting operators on the supervision and control of the flotation plant
Minerals Engineering, 1998
This paper describes an expert system for the supervision of flotation plants based on ACEFLOT, a... more This paper describes an expert system for the supervision of flotation plants based on ACEFLOT, a real time analyzer of the characteristics of the froth that is formed on the surface of flotation cells. The ACEFLOT analyzer is based on image processing and measures several physical variables of the froth, including colorimetric, geometric and dynamic information. On the other hand, the expert system detects abnormal operation states and suggests corrective actions, supporting operators on the supervision and control of the flotation plant.
International Journal for Numerical Methods in Engineering, 2010
Medical Imaging, IEEE …, 2004
Magnetic resonance imaging (MRI) provides bidimensional images with high definition and selectivi... more Magnetic resonance imaging (MRI) provides bidimensional images with high definition and selectivity. Selective excitations are achieved applying a gradient and a radio frequency (RF) pulse simultaneously. They are modeled by the Bloch differential equation, which has no closed-form solution. Most methods for designing RF pulses are derived from approximation of this equation or are based on iterative optimization methods. The approximation methods are only valid for small tip angles and the optimization-based algorithms yield better results, but they are computationally intensive. To improve the solutions and to reduce processing time, a method for designing RF pulses using a pseudospectral approach is presented. The Bloch equation is expanded in Chebyshev series, which can be solved using a sparse linear algebraic system. The method permits three different formulations derived from the optimal control theory, minimum distance, minimum energy, or minimum time, which are solved as algebraic constrained minimization problems. The results were validated through simulated and real experiments of 90 degrees and 180 degrees RF pulses. They show improvements compared to the corresponding solutions obtained using the Shinnar-Le Roux method. The minimum time formulation produces the best performance for 180 degrees pulses, reducing the excitation length in 4% and the RF pulse energy in 3%.
Biological Research, 1999
A simplified model for the arterial pressure control system was implemented on a personal compute... more A simplified model for the arterial pressure control system was implemented on a personal computer using Matlab Simulink. Model responses to variations of systemic vascular resistance were comparable to those predicted by physiology. Computer simulation suggested that including this model of the internal pressure control system within the design of an external controller would achieve better arterial pressure control and faster response than previous systems.
Journal of clinical monitoring and computing, 1998
We propose that it is possible to estimate cardiovascular parameters from the arterial pressure w... more We propose that it is possible to estimate cardiovascular parameters from the arterial pressure waveform, including ventricular maximal elastance and end-diastolic volume, if cardiac output is also known. We tested this hypothesis by means of a parameter estimation algorithm applied to simulated arterial pressure signals. The program first estimated three coefficients representing products of passive parameters from the diastolic part of the simulated arterial pressure waveform. Second, it estimated three parameter products pertaining to the ventricular function from the systolic part of the waveform. Third, mean blood flow was entered, enabling the program to compute individual parameters. This program was tested on 200 computer-generated arterial pressure signals, obtained by simulating the model with random but bounded parameters. Correlation between estimated parameters with those actually used in the simulations was excellent. Even though the value of this computer simulation i...
References: [1] van Vaals et al. JMRI 3,4 (1993); [2] Jones et al.MRM 29,6 (1993); [3] Tsao et al... more References: [1] van Vaals et al. JMRI 3,4 (1993); [2] Jones et al.MRM 29,6 (1993); [3] Tsao et al. MRM 50,5 (2003); [4] Madore et al.MRM 42,5 (1999); [5] d'Arcy et al. NMR 15 (2002); [6] Irarrazaval et al. MRM 54,5 (2005); [7] ESMRMB 2008 pp. Fig. 2. RMS errors as a function of time for TRIO with intensity order estimated from Keyhole, k-t BLAST and Sliding Window, compared against the first reconstructions
Magnetic …, 2005
In 3D MRI, sampling k-space with traditional trajectories can be excessively time-consuming. Fast... more In 3D MRI, sampling k-space with traditional trajectories can be excessively time-consuming. Fast imaging trajectories are used in an attempt to efficiently cover the k-space and reduce the scan time without significantly affecting the image quality. In many applications, further ...
Monthly Notices of the Royal Astronomical Society, 2015
Computers in Cardiology 1994, 1995
An interactive scheme for the development of a fuzzy logic based model has been implemented and a... more An interactive scheme for the development of a fuzzy logic based model has been implemented and applied to build a model that is able to determine cardiac output from radial arterial pressure. It was built using as input radial pressure waveforms from patients in whom cardiac output was simultaneously measured by thermodilution. The scheme was programmed in C language in
Journal of clinical monitoring and computing, 1999
Intensive care and operating room monitors generate data that are not fully utilized. False alarm... more Intensive care and operating room monitors generate data that are not fully utilized. False alarms are so frequent that attending personnel tends to disconnect them. We developed an expert system that could select and validate alarms by integration of seven vital signs monitored on-line from cardiac surgical patients. The system uses fuzzy logic and is able to work under incomplete or noisy information conditions. Patient status is inferred every 2 seconds from the analysis and integration of the variables and a unified alarm message is displayed on the screen. The proposed structure was implemented on a personal computer for simultaneous automatic surveillance of up to 9 patients. The system was compared with standard monitors (SpaceLabs PC2), using their default alarm settings. Twenty patients undergoing cardiac surgery were studied, while we ran our system and the standard monitor simultaneously. The number of alarms triggered by each system and their accuracy and relevance were ...
Journal of clinical monitoring and computing, 1998
We propose that it is possible to estimate cardiovascular parameters from the arterial pressure w... more We propose that it is possible to estimate cardiovascular parameters from the arterial pressure waveform, including ventricular maximal elastance and end-diastolic volume, if cardiac output is also known. We tested this hypothesis by means of a parameter estimation algorithm applied to simulated arterial pressure signals. The program first estimated three coefficients representing products of passive parameters from the diastolic part of the simulated arterial pressure waveform. Second, it estimated three parameter products pertaining to the ventricular function from the systolic part of the waveform. Third, mean blood flow was entered, enabling the program to compute individual parameters. This program was tested on 200 computer-generated arterial pressure signals, obtained by simulating the model with random but bounded parameters. Correlation between estimated parameters with those actually used in the simulations was excellent. Even though the value of this computer simulation i...
2006 IEEE 3rd Latin American Robotics Symposium, 2006
... Xk = (Xk Yk Sk Vk Uk Sok) (7) where Xk is used to denote the state vector, and should no be c... more ... Xk = (Xk Yk Sk Vk Uk Sok) (7) where Xk is used to denote the state vector, and should no be confused with the position coordinate Xk. ... This is done in the same fashion as in [1], were thea's are calculated to reflect the acceleration that the robots are limited due to the wheel slip. ...
BioMedical Engineering OnLine, 2010
Background It is known that tight control of glucose in the Intensive Care Unit reduces morbidity... more Background It is known that tight control of glucose in the Intensive Care Unit reduces morbidity and mortality not only in diabetic patients but also in those non-diabetics who become transiently hyperglycemic. Taking advantage of a recently marketed subcutaneous glucose sensor we designed an Automatic Insulin Infusion System (AIIS) for inpatient treatment, and tested its stability under simulated clinical conditions. Methods The system included: reference glucose, glucose sensor, insulin and glucose infusion controllers and emergency infusion logic. We carried out computer simulations using Matlab/Simulink®, in both common and worst-case conditions. Results The system was capable of controlling glucose levels without entering in a phase of catastrophic instability, even under severe simulated challenges. Care was taken to include in all simulations the 5-10 minute delay of the subcutaneous glucose signal when compared to the real-time serum glucose signal, a well-known characteris...
C. A. Tejos, M. Guarini, P. Irarrazaval Department of Electrical Engineering, Pontificia Universi... more C. A. Tejos, M. Guarini, P. Irarrazaval Department of Electrical Engineering, Pontificia Universidad Catolica de Chile, Santiago, Chile Introduction In medical imaging studies that analyse the evolution of structures through time, measurements of anatomical parameters must be preceded by a registration and a segmentation process, to provide the location correspondence of equivalent structures on different images, and the selection of the object of interest, respectively. Clearly both processes have a strong dependency between each other. For example, in MRI scans of articular joints, a single rigid-body registration cannot be applied, since the relative movements among bones provide additional degrees of freedom. Thus, a rigid-body registration can only be done analysing each articular structure independently, and therefore, image segmentations are needed in advance. Several authors [1]-[4] have successfully developed joint segmentation and registration schemes, however, those techn...
This paper describes an expert system for the supervision of flotation plants that uses ACEFLOT, ... more This paper describes an expert system for the supervision of flotation plants that uses ACEFLOT, a real-time analyzer of the dynamic characteristics of flotation froth. The ACEFLOT analyzer, based on image processing, measures several physical parameters of the froth that forms on the cell surface. The expert system detects abnormal operation and suggests corrective actions, supporting operators on the supervision and control of the flotation plant
Minerals Engineering, 1998
This paper describes an expert system for the supervision of flotation plants based on ACEFLOT, a... more This paper describes an expert system for the supervision of flotation plants based on ACEFLOT, a real time analyzer of the characteristics of the froth that is formed on the surface of flotation cells. The ACEFLOT analyzer is based on image processing and measures several physical variables of the froth, including colorimetric, geometric and dynamic information. On the other hand, the expert system detects abnormal operation states and suggests corrective actions, supporting operators on the supervision and control of the flotation plant.
International Journal for Numerical Methods in Engineering, 2010
Medical Imaging, IEEE …, 2004
Magnetic resonance imaging (MRI) provides bidimensional images with high definition and selectivi... more Magnetic resonance imaging (MRI) provides bidimensional images with high definition and selectivity. Selective excitations are achieved applying a gradient and a radio frequency (RF) pulse simultaneously. They are modeled by the Bloch differential equation, which has no closed-form solution. Most methods for designing RF pulses are derived from approximation of this equation or are based on iterative optimization methods. The approximation methods are only valid for small tip angles and the optimization-based algorithms yield better results, but they are computationally intensive. To improve the solutions and to reduce processing time, a method for designing RF pulses using a pseudospectral approach is presented. The Bloch equation is expanded in Chebyshev series, which can be solved using a sparse linear algebraic system. The method permits three different formulations derived from the optimal control theory, minimum distance, minimum energy, or minimum time, which are solved as algebraic constrained minimization problems. The results were validated through simulated and real experiments of 90 degrees and 180 degrees RF pulses. They show improvements compared to the corresponding solutions obtained using the Shinnar-Le Roux method. The minimum time formulation produces the best performance for 180 degrees pulses, reducing the excitation length in 4% and the RF pulse energy in 3%.
Biological Research, 1999
A simplified model for the arterial pressure control system was implemented on a personal compute... more A simplified model for the arterial pressure control system was implemented on a personal computer using Matlab Simulink. Model responses to variations of systemic vascular resistance were comparable to those predicted by physiology. Computer simulation suggested that including this model of the internal pressure control system within the design of an external controller would achieve better arterial pressure control and faster response than previous systems.
Journal of clinical monitoring and computing, 1998
We propose that it is possible to estimate cardiovascular parameters from the arterial pressure w... more We propose that it is possible to estimate cardiovascular parameters from the arterial pressure waveform, including ventricular maximal elastance and end-diastolic volume, if cardiac output is also known. We tested this hypothesis by means of a parameter estimation algorithm applied to simulated arterial pressure signals. The program first estimated three coefficients representing products of passive parameters from the diastolic part of the simulated arterial pressure waveform. Second, it estimated three parameter products pertaining to the ventricular function from the systolic part of the waveform. Third, mean blood flow was entered, enabling the program to compute individual parameters. This program was tested on 200 computer-generated arterial pressure signals, obtained by simulating the model with random but bounded parameters. Correlation between estimated parameters with those actually used in the simulations was excellent. Even though the value of this computer simulation i...
References: [1] van Vaals et al. JMRI 3,4 (1993); [2] Jones et al.MRM 29,6 (1993); [3] Tsao et al... more References: [1] van Vaals et al. JMRI 3,4 (1993); [2] Jones et al.MRM 29,6 (1993); [3] Tsao et al. MRM 50,5 (2003); [4] Madore et al.MRM 42,5 (1999); [5] d'Arcy et al. NMR 15 (2002); [6] Irarrazaval et al. MRM 54,5 (2005); [7] ESMRMB 2008 pp. Fig. 2. RMS errors as a function of time for TRIO with intensity order estimated from Keyhole, k-t BLAST and Sliding Window, compared against the first reconstructions
Magnetic …, 2005
In 3D MRI, sampling k-space with traditional trajectories can be excessively time-consuming. Fast... more In 3D MRI, sampling k-space with traditional trajectories can be excessively time-consuming. Fast imaging trajectories are used in an attempt to efficiently cover the k-space and reduce the scan time without significantly affecting the image quality. In many applications, further ...
Monthly Notices of the Royal Astronomical Society, 2015
Computers in Cardiology 1994, 1995
An interactive scheme for the development of a fuzzy logic based model has been implemented and a... more An interactive scheme for the development of a fuzzy logic based model has been implemented and applied to build a model that is able to determine cardiac output from radial arterial pressure. It was built using as input radial pressure waveforms from patients in whom cardiac output was simultaneously measured by thermodilution. The scheme was programmed in C language in
Journal of clinical monitoring and computing, 1999
Intensive care and operating room monitors generate data that are not fully utilized. False alarm... more Intensive care and operating room monitors generate data that are not fully utilized. False alarms are so frequent that attending personnel tends to disconnect them. We developed an expert system that could select and validate alarms by integration of seven vital signs monitored on-line from cardiac surgical patients. The system uses fuzzy logic and is able to work under incomplete or noisy information conditions. Patient status is inferred every 2 seconds from the analysis and integration of the variables and a unified alarm message is displayed on the screen. The proposed structure was implemented on a personal computer for simultaneous automatic surveillance of up to 9 patients. The system was compared with standard monitors (SpaceLabs PC2), using their default alarm settings. Twenty patients undergoing cardiac surgery were studied, while we ran our system and the standard monitor simultaneously. The number of alarms triggered by each system and their accuracy and relevance were ...
Journal of clinical monitoring and computing, 1998
We propose that it is possible to estimate cardiovascular parameters from the arterial pressure w... more We propose that it is possible to estimate cardiovascular parameters from the arterial pressure waveform, including ventricular maximal elastance and end-diastolic volume, if cardiac output is also known. We tested this hypothesis by means of a parameter estimation algorithm applied to simulated arterial pressure signals. The program first estimated three coefficients representing products of passive parameters from the diastolic part of the simulated arterial pressure waveform. Second, it estimated three parameter products pertaining to the ventricular function from the systolic part of the waveform. Third, mean blood flow was entered, enabling the program to compute individual parameters. This program was tested on 200 computer-generated arterial pressure signals, obtained by simulating the model with random but bounded parameters. Correlation between estimated parameters with those actually used in the simulations was excellent. Even though the value of this computer simulation i...