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Gustavo Piriz

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Óscar I Salazar Arenas

Universidad Nacional de Colombia (National University of Colombia)

Diego Arango Lopez

Universidad Católica del Maule

Nancy BALLESTAS CARO

Politécnico Grancolombiano

Ariel Ivan Diaz

Institut polytechnique de Grenoble - Grenoble INP

Juan Camilo Contreras Jaramillo

Pontificia Universidad Javeriana

ITM - Instituto Tecnológico Metropolitano

Inés de Torres

Universidad de la República (Uruguay)

William GÓMEZ RIVERA

Universidad Militar de Nueva Granada

Boston University

University of Mumbai

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Papers by Gustavo Piriz

Dwell time in uterus and vagina as parameter to analyze the dose distribution in cervix carcinoma for brachytherapy with Co-60 source. Clinical cases

Revista Brasileira de Física Médica, Sep 11, 2022

Intracavitary gynecological brachytherapy uses as a guideline for dose distribution, the ratio be... more Intracavitary gynecological brachytherapy uses as a guideline for dose distribution, the ratio between the pear length in the three directions of the axes considers at ICRU 38. The ratios h/w, h/t function as a parameter to find out how the uterus and vagina are covered by the prescription dose. This work correlates these ratios with the dwell times inside the uterus (tu) and vagina (tv) expecting to identify these times as criteria for the dose shape distribution. We performed an optimized treatment planning for 120 sessions of 6.0 Gy each, following the recommendations of the ABS, ICRU 38, and 89. The planning system used is HDRplus 3.0.4 with an HDR Eckert y Ziegler BEBIG Co0.A86 brachytherapy unit with Cobalt 60. Considering the tandem time modulation and the time differences between left and right irradiation in the vagina, the variation of the correlation with the number of sessions for the tu/tv ratio with h/w and h/t was studied. A correlation has been found between tu/tv with h/w and h/t, which depends on the amount of data. There is a good correlation between the tu/tv ratio with h/w and h/t respectively, which is stronger for the first one.

Correlación entre las razones de los tiempos de permanencia de la fuente de braquiterapia con los volúmenes de restricción de dosis en tratamientos de cáncer cervicouterino

SALUD MILITAR

Correlation between ratios of brachytherapy source dwell times to dose restriction volumes in cer... more Correlation between ratios of brachytherapy source dwell times to dose restriction volumes in cervical cancer treatments RESUMEN Objetivos: El cáncer cervicouterino es tratado tradicionalmente con radioterapia preocupándose de dar una dosis de radiación alta al tumor manteniendo los órganos sanos con la menor dosis posible. La radioterapia en estos tratamientos se hace comúnmente en dos fases, teleterapia y braquiterapia, necesitándose sumar las dosis dadas en cada una de ellas tanto para el tumor como para los tejidos sanos. En la etapa de braquiterapia se forman isodosis a partir de los tiempos de permanencia de la fuente al interior

Fricke dosimetry study for dose ranges used in radiotherapy

Physica Medica, 2021

Artigo Original

Validation of a cylindrical phantom for verification of radiotherapy treatments in head and neck ... more

Implementation of intraoperative radiotherapy in a linear accelerator VARIAN 21EX

The aim of this paper is to present the experience on intraoperative radiotherapy, which has as t... more The aim of this paper is to present the experience on intraoperative radiotherapy, which has as the reference center the network of radiotherapy in Chile. It is detailed the construction of a system of applicators with an easy coupling on a linear accelerator collimator. It is also detailed the cost and the measurements set up with their corresponding percentage depth dose and isodose curves. This technique was implemented in a Varian Clinac 21EX for beams with 6, 9 and 12 MeV electron energy. The coupling system provides a good dose distribution both laterally and in depth for different energies. This provides a good coverage of treatment planning volume.

SU‐F‐T‐31: Shape and Isodose Distributions in Co60 HDR Brachytherapy for Different Utero‐Vaginal Time Ratios

Medical Physics, 2016

Purpose:To optimize the dose in bladder and rectum and show the different shapes of the isodose v... more Purpose:To optimize the dose in bladder and rectum and show the different shapes of the isodose volumes in Co60‐HDR brachytherapy, considering different utero and vaginal sources dwell ratio times (TU:TV).Methods:Besides Ir192‐HDR, new Co60‐HDR sources are being incorporated. We considered different TU:TV times and computed the dosis in bladder, rectum and at the reference points of the Manchester system. Also, we calculated the isodose volume and shape in each case. We used a EZAG‐BEBIG Co0.A86 model with TPS HDRplus3.0.4. and LCT42‐7, LCT42‐2(R,L) applicators. A reference dose RA= 1.00 Gy was given to the A‐right point. We considered the TU:TV dwell time ratios 1:0.25, 1:0.33, 1:0.5, 1:1, 1:2, 1:3, and 1:4. Given TU:TV, the stop time at each dwell position is fixed for each applicator.Results:Increasing TU:TV systematically results in a decreasing of the dose in bladder and rectum, e.g. 9% and 27% reduction were found in 1:0.25 with respect to 1:1, while 12% and 34% increase were ...

Validation of a cylindrical phantom for verification of radiotherapy treatments in head and neck with special techniques

Verification of radiotherapy treatments in head and neck requires, among other things, small volu... more Verification of radiotherapy treatments in head and neck requires, among other things, small volume chambers and a phantom to reproduce the geometry and density of the anatomical structure. New documents from the ICRU (International Comission on Radiation Units & Measurements), Report 83, established the need for quality control in radiotherapy with special techniques such as IMRT (intensity-modulated radiation therapy). In this study, we built a cylindrical acrylic phantom with standing water, containing seven measuring points in the transverse plane and free location (0-20 cm) in the longitudinal plane. These points of measurement are constituted by cavities for the accommodation of the ionization chamber of 7 mm of mayor diameter (semiflex, pinpoint with build cup). The results of the phantom validation yielded percentage differences less than 1% in fixed beams and less than 2.5% in arc therapy for TPS Eclipse calculation. The preparation of this phantom, particularly made to ver...

Main Features for a New Radiotherapy Device Based on a Single Convergent Beam of Photons (RTHC)

A new radiotherapy technique based on a single convergent photons beam (RTHC: Radioterapia de Haz... more A new radiotherapy technique based on a single convergent photons beam (RTHC: Radioterapia de Haz Convergente) by means of a device capable to generate a single beam of convergent X photons has been proposed. Previous studies have shown that a primary beam of these characteristics provides excellent dosimetric results with a dose peak close to the isocenter, similar those used for hadron therapy treatment. To determine the physical and dosimetric characteristics of a device convergent X photons beam and its potential to be used in clinical treatments. Analytical developments plus software that allows determining the necessary fields (electrostatic and/or magnetic fields) for electrons trajectory control are used. Monte Carlo simulation code (PENELOPE) is applied to a specially designed geometry for the generation of a convergent photons beam. We determined the values of the magnetic and/or electric fields to handle the convergent beam device for an electrons’ energy range from 0.1 t...

Quality assurance tool for determination of position and transit time of a Co-60 source in high dose rate brachytherapy

Applied Radiation and Isotopes, 2021

In this study, three holders were designed, constructed and characterized to perform quality assu... more In this study, three holders were designed, constructed and characterized to perform quality assurance on the source position and transit time in remote afterloading systems with Co-60 sources for high dose rate brachytherapy. The holders design focused on achieving accuracy, low cost, and a time efficient tool for use in clinical settings. Sensitivities greater than 0.6%/mm and maximum precisions better than 0.14 mm for the source position were obtained. The transit time was determined for the holders with a relative precision better than 19%.

Analysis in organs at risk for gynecological radiotherapy by High Dose Rate Brachytherapy using Manchester point A, ICRU 38 Report and American Braquitherapy Society recomendation

Brazilian Journal of Radiation Sciences, May 6, 2018

The gynecological treatment with High Dose Rate (HDR) Brachytherapy implies delivering dose to th... more The gynecological treatment with High Dose Rate (HDR) Brachytherapy implies delivering dose to the tumor and spare the dose in organs at risk. In this work, we apply the recommendations for prescribing dose given by the International Commission of Radiation Units (ICRU) reports 38, 89 and the American Brachytherapy Society (ABS). With both schemes of optimization, recommendation of ICRU 38 or ABS with vaginal point from ICRU 89. Doses received by the organs at risk were analyzws, in this case rectum and bladder and also the irradiated volume for patients that receive HDR brachytherapy treatment. An afterloading technique is applied with an Eckert & Ziegler MultiSource ® equipment using a 60 Co source, 30 patients with 4 applications with cervical cancer are planning with HDR brachytherapy. This work analyzes 120 single applications with orthogonal images using the treatment planning system (TPS) HDRplus version 3.0.4 through "Auto dwell time determination" optimization method, using the recommendation for optimization dose from the ABS and vaginal point from ICRU 89 . The volume of the isodose curve of prescription is 15% less using ABS recommendation than ICRU 38. The bladder dose is 11% and rectum dose is 21% less using ABS recommendation than ICRU 38. The analysis of dose prescription using ICRU 38 and ABS recommendations in the patients analyzed shows less irradiated volume at the dose prescribed and also less mean dose in rectum and bladder of applications using ABS in contrast with ICRU 38 recommendations.

Brachytherapy treatment planning commissioning: effect of the election of proper bibliography and finite size of TG-43 input data on standard treatments

Journal of applied clinical medical physics / American College of Medical Physics, Jul 8, 2015

The aim of this work is to evaluate the performance of a commercial brachytherapy treatment plann... more The aim of this work is to evaluate the performance of a commercial brachytherapy treatment planning system (TPS) with TG-43 Vendors Input Data (VID), analyze possible discrepancies with respect to a proper reference source and its implications for standard treatments, and judge the effectiveness of certain widespread recommended quality controls to find potential errors related with the interpolations of TG-43 VID tables. The TPS evaluated was a BrachyVision 8.6 loaded with TG-43 VID for a VariSource high-dose-rate 192Ir source (Vs2000). The reference data chosen were the TG-43 data published in the literature. In the first step, we compared TG-43 VID with respect to the chosen reference data. Next, we used percent dose-rate differences in a point array matrix to compare the outcomes of the TPS on standard treatment setup with respect to an in-house developed program (MATLAB R2009a-based) loaded with the chosen full TG-43 reference data. The cases with major discrepancies were eval...

Incorporación de la corrección por el ángulo de incidencia al método de Sherouse

El proceso de planificación dosimétrica de un tratamiento de radioterapia requiere del conocimien... more El proceso de planificación dosimétrica de un tratamiento de radioterapia requiere del conocimiento de numerosos parámetros que influyen directamente en el resultado que se quiere lograr. Un procedimiento de gran utilidad consiste en hacer un análisis vectorial de los gradientes de dosis que generan los haces de irradiación y de esta forma determinar, por ejemplo, el ángulo de filtro cuña que se requiere para obtener una distribución de dosis homogénea. Este método matemático de cálculo lo replanteó G. Sherouse 1 para la elección de cuñas, rotación de colimador y pesos relativos de los campos de tratamiento, pudiendo aplicarse a haces estáticos co-planares y no coplanares, pero sin considerar el gradiente generado por el ángulo de incidencia del haz. El método es aplicable a un número arbitrario de haces que se cruzan para lograr la máxima homogeneidad de dosis en el volumen de intersección. Consiste en un análisis matemático de los gradientes de dosis de cada uno de los haces, cuyas bases

Measurement of SO2and NO2applying ToTaL-DOAS from a remote site

Journal of Optics A: Pure and Applied Optics, 2008

ABSTRACT The concentration and diurnal variation of SO2 and NO2 were remotely measured in a main ... more ABSTRACT The concentration and diurnal variation of SO2 and NO2 were remotely measured in a main street of Montevideo using a recently proposed experimental procedure called topographic target light scattering differential optical absorption spectroscopy (ToTaL-DOAS). Our instrument was placed on the roof of a building 3 km away from the measured site. We give a general description of the procedure and present the first results of the 2006 campaign at Montevideo.

Spatial self-filtering with polarizer sheets

Applied Optics, 2005

A method for phase visualization and edge enhancement by spatial self-filtering by use of a polar... more A method for phase visualization and edge enhancement by spatial self-filtering by use of a polarizer sheet in the Fourier plane of an optical processor is described. Light absorbed by the polarizer sheet induces a thermal lens, which, in turn, produces selective action on certain spatial frequencies of the image to be processed. Some experiments that demonstrate the self-filtering action of the proposed system are presented.

Differential optical absorption spectroscopy (DOAS) system for urban atmospheric pollution monitoring

Applied Optics, 1993

We describe a fully computer-controlled differential optical absorption spectroscopy system for a... more We describe a fully computer-controlled differential optical absorption spectroscopy system for atmospheric air pollution monitoring. A receiving optical telescope can sequentially tune in to light beams from a number of distant high-pressure Xe lamp light sources to cover the area of a medium-sized city. A beam-finding servosystem and automatic gain control permit unattended long-time monitoring. Using an astronomical code, we can also search and track celestial sources. Selected wavelength regions are rapidly and repetitively swept by a monochromator to sensitively record the atmospheric absorption spectrum while avoiding the detrimental effects of atmospheric turbulence. By computer fitting to stored laboratory spectra, we can evaluate the path-averaged concentration of a number of important pollutants such as NO 2 , SO 2 , and 03. A measurement of NH 3 and NO close to the UV limit is also demonstrated.

Dwell time in uterus and vagina as parameter to analyze the dose distribution in cervix carcinoma for brachytherapy with Co-60 source. Clinical cases

Revista Brasileira de Física Médica, Sep 11, 2022

Intracavitary gynecological brachytherapy uses as a guideline for dose distribution, the ratio be... more Intracavitary gynecological brachytherapy uses as a guideline for dose distribution, the ratio between the pear length in the three directions of the axes considers at ICRU 38. The ratios h/w, h/t function as a parameter to find out how the uterus and vagina are covered by the prescription dose. This work correlates these ratios with the dwell times inside the uterus (tu) and vagina (tv) expecting to identify these times as criteria for the dose shape distribution. We performed an optimized treatment planning for 120 sessions of 6.0 Gy each, following the recommendations of the ABS, ICRU 38, and 89. The planning system used is HDRplus 3.0.4 with an HDR Eckert y Ziegler BEBIG Co0.A86 brachytherapy unit with Cobalt 60. Considering the tandem time modulation and the time differences between left and right irradiation in the vagina, the variation of the correlation with the number of sessions for the tu/tv ratio with h/w and h/t was studied. A correlation has been found between tu/tv with h/w and h/t, which depends on the amount of data. There is a good correlation between the tu/tv ratio with h/w and h/t respectively, which is stronger for the first one.

Correlación entre las razones de los tiempos de permanencia de la fuente de braquiterapia con los volúmenes de restricción de dosis en tratamientos de cáncer cervicouterino

SALUD MILITAR

Correlation between ratios of brachytherapy source dwell times to dose restriction volumes in cer... more Correlation between ratios of brachytherapy source dwell times to dose restriction volumes in cervical cancer treatments RESUMEN Objetivos: El cáncer cervicouterino es tratado tradicionalmente con radioterapia preocupándose de dar una dosis de radiación alta al tumor manteniendo los órganos sanos con la menor dosis posible. La radioterapia en estos tratamientos se hace comúnmente en dos fases, teleterapia y braquiterapia, necesitándose sumar las dosis dadas en cada una de ellas tanto para el tumor como para los tejidos sanos. En la etapa de braquiterapia se forman isodosis a partir de los tiempos de permanencia de la fuente al interior

Fricke dosimetry study for dose ranges used in radiotherapy

Physica Medica, 2021

Artigo Original

Validation of a cylindrical phantom for verification of radiotherapy treatments in head and neck ... more

Implementation of intraoperative radiotherapy in a linear accelerator VARIAN 21EX

The aim of this paper is to present the experience on intraoperative radiotherapy, which has as t... more The aim of this paper is to present the experience on intraoperative radiotherapy, which has as the reference center the network of radiotherapy in Chile. It is detailed the construction of a system of applicators with an easy coupling on a linear accelerator collimator. It is also detailed the cost and the measurements set up with their corresponding percentage depth dose and isodose curves. This technique was implemented in a Varian Clinac 21EX for beams with 6, 9 and 12 MeV electron energy. The coupling system provides a good dose distribution both laterally and in depth for different energies. This provides a good coverage of treatment planning volume.

SU‐F‐T‐31: Shape and Isodose Distributions in Co60 HDR Brachytherapy for Different Utero‐Vaginal Time Ratios

Medical Physics, 2016

Purpose:To optimize the dose in bladder and rectum and show the different shapes of the isodose v... more Purpose:To optimize the dose in bladder and rectum and show the different shapes of the isodose volumes in Co60‐HDR brachytherapy, considering different utero and vaginal sources dwell ratio times (TU:TV).Methods:Besides Ir192‐HDR, new Co60‐HDR sources are being incorporated. We considered different TU:TV times and computed the dosis in bladder, rectum and at the reference points of the Manchester system. Also, we calculated the isodose volume and shape in each case. We used a EZAG‐BEBIG Co0.A86 model with TPS HDRplus3.0.4. and LCT42‐7, LCT42‐2(R,L) applicators. A reference dose RA= 1.00 Gy was given to the A‐right point. We considered the TU:TV dwell time ratios 1:0.25, 1:0.33, 1:0.5, 1:1, 1:2, 1:3, and 1:4. Given TU:TV, the stop time at each dwell position is fixed for each applicator.Results:Increasing TU:TV systematically results in a decreasing of the dose in bladder and rectum, e.g. 9% and 27% reduction were found in 1:0.25 with respect to 1:1, while 12% and 34% increase were ...

Validation of a cylindrical phantom for verification of radiotherapy treatments in head and neck with special techniques

Verification of radiotherapy treatments in head and neck requires, among other things, small volu... more Verification of radiotherapy treatments in head and neck requires, among other things, small volume chambers and a phantom to reproduce the geometry and density of the anatomical structure. New documents from the ICRU (International Comission on Radiation Units & Measurements), Report 83, established the need for quality control in radiotherapy with special techniques such as IMRT (intensity-modulated radiation therapy). In this study, we built a cylindrical acrylic phantom with standing water, containing seven measuring points in the transverse plane and free location (0-20 cm) in the longitudinal plane. These points of measurement are constituted by cavities for the accommodation of the ionization chamber of 7 mm of mayor diameter (semiflex, pinpoint with build cup). The results of the phantom validation yielded percentage differences less than 1% in fixed beams and less than 2.5% in arc therapy for TPS Eclipse calculation. The preparation of this phantom, particularly made to ver...

Main Features for a New Radiotherapy Device Based on a Single Convergent Beam of Photons (RTHC)

A new radiotherapy technique based on a single convergent photons beam (RTHC: Radioterapia de Haz... more A new radiotherapy technique based on a single convergent photons beam (RTHC: Radioterapia de Haz Convergente) by means of a device capable to generate a single beam of convergent X photons has been proposed. Previous studies have shown that a primary beam of these characteristics provides excellent dosimetric results with a dose peak close to the isocenter, similar those used for hadron therapy treatment. To determine the physical and dosimetric characteristics of a device convergent X photons beam and its potential to be used in clinical treatments. Analytical developments plus software that allows determining the necessary fields (electrostatic and/or magnetic fields) for electrons trajectory control are used. Monte Carlo simulation code (PENELOPE) is applied to a specially designed geometry for the generation of a convergent photons beam. We determined the values of the magnetic and/or electric fields to handle the convergent beam device for an electrons’ energy range from 0.1 t...

Quality assurance tool for determination of position and transit time of a Co-60 source in high dose rate brachytherapy

Applied Radiation and Isotopes, 2021

In this study, three holders were designed, constructed and characterized to perform quality assu... more In this study, three holders were designed, constructed and characterized to perform quality assurance on the source position and transit time in remote afterloading systems with Co-60 sources for high dose rate brachytherapy. The holders design focused on achieving accuracy, low cost, and a time efficient tool for use in clinical settings. Sensitivities greater than 0.6%/mm and maximum precisions better than 0.14 mm for the source position were obtained. The transit time was determined for the holders with a relative precision better than 19%.

Analysis in organs at risk for gynecological radiotherapy by High Dose Rate Brachytherapy using Manchester point A, ICRU 38 Report and American Braquitherapy Society recomendation

Brazilian Journal of Radiation Sciences, May 6, 2018

The gynecological treatment with High Dose Rate (HDR) Brachytherapy implies delivering dose to th... more The gynecological treatment with High Dose Rate (HDR) Brachytherapy implies delivering dose to the tumor and spare the dose in organs at risk. In this work, we apply the recommendations for prescribing dose given by the International Commission of Radiation Units (ICRU) reports 38, 89 and the American Brachytherapy Society (ABS). With both schemes of optimization, recommendation of ICRU 38 or ABS with vaginal point from ICRU 89. Doses received by the organs at risk were analyzws, in this case rectum and bladder and also the irradiated volume for patients that receive HDR brachytherapy treatment. An afterloading technique is applied with an Eckert & Ziegler MultiSource ® equipment using a 60 Co source, 30 patients with 4 applications with cervical cancer are planning with HDR brachytherapy. This work analyzes 120 single applications with orthogonal images using the treatment planning system (TPS) HDRplus version 3.0.4 through "Auto dwell time determination" optimization method, using the recommendation for optimization dose from the ABS and vaginal point from ICRU 89 . The volume of the isodose curve of prescription is 15% less using ABS recommendation than ICRU 38. The bladder dose is 11% and rectum dose is 21% less using ABS recommendation than ICRU 38. The analysis of dose prescription using ICRU 38 and ABS recommendations in the patients analyzed shows less irradiated volume at the dose prescribed and also less mean dose in rectum and bladder of applications using ABS in contrast with ICRU 38 recommendations.

Brachytherapy treatment planning commissioning: effect of the election of proper bibliography and finite size of TG-43 input data on standard treatments

Journal of applied clinical medical physics / American College of Medical Physics, Jul 8, 2015

The aim of this work is to evaluate the performance of a commercial brachytherapy treatment plann... more The aim of this work is to evaluate the performance of a commercial brachytherapy treatment planning system (TPS) with TG-43 Vendors Input Data (VID), analyze possible discrepancies with respect to a proper reference source and its implications for standard treatments, and judge the effectiveness of certain widespread recommended quality controls to find potential errors related with the interpolations of TG-43 VID tables. The TPS evaluated was a BrachyVision 8.6 loaded with TG-43 VID for a VariSource high-dose-rate 192Ir source (Vs2000). The reference data chosen were the TG-43 data published in the literature. In the first step, we compared TG-43 VID with respect to the chosen reference data. Next, we used percent dose-rate differences in a point array matrix to compare the outcomes of the TPS on standard treatment setup with respect to an in-house developed program (MATLAB R2009a-based) loaded with the chosen full TG-43 reference data. The cases with major discrepancies were eval...

Incorporación de la corrección por el ángulo de incidencia al método de Sherouse

El proceso de planificación dosimétrica de un tratamiento de radioterapia requiere del conocimien... more El proceso de planificación dosimétrica de un tratamiento de radioterapia requiere del conocimiento de numerosos parámetros que influyen directamente en el resultado que se quiere lograr. Un procedimiento de gran utilidad consiste en hacer un análisis vectorial de los gradientes de dosis que generan los haces de irradiación y de esta forma determinar, por ejemplo, el ángulo de filtro cuña que se requiere para obtener una distribución de dosis homogénea. Este método matemático de cálculo lo replanteó G. Sherouse 1 para la elección de cuñas, rotación de colimador y pesos relativos de los campos de tratamiento, pudiendo aplicarse a haces estáticos co-planares y no coplanares, pero sin considerar el gradiente generado por el ángulo de incidencia del haz. El método es aplicable a un número arbitrario de haces que se cruzan para lograr la máxima homogeneidad de dosis en el volumen de intersección. Consiste en un análisis matemático de los gradientes de dosis de cada uno de los haces, cuyas bases

Measurement of SO2and NO2applying ToTaL-DOAS from a remote site

Journal of Optics A: Pure and Applied Optics, 2008

ABSTRACT The concentration and diurnal variation of SO2 and NO2 were remotely measured in a main ... more ABSTRACT The concentration and diurnal variation of SO2 and NO2 were remotely measured in a main street of Montevideo using a recently proposed experimental procedure called topographic target light scattering differential optical absorption spectroscopy (ToTaL-DOAS). Our instrument was placed on the roof of a building 3 km away from the measured site. We give a general description of the procedure and present the first results of the 2006 campaign at Montevideo.

Spatial self-filtering with polarizer sheets

Applied Optics, 2005

A method for phase visualization and edge enhancement by spatial self-filtering by use of a polar... more A method for phase visualization and edge enhancement by spatial self-filtering by use of a polarizer sheet in the Fourier plane of an optical processor is described. Light absorbed by the polarizer sheet induces a thermal lens, which, in turn, produces selective action on certain spatial frequencies of the image to be processed. Some experiments that demonstrate the self-filtering action of the proposed system are presented.

Differential optical absorption spectroscopy (DOAS) system for urban atmospheric pollution monitoring

Applied Optics, 1993

We describe a fully computer-controlled differential optical absorption spectroscopy system for a... more We describe a fully computer-controlled differential optical absorption spectroscopy system for atmospheric air pollution monitoring. A receiving optical telescope can sequentially tune in to light beams from a number of distant high-pressure Xe lamp light sources to cover the area of a medium-sized city. A beam-finding servosystem and automatic gain control permit unattended long-time monitoring. Using an astronomical code, we can also search and track celestial sources. Selected wavelength regions are rapidly and repetitively swept by a monochromator to sensitively record the atmospheric absorption spectrum while avoiding the detrimental effects of atmospheric turbulence. By computer fitting to stored laboratory spectra, we can evaluate the path-averaged concentration of a number of important pollutants such as NO 2 , SO 2 , and 03. A measurement of NH 3 and NO close to the UV limit is also demonstrated.