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Vladimir Feygelman - One of the best experts on this subject based on the ideXlab platform.
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optimizing the accuracy of a helical diode array dosimeter a comprehensive calibration methodology coupled with a novel virtual inclinometer
Medical Physics, 2011Co-Authors: Jakub Kozelka, Geoffrey Zhang, Joshua Robinson, Benjamin E Nelms, Dennis Savitskij, Vladimir FeygelmanAbstract:Purpose: The goal of any dosimeter is to be as accurate as possible when measuring absolute dose to compare with calculated dose. This limits the uncertainties associated with the dosimeter itself and allows the task of dose QA to focus on detecting errors in the treatment planning (TPS) and/or Delivery systems. This work introduces enhancements to the measurement accuracy of a 3D dosimeter comprised of a helical plane of diodes in a volumetric phantom. Methods: We describe the methods and derivations of new corrections that account for repetition rate dependence, intrinsic relative sensitivity per diode, field size dependence based on the dynamic field size determination, and positional correction. Required and described is an accurate “virtual inclinometer” algorithm. The system allows for calibrating the array directly against an ion chamber signal collected with high angular resolution. These enhancements are quantitatively validated using several strategies including ion chamber measurements taken using a “blank” plastic shell mimicking the actual phantom, and comparison to high resolution dose calculations for a variety of fields: static, simple arcs, and VMAT. A number of sophisticated treatment planning algorithms were benchmarked against ion chamber measurements for their ability to handle a large air cavity in the phantom. Results: Each calibration correction is quantified and presented vs its independent variable(s). The virtual inclinometer is validated by direct comparison to the gantry angle vs time data from machine log files. The effects of the calibration are quantified and improvements are seen in the dose agreement with the ion chamber reference measurements and with the TPS calculations. These improved agreements are a result of removing prior limitations and assumptions in the calibration methodology. Average gamma analysis passing rates for VMAT plans based on the AAPM TG-119 report are 98.4 and 93.3% for the 3%/3 mm and 2%/2 mm dose-error/distance to agreement threshold criteria, respectively, with the global dose-error normalization. With the local dose-error normalization, the average passing rates are reduced to 94.6 and 85.7% for the 3%/3 mm and 2%/2 mm criteria, respectively. Some algorithms in the convolution/superposition family are not sufficiently accurate in predicting the exit dose in the presence of a 15 cm diameter air cavity. Conclusions: Introduction of the improved calibration methodology, enabled by a robust virtual inclinometer algorithm, improves the accuracy of the dosimeter’s absolute dose measurements. With our treatment planning and Delivery Chain, gamma analysis passing rates for the VMAT plans based on the AAPM TG-119 report are expected to be above 91% and average at about 95% level for γ(3%/3 mm) with the local dose-error normalization. This stringent comparison methodology is more indicative of the true VMAT system commissioning accuracy compared to the often quoted dose-error normalization to a single high value.
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initial dosimetric evaluation of smartarc a novel vmat treatment planning module implemented in a multi vendor Delivery Chain
Journal of Applied Clinical Medical Physics, 2010Co-Authors: Vladimir Feygelman, Geoffrey Zhang, Craig W StevensAbstract:We performed an initial dosimetric evaluation of SmartArc - a novel VMAT planning module for Philips Pinnacle treatment planning system. A test suite of structure sets and dose objectives provided by the AAPM for multi-institutional comparison of IMRT dosimetry was used. A total of fifty plans were successfully delivered. The effect of control point spacing on dosimetric accuracy was investigated. When calculated with the 4o spacing, the overall mean point dose errors measured with an ion chamber were 0.5±1.4 and -0.3±1.4% for the PTV and OAR, respectively. The γ(3%,3mm) passing rate, measured for absolute dose with a biplanar diode array, was 98.2±1.6% (range 94.5-99.9%). Ninety percent of the passing rate values were above 97.7%. With the 6o control point spacing, the highly modulated plans exhibited large dosimetric errors, while the results were still acceptable for the simpler cases. The data show that the practical accuracy of the small-arc approximation, which is at the heart of VMAT dose calculations, depends not only on the control point spacing, but also on the size and relative position of the MLC openings corresponding to the consecutive control points. The effect of the minimum allowed separation between the opposing leaves was found to be minimal. It appears that 4o control point spacing may be a good compromise between calculation speed and accuracy. However each institution is encouraged to establish its own treatment planning guidelines based on the case complexity and acceptable error level.
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initial dosimetric evaluation of smartarc a novel vmat treatment planning module implemented in a multi vendor Delivery Chain
Journal of Applied Clinical Medical Physics, 2010Co-Authors: Vladimir Feygelman, Geoffrey Zhang, Craig W StevensAbstract:We performed an initial dosimetric evaluation of SmartArc - a novel VMAT planning module for Philips Pinnacle treatment planning system. A test suite of structure sets and dose objectives provided by the AAPM for multi-institutional comparison of IMRT dosimetry was used. A total of fifty plans were successfully delivered. The effect of control point spacing on dosimetric accuracy was investigated. When calculated with the 4 masculine spacing, the overall mean point dose errors measured with an ion chamber were 0.5+/-1.4 and -0.3+/-1.4% for the PTV and OAR, respectively. The gamma(3%,3mm) passing rate, measured for absolute dose with a biplanar diode array, was 98.2+/-1.6% (range 94.5-99.9%). Ninety percent of the passing rate values were above 97.7%. With the 6 masculine control point spacing, the highly modulated plans exhibited large dosimetric errors, while the results were still acceptable for the simpler cases. The data show that the practical accuracy of the small-arc approximation, which is at the heart of VMAT dose calculations, depends not only on the control point spacing, but also on the size and relative position of the MLC openings corresponding to the consecutive control points. The effect of the minimum allowed separation between the opposing leaves was found to be minimal. It appears that 4 masculine control point spacing may be a good compromise between calculation speed and accuracy. However each institution is encouraged to establish its own treatment planning guidelines based on the case complexity and acceptable error level.
Tamara L Kinzerursem - One of the best experts on this subject based on the ideXlab platform.
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measuring biotherapeutic viscosity and degradation on chip with particle diffusometry
Lab on a Chip, 2017Co-Authors: Katherine N Clayton, Dong Hoon Lee, Steven T Wereley, Tamara L KinzerursemAbstract:In the absence of efficient ways to test drug stability and efficacy, pharmaceuticals that have been stored outside of set temperature conditions are destroyed, often at great cost. This is especially problematic for biotherapeutics, which are highly sensitive to temperature fluctuations. Current platforms for assessing the stability of protein-based biotherapeutics in high throughput and in low volumes are unavailable outside of research and development laboratories and are not efficient for use in production, quality control, distribution, or clinical settings. In these alternative environments, microanalysis platforms could provide significant advantages for the characterization of biotherapeutic degradation. Here we present particle diffusometry (PD), a new technique to study degradation of biotherapeutic solutions. PD uses a simple microfluidic chip and microscope setup to calculate the Brownian motion of particles in a quiescent solution using a variation of particle image velocimetry (PIV) fundamentals. We show that PD can be used to measure the viscosity of protein solutions to discriminate native protein from degraded samples as well as to determine the change in viscosity as a function of therapeutic concentration. PD viscosity analysis is applied to two particularly important biotherapeutic preparations: insulin, a commonly used protein for diabetic patients, and monoclonal antibodies which are an emerging class of biotherapeutics used to treat a variety of diseases such as autoimmune disorders and cancer. PD-based characterization of solution viscosity is a new tool for biotherapeutic analysis, and owing to its easy setup could readily be implemented at key points of the pharmaceutical Delivery Chain and in clinical settings.
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measuring biotherapeutic viscosity and degradation on chip with particle diffusometry
bioRxiv, 2017Co-Authors: Katherine N Clayton, Dong Hoon Lee, Steven T Wereley, Tamara L KinzerursemAbstract:In absence of efficient ways to test drug stability and efficacy, pharmaceuticals that have been stored outside of set temperature conditions are destroyed, often at great cost. This is especially problematic for biotherapeutics, which are highly sensitive to temperature fluctuations. Current platforms for assessing the stability of protein-based biotherapeutics in high throughput and in low volumes are unavailable outside of research and development laboratories and are not efficient for use in production, quality control, distribution, or clinical settings. In these alternative environments, microanalysis platforms could provide significant advantages for the characterization of biotherapeutic degradation. Here we present particle diffusometry (PD), a new technique to study degradation of biotherapeutic solutions. PD uses a simple microfluidic chip and microscope setup to calculate the Brownian motion of particles in a quiescent solution using a variation of particle image velocimetry (PIV) fundamentals. We show that PD can be used to measure the viscosity of protein solutions to discriminate intact protein from degraded samples as well as to determine the change in viscosity as a function of therapeutic concentration. PD viscosity analysis is applied to two particularly important biotherapeutic preparations: insulin, a commonly used protein for diabetic patients, and monoclonal antibodies which are an emerging class of biotherapeutics used to treat a variety of diseases such as autoimmune disorders and cancer. PD-based characterization of solution viscosity is a new tool for biotherapeutic analysis, and owing to its easy setup could readily be implemented at key points of the pharmaceutical Delivery Chain and in clinical settings.
Dharmaputra, Okky S. - One of the best experts on this subject based on the ideXlab platform.
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Fungal Infection in Stored Arabica Coffee (Coffea Arabica) Beans at Various Stages of the Delivery Chain in South Sulawesi Province
Southeast Asian Regional Centre for Tropical Biology, 2019Co-Authors: Dharmaputra, Okky S., Ambarwati S., Nurfadila N.Abstract:Indonesia has retained its status as the world\u27s fourth largest coffee producer after Brazil, Vietnam and Columbia, in which one of its well-known coffee is originated from Toraja region, South Sulawesi. Because of this, Indonesia has to compete with these countries in producing good quality coffee beans. The objectives of this research were (a) to obtain information on the postharvest handling methods of Arabica coffee (C. arabica) beans in Tana Toraja and North Toraja Regencies, and Makassar Municipality, and (b) to investigate the occurrence of fungi (including ochratoxin A producing fungi) in stored Arabica coffee beans collected from various stages of the Delivery Chain. Methods used in this study included surveys, interviews and sample collections in each level of Delivery Chain, which were conducted in May and July 2016. The moisture content and physical quality of the beans were also measured to determine the quality of the beans. The total number of coffee bean samples was 64, consisting of 27 samples from farmers, 15 samples from collectors, 13 samples from traders, and 9 samples from exporters. The results showed that the moisture content of coffee beans collected from farmers and collectors was higher than the maximum tolerable limit determined by SNI (13%), while the moisture content of beans collected from traders and exporters were lower. Based on the total defective value, coffee beans collected from farmers had more diverse grades than those at other levels. Penicillium citrinum was the dominat fungus found in coffee beans collected from farmers, collectors and traders, while Aspergillus Niger was the dominant fungus found in coffee beans collected from exporters. At trader level, 46% of the samples was infected by Aspergillus ochraceus and A. Niger, which are known as OTA-producing fungi. At exporter level, 44% of the samples was infected by A. ochraceus, while 78% of the samples was infected by A. Niger. The postharvest handling methods of Arabica coffee beans conducted especially by farmers and collectors should be improved to minimize moisture content and to increase quality grade of coffee beans
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Fungal Infection and Aflatoxin Contamination in Stored Nutmeg (Myristica fragrans) Kernels at Various Stages of Delivery Chain in North Sulawesi Province
'Seameo Biotrop', 2016Co-Authors: Dharmaputra, Okky S., Ambarwati Santi, Retnowati Ina, Nurfadila NijmaAbstract:ABSTRACTNutmeg (Myristica fragrans Houtt.) or fragrant nutmeg is an important commodity that has been used in food industry and medicine, hence its quality should be monitored. The objectives of the research were to obtain informations on the postharvest handling of nutmeg conducted by farmers, collectors and exporters in North Sulawesi province and to investigate the occurrence of fungi (included A. flavus) and aflatoxin contamination in stored nutmeg collected from farmers, collectors and exporters in North Sulawesi province. Moisture content and percentage of damaged kernels were also investigated, because they affect fungal infection. Surveys and obtaining samples of nutmeg in different points of the Delivery Chain were done in April and May 2013, in three regencies (North Minahasa, Siau Tagulandang Biaro (Sitaro) and Sangihe Talaud) and two cities (Bitung and Manado). Interviews were conducted during the surveys to collect informations on the postharvest handling of nutmeg in different points of the Delivery Chain. The total number of nutmeg samples collected from different point of the Delivery Chain was 76. It consisted of samples collected from farmers (25 samples), collectors (22), and exporters (29). The results showed that in general, the moisture content of nutmeg collected from North Sulawesi province was not higher than the maximum limit of moisture content determineted by SNI (10%). In general, nutmeg collected from farmers and collectors had high percentage of damaged kernels. Aspergillus niger and Endomyces fibuliger were the dominant fungi infecting nutmeg collected from farmers and collectors, while Eurotium repens was the dominant fungus infecting nutmeg collected from exporters. Aflatoxin B1 and total aflatoxin contents in nutmeg collected from farmers and exporters were relatively high. Based on the results of this study, the method of postharvest handling of nutmeg conducted by farmers, collectors and exporters in North Sulawesi province (North Minahasa, Sitaro and Sangihe Talaud regencies, Bitung and Manado cities) should be improved to minimize aflatoxin contamination. Keywords : aflatoxin, fungi, Myristica fragrans Houtt., nutmeg, North Sulawesi province, Delivery Chain
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Fungal Infection and Aflatoxin Contamination in Stored Nutmeg (Myristica Fragrans) Kernels at Various Stages of Delivery Chain in North Sulawesi Province
Southeast Asian Regional Centre for Tropical Biology, 2015Co-Authors: Dharmaputra, Okky S., Ambarwati S., Nurfadila N.Abstract:Nutmeg (Myristica fragrans Houtt.) or fragrant nutmeg is an important commodity that has been used in food industry and medicine, hence its quality should be monitored. The objectives of the research were to obtain informations on the postharvest handling of nutmeg conducted by farmers, collectors and exporters in North Sulawesi province and to investigate the occurrence of fungi (included A. flavus) and aflatoxin contamination in stored nutmeg collected from farmers, collectors and exporters in North Sulawesi province. Moisture content and percentage of damaged kernels were also investigated, because they affect fungal infection. Surveys and obtaining samples of nutmeg in different points of the Delivery Chain were done in April and May 2013, in three regencies (North Minahasa, Siau Tagulandang Biaro (Sitaro) and Sangihe Talaud) and two cities (Bitung and Manado). Interviews were conducted during the surveys to collect informations on the postharvest handling of nutmeg in different points of the Delivery Chain. The total number of nutmeg samples collected from different point of the Delivery Chain was 76. It consisted of samples collected from farmers (25 samples), collectors (22), and exporters (29). The results showed that in general, the moisture content of nutmeg collected from North Sulawesi province was not higher than the maximum limit of moisture content determineted by SNI (10%). In general, nutmeg collected from farmers and collectors had high percentage of damaged kernels. Aspergillus Niger and Endomyces fibuliger were the dominant fungi infecting nutmeg collected from farmers and collectors, while Eurotium repens was the dominant fungus infecting nutmeg collected from exporters. Aflatoxin B1 and total aflatoxin contents in nutmeg collected from farmers and exporters were relatively high. Based on the results of this study, the method of postharvest handling of nutmeg conducted by farmers, collectors and exporters in North Sulawesi province (North Minahasa, Sitaro and Sangihe Talaud regencies, Bitung and Manado cities) should be improved to minimize aflatoxin contamination
Nurfadila N. - One of the best experts on this subject based on the ideXlab platform.
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Fungal Infection in Stored Arabica Coffee (Coffea Arabica) Beans at Various Stages of the Delivery Chain in South Sulawesi Province
Southeast Asian Regional Centre for Tropical Biology, 2019Co-Authors: Dharmaputra, Okky S., Ambarwati S., Nurfadila N.Abstract:Indonesia has retained its status as the world\u27s fourth largest coffee producer after Brazil, Vietnam and Columbia, in which one of its well-known coffee is originated from Toraja region, South Sulawesi. Because of this, Indonesia has to compete with these countries in producing good quality coffee beans. The objectives of this research were (a) to obtain information on the postharvest handling methods of Arabica coffee (C. arabica) beans in Tana Toraja and North Toraja Regencies, and Makassar Municipality, and (b) to investigate the occurrence of fungi (including ochratoxin A producing fungi) in stored Arabica coffee beans collected from various stages of the Delivery Chain. Methods used in this study included surveys, interviews and sample collections in each level of Delivery Chain, which were conducted in May and July 2016. The moisture content and physical quality of the beans were also measured to determine the quality of the beans. The total number of coffee bean samples was 64, consisting of 27 samples from farmers, 15 samples from collectors, 13 samples from traders, and 9 samples from exporters. The results showed that the moisture content of coffee beans collected from farmers and collectors was higher than the maximum tolerable limit determined by SNI (13%), while the moisture content of beans collected from traders and exporters were lower. Based on the total defective value, coffee beans collected from farmers had more diverse grades than those at other levels. Penicillium citrinum was the dominat fungus found in coffee beans collected from farmers, collectors and traders, while Aspergillus Niger was the dominant fungus found in coffee beans collected from exporters. At trader level, 46% of the samples was infected by Aspergillus ochraceus and A. Niger, which are known as OTA-producing fungi. At exporter level, 44% of the samples was infected by A. ochraceus, while 78% of the samples was infected by A. Niger. The postharvest handling methods of Arabica coffee beans conducted especially by farmers and collectors should be improved to minimize moisture content and to increase quality grade of coffee beans
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Fungal Infection and Aflatoxin Contamination in Stored Nutmeg (Myristica Fragrans) Kernels at Various Stages of Delivery Chain in North Sulawesi Province
Southeast Asian Regional Centre for Tropical Biology, 2015Co-Authors: Dharmaputra, Okky S., Ambarwati S., Nurfadila N.Abstract:Nutmeg (Myristica fragrans Houtt.) or fragrant nutmeg is an important commodity that has been used in food industry and medicine, hence its quality should be monitored. The objectives of the research were to obtain informations on the postharvest handling of nutmeg conducted by farmers, collectors and exporters in North Sulawesi province and to investigate the occurrence of fungi (included A. flavus) and aflatoxin contamination in stored nutmeg collected from farmers, collectors and exporters in North Sulawesi province. Moisture content and percentage of damaged kernels were also investigated, because they affect fungal infection. Surveys and obtaining samples of nutmeg in different points of the Delivery Chain were done in April and May 2013, in three regencies (North Minahasa, Siau Tagulandang Biaro (Sitaro) and Sangihe Talaud) and two cities (Bitung and Manado). Interviews were conducted during the surveys to collect informations on the postharvest handling of nutmeg in different points of the Delivery Chain. The total number of nutmeg samples collected from different point of the Delivery Chain was 76. It consisted of samples collected from farmers (25 samples), collectors (22), and exporters (29). The results showed that in general, the moisture content of nutmeg collected from North Sulawesi province was not higher than the maximum limit of moisture content determineted by SNI (10%). In general, nutmeg collected from farmers and collectors had high percentage of damaged kernels. Aspergillus Niger and Endomyces fibuliger were the dominant fungi infecting nutmeg collected from farmers and collectors, while Eurotium repens was the dominant fungus infecting nutmeg collected from exporters. Aflatoxin B1 and total aflatoxin contents in nutmeg collected from farmers and exporters were relatively high. Based on the results of this study, the method of postharvest handling of nutmeg conducted by farmers, collectors and exporters in North Sulawesi province (North Minahasa, Sitaro and Sangihe Talaud regencies, Bitung and Manado cities) should be improved to minimize aflatoxin contamination
Katherine N Clayton - One of the best experts on this subject based on the ideXlab platform.
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measuring biotherapeutic viscosity and degradation on chip with particle diffusometry
Lab on a Chip, 2017Co-Authors: Katherine N Clayton, Dong Hoon Lee, Steven T Wereley, Tamara L KinzerursemAbstract:In the absence of efficient ways to test drug stability and efficacy, pharmaceuticals that have been stored outside of set temperature conditions are destroyed, often at great cost. This is especially problematic for biotherapeutics, which are highly sensitive to temperature fluctuations. Current platforms for assessing the stability of protein-based biotherapeutics in high throughput and in low volumes are unavailable outside of research and development laboratories and are not efficient for use in production, quality control, distribution, or clinical settings. In these alternative environments, microanalysis platforms could provide significant advantages for the characterization of biotherapeutic degradation. Here we present particle diffusometry (PD), a new technique to study degradation of biotherapeutic solutions. PD uses a simple microfluidic chip and microscope setup to calculate the Brownian motion of particles in a quiescent solution using a variation of particle image velocimetry (PIV) fundamentals. We show that PD can be used to measure the viscosity of protein solutions to discriminate native protein from degraded samples as well as to determine the change in viscosity as a function of therapeutic concentration. PD viscosity analysis is applied to two particularly important biotherapeutic preparations: insulin, a commonly used protein for diabetic patients, and monoclonal antibodies which are an emerging class of biotherapeutics used to treat a variety of diseases such as autoimmune disorders and cancer. PD-based characterization of solution viscosity is a new tool for biotherapeutic analysis, and owing to its easy setup could readily be implemented at key points of the pharmaceutical Delivery Chain and in clinical settings.
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measuring biotherapeutic viscosity and degradation on chip with particle diffusometry
bioRxiv, 2017Co-Authors: Katherine N Clayton, Dong Hoon Lee, Steven T Wereley, Tamara L KinzerursemAbstract:In absence of efficient ways to test drug stability and efficacy, pharmaceuticals that have been stored outside of set temperature conditions are destroyed, often at great cost. This is especially problematic for biotherapeutics, which are highly sensitive to temperature fluctuations. Current platforms for assessing the stability of protein-based biotherapeutics in high throughput and in low volumes are unavailable outside of research and development laboratories and are not efficient for use in production, quality control, distribution, or clinical settings. In these alternative environments, microanalysis platforms could provide significant advantages for the characterization of biotherapeutic degradation. Here we present particle diffusometry (PD), a new technique to study degradation of biotherapeutic solutions. PD uses a simple microfluidic chip and microscope setup to calculate the Brownian motion of particles in a quiescent solution using a variation of particle image velocimetry (PIV) fundamentals. We show that PD can be used to measure the viscosity of protein solutions to discriminate intact protein from degraded samples as well as to determine the change in viscosity as a function of therapeutic concentration. PD viscosity analysis is applied to two particularly important biotherapeutic preparations: insulin, a commonly used protein for diabetic patients, and monoclonal antibodies which are an emerging class of biotherapeutics used to treat a variety of diseases such as autoimmune disorders and cancer. PD-based characterization of solution viscosity is a new tool for biotherapeutic analysis, and owing to its easy setup could readily be implemented at key points of the pharmaceutical Delivery Chain and in clinical settings.