Michiel Janssen - Academia.edu (original) (raw)
Uploads
Papers by Michiel Janssen
Transfusion, 2011
The shelf life of platelet concentrates (PCs) is a matter of days. Simultaneously, the demand is ... more The shelf life of platelet concentrates (PCs) is a matter of days. Simultaneously, the demand is highly variable, shortages are not allowed, and producing too many results in outdating. Concurrently, younger PCs, implying an extended time till outdating (TTO), are preferred. Common PC inventory management relies on experience-based order-up-to rules. This study aimed at minimizing outdating and shortages, while extending the TTO through a theoretical approach. It focuses on PCs processed from whole blood donations. A combined approach of stochastic dynamic programming and simulation techniques (SDP/S), from the mathematical discipline operations research, has been implemented. This approach included the design of the dedicated software tool thrombocyte inventory management optimizer (TIMO). Based on the 2007 data, an optimal order-up-to rule was calculated. Outdating percentages and TTOs have been collected from August 2005 to July 2010. The resulting order-up-to rule has been applied and adjusted from summer 2007 onward. Over the study period, the results of the practical implementation showed significant improvements. The median weekly outdating percentage dropped to less than 1% and a gain in TTO of 0.48 day was reached. The results and the additional computer simulations brought confidence to the personnel to apply and adopt the "theoretical" approach and TIMO. Applying theory may help a blood bank to improve its PC inventory management and may help to identify to what extent practical limits can approach theoretical limits. The application of the theory has led to both a significant improvement and a more structured and less panic-driven PC inventory management.
European Respiratory Journal, Sep 1, 2013
Studies in health technology and informatics
Despite years of extensive research, the etiology of idiopathic scoliosis still has not been reso... more Despite years of extensive research, the etiology of idiopathic scoliosis still has not been resolved. A hypothesis on the role of posteriorly directed shear loads was studied in several biomechanical and imaging studies. So far, it has been shown that: on the human erect spine these posteriorly directed shear loads act; these loads decrease the rotational stability of the spine vitro and in vivo; once rotation occurs, it logically follows an already built-in vertebral rotational pattern, that is pre-existent in the human spine; this pre-existent rotational pattern is related to organ anatomy, and not to handedness; certain areas in the female spine are more subject to posteriorly directed shear loads as certain areas in the female spine are more backwardly inclined. Although it is appreciated that the cause of idiopathic scoliosis is multi-factorial, we believe that the delicate upright spinal sagittal balance and the unique posteriorly directed shear loads acting on the erect human spine play a crucial role in the rotational stability of the human spine, and thus in the pathogenesis of idiopathic scoliosis.
Spine, 2009
A three-dimensional analysis of spino-pelvic alignment in 60 asymptomatic young adult males and f... more A three-dimensional analysis of spino-pelvic alignment in 60 asymptomatic young adult males and females. To analyze the differences in sagittal spino-pelvic alignment in a group of asymptomatic young adult males and females and describe gender specific reference values. Several spinal disorders like idiopathic scoliosis and Scheuermann's disease have a well-known sex-related prevalence ratio. As spino-pelvic alignment plays an important role in spinal biomechanics, it is imperative to analyze possible differences between the male and female spino-pelvic alignment. Furthermore, in spinal fusion surgery, normal sagittal balance should be recreated as closely as possible. An innovative biplanar ultra low-dose radiographic technique was used to obtain three-dimensional reconstructions of the spine (T1-L5), sacrum, and pelvis in a freestanding position of 30 asymptomatic young male and 30 young female adults. Values were calculated for thoracic kyphosis (T4-T12), lumbar lordosis (L1-...
Studies in health technology and informatics, 2010
Despite years of extensive research, the etiology of idiopathic scoliosis still has not been reso... more Despite years of extensive research, the etiology of idiopathic scoliosis still has not been resolved. A hypothesis on the role of posteriorly directed shear loads was studied in several biomechanical and imaging studies. So far, it has been shown that: on the human erect spine these posteriorly directed shear loads act; these loads decrease the rotational stability of the spine vitro and in vivo; once rotation occurs, it logically follows an already built-in vertebral rotational pattern, that is pre-existent in the human spine; this pre-existent rotational pattern is related to organ anatomy, and not to handedness; certain areas in the female spine are more subject to posteriorly directed shear loads as certain areas in the female spine are more backwardly inclined. Although it is appreciated that the cause of idiopathic scoliosis is multi-factorial, we believe that the delicate upright spinal sagittal balance and the unique posteriorly directed shear loads acting on the erect huma...
Journal of Biomechanics, 2012
Green Chemistry, 2007
ABSTRACT
Advanced Synthesis & Catalysis, 2001
This review describes the remarkable transition in the manufacture of b-lactam antibiotics, which... more This review describes the remarkable transition in the manufacture of b-lactam antibiotics, which is driven by the desire to reduce or eliminate the production of waste and the dependence on organic solvents. To this effect, traditional chemical procedures are gradually being replaced by biotransformations. The b-lactam antibiotics industry has led the way in the introduction of biocatalysis in the fine chemicals industry by replacing the chemical multi-step process for the penicillin nucleus 6aminopenicillanic acid (6-APA) by an enzymatic one in the early 1990's. Recently, bioprocesses have been developed for the synthesis of the cephalosporin nucleus, 7-aminodeacetoxycephalosporanic acid (7-ADCA) from a penicillin precursor and will shortly be commercialized. Thirty years of research have now resulted in viable enzymatic procedures for coupling the b-lactam nuclei with d-phenylglycine side-chains. The necessary adaptations in the synthesis of the side-chain donors have likewise resulted in more efficient procedures.
Archives of Internal Medicine, Oct 27, 2003
Background: Several reports of various bleeding problems associated with the use of serotonergic ... more Background: Several reports of various bleeding problems associated with the use of serotonergic antidepressants have been published. However, no information concerning the effect of these drugs on perioperative blood loss and blood transfusion requirements during orthopedic surgery is available. The objective of this study was to determine the association between use of serotonergic antidepressants and perioperative blood loss and transfusion in orthopedic surgical patients.
Spine, Sep 30, 2011
Pelvic incidence (PI) was measured in 3 dimensions from computed tomographic (CT) images of norma... more Pelvic incidence (PI) was measured in 3 dimensions from computed tomographic (CT) images of normal subjects using a computerized method. To obtain the angle of PI from 3-dimensional (3D) images and analyze its distribution in a normal population. The sagittal alignment of the pelvis is usually evaluated in 2-dimensional (2D) sagittal radiographs. The purpose of this study is to measure and analyze PI, which represents a key parameter of sagittal alignment, in 3D images. A computerized method, based on image-processing techniques, was used to automatically determine the anatomical references required to measure PI, that is, the centers of the femoral heads in 3 dimensions and the center and inclination of the sacral end plate in 3 dimensions. Multiplanar image reformation was applied to obtain perfect sagittal views with all anatomical structures completely in line with the hip axis from which PI was calculated. PI was successfully obtained in CT images of 370 normal subjects (mean age: 41.5 years; range: 1-87 years). The mean PI (± standard deviation) was equal to 46.6° (±9.2°) for male subjects, 47.6° (±10.7°) for female subjects, and 47.1° (±10.0°) for both sexes. No statistically significant differences were obtained between the sexes, and statistically significant correlation was obtained between PI and age. In this study, the sagittal alignment of the pelvis was evaluated in terms of PI completely in 3 dimensions. The results show that computerized measurements of PI in 3 dimensions are less variable than manual measurements. The large span of PI values for normal subjects indicates that the natural variation of PI is relatively large.
Global Spine Journal, 2016
Transfusion, 2011
The shelf life of platelet concentrates (PCs) is a matter of days. Simultaneously, the demand is ... more The shelf life of platelet concentrates (PCs) is a matter of days. Simultaneously, the demand is highly variable, shortages are not allowed, and producing too many results in outdating. Concurrently, younger PCs, implying an extended time till outdating (TTO), are preferred. Common PC inventory management relies on experience-based order-up-to rules. This study aimed at minimizing outdating and shortages, while extending the TTO through a theoretical approach. It focuses on PCs processed from whole blood donations. A combined approach of stochastic dynamic programming and simulation techniques (SDP/S), from the mathematical discipline operations research, has been implemented. This approach included the design of the dedicated software tool thrombocyte inventory management optimizer (TIMO). Based on the 2007 data, an optimal order-up-to rule was calculated. Outdating percentages and TTOs have been collected from August 2005 to July 2010. The resulting order-up-to rule has been applied and adjusted from summer 2007 onward. Over the study period, the results of the practical implementation showed significant improvements. The median weekly outdating percentage dropped to less than 1% and a gain in TTO of 0.48 day was reached. The results and the additional computer simulations brought confidence to the personnel to apply and adopt the "theoretical" approach and TIMO. Applying theory may help a blood bank to improve its PC inventory management and may help to identify to what extent practical limits can approach theoretical limits. The application of the theory has led to both a significant improvement and a more structured and less panic-driven PC inventory management.
European Respiratory Journal, Sep 1, 2013
Studies in health technology and informatics
Despite years of extensive research, the etiology of idiopathic scoliosis still has not been reso... more Despite years of extensive research, the etiology of idiopathic scoliosis still has not been resolved. A hypothesis on the role of posteriorly directed shear loads was studied in several biomechanical and imaging studies. So far, it has been shown that: on the human erect spine these posteriorly directed shear loads act; these loads decrease the rotational stability of the spine vitro and in vivo; once rotation occurs, it logically follows an already built-in vertebral rotational pattern, that is pre-existent in the human spine; this pre-existent rotational pattern is related to organ anatomy, and not to handedness; certain areas in the female spine are more subject to posteriorly directed shear loads as certain areas in the female spine are more backwardly inclined. Although it is appreciated that the cause of idiopathic scoliosis is multi-factorial, we believe that the delicate upright spinal sagittal balance and the unique posteriorly directed shear loads acting on the erect human spine play a crucial role in the rotational stability of the human spine, and thus in the pathogenesis of idiopathic scoliosis.
Spine, 2009
A three-dimensional analysis of spino-pelvic alignment in 60 asymptomatic young adult males and f... more A three-dimensional analysis of spino-pelvic alignment in 60 asymptomatic young adult males and females. To analyze the differences in sagittal spino-pelvic alignment in a group of asymptomatic young adult males and females and describe gender specific reference values. Several spinal disorders like idiopathic scoliosis and Scheuermann's disease have a well-known sex-related prevalence ratio. As spino-pelvic alignment plays an important role in spinal biomechanics, it is imperative to analyze possible differences between the male and female spino-pelvic alignment. Furthermore, in spinal fusion surgery, normal sagittal balance should be recreated as closely as possible. An innovative biplanar ultra low-dose radiographic technique was used to obtain three-dimensional reconstructions of the spine (T1-L5), sacrum, and pelvis in a freestanding position of 30 asymptomatic young male and 30 young female adults. Values were calculated for thoracic kyphosis (T4-T12), lumbar lordosis (L1-...
Studies in health technology and informatics, 2010
Despite years of extensive research, the etiology of idiopathic scoliosis still has not been reso... more Despite years of extensive research, the etiology of idiopathic scoliosis still has not been resolved. A hypothesis on the role of posteriorly directed shear loads was studied in several biomechanical and imaging studies. So far, it has been shown that: on the human erect spine these posteriorly directed shear loads act; these loads decrease the rotational stability of the spine vitro and in vivo; once rotation occurs, it logically follows an already built-in vertebral rotational pattern, that is pre-existent in the human spine; this pre-existent rotational pattern is related to organ anatomy, and not to handedness; certain areas in the female spine are more subject to posteriorly directed shear loads as certain areas in the female spine are more backwardly inclined. Although it is appreciated that the cause of idiopathic scoliosis is multi-factorial, we believe that the delicate upright spinal sagittal balance and the unique posteriorly directed shear loads acting on the erect huma...
Journal of Biomechanics, 2012
Green Chemistry, 2007
ABSTRACT
Advanced Synthesis & Catalysis, 2001
This review describes the remarkable transition in the manufacture of b-lactam antibiotics, which... more This review describes the remarkable transition in the manufacture of b-lactam antibiotics, which is driven by the desire to reduce or eliminate the production of waste and the dependence on organic solvents. To this effect, traditional chemical procedures are gradually being replaced by biotransformations. The b-lactam antibiotics industry has led the way in the introduction of biocatalysis in the fine chemicals industry by replacing the chemical multi-step process for the penicillin nucleus 6aminopenicillanic acid (6-APA) by an enzymatic one in the early 1990's. Recently, bioprocesses have been developed for the synthesis of the cephalosporin nucleus, 7-aminodeacetoxycephalosporanic acid (7-ADCA) from a penicillin precursor and will shortly be commercialized. Thirty years of research have now resulted in viable enzymatic procedures for coupling the b-lactam nuclei with d-phenylglycine side-chains. The necessary adaptations in the synthesis of the side-chain donors have likewise resulted in more efficient procedures.
Archives of Internal Medicine, Oct 27, 2003
Background: Several reports of various bleeding problems associated with the use of serotonergic ... more Background: Several reports of various bleeding problems associated with the use of serotonergic antidepressants have been published. However, no information concerning the effect of these drugs on perioperative blood loss and blood transfusion requirements during orthopedic surgery is available. The objective of this study was to determine the association between use of serotonergic antidepressants and perioperative blood loss and transfusion in orthopedic surgical patients.
Spine, Sep 30, 2011
Pelvic incidence (PI) was measured in 3 dimensions from computed tomographic (CT) images of norma... more Pelvic incidence (PI) was measured in 3 dimensions from computed tomographic (CT) images of normal subjects using a computerized method. To obtain the angle of PI from 3-dimensional (3D) images and analyze its distribution in a normal population. The sagittal alignment of the pelvis is usually evaluated in 2-dimensional (2D) sagittal radiographs. The purpose of this study is to measure and analyze PI, which represents a key parameter of sagittal alignment, in 3D images. A computerized method, based on image-processing techniques, was used to automatically determine the anatomical references required to measure PI, that is, the centers of the femoral heads in 3 dimensions and the center and inclination of the sacral end plate in 3 dimensions. Multiplanar image reformation was applied to obtain perfect sagittal views with all anatomical structures completely in line with the hip axis from which PI was calculated. PI was successfully obtained in CT images of 370 normal subjects (mean age: 41.5 years; range: 1-87 years). The mean PI (± standard deviation) was equal to 46.6° (±9.2°) for male subjects, 47.6° (±10.7°) for female subjects, and 47.1° (±10.0°) for both sexes. No statistically significant differences were obtained between the sexes, and statistically significant correlation was obtained between PI and age. In this study, the sagittal alignment of the pelvis was evaluated in terms of PI completely in 3 dimensions. The results show that computerized measurements of PI in 3 dimensions are less variable than manual measurements. The large span of PI values for normal subjects indicates that the natural variation of PI is relatively large.
Global Spine Journal, 2016