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Your search keyword '"Van der Spek, Pieter"' showing total 19 results
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19 results on '"Van der Spek, Pieter"'

13. 7153 Endoscopic palliation of malignant gastric-outlet obstruction.

Author

Ferrante, Michel Ep, primary, Vandervoort, Jo Gp, additional, De Coninck, Steven Am, additional, Vanstiphout, Jos Je, additional, De Man, Marc, additional, Van der Spek, Pieter, additional, De Troyer, Martine M., additional, Lepoutre, Luc, additional, and Ziekenhuis, Onze Lieve Vrouw, additional

Published
2000
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15. Balancing Time-to-Market and Quality in Embedded Systems.

Author

van der Spek, Pieter and Verhoef, Chris

Subjects
*TIME to market (New products), *RAYLEIGH model, *COST estimates, *TIME series analysis, *EMBEDDED computer systems, *MAGNETIC resonance imaging
Abstract

ABSTRACT Finding a balance between the time-to-market and quality of a delivered product is a daunting task. The optimal release moment is not easily found. We propose to use historical project data to monitor the progress of running projects. From the data we inferred a formula providing a rough indication of the number of defects given the effort spent thus far (effort-to-defect formula). Furthermore, we provide a worst case bound to the allowed number of residual defects at the end of a project in order to achieve the required level of quality. For this purpose we slightly modified a well-known reliability growth model by Bishop and Bloomfield. It turned out that the software in Philips' MRI scanners has a defect rate of 1 per 1175 device-years of observation. This coincides with the second highest safety integrity level ( SIL3) as defined in the IEC 61508 standard. The highest level ( SIL4) is only attainable by applying redundancy. Finally, we combine the effort-to-defect formula with the reliability growth model to monitor the progress of a project and to determine when the required level of quality will be reached. We show that a common fault distribution, the Rayleigh model, is not necessarily the best model for predicting the number of residual defects in the system. Using a well-known data analysis approach called exploratory data analysis ( EDA) we obtained an alternative model based on the Normal curve. We have evaluated the Rayleigh model and our model based on the Normal curve at Philips Healthcare MRI. The Normal curve predicts defects over time better than the Rayleigh model in the case of Philips Healthcare MRI. Furthermore, time series models ( ARIMA) are also useful for accurately describing the defect trend, but are not suitable for long-term predictions. Finally, cost estimation models ( COCOMO) lack the predictive capabilities of models fitted on the data using EDA. Their capabilities are limited compared to a model derived from data which reflects the constitutional knowledge of the actual realization of systems within a specific company. However, they can still be used to advantage when there is limited or no data available to use as a basis for lifting from gut feel to order of magnitude. © 2013 Wiley Periodicals, Inc. Syst Eng 17 [ABSTRACT FROM AUTHOR]

Published
2014
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19. ⁎⁎Invited to participate in the poster session of the asge meeting.4698 Endoscopic intracystic treatment of pancreatic pseudocysts: a possible innovative technique in their management?

Author

De Coninck, Steven Am, Vandervoort, Jo Gp, Ferrante, Michel Ep, Troost, Els, Vanstiphout, Jos Je, Van der Spek, Pieter, De Man, Marc, De Troyer, Martine M., and Lepoutre, Luc

Abstract

Introduction: Endoscopic transmural drainage is a treatment modality of pancreatic pseudocysts when visible extrinsic compression of the gastric or duodenal wall and close apposition to the lumen are present. We describe a new technique based upon introduction of the endoscope into the pseudocyst in order to treat complications of drainage. Case 1: A 52-year-old man with chronic pancreatitis presented with a mature symptomatic pseudocyst located in the pancreatic head and bulging into the duodenum. Endoscopic transduodenal drainage was complicated by stent migration into the pseudocyst. A nasocystic catheter was inserted. Three days later the cystostomy tract was dilated with a 12 mm balloon until we were able to advance the endoscope into the pseudocyst. The stent was removed with a snare and cyst fluid was aspirated before endoscope withdrawal. Since ERCP revealed pseudocyst communication with the pancreatic duct, a transpapillary drainage was performed. The pseudocyst resolved with no recurrence after 3 months of follow-up. Case 2:Seven months following an episode of acute pancreatitis, a 54-year-old man presented with a mature symptomatic pseudocyst located in the pancreatic head, bulging into the duodenum and not communicating with the pancreatic duct. Uneventful endoscopic transduodenal drainage was performed. Two days later stent migration into the gut and pseudocyst infection were noticed. Antibiotics were started. After 12 mm balloon dilation of the cystostomy tract, the endoscope was advanced into the pseudocyst followed by aspiration or extraction of cyst fluid and debris. A nasocystic catheter was inserted. The catheter was irrigated twice under endoscopic view with saline passing together with cyst debris through the cystostomy into the duodenum, until only clear fluid was returning. Two weeks later an intracystic bleeding due to rupture of a pseudoaneurysm was treated by angiographic embolization. Further follow-up was uneventful with pseudocyst resolution after 3 months. Conclusion: Balloon dilation of a cystostomy tract followed by advancement of an endoscope into a pseudocyst can be safely performed in a mature pancreatic pseudocyst adjacent to the upper GI-tract. This new technique enabled us to treat complications of endoscopic transmural pseudocyst drainage for which surgery is usually carried out. It offers new perspectives in the endoscopic treatment of well-defined pseudocysts but needs further validation before it can be promoted as such.

Published
2000
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