Robert van Veen - Academia.edu (original) (raw)

Papers by Robert van Veen

Research paper thumbnail of Determination of visible near-IR absorption coefficients of mammalian fat using time- and spatially resolved diffuse reflectance and transmission spectroscopy

Journal of Biomedical Optics, 2005

In-vivo optical spectroscopy and the determination of tissue absorption and scattering properties... more In-vivo optical spectroscopy and the determination of tissue absorption and scattering properties have a central role in the development of novel optical diagnostic and therapeutic modalities in medicine. A number of techniques are available for the optical characterization of tissue in the visible near-IR region of the spectrum. An important consideration for many of these techniques is the reliability of the absorption spectrum of the various constituents of tissue. The availability of accurate absorption spectra in the range 600 to 1100 nm may allow for the determination of the concentration of key tissue constituents such as oxy-and deoxy-hemoglobin, water, and lipids. The objective of the current study is the determination of a reliable absorption spectrum of lipid͑s͒ that can be used for component analysis of in-vivo spectra. We report the absorption spectrum of a clear purified oil obtained from pig lard. In the liquid phase above 36°C, the oil is transparent and thus suitable for collimated transmission measurements. At room temperature, the oil is a solid grease that is highly scattering. The absorption and scattering properties in this solid phase are measured using time-and spatially resolved diffuse reflectance spectroscopy. Using these three independent measurement techniques, we have determined an accurate estimate for the absorption spectrum of mammalian fat.

Research paper thumbnail of In situ light dosimetry during photodynamic therapy of Barrett's esophagus with 5-aminolevulinic acid

Lasers in Surgery and Medicine, 2002

Background and Objectives: Previous studies with PhotoDynamic Therapy (PDT) in bladder and bronch... more Background and Objectives: Previous studies with PhotoDynamic Therapy (PDT) in bladder and bronchi have shown that due to scattering and reflection, the actually delivered fluence rate on the surface in a hollow organ can be significantly higher than expected. In this pilot study, we investigated the differences between the primary calculated and the actual measured fluence rate during PDT of Barrett's Esophagus (BE) using 23 independent clinical measurements in 15 patients. Study Design/Materials and Methods: A KTP-dye module laser at 630 nm was used as light source. Light delivery was performed using a cylindrical light diffuser inserted in the center of an inflatable transparent balloon with a length corresponding to the length of the Barrett's epithelium. The total light output power of the cylindrical diffuser was calibrated using an integrating sphere to deliver a primary fluence rate of 100 mW cm À2. Two fiber-optic pseudo sphere isotropic detectors were placed on the balloon and were used to measure fluence rate at the surface of the esophageal wall during PDT. Results and Conclusions: The actual fluence rate measured was 1.5-3.9 times higher than the primary fluence rate for 630 nm. In general, the fluence rate amplification factor decreased with increasing redness of the tissue and was less for shorter diffusers. Fluence rate variations in time were observed which coincided with patients coughing, movement, and esophageal spasms. These factors combined with inter patient variability of the fluence rate measured appears to justify the routine application of this technique in

Research paper thumbnail of In Vivo Optical Measurements for Diagnostics and Monitoring of Treatment

textabstractThe interaction of light with tissue and its use for medical purposes has been under ... more textabstractThe interaction of light with tissue and its use for medical purposes has been under investigation for centuries. Since the early nineteen sixties, the development of novel optical technology and advances in laser design/technology allowed a wide range of innovative applications in many fields of medicine. For the majority of light applications in medicine the distribution of light within tissue is of fundamental importance. The light distribution is determined by the optical properties of the tissue; scattering and absorption. This thesis focuses on two applications of light in medicine, photodynamic therapy (PDT) and optical diagnostics. For each application the effect of differences in and changes of tissue optical properties are investigated. The distribution of light within tissue is of vital importance in PDT and is strongly dependent on the in vivo optical properties. In vivo differences and variations in optical properties are also critically important for optica...

Research paper thumbnail of Intraoperative Photodynamic Therapy After Pleuropneumonectomy In Patients With Malignant Pleural Mesothelioma*

Chest, 2001

Schouwink, Hugo; Rutgers, Emiel T.; van der Sijp, Joost; Oppelaar, Hugo; van Zandwijk, Nico; van ... more Schouwink, Hugo; Rutgers, Emiel T.; van der Sijp, Joost; Oppelaar, Hugo; van Zandwijk, Nico; van Veen, Robert; Burgers, Sjaak; Stewart, Fiona A.; Zoetmulder, Frans; Baas, Paul.

Research paper thumbnail of Determination of visible near-IR absorption coefficients of mammalian fat using time- and spatially resolved diffuse reflectance and transmission spectroscopy

Journal of Biomedical Optics, 2005

In-vivo optical spectroscopy and the determination of tissue absorption and scattering properties... more In-vivo optical spectroscopy and the determination of tissue absorption and scattering properties have a central role in the development of novel optical diagnostic and therapeutic modalities in medicine. A number of techniques are available for the optical characterization of tissue in the visible near-IR region of the spectrum. An important consideration for many of these techniques is the reliability of the absorption spectrum of the various constituents of tissue. The availability of accurate absorption spectra in the range 600 to 1100 nm may allow for the determination of the concentration of key tissue constituents such as oxy-and deoxy-hemoglobin, water, and lipids. The objective of the current study is the determination of a reliable absorption spectrum of lipid͑s͒ that can be used for component analysis of in-vivo spectra. We report the absorption spectrum of a clear purified oil obtained from pig lard. In the liquid phase above 36°C, the oil is transparent and thus suitable for collimated transmission measurements. At room temperature, the oil is a solid grease that is highly scattering. The absorption and scattering properties in this solid phase are measured using time-and spatially resolved diffuse reflectance spectroscopy. Using these three independent measurement techniques, we have determined an accurate estimate for the absorption spectrum of mammalian fat.

Research paper thumbnail of In situ light dosimetry during photodynamic therapy of Barrett's esophagus with 5-aminolevulinic acid

Lasers in Surgery and Medicine, 2002

Background and Objectives: Previous studies with PhotoDynamic Therapy (PDT) in bladder and bronch... more Background and Objectives: Previous studies with PhotoDynamic Therapy (PDT) in bladder and bronchi have shown that due to scattering and reflection, the actually delivered fluence rate on the surface in a hollow organ can be significantly higher than expected. In this pilot study, we investigated the differences between the primary calculated and the actual measured fluence rate during PDT of Barrett's Esophagus (BE) using 23 independent clinical measurements in 15 patients. Study Design/Materials and Methods: A KTP-dye module laser at 630 nm was used as light source. Light delivery was performed using a cylindrical light diffuser inserted in the center of an inflatable transparent balloon with a length corresponding to the length of the Barrett's epithelium. The total light output power of the cylindrical diffuser was calibrated using an integrating sphere to deliver a primary fluence rate of 100 mW cm À2. Two fiber-optic pseudo sphere isotropic detectors were placed on the balloon and were used to measure fluence rate at the surface of the esophageal wall during PDT. Results and Conclusions: The actual fluence rate measured was 1.5-3.9 times higher than the primary fluence rate for 630 nm. In general, the fluence rate amplification factor decreased with increasing redness of the tissue and was less for shorter diffusers. Fluence rate variations in time were observed which coincided with patients coughing, movement, and esophageal spasms. These factors combined with inter patient variability of the fluence rate measured appears to justify the routine application of this technique in

Research paper thumbnail of In Vivo Optical Measurements for Diagnostics and Monitoring of Treatment

textabstractThe interaction of light with tissue and its use for medical purposes has been under ... more textabstractThe interaction of light with tissue and its use for medical purposes has been under investigation for centuries. Since the early nineteen sixties, the development of novel optical technology and advances in laser design/technology allowed a wide range of innovative applications in many fields of medicine. For the majority of light applications in medicine the distribution of light within tissue is of fundamental importance. The light distribution is determined by the optical properties of the tissue; scattering and absorption. This thesis focuses on two applications of light in medicine, photodynamic therapy (PDT) and optical diagnostics. For each application the effect of differences in and changes of tissue optical properties are investigated. The distribution of light within tissue is of vital importance in PDT and is strongly dependent on the in vivo optical properties. In vivo differences and variations in optical properties are also critically important for optica...

Research paper thumbnail of Intraoperative Photodynamic Therapy After Pleuropneumonectomy In Patients With Malignant Pleural Mesothelioma*

Chest, 2001

Schouwink, Hugo; Rutgers, Emiel T.; van der Sijp, Joost; Oppelaar, Hugo; van Zandwijk, Nico; van ... more Schouwink, Hugo; Rutgers, Emiel T.; van der Sijp, Joost; Oppelaar, Hugo; van Zandwijk, Nico; van Veen, Robert; Burgers, Sjaak; Stewart, Fiona A.; Zoetmulder, Frans; Baas, Paul.