Georg Stamm | Hannover Medical School (original) (raw)

Papers by Georg Stamm

Research paper thumbnail of Organdosis leicht bestimmt

Research paper thumbnail of Kinderorthopädische Untersuchung: Bildgebende Verfahren

Springer Reference Medizin, Dec 31, 2022

Research paper thumbnail of Strahlenexposition und Dosisoptimierung in der CT

Research paper thumbnail of 2nd Modification and Update of Diagnostic Reference Levels in Germany - Improvements and Consequences

Poster: "EuroSafe Imaging 2017 / ESI-0034 / 2nd Modification and Update of Diagnostic Refere... more Poster: "EuroSafe Imaging 2017 / ESI-0034 / 2nd Modification and Update of Diagnostic Reference Levels in Germany - Improvements and Consequences" by: "G. Stamm1, H. Lenzen2, M. Wucherer3, G. Brix4, A. Schegerer4, A. Sommer5; 1Institute for Diagnostic and Interventional Radiology Gottingen/DE, 2Institute of Clinical Radiology Munster/DE, 3Institut fur Medizinische Physik Nurnberg, D/DE, 4 Neuherberg/DE, 5Reference Center Munster/DE"

Research paper thumbnail of Paediatric CT Exposure Practice in the Federal Republic of Germany. Results of a Nation-wiede Survey in 2005/06

Research paper thumbnail of Two-dimensional turbulent nonstationary superfluid counterflows: Numerical simulations, qualitative effects

Research paper thumbnail of Schnelle, interaktive Segmentierung medizinischer 3D-Datensätze durch Anwendung der „Image Foresting Transformation“ in zwei verschiedenen Auflösungsstufen

Informatik aktuell, 2002

Zusammenfassung. Zur Segmentierung von 3D-Datensätzen in der klinischen Praxis werden Verfahren b... more Zusammenfassung. Zur Segmentierung von 3D-Datensätzen in der klinischen Praxis werden Verfahren benötigt, die einen möglichst geringen Interaktionsaufwand besitzen und flexibel einsetzbar sind. Dieses Ziel wird durch die vorgenommenen Erweiterungen der "Image Foresting Transformation" erreicht. Die Leistungsfähigkeit des Verfahrens wird anhand des Vergleichs zur manuellen Segmentierung eingeschätzt.

Research paper thumbnail of Dosisoptimiertes CT

RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2014

Research paper thumbnail of New Vessel Analysis Tool for Morphometric Quantification and Visualization of Vessels in CT and MR Imaging Data Sets

RadioGraphics, 2004

Image processing algorithms and a prototypical research software tool have been developed for vis... more Image processing algorithms and a prototypical research software tool have been developed for visualization and quantitative analysis of vessels in data sets from computed tomography and magnetic resonance imaging. The software is based on a sequence of processing steps, which are as follows: (a) vessel segmentation based on a region growing algorithm, (b) interactive "premasking" to optionally exclude interfering structures close to the vessels of interest, (c) distance transformbased skeletonization, (d) multiplanar reformation orthogonal to the vessel path, (e) identification of the lumen boundary on the orthogonal cross-section images, and (f) morphometric measurements. The development of the algorithmic components and the application user interface has been carried out in close cooperation with clinical users to achieve a high degree of usability and flexible support of work flow. The software has been successfully applied to the intracranial arteries, carotid arteries, and abdominal and thoracic aorta, as well as the renal, coronary, and peripheral arteries.

Research paper thumbnail of Boundary layer influence on He II flows

Physica B: Condensed Matter, 1994

Research paper thumbnail of Visualization of Taylor-Couette flow in superfluid helium

Research paper thumbnail of The boiling-up process in He II: optical measurements and visualization

Cryogenics, 1992

The boiling-up process in superfluid helium was measured by an optical method and compared with p... more The boiling-up process in superfluid helium was measured by an optical method and compared with previous experiments of other authors. The influence of the different pulse triggering rates was removed by introducing a dimensionless parameter. It appears that the reported new method is much more sensitive than those used in former investigations and gives the possibility of a visualization of the whole process. Further, vapour bubbles with finite dimensions (diameter of the order of 1 cm) were observed in the bulk liquid. Depending on the remaining liquid column (or hydrostatic pressure head) above the heater, these bubbles have a lifetime of up to 50 ms. The lower the pressure head, the longer is the lifetime of the bubbles.

Research paper thumbnail of Acoustic, video and thermoacoustic registration of boiling up phenomena in He II

Cryogenics, 1992

A piezodetector, video with strobed light flash and fast film superconducting thermometers were a... more A piezodetector, video with strobed light flash and fast film superconducting thermometers were applied to research boiling up processes developing when steplike heat pulse is released on a film heater in He II. More exact data concerning the dependence of the boiling up time tB in He II upon the heat flux density Q were obtained at 1.85 and 1.40 ]~'. An influence of heat triggering frequency on ~B was revealed, indicating that superfluid turbulence or a vortex tangle plays a role in such processes. A substantial-up to 40 ms-lifetime of vapour bubbles with dimensions more than 1 cm. diameter was found. The temperature raise in bubbles corresponds to that related with hydrostatic pressure of liquid above the heater.

Research paper thumbnail of Temperature overshoot due to quantum turbulence during the evolution of moderate heat pulses in He II

Journal of Fluid Mechanics, 1990

Transient heat transfer in liquid helium is investigated both experimentally and theoretically in... more Transient heat transfer in liquid helium is investigated both experimentally and theoretically in plane and cylindrical geometry in the range of parameters where superfluid turbulence appears to be important. The influence of the main flow parameters-heat flux, pulse duration, and rest timeon the temperature evolution is reported. At high heat inputs the mutual friction force related to the superfluid vortex lines leads to the formation of a temperature overshoot behind the propagating second-sound wave and must be looked upon as a macroscopic effect of microscopic quantum turbulence. The experimental results can be reproduced by a theoretical model when the mutual interaction force is expressed in terms of the vortex line density (VLD), and the Vinen equation, extended to include spatial dependence, is taken into account for its temporal evolution. Fair quantitative agreement between experiment and theory is obtained if the ratio of the temperature overshoot and the shock-wave amplitude is below about 4. At stronger heat inputs the agreement is only qualitative.

Research paper thumbnail of Strahlenschutzaspekte bei Multi-Slice-CT – ein Update

Research paper thumbnail of Smartphones jetzt noch smarter? - Möglichkeit des Einsatzes als „Dosiswarner“

RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2013

• " radiation safety • " technical aspects • " radiation • " technology assessment

Research paper thumbnail of Phantom and cadaver measurements of dose and dose distribution in micro-CT of the chest in mice

Acta Radiologica, 2011

Background Micro-computed tomography (CT) allows high-resolution imaging of the chest in mice for... more Background Micro-computed tomography (CT) allows high-resolution imaging of the chest in mice for small animal research with a significant radiation dose applied. Purpose To report on measurement of the applied radiation dose using different scan protocols in micro-CT of the chest in mice. Material and Methods Repetitive dose measurements were performed for four different micro-CT protocols (with/without respiratory gating) and for micro-CT fluoroscopy used for chest imaging. Measurements were carried out using thermoluminescence dosimeters (TLD) in mouse cadavers and in a PMMA phantom allowing measurement of the radiation dose in the direct path of rays and assessment of scattered radiation. Results The dose measured inside and outside the chests of the cadavers varied between 190 und 210 mGy, respectively. The expected mean doses in mice in the direct path of rays for the four examined micro-CT protocols varied between 170 and 280 mGy. The mean values for 1 and 5 minutes of fluoro...

Research paper thumbnail of Handling of Incidents in the Clinical Application of Ionizing Radiation in Diagnostic and Interventional Radiology – a Multi-center Study

RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2021

Purpose According to the German legislation and regulation of radiation protection, i. e. Strahle... more Purpose According to the German legislation and regulation of radiation protection, i. e. Strahlenschutzgesetz und Strahlenschutzverordnung (StrlSchG and StrlSchV), which came into force on 31st December 2018, significant unintended or accidential exposures have to be reported to the competent authority. Furthermore, facilities have to implement measures to prevent and to recognize unintended or accidental exposures as well as to reduce their consequences. We developed a process to register incidents and tested its application in the framework of a multi-center-study. Materials and Methods Over a period of 12 months, 16 institutions for x-ray diagnostics and interventions, documented their incidents. Documentation of the incidents was conducted using the software CIRSrad, which was developed, released for testing purposes and implemented in the frame of the study. Reporting criteria of the project were selected to be more sensitive compared to the legal criteria specifying “signific...

Research paper thumbnail of Procurement strategy for a dose management system

Der Radiologe (Berlin. Print), Dec 17, 2020

We present the different steps for procurement of a dose management system for a university hospi... more We present the different steps for procurement of a dose management system for a university hospital, starting from the Europe-wide request for proposals, the product presentations by the suppliers and the final decision. For a project of this size, it is advisable to involve external consultants, especially for preparation of the system specifications and the calculation of the total cost of ownership (TCO). Use cases were of special interest in assessing the functionality of the different systems. Following the product presentations some changes were made concerning the system specifications and minimum requirements. Qualified users like medical physics experts, radiologists and technicians as well as users from generic quality management should form the team for evaluation and final product decision.

Research paper thumbnail of Persistent DNA Double-Strand Breaks After Repeated Diagnostic CT Scans in Breast Epithelial Cells and Lymphocytes

Frontiers in Oncology, 2021

DNA double-strand break (DSB) induction and repair have been widely studied in radiation therapy ... more DNA double-strand break (DSB) induction and repair have been widely studied in radiation therapy (RT); however little is known about the impact of very low exposures from repeated computed tomography (CT) scans for the efficiency of repair. In our current study, DSB repair and kinetics were investigated in side-by-side comparison of RT treatment (2 Gy) with repeated diagnostic CT scans (≤20 mGy) in human breast epithelial cell lines and lymphoblastoid cells harboring different mutations in known DNA damage repair proteins. Immunocytochemical analysis of well known DSB markers γH2AX and 53BP1, within 48 h after each treatment, revealed highly correlated numbers of foci and similar appearance/disappearance profiles. The levels of γH2AX and 53BP1 foci after CT scans were up to 30% of those occurring 0.5 h after 2 Gy irradiation. The DNA damage repair after diagnostic CT scans was monitored and quantitatively assessed by both γH2AX and 53BP1 foci in different cell types. Subsequent diag...

Research paper thumbnail of Organdosis leicht bestimmt

Research paper thumbnail of Kinderorthopädische Untersuchung: Bildgebende Verfahren

Springer Reference Medizin, Dec 31, 2022

Research paper thumbnail of Strahlenexposition und Dosisoptimierung in der CT

Research paper thumbnail of 2nd Modification and Update of Diagnostic Reference Levels in Germany - Improvements and Consequences

Poster: "EuroSafe Imaging 2017 / ESI-0034 / 2nd Modification and Update of Diagnostic Refere... more Poster: "EuroSafe Imaging 2017 / ESI-0034 / 2nd Modification and Update of Diagnostic Reference Levels in Germany - Improvements and Consequences" by: "G. Stamm1, H. Lenzen2, M. Wucherer3, G. Brix4, A. Schegerer4, A. Sommer5; 1Institute for Diagnostic and Interventional Radiology Gottingen/DE, 2Institute of Clinical Radiology Munster/DE, 3Institut fur Medizinische Physik Nurnberg, D/DE, 4 Neuherberg/DE, 5Reference Center Munster/DE"

Research paper thumbnail of Paediatric CT Exposure Practice in the Federal Republic of Germany. Results of a Nation-wiede Survey in 2005/06

Research paper thumbnail of Two-dimensional turbulent nonstationary superfluid counterflows: Numerical simulations, qualitative effects

Research paper thumbnail of Schnelle, interaktive Segmentierung medizinischer 3D-Datensätze durch Anwendung der „Image Foresting Transformation“ in zwei verschiedenen Auflösungsstufen

Informatik aktuell, 2002

Zusammenfassung. Zur Segmentierung von 3D-Datensätzen in der klinischen Praxis werden Verfahren b... more Zusammenfassung. Zur Segmentierung von 3D-Datensätzen in der klinischen Praxis werden Verfahren benötigt, die einen möglichst geringen Interaktionsaufwand besitzen und flexibel einsetzbar sind. Dieses Ziel wird durch die vorgenommenen Erweiterungen der "Image Foresting Transformation" erreicht. Die Leistungsfähigkeit des Verfahrens wird anhand des Vergleichs zur manuellen Segmentierung eingeschätzt.

Research paper thumbnail of Dosisoptimiertes CT

RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2014

Research paper thumbnail of New Vessel Analysis Tool for Morphometric Quantification and Visualization of Vessels in CT and MR Imaging Data Sets

RadioGraphics, 2004

Image processing algorithms and a prototypical research software tool have been developed for vis... more Image processing algorithms and a prototypical research software tool have been developed for visualization and quantitative analysis of vessels in data sets from computed tomography and magnetic resonance imaging. The software is based on a sequence of processing steps, which are as follows: (a) vessel segmentation based on a region growing algorithm, (b) interactive "premasking" to optionally exclude interfering structures close to the vessels of interest, (c) distance transformbased skeletonization, (d) multiplanar reformation orthogonal to the vessel path, (e) identification of the lumen boundary on the orthogonal cross-section images, and (f) morphometric measurements. The development of the algorithmic components and the application user interface has been carried out in close cooperation with clinical users to achieve a high degree of usability and flexible support of work flow. The software has been successfully applied to the intracranial arteries, carotid arteries, and abdominal and thoracic aorta, as well as the renal, coronary, and peripheral arteries.

Research paper thumbnail of Boundary layer influence on He II flows

Physica B: Condensed Matter, 1994

Research paper thumbnail of Visualization of Taylor-Couette flow in superfluid helium

Research paper thumbnail of The boiling-up process in He II: optical measurements and visualization

Cryogenics, 1992

The boiling-up process in superfluid helium was measured by an optical method and compared with p... more The boiling-up process in superfluid helium was measured by an optical method and compared with previous experiments of other authors. The influence of the different pulse triggering rates was removed by introducing a dimensionless parameter. It appears that the reported new method is much more sensitive than those used in former investigations and gives the possibility of a visualization of the whole process. Further, vapour bubbles with finite dimensions (diameter of the order of 1 cm) were observed in the bulk liquid. Depending on the remaining liquid column (or hydrostatic pressure head) above the heater, these bubbles have a lifetime of up to 50 ms. The lower the pressure head, the longer is the lifetime of the bubbles.

Research paper thumbnail of Acoustic, video and thermoacoustic registration of boiling up phenomena in He II

Cryogenics, 1992

A piezodetector, video with strobed light flash and fast film superconducting thermometers were a... more A piezodetector, video with strobed light flash and fast film superconducting thermometers were applied to research boiling up processes developing when steplike heat pulse is released on a film heater in He II. More exact data concerning the dependence of the boiling up time tB in He II upon the heat flux density Q were obtained at 1.85 and 1.40 ]~'. An influence of heat triggering frequency on ~B was revealed, indicating that superfluid turbulence or a vortex tangle plays a role in such processes. A substantial-up to 40 ms-lifetime of vapour bubbles with dimensions more than 1 cm. diameter was found. The temperature raise in bubbles corresponds to that related with hydrostatic pressure of liquid above the heater.

Research paper thumbnail of Temperature overshoot due to quantum turbulence during the evolution of moderate heat pulses in He II

Journal of Fluid Mechanics, 1990

Transient heat transfer in liquid helium is investigated both experimentally and theoretically in... more Transient heat transfer in liquid helium is investigated both experimentally and theoretically in plane and cylindrical geometry in the range of parameters where superfluid turbulence appears to be important. The influence of the main flow parameters-heat flux, pulse duration, and rest timeon the temperature evolution is reported. At high heat inputs the mutual friction force related to the superfluid vortex lines leads to the formation of a temperature overshoot behind the propagating second-sound wave and must be looked upon as a macroscopic effect of microscopic quantum turbulence. The experimental results can be reproduced by a theoretical model when the mutual interaction force is expressed in terms of the vortex line density (VLD), and the Vinen equation, extended to include spatial dependence, is taken into account for its temporal evolution. Fair quantitative agreement between experiment and theory is obtained if the ratio of the temperature overshoot and the shock-wave amplitude is below about 4. At stronger heat inputs the agreement is only qualitative.

Research paper thumbnail of Strahlenschutzaspekte bei Multi-Slice-CT – ein Update

Research paper thumbnail of Smartphones jetzt noch smarter? - Möglichkeit des Einsatzes als „Dosiswarner“

RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2013

• " radiation safety • " technical aspects • " radiation • " technology assessment

Research paper thumbnail of Phantom and cadaver measurements of dose and dose distribution in micro-CT of the chest in mice

Acta Radiologica, 2011

Background Micro-computed tomography (CT) allows high-resolution imaging of the chest in mice for... more Background Micro-computed tomography (CT) allows high-resolution imaging of the chest in mice for small animal research with a significant radiation dose applied. Purpose To report on measurement of the applied radiation dose using different scan protocols in micro-CT of the chest in mice. Material and Methods Repetitive dose measurements were performed for four different micro-CT protocols (with/without respiratory gating) and for micro-CT fluoroscopy used for chest imaging. Measurements were carried out using thermoluminescence dosimeters (TLD) in mouse cadavers and in a PMMA phantom allowing measurement of the radiation dose in the direct path of rays and assessment of scattered radiation. Results The dose measured inside and outside the chests of the cadavers varied between 190 und 210 mGy, respectively. The expected mean doses in mice in the direct path of rays for the four examined micro-CT protocols varied between 170 and 280 mGy. The mean values for 1 and 5 minutes of fluoro...

Research paper thumbnail of Handling of Incidents in the Clinical Application of Ionizing Radiation in Diagnostic and Interventional Radiology – a Multi-center Study

RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, 2021

Purpose According to the German legislation and regulation of radiation protection, i. e. Strahle... more Purpose According to the German legislation and regulation of radiation protection, i. e. Strahlenschutzgesetz und Strahlenschutzverordnung (StrlSchG and StrlSchV), which came into force on 31st December 2018, significant unintended or accidential exposures have to be reported to the competent authority. Furthermore, facilities have to implement measures to prevent and to recognize unintended or accidental exposures as well as to reduce their consequences. We developed a process to register incidents and tested its application in the framework of a multi-center-study. Materials and Methods Over a period of 12 months, 16 institutions for x-ray diagnostics and interventions, documented their incidents. Documentation of the incidents was conducted using the software CIRSrad, which was developed, released for testing purposes and implemented in the frame of the study. Reporting criteria of the project were selected to be more sensitive compared to the legal criteria specifying “signific...

Research paper thumbnail of Procurement strategy for a dose management system

Der Radiologe (Berlin. Print), Dec 17, 2020

We present the different steps for procurement of a dose management system for a university hospi... more We present the different steps for procurement of a dose management system for a university hospital, starting from the Europe-wide request for proposals, the product presentations by the suppliers and the final decision. For a project of this size, it is advisable to involve external consultants, especially for preparation of the system specifications and the calculation of the total cost of ownership (TCO). Use cases were of special interest in assessing the functionality of the different systems. Following the product presentations some changes were made concerning the system specifications and minimum requirements. Qualified users like medical physics experts, radiologists and technicians as well as users from generic quality management should form the team for evaluation and final product decision.

Research paper thumbnail of Persistent DNA Double-Strand Breaks After Repeated Diagnostic CT Scans in Breast Epithelial Cells and Lymphocytes

Frontiers in Oncology, 2021

DNA double-strand break (DSB) induction and repair have been widely studied in radiation therapy ... more DNA double-strand break (DSB) induction and repair have been widely studied in radiation therapy (RT); however little is known about the impact of very low exposures from repeated computed tomography (CT) scans for the efficiency of repair. In our current study, DSB repair and kinetics were investigated in side-by-side comparison of RT treatment (2 Gy) with repeated diagnostic CT scans (≤20 mGy) in human breast epithelial cell lines and lymphoblastoid cells harboring different mutations in known DNA damage repair proteins. Immunocytochemical analysis of well known DSB markers γH2AX and 53BP1, within 48 h after each treatment, revealed highly correlated numbers of foci and similar appearance/disappearance profiles. The levels of γH2AX and 53BP1 foci after CT scans were up to 30% of those occurring 0.5 h after 2 Gy irradiation. The DNA damage repair after diagnostic CT scans was monitored and quantitatively assessed by both γH2AX and 53BP1 foci in different cell types. Subsequent diag...