WiersmaLab

RODENY D. WIERSMA, PH.D.

Faculty, Department of Radiation and Cellular Oncology

Member, Committee on Medical Physics

EDUCATION

• 09/95 - 04/99    University of Alberta, Edmonton, Canada
Bachelor of Science with Honors in Physics


• 09/99 - 06/02    Simon Fraser University, Vancouver, Canada
Master of Science in Semiconductor Physics


• 06/02 - 05/06    Max-Planck-Institute FKF, Stuttgart, Germany
Doctor of Philosophy in Condensed Matter Physics


• 06/06 - 12/08    Stanford University, Stanford, USA
Postdoc Scholar in Medical Physics

OPEN POSITIONS

• Postdoctorial Scholar Opening
I have funding for one postdoctoral position in the Medical Physics Division of the Department of Radiation and Cellular Oncology. I am looking for an individual who has recently received a Ph.D. in medical physics, physics or engineering. The areas of research include development of image-guided adaptive radiotherapy methods and nano-particle detection methods. Prior MRI or magnetic field construction and detection experience is greatly desired. Good programming skills in C++, C#, Matlab or Labview are also beneficial.

PROJECTS

• Frameless Gated Head Stereotactic Radiotherapy via Real-Time Optical Position Monitoring and an Adaptive Head Motion Compensation Stage
We are developing a real-time 3D optically guided adaptive head motion compensation stage for use in stereotactic radiosurgery/radiotherapy. The goal of this project is to reduce patient setup time and to perform accurate minimally invasive frameless head radiosurgery/radiotherapy. A Polaris 4D tracker (NDI) is used to monitor four optical reflective markers rigidly fixated to a biteblock at 30 fps with an accuracy of 0.25 mm RMS. Head motion compensation is done through the use of a stepper motor stage. Labview is used for system control.


• Dynamic kV Collimator for Low Diagnostic Dose Real-Time 3D Motion Tracking during Radiation Therapy by Combined MV-kV Imaging
We are currently using combined MV (EPID) and kV (onboard fluoroscopic imager) imaging on a Varian Trilogy system to perform real-time 3D tracking of internally placed metallic markers. Currently, the technique requires use of continuous kV imaging throughout the treatment process leading to high diagnostic dose levels. We want to reduce exposure through the development of a dynamic motor controlled aperture to confine the kV exposure to a small region of interest (ROI) encompassing only the markers. As the internal markers move, the aperture is dynamically updated using feedback information provided by the last known marker positions.


• Superparamagnetic Nano-Particle Cluster Tracking and Molecular Imaging for Tumor Localization during Radiotherapy
This project uses magnetic nanoparticle clusters as a method for organ motion tracking and possible molecular imaging. The nanoparticle clusters are exposed to an external oscillating magnetic field and their magnetization response is measured using lock-in techniques. The potentially large SNR allows detection of vary small amounts of particles, letting the internal clusters be much smaller and less invasive than current metallic markers. Use of a 2D coil array, measuring the cluster signal from many different positions in space, may be used for real-time 3D position calculation based on triangulation methods.

PUBLICATIONS

Book Chapters

1) R. D. Wiersma, N. Riaz, L. Xing, Real-Time Imaging for Radiation Therapy Guidance, Biomedical Mathematics: Promising Directions in Imaging, Therapy Planning and Inverse Problems", Yair Censor, Ming Jiang and Ge Wang (Editors), Medical Physics Publishing, Madison, Wisconsin, USA, (2009)

Papers

17) Weihua Mao, Annie Hsu, Nadeem Riaz, Louis Lee, Rodney Wiersma, Gary Luxton, Christopher King, Lei Xing, Timothy Solberg, Image-Guided Radiotherapy in Near Real Time With Intensity-Modulated Radiotherapy Megavoltage Treatment Beam Imaging, International Journal of Radiation Oncology * Biology * Physics, 75 (2), 603-610, (2009)

16) Nadeem Riaz, Piyush Shanker, Rodney Wiersma, Olafur Gudmundsson, Weihua Mao, Bernard Widrow and Lei Xing, Predicting respiratory tumor motion with multi dimensional adaptive filters and support vector regression, Phys. Med. Biol., 54 (19), 5735-5748, (2009)

15) Wiersma R. D., Riaz N, Dieterich S, Suh Y, Xing L., Use of MV and kV imager correlation for maintaining continuous real-time 3D internal marker tracking during beam interruptions, Phys Med Biol., 54 (1), 89-103 (2009)

14) Liu W, Wiersma R. D., Mao W, Luxton G, Xing L., Real-time 3D internal marker tracking during arc radiotherapy by the use of combined MV-kV imaging, Phys Med Biol., 53 (24), 7197-213 (2008)

13) Mao W, Riaz N, Lee L, Wiersma R. D., Xing L., A fiducial detection algorithm for real-time image guided IMRT based on simultaneous MV and kV imaging, Med Phys., 35 (8), 3554-64 (2008)

12) Mao W, Wiersma R. D., Xing L., Fast internal marker tracking algorithm for onboard MV and kV imaging systems, Med Phys., 35 (5), 1942-9 (2008)

11) R. D. Wiersma, W. Mao, and L. Xing, Combined kV and MV imaging for real-time tracking of implanted fiducial markers, Med. Phys., 35 (4), 1191-1198 (2008)

10) Wiersma, R. D.; Lok, JCS; Tiemann, L, W. Dietsche, K. von Klitzing. Investigations of the nu(T)=1 exciton condensate, INTERNATIONAL JOURNAL OF MODERN PHYSICS B, (21), 1256-1265 (2007)

9) R. D. Wiersma and L. Xing, Examination of Geometric and Dosimetric Accuracies of Gated Step-and-Shoot Intensity Modulated Radiation Therapy, Med. Phys., 34 (10), 3962 - 3970 (2007)

8) R. D. Wiersma, J. G. S. Lok, L. Tiemann, W. Dietsche, K. von Klitzing, D. Schuh, M., W. Wegscheider, Investigations of the vT=1 exciton condensate, Physica E-Low Dimensional Systems & Nanostructures, 35 (2), 320-326, (2006)

7) R. D. Wiersma, J. G. S. Lok, W. Dietsche, K. von Klitzing, D. Schuh, M. Bichler, H. -P. Tranitz, and W. Wegscheider, Role of density imbalance in the vT=1 exciton condensate state for electron bilayer systems, Physica Status Solidi, 243, No. 14, (2006)

6) R. D. Wiersma, J. G. S. Lok, S. Kraus, W. Dietsche, K. von Klitzing, et al., Activated Transport in the vT=1 Exciton Condensate at Balanced and Imbalanced Densities Measured in Drag and Counter-flow Configuration, Physica E, 34 (1-2): 16-21, (2006)

5) R. D. Wiersma, J. G. S. Lok, S. Kraus, W. Dietsche, K. von Klitzing, D. Schuh, M. Bichler, H. -P. Tranitz, and W. Wegscheider, Activated Transport in the Separate Layers that form the vT=1 Exciton Condensate, Physical Review Letters, 93, 266805 (2004)

4) R. D. Wiersma, J. A. H. Stotz, C. X. Wang, M. L. W. Thewalt, and S. P. Watkins, Electrical and optical properties of carbon doped GaSb, Physical Review B, 67, 165202 (2003)

3) S. P. Watkins, R. D. Wiersma, C. X. Wang, O. J. Pitts, and C. R. Bolognesi, Structural Effects of Carbon in GaSb Grown by Metalorganic Vapor Phase Epitaxy, Journal of Crystal Growth (2003)

2) X. K. Chen, R. D. Wiersma, C. X. Wang, O. J. Pitts, C. Dale, C. R. Bolognesi, S. P. Watkins, Local vibrational mode of carbon in GaSb and GaAsSb, Applied Physics Letters, 80, 1942 (2002)

1) R. D. Wiersma, J. A. H. Stotz, O. J. Pitts, C. X. Wang, M. L. W. Thewalt, and S. P. Watkins, P-type carbon doping of GaSb, Journal of Electrical Materials, 30, 1429 (2001)

Talks

11) Image Guided Radiation Therapy: from patient setup, real-time monitoring of tumor motion to adaptive therapy, UCSD Radiation Oncology Academic Seminar Series(2008)

10) Real-time Tracking of Implanted Fiducial Markers using Combined Onboard kV Fluoroscopy and MV EPID Imaging, 50th Annual ASTRO Meeting, Boston, USA (2008)

9) Managing intra-fraction organ motion I: 4D CT and IGRT treatment planning, Stanford IGRT Short Course, Stanford, USA (2008)

8) Dosimetric Consequences of Electronic Delay on Gated Radiation Therapy (RT), 49th Annual ASTRO Meeting, Los Angeles, USA (2007)

7) Dosimetric Precision of Gated Step-and-Shoot Intensity Modulated Radiation Therapy, 49th Annual AAPM Meeting, Minneapolis, USA (2007)

6) Temporal Precision of Gated Step-and-Shoot Intensity Modulated Radiation Therapy, 49th Annual AAPM Meeting, Minneapolis, USA (2007)

5) Precision of Gated Step-and-Shoot Intensity Modulated Radiation Therapy, Visiting Professor Research Symposium, Stanford, USA (2007)

4) Investigations of the ?T=1 Exciton Condensate and Possible Novel Devices, 14th International Winterschool on New Developments in Solid State Physics, Mauterndorf, Austria, (2006)

3) Activted Transport in the Separate Layers that form the ?=1 Exciton Condensate, Electronic Properties of Two-Dimensional System 16 (EP2DS-16), Albuquerque, New Mexico, (2005)

2) P-type Carbon Doping of GaSb, Pacific Center for Advanced Materials and Microstructures (PCAMM) Conference, Simon Fraser University, (2001)

1) P-type Carbon Doping of GaSb, Canadian Association of Physics (CAP) Meeting, University of Victoria, (2001)

Published Abstracts

10) Wiersma, RD; Mao, W; Xing, L; Riaz, N, Prediction of Fiducial Motion in Respiratory Tumors for Image-Guided Radiotherapy, MEDICAL PHYSICS Volume: 35 Issue: 6 Pages: 2626-2626 Published: JUN 2008

9) Wiersma, RD; Mao, W; Xing, L; Luxton, G, Liu, W; Riaz, N, Nearly Real-Time Tumor Position Monitoring During Arc Therapy with Combined MV and kV Imaging, MEDICAL PHYSICS Volume: 35 Issue: 6 Pages: 2626-2626 Published: JUN 2008

8) Wiersma, RD; Mao, W; Lee, K; Xing, L, Riaz, N, Tracking Multiple Moving Fiducials During Treatment Based on Simultaneous Onboard kV and Treatment MV Imaging, MEDICAL PHYSICS Volume: 35 Issue: 6 Pages: 2621-2621 Published: JUN 2008

7) Riaz, N; Wiersma, RD; Mao, W; Xing, L, Improving Tracking of Implanted Radio-Opaque Markers on MV and kV Imaging with Techniques from Computer Vision and Machine Learning, MEDICAL PHYSICS Volume: 35 Issue: 6 Pages: 2618-2618 Published: JUN 2008

6) Wiersma, RD; Mao, W; Riaz, N; Xing, L, Use of Synchronized Beam Switching for Real-Time 3D kV-MV Internal Marker Tracking with Step-and-Shoot IMRT, MEDICAL PHYSICS Volume: 35 Issue: 6 Pages: 2598-2598 Published: JUN 2008

5) Mao, W; Riaz, N; Lee, K; Wiersma, RD; King, C:Hsu, A; Luxton, G; Xing, L, Using Treatment Beam Imaging to Monitor Prostate Motion in Near Real-Time On a Conventional LINAC, MEDICAL PHYSICS Volume: 35 Issue: 6 Pages: 2634-2634 Published: JUN 2008

4) Wiersma, RD; Mao, W; Riaz, N; Xing, L, Real-time tracking of implanted fiducial markers using combined kV and MV imaging, MEDICAL PHYSICS Volume: 35 Issue: 6 Pages: 2634-2634 Published: JUN 2008

3) Wiersma, RD; Xing, L, Dosimetric consequences of electronic delay on gated radiation therapy (RT), INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS Volume: 69 Pages: S131-S132 Published: 2007

2) Wiersma, RD; Xing, L, Temporal precision of gated step-and-shoot intensity modulated radiation therapy, MEDICAL PHYSICS Volume: 34 Issue: 6 Pages: 2560-2560 Published: JUN 2007

1) Wiersma, RD; Xing, L, Temporal, dosimetric, and geometric precision of gated step-and-shoot intensity modulated radiation therapy, MEDICAL PHYSICS Volume: 34 Issue: 6 Pages: 2601-2601 Published: JUN 2007

Patents

1) Patent title: 3D real-time tracking of human anatomy using combined kV and MV imaging Inventors: Lei Xing Rodney D. Wiersma Weihua Mao Agents: LUMEN PATENT FIRM Origin: PALO ALTO, CA US IPC8 Class: AG06K900FI USPC Class: 382128