Titles

Assistant Professor of Radiation Oncology and Molecular Radiation Sciences and Oncology

Schools\Degrees

Ph.D., University of Chicago School of Medicine, Chicago, IL

Training

Stanford University School of Medicine

Certifications

ABMP

Clinical Interests

Radiation Planning Optimazaiton, Sterotactic Radiotherapy Techniques Gene Therapy for Prostate Cancer, Brachytherapy Optimazation and Source Localization

Research Summary

Research Goals

The research goal is to develop an image-guided and computer-aidedoptimal radiotherapy of cancer. The first project is to develop and test a patient refixation system for stereotactic radiotherapy (SRT) in order to improve the position accuracy and treatment efficacy of brain tumor. The second project is to introduce an image-guided intensity-modulated radiotherapy and volume monitoring technique for treatment of Head & Neck, breast, and chest wall tumors. The third project is developing an image-guided real-time intraoperative high-dose-rate brachytherapy (IOHDRB) planning system useful for locally advanced and recurrent tumors and skin cancers.

Another research goal is to derive a simple and specific dosimetric model for interstitial adenoviral gene therapy of prostate cancer.

Overall Research Summary and Significance

Brain metastases develop in up to 50% of all patients with cancer, particularly for the patients with lung and breast cancers, renal cell carcinomas, and melanomas. Even though more people harvest the multiple brain metastases, there are many technical difficulties in management of multiple brain metastases including inaccessible for deep-seeded tumor and unresectable for the micro-diseases. Stereotactic radiotherapy or radiosurgery are thought as an optimal approach for the tumor control but patient refixation is time consuming and imprecise position can increase the chance of normal tissue complications. One research effort in the stereotactic radiotherapy program at Johns Hopkins is to improve the precision and accuracy of patient position and dose delivery. This faculty member is the lead physicist in the program and an expert in the techniques. Several research projects introduced by the faculty such as a novel 3D-surface image-guided radiotherapy (supervised an SBIR grant from NIH), treatment optimization for multiple-targets, and a study of dose-response for fractionated SRT, are under investigation.

The most massive, recurrent tumors often encroach major blood vessels or adjacent organs and the local control rate is low without the brachytherapy. Recent clinical trials of intraoperative high dose rate brachytherapy (IOHDRB) had yield excellent local control and survival in those patients with recurrent colorectal carcinoma, advanced head and neck tumor, and retroperitoneal sarcomas. However, there is no real-time IOHDRB planning system available for a large-scale clinical application. To fully realize the therapeutic potentials of IOHDRB, this faculty introduces an automatic HDR brachytherapy planning system. The system can complete the treatment planning in a few minutes and provide accurate geometric and dosimetric information. Two additional researches carried by the faculty member are development of dosimetry system for a gene therapy program and a new volume monitoring system for determination of the tumor-response to the radiation. The faculty is key member for the NIH and DOD founded clinical trials of gene therapy of prostate cancer using CG7060 adenovirus. One critical consideration was the development of a dosimetric model for optimal viral delivery in order to maximize the tumor control. In this research effort, the faculty has developed the first dosimetric model, which predicts that outcome is strongly influenced by the integral dose of virus and the target volume coverage. This contribution for interstitial gene therapy will serve as a basis for quantitative analysis of on-going and future studies and has been recently published as an editorial favorite article in International Journal of Radiation Oncology, Biology, and Physics (Red Journal).

The investigator has also introduced the surface-based volumetric monitoring and breast cancer IMRT. The study will establish the relationship between 3D surface and the tumor volume under the surface using 3D-surface images. The data can also be used for evaluation of the cosmetic effect due to the radiotherapy. The real-time image-guided IMRT of breast cancer will also reduce the dose to the lung and heart while increasing the dose to the breast tumor therefore reducing the radiation damage to those critical organs while improving the local control.

Journal Citations

Shidong Li, and et al, "Dosimetric and technical considerations for interstitial adenoviral gene therapy as applied to prostate cancer." Int. J. Radiation Oncology, Biology, and Physics, Vol. 55, PP: 204-214, 2003.



Li, S, Frassica, D, DeWeese, T, Lee, DJ, Geng, J, and Nag, S, "A Real-Time Image-Guided Intraoperative High-Dose-Rate Brachytherapy System," in press, Int. J. Brachytherapy, Vol 1, Number 4, 2003.



S. Li, "A Hybrid of Pencil Beam Model and Clarkson Integration for Accurate Dose Calculation and Monitor Unit Verification Useful For IMRT and SRT", Med. Phys.,29: 1262, 2002 (abstract).