Single-minded Dedication, Singular Result

Posted on | August 4, 2011 | No Comments

Calculating Radiation Schemes

Danny Z. Chen

  • Danny Z. Chen
    Computer Science and Engineering

No one is surprised when Olympic athletes push beyond what they thought their limits were to run faster, throw farther, and perform at a much higher level than they have ever done. It is considered a natural outcome of their hard work, in many cases years of commitment, to capture a gold medal. Society doesn’t always use the same thought processes in regard to researchers. Instead, people expect a “eureka” moment. The truth is that first-generation technologies are often the fruit of years of work conducted by dedicated researchers. The same is true for second- and third-generation technologies. Proving that point, the same researchers who helped develop the latest generation of intensity-modulated radiation therapy have now introduced a new medical treatment technology that can deliver a prescribed radiation dosage using a single pass. This new technique provides equally effective treatment with much less potential damage to healthy tissue in half of the time.

For more than a decade Danny Z. Chen, professor of computer science and engineering, has been focusing his efforts on one of the interfaces between computer technology and medicine. In 2002 as he was discussing his work on medical treatment algorithms and the development of more efficient and accurate radiation therapy dosage calculations, Chen said, “The interface of computer technologies and medicine is going to have a huge impact on society.” By 2007, he and collaborators from Notre Dame and the University of Maryland School of Medicine had already made an impact, introducing hardware (field programmable gate arrays) and software (new leaf sequencing algorithms) for advanced intensity-modulated radiation therapy (IMRT). Their technique produced IMRT plans that reduced treatment times by more than 60 percent while providing higher quality dose distribution for more accurate targeting of tumors. The technology was licensed by Prowess, Inc., an international provider of medical software products and services for the radiation therapy community.

Chen Research image

From left to right, dose-volume histograms show that the dose distribution of radiation delivered by arc-modulated radiation therapy (single-arc) of a brain case, a lung case, and a prostate case is comparable or potentially superior to intensity-modulated arc therapy (fixed-gantry) or intensity-modulated arc therapy?(multiple arcs).

Chen research image

In a case study comparing the delivery parameters for arc-modulated radiation therapy (AMRT) and intensity-modulated radiation therapy (IMRT) on the head and neck, AMRT performed the same dosage distribution and delivery ­­in almost half the time.

Less than a decade later, Chen and team — Chao Wang, a former Notre Dame graduate student who is currently a scientist at Xcision Medical Systems, LLC; Shuang Luan, a former Notre Dame graduate student who is now an associate professor of computer science at the University of New Mexico; Grace Tang, a former graduate student of the University College of London who is now serving as a postdoctoral researcher at Memorial Sloan-Kettering Cancer Center; and Assistant Professor Matthew A. Earl and Dr. Cedric X. Yu, clinical professor, both of the University of Maryland School of Medicine — have introduced a new rotational IMRT: Arc-modulated radiation therapy (AMRT). With a patent pending, AMRT has also recently been licensed by Varian Medical Systems, one of the world’s largest manufacturers of devices and software for radiation treatment systems.

Although others have studied AMRT, Chen and his collaborators have developed a different method for optimizing rotational radiation delivery. Their goal was to deliver the optimal dose with only one gantry rotation, offering the advantage of rotational arc therapy without the inefficiency involved in delivering multiple arcs. They believed they could target a tumor using a given intensity pattern at a fixed angle through non-overlapping apertures from neighboring beam angles. By simply spreading the apertures previously aligned for each gantry angle into the neighboring angles, they were able to “multiplex” the angles.

Their AMRT consists of three steps: inverse planning, leaf sequencing, and dose calculation. The performance of their AMRT has been verified through multiple clinical cases of different parts of the body and has proven effective in producing dose distributions that rival current IMRT techniques.­­

Most recently, a patent for AMRT has been approved by the United States Patent and Trademark Office. Notre Dame has also been honored as a Laureate in the 2011 Computerworld Honors Program for its work in this area.

Suggested Reading

Bansal, Nikhil; Chen, Danny Z.; Coppersmith, Don; Hu, Xiaobo S.; Luan, Shuang; Misloek, Ewa; Schieber, Baruch; and Wang, Chao, “Shape Rectangular-ization Problems in Intensity-modulated Radiation Therapy,” Algorithmica, 2011 60, 2, 421-450.

Chen, Danny Z.; Luan, Shuang; and Wang, Chao, “Coupled Path Planning, Region Optimization, and Applications in Intensity-modulated Radiation Therapy,” Algorithmica, 2011, 60, 1, ­­152-174.

Zhou, Bo; Yu, Cedric X.; Chen, Danny Z.; and Hu, Xiaobo S., “GPU-accelerated Monte Carlo Convolution/Super-position Implementation for Dose Calculation,” Medical Physics, 2010, 37, 11, 5593-5603.

Chen, Danny Z.; Hu, Xiaobo S.; Wang, Chao; Luan, Shuang; and Wu, Xiaodong, “Mountain Reduction, Block Matching, and Applications in Intensity-modulated Radiation Therapy,” International Journal of Computational Geometry and Applications, 2008, 18, 1-2, 63-106.

Wang, Chao; Luan, Shuang; Tang, Grace; Chen, Danny Z.; Earl, Matt A.; and Yu, Cedric X., “Arc-modulated Radiation Therapy (AMRT): A Single-arc Form of Intensity-modulated Arc Therapy,” Physics in Medicine and Biology, 2008, 53, 6291-6303.

Shuang, Luan; Wang, Chao; Chen, D.Z.; Shepard, D.M.; and Yu, Cedric X., “Leaf-sequencing for Intensity-modulated Arc Therapy Using GraphAlgorithms,” Medical Physics, 2008, 35, 1, 61-69.

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