The 52nd meeting of the American Association of Physicists in Medicine (AAPM) convenes from July 18 - 22, 2010 in Philadelphia, PA.
AAPM is the premier organization in medical physics, a broadly-based scientific and professional discipline encompassing physics principles and applications in medicine and biology. Its membership includes medical physicists who specialize in research that develops cutting-edge technologies and board-certified clinical medical physicists who apply these technologies in community hospitals, clinics, and academic medical centers.
Highlights of the meeting are listed below.
MEETING HIGHLIGHTS
- Nanocoated Gold Bullets Help Destroy Tumors, Improve Radiation Therapy
- Tumor Tracking with Smart Probing – A Stock Market Approach
- Six-Year Study Finds Few Permanent Side Effects After SBRT for Lung Cancer
- A Library of Lung Tumors
- Tactile Tumor-Imaging Device
- Making Tumors Glow Could Reveal Their Hiding Spots
- IMRT Safe and Effective for Treating Cancers of Paranasal Sinus
- New Nanotechnology Capsule Delivers Cancer Drug, Then Heat
- New Multisource X-Ray Imaging Technology
- Testing Proton Clusters
- Solid-State X-Ray Intensifiers
- To Treat Cancer, Subdivide and Conquer
- Red-Flagging Cancer
- More Meeting Information
1) NANOCOATED GOLD BULLETS HELP DESTROY TUMORS, IMPROVE RADIATION THERAPY
Image-guided radiation therapy targets tumors in organs that tend to move during treatment, such as the prostate gland or the lungs, as well as tumors near vital organs. Often, inert markers are implanted into the body to help radiation oncologists pinpoint the cancerous tissue.
A group of researchers wants to draft these markers to deliver drugs that will combat cancer and make the tumor more sensitive to radiation. The drugs can be tailored to different tumor types, the researchers say.
"Right now, these markers are just passive implants that are inserted into the tumor," says Srinivas Sridhar, a physics professor at Northeastern University and director of the university's Electronic Materials Research Institute. "We're making them active and smart using nanotechnology," he said.
The challenge is designing a system that will work over an extended period of time and target the entire tumor without affecting healthy tissue. The team has already developed a nanoscale polymer coating containing anti-cancer drugs for gold fiducials, which are commonly used markers.
Now, the researchers report they can precisely tailor drug dosage and rate of release in laboratory tests lasting up to three months. The nanoporous morphology of the polymer coatings enabled the controlled release of molecules and nanoparticles. The results also help refine the team's models of drug release kinetics.
The group includes collaborators Mike Makrigiorgos and Robert Cormack from Brigham & Women's Hospital and Dana-Farber Cancer Institute.
The Presentation "Release Kinetics of Radio-Sensitizers From Nanoporous Coatings On Gold Fiducials: Biological In-Situ Dose-Painting for IGRT" by C Stambaugh et al. will be at 4:12 p.m. on Wednesday, July 21 in room 204B of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-13246-24612-876.pdf
2) TUMOR TRACKING WITH SMART PROBING – A STOCK MARKET APPROACH
Pinpointing tumor location and behavior can be as risky and frustrating as estimating the rise and fall of stocks in the market. A new model, developed by Dan Ruan, Ph.D., an instructor in radiation oncology at Stanford University, and colleagues, employs tactics similar to those used by market analysts. Ruan will present the model at the 2010 annual meeting of the American Association of Physicists in Medicine, July 18-22, in Philadelphia, PA.
"In estimating the stock market," she says, "people try to predict how stock will behave based on historical data and the company's portfolio." The mathematical model uses data on how tumor motion has changed during a course of radiation treatment in addition to real-time images of a tumor to calculate how much confidence the physcists can have about an instantaneous tumor position estimate. The goal of the work is to reduce the number of times intrafraction X-ray needs to be triggered as tumor localization measurement, thereby reducing the total amount of radiation a patient receives.
With a typical image-guided radiotherapy (IGRT) protocol, X-rays are used at a fixed frequency to validate the location of the tumor target. This rate may be increased to improve the localization accuracy. Ruan's model, however, which she calls adaptive, aims to accurately localize tumors in real-time by imaging smarter, rather than more frequently. It makes online decisions as to whether or not it is necessary to take a new X-ray image during treatment. In test cases that she will present, imaging frequency was reduced by 40 to 50 per cent without sacrificing tumor localization accuracy, meaning that the X-ray dosage to the patient was essentially halved or close to halved.
Reducing imaging radiation is an important goal for oncologists because radiation is associated with secondary malignancies, especially in pediatric patients who typically live for a long time after surviving their cancer. The model should be helpful in these cases, and particularly for tumors that because of their location – lung, thorax, and abdomen – are difficult to locate because of the body movement that occurs as patients breathe.
The Presentation " Reducing Imaging Dose Without Sacrificing Target Localization Accuracy: A Feasibility Study Byline D Ruan" by D Ruan and P Keall will be at 10:24 a.m. on Tuesday, July 20 in room 204B of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-13987-71074-176.pdf
This research was supported by the National Cancer Institute and the AAPM Seed Funding Initiative.
3) SIX-YEAR STUDY FINDS FEW PERMANENT SIDE EFFECTS AFTER SBRT FOR LUNG CANCER
A six-year study of lung cancer patients treated with stereotactic body radiation therapy (SBRT) found few people experienced significant lasting side effects from the relatively new technique.
SBRT hits tumors with extremely high (but narrowly focused) radiation doses, typically given in three to five treatments. The researchers evaluated lung density changes in 63 people who received SBRT between 2003 and 2009. After six months, patients had transient density increases of up to 100 percent compared to their pre-treatment lung density. After 12 months, the density changes stabilized to less than 50 percent of pre-treatment levels, and lung morphology was mostly unaffected.
"We saw some changes, but nothing of a catastrophic nature or anything that implies we're going in the wrong direction with this treatment," says co-author Brian Kavanagh, a professor of radiation oncology at the University of Colorado Denver School of Medicine. "The first impression is very much a reassuring one."
Understanding how normal lung tissue is affected by the intense radiation will help physicians avoid excess injury to healthy tissue and more aggressively treat tumors, says Kavanagh.
The researchers also discovered that some patients had subtle changes in normal tissue that appeared to signal later development of side effects such as inflammation.
"These early signals will give us an opportunity to anticipate potential problems and personalize treatments," says co-author Moyed Miften, a professor of radiation oncology at UC Denver.
Funding sources: University of Colorado Denver Cancer Center
The Presentation "Temporal Dose-Response of Normal Lung Tissue in Patients Treated with Stereotactic Body Radiation Therapy for Lung Tumors" by B Kavanah et al. will be at 1:30 p.m. on Monday, July 19 in room 204B of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-14065-14067-429.pdf
4) A LIBRARY OF LUNG TUMORS – THE LUNG IMAGE DATABASE CONSORTIUM AND IMAGE DATABASE RESOURCE INITIATIVE
A database of more than one thousand lung scans, the culmination of a nine-year effort on the part of seven academic institutions and eight medical imaging companies, has been completed and is now available to medical imaging investigators. The project will be presented by Samuel G. Armato III, Ph.D., associate professor of radiology at the University of Chicago, during the 2010 annual meeting of the American Association of Physicists in Medicine, July 18-22, in Philadelphia, PA.
The rationale for the project, according to Armato, was to assist developers of automated detection systems, often referred to as CAD (computer-aided diagnosis) by offering them a "standard of truth" against which to compare their methods. All of the images contained in the database are clinical CT scans (computed tomography) that were read manually by a team of four thoracic radiologists, working in two phases. In the first phase, each radiologist worked independently of the others; in the second phase, they reviewed one another's findings in order to achieve a more complete read of each scan.
The database contains 1018 CT scans and a total of 7371 identified lung nodules, as well as the radiologists' markings of the larger nodules' outlines and characteristics, including subtlety, spiculation, solidity and margin. The database contains both larger (greater than three millimeters) and smaller nodules. "There is a lot of discussion in the clinical community about the significance of small nodules," Armato said. The radiologists marked the smaller nodules to indicate their presence but provided more extensive information about the larger nodules.
The Lung Image Database Consortium (LIDC) was initiated by the National Cancer Institute in 2001 with the participation of five academic centers and expanded in 2004 by the Foundation for the National Institutes of Health to create the Image Database Resource Initiative (IDRI). "There was a huge commitment on the part of the NCI," said Armato, pointing out the "extent of academic and intellectual effort" marshaled toward the completion of the project.
The web site through which the database may be accessed is http://ncia.nci.nih.gov.
The presentation "The Lung Image Database Consortium (LIDC) and Image Database Resource Initiative (IDRI): A Completed Public Database of CT Scans for Lung Nodule Analysis" by S Armato et al. will be at 8:30 a.m. on Wednesday, July 21 in room 201B of the Philadelphia Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-14019-43804-664.pdf
5) TACTILE TUMOR-IMAGING DEVICE
Chang Hee Won and his colleagues at Temple University have made a novel tactile tumor-imaging device by exploiting the optical properties of waveguides -- which are planar, flexible and transparent probes.
Light traveling in a transparent waveguide will normally not leak out because of the principle of total internal reflection; if the refractive index of the guide is more than that of the surrounding material, a light ray approaching the wall of the guide will be reflected back into the guide. If, however, the guide becomes deformed because an object compresses the waveguide, then light can escape at that point. An imager will capture the light and from this image the mechanical properties of the objects may be determined.
In this case, the object in question is a tumor. In the case of the Temple research the waveguide consists of a flexible probe fed with light from a light emitting diode (LED). Light exiting the probe is caught on a camera, and from the emergent light the scientists are able to measure tumor diameters to within about 4 percent and tumor depths to 7.6 percent.
"We have performed a phantom study and [imaged] globus tumors in mice," says Won. "More sophisticated machines such as MRI will measure the size and depth more accurately, but the elasticity information is unavailable with MRI. Conversely, methods such as sonoelastography will provide the elasticity information, but this is a much more complex machine. Our device provides a means of detecting size, depth, and elasticity information in a relative simple device."
The next step, Won says, is to move from imaging mouse to human tumors with the device. This he is now doing with collaborators at the Thomas Jefferson University Hospital and Cooper University Hospital.
Small-scale human tests will be carried out within this year. Won says that this device has a potential to be used in breast cancer screening if it proves successful.
A website with more information: http://www.temple.edu/csnap
The presentation "Design and Evaluation of an Optical Tactile Imaging Device for Tumor Detection" by C Won et al. will be at 3:00 p.m. on Sunday, July 18 in the exhibit hall of the Philadelphia Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-13673-56966-519.pdf
6) MAKING TUMORS GLOW COULD REVEAL THEIR HIDING SPOTS
Getting a clear picture of a hidden tumor remains a major hurdle in cancer treatment. Researchers from the Stanford University School of Medicine hope to solve this problem with a molecular imaging system that uses X-rays to make tumor cells shine brightly.
The hybrid X-ray/optical imaging system relies on nanosize phosphors – imaging markers that convert X-ray energy to light. The markers are made of gadolinium oxysulfide and coated with either terbium (glows green) or europium (glows red).
In laboratory tests, the hybrid system showed a 260 percent contrast difference between simulated normal and cancerous tissue, the researchers report. A standard X-ray showed a 0.6 percent contrast difference.
The team also found that very low concentrations of the nano-phosphors produce high contrast pictures. "We have determined that the minimum detectable concentration is far lower than conventional contrast enhanced X-ray imaging, for the same dose, meaning that tumors may be detected at the earliest, most treatable stage," says lead author Colin Carpenter, a Stanford postdoctoral fellow.
The system could aid both drug discovery and disease treatment. For example, attaching the phosphors to certain biomarkers would help researchers better visualize the distribution and efficacy of new anti-cancer drugs, says Carpenter.
"However, in my mind, the most exciting application for this system is a device to aid surgeons in the complete excision of diseased tissue," he adds. "Currently, it is very difficult to remove all the tumor cells in the tissue, because surgeons don't have a tool that is sensitive enough. Allowing a real-time visualization of these tumor cells could significantly improve treatment."
The presentation "Development of an X-ray/Optical Luminscence Imager for Improved X-ray Contrast Sensitivity" by CM Carpenter et al. will be at 4:00 p.m. on Wednesday, July 21 in 204B of the Philadelphia Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-13965-51280-504.pdf
This research was supported by the NIH In vivo Cellular and Molecular Imaging Center at Stanford, the NSF and the DoD.
7) IMRT SAFE AND EFFECTIVE FOR TREATING CANCERS OF PARANASAL SINUS
Intensity-modulated radiation therapy (IMRT) appears to be a safe and effective treatment for cancers in the nose area, known as paranasal sinus cancers, new data suggest. This is a boon to patients suffering from a cancer that is difficult to treat due to its closeness to the optic nerve and the interactions of air and tissue that can disrupt precision delivery of radiation. Both hold potential for causing blindness.
But clinical outcomes are encouraging from a new collaborative study of 31 patients treated with IMRT at Fox Chase Cancer Center in Philadelphia. Notes Fox Chase lead researcher Aruna Turaka, M.D.: "Our results show there were no loss of vision or vision disturbances such as floaters, and preserving vision is always the main concern."
Researchers found no high grade complications to either vision or salivary function. With a median follow up of 27 months the 2- and 5-year overall survival rates were as high as 89%, for early stages, and declined with time to 66% at 5 years. A few patients had recurrent or residual cancer, but overall, Dr. Turaka says, "IMRT appears be a promising and well-tolerated treatment method."
The presentation "Intensity-Modulated Radiation Therapy (IMRT) for the Para-Nasal Sinus (PNS) Malignancies: Outcomes From Fox Chase Cancer Center (FCCC)" will be at 3:00 p.m. on Sunday, July 18 in the exhibit hall of the Philadelphia Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-12575-55394-995.pdf
8) NEW NANOTECHNOLOGY CAPSULE DELIVERS CANCER DRUG, THEN HEAT
Nanoparticles are tiny bits of metal and other materials that spark a lot of enthusiasm in the cancer research world because the particles can be precisely targeted to a tumor and therefore need lower doses to be effective. This translates into fewer side effects for patients.
Now there's more. Researchers at Baylor College of Medicine in Houston, Texas have developed a targeted nanocapsule system that delivers two cancer therapies simultaneously: the chemotherapy agent doxorubicin and heat therapy (hyperthermia).
"The great thing about our magnetic, nanoparticle-assembled capsule," explains lead researcher John McGary, "is that it's a multifunctional device that can be used simultaneously to release the desired drug concentration at the tumor site while heating up the tumor cells."
The system is based on nanoparticle-assembled capsules (NACs), structures that form themselves as a result of their chemical properties. The capsules contain the chemotherapy agent doxorubicin. An external magnetic field passed over the nanocapsule releases doxorubicin and also heats up the NAC solution, heating the tumor cells to more than 50° C to kill them.
NACs have been tested in the lab to study the release and heating rates. Future studies will test cell culture and animal studies, Dr. McGary says.
The presentation "Nanoparticle Assembled Capsules for Target Drug Delivery, Controlled Release and Hyperthermia" by J McGary et al. will be at 3:00 p.m. on Sunday, July 18 in the exhibit hall of the Philadelphia Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-13061-62578-357.pdf
This research was supported by the Mike Hogg fund and Golfers Against Cancer.
9) NEW MULTISOURCE X-RAY IMAGING TECHNOLOGY
Rather than use a single source of X-rays to image patients, scientists at GE Global Research have developed a way to use an array of separate sources, each of which covers a small portion of the patient. Each can be modulated in intensity so as to achieve sharp images with the lowest possible amount of radiation. Only one source is active at a time, and can be modulated so that within one position the desired intensity delivers a shaped dose. It's like a personalized CT scanner for each patient.
The GE sources achieve beam powers of 60 kW. Images are sharper than usual because the conical X-ray beams are narrower than for traditional CT machines and produce less scattered X-rays. This eliminates the need for baffles to block scattered X-rays (which would otherwise degrade the image quality), allowing still more detector cells to be brought into play. The detector in the inverse geometry CT system (IGCT) is about one-fifth the size used in conventional CT units. A higher active area also means the possibility of realizing smaller cells and higher spatial resolution.
According to GE scientist Kris Frutschy, multisource technology is at the research stage and is not yet commercially available. Furthermore, the reconstruction software will necessarily be more sophisticated for multisource systems since the data from all sources must be calibrated and combined.