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College Park, MD (July 18, 2006) –What Google-like techniques are medical physicists using to improve computer-aided detection of breast cancer?  How are robots superior to ordinary machines in treating lung cancer?  What is the risk of developing cancer from the very radiation that cured it? 

These and other questions will be addressed at the 48th Annual Meeting of The American Association of Physicists in Medicine (AAPM), which will take place July 30-August 3, 2006 in Orlando, FL, at the Orange County Convention Center.  Expected to be the most highly attended AAPM meeting to date, the conference will feature approximately 1250 scientific papers on subjects at the intersection of physics and medicine. The scientific program will begin on Sunday, July 30 at 8:00 AM and conclude on Thursday, August 3 at 5:30 PM.  Many of these topics deal with the development of state-of-the-art imaging and therapeutic devices for cancer, and the new techniques that go along with them.


The AAPM meeting webpage (http://www.aapm.org/meetings/06AM/) contains links to the full program.  The site's Virtual Pressroom contains expanded writeups on selected topics as well as other press materials.

Reporters who would like to attend the meeting should fill out the press registration form (http://www.aapm.org/meetings/06AM/VirtualPressRoom/PressReg06.pdf).   Even if you can't make it to Orlando, the Virtual Pressroom and this news release are designed to make it possible to write stories about the meeting from your desk.


The following highlights represent some of the many noteworthy talks that medical physicists will present at the meeting.                                                                   

  1. Radiation-Armed Robot Rapidly Destroys Human Lung Tumors
  2. Speeding Up a Computer's Second Opinion For Breast Cancer
  3. Carefully Mixed Radiation Cocktail Reduces Collateral Damage in Breast Cancer Patients
  4. 256-Slice CT Scanner Promises Faster Heart Images,  Lower Radiation Doses
  5. Molecular Beacons Fight Cancer, Shed Light on Cancer Cells' Inner Workings
  6. The Risk of Developing Cancer From Radiation Therapy

I. Radiation-Armed Robot Rapidly Destroys Human Lung Tumors
Super-intense radiation delivered by a robotic arm eradicated lung tumors in some human patients just 3-4 months after treatment, reports medical physicist Cihat Ozhasoglu, Ph.D., of the University of Pittsburgh Medical Center (ozhasogluc@upmc.edu).  Although it is too early to determine the technique's long-term effectiveness, Ozhasoglu and his colleagues find promise in this new approach to treat lung cancer and other moving tumors, such as those in the thorax and abdomen.

At the University of Pittsburgh, Ozhasoglu and approximately 30 colleagues form one of the largest US teams devoted to the CyberKnife, a commercially available radiation delivery system that uses an accurate, precise robotic arm to aim highly focused x-ray beams at the site of a tumor.   Recently, the Pittsburgh researchers upgraded their CyberKnife by adding a system called "Synchrony," which allows the robotic arm to deliver intense radiation accurately to tumors that move as a result of breathing. 

With their upgraded Cyberknife, the researchers have established detailed methods for delivering very intense levels of x-rays safely to a lung tumor, which otherwise couldn’t be treated with similar levels of intensity by more conventional radiation therapy machines because of their lack of sufficient real-time tracking accuracy. 

Treating lung tumors with the enhanced Cyberknife requires only 1-3 sessions lasting 60-90 minutes. In conventional radiotherapy, patients typically get dozens of radiation treatments, each lasting about 15 minutes but requiring 20-30 hospital visits.   To track the moving tumor, the CyberKnife takes real-time x-ray pictures of the patient while using external markers attached to the patient’s chest or abdomen to follow tumors in real time with a few millimeters of accuracy.  (Wednesday, August 2, 2006, 2:20-2:40 PM, Valencia A).

Expanded story at:

Lay-language Paper at:

II. Speeding Up a Computer's Second Opinion For Breast Cancer
To help computers provide faster "second opinions" on mammogram images showing suspicious-looking breast masses, medical physicist Georgia D. Tourassi, Ph.D., (Georgia.tourassi@duke.edu) and her colleagues at Duke University are employing a Google-like approach that retrieves useful information from an existing mammogram database more rapidly than before. 

Knowledge-based computer-assisted detection (CAD) systems compare a mammogram image to those of known cases of breast cancer in order to aid radiologists in their diagnosis.  Traditionally, CAD systems compare the mammogram image under investigation to every image of breast cancer in a computer database.  In contrast, the Duke technique compares the mammogram only to selected images that are most highly ranked for their information content.  This is analogous to how a Google search first returns a list of only those websites that it determines to have the most important and useful information on the words entered in the search.

Applied to an existing database of 2,300 mammography images, the Duke method compared a sample mammogram to 600 images it ranked as most informative. This cut down the time the CAD system took to analyze the mammogram by one-fourth, to less than 3 seconds per query. Such speed and efficiency will be important as CAD image databases rapidly grow larger and more complex.  In the next year, the researchers expect to follow up their pilot study with a larger investigation to evaluate the clinical impact of this new approach.  (Tuesday, August 1, 2006, 2:54-3:06 PM, Room 330A)

Expanded story at:

III. Carefully Mixed Radiation Cocktail Reduces Collateral Damage in Breast Cancer Patients
A carefully determined mixture of electron and x-ray beams precisely treated breast tumors while significantly reducing collateral skin damage in 78 patients.  The key to choosing the right mixture of beams, as well as their individual properties, was a sophisticated computer approach developed by medical physicists Jinsheng Li, Ph.D. (Jinsheng.Li@fccc.edu) and Chang-Ming Ma , Ph.D. of Fox Chase Cancer Center in Philadelphia. 

Using a procedure known as the "Monte Carlo" method, the computer simulations helped oncologists send optimally mixed, accurately targeted doses to 78 breast cancer patients receiving "hypofractionated" treatments, in which the patients were given fewer, but more potent, doses of radiation. The beams delivered all the radiation within a small margin of the tumor's edge, dramatically reducing radiation damage to surrounding healthy tissue. The researchers expect their approach to provide benefits for reducing collateral damage in the treatment of shallow tumors in the breast, chest wall, and head-and-neck region. (Tuesday, August 1, 2006, 2:30-2:45 PM, and Wednesday, August 2, 4:24-4:36 PM, Room 224A.)

Expanded story at:

Lay-language paper at:

IV. 256-Slice CT Scanner Promises Faster Heart Images, Lower Radiation Doses
Richard T. Mather, Ph.D. of Toshiba America Medical Systems (rmather@tams.com) in Tustin, California will describe a work in progress (WIP) prototype of the wide-area-detector "256-slice" CT scanner. 256-slice CT is a new imaging technology that can provide detailed images of the entire heart, including the coronary arteries, in less than half a second while requiring a fraction of the radiation dose that is traditionally needed [potentially as low as 2 milliSieverts (mSv) as opposed to the 13 mSv generally required in present state of the art CT equipment].  A followup to clinically successful "64 slice" CT machines, the 256-slice scanner, slated to be introduced clinically within the next 2-3 years, has the potential to routinely detect coronary artery disease and heart defects in a single test during an emergency-room visit or annual physical.  For this reason, Mather says, he and his colleagues hope this technology can help reduce healthcare costs, by potentially eliminating batteries of unneeded tests in certain cases.

When used in conjunction with an injected dye (contrast agent) that highlights the blood vessels in the heart, the machine's rapid imaging enables it to obtain valuable information on blood flow in the heart, and potentially uncover heart defects such as coronary stenosis, narrowing of the heart’s blood vessels, and cardiac shunts, the undesirable mixing of blood from the different heart chambers.

A challenge in developing the 256-slice CT scanner, Mather says, is that it forces advances in accompanying technologies. In addition to pushing forward the performance of wide-area detectors, the researchers are addressing existing limitations in image reconstruction, image processing, and data transfer technology as they prepare to bring the device to market.  (Monday, July 31, 2006, 4:25-4:50 PM, Room 330 D)

Expanded story at:

V. Molecular Beacons Fight Cancer, Shed Light on Cancer Cells' Inner Workings
The University of Pennsylvania's Jerry D. Glickson, Ph.D. (glickson@mail.med.upenn.edu) will discuss his group's creation of three different platforms for delivery of diagnostic and therapeutic agents to cancer cells: 1) lipoproteins [low-density lipoprotein (LDL),high-density lipoprotein (HDL), and chemically modified versions of LDL and HDL that target various cancer-associated receptors], 2) molecules that enter the cells through the glucose transport system; one class of molecules (easily detected by MRI) includes metal atoms attached to a glucose-like molecule , and 3) molecular beacons, inactive agents that can be activated into cytotoxic (cell-killing) agents interacting with specific messenger RNA molecules (mRNAs) or specific enzymes that the cancer cell produces  (Wednesday, August 2, 2006, 11:10-11:40 AM, Valencia B)

Lay-language paper at:

VI. The Risk of Developing Cancer from Radiation Therapy
The same medical radiation that destroys patients' tumors and saves their lives also risks creating new cancers at a later date, but it has been unclear how likely this risk may be.  With more and more cancer patients living for 20 or even 40 years after radiation treatment, a significant public health question becomes how much risk these patients face of developing such "secondary" cancers over the rest of their lives. 

To provide new insights into this question, Herman Suit, M.D., M.Sc. Ph.D., of Harvard Medical School and Massachusetts General Hospital (hsuit@partners.org) and his colleagues have examined a wide variety of studies of the effects of radiation on cancer patients, atom-bomb survivors, individual mammalian cells, and animal populations such as mice and rhesus monkeys.    As Suit found, there is no uniform relationship between radiation exposure and secondary cancer incidence; the relationship is highly variable in these diverse groups. 

While research has not yet uncovered tidy relationships between radiation dose and cancer risk, one thing is clear. Radiation exposure at all except at the low dose levels, e.g. 0.01 Gray (typical of a routine diagnostic x-ray exam), is known to heighten cancer risk.  However, the risk of radiation-induced cancer is difficult to quantify with accuracy as the risk in absolute terms is quite low and the heterogeneity of human populations is high.

For example, in a well-studied group of ~ 86,000 atomic bomb survivors, only 438, or 4.7%, of all the 9335 cancer deaths in this group over a 52-year period could be statistically attributed to radiation exposure from the bomb.  Other studies have measured patients' risks of developing cancer in individual organs after receiving radiation treatment for other nearby organs (full treatment for a solid cancer typically involves tens of Grays of radiation, and nearby healthy organs usually get a portion of this total dose).  Those patients receiving relatively high radiation doses to the stomach while being treated for another cancer increased their chance of developing stomach cancer from approximately 1% (the normal risk for an average member of the US population) to a heightened risk of about 4% for the rest of their lives. In contrast, there was no significant increment in risk of bladder or rectal cancer over the dose range of 1 to 60 Grays to those organs. 

Even though the current data are too incomplete to obtain clear answers, positive steps are now taking place to minimize secondary cancer risks. Especially in recent years, medical professionals have been making tremendous strides in increasing the precision with which radiation hits tumors and reducing radiation exposure to nearby healthy organs.  The rapid technical gains in this area are continuing "at a pace that must be described as exciting," Suit comments.  In addition, serious prospects exist, he says, for someday identifying patients who have increased genetic susceptibility to radiation-induced cancer and for managing their cancer treatments accordingly. (Wednesday, August 2, 2006, 10:05-10:35 AM, Room 224 A)

Meeting Abstract at:


The theme of the AAPM President’s Symposium this year is "Regulations, Regulations, Regulations!" Moderated by AAPM President E. Russell Ritenour, Ph.D., the symposium will feature top authorities in the U.S. describing the impact of government rules on the practice of physics in medicine.  Speakers will include Gregory B. Jaczko, Ph.D., the new commissioner of the U.S. Nuclear Regulatory Commission, and Daniel Schultz, M.D., Director of the Center for Devices and Radiological Health at the U.S. Food and Drug Administration (FDA).  Also presenting will be Robert R. Hattery, M.D., president of the Radiological Association of North America (Monday, July 31, 2006, 10 AM-12 PM, Valencia A).


The professional program features policy-oriented topics related to medical physics. One session deals with ethics and conflict of interests in publishing, research and patient care (Sunday, July 30, 9:30-11 AM, Valencia B). Another session explores how the modern publishing landscape, with its online access, greater international participation, and new options such as open-access publishing, affects legal, intellectual property, and other professional issues for medical physicists (Monday, August 1, 4:00-5:30PM, Room 230A).  A third symposium, moderated by Gerald A. White, Jr., M.S., of the Colorado Associates in Medical Physics and Michael Herman, Ph.D., of Mayo Clinic, is entitled "The Medical Physicist Defined" (Wednesday, 4-5:30 PM, Room 230A).


If you have ever had a mammogram, an ultrasound, an x-ray or a PET scan, chances are reasonable that a medical physicist was working behind the scenes to make sure the imaging procedure was as effective as possible.  Medical physicists help to develop new imaging techniques, improve existing ones, and assure the safety of radiation used in medical procedures.  They contribute to the development of therapeutic techniques, such as the radiation treatment and prostate implants for cancer.  They collaborate with radiation oncologists to design cancer treatment plans.  They monitor equipment and procedures to insure that cancer patients receive the prescribed dose of radiation to the correct location.  AAPM's annual meeting provides some of medical physicists’ latest innovations, which may be coming soon to a hospital near you.


AAPM (www.aapm.org) is a scientific, educational, and professional organization of more than 6,000 medical physicists. Headquarters are located at the American Center for Physics in College Park, MD. Publications include a scientific journal ("Medical Physics"), technical reports, and symposium proceedings.


For more information, please contact Ben Stein of the American Institute of Physics, bstein@aip.org, 301-209-3091, Jeff Limmer, AAPM Media Relations Subcommittee Chair, jeffl@aspirus.org, or Martha Heil, American Institute of Physics, 301-209-3088, mheil@aip.org