[ RadSafe ] Medical physics meeting features innovations coming to a hospital near you

[Herren, Roy WS.]

 <http://www.eurekalert.org/meetings.php>
<http://www.eurekalert.org/meetings.php> [ Back to EurekAlert! ]
<http://www.eurekalert.org/meetings.php> Public release date: 28-Jun-2005

Contact: Ben Stein
 <mailto:bstein at aip.org> bstein at aip.org
301-209-3091 

Phillip Schewe
 <mailto:pschewe at aip.org> pschewe at aip.org
301-209-3092 

 <http://www.aip.org> American Institute of Physics 


4D proton therapy, radiation-resistant tumors, interpreting medical images


Medical physics meeting features innovations coming to a hospital near you


College Park, MD, June 28, 2005 - How can the act of simply imaging a tumor
reveal cancer regions that will be invulnerable to normal levels of
radiation? What are the biggest errors in reading image scans and how can
they be fixed? What recent advances are making subatomic protons
increasingly desirable for treating lung tumors? What can local governments
do to better prepare for radiological emergencies? 

These and other questions will be addressed at the 47th Annual Meeting of
the American Association of Physicists in Medicine (AAPM), which will take
place July 24-28, 2005 in Seattle, WA at the newly expanded Washington State
Convention & Trade Center, located at Pike Street and 7th Avenue. The
scientific program will begin on Sunday, July 24 at 8:00 AM and conclude on
Thursday, July 28 at noon. Approximately 1152 papers will be presented on
subjects at the intersection of physics and medicine. Many of these topics
deal with the development of state-of-the-art imaging and therapeutic
devices, and the new techniques that go along with them. 

CONTENTS 

This news release begins by containing information on how to cover the
meeting, then describes the President's Symposium on the World Year of
Physics as well as some public-policy sessions, and concludes by
highlighting six scientific papers/sessions at the meeting. 

HOW TO COVER THE MEETING 

The AAPM meeting webpage ( <http://www.aapm.org/meetings/05AM/>
http://www.aapm.org/meetings/05AM/) contains links to the full program.
Starting in early July, a Virtual Pressroom will contain additional meeting
tips, lay-language papers, and press releases. Reporters who would like to
attend the meeting should fill out the press registration form (
<http://www.aapm.org/meetings/05AM/documents/pressreg.PDF>
http://www.aapm.org/meetings/05AM/documents/pressreg.PDF) by July 15. Even
if you can't make it to Seattle, the Virtual Pressroom and this news release
are designed to make it possible to cover meeting highlights from your desk.
For assistance in contacting researchers and setting up interviews, please
do not hesitate to contact the science writers listed at the top of the news
release. 

PRESS LUNCHEON 

A press luncheon featuring some of the most newsworthy topics at the meeting
will be held in room 401 between 12:00-1:30 PM on Tuesday, July 26. Topics
will include 4D proton therapy, lighting up radiation-resistant cancer
regions, first clinical trials of a mammography alternative, and
image-guided radiation therapy (IGRT), in which onboard imaging equipment
guides radiation more precisely than previously possible during a cancer
therapy procedure. Further details will be given in an upcoming news
release. RSVP Ben Stein at  <mailto:bstein at aip.org> bstein at aip.org by July
15 if possible. 

PRESIDENT'S SYMPOSIUM FEATURES EINSTEIN AND THE WORLD YEAR OF PHYSICS 

The AAPM President's Symposium, moderated by AAPM President Howard Amols,
which focuses on the World Year of Physics that has been declared for 2005 (
<http://www.wyp2005.org/> http://www.wyp2005.org/). John Rigden (
<mailto:jrigden at aip.org> jrigden at aip.org), a physicist, historian, and
popular science writer, will discuss how in a period of six months, one
week, and two days, in 1905, Einstein wrote five papers that helped form the
bedrock of modern physics. Medical physicist Peter Almond (
<mailto:palmond at mdanderson.org> palmond at mdanderson.org) will talk about the
concurrent early history of radiation physics, and how news of Wilhelm
Roentgen's 1895 discovery spread like wildfire and led quickly to medical
uses of x rays. 

TERRORISM RESPONSE, MEDICAL ERRORS, INSURANCE REIMBURSEMENT 

A weeklong series of professional symposia will cover various public policy
issues that affect the general public. On Wednesday, July 27, at 10:00 AM,
Janice Adair, the Assistant Secretary of Washington State's Division of
Environmental Health, will describe emergency preparedness and terrorism
response training for professionals at the statewide level. On Thursday,
July 28, at 10:00 AM, Debra McBaugh, the chairperson of the Conference of
Radiation Control Program Directors, will discuss how medical physicists
have unique skills that can assist states in terrorism response. McBaugh was
part of the State of Washington's team that participated in a national
exercise that included responding to a simulated dirty bomb attack. Other
sessions throughout the week cover topics such as how Medicare and Medicaid
reform are affecting insurance reimbursement of radiological procedures,
medical errors, the impact of recent Nuclear Regulatory Commission training
and experience regulations on the handlers of radioactive material in
diagnosis and therapy, and reforms in the radiological health programs at
the FDA. 

HIGHLIGHTS OF THE SCIENTIFIC PROGRAM 

The following is a sampling of some of the many noteworthy talks that
medical physicists will present at the meeting. 

I. PROMISING FIRST IMAGES FROM HUMAN CLINICAL TRIALS OF MAMMOGRAPHY
ALTERNATIVE
II. LIGHTING UP RADIATION-RESISTANT TUMOR REGIONS 
III. READING BETWEEN THE LINES OF MEDICAL-IMAGE INTERPRETATION 
IV. TREATING LUNG CANCER WITH 4D PROTONS 
V. HYBRID MACHINE PERFORMS MRI AND RADIATION THERAPY 
VI. ELECTRON TECHNIQUE IMAGES CRUCIAL OXYGEN LEVELS 

I. PROMISING FIRST IMAGES FROM HUMAN CLINICAL TRIALS OF MAMMOGRAPHY
ALTERNATIVE 

Researchers will present some of the first images from human clinical trials
of breast CT imaging, a potential improvement over traditional mammography
that aims to catch breast cancer earlier while eliminating patient
discomfort. Traditional mammograms involve squeezing the breast between two
plates and firing an x-ray that images the breast all at once. In breast CT,
the patient lies down on a table and places one breast at a time through a
circular opening, while a CT scanner produces 300 images per breast, in a
period of just 17 seconds, to build up 3D images. 

According to the inventors of the new approach, including John Boone of the
University of California at Davis ( <mailto:jmboone at ucdavis.edu>
jmboone at ucdavis.edu), the technique has the potential to catch tumors that
are the size of a pea, as opposed to the garbanzo-sized tumors that can be
caught with standard mammography, while not requiring painful breast
compression. In addition, the 3D images can catch buried tumors that are
ordinarily obscured by 2D mammograms. 

At the AAPM meeting, Thomas Nelson of the University of California at San
Diego ( <mailto:tnelson at ucsd.edu> tnelson at ucsd.edu) will present some of the
first images from the clinical trials. Nelson and his colleagues report that
the breast CT images show impressive detail of the unique tissue structure
of the breast and high-contrast glandular detail. If the first clinical
trial successfully demonstrates that breast CT can detect tumors as well as
mammograms, a larger-scale clinical trial, which can occur in as early as 2
or 3 years, will test if the technique can detect tumors earlier than
mammograms. Breast CT will expose the patient to about as much radiation as
a standard mammography. (Paper SU-EE-A2-3, Sunday, 2:15 PM; for more
information, see
<http://www.ucdmc.ucdavis.edu/newsroom/releases/archives/cancer/2005/breast_
ct5-2005.html>
http://www.ucdmc.ucdavis.edu/newsroom/releases/archives/cancer/2005/breast_c
t5-2005.html). 

Meanwhile, researchers at the University of Rochester, the University of
Massachusetts, and Duke University are also independently pursuing breast CT
machines as an alternative to standard mammography. 

II. LIGHTING UP RADIATION-RESISTANT TUMOR REGIONS 

Andrei Pugachev of Memorial Sloan-Kettering Cancer Center in New York (
<mailto:pugachea at mskcc.org> pugachea at mskcc.org) will present progress
towards reliably finding and imaging regions of a tumor that are not
destroyed by ordinary levels of radiation. 

Like an overdeveloped mall built suddenly in a small town, aggressive tumors
overwhelm their surroundings; they often grow faster than the blood vessels
supplying oxygen to them. Such fast-growing tumors often contain "hypoxic
regions," or areas of lower-than-normal levels of oxygen. As it turns out,
these hypoxic tumor regions are resistant to radiation. That's because when
radiation damages DNA in a tumor cell, oxygen is needed to carry out
additional chemical reactions to make the damage permanent. 

Currently, there are radioactive tracers that, when injected into the blood
supply, will tend to bind to hypoxic regions in tissue and light them up for
doctors to see in a PET scan. Unfortunately, however, some tracers behave
very differently in different tumors, and their accuracy in mapping hypoxic
regions is not known. 

Pugachev and colleagues have devised a technique for verifying that PET
tracers work as intended. They compare how a PET tracer distributes itself
in a tumor to the distribution of a proven marker of hypoxia, such as the
chemical pimonidazole. In animal studies of prostate tumors, they found that
two specific PET tracers were reliable and one was not. 

By validating PET tracers in a two-step process (first, using animal tumor
models and then patient tumor biopsies), researchers hope that they will
soon be able to produce reliable, in-vivo images of hypoxic tumor regions
(Paper MO-D-I-609-8, Monday, 1:30 PM). 

III. READING BETWEEN THE LINES OF MEDICAL-IMAGE INTERPRETATION 

Properly interpreting a medical image can involve a life-or-death decision
about the course of a patient's treatment. In recent years, computers have
helped image perception in two ways. First, algorithms can be used to
process digital information to make images clearer, such as by enhancing
contrast. Second, algorithms can aid in detecting and possibly classifying
lesions. 

But there are still plenty of chances for errors in interpretation.
Sometimes a radiologist will make a mistake; they might miss lesions (false
negatives) or report something as positive when in fact there is nothing
there (false positives). 

Elizabeth Krupinski ( <mailto:krupinski at radiology.arizona.edu>
krupinski at radiology.arizona.edu,
<http://www.radiology.arizona.edu/krupinski/index.html>
http://www.radiology.arizona.edu/krupinski/index.html), who holds joint
appointments in the radiology and psychology departments at the University
of Arizona, is a leader in Medical Image Perception research, which seeks to
discover the root causes of interpretation errors and find ways to avoid
them. She is the first of several speakers on this topic at session
WE-E-I-609 (Wednesday, 3:30-5:00 PM), which is designed to highlight the
importance of medical image perception research to a community of
researchers that may not be that familiar with the topic or know why it is
important. 

As Krupinski points out, the radiologist is the final link in the imaging
chain. He or she holds the final responsibility for interpreting the image
data and making a diagnostic decision that will affect patient care. Hence
there is a need for examining how the radiologist views images and what
factors influence the interpretation process. 

IV. TREATING LUNG CANCER WITH 4D PROTONS 

Compared to the x rays traditionally used in radiation therapy, protons
offer the ability to destroy lung tumors just as competently while
inflicting less damage to surrounding healthy tissue. 

In a small experimental patient study, researchers have increased the
effectiveness of using protons to treat lung tumors. In traditional
radiation therapy, one must use multiple beams of x-rays to deliver a
uniform dose to a lung tumor; often at least one of the x-ray beams will
exit from the healthy (non-tumor-containing) lung and potentially damage it.
On the other hand, positively charged, subatomic protons only travel a
limited distance through the body; they never make it to the other lung, and
they also are more likely to spare nearby organs such as the esophagus and
heart. 

In any radiation treatment of the lung, it is a challenge to keep the
radiation on target while the tumor moves as a result of patient breathing.
In the 4D approach, one takes into account how the patient's breathing moves
the lung back and forth over time (the fourth dimension) so that the
radiation hits the tumor precisely over all phases of a patient's breathing
cycle. 

Now, researchers at Massachusetts General Hospital have applied the 4D
approach to proton therapy. In a study of four patients, they have found
that planning and carrying out 4D proton therapy delivers excellent dose
levels to lung tumors in all cases. 

The only thing preventing this technique from wider use is the need to
develop an algorithm that cuts down the currently lengthy time it takes to
calculate and plan the proton beam's direction and intensity for each
breathing phase. The 4D approach is also applicable to radiation therapy
using carbon ions, which is currently being used to help defeat lung cancer
in a couple of centers in Japan. (Paper WE-E-J-6C-7, Wednesday, 3:30 PM;
contact Martijn Engelsman, now at MAASTRO clinic, Netherlands,
<mailto:martijn.engelsman at maastro.nl> martijn.engelsman at maastro.nl) 

V. HYBRID MACHINE PERFORMS MRI AND RADIATION THERAPY 

Combining MRI imaging and cancer radiation therapy in a single procedure
addresses the problem of maintaining accurate positioning while performing
radiotherapy over a period of several days or more. A procedure developed by
a collaboration of scientists at University Medical Center Utrecht
(Netherlands), Philips Research Hamburg (Germany), and Elekta Oncology
Systems (Great Britain) uses a slightly modified commercial MRI unit
surrounded by a movable accelerator (producing 6-megavolt beams of electrons
to generate x rays). The whole process of tumor imaging and dose delivery is
under computer control. 

According to Jan Lagendijk ( <mailto:J.J.W.Lagendijk at radth.med.uu.nl>
J.J.W.Lagendijk at radth.med.uu.nl,  <http://www.radiotherapie.nl>
www.radiotherapie.nl), he and his colleagues expect that this new design
will become the next-generation radiotherapy treatment machine. The superior
image quality of the MRI available on line during treatment should have a
large impact on the design of individualized radiation-therapy treatment
plans. (MO-E-J-6B-3, Monday, 4 PM; for another recent hybrid machine that
combines MRI and x-ray methods, see a June 2005 Physics Today article at
<http://www.physicstoday.org/vol-58/iss-6/p22.html>
http://www.physicstoday.org/vol-58/iss-6/p22.html). 

VI. ELECTRON TECHNIQUE IMAGES CRUCIAL OXYGEN LEVELS 

Taking advantage of the properties of electrons in certain biochemical
compounds, Charles Pelizzari ( <mailto:c-pelizzari at uchicago.edu>
c-pelizzari at uchicago.edu) and his colleagues use a novel technique to form
images of the oxygen distribution of small animals with millimeter spatial
resolution. 

Developing these tools at the Center for In-Vivo EPR Imaging directed by
Howard Halpern at the University of Chicago, the researchers create these
important maps of oxygen levels by magnetically manipulating the unpaired
electrons in certain oxygen-containing molecules such as free radicals. Most
electrons in atoms and molecules form pairs that mutually cancel out their
internal magnetic properties, but unpaired electrons can give the
atom/molecule "paramagnetic" properties that cause them to be weakly
attracted to an external magnetic field. 

Electron paramagnetic imaging (EPRI) obtains pictures of molecules with
unpaired electrons in a similar way that MRI obtains images of atomic nuclei
such as the hydrogen in water: an image is formed when paramagnetic
molecules, lined up in a magnetic field, absorb and then re-emit
electromagnetic waves in or near the microwave portion of the spectrum.
Using a series of magnetic fields that vary in strength over a given region
of space, these emissions can be reconstructed into a 3D image. 

Where EPRI is advantageous over MRI is in providing quantitative images of
the distribution of oxygen in living tissues. Oxygen, or its absence, is
central to many diseases; it is a factor in cancer aggressiveness and in the
response to radiation and chemotherapy. Pelizzari expects that one day this
EPR methodology will obtain submillimeter-resolution maps and also be scaled
up to human dimensions. A potential long-term benefit of EPR imaging should
be in providing quick feedback on the results of cancer therapy in days or
even hours, without the use of radioactivity. In their talk at the meeting,
Pelizzari's group will present EPR oxygen images superimposed on MRI
anatomical images (WE-D-I-609-8) 

###

ABOUT MEDICAL PHYSICISTS
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
to a hospital near you. 

ABOUT AAPM
AAPM ( <http://www.aapm.org> www.aapm.org) is a scientific, educational, and
professional organization of more than 4,700 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