52nd Annual Meeting, Philadelphia, Pa., July 18-22, 2010
Next week the city of Philadelphia will host the 52nd annual meeting of the American Association of Physicists in Medicine (AAPM), the premier organization in medical physics, a broadly-based scientific and professional discipline encompassing physics principles and applications in medicine and biology.
Many of the presentations and symposia at the meeting are focused on patient safety -- tailoring therapy to the specific needs of people undergoing treatment, adding safeguards to enhance quality assurance, and finding ways to image children and adults safely at lower radiation exposures while maintaining good image quality, and more.
Some of the highlights of these presentations are listed below. Journalists are invited to attend the meeting for free. The meeting lasts from July 18 - 22, 2010, and registration information appears at the end of this release.
PATIENT SAFETY HIGHLIGHTS FROM THE MEETING
- Special Symposium: Medical Radiation and Patient Safety
- Reducing Radiation Dose -- and Future Cancer Risk -- in Pediatric Patients
- Risk of Radiation-Induced Cataracts Among Cardiologists
- Cancer Risks From Radiation Should Include Age, Sex
- IAEA "Smart Card" Effort to Create Radiation Passports
- From "Step and Shoot" to a Smooth Spiral -- Evolving CT Dose Assessment
- Medical Scanners Get a Check-Up
- Time Out Procedures Reduce Error Rates
- One Canadian Hospital's Encouraging Results Reducing Radiation Dose
- Safety Science: Emergency Off Systems
- New Data Management System Helps Promote Patient Safety
- Risks of Accurate Therapy -- Making Radiation Safer for Pediatric Patients
- Other Presentations of Interest
- More Meeting Information
1) SPECIAL SYMPOSIUM: MEDICIAL RADIATION AND PATIENT SAFETY
Recent radiation overdoses at three Los Angeles-area hospitals and one hospital in Alabama have thrown a public spotlight on the safety of procedures involving medical radiation. New efforts to improve patient safety are the focus of a special symposium at the 52nd AAPM meeting that brings together an investigative journalist and medical physicists. Recent technical failures and human errors will be addressed in light of new AAPM recommendations and IAEA efforts to provide better education and accreditation for staff, consistent systems for reporting medical errors, and a more comprehensive assessment of medical technologies by the FDA.
The discussion will take place from 2-4 p.m. EDT on Sunday, July 18. Speakers include:
- Walt Bogdanich, an investigative reporter for the New York Times, who will discuss his recent series of articles on radiation accidents
- William Hendee, professor at the Medical College of Wisconsin and editor of the journal Medical Physics, who will present safety recommendations developed at the AAPM symposium "Safety in Radiation Therapy -- A Call to Action" in June
- Michael Herman, professor at the Mayo Clinic and president of AAPM, who will describe ongoing efforts by the AAPM to improve patient safety, including dialogues with the FDA
- Ola Holmberg, head of the Radiation Protection of Patients (RPoP) unit at the International Atomic Energy Association, who will discuss IAEA efforts to prevent radiation accidents.
The "Special Symposium on Patient Safety" will be at 2:00 p.m. on Sunday, July 18, 2010 in Ballroom A of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-14600-67969-790.pdf
2) Reducing Radiation Dose -- and Future Cancer Risk -- in Pediatric Patients
PHILADELPHIA, PA (July 18, 2010) -- Children with cancer are monitored regularly, but can there be too much of a good thing? According to Dianna Cody, a professor of imaging physics at the University of Texas, M.D. Anderson Cancer Center in Houston, many children who survive cancer have a higher than average chance of developing a second cancer later in their lives.
"And we don't know," she says, "if that is because they have a genetic predisposition, or if it was due to the chemotherapy, the radiation therapy, or the diagnostic imaging. We want to reduce the risk of future cancer due to our component." The radiation exposure due to tumor imaging can be substantial, she adds, as some children are screened as often as every three months.
Cody and her colleagues will present results of a study aimed at reducing radiation exposure in pediatric patients today at the 52nd meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia.
Cody and her team took what she says were "logical steps." The CT (computed tomography) scanners used to visualize tumors are capable of modulating their radiation output based on the amount of tissue being scanned, ramping up in areas of relatively thick tissue such as the torso and tamping down in thinner areas such as the neck. Rather than having the machine operate at a static level throughout the process, the researchers instructed the machine to deliver a certain quality and then stepped back, allowing the instrument to "dial" itself up or down. They also consulted closely with the radiologists responsible for reading the CT images, to work on how high an image quality was actually necessary to make a clinical determination; that is, how much "noise" could be accepted before the tumor "signal" would be unreadable.
In an initial group of eight cases, the investigators were able to demonstrate that a reduction of radiation exposure by 23 percent could be achieved without compromising quality medical care.
The presentation "Our Experience Reducing CT Radiation Dose to Pediatric Populations" by K Mathieu, N Fitzgerald, and D Cody will be at 3:00 p.m. on Sunday, July 18, 2010 in the Exhibit Hall on Level One of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-12996-5072-477.pdf
3) RISK OF RADIATION-INDUCED CATARACTS AMONG CARDIOLOGISTS
PHILADELPHIA, PA (July 21, 2010) -- Some cardiologists who use fluoroscopy to image patients can be exposed to higher doses of radiation than radiologists. One danger for those exposed to higher levels of radiation is an increased level of eye cataracts.
Believing that interventional cardiologists and nurses who work in places where radiation protection protocols might not be fully employed are especially at risk, Madan Rehani and his team at the International Atomic Energy Agency (IAEA) in Vienna have investigated possible cataract links for catheterization laboratories staff in Bogota, Columbia; Montevideo, Uruguay; Kuala Lumpur, Malaysia; and Sofia, Bulgaria.
Rehani and his team, interviewed cardiologists and nurses in these cities, and eye specialists examined their eyes. They found that among cardiologists, 52 percent had developed some opacity in the lenses of their eyes; for nurses it was 45 percent, and for a control group it was 9 percent.
Rehani cautions that even though the correlation between radiation dose exposure and prevalence of lens change was high, a larger sample size needs to be tested to pin down the relation between dose and cataracts
Nevertheless, he says, "Radiation protection rules should be obeyed, as cataracts were observed at radiation levels lower than what are currently believed to cause cataracts.
The presentation "IAEA Study of Cataract in Staff Working in Catheterization Laboratories" by M Rehani will be at 8:30 a.m. on Wednesday, July 21, 2010 in Room 202 of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-14431-74473-551.pdf
4) Cancer Risks From Radiation Should Include Age, Sex
PHILADELPHIA, PA (July 19, 2010) -- The technique currently used in hospitals across the country to assess the cancer risk associated with CT scans doesn't take into account a patient's age or sex. But it should, according to Walter Huda of the Medical University of South Carolina in Charleston, who will present data today at the 52nd meeting of the American Association of Physicists in Medicine (AAPM) suggesting that these factors can have a significant impact on risk.
CT scans image the human body with X-ray radiation that can increase a person's chance of getting cancer. Radiologists estimate this risk with a number called an effective dose -- a calculation that includes both the dosage received by different tissues in the body and the sensitivity of different organs to these doses.
A typical chest X-ray scan might have an effective dose of 0.02 millisieverts. A CT scan of the abdomen, about 8 millisieverts.
"The assumption is often that a millisievert is a millsievert is a millisievert," says Huda. "But it's a very crude indicator of patient risk that can overestimate or underestimate your actual risk."
Using data from the National Research Council's committee on the Biological Effect of Ionizing Radiations (BIER), the most authoritative source on radiation risks, Huda investigated other factors that could impact a patient's risk.
He found that risk levels depended on the type of procedure being performed.
"A pelvic CT scan, an abdomen CT scan, or a chest CT scan might all have effective doses of 10 millisieverts, but the risks for each of those doses could vary by a factor of two or three," says Huda.
The sex of the person being scanned was also important. On average, a chest CT scan was 2.6 times riskier for women than men -- while a pelvic scan was 11 percent safer.
The age of a person had the biggest effect. Compared to an 80-year-old, the risk levels for a 20-year-old were five times higher in men and six times higher in women.
The presentation " How Well Do Effective Doses Predict Carcinogenic Risks in Body CT?" by W He and W Huda will be at 5:10 p.m. on Monday, July 19, 2010 in Room 204B of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-12725-73639-142.pdf
5) IAEA "SMART CARD" EFFORT TO CREATE RADIATION PASSPORTS
PHILADELPHIA, PA (July 22, 2010) -- Patients going from one radiology facility or one doctor to another, or indeed moving from one country to another, can leave a confusing trail of documentation about radiation exposure in radiological examinations. M. Rehani, who works at the International Atomic Energy Agency (IAEA) in Vienna, Austria, will report today at the 52nd meeting of the American Association of Physicists in Medicine (AAPM) on efforts to develop an international system for tracking patient exposures. The idea was first broached in 2001 but became an active program only around 2008.
Called a Smart Card/SmartRadTrack, the system ultimately may be something like an ATM card. It does not contain money on it but allows one to use the card to access money and account details. For the patient, radiation exposure history is sufficient whereas for health authorities radiation dose information is needed. Aggregate data obtained through the eHealth system would enable countries to establish radiation and exposure standards and help in future epidemiological studies. This would require manufacturers to develop equipment and software for tracking procedures and doses.
The presentation " IAEA Smart Card Initiative for Patient Exposure" by M Rehani will be at 8:30 a.m. on Thursday, July 22, 2010 in Room 202 of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-14438-62523-620.pdf
6) From "Step and Shoot" to a Smooth Spiral -- Evolving CT Dose Assessment
PHILADELPHIA, PA (July 20, 2010) -- CT scanning has undergone radical changes during its thirty-plus years in clinical use, but the way radiation dosage associated with scanning is assessed has not kept pace. That may change shortly, according to Dianna Cody, Ph.D., a professor of imaging physics at the University of Texas, M.D. Anderson Cancer Center in Houston.
"Current methods are not optimal," notes Cody, who said the methods used to calculate patient exposure are based on original CT (computed tomography) machines, which required that the object of analysis travel through the instrument's field in small increments. After each small movement, the machine took a reading - what investigators termed a "step and shoot" approach. These snapshots were then compiled to obtain the complete exam. Manufacturers have made great strides, however, and currently take continuous readings, collecting data in a spiral mode.
But determination of radiation exposure is still arrived at by assuming the patient is exposed in a planar mode and making mathematical adjustments to the calculation. Since CT is used for many types of medical diagnosis, and some patients being treated for conditions as diverse as cancer and kidney stones receive repeated exposure to the technique, a more straightforward and accurate means is desired by those in the field. This more direct method to assess radiation dose was developed by Robert Dixon, Ph.D., a professor at Wake Forest University in Winston Salem, North Carolina; it is becoming accepted as the CT dose assessment choice for the future.
Today at the 52nd meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia, Cody and her colleagues will cover this new approach based on modern CT scanners' helical motion around a center point in the field. She doesn't expect any new standard to be adopted immediately, she says. Rather, she expects it would "take a while for everyone to converge, and we'll probably be using both approaches for a while until a transition is made."
The presentation "Current and Future Measurements of CT Dose" by D Cody will be at 1:55 p.m. on Tuesday, July 20, 2010 in Room 201B of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-14529-33931-56.pdf
7) Medical IMAGING SYSTEMS Get a Check-Up
PHILADELPHIA, PA (July 19, 2010) -- Patients aren't the only ones getting check-ups in hospitals. The medical scanners that radiologist use to peer into the human body must be periodically tested to make sure that they are functioning efficiently and to minimize the radiation doses received during a scan.
Currently, no common standard exists for testing scanners used for digital radiography. Different healthcare facilities use different, subjective procedures.
"There are inconsistencies between hospitals, and it can be difficult to assess which machines are actually performing well," says Andrew Kuhls-Gilcrist of the University at Buffalo, N.Y.
Today at the 52nd Annual Meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia, Kuhls-Gilcrist and his colleagues in Professor Stephen Rudin's group at the UB Toshiba Stroke Research Center will describe how they have developed one possible solution -- a standard calibration method that bridges the gap between the laboratory and the clinic. They've adapted the precise techniques used by scientists to test new scanner technologies into a simple, effective procedure suitable for a bustling healthcare facility.
"If it's not easy, if it's not accurate, no one is going to use it," says Kuhls-Gilcrist, who is the AAPM Junior Investigator Winner.
The procedure takes about ten minutes. A radiologic technologist pushes the button on the X-ray equipment to acquire a few "blank" images. Then a computer program automatically analyzes the noise in these images and calculates a range of quantitative measurements such as the detective quantum efficiency, which indicates how effectively a scanner uses each dose of radiation. Other measurements of instrument noise check for problems that could affect the image quality of low-dose procedures such as fluoroscopy.
This method of quality assurance procedure has proven to be just as accurate as tests used by scientists in the laboratory, in which expensive, precisely-fabricated objects with near-perfect straight edges are imaged.
The presentation, "A New Simple, Accurate, and Quantitative Approach for Routine Quality Assurance in Digital Radiography" by A Kuhls-Gilcrist, D Bednarek, and S Rudin will be at 4:00 p.m. on Monday, July 19, 2010 in Room 204B of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-12777-99871-601.pdf
8) Time Out Procedures Reduce Error Rates
PHILADELPHIA, PA (July 22, 2010) -- Imagine the following announcement: "Our patient is Ken Chu. We are amputating his left arm. Does everybody agree?"
Welcome to a hypothetical "Time Out" (TO) statement and question set, a standard operating room procedure among surgeons to reduce errors by assuring the patient receives the correct treatment.
And now Ken Chu, PhD-who happily has both arms and is Chief Medical Physicist at Marquette General Hospital in Michigan-has conducted a study whose data argue for extending the TO requirement to radiation oncology operators nationwide. He will present this work today at the 52nd meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia.
"This simple procedure of taking the time to say, 'Correct patient name?-birthday?...treatment site?...dose?...gantry angle? Do you agree?' If it's all good, then you beam on," explains Chu.
Results show implementing TOs led to a threefold reduction in radiation errors. To implement TOs takes just 15 seconds of verbal discussion per radiation beam.
Dr. Chu reviewed radiation error records from five different cancer centers in New York and Michigan over 2000-2009. During that period, TO protocols were adopted at all centers, allowing him to compute error rates before and after TO implementation.
Says Dr. Chu: "This is an amazingly powerful safety assurance check that hospitals administrators would support since it is already implemented in other areas of the hospital to reduce errors."
The presentation "Implementation of a "time Out" Procedure in Radiation Oncology: A Multi-Institution Study Over Nine Years Results in a Three-Fold Reduction in Misadministrations" by B Rasmussen and K Chu will be at 10:36 a.m. on Thursday, July 22, 2010 in Room 203 of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-12987-2450-892.pdf
9) One Canadian Hospital's Encouraging Results Reducing Radiation Dose
PHILADELPHIA, PA (July 21, 2010) -- Late last year, after a number of stories on diagnostic medical CT scanning began appearing in newspapers, more and more people began to express concern about their procedures and to inquire about dangers of X-ray radiation, recalls Elena Tonkopi, a medical physicist at Queen Elizabeth II Health Sciences Center in Halifax, Nova Scotia.
When an increasing number of these calls coming her way, Tonkopi was prepared to answer them. "If patients are worried," she says. "They need to hear from somebody who can provide them with information." All the radiologists, technologists and medical physicists in her department are conscious of radiation exposures, she adds, and they all support strategies aimed at reducing dose.
In fact, when the calls started coming in, she was just completing a project with her colleagues Dr. Andrew Ross and Anita MacDonald to increase safety for patients by optimizing and lowering the CT radiation dose that patients receive while undergoing PET/CT examination -- a common procedure for cancer staging
Today at the 52nd Annual Meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia, Tonkopi will describe the results of that effort. Using nothing but available techniques for protocol optimization provided by the manufacturer, her department gradually lowered the average CT dose for patients undergoing PET/CT by about one third (32 percent) without sacrificing image quality -- something that can suffer if dose is lowered too much.
"It was interesting to compare the studies of the patients who had examinations before and after this optimization," Tonkopi said, calling the results "encouraging." She added that they may lead other institutions to follow suit. Before beginning the optimization experiment, her colleague Dr. Ross, who is Division Head Nuclear Med at Queen Elizabeth II Health Sciences Center, contacted several other medical centers in Canada that offer PET/CT and found that they expected about the same level of dose for the same procedures.
The presentation "CT Radiation Dose Optimization in Whole-Body PET/CT Examination by E Tonkopi, A Ross, and A MacDonald will be at 5:10 p.m. on Wednesday, July 21, 2010 in Room 201C of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-13026-36971-93.pdf
10) Safety Science: Emergency off systems
PHILADELPHIA, PA (July 18, 2010) -- In all interactions with technology, rigorous safety standards are imperative. But so is practicality -- and sometimes the two aren't joined.
Physicists at the University of Alabama in Birmingham emphasize this point in their statistical study of Emergency Off Systems (EOS) procedures for computer-controlled linear accelerators that deliver radiation cancer treatments in hospitals. Some states require EOS of accelerators to be tested at exactly three-month intervals, to the calendar day. But the researchers' results show EOS tests performed on any day within the 3rd month after the last check pose no significant risk to patients. And it would certainly be more practical by reducing staff stress.
"A safety regulation can actually be counter productive when it creates a false feeling of security -- and also, because it diverts resources from other areas," explains Ivan Brezovich, PhD, director in the Division of Radiation Physics and the lead investigator on the study, which he and his colleagues are presenting today at the 52nd Annual Meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia.
"Regulators need to consider both the short-term and extended-term impacts of a safety policy," Brezovich adds.
The presentation "Safety Considerations Concerning the Scheduling of Emergency Off Switch Tests" by I Brezovich and R Popple will be at 10:24 a.m. on Thursday, July 22, 2010 in Room 203 of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-13500-88849-73.pdf
11) New Data Management System Helps Promote Patient Safety
PHILADELPHIA, PA (July 18, 2010) -- Every 20 seconds, somebody in the United States is diagnosed with cancer, and each year hundreds of thousands of people will discuss possible next steps with their doctors and decide to undergo treatment with radiation therapy. This overarching decision, once reached, sets the wheels in motion for the treatment team, as doctors, nurses, medical physicists, technologists, and other specialists work together to devise and carry out the best treatment plan possible for each patient. That's how it's supposed to work.
Now a team of medical physicists at Washington University School of Medicine has developed a new web-based infrastructure that they say will enhance the current quality management paradigm and help to improve safety for patients by collecting, analyzing, and interpreting all the data related to the treatment. This includes data on machine performance, software performance, and more in one centralized database that can be accessed anywhere at any time during the treatment process. They call this system Quality Assurance Information System (QAIS). Currently, patient records in many hospitals and clinics often reside partly on paper and partly electronically -- and sometimes on multiple machines that can't access one another.
"The idea is to make the whole system electronic," explains Washington University medical physicist Dharanipathy Rangaraj, who will describe the new system today at the 52nd Annual Meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia. "The electronic environment for QA data would facilitate solving several challenges in quality assurance in radiation therapy," he says.
Rangaraj and his colleagues envision that their new system QAIS will make many things easier by facilitating opportunities to develop tools such as an automated electronic chart plan checking (EcCk) tool, an automated machine log file analysis tool (DynaQA) for every treated beam, an automated QA plan generation tool to reduce errors and variability, and workflow monitoring to evaluate system status, collecting errors and near misses as they occur to improve organizational learning. Also it would facilitate record keeping, auditing, and assurance of hospital, state, and federal compliance. The system is also designed to enhance safety and quality for each individual patient by incorporating automated alerts and warnings and by allowing users to access the data and check patient charts at any step of a procedure in ways that otherwise would not necessarily be available.
"Infrastucture such as QAIS should help institutions and private clinics to understand the treatment practices, determine best practice, benchmark practices and ultimately standardize health care treatment in radiation therapy," Rangaraj adds. "We are in a verge of a QA revolution in radiation oncology and QAIS is a step in the right direction."
The presentation " An Infrastructure Towards Better and Safer Radiation Therapy- Quality Assurance Information System (QAIS)" by D Rangaraj, K Moore, L Santanam, S Yaddanapudi, D Yang, S Goddu, R Brame, S Mutic, and D Low will be at 3:00 p.m. on Sunday, July 18, 2010 in the Exhibit Hall on Level One of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-14261-67279-23.pdf
12) Risks of Accurate Therapy -- Making Radiation Safer for Pediatric Patients
PHILADELPHIA, PA (July 18, 2010) -- Visualization of tumors can guide radiation therapy in a specific and effective manner, but the methods used to image and direct therapy typically themselves involve radiation. This is particularly a concern in pediatric patients, because they are far more susceptible than adults to radiation-induced late effects such as growth retardation and second malignancies.
Jun Deng, Ph.D., an associate professor of therapeutic radiology at the Yale University School of Medicine, will present at the 52nd meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia today results that detail how much radiation children are exposed to and how it might be reduced.
Deng and his colleagues examined a common imaging technique known as kVCBCT (for kilo-voltage cone beam computed tomography) used for tumor localization during image-guided radiation therapy. Although kVCBCT is frequently applied nowadays, sometimes daily or more for certain lesions, there are currently no commercially available tools to calculate radiation exposure for kVCBCT scans. Deng and his colleagues used a Monte Carlo simulation code developed specifically for the purpose to monitor exposure in four pediatric patients. They found that kVCBCT imaging delivered "considerably larger doses" to critical organs and bony structures in children, by a factor of 2 to 3 times more than in adults. A typical kVCBCT imaging procedure in children can result in a dose to certain organs that is equivalent to about 5000 chest x-rays, and during a several week course of daily radiation treatments, the imaging procedure may be repeated many times.
"Image guided radiation therapy is the way to go," Deng says, emphasizing that the increased accuracy with imaging makes it possible to eradicate some tumors that may not be curable otherwise. But, he says, it is essential to evaluate and incorporate the doses induced by imaging as part of the treatment plan and to carefully choose an appropriate scanning protocol for kVCBCT, in order to minimize late effects due to unwanted radiation to nearby organs at risk while maximizing cure. Many of these radiation-induced side effects occur several years after irradiation, which may not be a serious concern for the elderly adults but is critical for children.
"Many pediatric patients survive their primary cancers and have a long life ahead of them," says Deng. "Therefore, we must include imaging doses in treatment plans to ensure that the pediatric patients have a good quality of life after radiotherapy."
The presentation "Investigation of KV Imaging Doses in the Radiotherapy of Pediatric Cancer Patients by J Deng, Z Chen, K Roberts, and R Nath will be at 1:30 p.m. on Sunday, July 18, 2010 in Exhibit Hall - Area 4 on Level One of the Pennsylvania Convention Center.
ABSTRACT: http://www.aapm.org/meetings/amos2/pdf/49-13212-37092-250.pdf
MORE MEETING INFORMATION
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.
In addition to the highlights above, other presentations at the AAPM meeting will cover topics ranging from new ways of imaging the human body to the latest clinical developments on treating cancer with high energy X-rays and electrons from accelerators, brachytherapy with radioactive sources, and protons.
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