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    To answer your question we refer you to this website that describes an "alternative pathway" for experienced international medical physicists who wish to become certified by the American Board of Radiology:
    https://www.theabr.org/medical-physics/initial-certification/international-medical-graduates

    This letter to the editor of JACMP may be of interest, although it applies specifically to diagnostic imaging physics, not therapy physics:
    https://doi.org/10.1002/acm2.13166

    There are two types of biological risk from radiation that medical physicists focus attention on. One is a potential skin reaction if a large accumulation of radiation impinges upon a region of skin. The other risk is cancer initiated by an accumulation of radiation delivered to radiosensitive organs.

    The treatment that you received used a technique called interventional fluoroscopy to produce x-ray images that guided the placement of the stents and coils in your head. The numbers that you were given (2140 and 2100 mGy) is the cumulative air kerma to a reference point from each procedure. The reference point is defined in industry standards and is intended to approximate the location where the x-ray beam first hits the skin. When the skin dose exceeds about 2000 mGy, there is a potential for “transient erythema” which is a temporary reddening of the skin, like a sunburn(1). Since your reported values are just slightly above the 2000 mGy threshold, it is unlikely that you would have experienced erythema because in most cases the x-ray beam is moved around and the dose to any region of skin is less than the reported cumulative air kerma value to the reference point. Therefore the peak skin dose is very likely less than the threshold dose for early transient erythema. However, if you do notice skin changes in the area of your treatment, you should definitely bring it to the attention of your doctor.

    The second risk is an increase in the risk of cancer above the baseline risk that every human faces. This risk is difficult to quantify because our knowledge about radiation and cancer is derived from studies of people who received very high radiation doses to their entire body (for example, atomic bomb survivors, nuclear accident survivors, etc.). Applying this knowledge to medical patients who receive localized, smaller doses requires numerous assumptions. It is generally agreed that a radiation dose from medical imaging increases an individual’s cancer risk very slightly above the natural baseline lifetime risk of 42 diagnosed cancers for every 100 people(2). Higher doses are associated with increased risk, but even at the highest doses used in medicine, the overall increase in cancer risk is still quite small compared to baseline and depends on the age and sex of the patient. Using published values for the typical kerma-area product for cerebral neurovascular embolization for aneurysm (250-300 Gycm2)(3), a published dose conversion coefficient from kerma-area product to effective dose (0.087 mSv/Gycm2)(4), and a published cancer risk coefficient(2), a very rough estimate based on many assumptions is that 1 patient in 400 who undergoes cerebral coil embolization may develop a future cancer as a result of the radiation exposure, while about 168 of these 400 will be diagnosed with cancer from other or natural causes. Because of the high natural incidence of cancer in the population, it is impossible to know if an individual’s cancer resulted from a radiation exposure or if it would have occurred anyway.

    You had two procedures performed about six months apart. During the time interval between these procedures, your body’s natural DNA repair mechanisms had the opportunity to fix any DNA base pair mutations that may have been caused by the first radiation exposure. We have no way to quantify the degree of repair, but your body did have time to “heal” from the first exposure. For cancer risk, each radiation exposure is considered independent, and the second exposure carries no greater or less risk than the first.

    References:
    (1) https://www.iaea.org/resources/rpop/health-professionals/radiology/erythema
    (2) NAS/NRC National Academy of Sciences/National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation: Phase 2, BEIR VII, Board on Radiation Effects Research (National Academies Press, Washington), 2006.
    (3) Miller et al, Radiation Doses in Interventional Radiology Procedures: The RAD-IR Study Part I: Overall Measures of Dose. JVIR 14(6) 711-727, 2003. https://doi.org/10.1097/01.RVI.0000079980.80153.4B
    (4) NCRP Report No 160, Ionizing Radiation Exposure of the Population of the Unites States (National Council on Radiation Protection and Measurements, Bethesda, Maryland), 2009.

    To answer your question we refer you to this website that describes an "alternative pathway" for experienced international medical physicists who wish to become certified by the American Board of Radiology:
    https://www.theabr.org/medical-physics/initial-certification/international-medical-graduates

    This letter to the editor of JACMP may be of interest, although it applies specifically to diagnostic imaging physics, not therapy physics:
    https://doi.org/10.1002/acm2.13166

    Every diagnostic imaging exam is prescribed only if the benefits associated with it outweigh the potential risks. The information obtained from a CT exam can improve the clinical outcome for the patient by providing physicians with insights into what is going on inside the patient. As with every medical procedure, there are risks associated with a diagnostic imaging exam. A typical way to describe the risk associated with radiation from a CT exam is the effective dose. For a standard head exam, the effective dose is generally lower than 2 mSv (milli Sievert). To provide a comparison, the average annual natural background radiation in the US is 3.1 mSv. This means that by simply living on earth, each person in the US is naturally exposed every year to a radiation dose higher than the dose associated with a standard head CT exam. Therefore, we can reasonably say that the risk associated with a single head CT procedure is negligible, and the benefit to the patient from a medically necessary brain CT scan outweighs the radiation risk.

    Risk vs benefit is always taken into account for imaging using ionizing radiation. The risk of a screening mammogram is quite low: since a very large number of screening mammograms are done in the US every year, mammographic imaging procedures and radiation dose are closely regulated by the FDA. Screening mammograms are kept at a tightly regulated low dose. Physicists ensure that all of the x-rays produced by the machine fall on the imaging detector, which blocks direct x-rays from going to your uterus. Therefore, a lap apron is not necessary. Due to the positioning of the breast on the imaging plate (pulled away from the body), the amount of low-energy, low-dose scattered radiation that could possibly reach the vicinity of the uterus is incredibly small or negligible. In comparison, if you are at risk for breast cancer, the potential benefit – both for you and for your future baby -- of catching any problems early typically far outweighs the low risk!

    The radiation oncology team performs a lot of checks before, during and after treatment to make sure treatments are delivered as precisely and safely as possible. Before treatment, the patient will be set up in a way that will hold them still for every treatment, and their images are used to create a custom-made treatment plan for their body and their disease. During treatment, more imaging is used to make sure they’re positioned precisely where they need to be. The medical physicist(s) on the team will be doing behind-the-scenes checks during the whole process to make sure the treatment plan is correct, the machine is operating as it should, and the radiation dose delivered matches the plan.

    For most adults, 10 CT scans in a year does not carry a high risk of cancer development. In general, the risk of radiation causing cancer is a linear relationship with no lower threshold. That means the higher the radiation we received, the higher the risk for us to develop cancer will be. Depending on the type of CT scan, the radiation dose from that scan is approximately equal to the dose that everyone receives in one year from naturally-occurring sources on earth. After our body receives radiation, whether from medical imaging or from nature, the cells in our body will try to repair any cellular damage that may have occurred. In most cases, the cumulative radiation from 10 CT scans spread out over a year will be repaired and will not reach a dangerous level of cancer risk. In almost all cases, CT scans offer more benefit than risk. The information gathered from your CTs helps physicians diagnose and treat your medical ailment(s). This outweighs the small to negligible risk associated with the exposure to x-ray radiation during a CT exam.

    In general, no. Radiation treatment delivery is entirely a passive process. The length of treatment depends on the particular case, but usually the patient can expect to remain in the same position for approximately 20 minutes, which may cause some discomfort. Special devices are made for each patient to assist in holding still and minimizing discomfort. The radiation itself cannot be felt - just like with an x-ray, you won’t feel a thing.

    For PET/CT, the amounts of 18F-FDG excreted in breastmilk after a PET scan are below the level of concern for the breastfed infant and most international radiation safety organizations state that no interruption of breastfeeding is necessary. However, to follow the principle of keeping exposure "as low as reasonably achievable", some guidelines recommend withholding breastfeeding for 1 to 4 hours. Because of extensive uptake by lactating breasts and the consequent external radiation, nursing mothers should refrain from prolonged close contact with their infants for a period of time. Some authors suggest that the infant be bottle fed with expressed breastmilk by a third person for 1 feeding or 4 to 12 hours, depending on the dose, after a PET scan with 18F-FDG in a nursing mother. Ref: https://toxnet.nlm.nih.gov/newtoxnet/lactmed.htm

    For CT scans with an iodine-containing contrast agent, eg. Isovue 370, Intravenous iodinated contrast media is minimally excreted into breastmilk and minimally absorbed orally so it is not likely to reach the bloodstream of the infant or cause any adverse effects in breastfed infants. Guidelines developed by several professional organizations state that breastfeeding need not be disrupted after a nursing mother receives a iodine-containing contrast medium. However, because there is no published experience with iopamidol during breastfeeding, other agents may be preferred, especially while nursing a newborn or preterm infant. Ref: https://toxnet.nlm.nih.gov/newtoxnet/lactmed.htm

    No, patients do not need to cease breastfeeding after a chest x-ray exam. The x-ray interactions with the body are complete as soon as the machine finishes taking the image. There is no lingering radiation inside of the body.

    Both, protons and photons are used in the treatment of cancer by directing beams towards tumors and killing the cancer cells in the tumor when energy is deposited. The main difference between the two methods lies in the way the energy is deposited in the patient's body.
    Photons are highly energetic packets of light that travel at the speed of light. As photons enter the patient's body, they deposit most of their energy at the surface of the patient and the energy deposition weakens as the photons travel through the patient's body and finally exits the patient's body.
    In contrast, protons are electrically charged particles that upon entering the body, immediately begin slowing down as they deposit their energy. Protons deposit most of their energy immediately before they have given up all of their energy and come to rest. This leads to a peak in energy right before the protons come to rest, called the Bragg peak. The initial energy of protons may be adjusted in such a way that the protons come to rest in the tumor and minimal energy is deposited beyond the tumor. Therefore the healthy tissues that lie beyond the tumor may be spared better when compared with photons. This can be of great benefit to the patient in most cases.
    Accelerating protons to energies suitable for treatment of most cancers is technically difficult and expensive. Therefore there are far fewer proton beam therapy facilities available than photon therapy facilities. In some cases the energy deposition difference described above is not of the highest importance and photon therapy may be more beneficial to the patient. Radiation oncologists use scientific evidence to determine which radiation type is best for any given patient and tumor location.

    MRI is a commonly used imaging method that allows our doctors to see and better understand what is going on inside your body. Compared with other imaging methods such as x-ray, CT, and nuclear medicine,, MRI does not use high-energy radiation to create an image, and therefore it does not carry the very small risk of future cancer that is sometimes associated with x-rays and gamma rays. However, MRI has some unique safety considerations because of the strong magnetic fields and radio waves that are used. The magnetic field can attract some metals; therefore, let your doctor or the MRI technologist know if you have any metal on or inside your body. Use only the facility's provided clothing during the exam. MRI exams can be noisy, so you may be offered hearing protection. Some MRI scanner designs (the "narrow bore" type) can provoke feelings of claustrophobia in some patients. Contrast dyes are sometimes used, which may cause an allergic reaction in some patients.

    Indeed, some forms of radiation, specifically x-rays or photons, do penetrate through your entire body and will deposit some dose along their entire path of travel. However, the design of common linear accelerators is such that they can rotate around a single point where the radiation from different directions will add up together to collect significant dose. Tissues away from this common point will only see a small fraction of the radiation paths and collect minimal dose. This is similar to how a magnifying glass can focus the sun’s rays down to a single point and cause a quick burn on your hand while putting your hand out into the direct sun will simply feel a little bit warm.

    A dose volume histogram, or DVH, is a quick way to graphically show how much radiation dose a structure (like the heart) receives as part of radiation treatment. It shows how much dose is received by a percentage of the structure. It can give several important pieces of information, such as the maximum dose, minimum dose, or how much dose is received by 50% of the structure. However, it is important to know that a DVH does not give information about the location of dose, such as where the maximum dose is located in a structure.

    X-ray imaging is like creating a shadow using a light source and any object. When light shines on the object, the amount of light coming through the object will depend on the transparency of that object. With visible light, the shadow of a clear glass is very faint while the shadow of a rock of the same dimension is dark. This difference comes from the difference between the transparency of different objects. The same principle applies to x-ray imaging. The interesting property of x-rays is the ability to penetrate through human body. The penetration ability through an object or human body depends on the energy of x-rays; higher energy x-rays can penetrate through more tissue. For the same energy x-rays, penetration through the bone or through the muscle will be different (similar to light’s transmission through glass or rock). So, if we shine x-rays on the human body, a region with bone structure will allow less penetration and a region of muscle will allow more penetration. When these x-rays are collected using an x-ray film or a digital detector, a difference will be seen in terms of the number of x-rays at two locations and this relative difference allows the structures in your body to be visualized as an x-ray image

    Hopefully it won’t disappoint you to find out that radiation only makes people glow in comic books and movies. In reality, the radiation you will be getting is totally colorless and you shouldn’t feel anything at all from your treatment besides the applicator the physician has already placed. If you do feel anything during the treatment, please speak up and say so. We have cameras and an intercom so we can see and hear you at all times during the treatment even though we’ll be out of the room.

    Radiation can damage cells in the body. Healthy, normal cells are capable of repairing themselves following exposure to radiation. However, cancerous cells have lost this ability. When radiation is delivered to a part of the body containing a tumor, the cancerous cells are killed but the non-cancerous cells survive.

    Generally speaking, such websites should not be used to estimate your personal risk from an imaging exam. They use risk averages derived from the general population, including men and women, adults and children of all ages. Therefore, these values cannot be used to calculate an individual's risk which is unique for each person. If you are concerned about the safety of your exam, please contact the radiology or medical physics department of the facility where you had your exam. They will be able to answer any questions that you may have.

    Dental exams, like other x-ray exams, do not require any safety action after the end of the exam. There is no residual radiation after an x-ray. The effect of the x-ray radiation stops as soon as the exam ends and there are no lingering safety issues for the patient’s family members, friends, coworkers, etc.

    Normal cells are better at healing themselves than cancer cells. Multiple treatment “fractions” allow normal cells a chance to repair, while the intended radiation damage accumulates in the cancer cells. Also, small imperfections in the treatment setup can exist, such as exact patient positioning, body motion, internal organ motion, and the positions of moving parts in the treatment machine. By spreading the radiation therapy over a number of fractions, those small imperfections average out and their effect is decreased.

    Some types of cancer benefit from much higher dose per treatment. In that case, the physician may recommend “stereotactic” therapy in 5 or fewer fractions. In order to minimize technical imperfections, stereotactic treatments may use more devices to prevent patient motion and more imaging for accurate positioning

    In some ways, a medical physicist is like a pharmacist. The doctor writes a prescription of radiation for your cancer, and it is the job of the medical physicist to fill the prescription. First, we have to test the quality of the machines that are used to treat cancer. Every day we perform quality testing on the machines to ensure the safety of our patients. Second, with the help of other staff on the radiation therapy team, we develop a unique treatment plans to get the radiation where the doctor wants it and away from the healthy organs. Our quality checks do not stop when the treatment begins - during treatment we make continuous checks to ensure safety throughout the treatment, and verify the delivery of the radiation to the cancer.

    Proton therapy is a tool for doctors to treat cancer, and like X-rays, it is a form of radiation therapy. However because of protons' unique stopping characteristics (known as the Bragg peak), proton therapy can stop at an exact depth (cancer location) inside the body, whereas x-rays travel farther. Therefore, proton therapy has the potential of causing less harm to healthy organs that are near the location in the body where the treatment is intended. Depending on the type and location of cancer, proton therapy may be beneficial. For more information please visit The National Association for Proton Therapy’s webpage https://www.proton-therapy.org/.

    While you are inside the scanner, the various clicking, buzzing and vibration noises that you hear are produced by magnetic field gradient coils that localize the information inside your body and produces images. It is important to keep still while you hear these noises throughout the exam, or else the images produced will be distorted or blurred. The technologist should advise you when it is ok to move or adjust your position, such as during the quiet period in between imaging sequences. While imaging is taking place, it is generally ok to make small movements using parts of your body not in the imaging field, such as toes or fingers during a head or body exam.

    Inside the machine, known as a linear accelerator (or “linac” for short), there is a measurement device between the source of radiation and the patient. This device is called a “Monitor Chamber,” and it is used to monitor the amount of radiation being emitted by the linac. The Monitor Chamber collects electric charges created by radiation as it passes through the device. That electric charge is counted as “Monitor Units.” When a treatment plan is developed, we set a certain number of Monitor Units that we want to be counted with each treatment field. When we “turn on” the beam, the linac begins counting the Monitor Units, and when the number has been reached, the linac knows to turn off the radiation. For safety purposes, we have other safeguards to ensure that the number of monitor units is not exceeded and that the linac turns off the beam at the appropriate time

    Prostate seeds refers to a form of low-dose-rate (LDR) brachytherapy, which is a type of radiation therapy in which multiple, small, radiation-emitting devices are implanted directly into the prostate permanently. The procedure is conducted with the patient unconscious, and it is a one-time procedure. The dose to the prostate can be high and will give very little dose to normal organs at a distance from the prostate. The procedure is one of the many options of treatment available for prostate cancer.

    No. You are not radioactive and pose no risk to those around you. The radiation you were treated with is a special kind of energy delivered to your disease in the form of small particles (electrons) or waves (gamma or x-ray radiation). When delivered, some of this energy passes through, reflects off, or is absorbed by your body. The portion of that energy that does not pass through or bounce off the body is absorbed and transfers its energy to tissues (which is how it kills cancer cells). None of this energy remains as a radiation source inside of the body.

    This concept is distinct from the term “radioactive” which describes something that emits radiation as part of its physical nature. If you were treated via high dose-rate brachytherapy (HDR), you were treated with a form of the metal iridium which is radioactive. This source emitted radiation, which interacted with your body as described above, and then was retracted from your body. Since the radioactive source is no longer in your body, you are not radioactive and are no longer receiving the radiation. If you were treated with a linear accelerator, nothing radioactive ever entered your body.

    Medical physicists are clinician scientists who usually specialize in either diagnostic or therapeutic radiological physics. In the diagnostic setting, medical physicists contribute to the effectiveness of radiological imaging procedures by ensuring high image quality obtained safely, and the development of improved imaging techniques and technologies. In the therapeutic setting, medical physicists work in radiation oncology and contribute to the development, optimization, and quality control of therapeutic delivery techniques. They collaborate with radiation oncologists to design treatment plans and monitor equipment and procedures to ensure that patients receive the prescribed dose of radiation to the intended location.

    Medical physicists are technical experts in academic, industry, or hospital settings who apply physics knowledge to the diagnosis and treatment of disease. We usually spend our time doing some combination of patient care, research & development, and teaching. As a radiation oncology physicist, I consult with our physicians to make sure our team delivers safe and effective radiation treatments to cancer patients.

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