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Radiation & Safety Q&A
If you have a question about radiation being used in a medical setting then get in touch via Twitter (@senseaboutsci) or email firstname.lastname@example.org and we'll put your questions to the BIR & IPEM panel members.
"In an episode of House an inmate has an MRI scan which causes him a great deal of pain because of his tattoos - supposedly they contain 'heavy metals' - is this in anyway an accurate portrayal of reality? I have a tattoo - would I be prevented from having an MRI scan?"
Andy Rogers: "Skin reactions to scans of tattoos are rare. However, there have been a few very rare reports of skin reactions around tattoos in patients either with excessively large tattoos or body art which may have used heavy metals or iron oxides. This is because these substances are conductive and can increase the heat on the skin.
During an MRI scan, certain types of tattoos may heat up if they are inside the region being scanned; in exceptional conditions some burning may occur around the tattoo (in extreme cases leading to blistering). For people with facial or genital tattoos or large tattoos (greater that 7.5cms across), such burning could be particularly inconvenient or uncomfortable and may require medical care.
People may feel tingling at the site of the tattoo during scanning if it is going to heat up, and this provides a warning of a potential problem.
Patients should be asked if they have tattoos on an imaging screening form. Procedures will be in place to end the scan if patients feel any heat or sensitivity.
Whether the MRI scan would be prevented would depend on the location of the tattoo."
1: “What is the difference between CT and X-ray?”
Jennifer Poveda: “X-rays are high energy rays that can be transmitted through the patient and detected on the other side. Bones absorb the x-rays more than soft tissue, and these differences produce a ‘shadowgraph’ of the patient.
CT scanners use X-rays and tend to give higher doses than ‘plain x-rays’. During a CT scan, the patient lies inside a ‘tunnel’ while the x-ray tube and detector rotate very quickly around them. Hundreds of x-ray images are taken and processed to create very detailed images of the patients’ cross section.”
2: “What is the difference between MRI and X-ray?”
JP: “MRI scanners do not use ionising radiation; they use a strong magnetic field instead. Human bodies contain a lot of water. When the patient is in the MRI ‘tunnel’, the strong magnetic field causes the water molecules to line up, and they do this in different ways depending on the tissue type. These differences allow us to form an image of the different tissues in the body.”
3: “I’ve had loads of X-rays. Can this affect my fertility?”
Dr David Wilson: “Radiation exposures are prescribed by medical practitioners and supervised by radiologists who are doctors with specialised training in using ionising radiation for medical purposes. They will have followed national guidelines on the amount of radiation dose which require that they balance the small risks associated with radiation against the potential harm of not having an investigation. They also will have followed the principle of using the lowest dose practical for the investigation. They will have been aware of your age and gender. It should be pointed out that the cumulative dose of radiation used for diagnostic imaging have some low level risks associated with their use but are well below a dose that would damage fertility in the long term.”
4: “Is an interventional radiologist a qualified surgeon?”
DW: “Interventional radiologists are doctors who take additional training in the diagnostic use of radiation for at least 5 years and then further training in the use of image guided procedures that may be an alternative to surgical procedures. Some interventional procedures treat conditions where conventional surgery is not possible. Unlike open surgery, where an incision is the norm, interventional procedures use needles and devices inserted into the body through small punctures. The key difference is that these methods use imaging to guide the procedure and those with additional training in this field have the required skills. There is a large cross over in specialist skills nowadays, interventional radiologists often teach surgeons new procedures and work on the same case together. Interventional radiologists will see patients before treatment, work with medical teams to create a treatment plan, perform the procedures, handle any complications and then follow up their patients. It is becoming difficult to define what a surgeon is but all these professional groups have extensive training and work to high standards often in close collaboration.”
5: “My garden backs on to a mobile ultrasound scanning unit. Am I in danger from radiation?”
JP: “No, ultrasound scanners do not use any ionising radiation. Ultrasound ‘does what it says on the can’, the scanners produce high frequency sound waves to make medical images. The output from these are concentrated from the end of the probe and do not travel more than a few centimetres in air.”
6: “Will radiotherapy make me infertile?”
Dr Alexandra Stewart: “Having radiotherapy to certain areas of the body may affect fertility for both men and women, this is mainly when receiving radiotherapy to the pelvis. It is important to discuss these issues with your doctor as it may be possible to perform procedures before radiotherapy such as sperm banking for men which allows future pregnancies to occur.”
7: “What is the difference between chemotherapy and radiotherapy?”
AS: “Chemotherapy is the treatment of cancer with drugs and radiotherapy is the treatment of cancer with radiation, usually strong X-rays. Both can be used to cure cancers and they are also used to decrease the risk of cancer returning after surgery. Sometimes the two are used together as chemo-radiation to improve the efficacy of the radiotherapy and make cancer cells more likely to be killed than with radiation alone.”
8: “Why is Proton Therapy supposed to be a “better” or more sought after treatment?”
AS: “Proton therapy is a type of radiotherapy that uses protons to deliver the radiotherapy rather than the photons that most radiotherapy use. The dose delivered by protons decreases more quickly than photons after the dose has been delivered meaning they may be able to spare normal tissues some of the dose. This is useful in certain areas of the body and often in children in whom prevention of long term effects is more important. Not all patients will benefit from proton therapy but the small number that do currently have to travel abroad for the treatment, which is funded by the NHS. The UK government has committed to setting up two proton centres in the near future so patients will no longer have to travel abroad for treatment.”
9: “If I have had scans in different hospitals, how do hospitals keep a track of how much radiation I have been exposed to?”
Nicola Macdonald: “Hospitals don’t do this as each image taken is dealt with individually, they can see your previous images though so you won’t have images repeated simply because you’re at a different hospital. Each x-ray is only taken once the risks have been weighed up against the benefits and you’ll only be given a radiation exposure if it is going to affect your care at that time.”
10: "As I’m pregnant, can I be with my child when he/she has an X-ray?"
Andy Rogers: “There are two competing issues here. The first is the need to have a quiet, relaxed child during an x-ray procedure to maximise the quality of the image (wriggling kids cause blurring in the image making it harder to interpret and potentially missing small details). The second is the risk to both the mother and fetus from the scattered radiation that hits them if they are helping to support their child during the x-ray procedure. The current UK dose constraint to the fetus of a pregnant radiation worker is 1mSv and any scattered dose to the fetus from diagnostic procedures will be at least 100x less than this. In other words the benefit from the mother calming her child (if required) vastly outweighs any radiation risk to the unborn child or mother."
Imaging and pregnancy
11: “What special precautions should I take to avoid radiation whilst pregnant?”
NM: “If you are attending hospital and require to have an x-ray examination which could give your baby a radiation dose this will be assessed by the doctors and may be postponed if possible. If required to keep you healthy then the staff will take measures to minimise the dose used. In day-to-day life you are unlikely to encounter levels of radiation which could cause harm to your baby.
If you work with radiation, the three key principles are Time, Distance and Shielding. 1. Minimise the time spent near radiation sources. 2. Maximise the distance between yourself and the source, whilst still carrying out your necessary duties. 3. Use the protection provided whether this is lead glass screens or lead aprons. Your Radiation Protection Supervisor will give you more specific advice.”
Devices and radiation
12: “How much time can a child safely spend using a mobile phone?”
NM: “Mobile phones do not use ionising radiation. This means they use lower energies of radiation so the only proven side effects are localised heating when phone calls are being made. There are no current guidelines but minimising the duration of calls may minimise the risks.”
13: “Do tablets, iphones etc give off harmful radiation?”
JP: “These devices do not give off ionising radiation; however, they do use radiofrequency (RF) electro-magnetic fields. Research has concluded that RF field exposures below guideline levels do not cause health effects in adults or children. Caution is recommended because this data is only based on the last 15 years that mobile phones have been in widespread use. Radiofrequency Exposures from devices held further away from the body such as laptops etc are even lower than those from mobile phones.”
14: “Should I worry if I live near power lines?”
NM: “The level of electro-magnetic radiation a person can be exposed to by power lines is very low. At present, there is a very small increased risk of childhood leukaemia amongst populations living very close to power lines. There is no evidence of risk to the adult population.”
Meet the panel:
Dr David Wilson MBBS BSc MFSEM FRCP FRCR (radiologist) St Luke’s Hospital
Dr David Wilson is a radiologist at St Luke’s Hospital, Oxford. Dr Wilson’s primary interest is in the application of modern imaging techniques to disorders of the locomotors system. He has undertaken original work in the application of diagnostic ultrasound to joint, muscle and soft tissue disease with particular attention to joint effusion and congenital dysplasia of the hip. Dr Wilson is President of the British Institute of Radiology.
Dr Alexandra Stewart DM, MRCP, FRCR Clinical Lead for Oncology, Consultant Clinical Oncologist, Royal Surrey County Hospital
Dr Alexandra Stewart is a Consultant Clinical Oncologist with a special interest in pelvic cancer and brachytherapy. She qualified in 1997 and trained at Charing Cross and the Royal Marsden Hospitals with a Fellowship at Harvard University in Boston. Her clinical interests include the improvement of radiotherapy dose delivery in pelvic cancer, using conformal radiotherapy and/or brachytherapy.
Alex is Course Director for the Harvard Medical School annual brachytherapy review. She gives lectures, organizes the course and runs practical workshops.
Nicola Macdonald, Principal Physicist/RPA, Radiation Protection Service, Medical Physics, NHS Lothian
Nicola is a Clinical Scientist working in Medical Physics for NHS Lothian (Edinburgh) specializing in Radiation Protection. She is a Radiation Protection Adviser and gets involved with monitoring staff and patient doses, investigating Radiation Incidents and planning new facilities to ensure that doses are kept As Low as Reasonably Practicable.
Jennifer Poveda, Medical Physicist, NHS
Jennifer has worked in various disciplines of Medical Physics for over twenty years and is currently a Radiation Protection Advisor in an NHS teaching Trust in the East Midlands. She also serves on the Radiation Protection Special Interest Group of IPEM.
Andy Rogers (medical physicist), Head of Radiation Physics, Medical Physics & Clinical Engineering, Nottingham University Hospitals NHS Trust
Andy Rogers is on the working group that will advise the DH on the EU Basic Safety Standards revision as well as the National Research Ethics Service. He has recently joined the international standards organisation IEC to represent the UK in a project looking at the use of dose data held in digital imaging modalities along with being a member of an ICRP working group drafting a report on Diagnostic Reference Levels. He is also a Vice President of UKRC, leading on the ‘Advances in Technology’ stream. His current research interests are observer studies in radiology using simulated computer images and skin dose assessment in interventional radiology and cardiology.