- DETAILED DESCRIPTION OF PROPOSED PROJECT
- Aims and objectives
The health risk assessment of MRI is incomplete yet and a number of gaps in our knowledge about the ill-effects of MRI have been identified. The effects of exposure to static fields above 8 T are not known. Only a little is known about the increased sensitivity of some people to CNS stimulation by the electric fields in switched gradient fields. There are concerns about the increased heat loads on infants and pregnant women. Hence, well-targeted research is required to complete the health risk assessment (Health Protection Agency, 2008). In the present research, we will conduct experimental and epidemiological studies to investigate the effects of static magnetic field greater the 8 T on pregnant women and their fetuses.
The specific objectives of this study are:
- Justification
Magnetic Resonance Imaging (MRI) is routinely used for diagnosis in most areas of the body and in most of the clinical specialties. It uses three main components to produce images from the body viz. a static magnetic field, a time-varying gradient and a radiofrequency. The clinical applications of MRI include standard imaging, functional MRI and contrast imaging. Different hazards have been assigned to the three components of the MRI system. The acute biological effects associated with movement in static field are vertigo-like sensations. However, the sensitivity to these effects varies from individual to individual. The Health Protection Agency advises that the patient should be moved slowly into the scanner so as to minimize the vertigo and nausea. Switched gradient fields may cause uncomfortable and painful sensations. Hearing protection is given to all patients because of the excessive noise levels in the scanner (Health Protection Agency, 2008; De Wilde, Rivers, Price, 2005).
The circumstances for fetal exposure in MRI may include several situations: The patient may not be aware she is pregnant, direct imaging of the fetus may be required to confirm an abnormality, direct imaging of the expectant mother may be required, pregnant MRI staff may be exposed to the radiation, etc. Studies done on the experimental animals have shown the abnormalities and developmental issues in the fetus. In case of humans, the studied factors (fertility length of gestation, birth weight, pregnancy outcome and offspring gender) revealed no statistically significant association with working in MRI. However, the heating during MRI may result in a range of abnormalities such as neural tube and cranio-facial defects. Hence, there is a clear need for further research into the effects of MRI in pregnancy (De Wilde, Rivers, Price, 2005).
- Present state of knowledge presented as a brief review of the relevant literature
Most MRI scanners in clinical use employ superconducting magnets with cylindrical bores and produce static fields of magnetic flux density from 1.5 to 3.0 T. However, ultrahigh field MRI scanners produce magnetic field in the rage of 4.7 to 9.4 T and are under investigation in various research institutions. MRI scanners with time-varying magnetic fields induce electric fields in the body and lead to current flow and subsequent heating of the body. Patients undergoing MRI examinations are exposed to static magnetic field, time-varying magnetic field, radio-frequency field and acoustic noise for a considerable length of time. Computational dosimetry provides the predictions about the electric field and current produced inside the body during MRI. It can also predict the temperature rise inside the body. ICNRIP recommends the static magnetic field of 4 T (maximum) during the whole body exposure in routine procedures. However, an upper limit of 8 T is recommended for specific examinations outside the normal operating mode (Health Protection Agency, 2008).
Several structures of the human body are affected by the static magnetic fields such as retina, pineal gland and cells of the paranasal sinuses. The attraction of ferromagnetic materials towards the magnet of the MRI instrument is another safety issue. Devices made of ferromagnetic materials such as surgical tools and medical implants attracted to the magnet. Hence, the individuals in or near the MR instrument could be seriously injured by this projectile effect. In order to prevent the accidents caused by projectiles, all equipments brought into the scanning room such as wheel chairs, trolleys, etc. should be of non-ferromagnetic materials. There are several safety issues to be considered by the radiologists, clinicians, radiographers, nurses and medical physicists while MRI examinations. Injuries from MRI and radiotherapy accidents are occurring more frequently now and there is an urgent need for the implementation of safety guidelines during these procedures (Ng, Ahmad, Nizam, Abdullah, 2003).
Nurses, fire department, emergency and MR personnel should be educated to the potential risk and hazards of magnetic field. Signs should be posted to prevent the entry of ferromagnetic materials into the scanning room. Unauthorized persons including carers escorting patients and general public must be accompanied by an authorized person who is responsible for them in the scanning area (Ng, Ahmad, Nizam, Abdullah, 2003; Society of Radiographers, 2013).
Malpractice issues in radiology have been highlighted by Berlin (1996) wherein the author exemplifies the effects of radiation exposure onto a pregnant patient. The author discusses several anomalies in the fetus after the radiation exposure. However, the data presented in this article is not comprehensive and updated. Nonetheless, it was recommended by the author that all radiologic facilities should have a process to identify pregnancy in women of child-bearing age. The radiologists and radiation physicists should discuss the risks of radiation exposure with such patients (Berlin, 1996). The Society and College of radiographers (SCoR) and the British Association of Magnetic Resonance Radiographers (BaMRR) have issued certain safety guidelines regarding MRI. For MR procedures on pregnant women, the safety of both the mother and the developing fetus needs to be carefully considered. Scanning should only be recommended after consideration of risks and benefits of using MRI including assessing the suitability of alternative imaging modalities. Wherever possible, the scanning should be done within normal operating modes and low SAR & quite pulse sequences should be used (Society of Radiographers, 2013). Stanford hospitals and clinics recommend that the pregnant female workers can receive no more than 0.5 rem during the entire gestation period and no more than 0.05 rem each month because of the increased health risk to the rapidly developing embryo and fetus (Stanford Hospital and Clinics, 2012). Several governments are amending the radiation protection regulations to minimize the risk for pregnant workers and those who are breast feeding (Canadian Nuclear Safety Commission, 2013).
Apart from MRI, radiation therapy is another arena in which the cancer patients are exposed to high doses of radiation. Hazard et al. studied the effects of adjuvant radiation and interferon-alpha 2b therapy in high-risk melanoma patients. It was concluded that patients receiving the adjuvant therapy may experience more severe radiation toxicities (Hazard, Sause, Noyes, 2002). Another study conducted to evaluate the long-term efficacy and safety of radiotherapy combined with carboplatin also raised serious concerns (Levin, et al., 2002).
(d) Method
- Studies will be conducted on pregnant female volunteers (or staff) to see the effects of static magnetic field above 8 T. Follow up studies of pregnancy outcomes will be done. Cohort study of long-term effects in highly exposed staff volunteers will be done.
- Survey will be sent to the MR centers in the predetermined area. The questionnaire of the survey will be designed to assess three aspects viz. maternal MRI diagnosis, fetal MRI and pregnant MRI staff.
- Voxel phantoms, based on digital images recorded from scanning of real persons by MRI, will be used to calculate the radiation dose to organs and tissues. Phantoms have been developed for infants, children, adult males and females depending on the body height, weight and organ masses. CT/MRI images from pregnant females will be segmented with respect to the reproductive organs and fetus. The segmented images will be assembled to form a three dimensional voxel matrix. The masses of all relevant organs will be adjusted to match the reference values given by ICRP89 for female reference adult. The effective dose for a pregnant female will be calculated based upon the anatomical specifications (Kramer, et al., 2004).
- EQUIPMENT
(a) Equipment required: MRI
(b) Access to the equipment:
- TIME PERIOD REQUIRED
Indicate whether the project will be undertaken full-time or part-time and in which
(a) Commencement
(b) Completion of various stages
(c) Write up commencement
(d) Completed first draft
(e) Completion of final report
(f) Oral seminar
Note: the final report and seminar should be completed by the end of the central
examination period of the relevant semester.
- FINANCIAL ASSISTANCE
List any institution or private organisation which will assist financially, where
applicable.
- COSTS
Expected costs to QUT, ie
(a) equipment, components and consumables
(b) workshop time and technical assistance
(c) other costs
Indicate the source/s of funds to cover the costs.
- ETHICAL APPROVAL
Any project involving human or animal experimentation requires ethical approval
external institution where the project is undertaken (if applicable). It is not necessary
eventually proceed with the project.
- HEALTH AND SAFETY RISK ASSESSMENT
It is a statutory requirement under the Workplace Health and Safety Act that a health
and safety risk assessment of all projects be undertaken before the commencement
of the project. It is not necessary to do for PCN218 purposes however the relevant
forms are to be completed and submitted if you proceed with the project.
Bibliography
Berlin, L., 1996. Malpractice issues in radiology. American Journal of Roentgenology, 167, pp.1377-1379.
Canadian Nuclear Safety Commission, 2013. Proposals to amend the radiation protection regulations. [pdf]. Canada’s Nuclear Regulator. Available from < http://www.nuclearsafety.gc.ca/pubs_catalogue/uploads/DIS-13-01-Proposals-to-Amend-the-Radiation-Protection-Regulations.pdf> [Accessed 02 June 2014].
De Wilde, J.P., Rivers, A.W., Price, D.L., 2005. A review of the current use of magnetic resonance imaging in pregnancy and safety implications for the fetus. Progress in Biophysics and Molecular Biology, 87, pp.335-353.
Ga, J., Rummeny, E.J., Seemann, M.D., 2004. Whole-body imaging with MRI-PET. European Journal of Medical Research, 9, pp.309-312.
Hazard, L.J., Sause, W.T., Noyes, R.D., 2002. Combined adjuvant radiation and interferon-alpha 2b therapy in high-risk melanoma patients: The potential for increased radiation toxicity. International Journal of Radiation Oncology Biology Physics, 52(3), pp.796-800.
Health Protection Agency, 2008. Protection of patients and volunteers undergoing MRI procedures. Advice from the Health Protection Agency. [pdf]. Available at <www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1222673275524> [Accessed 02 June 2014].
Hill, D.L.G., Mcleish, K., Keevil, S, 2005. Impact of electromagnetic field exposure limits in Europe: Is the future of interventional MRI safe? Academic Radiology, 12, pp.1135-1142.
Kramer, R., Khoury, H.J., Vieira, J.W., et al., 2004. All about FAX: A female adult voXel phantom for Monte Carlo calculation in radiation protection dosimetry. Physics in Medicine and Biology, 49(23), pp.52.
Levin, V.A., Yung, W.K.A, Bruner, J., et al., 2002. Phase II study of accelerated fractionation radiation therapy with carboplatin followed by PCV chemotherapy for the treatment of anaplastic gliomas. International Journal of Radiation Oncology Biology Physics, 53(1), pp.58-66.
Ng, K., Ahmad, A.C., Nizam, M.S., Abdullah, B.J.J., 2003. Magnetic resonance imaging: Health effects and safety. Proceedings of the International Conference on Non-ionizing Radiation at UINTEN (ICNIR2003), pp.1-15.
Society of Radiographers, 2013. Safety in magnetic resonance imaging. [pdf]. Society of Radiographers. Available at < www.sor.org/printpdf/book/export/html/9396> [Accessed 02 June 2014].
Stanford Hospital and Clinics, 2012. Radiation protection guidance for hospital staff. [pdf]. Stanford hospital and clinics, Lucile Packard Children's Hospital and Veterans Affairs Palo Alto Health Care System. Available at <www.stanford.edu/dept/EHS/prod//Hospital_Guidance_document.pdf> [Accessed 02 June 2014].
