- Email: [email protected]
ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice
Radiography xxx (2013) 1e6
Contents lists available at ScienceDirect
Radiography journal homepage: www.elsevier.com/locate/radi
ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice Christine Rodgerson* British Columbia Cancer Agency, 600 W 10 Ave, Vancouver V5Z 4E6, Canada
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 May 2013 Received in revised form 9 November 2013 Accepted 14 November 2013 Available online xxx
Purpose: There is little discussion in the literature regarding paediatric imaging dose reduction with respect to conventional imaging carried out in radiotherapy departments. This is in contrast to diagnostic radiography where dose optimization when imaging children is a very current topic. For this reason Canadian radiotherapy clinics were surveyed to look at paediatric imaging practice, knowledge and perspectives with respect to imaging dose reduction. Method: As this was an exploratory study, a questionnaire was developed and sent to radiation therapy clinics across Canada, via email, to assess knowledge of paediatric imaging and dose reduction initiatives. The questionnaire focus was CT simulation and treatment verification imaging of children. Results: Practice and knowledge of paediatric imaging varied across Canada. Forty percent of clinics reported using paediatric specific protocols for CT simulation and 20% of clinics reported using paediatric specific protocols for treatment verification imaging. There was variation in imaging practices among the clinics that reported treating the most children. The survey results show that while some measures are being taken to reduce paediatric imaging dose in radiation therapy, 46.7% of the respondents felt more could be done. Conclusion: The survey demonstrates interest in dose reduction in radiation therapy imaging as well as differences in current practice and knowledge across Canada. Paediatric imaging dose reduction would appear to be an area of practice that would benefit from more study and development of standards of practice. Ó 2013 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.
Keywords: Imaging dose reduction Paediatric radiation therapy ALARA Paediatric imaging guidelines
Introduction Reducing imaging dose in paediatric patients is important as children are up to ten times more sensitive to radiation induced toxicities than adults1 and are susceptible to a larger anatomical area being irradiated due to their small size.2 This has led to a worldwide effort to reduce radiation dose to paediatric patients from diagnostic imaging supported by the World Pediatric Imaging Federation (WPIF),3 the Image Gently (IG) campaign,4 the International Atomic Energy Agency (IAEA),5 and the Food and Drug Administration (FDA) in the United States.6 The Image Gently campaign started in 2007 with the goal to change diagnostic
* Tel.: þ1 604 877 6000x672723 (work); fax: þ1 604 877 6039. E-mail address: [email protected].
imaging practice by increasing awareness of the opportunities to lower dose when imaging children. The IAEA suggests that children are a special case in terms of standards and guidelines for radiation protection5 and according to the FDA, the “increased radio sensitivity of paediatric patients compared to adults makes it important to adjust equipment settings to optimize radiation exposure to paediatric patients for all types of X-ray imaging exams.”6 In addition to an increase in diagnostic imaging procedures over the past decade, there has been an increase in imaging procedures related to radiotherapy planning and treatment. Radiation treatment planning can involve patients undergoing multiple computed tomography (CT) scans. Intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) treatments are now commonly available and often require image guided radiation therapy (IGRT) to ensure the patient is in the correct position for these precise treatments.7e9
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Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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IMRT and VMAT treatment techniques, along with increased treatment verification imaging, can lead to increased amounts of normal tissue receiving low dose radiation.8,9 Paradoxically, new treatment techniques such as IMRT and VMAT can lead to greater protection of normal tissue from the effects of radiotherapy with a resulting decrease in both acute and chronic side effects of radiation treatment.7 The American Association of Physicists in Medicine (AAPM) tasked a group to look at ways to mange imaging dose from IGRT.8 In 2007 this group concluded that imaging doses are not negligible8 and for IGRT, a balance of risks versus benefits must be determined.6e8 Children comprise a very small fraction of patients treated in radiation therapy departments with some departments rarely, if ever, treating paediatric patients. With such small patient numbers, it can be difficult to create expertise in paediatric imaging. Children can have a number of different treatment requirements in comparison to adult patients such as awareness of late effects, the possible need for anaesthesia during treatment, and a need to customize procedures for children.10 A literature search of MEDLINE and the internet (2006e2013) using key words such as paediatric radiation therapy imaging dose, imaging guidelines, ALARA principle (As Low as Reasonably Achievable) and imaging dose reduction in radiation therapy indicated little published literature on the subject. The two types of imaging used in radiation therapy are CT simulation and treatment position verification imaging. It is unknown if established diagnostic CT guidelines4 for children are being used for CT simulation of children. Kilovoltage (kV) imaging modalities such as planar imaging and cone beam computed tomography (CBCT) are quickly replacing electronic portal imaging (EPI) for most treatment setup verification imaging with some identified articles outlining dose reduction strategies for CBCT imaging.13e15 With respect to kV planar imaging, it is not clear from the literature if dose reduction guidelines for computed radiography (CR) and digital radiography (DR)4 are being applied in radiation therapy. The Children’s Oncology Group (COG) includes children’s hospitals in the United States, Canada, Europe, Australia and New Zealand. A survey of COG institutions was used to develop radiation therapy treatment imaging guidelines for children12 in 2007, but much of the information is now out-of-date because EPI and port films are no longer the main imaging modalities. With respect to treatment set up verification imaging, there is often a general sense within the radiation therapy community that the dose received from imaging is very small in comparison to the treatment dose and therefore not significant.8,9,12 Imaging dose reduction initiatives are important for paediatric cancer patients as the current survival rate for childhood cancer is approximately 80% in Canada and the United States16,17 and 75% in Europe.18 With children living longer after a diagnosis of cancer, there is more time for a radiation induced neoplasm, or other radiation induced effects, to develop.2,9 With this in mind, a survey of paediatric imaging practice in Canadian cancer clinics was undertaken to investigate whether paediatric radiation protection initiatives in diagnostic imaging have been integrated into radiation therapy paediatric imaging. In addition the survey also assessed therapy radiographer knowledge of paediatric imaging. Methods A questionnaire was developed to explore paediatric radiotherapy imaging practice across Canada. An invitation to complete the online questionnaire (Appendix 1) was sent to 39 of the 44 radiation therapy clinics in Canada via e-mail. Five
clinics within the French-speaking province of Quebec were excluded from the sample as the survey was available only in English. The survey was peer reviewed (piloted) by three colleagues including a paediatric Radiation Oncologist and a radiation therapy educator with research experience. Questions were modified based on feedback. Research Ethics Board approval (H12-03294) was obtained for the study design and data collection from across Canada. The questionnaire was sent to radiation therapy educators working within clinical departments. This group was chosen as an email distribution list exists for this group and this approach facilitated access to most clinics. The educators were asked to forward the survey to the best person in their clinic to complete, or to complete it themselves. The email invitation directed the respondents to the Fluid Survey website,19 an established web based survey tool. Completed surveys were tabulated and stored anonymously on the web-based program. As the responses were anonymous, it was not possible to determine which clinics responded. The data was collected between November 2012 and December 2012 and no follow up reminders were distributed due to time restrictions for project completion. The questionnaire consisted of 14 questions (qualitative and quantitative) regarding imaging of paediatric patients. The survey questions were developed using the Image Gently website for recommended dose reduction methods. Most questions (n ¼ 9/14) were fixed choice, yes or no, questions. Five questions had an option to add additional information or choose more than one option. The first six questions were general questions about paediatric imaging and dose followed by questions related to treatment verification imaging and CT simulation. Results Fifteen responses were received (n ¼ 15/39; 38.5%). As this is the first survey research to consider this aspect of practice in Canada, the response rate was disappointing, but will nonetheless provide a baseline upon which future studies can build. General questions All centres reported treating low numbers of paediatric patients annually with most (46.6%, n ¼ 7/15) reporting treating less than 10 children per year. Three clinics treated 10-20 children per year whilst four clinics treated between 20 and 40 children. Only 1 clinic reported treating more than 50 children per year. When asked to rate their knowledge of paediatric imaging, the majority of respondents (40%, n ¼ 6/15) felt knowledgeable or had some knowledge (40%, n ¼ 6/15), while three respondents felt they had no paediatric imaging knowledge (20%, n ¼ 3/15). Interestingly, responses appeared to be associated with volume of paediatric patients treated as the majority of respondents from clinics treating more than 20 children per year (n ¼ 4/5) reported feeling knowledgeable about paediatric imaging, whereas only two respondents from clinics treating les than 20 children per year felt knowledgeable (20%, n ¼ 2/10). When asked if they were aware of the Image Gently campaign, 73.3% (n ¼ 11/15) of respondents reported they were aware. Of the five clinics that reported treating more than 20 children per year, four respondents (80%) were aware of the Image Gently campaign. Survey responses indicate 33.3% (n ¼ 5/15) of clinics have a paediatric team in radiation therapy. It is unknown if these teams are multidisciplinary or the role of a therapy radiographer within
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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them. Teams existed in four of the five clinics that treated more than 20 paediatric patients annually. With respect to dose reduction in imaging associated with radiation therapy, the majority of respondents (86.7%, n ¼ 13/ 15) felt there was value in reducing imaging dose to children. In contrast, when asked if imaging dose could be reduced at their centre, nearly half of the clinics (n ¼ 7/15) felt this was not possible. Once again, responses appeared to be associated with volume of paediatric patients treated with all response from the five clinics who treat more than 20 children per year reporting that imaging dose could be reduced at their centre. Figure 2. Treatment verification imaging frequency.
Treatment verification imaging Concerning the primary treatment imaging modality used, most clinics reported using kV planar imaging, followed by CBCT and EPI’s (Fig. 1). Four clinics used a combination of imaging modalities, including two clinics that treated more than 20 children per year. Of the five clinics that treated the most children, two clinics use CBCT as a primary imaging modality, including the clinic that treated more than 50 children per year, and four clinics used kV planar imaging. With respect to imaging frequency, daily imaging was most commonly undertaken followed by imaging on day one only (Fig. 2). No clinic reported taking post treatment images and twenty percent (n ¼ 3/15) of clinics reported using a combination of imaging frequencies. Of the clinics that treated more than 20 children per year, four used daily imaging and one used first day imaging only. Interestingly, the clinic that reported treating the greatest number of paediatric patients reported that it verified moves based on initial imaging, with repeated imaging after the moves were made, except when using CBCT. No explanation was given as to why CBCT moves did not also need to be verified. When asked if paediatric specific protocols are used for treatment verification imaging, only three clinics (n ¼ 3/15), all of which treated more than 20 children annually, reported using specific protocols. Of these, only 2 indicated that the incorporated ways to reduce imaging dose. When asked if verification imaging dose is too minimal to be concerned with when the treatment target is receiving a much higher radiation dose, approximately one third (33.3%, n ¼ 5/15) responded that the imaging dose was too small to worry about. This included two clinics that treat greater than 20 children per year.
Figure 1. Primary imaging modality used for treatment set up verification.
Clinics reported using the following methods to reduce dose when performing verification imaging: coning down the imaging field (20%, n ¼ 3/15), manually lowering the settings (13.3%, n ¼ 2/ 15), using ‘small’ pre-programmed settings on the kV planar imager (13.3%, n ¼ 2/15). One third (33.3%, n ¼ 5/15) of responses indicated no adjustments were made to reduce dose. No respondent reported reducing imaging dose by reducing the amount of images taken. Of the five clinics that reported using no adjustments for verification imaging, two were clinics that treated more than 20 children per year. CT simulation Less than half (40%, n ¼ 6/15) of the respondents reported having paediatric specific CT simulation protocols. Methods reported by clinics to reduce CT simulation dose include using shorter length scans, using paediatric specific settings and trying to reduce the possibility of rescan by having all relevant information before scanning. One clinic reported using manually lowered settings and one clinic reported using no methods to reduce CT scan dose. No other methods to reduce CT dose from simulation were identified. Discussion This survey of paediatric radiation therapy imaging practice across Canada may be criticized for the small sample size and response rate; however the findings remain valuable and demonstrate significant variation in practice between clinics. The WPIF, FDA, IAEA and the International Commission on Radiological Protection (ICRP)3,5,6,20 have expressed a need to minimize imaging dose to children. The results of this survey suggest that imaging practice in radiotherapy centres may not always reflect this directive. In some radiotherapy centres, children may be imaged using adult techniques, a finding also noted to occur in diagnostic imaging settings.21 Kaste21 suggests that the inappropriate use of radiation in paediatric medical imaging results from naiveté, misinformation, resource availability, staffing, scheduling, and limited evidence base for imaging practice. The Image Gently campaign has dose reduction guidelines for diagnostic CT procedures4 which also could be applied to CT simulation examinations within radiation therapy. However, less than half of the respondents indicated that paediatric CT protocols were in operation. Importantly, while CT examinations account for only 13% of radiological procedures, CT accounts for 70% of the imaging dose patients receive.2,4 A recent study has demonstrated increased cancer incidence in children who have
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had a previous CT scan11 as a result of a doseeresponse relationship. This emphasizes the importance of radiation protection for CT examinations, especially for children for whom sensitivity to radiation is greater due to growth and anatomical factors. Paediatric CT imaging dose can be reduced2,4 by using size adjusted kV and mA, performing a single scan, scanning only the required area and staff education. There are suggestions in the literature for manufacturers to share responsibility for reducing paediatric dose4,5,23 through the provision of tools to allow for child appropriate scan parameters. As shown from the survey results, some of these measures are currently being employed within Canadian clinics. Treatment set up verification imaging in radiation therapy has evolved quickly. This is evident in the COG portal imaging guidelines from 2007 which only mention kV planar imaging and CBCT briefly.12 IGRT often involves frequent imaging of the patient throughout treatment. The AAPM task group 75 states that imaging exposure should be carefully managed8 and this can be a complex process as illustrated in the task force’s recommendations. In addition to increased imaging demands, certain treatment techniques, such as IMRT or VMAT, expose larger volumes of uninvolved tissues to low levels of radiation through head leakage from the machine.9,24 This low dose radiation to normal tissues is associated with secondary carcinogenesis, sometimes with greater incidence than seen with conventional radiation therapy.24 Best treatment verification imaging practice for paediatric patients9,13,14 is yet to be determined. The rapid advancement in technologies has not been met with equally rapid changes in technology application and practice evolution.21 As a result; a delay between technological capability and evidence based practice exists. Many clinics in Canada (80%, n ¼ 12/15) do not have paediatric protocols for treatment verification imaging and one third (33.3%, n ¼ 5/15) of radiation therapy clinics in Canada make no adjustments to image settings. The survey found approximately one quarter of clinics use CBCT for paediatric patients. Dose reduction with CBCT warrants further discussion as CBCT of children can result in two to three times the dose to critical structures13 in comparison to adults. CBCT can also result in two to four times the dose to bone compared to soft tissue14 in children. Two of the five clinics that treat greater than 20 children per year reported using CBCT as a primary treatment verification imaging modality. There is discord in the use of CBCT in children and the effects of the CBCT which requires further examination and clarification. Potential dose reduction methods for CBCT include using a copper filter,15 changing exposure settings,13,15 increasing the distance of the scan border from organs at risk (OAR’s),13 using testicular shielding,13 and choosing an appropriate scanning protocol.13 However, not all of these options are available on linear accelerators. It is unknown from this survey if clinics in Canada use methods to reduce CBCT dose when imaging children. Electronic portal imaging (EPI’s) can be necessary for certain treatment techniques to see shielding of critical structures, or the treatment field itself. For EPI’s of children, guidelines exist12 and include using a single exposure, minimizing the field size, using the minimum number of monitor units possible to get a readable image, accumulating monitor units, and acquiring field ports during treatment. Kilovoltage planar imaging for treatment verification is the most commonly used imaging modality for paediatric patients. Review of the literature, found no articles in relation to modifying radiation therapy imaging dose using kV planar imaging. Willis and Slovis (2004) in their article on ALARA in Computed Radiography (CR) and
Digital Radiography (DR) offer suggestions for dose reduction22 such as using a team approach to dose management, dose feedback, training of staff in use of equipment, and standardization of protocols. International Commission on Radiological Protection (ICRP) 121 contains paediatric dose reduction information for kV imaging.20 The Image Gently website ‘back to basics’ and ICRP 121 guidelines include2,20 ‘child sizing’ procedure settings, imaging only when necessary, shielding patients when possible, and coning down imaging fields. Over-exposure in CR and DR can be common22 as a connection is lost between the image displayed, and the settings used to take images. This is true in radiation therapy as well. Therapy radiographers can improve a verification image by adjusting the window/level, and need not be as concerned with adjusting exposure settings. Linear accelerator manufacturers have not addressed the need for smaller kV and mAs for paediatric patients. The questionnaire identifies that approximately one third of clinics have paediatric teams supporting paediatric practice in radiation therapy departments. Kufe10 et al. (2003) argues that unique skills and resources are required for treating children, and that paediatric radiotherapy should be ideally given at a center with experience of treating children.10 Kaste (2009) states that ‘Collaboration with other health care providers, technologists, vendors, patients and others is the key to successfully establishing ALARA principles for all medical imaging.’21 The survey findings do not indicate whether the paediatric teams are multidisciplinary or how they specifically impact on practice. As with most research, limitations to the study are acknowledged. Specifically, some of the questions may have been considered ‘leading’ in their phrasing, some questions had more than one answer that could be chosen which could cause ambiguity, and the responses may not have captured all imaging practices, particularly given the low response rate and sample size. Nevertheless, the findings of this study provide baseline data on paediatric imaging dose reduction strategies within radiation therapy departments across Canada, and the wide variation in practice that exists. Further, the study supports the need for education, standardization and further work to prioritize the needs of this vulnerable group. This could be achieved through establishing multidisciplinary teams to set standards and engage in further research.
Conclusion Variations of practice and knowledge in paediatric radiotherapy imaging were identified across Canada. The WPIF, FDA, IAEA, and the ICRP3,5,6,20 strongly promote the reduction of imaging dose to paediatric patients. It is no longer reasonable to assume imaging doses in radiation therapy are negligible to children. With respect to IGRT, the AAPM conveys we cannot assume the imaging dose is negligible in comparison to the treatment dose.8 Therapy radiographers must take a lead in developing international paediatric imaging dose reduction strategies, and establishing standards of best practice in radiation therapy. While the findings of this study pertain solely to Canada, there is currently no evidence to suggest that practice and knowledge within the radiation therapy setting would be different in other countries.
Conflict of interest statement The author has no conflicts of interest.
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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Appendix 1
Questionnaire sent to Canadian clinics on pediatric imaging in RT General Questions 1. Approximately how many pediatric patients do you treat in your centre per year? a) 0-20 b) 21-40 c) 41-60 d) more than 50 2. How would you rate your knowledge of pediatric imaging and how it is different from adult imaging in Radiation Therapy? a) none b) some c) knowledgeable 3. Do you have a pediatric RT team at your centre? a) yes b) no c) working on creating a team 4. Are you aware of the Image Gently campaign initiative? a) yes b) no 5. Do you think there is value in reducing dose to pediatric radiation therapy patients? a) yes b) no 6. Do you feel pediatric imaging dose could be reduced at your centre? a) yes b) no Treatment Imaging Questions 7. What is the primary imaging modality used for position verification in your clinic for pediatric patients? Pick all relevant answers. a) kV b) Portal imaging (MV) c) CBCT d) combination (specify) 8. What is the frequency of verification imaging for pediatric patient at your centre? a) first day b) first 3 days c) weekly d) daily e) pre and post treatment f) other (specify) 9. Do you have specific pediatric treatment verification imaging protocols (as opposed to site protocols generally used for adults)? a) yes b) no 10. If you have a pediatric imaging protocol, does it emphasize reducing dose to pediatric patients? a) yes b) no 11. If you do use measures to reduce pediatric verification imaging dose, what measures do you take to reduce dose to pediatric patients from verification imaging (choose all appropriate)? a) cone down field b) limit frequency of imaging c) use lower settings for kV images d) use kV imaging instead of MV e) other… specify 12. Do you believe the dose from verification imaging is too minimal to worry about considering we are treating the treatment site to a high dose? a) yes b) no
CT Simulation Questions 13. For CT simulation of pediatric patients, does your clinic have specific protocols for scanning pediatric patients? a) yes b) no 14. If you do have pediatric specific protocols for CT simulation, what methods are used to reduce pediatric radiation exposure during CT? a) shorter scan lengths b) lower setting are used c) specific pediatric CT settings d) specific pediatric settings as per the Image Gently campaign e) no specific measures f) prevent rescan for patients by being as informed and prepared as possible. h) other (please specify)
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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References 1. ICRP. 1990 recommendations of the International Commission on Radiological Protection. ICRP publication 60 Ann ICRP 1991;21(1e3). 2. Voress M. The increasing use of CT and it’s risks. Radiol Technol 2007;79(2): 186e90. 3. World pediatric imaging federation launch. http://www.espr.org/index.php? option¼com_content&view¼article&id¼201:wfpi-launch&catid¼129:wfpicategory [accessed April 2013]. 4. Image Gently website: http://www.pedrad.org/associations/5364/ig/ [accessed from Dec 2012eMay 2013]. 5. International Atomic Energy Agency website: https://rpop.iaea.org/RPOP/RPoP/ Content/AdditionalResources/Training/1_TrainingMaterial/ PaediatricRadiology.htm [accessed April 2013]. 6. Federal Drug Administration. Radiation emitting products e pediatric X-ray imaging. http://www.fda.gov/Radiation%20EmittingProducts/RadiationEmitt ingProductsandProcedures/MedicalImaging/ucm298899.htm [accessed April 3013]. 7. Willis D, Tongs D. Imaging ‘Gently’ in paediatric image guided radiation therapy. Imaging Oncol 2012; 64e66. Available from: http://www.sor.org/learning/ library-publications/imaging-oncology [accessed April 2013]. 8. Murphy M, Balter J, Balter S, BenComo Jr JA, Das IJ, Jiang SB, et al. The management of imaging dose during image-guided radiotherapy. Report of the AAPM Task Group 75 Med Phys 2007;34(10):4041e63. 9. Kun LE, Beltran C. Radiation therapy for children: evolving technologies in the era of ALARA. Pediatr Radiol 2009;Feb(39 Supp1.):S65e70. 10. Kufe DW, Pollock RE, Weichselbaum RR, Bast RC, Gansler TS, Holland JF, et al., editors. Holland Frei cancer medicine. 6th ed. Hamilton (On): BC Decker; 2003. Section 37. Available from: http://www.ncbi.nlm.nih.gov/books/NBK20844/ [accessed April 2013]. 11. Mathews JD, Forsythe AV, Brady Z, Butler MW, Goergen SK, Byrnes GB, et al. Caner risk in 680 000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians. BMJ 2013;346:f2360.
12. Olich AJ, Gueurts M, Thomadsen B, Famiglietti R, Chang EL. Portal imaging practice patterns of children’s oncology group institutions: dosimetric assessment and recommendations for minimizing unnecessary exposure. Int J Radiat Oncol Biol Phys 2007;67(2):594e600. 13. Deng J, Chen Z, Roberts KB, Nath R. Kilovoltage imaging doses in the radiotherapy of paediatric cancer patients. Int J Radiat Oncol Biol Phys 2012;82(5#): 1680e8. 14. Ding GX, Coffey CW. Radiation dose from kilovoltage cone beam computed tomography in an image-guided radiotherapy procedure. Int J Radiat Oncol Biol Phys 2009;73(2):610e7. 15. Roxby P, Kron T, Foroudi F, Haworth A, Fox C, Mullen A, et al. Simple methods to reduce patient dose in a Varian cone beam CT system for delivery verification in pelvis radiotherapy. Br J Radiol 2009;82:855e9. 16. Pediatric cancer survival rates in the United States. http://www.cancer.gov/ cancertopics/factsheet/Sites-Types/childhood [accessed April 15, 2013]. 17. Childhood cancer survivor rates in Canada. http://www.phac-aspc.gc.ca/cd-mc/ cancer/fs-fi/cancer-child-enfant/ [accessed April 14, 2013]. 18. Gatta G, Capocaccia R, Stiller C, Kaastsch P, Berrino F, Terenziani M, the EUROCARE Working Group. Childhood cancer survival trends in Europe: a EUROCARE Working Group study. J Clin Oncol 2005; June 1;23(16):3742e51. 19. http://fluidsurveys.com/ [accessed from Dec 2012eMay 2013]. 20. ICRP. Radiological protection in paediatric diagnostic and interventional radiology. ICRP Publication 121 Ann ICRP 2013;42(2). 21. Kaste SC. Imaging challenges: a US perspective on controlling exposure to ionizing radiation in children with cancer. Pediatr Radiol 2009;39(Suppl. 1): S74e9. 22. Willis CE, Slovis TL. The ALARA concept in pediatric CR and DR: dose reduction in pediatric exams e a white conference executive summary. Pediatr Radiol 2004;34(Suppl. 3):S162e4. 23. Slovis TL. The ALARA concept in pediatric CT: myth or reality. Radiography 2002;223:5e6. 24. Cashmore J, Ramthhul M, Ford D. Lowering whole body radiation dose in pediatric intensity modulated radiotherapy through the use of unflattened photon beams. Int J Radiat Oncol Biol Phys 2011;80(4):1220e7.
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
Contents lists available at ScienceDirect
Radiography journal homepage: www.elsevier.com/locate/radi
ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice Christine Rodgerson* British Columbia Cancer Agency, 600 W 10 Ave, Vancouver V5Z 4E6, Canada
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 May 2013 Received in revised form 9 November 2013 Accepted 14 November 2013 Available online xxx
Purpose: There is little discussion in the literature regarding paediatric imaging dose reduction with respect to conventional imaging carried out in radiotherapy departments. This is in contrast to diagnostic radiography where dose optimization when imaging children is a very current topic. For this reason Canadian radiotherapy clinics were surveyed to look at paediatric imaging practice, knowledge and perspectives with respect to imaging dose reduction. Method: As this was an exploratory study, a questionnaire was developed and sent to radiation therapy clinics across Canada, via email, to assess knowledge of paediatric imaging and dose reduction initiatives. The questionnaire focus was CT simulation and treatment verification imaging of children. Results: Practice and knowledge of paediatric imaging varied across Canada. Forty percent of clinics reported using paediatric specific protocols for CT simulation and 20% of clinics reported using paediatric specific protocols for treatment verification imaging. There was variation in imaging practices among the clinics that reported treating the most children. The survey results show that while some measures are being taken to reduce paediatric imaging dose in radiation therapy, 46.7% of the respondents felt more could be done. Conclusion: The survey demonstrates interest in dose reduction in radiation therapy imaging as well as differences in current practice and knowledge across Canada. Paediatric imaging dose reduction would appear to be an area of practice that would benefit from more study and development of standards of practice. Ó 2013 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.
Keywords: Imaging dose reduction Paediatric radiation therapy ALARA Paediatric imaging guidelines
Introduction Reducing imaging dose in paediatric patients is important as children are up to ten times more sensitive to radiation induced toxicities than adults1 and are susceptible to a larger anatomical area being irradiated due to their small size.2 This has led to a worldwide effort to reduce radiation dose to paediatric patients from diagnostic imaging supported by the World Pediatric Imaging Federation (WPIF),3 the Image Gently (IG) campaign,4 the International Atomic Energy Agency (IAEA),5 and the Food and Drug Administration (FDA) in the United States.6 The Image Gently campaign started in 2007 with the goal to change diagnostic
* Tel.: þ1 604 877 6000x672723 (work); fax: þ1 604 877 6039. E-mail address: [email protected].
imaging practice by increasing awareness of the opportunities to lower dose when imaging children. The IAEA suggests that children are a special case in terms of standards and guidelines for radiation protection5 and according to the FDA, the “increased radio sensitivity of paediatric patients compared to adults makes it important to adjust equipment settings to optimize radiation exposure to paediatric patients for all types of X-ray imaging exams.”6 In addition to an increase in diagnostic imaging procedures over the past decade, there has been an increase in imaging procedures related to radiotherapy planning and treatment. Radiation treatment planning can involve patients undergoing multiple computed tomography (CT) scans. Intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) treatments are now commonly available and often require image guided radiation therapy (IGRT) to ensure the patient is in the correct position for these precise treatments.7e9
1078-8174/$ e see front matter Ó 2013 The College of Radiographers. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.radi.2013.11.003
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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IMRT and VMAT treatment techniques, along with increased treatment verification imaging, can lead to increased amounts of normal tissue receiving low dose radiation.8,9 Paradoxically, new treatment techniques such as IMRT and VMAT can lead to greater protection of normal tissue from the effects of radiotherapy with a resulting decrease in both acute and chronic side effects of radiation treatment.7 The American Association of Physicists in Medicine (AAPM) tasked a group to look at ways to mange imaging dose from IGRT.8 In 2007 this group concluded that imaging doses are not negligible8 and for IGRT, a balance of risks versus benefits must be determined.6e8 Children comprise a very small fraction of patients treated in radiation therapy departments with some departments rarely, if ever, treating paediatric patients. With such small patient numbers, it can be difficult to create expertise in paediatric imaging. Children can have a number of different treatment requirements in comparison to adult patients such as awareness of late effects, the possible need for anaesthesia during treatment, and a need to customize procedures for children.10 A literature search of MEDLINE and the internet (2006e2013) using key words such as paediatric radiation therapy imaging dose, imaging guidelines, ALARA principle (As Low as Reasonably Achievable) and imaging dose reduction in radiation therapy indicated little published literature on the subject. The two types of imaging used in radiation therapy are CT simulation and treatment position verification imaging. It is unknown if established diagnostic CT guidelines4 for children are being used for CT simulation of children. Kilovoltage (kV) imaging modalities such as planar imaging and cone beam computed tomography (CBCT) are quickly replacing electronic portal imaging (EPI) for most treatment setup verification imaging with some identified articles outlining dose reduction strategies for CBCT imaging.13e15 With respect to kV planar imaging, it is not clear from the literature if dose reduction guidelines for computed radiography (CR) and digital radiography (DR)4 are being applied in radiation therapy. The Children’s Oncology Group (COG) includes children’s hospitals in the United States, Canada, Europe, Australia and New Zealand. A survey of COG institutions was used to develop radiation therapy treatment imaging guidelines for children12 in 2007, but much of the information is now out-of-date because EPI and port films are no longer the main imaging modalities. With respect to treatment set up verification imaging, there is often a general sense within the radiation therapy community that the dose received from imaging is very small in comparison to the treatment dose and therefore not significant.8,9,12 Imaging dose reduction initiatives are important for paediatric cancer patients as the current survival rate for childhood cancer is approximately 80% in Canada and the United States16,17 and 75% in Europe.18 With children living longer after a diagnosis of cancer, there is more time for a radiation induced neoplasm, or other radiation induced effects, to develop.2,9 With this in mind, a survey of paediatric imaging practice in Canadian cancer clinics was undertaken to investigate whether paediatric radiation protection initiatives in diagnostic imaging have been integrated into radiation therapy paediatric imaging. In addition the survey also assessed therapy radiographer knowledge of paediatric imaging. Methods A questionnaire was developed to explore paediatric radiotherapy imaging practice across Canada. An invitation to complete the online questionnaire (Appendix 1) was sent to 39 of the 44 radiation therapy clinics in Canada via e-mail. Five
clinics within the French-speaking province of Quebec were excluded from the sample as the survey was available only in English. The survey was peer reviewed (piloted) by three colleagues including a paediatric Radiation Oncologist and a radiation therapy educator with research experience. Questions were modified based on feedback. Research Ethics Board approval (H12-03294) was obtained for the study design and data collection from across Canada. The questionnaire was sent to radiation therapy educators working within clinical departments. This group was chosen as an email distribution list exists for this group and this approach facilitated access to most clinics. The educators were asked to forward the survey to the best person in their clinic to complete, or to complete it themselves. The email invitation directed the respondents to the Fluid Survey website,19 an established web based survey tool. Completed surveys were tabulated and stored anonymously on the web-based program. As the responses were anonymous, it was not possible to determine which clinics responded. The data was collected between November 2012 and December 2012 and no follow up reminders were distributed due to time restrictions for project completion. The questionnaire consisted of 14 questions (qualitative and quantitative) regarding imaging of paediatric patients. The survey questions were developed using the Image Gently website for recommended dose reduction methods. Most questions (n ¼ 9/14) were fixed choice, yes or no, questions. Five questions had an option to add additional information or choose more than one option. The first six questions were general questions about paediatric imaging and dose followed by questions related to treatment verification imaging and CT simulation. Results Fifteen responses were received (n ¼ 15/39; 38.5%). As this is the first survey research to consider this aspect of practice in Canada, the response rate was disappointing, but will nonetheless provide a baseline upon which future studies can build. General questions All centres reported treating low numbers of paediatric patients annually with most (46.6%, n ¼ 7/15) reporting treating less than 10 children per year. Three clinics treated 10-20 children per year whilst four clinics treated between 20 and 40 children. Only 1 clinic reported treating more than 50 children per year. When asked to rate their knowledge of paediatric imaging, the majority of respondents (40%, n ¼ 6/15) felt knowledgeable or had some knowledge (40%, n ¼ 6/15), while three respondents felt they had no paediatric imaging knowledge (20%, n ¼ 3/15). Interestingly, responses appeared to be associated with volume of paediatric patients treated as the majority of respondents from clinics treating more than 20 children per year (n ¼ 4/5) reported feeling knowledgeable about paediatric imaging, whereas only two respondents from clinics treating les than 20 children per year felt knowledgeable (20%, n ¼ 2/10). When asked if they were aware of the Image Gently campaign, 73.3% (n ¼ 11/15) of respondents reported they were aware. Of the five clinics that reported treating more than 20 children per year, four respondents (80%) were aware of the Image Gently campaign. Survey responses indicate 33.3% (n ¼ 5/15) of clinics have a paediatric team in radiation therapy. It is unknown if these teams are multidisciplinary or the role of a therapy radiographer within
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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them. Teams existed in four of the five clinics that treated more than 20 paediatric patients annually. With respect to dose reduction in imaging associated with radiation therapy, the majority of respondents (86.7%, n ¼ 13/ 15) felt there was value in reducing imaging dose to children. In contrast, when asked if imaging dose could be reduced at their centre, nearly half of the clinics (n ¼ 7/15) felt this was not possible. Once again, responses appeared to be associated with volume of paediatric patients treated with all response from the five clinics who treat more than 20 children per year reporting that imaging dose could be reduced at their centre. Figure 2. Treatment verification imaging frequency.
Treatment verification imaging Concerning the primary treatment imaging modality used, most clinics reported using kV planar imaging, followed by CBCT and EPI’s (Fig. 1). Four clinics used a combination of imaging modalities, including two clinics that treated more than 20 children per year. Of the five clinics that treated the most children, two clinics use CBCT as a primary imaging modality, including the clinic that treated more than 50 children per year, and four clinics used kV planar imaging. With respect to imaging frequency, daily imaging was most commonly undertaken followed by imaging on day one only (Fig. 2). No clinic reported taking post treatment images and twenty percent (n ¼ 3/15) of clinics reported using a combination of imaging frequencies. Of the clinics that treated more than 20 children per year, four used daily imaging and one used first day imaging only. Interestingly, the clinic that reported treating the greatest number of paediatric patients reported that it verified moves based on initial imaging, with repeated imaging after the moves were made, except when using CBCT. No explanation was given as to why CBCT moves did not also need to be verified. When asked if paediatric specific protocols are used for treatment verification imaging, only three clinics (n ¼ 3/15), all of which treated more than 20 children annually, reported using specific protocols. Of these, only 2 indicated that the incorporated ways to reduce imaging dose. When asked if verification imaging dose is too minimal to be concerned with when the treatment target is receiving a much higher radiation dose, approximately one third (33.3%, n ¼ 5/15) responded that the imaging dose was too small to worry about. This included two clinics that treat greater than 20 children per year.
Figure 1. Primary imaging modality used for treatment set up verification.
Clinics reported using the following methods to reduce dose when performing verification imaging: coning down the imaging field (20%, n ¼ 3/15), manually lowering the settings (13.3%, n ¼ 2/ 15), using ‘small’ pre-programmed settings on the kV planar imager (13.3%, n ¼ 2/15). One third (33.3%, n ¼ 5/15) of responses indicated no adjustments were made to reduce dose. No respondent reported reducing imaging dose by reducing the amount of images taken. Of the five clinics that reported using no adjustments for verification imaging, two were clinics that treated more than 20 children per year. CT simulation Less than half (40%, n ¼ 6/15) of the respondents reported having paediatric specific CT simulation protocols. Methods reported by clinics to reduce CT simulation dose include using shorter length scans, using paediatric specific settings and trying to reduce the possibility of rescan by having all relevant information before scanning. One clinic reported using manually lowered settings and one clinic reported using no methods to reduce CT scan dose. No other methods to reduce CT dose from simulation were identified. Discussion This survey of paediatric radiation therapy imaging practice across Canada may be criticized for the small sample size and response rate; however the findings remain valuable and demonstrate significant variation in practice between clinics. The WPIF, FDA, IAEA and the International Commission on Radiological Protection (ICRP)3,5,6,20 have expressed a need to minimize imaging dose to children. The results of this survey suggest that imaging practice in radiotherapy centres may not always reflect this directive. In some radiotherapy centres, children may be imaged using adult techniques, a finding also noted to occur in diagnostic imaging settings.21 Kaste21 suggests that the inappropriate use of radiation in paediatric medical imaging results from naiveté, misinformation, resource availability, staffing, scheduling, and limited evidence base for imaging practice. The Image Gently campaign has dose reduction guidelines for diagnostic CT procedures4 which also could be applied to CT simulation examinations within radiation therapy. However, less than half of the respondents indicated that paediatric CT protocols were in operation. Importantly, while CT examinations account for only 13% of radiological procedures, CT accounts for 70% of the imaging dose patients receive.2,4 A recent study has demonstrated increased cancer incidence in children who have
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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had a previous CT scan11 as a result of a doseeresponse relationship. This emphasizes the importance of radiation protection for CT examinations, especially for children for whom sensitivity to radiation is greater due to growth and anatomical factors. Paediatric CT imaging dose can be reduced2,4 by using size adjusted kV and mA, performing a single scan, scanning only the required area and staff education. There are suggestions in the literature for manufacturers to share responsibility for reducing paediatric dose4,5,23 through the provision of tools to allow for child appropriate scan parameters. As shown from the survey results, some of these measures are currently being employed within Canadian clinics. Treatment set up verification imaging in radiation therapy has evolved quickly. This is evident in the COG portal imaging guidelines from 2007 which only mention kV planar imaging and CBCT briefly.12 IGRT often involves frequent imaging of the patient throughout treatment. The AAPM task group 75 states that imaging exposure should be carefully managed8 and this can be a complex process as illustrated in the task force’s recommendations. In addition to increased imaging demands, certain treatment techniques, such as IMRT or VMAT, expose larger volumes of uninvolved tissues to low levels of radiation through head leakage from the machine.9,24 This low dose radiation to normal tissues is associated with secondary carcinogenesis, sometimes with greater incidence than seen with conventional radiation therapy.24 Best treatment verification imaging practice for paediatric patients9,13,14 is yet to be determined. The rapid advancement in technologies has not been met with equally rapid changes in technology application and practice evolution.21 As a result; a delay between technological capability and evidence based practice exists. Many clinics in Canada (80%, n ¼ 12/15) do not have paediatric protocols for treatment verification imaging and one third (33.3%, n ¼ 5/15) of radiation therapy clinics in Canada make no adjustments to image settings. The survey found approximately one quarter of clinics use CBCT for paediatric patients. Dose reduction with CBCT warrants further discussion as CBCT of children can result in two to three times the dose to critical structures13 in comparison to adults. CBCT can also result in two to four times the dose to bone compared to soft tissue14 in children. Two of the five clinics that treat greater than 20 children per year reported using CBCT as a primary treatment verification imaging modality. There is discord in the use of CBCT in children and the effects of the CBCT which requires further examination and clarification. Potential dose reduction methods for CBCT include using a copper filter,15 changing exposure settings,13,15 increasing the distance of the scan border from organs at risk (OAR’s),13 using testicular shielding,13 and choosing an appropriate scanning protocol.13 However, not all of these options are available on linear accelerators. It is unknown from this survey if clinics in Canada use methods to reduce CBCT dose when imaging children. Electronic portal imaging (EPI’s) can be necessary for certain treatment techniques to see shielding of critical structures, or the treatment field itself. For EPI’s of children, guidelines exist12 and include using a single exposure, minimizing the field size, using the minimum number of monitor units possible to get a readable image, accumulating monitor units, and acquiring field ports during treatment. Kilovoltage planar imaging for treatment verification is the most commonly used imaging modality for paediatric patients. Review of the literature, found no articles in relation to modifying radiation therapy imaging dose using kV planar imaging. Willis and Slovis (2004) in their article on ALARA in Computed Radiography (CR) and
Digital Radiography (DR) offer suggestions for dose reduction22 such as using a team approach to dose management, dose feedback, training of staff in use of equipment, and standardization of protocols. International Commission on Radiological Protection (ICRP) 121 contains paediatric dose reduction information for kV imaging.20 The Image Gently website ‘back to basics’ and ICRP 121 guidelines include2,20 ‘child sizing’ procedure settings, imaging only when necessary, shielding patients when possible, and coning down imaging fields. Over-exposure in CR and DR can be common22 as a connection is lost between the image displayed, and the settings used to take images. This is true in radiation therapy as well. Therapy radiographers can improve a verification image by adjusting the window/level, and need not be as concerned with adjusting exposure settings. Linear accelerator manufacturers have not addressed the need for smaller kV and mAs for paediatric patients. The questionnaire identifies that approximately one third of clinics have paediatric teams supporting paediatric practice in radiation therapy departments. Kufe10 et al. (2003) argues that unique skills and resources are required for treating children, and that paediatric radiotherapy should be ideally given at a center with experience of treating children.10 Kaste (2009) states that ‘Collaboration with other health care providers, technologists, vendors, patients and others is the key to successfully establishing ALARA principles for all medical imaging.’21 The survey findings do not indicate whether the paediatric teams are multidisciplinary or how they specifically impact on practice. As with most research, limitations to the study are acknowledged. Specifically, some of the questions may have been considered ‘leading’ in their phrasing, some questions had more than one answer that could be chosen which could cause ambiguity, and the responses may not have captured all imaging practices, particularly given the low response rate and sample size. Nevertheless, the findings of this study provide baseline data on paediatric imaging dose reduction strategies within radiation therapy departments across Canada, and the wide variation in practice that exists. Further, the study supports the need for education, standardization and further work to prioritize the needs of this vulnerable group. This could be achieved through establishing multidisciplinary teams to set standards and engage in further research.
Conclusion Variations of practice and knowledge in paediatric radiotherapy imaging were identified across Canada. The WPIF, FDA, IAEA, and the ICRP3,5,6,20 strongly promote the reduction of imaging dose to paediatric patients. It is no longer reasonable to assume imaging doses in radiation therapy are negligible to children. With respect to IGRT, the AAPM conveys we cannot assume the imaging dose is negligible in comparison to the treatment dose.8 Therapy radiographers must take a lead in developing international paediatric imaging dose reduction strategies, and establishing standards of best practice in radiation therapy. While the findings of this study pertain solely to Canada, there is currently no evidence to suggest that practice and knowledge within the radiation therapy setting would be different in other countries.
Conflict of interest statement The author has no conflicts of interest.
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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Appendix 1
Questionnaire sent to Canadian clinics on pediatric imaging in RT General Questions 1. Approximately how many pediatric patients do you treat in your centre per year? a) 0-20 b) 21-40 c) 41-60 d) more than 50 2. How would you rate your knowledge of pediatric imaging and how it is different from adult imaging in Radiation Therapy? a) none b) some c) knowledgeable 3. Do you have a pediatric RT team at your centre? a) yes b) no c) working on creating a team 4. Are you aware of the Image Gently campaign initiative? a) yes b) no 5. Do you think there is value in reducing dose to pediatric radiation therapy patients? a) yes b) no 6. Do you feel pediatric imaging dose could be reduced at your centre? a) yes b) no Treatment Imaging Questions 7. What is the primary imaging modality used for position verification in your clinic for pediatric patients? Pick all relevant answers. a) kV b) Portal imaging (MV) c) CBCT d) combination (specify) 8. What is the frequency of verification imaging for pediatric patient at your centre? a) first day b) first 3 days c) weekly d) daily e) pre and post treatment f) other (specify) 9. Do you have specific pediatric treatment verification imaging protocols (as opposed to site protocols generally used for adults)? a) yes b) no 10. If you have a pediatric imaging protocol, does it emphasize reducing dose to pediatric patients? a) yes b) no 11. If you do use measures to reduce pediatric verification imaging dose, what measures do you take to reduce dose to pediatric patients from verification imaging (choose all appropriate)? a) cone down field b) limit frequency of imaging c) use lower settings for kV images d) use kV imaging instead of MV e) other… specify 12. Do you believe the dose from verification imaging is too minimal to worry about considering we are treating the treatment site to a high dose? a) yes b) no
CT Simulation Questions 13. For CT simulation of pediatric patients, does your clinic have specific protocols for scanning pediatric patients? a) yes b) no 14. If you do have pediatric specific protocols for CT simulation, what methods are used to reduce pediatric radiation exposure during CT? a) shorter scan lengths b) lower setting are used c) specific pediatric CT settings d) specific pediatric settings as per the Image Gently campaign e) no specific measures f) prevent rescan for patients by being as informed and prepared as possible. h) other (please specify)
Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003
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Please cite this article in press as: Rodgerson C, ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice, Radiography (2013), http://dx.doi.org/10.1016/j.radi.2013.11.003