A Critique of the ALARA Concept for Performing Pediatric Head

Computed Tomography

With the advancement in Computed Tomography (CT) imaging technology and image acquisition is the importance of patient safety, particularly in pediatric imaging. CT has become one of the most popular diagnostic tools used in the clinical environment. In some facilities, CT scans constitute as much as 67% of the patient's annual exposures to ionizing radiation (Furlow, 2012). Physicians and technologists alike must be knowledgeable on how to perform the ALARA principle on their patients in order to deliver the least amount of radiation dose possible while achieving diagnostic quality images.
Image Gently Campaign Image Gently and the Alliance for Radiation Safety in Pediatric Imaging has launched a campaign to increase the awareness of the importance of applying the ALARA principles when imaging pediatric patients with Computed Tomography. The Image Gently web site is a source of valuable information for parents of pediatric patients, physicians, technologists, and radiologists. The web site offers pediatric protocols as well as tracking mechanisms for parents of pediatric patients to keep track of their child's dose from clinical CT examinations. The web site offers educational resources for technologists through on-line presentations for continuing education in pediatric CT scanning describing techniques that technologists can employ to reduce dose to their pediatric patients. An example of one of the presentations is Module 3: The ALARA Concept for Performing Pediatric Head Computed Tomography. The main purpose of this particular presentation is to review some of the common causes or indications for ordering CT head examinations on pediatric patients as well as the measures that technologists and radiologists should take to limit patient dose and still maintain diagnostic quality images with the use of proper patient protocols. The key concepts that this module provides are the importance of employing the lowest possible dose in pediatric scanning while maintaining image quality, obtaining proper patient histories, the importance of parent involvement, references to optimal scan protocols, scan technique and resolution, proper patient positioning and the radiation CT dose index. The presentation does an excellent job of covering the three radiation protection principles of justification, optimization, and dose limitation (Seeram, 2009).
Increased use of Pediatric CT The presentation explains the increased use of CT and the susceptibility of children to the effects of radiation due to the fact that they could inevitably live to experience the latent effects, however; the presentation does not go into the reasons why this is so. According to Furlow (2012, p. 443) “this is part because rapidly growing organisms are undergoing rapid cellular division and their DNA is therefore more frequently uncoiled and more vulnerable to damage. Teratogenesis or distruption of fetal development other than carcinogenesis can occur in embryos as young as 2 weeks of gestation and through 15 weeks resulting in birth defects such as brain abnormalities, retarded body growth, and mental retardation.” The presentation lacks information on the estimated number of CT exams that are performed in the United States. According to Furlow (2012, p. 442) “It has been estimated that 10% of the CT scans performed each year in the United States - at least 6 million - are perfomed on children.” Technologists, physicians, and radiologists have a duty as professionals in the healthcare arena to make every effort to apply all the tools necessary to keep radiation dose as low as reasonably achievable when performing CT scans on all patients, especially pediatric patients.
Indications for Pediatric CT The presentation does an excellent job in listing the indications for ordering head CT scans on pediatric patients such as acute head trauma, neurological disorders, unconsciousness, skull fractures, and follow-up cerebrospinal fluid shunt studies. Listing these indications in the presentation is a good reminder for technologists on the proper reasons or medical indications for ordering CT head examinations. This information can be used as a guide line for the technologist when CT examinations are ordered on pediatric patients in their facilities. If a technologist feels an order for a CT scan on a pediatric patient is questionable, he or she should bring their concern to a radiologist for the final decision on whether or not the exam is justified or if an alternative examination could be performed. Having the patient's best interest in mind will help to eliminate unnecessary CT examinations on all patients. The comparison of dose equivalents from a head CT to background radiation helps to provide the technologist or the parent with a better understanding of the doses associated with a CT examination as well as an understanding of the importance of dose reduction when imaging pediatric patients. The presentation emphasizes the role of the technologist in the reduction of dose to the pediatric patient and reconfirms the responsibility that the technologist has in employing radiation safety. The presentation explains that most often the technologist is the one that decides on the imaging protocols to be used due to the indication of the exam. By including this in the presentation, it puts into perspective the crucial role that the technologist plays in the reduction of dose to pediatric patients by selecting proper scanning protocols to eliminate motion and the use of sedation. Seeram (2009) explains that the principle duties of technologists that perform CT scans are to ensure that the scans are done as safely, quickly, and as accurately as possible. Taking the time to ensure justification of the exam, selection of proper scan parameters for image quality, as well as selecting all available imaging tools to keep radiation dose to a minimum, the technologist will ensure that the ALARA principles of radiation protection are followed for all patients undergoing CT examinations.
Patient Histories The presentation talked about the importance of obtaining proper patient histories, reviewing the patient's medical history through the hospital information system, the patient's medical record, and the patient’s parents. The importance of this practice is emphasized by the statement in the presentation that medical record reports can give pertinent information that could actually alter the CT protocols used. The presentation provides a link to the Image Gently web site for information on pediatric CT scanning which is a valuable resource for technologists, physicians, and parents to gain information on proper scan protocols as well as protocol forms that parents can use to log their child's dose and medical histories for all CT examinations. This form can prove to be a dose reduction tool for parents to present to their child's referring physicians in order to plan the best course of action for their child with the least amount of radiation exposure. The more educated parents are on the effects of radiation dose from CT scanning, the more likely they will be to question their child's physician which could inevitably reduce unnecessary CT exams performed on pediatric patients.
Scan Protocols The presentation talks about using the proper scan protocols based on the tissues or structures that are being evaluated. It explains that higher doses are needed to see soft tissue structures where lower doses could be used when evaluating higher density structures such as shunts or contrast filled structures. A list is provided showing indications for pediatric head scanning that are categorized with an (H) for higher resolution techniques, and an (L) for lower resolution techniques and (3D) for 3Dimensional techniques. The presentation talks about lowering mAs values to decrease patient dose, but doesn't include anything about the effects of lowering kVp along with mAs reductions. In a study performed by Jee and Newman (2010), reducing kVp values from 120 to 80 along with dose modulation software had little effect on image noise when scaning pediatric phantoms. The study showed that employing simple weight-based kVp techniques in addition to already low mAs values as radiation dose protocols resulted in significant dose reductions in pediatric CT examinations then were seen with mAs reductions alone while image quality remained acceptable (Jee & Newman, 2010). An example of a dose reduction tool is Siemens CARE Dose4D. This tool works by measuring attenuation profiles form the "scout" topogram taken before the scan is performed. Kalra and Brady (n.d.) explain that CARE Dose4D measures attentuation profiles in the z-axis and also in the perpendicular direction with sophisticated algorithms and the tube current values are calculated and customized to the patient's size and attenuation profiles. Based on these tube current customized settings, real-time tube current modulation can be obtained durring each tube rotation according to the size and shape of the patient (Kalra & Brady, n. d.). Ulzheimer et al. (2011) explains that finding the right balance or relationship between tube current, tube voltage, and image quality is an intricate procedure and that adjusting tube voltage to each individual patient and exam is challenging if not time consuming. To overcome challenges such as these, Siemens has developed a new tool to go along with CARE Dose4D, so named CARE kV. CARE kV automatically adjusts tube voltage for individual patients and clinical indications as well as for pediatric patients (Ulzheimer et al., 2011). Using CARE kV alone without tube modulation can cause an increase in noise. Ulzheimer et al. (2011) points out that “It is essential to adjust tube current when changing the kV settings and this task will be automaticlly acccomplished with CARE kV. Taking into account the patient’s size and clinical indication, CARE kV will automatically recommend the optimal tube voltage and tube current.” With the use of CARE kV, technologist error along with radiation dose can be minimized while diagnostic quality can be optimized.
Patient Positioning One other important fact that the presentation points out is the importance of proper patient positioning within the ganty of the CT scanner. In a study conducted by Toth et al. (2007) with the use of phantoms, miscentering the patient by as little as 3cm and 6cm within the isocenter of the gantry can cause an increase in surface and peripheral doses to the patient by as much as 18% and 41% (as cited in Seeram, 2009, p. 234). The presentation discusses ways in which the technologist can minimize radiation dose to the lense of the eyes by tilting the gantry and through careful positioning, as well as the use of orbit and thyroid shields to aid in the dose reduction of these radiosensitive areas. The presentation encourages technologists to consult with the radiologist or medical physicist about appropriate shielding guidelines. Communication is one of the key elements that technologists and physicians can use to be sure that the best interest of the patient is at hand and that every precaution is taken to perform CT head examinations on pediatric patients with doses as low as reasonalby achievabel to obtain a quality diagnostic study.
Computed Tomography Dose Index The presentation stressed the importance of using the Computed Tomography Dose Index (CTDI) even though it stated that there is currently no method available to give an accurate reading on the actual dose received from a pediatric head CT. The presention expalins that the CTDI gives an approximation of the dose an adult sized phantom would receive and states that the smaller a patient is in regards to the reference phantom the more innacuarate the dose displayed will be causing an underestimation of the actual patient dose by a factor of 3. Unfortunately, the speaker in the presentation seemed to rush through this particular subject. Comprehension of the subject material in this part of the presentation may be difficult due to the speed at which the narator was speaking. It would have helped the audience to have had check point slides on this material to reinforce the subject matter due to its complexity.
Presentation Critique The overall appearance of the slides in this presentation were easy to read. It is suggested that when creating Power Point slides, the use of light backgrounds along with dark san serif fonts such as Arial and Tahoma which are more pleasing to the eye and much esier to read then serif fonts such as Times New Roman (Archambeau, 2007). The use of soft green and yellow pastel colors are a good choice for a presentation regarding pediatric CT examinations. The black sans serif font against the light background was easy on the eyes which makes reading the content on the slides easy and comprehensibe. The use of the butterfly on each of the slides was a good fit to go along with a campaign on Imaging Gently. The speakers voice was clear and sentences were consise sticking to the most important content in pediatric CT imaging of the head, although the rate of the speakers voice was little to fast at times in the presentation. The content of the presentation included all the key areas that technologists, physicians, and parents need to consider and ask themselves before deciding on or initiating a CT head examination when a pediatric patient is involved. The presentation did an excellent job of putting into perspective the importance of exam justification, optimization, and dose reduction principles (ALARA) in pediatric imaging to lessen the risk of latent effects. There could have been more emphasis on images depiciting the types of shields available as well as CT images on monitors depicting where the CTDI numbers are typically demonstated.
Conclusion
New technology in computed tomography such as multiple slice CT (MSCT) scanners bring about new concerns for dose reduction since large volumes of tissue can be scanned faster than Single Slice CT (SSCT) scanners. Along with this new technology comes automated tools that can monitor and adjust technique protocols according to a patient's weight, body size and shape. With this said, it is important for technologists, physicians and radiologists to be competent and knowlegeable on the use of these tools and employ proper patient protocols when scanning pediatric patients. Improved efforts need to be made by imaging departments and professional organizations to set up educational seminares on radiation reduction techniques for staff technologists, radiologists and referring physicians. The Image Gently campaign is a prime example of what professional organizations can do through the use of on-line presentations to educate technologists, physicians, and the public, about the importance of radiation protection when imaging pediatric patients. With educational services such as these, professional competence and image protocol standardization may someday be achieved throughout all imaging facilities.

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