Pediatr Radiol (2014) 44 (Suppl 3):S489–S491 DOI 10.1007/s00247-014-3136-4
IMAGE GENTLY ALARA CT SUMMIT: HOW TO USE NEW CT TECHNOLOGIES FOR CHILDREN
Development of pediatric CT protocols for specific scanners: why bother? Dianna D. Cody
Received: 20 February 2014 / Revised: 8 July 2014 / Accepted: 18 July 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract When determining a strategy for pediatric CT scanning, clinical staff can either elect to adjust routine adultprotocol parameter settings on a case-by-case basis or rely on pre-set pediatric protocol parameters. The advantages of the latter approach are the topic of this manuscript. This paper outlines specific options to consider, including the need for regular protocol review. Keywords Protocols . Computed tomography . Pediatric
Why a scanner-based strategy is best One effective strategy for handling pediatric exams is the development of a set of protocols with parameters that are specific to pediatric patients for each relevant CT scanner model in the department. Logistics may be such that pediatric exams are performed on only some of the CT scanners, which may be more appropriate for pediatric patients for one reason or another. These scanners can be targeted for pediatric CT protocol development efforts. There are many advantages to this approach. The most powerful is that it allows the staff to take full advantage of the best technologies available on each scanner to their fullest capability, provided that the required time is invested to learn and understand how to best leverage the special features of each scanner. This can be very difficult to accomplish on an ad hoc basis. When tackled on an individual-scanner-model basis, the optimal combination of parameter selections can be D. D. Cody (*) Department of Imaging Physics, University of Texas M.D. Anderson Cancer Center, 1400 Pressler Ave., Unit 1472, Houston, TX 77030, USA e-mail: [email protected]
thought through (and tested) well ahead of time, which should result in optimal image quality for clinical exams. Attempting to develop a generic set of pediatric protocol parameters for all scanners, to be adjusted for each exam and each scanner on a case-by-case basis [1], however, will lead to a less-than-perfect result. It is very rare that all of the target parameters are available together on all of the target scanners. When a mismatch of parameters emerges, the technologist operator will be forced to make a decision, very quickly and under pressure, regarding how to adjust the parameters to best match the intended result. Often a compromise is required, which can be very stressful for the technologist. The pressure on the scanning technologist in this scenario is even more acute if a short-acting sedative is being used to keep the child sufficiently still while the scan is performed. CT scanners have become increasingly complex instruments; selecting or adjusting protocol parameters at the time of the exam can result in studies of inconsistent quality. Given the same situation, any two technologists are unlikely to make exactly the same decisions. And, over the course of time, a single technologist is unlikely to make exactly the same decision several times in a row when adjustments are routinely necessary during exams. This inter- and intra-technologist variability will result in exams with different parameter combinations and varying quality. Pre-set protocol parameters are more likely to result in fewer mistakes, fewer repeated exams, and smoother and less stressful workflow patterns. However, note that if time has not been invested to develop or obtain detailed, tested protocols for the specific scanners in the department, selecting or adjusting protocol parameters at the time of the exam based on dose indices provided by the scanner may better manage pediatric patient dose and image quality than using detailed protocols not specifically designed for the types of scanners in a given department.
S490
Size matters When developing or reviewing pediatric CT protocols, special attention should be directed to the patient size metric to be used to categorize the pediatric protocols. This is especially important in pediatric CT imaging, where patients often range in size from neonate to extra-large adults. Exam parameters must be tailored for patient size. The solutions to handle this have been quite variable. Some facilities use a combination of age and weight. Age alone is insufficient [2], except in the case of pediatric head CT. Some facilities utilize patient circumference or a surrogate for that, such as display field of view [3–5]. No single patient-size approach is likely to be 100% successful at characterizing the attenuation properties of a given region of the body. Patients of some size and shape combinations might have to be handled in a customized manner. In the future, if the CT scanner manufacturers allow the localizer view to be used to generate a generic, reported metric for patient size and attenuation pattern, this metric might be very useful as a patient size category for pediatric protocols. In the meantime, the Alliance for Radiation Safety in Pediatric Imaging (www.imagegently.org) recommends that the size of the lateral dimension of the supine patient be measured with simple mechanical calipers by the technologist to assist in classifying the size or attenuation properties of the region of the body to be scanned.
Pediatr Radiol (2014) 44 (Suppl 3):S489–S491
consideration. Communication among colleagues at different medical facilities (radiologist, technologist and physicist perspectives) can also be useful in collecting alternative parameter sets to evaluate. No matter how the initial protocol parameter set is developed, many groups recommend a periodic review of all CT protocol sets, including those for pediatric CT exams [9, 10]. A careful CT protocol review process should be established and carried out on a regular basis to confirm that the image quality being generated continues to meet the radiologists’ expectations; an annual review process would be optimal, but one every 2 years might suffice [9]. Radiation dose levels should be considered when pediatric CT protocols are developed or reviewed. Guidelines regarding dose values for pediatric CT can be found in various places [11–13]. Several studies have found that pediatric specialty radiology groups tend to perform pediatric CT at lower radiation dose levels than do radiology groups that serve both adult and pediatric patient populations [14, 15]. It would thus be wise to compare your site’s pediatric CT exam dose values with those at operations serving patient populations similar to yours.
Conflicts of interest Dr. Cody is the principal investigator of several inkind research projects in conjunction with GE Healthcare.
References Other factors The specific items to include in a pre-set protocol package depend on the scanner environment and the practice pattern. Some general tips would include use of the shortest rotation speed and pitch values greater than one, in order to minimize the scan time (and associated motion artifacts). It must be realized, however, that this combination of parameters can strain X-ray tube capacity, especially for larger patients. Some compromise of parameter settings is required in some cases. Additional parameters to pay special attention to include the scan field of view (for the most appropriate bow-tie selection), beam-on time, IV contrast timing, and image thickness. All capabilities on each scanner to further reduce dose should be implemented if possible. This includes the use of less noisy algorithms/filters/kernels for conventional image reconstruction, and the application of iterative reconstruction for scanners on which it is available. Several publications can be used to help design pediatric protocols by incorporating an iterative reconstruction mode [6–8]. Model pediatric CT protocol sets can be requested from the CT scanner manufacturer applications group; these should provide an excellent baseline. Adjustments can be made from this point according to the radiologists’ needs. Several online resources have protocol parameter sets available for
1. Strauss KJ (2014) Developing patient-specific dose protocols for a CT scanner and exam using diagnostic reference levels. Pediatr Radiol [In press] 2. Kleinman PL, Strauss KJ, Zurakowski D et al (2010) Patient size measured on CT images as a function of age at a tertiary care children’s hospital. AJR Am J Roentgenol 194:1611–1619 3. Reid J, Gamberoni J, Dong F et al (2010) Optimization of kVp and mAs for pediatric low-dose simulated abdominal CT: is it best to base parameter selection on object circumference? AJR Am J Roentgenol 195:1015–1020 4. Dong F, Davros W, Pozzuto J et al (2012) Optimization of kilovoltage and tube current-exposure time product based on abdominal circumference: an oval phantom study for pediatric abdominal CT. AJR Am J Roentgenol 199:670–676 5. Cody DD, Moxley DM, Krugh KT et al (2004) Strategies for formulating appropriate MDCT techniques when imaging the chest, abdomen and pelvis in pediatric patients. AJR Am J Roentgenol 182:849– 859 6. Brady SL, Yee BS, Kaufman RA (2012) Characterization of adaptive statistical iterative reconstruction algorithm for dose reduction in CT: a pediatric oncology perspective. Med Phys 39:5520–5531 7. Rampado O, Bossi L, Garabello D et al (2012) Characterization of a computed tomography iterative reconstruction algorithm by image quality evaluations with an anthropomorphic phantom. Eur J Radiol 81:3172–3177 8. Martinsen ACT, Saether HK, Hol PK et al (2012) Iterative reconstruction reduces abdominal CT dose. Eur J Radiol 81:1483–1487 9. Cody DD, Fisher TS, Gress DA et al (2013) AAPM medical physics practice guideline 1.a: CT protocol management and review practice guideline. J Appl Clin Med Phys 14:3–12
Pediatr Radiol (2014) 44 (Suppl 3):S489–S491 10. Cody DD, Pfeiffer D, McNitt-Gray MF et al (2012) American College of Radiology CT quality control manual. http://www.acr. org/Education/Education-Catalog/Products/8336734. Accessed 9 July 2014 11. Goske MJ, Strauss KJ, Coombs LP et al (2013) Diagnostic reference ranges for pediatric abdominal CT. Radiology 268:208–218 12. American College of Radiology (2013) ACR CT accreditation program requirements. http://www.acr.org/~/media/ACR/Documents/ Accreditation/CT/Requirements.pdf. Accessed 9 July 2014
S491 13. Dougeni E, Faulkner K, Panayiotakis G (2012) A review of patient dose and optimization methods in adult and paediatric CT scanning. Eur J Radiol 81:e665–e683 14. Borders HL, Barnes CL, Parks DC et al (2012) Use of a dedicated pediatric CT imaging service associated with decreased patient radiation dose. J Am Coll Radiol 9:340–343 15. Nosek AE, Hartin CW, Bass KD et al (2013) Are facilities following best practices of pediatric abdominal CT scans? J Surg Res 181:11–15
IMAGE GENTLY ALARA CT SUMMIT: HOW TO USE NEW CT TECHNOLOGIES FOR CHILDREN
Development of pediatric CT protocols for specific scanners: why bother? Dianna D. Cody
Received: 20 February 2014 / Revised: 8 July 2014 / Accepted: 18 July 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract When determining a strategy for pediatric CT scanning, clinical staff can either elect to adjust routine adultprotocol parameter settings on a case-by-case basis or rely on pre-set pediatric protocol parameters. The advantages of the latter approach are the topic of this manuscript. This paper outlines specific options to consider, including the need for regular protocol review. Keywords Protocols . Computed tomography . Pediatric
Why a scanner-based strategy is best One effective strategy for handling pediatric exams is the development of a set of protocols with parameters that are specific to pediatric patients for each relevant CT scanner model in the department. Logistics may be such that pediatric exams are performed on only some of the CT scanners, which may be more appropriate for pediatric patients for one reason or another. These scanners can be targeted for pediatric CT protocol development efforts. There are many advantages to this approach. The most powerful is that it allows the staff to take full advantage of the best technologies available on each scanner to their fullest capability, provided that the required time is invested to learn and understand how to best leverage the special features of each scanner. This can be very difficult to accomplish on an ad hoc basis. When tackled on an individual-scanner-model basis, the optimal combination of parameter selections can be D. D. Cody (*) Department of Imaging Physics, University of Texas M.D. Anderson Cancer Center, 1400 Pressler Ave., Unit 1472, Houston, TX 77030, USA e-mail: [email protected]
thought through (and tested) well ahead of time, which should result in optimal image quality for clinical exams. Attempting to develop a generic set of pediatric protocol parameters for all scanners, to be adjusted for each exam and each scanner on a case-by-case basis [1], however, will lead to a less-than-perfect result. It is very rare that all of the target parameters are available together on all of the target scanners. When a mismatch of parameters emerges, the technologist operator will be forced to make a decision, very quickly and under pressure, regarding how to adjust the parameters to best match the intended result. Often a compromise is required, which can be very stressful for the technologist. The pressure on the scanning technologist in this scenario is even more acute if a short-acting sedative is being used to keep the child sufficiently still while the scan is performed. CT scanners have become increasingly complex instruments; selecting or adjusting protocol parameters at the time of the exam can result in studies of inconsistent quality. Given the same situation, any two technologists are unlikely to make exactly the same decisions. And, over the course of time, a single technologist is unlikely to make exactly the same decision several times in a row when adjustments are routinely necessary during exams. This inter- and intra-technologist variability will result in exams with different parameter combinations and varying quality. Pre-set protocol parameters are more likely to result in fewer mistakes, fewer repeated exams, and smoother and less stressful workflow patterns. However, note that if time has not been invested to develop or obtain detailed, tested protocols for the specific scanners in the department, selecting or adjusting protocol parameters at the time of the exam based on dose indices provided by the scanner may better manage pediatric patient dose and image quality than using detailed protocols not specifically designed for the types of scanners in a given department.
S490
Size matters When developing or reviewing pediatric CT protocols, special attention should be directed to the patient size metric to be used to categorize the pediatric protocols. This is especially important in pediatric CT imaging, where patients often range in size from neonate to extra-large adults. Exam parameters must be tailored for patient size. The solutions to handle this have been quite variable. Some facilities use a combination of age and weight. Age alone is insufficient [2], except in the case of pediatric head CT. Some facilities utilize patient circumference or a surrogate for that, such as display field of view [3–5]. No single patient-size approach is likely to be 100% successful at characterizing the attenuation properties of a given region of the body. Patients of some size and shape combinations might have to be handled in a customized manner. In the future, if the CT scanner manufacturers allow the localizer view to be used to generate a generic, reported metric for patient size and attenuation pattern, this metric might be very useful as a patient size category for pediatric protocols. In the meantime, the Alliance for Radiation Safety in Pediatric Imaging (www.imagegently.org) recommends that the size of the lateral dimension of the supine patient be measured with simple mechanical calipers by the technologist to assist in classifying the size or attenuation properties of the region of the body to be scanned.
Pediatr Radiol (2014) 44 (Suppl 3):S489–S491
consideration. Communication among colleagues at different medical facilities (radiologist, technologist and physicist perspectives) can also be useful in collecting alternative parameter sets to evaluate. No matter how the initial protocol parameter set is developed, many groups recommend a periodic review of all CT protocol sets, including those for pediatric CT exams [9, 10]. A careful CT protocol review process should be established and carried out on a regular basis to confirm that the image quality being generated continues to meet the radiologists’ expectations; an annual review process would be optimal, but one every 2 years might suffice [9]. Radiation dose levels should be considered when pediatric CT protocols are developed or reviewed. Guidelines regarding dose values for pediatric CT can be found in various places [11–13]. Several studies have found that pediatric specialty radiology groups tend to perform pediatric CT at lower radiation dose levels than do radiology groups that serve both adult and pediatric patient populations [14, 15]. It would thus be wise to compare your site’s pediatric CT exam dose values with those at operations serving patient populations similar to yours.
Conflicts of interest Dr. Cody is the principal investigator of several inkind research projects in conjunction with GE Healthcare.
References Other factors The specific items to include in a pre-set protocol package depend on the scanner environment and the practice pattern. Some general tips would include use of the shortest rotation speed and pitch values greater than one, in order to minimize the scan time (and associated motion artifacts). It must be realized, however, that this combination of parameters can strain X-ray tube capacity, especially for larger patients. Some compromise of parameter settings is required in some cases. Additional parameters to pay special attention to include the scan field of view (for the most appropriate bow-tie selection), beam-on time, IV contrast timing, and image thickness. All capabilities on each scanner to further reduce dose should be implemented if possible. This includes the use of less noisy algorithms/filters/kernels for conventional image reconstruction, and the application of iterative reconstruction for scanners on which it is available. Several publications can be used to help design pediatric protocols by incorporating an iterative reconstruction mode [6–8]. Model pediatric CT protocol sets can be requested from the CT scanner manufacturer applications group; these should provide an excellent baseline. Adjustments can be made from this point according to the radiologists’ needs. Several online resources have protocol parameter sets available for
1. Strauss KJ (2014) Developing patient-specific dose protocols for a CT scanner and exam using diagnostic reference levels. Pediatr Radiol [In press] 2. Kleinman PL, Strauss KJ, Zurakowski D et al (2010) Patient size measured on CT images as a function of age at a tertiary care children’s hospital. AJR Am J Roentgenol 194:1611–1619 3. Reid J, Gamberoni J, Dong F et al (2010) Optimization of kVp and mAs for pediatric low-dose simulated abdominal CT: is it best to base parameter selection on object circumference? AJR Am J Roentgenol 195:1015–1020 4. Dong F, Davros W, Pozzuto J et al (2012) Optimization of kilovoltage and tube current-exposure time product based on abdominal circumference: an oval phantom study for pediatric abdominal CT. AJR Am J Roentgenol 199:670–676 5. Cody DD, Moxley DM, Krugh KT et al (2004) Strategies for formulating appropriate MDCT techniques when imaging the chest, abdomen and pelvis in pediatric patients. AJR Am J Roentgenol 182:849– 859 6. Brady SL, Yee BS, Kaufman RA (2012) Characterization of adaptive statistical iterative reconstruction algorithm for dose reduction in CT: a pediatric oncology perspective. Med Phys 39:5520–5531 7. Rampado O, Bossi L, Garabello D et al (2012) Characterization of a computed tomography iterative reconstruction algorithm by image quality evaluations with an anthropomorphic phantom. Eur J Radiol 81:3172–3177 8. Martinsen ACT, Saether HK, Hol PK et al (2012) Iterative reconstruction reduces abdominal CT dose. Eur J Radiol 81:1483–1487 9. Cody DD, Fisher TS, Gress DA et al (2013) AAPM medical physics practice guideline 1.a: CT protocol management and review practice guideline. J Appl Clin Med Phys 14:3–12
Pediatr Radiol (2014) 44 (Suppl 3):S489–S491 10. Cody DD, Pfeiffer D, McNitt-Gray MF et al (2012) American College of Radiology CT quality control manual. http://www.acr. org/Education/Education-Catalog/Products/8336734. Accessed 9 July 2014 11. Goske MJ, Strauss KJ, Coombs LP et al (2013) Diagnostic reference ranges for pediatric abdominal CT. Radiology 268:208–218 12. American College of Radiology (2013) ACR CT accreditation program requirements. http://www.acr.org/~/media/ACR/Documents/ Accreditation/CT/Requirements.pdf. Accessed 9 July 2014
S491 13. Dougeni E, Faulkner K, Panayiotakis G (2012) A review of patient dose and optimization methods in adult and paediatric CT scanning. Eur J Radiol 81:e665–e683 14. Borders HL, Barnes CL, Parks DC et al (2012) Use of a dedicated pediatric CT imaging service associated with decreased patient radiation dose. J Am Coll Radiol 9:340–343 15. Nosek AE, Hartin CW, Bass KD et al (2013) Are facilities following best practices of pediatric abdominal CT scans? J Surg Res 181:11–15
