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Patient and operating room personnel radiation exposure in spinal surgery
Letters to the Editor / The Spine Journal 15 (2015) 796–800
cadaveric study’’ published by Chau et al. [1] in the October issue of The Spine Journal. The authors are to be commended for contributing important data to the growing literature on microanatomic features of the lumbar ligamentum flavum which are relevant to spinal microsurgery. In 1949/1950, Herzog [2] published a detailed anatomic and pathologic description of the ligamentum flavum, describing the so-called hypertrophy of the ligamentum flavum in different spinal levels. Picket [3] in 1963 outlined the role of the ligamenta flava in low back and sciatic pain after studying 139 specimens of ligamentum flavum grossly and microscopically. In terms of small surgical exposure during minimally invasive surgical procedures of the lumbar spine, the ligamentum flavum serves as a landmark for the exact localization of the nerve roots [4]. The article by Chau et al. [1] demonstrates three patterns of relationships between the lateral border of the ligamentum flavum and the intervertebral foramen. We would like to add the findings of Winkler et al. [5], who demonstrated a correlation between microanatomic and magnetic resonance imaging studies concerning the far lateral border and the extraforaminal course of the ligamentum flavum. The median distance between the midline and the far lateral and extraforaminal extent of the ligamentum flavum was 17 mm. Discrepancies between microanatomic and magnetic resonance imaging measurements did not exceed 1.5 mm. Thus, the extent of the far lateral ligamentum flavum can be precisely visualized for surgical planning before minimal invasive decompressive procedures for release of the entrapped nerve roots in the recess and foramen. References [1] Chau AM, Pelzer NR, Hampton J, Smith A, Seex KA, Stewart F, et al. Lateral extent and ventral laminar attachments oft he lumbar ligamentum flavum: cadaveric study. Spine J 2014;14: 2467–71. [2] Herzog W. Zur Morphologie und Pathologie des Ligamentum flavum. Frankfurter Zeitschrift f€ur Pathologie 1950;61:250–67. [3] Pickett JC. The lumbar ligamentum flavum in low back pain and sciatic pain. Southern Medical Journal 1963;56:1036–42. [4] Losiniecki AJ, Serrone JC, Keller JT, Bohinski RJ. Lumbar ligamentum flavum: spatial relationships to surrounding anatomical structures and technical description of en bloc resection. J Neurol Surg A Cent Eur Neurosurg 2013;74:388–92. [5] Winkler PA, Zausinger S, Milz S, Buettner A, Wiesmann M, Tonn JC. Morphometric studies of the ligamantum flavum: a correlative microanatomical and MRI study oft he lumbar spine. Zentralbl Neurochir 2007;68:200–4.
Juergen Volker Anton, MD Peter A. Winkler, MD, PhD Department of Neurosurgery Paracelsus Private Medical University Christian-Doppler-Klinik
797
Ignaz Harrer Strasse 79 A-5020 Salzburg Austria FDA device/drug status: Not applicable. Author disclosures: JVA: Nothing to disclose. PAW: Nothing to disclose. 1529-9430 Ó 2015 Elsevier Inc. All rights reserved http://dx.doi.org/10.1016/j.spinee.2015.01.011
Reply to commentary on ‘‘Lateral extent and ventral laminar attachments of the lumbar ligamentum flavum: cadaveric study’’ Dear Editor, We thank Drs. Anton and Winkler for their comments on our article [1] and for drawing attention to the importance of older and non-English anatomical literature. As the authors have mentioned, knowledge of the lateral extent of the ligamentum flavum is important for surgical planning, intraoperative localization, and adequate neural decompression. Our examination of the ligamenta flava of cadavers and in patients has also helped us in the development of a surgical instrument dubbed the ‘Gragnaniello’s dissector’ (unpublished), designed to effectively resect the ligamentum from the inside of the spinal canal, while minimizing the risk of damage to the dura. Reference [1] Chau AM, Pelzer NR, Hampton J, Smith A, Seex KA, Stewart F, et al. Lateral extent and ventral laminar attachments of the lumbar ligamentum flavum: cadaveric study. Spine J 2014;14:2467–71.
Anthony M.T. Chau, MBBS (Hons), MAppAnatDiss Kevin Seex, MB, ChB, FRCS, FRACS Cristian Gragnaniello, MD, PhD, MSurg, MAdvSurg, FICS Macquarie Neurosurgery Australian School of Advanced Medicine Macquarie University Hospital Suite 201, 2 Technology Place Macquarie University 2109 Sydney, Australia FDA device/drug status: Not applicable (Gragnaniello’s dissector). Author disclosures: AMTC: Nothing to disclose. KS: Nothing to disclose. CG: Nothing to disclose. 1529-9430 Ó 2015 Elsevier Inc. All rights reserved http://dx.doi.org/10.1016/j.spinee.2014.12.016
Patient and operating room personnel radiation exposure in spinal surgery To the Editor: It was with great interest that we read the article entitled ‘‘intraoperative fluoroscopy, portable X-ray, and CT:
798
Letters to the Editor / The Spine Journal 15 (2015) 796–800
patient and operating room personnel radiation exposure in spinal surgery’’ published in The Spine Journal [1]. This in vitro study used the experimental model to determine the amount of radiation exposure to patients and operating room staff during spine surgery with X-ray, C-arm, and O-arm fluoroscopy. However, we have several concerns regarding the design of the study. Firstly, it is a feeble argument that ‘‘assessment of radiation risk to the patient and operating room staff should be part of the decision for utilization of any specific imaging modality during spinal surgery.’’ The inconvenient truth is that, in real practice, if the institution has X-ray and C-arm machines, the surgeons will choose C-arm fluoroscopy rather than X-ray as the imaging modality during spinal surgery. That is because C-arm fluoroscopy provides clearer visualization and may improve the accuracy of pedicle screw placement. As for the concerns of radiation exposure, most of the surgeons wear leaded apron and thyroid gland shield in real spinal surgery with C-arm fluoroscopy, which has been reported to reduce most of the radiation exposure [2]. However, this condition is not simulated and compared in the presented study. Furthermore, the fluoroscopy times and duration are not clearly simulated and determined for each imaging modality in the presented study, which are another two key factors to assess the total radiation exposure in real practice for each single surgery. What is the guiding significance of this experimental study, if it did not simulate the real condition? Secondly, numerous studies have compared the radiation exposure and benefits of C-arm and O-arm fluoroscopy [1], so it is a nice try to integrate X-ray into the comparison. However, the presented study did not investigate and compare the merits of each imaging modality, such as the accuracy of pedicle screw placement. It is not convincing at all to claim that ‘‘this study provides the surgeon with information to better weigh the risks and benefits of each imaging modality.’’ Last but not least, it isn’t of scientific rigors to simulate the patient with surrogate phantom comprising 12123/8 inch polymethyl methacrylate. It was well known that scatter radiation was correlated with the anatomy of patient body, or even the shape of the operating table, and surrounding instruments because of reflex and refraction. Why not use the anthropometric rando phantom (RS-111; Radiology Support Devices, Long Beach, CA), a well validated tool [3,4], to simulate the patient? In conclusion, we strongly recommend adding the simulating condition of wearing leaded apron and thyroid gland shield and clearly setting the fluoroscopy times and duration of each imaging modality in real utilization for this comparative study (Figure). We also recommend, in the future comparative study, measuring the radiation exposure to sensitive organs of rando phantom to calculate allowed spinal surgery amount according to the
Figure. The schematic diagram of C-arm fluoroscopy simulating the real practice. Measurement spots include eyes, thyroid gland, and gonad gland, where dosimeters can be inserted into the corresponding location of the anthropometric rando phantom.
annual limits of International Commission on Radiologic Protection [5]. References [1] Nelson EM, Monazzam SM, Kim KD, Seibert JA, Klineberg EO. Intraoperative fluoroscopy, portable X-ray, and CT: patient and operating room personnel radiation exposure in spinal surgery. Spine J 2014;14:2985–91. [2] Choi HC. Fluoroscopic radiation exposure during percutaneous kyphoplasty. J Korean Neurosurg Soc 2011;49:37–42. [3] Lee SY, Min E, Bae J, Chung CY, Lee KM, Kwon SS, et al. Types and arrangement of thyroid shields to reduce exposure of surgeons to ionizing radiation during intraoperative use of C-arm fluoroscopy. Spine 2013;38:2108–12. [4] Lee K, Lee KM, Park MS, Lee B, Kwon DG, Chung CY. Measurements of surgeons’ exposure to ionizing radiation dose during intraoperative use of C-arm fluoroscopy. Spine 2012;37:1240–4. [5] Fan G, Zhao S, He S, Gu X, Guan X. Fluoroscopic radiation exposure to operating room personnel in spinal surgery. J Spinal Disord Tech 2014;28:28.
Guoxin Fan, MD Department of Orthopaedics Shanghai Tenth People’s Hospital Tongji University School of Medicine 301 Yanchang Rd. Shanghai, China Qingsong Fu, MD Department of Orthopaedics Ningbo No. 2 Hospital 14 Northwest Ningbo, China Xinbo Wu, Xiaofei Guan, Guangfei Gu, Shunzhi Yu,
MD MD MD MD
Letters to the Editor / The Spine Journal 15 (2015) 796–800
Hailong Zhang, MD Shisheng He, MD Department of Orthopaedics Shanghai Tenth People’s Hospital Tongji University School of Medicine 301 Yanchang Rd. Shanghai, China FDA device/drug status: Not applicable. Author disclosures: GF: Nothing to disclose. QF: Nothing to disclose. XW: Nothing to disclose. XG: Nothing to disclose. GG: Nothing to disclose. SY: Nothing to disclose. HZ: Nothing to disclose. SH: Nothing to disclose. Conflict of interest: None declared. 1529-9430 Ó 2015 Elsevier Inc. All rights reserved http://dx.doi.org/10.1016/j.spinee.2014.09.034
Intraoperative fluoroscopy, portable X-ray, and computed tomography: patient and operating room personnel radiation exposure in spinal surgery Thank you for your interest in our article ‘‘Intraoperative fluoroscopy, portable X-ray, and CT: patient and operating room personnel radiation exposure in spinal surgery’’ [1]. Radiation exposure is a critically important variable in the operating room, not only for ourselves, but also for the patients. The goal of this research was to determine the radiation exposure using common imaging devices, including the C-arm, portable X-ray, and the O-arm. We found significant differences based on the modality and location of the personnel in the operating room. Radiation dosage and image quality require a cost benefit analysis for both us and the patients. Higher radiation increases the image quality, but at what cost? We would disagree that most surgeons would choose C-arm over X-ray (if given the choice) or that C-arm has improved visualization over X-ray. This is clearly an individual surgeon-driven choice, which has as much to do with geographic location, convenience, and surgical procedure as it does with image quality and radiation dose. At our own institution, for example, one surgeon uses a free-hand pedicle screw technique for all screws and confirms their placement with X-ray at the end of the case versus another who uses C-arm throughout the case to confirm screw placement. Additionally, radiation is used in many cases for simple localization, and often, the imaging of choice is based on convenience. Our goal was to demonstrate that these casual choices do have a radiation impact on us and our patients. You are correct in pointing out that protective shields are of critical importance in reducing the radiation dose for surgeons and other operating room personnel. We
799
found in our study that the surgeon received the greatest radiation scatter dose, particularly with the C-arm and when positioned on the X-ray tube side with the C-arm in lateral orientation. However, as the protective shields offer excellent protection, studying the radiation dose in a protected individual is not particularly helpful. Additionally, the surgeon, operating room staff, and the anesthesiologist need to remain compliant with wearing the protective shields for them to be effective. This study demonstrates the very real radiation exposure encountered with the utilization of these image modalities and further encourages protective equipment for not only the surgeon but the entire operating room staff. We chose to use a single image as our standard for our C-arm/X-ray/O-arm exposure to allow the reader to extrapolate the radiation information to their own practice. Many factors go into the total number of image acquisitions performed during one surgery, including but not limited to the type of surgery, experience of the surgeon, surgical technique, institutional limitations, and unique factors to each patient such as body habitus. It would not only be impossible to determine the radiation exposure for each of these difference scenarios, but the reader would have limited ability to extrapolate our findings to their own unique practice and clinical scenarios. This exact point was actually the major criticism we had of the available literature and a major reason for our interest in conducting this study. Regarding the choice of image modality for screw placement, this is truly beyond the scope of this study. Pedicle screw placement is dependent on experience, technique, and finally imaging choice. Again this requires an assessment of the risks of radiation versus its benefit. We know that with advanced imaging we can more accurately place pedicle screws, but this improved accuracy does have a radiation cost for our patients and ourselves [2]. As for the use of a Poly(methyl methacrylate) phantom, our goal was to provide X-ray attenuation and scatter material to simulate a patient of approximately a BMI of 27.4, which was represented by a phantom of 30 sheets of lucite. This is a commonly applied phantom and method to measure peak skin dose to a patient (the plastic phantom) and the environmental scatter levels at locations where operating room personnel are commonly working. Our intent was not to estimate the ‘‘effective dose’’ to personnel in the room as inferred by references [3–5] in the Letter to the Editor, but to compare the relative levels of scatter emanating from the phantom (simulated patient undergoing surgery) for each procedure, evaluated at specific locations in the room. This provides an estimate of the unshielded radiation exposure to the operating room personnel. References [3–5] describe excellent ways in which surgeons and other operating room personnel can protect themselves from these radiation levels, by using appropriate shielding and safe use of the imaging equipment. Additionally, the value of
cadaveric study’’ published by Chau et al. [1] in the October issue of The Spine Journal. The authors are to be commended for contributing important data to the growing literature on microanatomic features of the lumbar ligamentum flavum which are relevant to spinal microsurgery. In 1949/1950, Herzog [2] published a detailed anatomic and pathologic description of the ligamentum flavum, describing the so-called hypertrophy of the ligamentum flavum in different spinal levels. Picket [3] in 1963 outlined the role of the ligamenta flava in low back and sciatic pain after studying 139 specimens of ligamentum flavum grossly and microscopically. In terms of small surgical exposure during minimally invasive surgical procedures of the lumbar spine, the ligamentum flavum serves as a landmark for the exact localization of the nerve roots [4]. The article by Chau et al. [1] demonstrates three patterns of relationships between the lateral border of the ligamentum flavum and the intervertebral foramen. We would like to add the findings of Winkler et al. [5], who demonstrated a correlation between microanatomic and magnetic resonance imaging studies concerning the far lateral border and the extraforaminal course of the ligamentum flavum. The median distance between the midline and the far lateral and extraforaminal extent of the ligamentum flavum was 17 mm. Discrepancies between microanatomic and magnetic resonance imaging measurements did not exceed 1.5 mm. Thus, the extent of the far lateral ligamentum flavum can be precisely visualized for surgical planning before minimal invasive decompressive procedures for release of the entrapped nerve roots in the recess and foramen. References [1] Chau AM, Pelzer NR, Hampton J, Smith A, Seex KA, Stewart F, et al. Lateral extent and ventral laminar attachments oft he lumbar ligamentum flavum: cadaveric study. Spine J 2014;14: 2467–71. [2] Herzog W. Zur Morphologie und Pathologie des Ligamentum flavum. Frankfurter Zeitschrift f€ur Pathologie 1950;61:250–67. [3] Pickett JC. The lumbar ligamentum flavum in low back pain and sciatic pain. Southern Medical Journal 1963;56:1036–42. [4] Losiniecki AJ, Serrone JC, Keller JT, Bohinski RJ. Lumbar ligamentum flavum: spatial relationships to surrounding anatomical structures and technical description of en bloc resection. J Neurol Surg A Cent Eur Neurosurg 2013;74:388–92. [5] Winkler PA, Zausinger S, Milz S, Buettner A, Wiesmann M, Tonn JC. Morphometric studies of the ligamantum flavum: a correlative microanatomical and MRI study oft he lumbar spine. Zentralbl Neurochir 2007;68:200–4.
Juergen Volker Anton, MD Peter A. Winkler, MD, PhD Department of Neurosurgery Paracelsus Private Medical University Christian-Doppler-Klinik
797
Ignaz Harrer Strasse 79 A-5020 Salzburg Austria FDA device/drug status: Not applicable. Author disclosures: JVA: Nothing to disclose. PAW: Nothing to disclose. 1529-9430 Ó 2015 Elsevier Inc. All rights reserved http://dx.doi.org/10.1016/j.spinee.2015.01.011
Reply to commentary on ‘‘Lateral extent and ventral laminar attachments of the lumbar ligamentum flavum: cadaveric study’’ Dear Editor, We thank Drs. Anton and Winkler for their comments on our article [1] and for drawing attention to the importance of older and non-English anatomical literature. As the authors have mentioned, knowledge of the lateral extent of the ligamentum flavum is important for surgical planning, intraoperative localization, and adequate neural decompression. Our examination of the ligamenta flava of cadavers and in patients has also helped us in the development of a surgical instrument dubbed the ‘Gragnaniello’s dissector’ (unpublished), designed to effectively resect the ligamentum from the inside of the spinal canal, while minimizing the risk of damage to the dura. Reference [1] Chau AM, Pelzer NR, Hampton J, Smith A, Seex KA, Stewart F, et al. Lateral extent and ventral laminar attachments of the lumbar ligamentum flavum: cadaveric study. Spine J 2014;14:2467–71.
Anthony M.T. Chau, MBBS (Hons), MAppAnatDiss Kevin Seex, MB, ChB, FRCS, FRACS Cristian Gragnaniello, MD, PhD, MSurg, MAdvSurg, FICS Macquarie Neurosurgery Australian School of Advanced Medicine Macquarie University Hospital Suite 201, 2 Technology Place Macquarie University 2109 Sydney, Australia FDA device/drug status: Not applicable (Gragnaniello’s dissector). Author disclosures: AMTC: Nothing to disclose. KS: Nothing to disclose. CG: Nothing to disclose. 1529-9430 Ó 2015 Elsevier Inc. All rights reserved http://dx.doi.org/10.1016/j.spinee.2014.12.016
Patient and operating room personnel radiation exposure in spinal surgery To the Editor: It was with great interest that we read the article entitled ‘‘intraoperative fluoroscopy, portable X-ray, and CT:
798
Letters to the Editor / The Spine Journal 15 (2015) 796–800
patient and operating room personnel radiation exposure in spinal surgery’’ published in The Spine Journal [1]. This in vitro study used the experimental model to determine the amount of radiation exposure to patients and operating room staff during spine surgery with X-ray, C-arm, and O-arm fluoroscopy. However, we have several concerns regarding the design of the study. Firstly, it is a feeble argument that ‘‘assessment of radiation risk to the patient and operating room staff should be part of the decision for utilization of any specific imaging modality during spinal surgery.’’ The inconvenient truth is that, in real practice, if the institution has X-ray and C-arm machines, the surgeons will choose C-arm fluoroscopy rather than X-ray as the imaging modality during spinal surgery. That is because C-arm fluoroscopy provides clearer visualization and may improve the accuracy of pedicle screw placement. As for the concerns of radiation exposure, most of the surgeons wear leaded apron and thyroid gland shield in real spinal surgery with C-arm fluoroscopy, which has been reported to reduce most of the radiation exposure [2]. However, this condition is not simulated and compared in the presented study. Furthermore, the fluoroscopy times and duration are not clearly simulated and determined for each imaging modality in the presented study, which are another two key factors to assess the total radiation exposure in real practice for each single surgery. What is the guiding significance of this experimental study, if it did not simulate the real condition? Secondly, numerous studies have compared the radiation exposure and benefits of C-arm and O-arm fluoroscopy [1], so it is a nice try to integrate X-ray into the comparison. However, the presented study did not investigate and compare the merits of each imaging modality, such as the accuracy of pedicle screw placement. It is not convincing at all to claim that ‘‘this study provides the surgeon with information to better weigh the risks and benefits of each imaging modality.’’ Last but not least, it isn’t of scientific rigors to simulate the patient with surrogate phantom comprising 12123/8 inch polymethyl methacrylate. It was well known that scatter radiation was correlated with the anatomy of patient body, or even the shape of the operating table, and surrounding instruments because of reflex and refraction. Why not use the anthropometric rando phantom (RS-111; Radiology Support Devices, Long Beach, CA), a well validated tool [3,4], to simulate the patient? In conclusion, we strongly recommend adding the simulating condition of wearing leaded apron and thyroid gland shield and clearly setting the fluoroscopy times and duration of each imaging modality in real utilization for this comparative study (Figure). We also recommend, in the future comparative study, measuring the radiation exposure to sensitive organs of rando phantom to calculate allowed spinal surgery amount according to the
Figure. The schematic diagram of C-arm fluoroscopy simulating the real practice. Measurement spots include eyes, thyroid gland, and gonad gland, where dosimeters can be inserted into the corresponding location of the anthropometric rando phantom.
annual limits of International Commission on Radiologic Protection [5]. References [1] Nelson EM, Monazzam SM, Kim KD, Seibert JA, Klineberg EO. Intraoperative fluoroscopy, portable X-ray, and CT: patient and operating room personnel radiation exposure in spinal surgery. Spine J 2014;14:2985–91. [2] Choi HC. Fluoroscopic radiation exposure during percutaneous kyphoplasty. J Korean Neurosurg Soc 2011;49:37–42. [3] Lee SY, Min E, Bae J, Chung CY, Lee KM, Kwon SS, et al. Types and arrangement of thyroid shields to reduce exposure of surgeons to ionizing radiation during intraoperative use of C-arm fluoroscopy. Spine 2013;38:2108–12. [4] Lee K, Lee KM, Park MS, Lee B, Kwon DG, Chung CY. Measurements of surgeons’ exposure to ionizing radiation dose during intraoperative use of C-arm fluoroscopy. Spine 2012;37:1240–4. [5] Fan G, Zhao S, He S, Gu X, Guan X. Fluoroscopic radiation exposure to operating room personnel in spinal surgery. J Spinal Disord Tech 2014;28:28.
Guoxin Fan, MD Department of Orthopaedics Shanghai Tenth People’s Hospital Tongji University School of Medicine 301 Yanchang Rd. Shanghai, China Qingsong Fu, MD Department of Orthopaedics Ningbo No. 2 Hospital 14 Northwest Ningbo, China Xinbo Wu, Xiaofei Guan, Guangfei Gu, Shunzhi Yu,
MD MD MD MD
Letters to the Editor / The Spine Journal 15 (2015) 796–800
Hailong Zhang, MD Shisheng He, MD Department of Orthopaedics Shanghai Tenth People’s Hospital Tongji University School of Medicine 301 Yanchang Rd. Shanghai, China FDA device/drug status: Not applicable. Author disclosures: GF: Nothing to disclose. QF: Nothing to disclose. XW: Nothing to disclose. XG: Nothing to disclose. GG: Nothing to disclose. SY: Nothing to disclose. HZ: Nothing to disclose. SH: Nothing to disclose. Conflict of interest: None declared. 1529-9430 Ó 2015 Elsevier Inc. All rights reserved http://dx.doi.org/10.1016/j.spinee.2014.09.034
Intraoperative fluoroscopy, portable X-ray, and computed tomography: patient and operating room personnel radiation exposure in spinal surgery Thank you for your interest in our article ‘‘Intraoperative fluoroscopy, portable X-ray, and CT: patient and operating room personnel radiation exposure in spinal surgery’’ [1]. Radiation exposure is a critically important variable in the operating room, not only for ourselves, but also for the patients. The goal of this research was to determine the radiation exposure using common imaging devices, including the C-arm, portable X-ray, and the O-arm. We found significant differences based on the modality and location of the personnel in the operating room. Radiation dosage and image quality require a cost benefit analysis for both us and the patients. Higher radiation increases the image quality, but at what cost? We would disagree that most surgeons would choose C-arm over X-ray (if given the choice) or that C-arm has improved visualization over X-ray. This is clearly an individual surgeon-driven choice, which has as much to do with geographic location, convenience, and surgical procedure as it does with image quality and radiation dose. At our own institution, for example, one surgeon uses a free-hand pedicle screw technique for all screws and confirms their placement with X-ray at the end of the case versus another who uses C-arm throughout the case to confirm screw placement. Additionally, radiation is used in many cases for simple localization, and often, the imaging of choice is based on convenience. Our goal was to demonstrate that these casual choices do have a radiation impact on us and our patients. You are correct in pointing out that protective shields are of critical importance in reducing the radiation dose for surgeons and other operating room personnel. We
799
found in our study that the surgeon received the greatest radiation scatter dose, particularly with the C-arm and when positioned on the X-ray tube side with the C-arm in lateral orientation. However, as the protective shields offer excellent protection, studying the radiation dose in a protected individual is not particularly helpful. Additionally, the surgeon, operating room staff, and the anesthesiologist need to remain compliant with wearing the protective shields for them to be effective. This study demonstrates the very real radiation exposure encountered with the utilization of these image modalities and further encourages protective equipment for not only the surgeon but the entire operating room staff. We chose to use a single image as our standard for our C-arm/X-ray/O-arm exposure to allow the reader to extrapolate the radiation information to their own practice. Many factors go into the total number of image acquisitions performed during one surgery, including but not limited to the type of surgery, experience of the surgeon, surgical technique, institutional limitations, and unique factors to each patient such as body habitus. It would not only be impossible to determine the radiation exposure for each of these difference scenarios, but the reader would have limited ability to extrapolate our findings to their own unique practice and clinical scenarios. This exact point was actually the major criticism we had of the available literature and a major reason for our interest in conducting this study. Regarding the choice of image modality for screw placement, this is truly beyond the scope of this study. Pedicle screw placement is dependent on experience, technique, and finally imaging choice. Again this requires an assessment of the risks of radiation versus its benefit. We know that with advanced imaging we can more accurately place pedicle screws, but this improved accuracy does have a radiation cost for our patients and ourselves [2]. As for the use of a Poly(methyl methacrylate) phantom, our goal was to provide X-ray attenuation and scatter material to simulate a patient of approximately a BMI of 27.4, which was represented by a phantom of 30 sheets of lucite. This is a commonly applied phantom and method to measure peak skin dose to a patient (the plastic phantom) and the environmental scatter levels at locations where operating room personnel are commonly working. Our intent was not to estimate the ‘‘effective dose’’ to personnel in the room as inferred by references [3–5] in the Letter to the Editor, but to compare the relative levels of scatter emanating from the phantom (simulated patient undergoing surgery) for each procedure, evaluated at specific locations in the room. This provides an estimate of the unshielded radiation exposure to the operating room personnel. References [3–5] describe excellent ways in which surgeons and other operating room personnel can protect themselves from these radiation levels, by using appropriate shielding and safe use of the imaging equipment. Additionally, the value of