- Email: [email protected]
Deterministic effects after fenestrated endovascular aortic aneurysm repair
From the Western Vascular Society
Deterministic effects after fenestrated endovascular aortic aneurysm repair Melissa L. Kirkwood, MD,a Gary M. Arbique, PhD,b Jeffrey B. Guild, PhD,b Carlos Timaran, MD,a Jon A. Anderson, PhD,b and R. James Valentine, MD,a Dallas, Tex Background: Endovascular aortic aneurysm repairs (EVARs) with fenestrated (FEVAR) stent grafts are high radiation dose cases, yet no skin injuries were found retrospectively in our 61 cases with a mean peak skin dose (PSD) of 6.8 Gy. We hypothesize that skin injury is under-reported. This study examined deterministic effects in FEVARs after procedural changes implemented to detect skin injury. Methods: All FEVARs during a 6-month period with a radiation dose of 5 Gy reference air kerma (RAK; National Council on Radiation Protection and Measurements threshold for substantial radiation dose level [SRDL]) were included. Patients were questioned about skin erythema, epilation, and necrosis, with a physical examination of the back completed daily until discharge and then at 2 and 4 weeks and at 3 and 6 months. PSD distributions were calculated with custom software using input data from fluoroscopic machine logs. These calculations have been validated against Gafchromic (Ashland Inc, Covington, Ky) film measurements. Dose was summed for the subset of patients with multiple procedures #6 months of the SRDL event, consistent with the joint commission recommendations. Results: Twenty-two patients, 21 FEVARs and one embolization, reached an RAK of 5 Gy. The embolization procedure was excluded from review. The average RAK was 7.6 6 2.0 Gy (range, 5.1-11.4 Gy), with a mean PSD of 4.8 6 2.0 Gy (range, 2.3-10.4 Gy). Fifty-two percent of patients had multiple endovascular procedures #6 months of the SRDL event. The mean RAK for this subset was 10.0 6 2.9 Gy (range, 5.5-15.1 Gy), with a mean PSD of 6.6 6 1.9 Gy (range, 3.4-9.4 Gy). One patient died before the first postoperative visit. No radiation skin injuries were found. Putative risk factors for skin injury were evaluated and included smoking (32%), diabetes (14%), cytotoxic drugs (9%), and fair skin type (91%). No other risk factors were present (hyperthyroidism, collagen vascular disorders). Conclusions: Deterministic skin injuries are uncommon after FEVAR, even at high RAK levels, regardless of cumulative dose effects. This study addresses the concern of missed injuries based on the retrospective clinical examination findings that were published in our previous work. Even with more comprehensive postoperative skin examinations and patient questioning, the fact that no skin injuries were found suggests that radiation-induced skin injuries are multifactorial and not solely dose dependent. (J Vasc Surg 2015;61:902-7.)
Deterministic skin injury is a biologic effect resulting from excessive radiation exposure. These effects are associated with a threshold radiation dose above which the severity of injury increases with increasing delivered dose.1 The most common deterministic effects are skin and eye injuries, which are infrequent but serious potential complications of fluoroscopically guided interventions (FGIs).2,3 The National Council on Radiation Protection and Measurements (NCRP) has defined a substantial
From the Division of Vascular and Endovascular Surgery, Department of Surgery,a and the Division of Medical Physics, Department of Radiology,b UT Southwestern Medical Center. Author conflict of interest: none. Presented at the Twenty-ninth Annual Meeting of the Western Vascular Society, Coronado, Calif, September 20-23, 2014. Reprint requests: Melissa L. Kirkwood, MD, UT Southwestern Medical Center, Professional Office Bldg 1, Ste 620, 5959 Harry Hines Blvd, Dallas, TX 75390-9157 (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2015 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2014.11.044
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radiation dose level (SRDL) to be a reference air kerma (RAK) of $5 Gy. This dose threshold is intended to trigger patient follow-up directed at detecting skin effects that may require further management.4 In addition, the Joint Commission’s recognition of skin doses >15 Gy as a reviewable sentinel event has led to increased awareness of patient skin injury during FGIs.5 Reports of deterministic skin injury are mostly limited to case reports after coronary interventions, neuroembolizations, and transjugular intrahepatic portosystemic shunt procedures.6-10 Fenestrated endovascular aortic aneurysm repair (FEVAR) is a complex procedure that requires consistently high radiation doses to complete; yet, the prevalence of deterministic skin injuries after FEVAR remains unknown.11 Our previous work retrospectively reviewed 61 complex endovascular procedures that met or exceeded SRDL dose criteria. Despite mean peak skin doses (PSDs) >6.5 Gy, with a range extending to 18 Gy, no skin injuries were found. This study was limited by its retrospective design, with no formal protocol in place to ensure that a thorough skin examination of each patient’s back was performed at every postoperative visit, nor was there a protocol established for direct patient questioning regarding skin
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Fig 1. Reference air kerma (RAK). IRP, Interventional reference point.
complaints. Although severe skin ulceration or necrosis would likely have been detected, it is reasonable to assume that minor skin injuries could have been missed.12 We hypothesized that a more thorough postoperative follow-up of patients would detect skin injury and address the deficiencies of our previous work. This study sought to examine the frequency and severity of deterministic effects and to evaluate patient characteristics that might predispose to radiation injury after FEVAR. METHODS This study was approved by the UT Southwestern Medical Center Institutional Review Board. Patient consent was waived due to the retrospective nature of the study. This study used the RAK as the dose metric because no real-time PSD meter is currently available during a procedure. The RAK is a measure of the radiation dose to air at a reference point that roughly correlates with the patient’s skin and offers the best estimate of patient skin dose during a procedure.4,13,14 On interventional fluoroscopes featuring isocentric gantries, this reference point is called the interventional reference point and is 15 cm toward the X-ray focal spot from isocenter (Fig 1). A new policy was implemented at the UT Southwestern Medical Center Division of Vascular Surgery for follow-up of FEVAR patients beginning in June 2013. At every postoperative FEVAR visit, the operating surgeon or vascular nurse practioner performed a full skin examination of the patient’s back and buttock region. In addition, FEVAR patients were questioned about any skin-related
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complaints, including erythema, epilation, necrosis, or ulceration. The physical examination findings and the patient questionnaire were documented in the medical record. All patients undergoing an FGI in an Allura Xper FD20 hybrid room (Phillips Health Care, Andover, Mass) from June 1, 2013, to December 31, 2013, were initially included. Radiation dose and machine operating factors were recorded for each procedure. The FGIs that required at $5 Gy RAK were identified. The outpatient and inpatient medical records of all patients meeting SRDL dose criteria at our institution were retrospectively reviewed specifically for evidence of skin injury. Patient comorbidities that might predispose to skin injury (ie, collagen vascular disorders, hyperthyroidism, diabetes, ethnicity, and smoking status) were recorded. Patients were examined daily in the hospital until discharge, at 2 and 4 weeks, and at 3 and 6 months. PSD distributions were calculated for all FGIs with $5 Gy RAK, and a dose index (PSD/RAK ratio)14 was determined for each case. These calculations were performed because combining PSD calculations based on RAK and machine geometry results in a better estimate of skin dose compared with RAK alone. RAK is defined relative to the X-ray source and not the patient; therefore, RAK does not account for changes in table position or gantry angulation. The calculations were performed using custom software written in IDL data visualization software (Exelis Visual Information Systems, Bolder, Colo) using input data from the fluoroscope machine logs.11 The machine log data provided technique factors for the RAK calculation and system geometry parameters, such as C arm orientation, magnification mode, collimation, and table height, for the estimation of skin dose maps corresponding to the posterior surface of a patient lying supine on the table pad. The calculations included several corrections factors.15 An RAK calibration correction obtained using National Institute of Standards and Technology traceable dosimetry equipment (Piranha T20; RTI Electronics, Mölndal, Sweden) was necessary because the U.S. Food and Drug Administration only requires 35% accuracy for the RAK display. A table and support attenuation correction factor was measured at typical operating parameters. Back scatter radiation correction was taken from published data.16 Translational table motion was not provided by the system logs but was predicted by adjusting the table position to keep the anatomy of interest in the center of the field of view. These software dose calculations and simulated dose maps have been previously validated against Gafchromic film (Ashland Inc, Covington, Ky) measurements.12 The combined skin dose effects were investigated for patients that had multiple FGIs in the hybrid operating room. Consistent with Joint Commission guidelines, doses from multiple procedures within a 6-month period were summed. Data from FGIs that might have been performed at outside hospitals or in other subspecialty units were not collected and therefore not included.
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Fig 2. Patient characteristics. DM, Diabetes mellitus.
RESULTS Of 317 FGIs performed in a single hybrid operating room room during a 7-month period, 21 FEVARs and one embolization exceeded an RAK of 5 Gy, meeting criteria for an SRDL. Because embolizations were not included in the new rigorous patient follow-up protocol, this procedure was excluded from the analysis. Therefore the 21 FEVARs formed the basis of the present analysis. The patient cohort was 91% male and had a mean body mass index of 30 kg/m2. Comorbidities and putative risk factors for skin injury included smoking (32%), diabetes (14%), white (non-Hispanic) ethnicity (91%), and concomitant chemotherapeutic agents (9%; Fig 2). No instances of other associated risk factors were found, including hyperthyroidism, collagen vascular disorders, Sjögren syndrome, ataxia, or telangiectasia. The average RAK for all FEVARs was 7.6 6 2.0 Gy (range, 5.1-11.4 Gy). Eleven (52%) of the patients had multiple FGIs #6 months of the SRDL event, which led to a mean cumulative RAK of 10.0 6 2.9 Gy (range, 5.5-15.1 Gy; Fig 3). The mean PSD for all FEVARs was 4.8 6 2.0 Gy (range, 2.3-10.4 Gy), and the dose index (PSD/RAK) was 0.69 6 0.19 (range, 0.41-1.15). The average PSD for the subset of patients with multiple procedures involving the same irradiated anatomy #6 months was 6.6 6 1.9 Gy (range, 3.4-9.4 Gy; Fig 4). Six patients received a PSD >5 Gy (Fig 5). All 21 FEVAR patients were examined at 1 or 2 weeks postoperatively, and 17 patients (81%) were examined at 1 month. Of those not seen, one patient had died and three patients missed the 1-month follow-up but were seen at 3 months. At 3 months, 11 patients (52%) were examined; of the nine patients not seen, five were lost to follow-up and four were seen at 6 months. At 6 months, 13 patients (62%) were examined, one additional patient was lost to follow-up and another had died. In total at 6 months, eight patients had died or were lost to follow-up. No radiation skin injuries were recorded in any patient, regardless of PSD. DISCUSSION Radiation-induced skin lesions are classified according to the time after exposure, beginning as soon as 24 hours and manifesting as late as 1 year after the event. The most frequently reported prompt reaction is transient
Fig 3. Distribution of reference air kerma (RAK) in the study population. The horizontal line in the middle of each box indicates the median; the top and bottom borders of the box mark the 75th and 25th percentiles, respectively, and the whiskers mark the 90th and 10th percentiles. FEVAR, Fenestrated endovascular aortic aneurysm.
erythema, which can occur at skin doses as low as 2 Gy.4,17 Early reactions include epilation, the main erythematous reaction, and moderate tissue edema seen at skin doses of 3 to 6 Gy. Early lesions associated with PSDs >10 Gy include dry or moist desquamation, dermal atrophy, necrosis, and ulceration.4 Late reactions include telangiectasia, further dermal thinning, and deeper ulceration.9 Most of the deterministic changes have occurred after coronary interventions or neuroembolizations. Reports of radiation-induced skin injury from endovascular procedures have been limited to case reports; there has been a notable lack of large series reviews. Our previous study represents the largest analysis of deterministic skin injury after complex endovascular procedures. In this work, the mean PSD was substantial and should have demonstrated some forms of skin injury; however, no injuries were detected.12 We predicted that a more comprehensive follow-up protocol of patients within the distribution of calculated PSDs seen in the present study would have yielded a spectrum of injury ranging from erythema to ulceration and necrosis. However, once again, no skin injuries were detected. Our results suggest that the development of deterministic skin injury is multifactorial, complex, and not solely reliant on the radiation dose. Certain patient factors are believed to modify the normal response of skin to radiation and thus predispose patients to injury after FGIs, yet we were unable to demonstrate an association in this study. Multiple risk factors for injury were present in our cohort, including diabetes mellitus, current smoking status, white skin, and concomitant chemotherapeutic agents, but no adverse reactions were found.6,9,18,19 However, an analysis of risk factor effect is beyond the scope of this study due to the small number of patients. We
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Fig 5. Estimated peak skin dose (PSD) according to the number of fenestrated endovascular aortic aneurysm repairs (FEVARs).
Fig 4. Distribution of the estimated peak skin dose (PSD) in the study population. The horizontal line in the middle of each box indicates the median; the top and bottom borders of the box mark the 75th and 25th percentiles, respectively, and the whiskers mark the 90th and 10th percentiles. FEVAR, Fenestrated endovascular aortic aneurysm.
acknowledge that other putative risk factors for radiationinduced skin injury, such as collagen vascular diseases (ie, scleroderma, systemic lupus erythematous) and mixed connective tissue disease, have all been thought to increase susceptibility to skin injury at lower doses; however, these were not present in our study patients.7,20 Similarly, no patients had hyperthyroidism, ataxia telangiectasia, xeroderma pigmentosum, poor nutritional status, or compromised preoperative skin integrity.21 Thus, the present results neither refute nor support the role of risk factors for deterministic skin injury. In recognition of the summative effects of radiation, the Joint Commission recommends that doses from previous procedures to the same body area over a 6-month to 12-month period be combined. A sentinel event occurs when this cumulative PSD is $15 Gy. In this study, we used a 6-month period as our time frame for inclusion of additional fluoroscopic procedures, in accordance with current NCRP recommendations.4,9,22 No skin injury was observed in the patient subset with multiple procedures, despite high summed PSDs. This is consistent with skin recovery and regeneration in the time interval between procedures. Therefore, our results suggest that summing PSD may overestimate the potential for skin injury. Keeping track of a patient’s cumulative radiation dose helps ensure that unnecessary radiologic tests and procedures are omitted and that the appropriate follow-up of highdose patients ensues. We acknowledge that it is good practice and may be required by state law. However, a history of substantial radiation dose should not prohibit the practitioner from performing appropriate and needed interventions, especially because cumulative procedures within a 6-month period do not appear to increase the risk for skin injury in patients undergoing FEVAR.
The PSD/RAK ratio or dose index enables the operator to roughly estimate the patient’s PSD after a procedure based on the displayed RAK. In our previous series, the dose index for FEVARs was calculated to be 0.78, meaning that the PSD received by the patient was w78% of the RAK displayed on the monitor. The dose index for FEVARs in the current work decreased to w69%. This suggests that the surgeons in our group have more appropriately and consistently used strategies to decrease radiation dose to the patient, namely use of collimation, table height elevation, and minimization of magnification modes. However, even when best operating practice is used, FEVARs often require high radiation doses to complete. Several study limitations must be acknowledged. First, because a reliable dose tracking system that is accessible in the inpatient and outpatient setting was not available at our institution, intensive follow-up for skin injury was performed on all FEVAR patients, regardless of dose received; therefore, some FEVAR patients with radiation doses <5 Gy may have received unnecessary serial skin examinations. Alternatively, patients who received high radiation doses during alternative procedures, such as embolizations, did not undergo the same rigorous follow-up. Therefore, our results apply only to FEVAR patients. Ideally, patients would be followed up based on the radiation dose received with a dose tracking system that was linked to the patient’s medical record to alert physician at each follow-up visit. Another limitation is that the number of patients in this study was relatively small, and the diversity of the study cohort was limited. Nevertheless, the study represents the largest series of patients followed up for skin injury after FEVAR yet reported. Most patients were white males; therefore, the results may not be applicable to women or to individuals of other ethnic backgrounds. Furthermore, there was a relative paucity of putative risk factors for deterministic skin injury. We acknowledge the possibility that a larger and more varied patient population might have demonstrated some deterministic effects. In addition, not all patients in this study were examined at the designated time intervals after FEVAR. All patients were, however, examined at 1 or 2 weeks, which should be the best time frame to detect early effects of skin injuries
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that may resolve or progress. Some of the patients were from out of state and had follow-up at other institutions. These patients were considered lost to follow-up from the study because there was no documentation of skin examinations. Some late effects might have occurred in some of these patients. However, given the constraints of the referral population, we are confident that we have been able to rule out early skin injuries in patients exposed to high radiation doses during FEVAR. Finally, only repeat procedures performed #6 months of the SRDL that occurred by our group in our hybrid operating room room were included in the multiple procedure cumulative group. Patients who underwent FGIs at other institutions or in other departments within our institution were not included. Therefore, it is possible that even higher doses of PSD existed in the multiple procedure group. Although skin injury was still not detected in this cohort, a proper evaluation of cumulative dose would need to consider all radiologic exposures within the given time interval. CONCLUSIONS The present study shows that deterministic skin injuries are uncommon after FEVAR, even at high RAK levels, regardless of cumulative dose effects. The study addresses the concerns regarding the retrospective clinical examination findings of our previous work. Even with more comprehensive postoperative skin examinations and patient questioning, no skin injuries were found in this small cohort. This suggests that radiation-induced skin injuries are multifactorial and not just simply dose dependent. A prospective, multi-institutional study is needed to quantify the risk of deterministic injury in patients undergoing FEVAR. AUTHOR CONTRIBUTIONS Conception and design: MK, JG, GA Analysis and interpretation: MK, JG, GA, JA Data collection: MK, CT Writing the article: MK, JG, GA Critical revision of the article: JA, RV Final approval of the article: MK, JG, GA, JA, RV, CT Statistical analysis: JG, GA Obtained funding: Not applicable Overall responsibility: MK REFERENCES 1. Brown KR, Rzucidlo E. Acute and chronic radiation injury. J Vasc Surg 2011;53:15-21S. 2. Koenig TR, Wolff D, Mettler FA, Wagner LK. Skin injuries from fluoroscopically guided procedures: part 1, characteristics of radiation injury. AJR Am J Roentgenol 2001;177:3-11.
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3. Koenig TR, Mettler FA, Wagner LK. Skin injuries from fluoroscopically guided procedures: part 2, review of 73 cases and recommendations for minimizing dose delivered to patient. AJR Am J Roentgenol 2001;177: 13-20. 4. NCRP. Radiation dose management for fluoroscopically guided interventional medical procedures, Report No. 168. Bethesda, MD: National Council on Radiation Protection and Measurements; 2010. 5. The Joint Commission. The Joint Commission Sentinel Event Alert, Issue 47: radiation risks of diagnostic imaging. August 2011. Available at: http://www.jointcommission.org/assets/1/18/SEA_47.pdf. Accessed September 16, 2014. 6. Mettler FA Jr, Koenig TR, Wagner LK, Kelsey CA. Radiation injuries after fluoroscopic procedures. Semin Ultrasound CT MR 2002;23: 428-42. 7. Vano E, Goicolea J, Galvan C, Gonzalez L, Meiggs L, Ten JI, et al. Skin radiation injuries in patients following repeated coronary angioplasty procedures. Br J Radiol 2001;74:1023-31. 8. Mooney RB, McKinstry CS, Kamel HA. Absorbed dose and deterministic effects to patients from interventional neuroradiology. Br J Radiol 2000;73:745-51. 9. Balter S, Hopewell JW, Miller DL, Wagner LK, Zelefsky MJ. Fluoroscopically guided interventional procedures: a review of radiation effects on patients’ skin and hair. Radiology 2010;254:326-41. 10. Vlietstra RE, Wagner LK, Koenig T, Mettler F. Radiation burns as a severe complication of fluoroscopically guided cardiological interventions. J Interv Cardiol 2004;17:131-42. 11. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Chung J, Anderson JA, et al. Surgeon education decreases radiation dose in complex endovascular procedures and improves patient safety. J Vasc Surg 2013;58:715-21. 12. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Valentine RJ, Anderson JA. Radiation-induced skin injury after complex endovascular procedures. J Vasc Surg 2014;60:742-8. 13. Walsh SR, Cousins C, Tang TY, Gaunt ME, Boyle JR. Ionizing radiation in endovascular interventions. J Endovasc Ther 2008;15:680-7. 14. Fletcher DW, Miller DL, Balter S, Taylor MA. Comparison of four techniques to estimate radiation dose to skin during angiographic and interventional radiology procedures. J Vasc Interv Radiol 2002;13: 391-7. 15. Arbique G, Guild J, Chason D, Anderson J. The fluoroscopic sentinel event: what to do? J Am Osteopath Coll Radiol 2014;3:8-20. 16. Petoussi-Henss N, Zankl M, Drexler G, Panzer W, Regulla D. Calculation of backscatter factors for diagnostic radiology using Monte Carlo methods. Phys Med Biol 1998;43:2237-50. 17. Kalef-Ezra JA, Karavasilis S, Ziogas D, Dristiliaris D, Michalis LK, Matsagas M. Radiation burden of patients undergoing endovascular abdominal aortic aneurysm repair. J Vasc Surg 2009;49:283-7; discussion: 287. 18. Mettler FA. Medical effects and risks of exposure to ionising radiation. J Radiol Prot 2012;32:N9-13. 19. Herold DM, Hanlon AL, Hanks GE. Diabetes mellitus: a predictor for late radiation morbidity. Int J Radiat Oncol Biol Phys 1999;43:475-9. 20. Wagner LK, McNeese MD, Marx MV, Siegel EL. Severe skin reactions from interventional fluoroscopy: case report and review of the literature. Radiology 1999;213:773-6. 21. Hymes SR, Strom EA, Fife C. Radiation dermatitis: clinical presentation, pathophysiology, and treatment 2006. J Am Acad Dermatol 2006;54:28-46. 22. Miller DL, Balter S, Schueler BA, Wagner LK, Strauss KJ, Vano E. Clinical radiation management for fluoroscopically guided interventional procedures. Radiology 2010;257:321-32. Submitted Sep 16, 2014; accepted Nov 10, 2014.
DISCUSSION Dr Brian G. DeRubertis (Los Angeles, Calif). I would like to congratulate Dr Kirkwood on an excellent presentation regarding a very important topic, and I thank you for providing me with the
manuscript well in advance of the meeting. I also would like to commend you, Carlos Timaran, and your group for being one of only a handful of centers in the country to approach fenestrated
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endovascular aneurysm repair under an investigational device exemption (IDE). After being involved in just a few of these cases, one can become easily convinced that the role of open surgery for thoracos should diminish rapidly. Unfortunately, commercially available solutions are probably a decade away, and investigator sponsored IDEs are the only way that I see to bridge the gap between then and now. This manuscript focuses on the deterministic effects of radiation, which are those that cause tissue damage in a dose dependent manner after a threshold of exposure has been reached. It focused on 21 patients, followed out to 6 months, and found no evidence of tissue injury despite relatively high radiation exposures. Dr Kirkwood’s manuscript is well written and will be an important addition to the sparse literature on this topic to date. I do, however, have the following questions: 1. First of all, 38% of patients either died or were lost to followup at the 6 month mark. I suspect the patients lost to followup were those that were referred great distances to see you. Since deterministic effects can first present up to one year following exposure, are you convince that the incidence of these events is in fact zero, and do you share your protocol for screening for these with your referring doctors so they can assist in this process? 2. What percent of all your fenestrated repairs exceed the 5Gy threshold? Is this a common problem, and did the likelihood of exceeding this threshold diminish as you navigated the relatively flat learning curve associated with fenestrated repairs? 3. Are there specific predictors of exceeding this threshold, such as BMI, 4-vessel fenestration cases (compared to 1 or 2), other such factors? 4. What is the impact of subsequent interventions.for those that require subsequent interventions, what percent of the total dose comes from those subsequent interventions? Again, congratulations on a nice presentation.
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Dr Melissa L. Kirkwood. To answer your questions: 1. The study follow-up was limited because patients who lived a long distance had routine follow-up with the outside referring physician. However, minor and serious skin injuries are expected to manifest early in the postoperative period. All patients were seen at 1 or 2 weeks and therefore we are confident that all early skin injuries would have been detected. Although it is possible that later injuries may have been missed, these injuries tend to be more severe and likely would have been detected by the patient or the following physician. We did not notify the referring physician to look for deterministic skin injury. This weakness in our study is an area of future improvement. 2. Thirty percent of FEVARs exceed an RAK of 5 Gy. The surgeons in this study were well trained in fenestrated repair and we do not believe that learning curves were a factor in radiation dose. 3. Patient body mass index is a strong factor in predicting radiation dose because higher radiation output is required to image larger patients compared to thinner patients for the same procedure. In our previous paper,1 the level of fenestration did not prove to predict higher radiation dose. We did not evaluate this parameter in the current study. 4. Of the 11 patients that had subsequent interventions, the additional RAK was 40% of the total cumulative RAK and the PSD increased by 60%
REFERENCE 1. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Valentine RJ, Anderson JA. Radiation-induced skin injury after complex endovascular procedures. J Vasc Surg 2014;60:742-8.
Deterministic effects after fenestrated endovascular aortic aneurysm repair Melissa L. Kirkwood, MD,a Gary M. Arbique, PhD,b Jeffrey B. Guild, PhD,b Carlos Timaran, MD,a Jon A. Anderson, PhD,b and R. James Valentine, MD,a Dallas, Tex Background: Endovascular aortic aneurysm repairs (EVARs) with fenestrated (FEVAR) stent grafts are high radiation dose cases, yet no skin injuries were found retrospectively in our 61 cases with a mean peak skin dose (PSD) of 6.8 Gy. We hypothesize that skin injury is under-reported. This study examined deterministic effects in FEVARs after procedural changes implemented to detect skin injury. Methods: All FEVARs during a 6-month period with a radiation dose of 5 Gy reference air kerma (RAK; National Council on Radiation Protection and Measurements threshold for substantial radiation dose level [SRDL]) were included. Patients were questioned about skin erythema, epilation, and necrosis, with a physical examination of the back completed daily until discharge and then at 2 and 4 weeks and at 3 and 6 months. PSD distributions were calculated with custom software using input data from fluoroscopic machine logs. These calculations have been validated against Gafchromic (Ashland Inc, Covington, Ky) film measurements. Dose was summed for the subset of patients with multiple procedures #6 months of the SRDL event, consistent with the joint commission recommendations. Results: Twenty-two patients, 21 FEVARs and one embolization, reached an RAK of 5 Gy. The embolization procedure was excluded from review. The average RAK was 7.6 6 2.0 Gy (range, 5.1-11.4 Gy), with a mean PSD of 4.8 6 2.0 Gy (range, 2.3-10.4 Gy). Fifty-two percent of patients had multiple endovascular procedures #6 months of the SRDL event. The mean RAK for this subset was 10.0 6 2.9 Gy (range, 5.5-15.1 Gy), with a mean PSD of 6.6 6 1.9 Gy (range, 3.4-9.4 Gy). One patient died before the first postoperative visit. No radiation skin injuries were found. Putative risk factors for skin injury were evaluated and included smoking (32%), diabetes (14%), cytotoxic drugs (9%), and fair skin type (91%). No other risk factors were present (hyperthyroidism, collagen vascular disorders). Conclusions: Deterministic skin injuries are uncommon after FEVAR, even at high RAK levels, regardless of cumulative dose effects. This study addresses the concern of missed injuries based on the retrospective clinical examination findings that were published in our previous work. Even with more comprehensive postoperative skin examinations and patient questioning, the fact that no skin injuries were found suggests that radiation-induced skin injuries are multifactorial and not solely dose dependent. (J Vasc Surg 2015;61:902-7.)
Deterministic skin injury is a biologic effect resulting from excessive radiation exposure. These effects are associated with a threshold radiation dose above which the severity of injury increases with increasing delivered dose.1 The most common deterministic effects are skin and eye injuries, which are infrequent but serious potential complications of fluoroscopically guided interventions (FGIs).2,3 The National Council on Radiation Protection and Measurements (NCRP) has defined a substantial
From the Division of Vascular and Endovascular Surgery, Department of Surgery,a and the Division of Medical Physics, Department of Radiology,b UT Southwestern Medical Center. Author conflict of interest: none. Presented at the Twenty-ninth Annual Meeting of the Western Vascular Society, Coronado, Calif, September 20-23, 2014. Reprint requests: Melissa L. Kirkwood, MD, UT Southwestern Medical Center, Professional Office Bldg 1, Ste 620, 5959 Harry Hines Blvd, Dallas, TX 75390-9157 (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2015 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2014.11.044
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radiation dose level (SRDL) to be a reference air kerma (RAK) of $5 Gy. This dose threshold is intended to trigger patient follow-up directed at detecting skin effects that may require further management.4 In addition, the Joint Commission’s recognition of skin doses >15 Gy as a reviewable sentinel event has led to increased awareness of patient skin injury during FGIs.5 Reports of deterministic skin injury are mostly limited to case reports after coronary interventions, neuroembolizations, and transjugular intrahepatic portosystemic shunt procedures.6-10 Fenestrated endovascular aortic aneurysm repair (FEVAR) is a complex procedure that requires consistently high radiation doses to complete; yet, the prevalence of deterministic skin injuries after FEVAR remains unknown.11 Our previous work retrospectively reviewed 61 complex endovascular procedures that met or exceeded SRDL dose criteria. Despite mean peak skin doses (PSDs) >6.5 Gy, with a range extending to 18 Gy, no skin injuries were found. This study was limited by its retrospective design, with no formal protocol in place to ensure that a thorough skin examination of each patient’s back was performed at every postoperative visit, nor was there a protocol established for direct patient questioning regarding skin
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Fig 1. Reference air kerma (RAK). IRP, Interventional reference point.
complaints. Although severe skin ulceration or necrosis would likely have been detected, it is reasonable to assume that minor skin injuries could have been missed.12 We hypothesized that a more thorough postoperative follow-up of patients would detect skin injury and address the deficiencies of our previous work. This study sought to examine the frequency and severity of deterministic effects and to evaluate patient characteristics that might predispose to radiation injury after FEVAR. METHODS This study was approved by the UT Southwestern Medical Center Institutional Review Board. Patient consent was waived due to the retrospective nature of the study. This study used the RAK as the dose metric because no real-time PSD meter is currently available during a procedure. The RAK is a measure of the radiation dose to air at a reference point that roughly correlates with the patient’s skin and offers the best estimate of patient skin dose during a procedure.4,13,14 On interventional fluoroscopes featuring isocentric gantries, this reference point is called the interventional reference point and is 15 cm toward the X-ray focal spot from isocenter (Fig 1). A new policy was implemented at the UT Southwestern Medical Center Division of Vascular Surgery for follow-up of FEVAR patients beginning in June 2013. At every postoperative FEVAR visit, the operating surgeon or vascular nurse practioner performed a full skin examination of the patient’s back and buttock region. In addition, FEVAR patients were questioned about any skin-related
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complaints, including erythema, epilation, necrosis, or ulceration. The physical examination findings and the patient questionnaire were documented in the medical record. All patients undergoing an FGI in an Allura Xper FD20 hybrid room (Phillips Health Care, Andover, Mass) from June 1, 2013, to December 31, 2013, were initially included. Radiation dose and machine operating factors were recorded for each procedure. The FGIs that required at $5 Gy RAK were identified. The outpatient and inpatient medical records of all patients meeting SRDL dose criteria at our institution were retrospectively reviewed specifically for evidence of skin injury. Patient comorbidities that might predispose to skin injury (ie, collagen vascular disorders, hyperthyroidism, diabetes, ethnicity, and smoking status) were recorded. Patients were examined daily in the hospital until discharge, at 2 and 4 weeks, and at 3 and 6 months. PSD distributions were calculated for all FGIs with $5 Gy RAK, and a dose index (PSD/RAK ratio)14 was determined for each case. These calculations were performed because combining PSD calculations based on RAK and machine geometry results in a better estimate of skin dose compared with RAK alone. RAK is defined relative to the X-ray source and not the patient; therefore, RAK does not account for changes in table position or gantry angulation. The calculations were performed using custom software written in IDL data visualization software (Exelis Visual Information Systems, Bolder, Colo) using input data from the fluoroscope machine logs.11 The machine log data provided technique factors for the RAK calculation and system geometry parameters, such as C arm orientation, magnification mode, collimation, and table height, for the estimation of skin dose maps corresponding to the posterior surface of a patient lying supine on the table pad. The calculations included several corrections factors.15 An RAK calibration correction obtained using National Institute of Standards and Technology traceable dosimetry equipment (Piranha T20; RTI Electronics, Mölndal, Sweden) was necessary because the U.S. Food and Drug Administration only requires 35% accuracy for the RAK display. A table and support attenuation correction factor was measured at typical operating parameters. Back scatter radiation correction was taken from published data.16 Translational table motion was not provided by the system logs but was predicted by adjusting the table position to keep the anatomy of interest in the center of the field of view. These software dose calculations and simulated dose maps have been previously validated against Gafchromic film (Ashland Inc, Covington, Ky) measurements.12 The combined skin dose effects were investigated for patients that had multiple FGIs in the hybrid operating room. Consistent with Joint Commission guidelines, doses from multiple procedures within a 6-month period were summed. Data from FGIs that might have been performed at outside hospitals or in other subspecialty units were not collected and therefore not included.
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Fig 2. Patient characteristics. DM, Diabetes mellitus.
RESULTS Of 317 FGIs performed in a single hybrid operating room room during a 7-month period, 21 FEVARs and one embolization exceeded an RAK of 5 Gy, meeting criteria for an SRDL. Because embolizations were not included in the new rigorous patient follow-up protocol, this procedure was excluded from the analysis. Therefore the 21 FEVARs formed the basis of the present analysis. The patient cohort was 91% male and had a mean body mass index of 30 kg/m2. Comorbidities and putative risk factors for skin injury included smoking (32%), diabetes (14%), white (non-Hispanic) ethnicity (91%), and concomitant chemotherapeutic agents (9%; Fig 2). No instances of other associated risk factors were found, including hyperthyroidism, collagen vascular disorders, Sjögren syndrome, ataxia, or telangiectasia. The average RAK for all FEVARs was 7.6 6 2.0 Gy (range, 5.1-11.4 Gy). Eleven (52%) of the patients had multiple FGIs #6 months of the SRDL event, which led to a mean cumulative RAK of 10.0 6 2.9 Gy (range, 5.5-15.1 Gy; Fig 3). The mean PSD for all FEVARs was 4.8 6 2.0 Gy (range, 2.3-10.4 Gy), and the dose index (PSD/RAK) was 0.69 6 0.19 (range, 0.41-1.15). The average PSD for the subset of patients with multiple procedures involving the same irradiated anatomy #6 months was 6.6 6 1.9 Gy (range, 3.4-9.4 Gy; Fig 4). Six patients received a PSD >5 Gy (Fig 5). All 21 FEVAR patients were examined at 1 or 2 weeks postoperatively, and 17 patients (81%) were examined at 1 month. Of those not seen, one patient had died and three patients missed the 1-month follow-up but were seen at 3 months. At 3 months, 11 patients (52%) were examined; of the nine patients not seen, five were lost to follow-up and four were seen at 6 months. At 6 months, 13 patients (62%) were examined, one additional patient was lost to follow-up and another had died. In total at 6 months, eight patients had died or were lost to follow-up. No radiation skin injuries were recorded in any patient, regardless of PSD. DISCUSSION Radiation-induced skin lesions are classified according to the time after exposure, beginning as soon as 24 hours and manifesting as late as 1 year after the event. The most frequently reported prompt reaction is transient
Fig 3. Distribution of reference air kerma (RAK) in the study population. The horizontal line in the middle of each box indicates the median; the top and bottom borders of the box mark the 75th and 25th percentiles, respectively, and the whiskers mark the 90th and 10th percentiles. FEVAR, Fenestrated endovascular aortic aneurysm.
erythema, which can occur at skin doses as low as 2 Gy.4,17 Early reactions include epilation, the main erythematous reaction, and moderate tissue edema seen at skin doses of 3 to 6 Gy. Early lesions associated with PSDs >10 Gy include dry or moist desquamation, dermal atrophy, necrosis, and ulceration.4 Late reactions include telangiectasia, further dermal thinning, and deeper ulceration.9 Most of the deterministic changes have occurred after coronary interventions or neuroembolizations. Reports of radiation-induced skin injury from endovascular procedures have been limited to case reports; there has been a notable lack of large series reviews. Our previous study represents the largest analysis of deterministic skin injury after complex endovascular procedures. In this work, the mean PSD was substantial and should have demonstrated some forms of skin injury; however, no injuries were detected.12 We predicted that a more comprehensive follow-up protocol of patients within the distribution of calculated PSDs seen in the present study would have yielded a spectrum of injury ranging from erythema to ulceration and necrosis. However, once again, no skin injuries were detected. Our results suggest that the development of deterministic skin injury is multifactorial, complex, and not solely reliant on the radiation dose. Certain patient factors are believed to modify the normal response of skin to radiation and thus predispose patients to injury after FGIs, yet we were unable to demonstrate an association in this study. Multiple risk factors for injury were present in our cohort, including diabetes mellitus, current smoking status, white skin, and concomitant chemotherapeutic agents, but no adverse reactions were found.6,9,18,19 However, an analysis of risk factor effect is beyond the scope of this study due to the small number of patients. We
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Fig 5. Estimated peak skin dose (PSD) according to the number of fenestrated endovascular aortic aneurysm repairs (FEVARs).
Fig 4. Distribution of the estimated peak skin dose (PSD) in the study population. The horizontal line in the middle of each box indicates the median; the top and bottom borders of the box mark the 75th and 25th percentiles, respectively, and the whiskers mark the 90th and 10th percentiles. FEVAR, Fenestrated endovascular aortic aneurysm.
acknowledge that other putative risk factors for radiationinduced skin injury, such as collagen vascular diseases (ie, scleroderma, systemic lupus erythematous) and mixed connective tissue disease, have all been thought to increase susceptibility to skin injury at lower doses; however, these were not present in our study patients.7,20 Similarly, no patients had hyperthyroidism, ataxia telangiectasia, xeroderma pigmentosum, poor nutritional status, or compromised preoperative skin integrity.21 Thus, the present results neither refute nor support the role of risk factors for deterministic skin injury. In recognition of the summative effects of radiation, the Joint Commission recommends that doses from previous procedures to the same body area over a 6-month to 12-month period be combined. A sentinel event occurs when this cumulative PSD is $15 Gy. In this study, we used a 6-month period as our time frame for inclusion of additional fluoroscopic procedures, in accordance with current NCRP recommendations.4,9,22 No skin injury was observed in the patient subset with multiple procedures, despite high summed PSDs. This is consistent with skin recovery and regeneration in the time interval between procedures. Therefore, our results suggest that summing PSD may overestimate the potential for skin injury. Keeping track of a patient’s cumulative radiation dose helps ensure that unnecessary radiologic tests and procedures are omitted and that the appropriate follow-up of highdose patients ensues. We acknowledge that it is good practice and may be required by state law. However, a history of substantial radiation dose should not prohibit the practitioner from performing appropriate and needed interventions, especially because cumulative procedures within a 6-month period do not appear to increase the risk for skin injury in patients undergoing FEVAR.
The PSD/RAK ratio or dose index enables the operator to roughly estimate the patient’s PSD after a procedure based on the displayed RAK. In our previous series, the dose index for FEVARs was calculated to be 0.78, meaning that the PSD received by the patient was w78% of the RAK displayed on the monitor. The dose index for FEVARs in the current work decreased to w69%. This suggests that the surgeons in our group have more appropriately and consistently used strategies to decrease radiation dose to the patient, namely use of collimation, table height elevation, and minimization of magnification modes. However, even when best operating practice is used, FEVARs often require high radiation doses to complete. Several study limitations must be acknowledged. First, because a reliable dose tracking system that is accessible in the inpatient and outpatient setting was not available at our institution, intensive follow-up for skin injury was performed on all FEVAR patients, regardless of dose received; therefore, some FEVAR patients with radiation doses <5 Gy may have received unnecessary serial skin examinations. Alternatively, patients who received high radiation doses during alternative procedures, such as embolizations, did not undergo the same rigorous follow-up. Therefore, our results apply only to FEVAR patients. Ideally, patients would be followed up based on the radiation dose received with a dose tracking system that was linked to the patient’s medical record to alert physician at each follow-up visit. Another limitation is that the number of patients in this study was relatively small, and the diversity of the study cohort was limited. Nevertheless, the study represents the largest series of patients followed up for skin injury after FEVAR yet reported. Most patients were white males; therefore, the results may not be applicable to women or to individuals of other ethnic backgrounds. Furthermore, there was a relative paucity of putative risk factors for deterministic skin injury. We acknowledge the possibility that a larger and more varied patient population might have demonstrated some deterministic effects. In addition, not all patients in this study were examined at the designated time intervals after FEVAR. All patients were, however, examined at 1 or 2 weeks, which should be the best time frame to detect early effects of skin injuries
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that may resolve or progress. Some of the patients were from out of state and had follow-up at other institutions. These patients were considered lost to follow-up from the study because there was no documentation of skin examinations. Some late effects might have occurred in some of these patients. However, given the constraints of the referral population, we are confident that we have been able to rule out early skin injuries in patients exposed to high radiation doses during FEVAR. Finally, only repeat procedures performed #6 months of the SRDL that occurred by our group in our hybrid operating room room were included in the multiple procedure cumulative group. Patients who underwent FGIs at other institutions or in other departments within our institution were not included. Therefore, it is possible that even higher doses of PSD existed in the multiple procedure group. Although skin injury was still not detected in this cohort, a proper evaluation of cumulative dose would need to consider all radiologic exposures within the given time interval. CONCLUSIONS The present study shows that deterministic skin injuries are uncommon after FEVAR, even at high RAK levels, regardless of cumulative dose effects. The study addresses the concerns regarding the retrospective clinical examination findings of our previous work. Even with more comprehensive postoperative skin examinations and patient questioning, no skin injuries were found in this small cohort. This suggests that radiation-induced skin injuries are multifactorial and not just simply dose dependent. A prospective, multi-institutional study is needed to quantify the risk of deterministic injury in patients undergoing FEVAR. AUTHOR CONTRIBUTIONS Conception and design: MK, JG, GA Analysis and interpretation: MK, JG, GA, JA Data collection: MK, CT Writing the article: MK, JG, GA Critical revision of the article: JA, RV Final approval of the article: MK, JG, GA, JA, RV, CT Statistical analysis: JG, GA Obtained funding: Not applicable Overall responsibility: MK REFERENCES 1. Brown KR, Rzucidlo E. Acute and chronic radiation injury. J Vasc Surg 2011;53:15-21S. 2. Koenig TR, Wolff D, Mettler FA, Wagner LK. Skin injuries from fluoroscopically guided procedures: part 1, characteristics of radiation injury. AJR Am J Roentgenol 2001;177:3-11.
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3. Koenig TR, Mettler FA, Wagner LK. Skin injuries from fluoroscopically guided procedures: part 2, review of 73 cases and recommendations for minimizing dose delivered to patient. AJR Am J Roentgenol 2001;177: 13-20. 4. NCRP. Radiation dose management for fluoroscopically guided interventional medical procedures, Report No. 168. Bethesda, MD: National Council on Radiation Protection and Measurements; 2010. 5. The Joint Commission. The Joint Commission Sentinel Event Alert, Issue 47: radiation risks of diagnostic imaging. August 2011. Available at: http://www.jointcommission.org/assets/1/18/SEA_47.pdf. Accessed September 16, 2014. 6. Mettler FA Jr, Koenig TR, Wagner LK, Kelsey CA. Radiation injuries after fluoroscopic procedures. Semin Ultrasound CT MR 2002;23: 428-42. 7. Vano E, Goicolea J, Galvan C, Gonzalez L, Meiggs L, Ten JI, et al. Skin radiation injuries in patients following repeated coronary angioplasty procedures. Br J Radiol 2001;74:1023-31. 8. Mooney RB, McKinstry CS, Kamel HA. Absorbed dose and deterministic effects to patients from interventional neuroradiology. Br J Radiol 2000;73:745-51. 9. Balter S, Hopewell JW, Miller DL, Wagner LK, Zelefsky MJ. Fluoroscopically guided interventional procedures: a review of radiation effects on patients’ skin and hair. Radiology 2010;254:326-41. 10. Vlietstra RE, Wagner LK, Koenig T, Mettler F. Radiation burns as a severe complication of fluoroscopically guided cardiological interventions. J Interv Cardiol 2004;17:131-42. 11. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Chung J, Anderson JA, et al. Surgeon education decreases radiation dose in complex endovascular procedures and improves patient safety. J Vasc Surg 2013;58:715-21. 12. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Valentine RJ, Anderson JA. Radiation-induced skin injury after complex endovascular procedures. J Vasc Surg 2014;60:742-8. 13. Walsh SR, Cousins C, Tang TY, Gaunt ME, Boyle JR. Ionizing radiation in endovascular interventions. J Endovasc Ther 2008;15:680-7. 14. Fletcher DW, Miller DL, Balter S, Taylor MA. Comparison of four techniques to estimate radiation dose to skin during angiographic and interventional radiology procedures. J Vasc Interv Radiol 2002;13: 391-7. 15. Arbique G, Guild J, Chason D, Anderson J. The fluoroscopic sentinel event: what to do? J Am Osteopath Coll Radiol 2014;3:8-20. 16. Petoussi-Henss N, Zankl M, Drexler G, Panzer W, Regulla D. Calculation of backscatter factors for diagnostic radiology using Monte Carlo methods. Phys Med Biol 1998;43:2237-50. 17. Kalef-Ezra JA, Karavasilis S, Ziogas D, Dristiliaris D, Michalis LK, Matsagas M. Radiation burden of patients undergoing endovascular abdominal aortic aneurysm repair. J Vasc Surg 2009;49:283-7; discussion: 287. 18. Mettler FA. Medical effects and risks of exposure to ionising radiation. J Radiol Prot 2012;32:N9-13. 19. Herold DM, Hanlon AL, Hanks GE. Diabetes mellitus: a predictor for late radiation morbidity. Int J Radiat Oncol Biol Phys 1999;43:475-9. 20. Wagner LK, McNeese MD, Marx MV, Siegel EL. Severe skin reactions from interventional fluoroscopy: case report and review of the literature. Radiology 1999;213:773-6. 21. Hymes SR, Strom EA, Fife C. Radiation dermatitis: clinical presentation, pathophysiology, and treatment 2006. J Am Acad Dermatol 2006;54:28-46. 22. Miller DL, Balter S, Schueler BA, Wagner LK, Strauss KJ, Vano E. Clinical radiation management for fluoroscopically guided interventional procedures. Radiology 2010;257:321-32. Submitted Sep 16, 2014; accepted Nov 10, 2014.
DISCUSSION Dr Brian G. DeRubertis (Los Angeles, Calif). I would like to congratulate Dr Kirkwood on an excellent presentation regarding a very important topic, and I thank you for providing me with the
manuscript well in advance of the meeting. I also would like to commend you, Carlos Timaran, and your group for being one of only a handful of centers in the country to approach fenestrated
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endovascular aneurysm repair under an investigational device exemption (IDE). After being involved in just a few of these cases, one can become easily convinced that the role of open surgery for thoracos should diminish rapidly. Unfortunately, commercially available solutions are probably a decade away, and investigator sponsored IDEs are the only way that I see to bridge the gap between then and now. This manuscript focuses on the deterministic effects of radiation, which are those that cause tissue damage in a dose dependent manner after a threshold of exposure has been reached. It focused on 21 patients, followed out to 6 months, and found no evidence of tissue injury despite relatively high radiation exposures. Dr Kirkwood’s manuscript is well written and will be an important addition to the sparse literature on this topic to date. I do, however, have the following questions: 1. First of all, 38% of patients either died or were lost to followup at the 6 month mark. I suspect the patients lost to followup were those that were referred great distances to see you. Since deterministic effects can first present up to one year following exposure, are you convince that the incidence of these events is in fact zero, and do you share your protocol for screening for these with your referring doctors so they can assist in this process? 2. What percent of all your fenestrated repairs exceed the 5Gy threshold? Is this a common problem, and did the likelihood of exceeding this threshold diminish as you navigated the relatively flat learning curve associated with fenestrated repairs? 3. Are there specific predictors of exceeding this threshold, such as BMI, 4-vessel fenestration cases (compared to 1 or 2), other such factors? 4. What is the impact of subsequent interventions.for those that require subsequent interventions, what percent of the total dose comes from those subsequent interventions? Again, congratulations on a nice presentation.
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Dr Melissa L. Kirkwood. To answer your questions: 1. The study follow-up was limited because patients who lived a long distance had routine follow-up with the outside referring physician. However, minor and serious skin injuries are expected to manifest early in the postoperative period. All patients were seen at 1 or 2 weeks and therefore we are confident that all early skin injuries would have been detected. Although it is possible that later injuries may have been missed, these injuries tend to be more severe and likely would have been detected by the patient or the following physician. We did not notify the referring physician to look for deterministic skin injury. This weakness in our study is an area of future improvement. 2. Thirty percent of FEVARs exceed an RAK of 5 Gy. The surgeons in this study were well trained in fenestrated repair and we do not believe that learning curves were a factor in radiation dose. 3. Patient body mass index is a strong factor in predicting radiation dose because higher radiation output is required to image larger patients compared to thinner patients for the same procedure. In our previous paper,1 the level of fenestration did not prove to predict higher radiation dose. We did not evaluate this parameter in the current study. 4. Of the 11 patients that had subsequent interventions, the additional RAK was 40% of the total cumulative RAK and the PSD increased by 60%
REFERENCE 1. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Valentine RJ, Anderson JA. Radiation-induced skin injury after complex endovascular procedures. J Vasc Surg 2014;60:742-8.