The impact of radiation dose exposure duringendovascular aneurysm repair on patient safetyClaire Jones, MB BCh, MRCS, Stephen A. Badger, MD, MRCS, Christopher S. Boyd, MD, FRCR, andChee V. Soong, MD, FRCS, Belfast, Ireland

Objective: Endovascular aneurysm repair (EVAR) exposes patients to radiation during the procedure and in subsequentfollow-up. The study goal was to calculate the radiation dose in our unit and compare it against other published data andnational guidelines.Methods: All EVAR procedures were identified from a prospectively maintained database. Radiation dose, screening time,and volume of intravenous contrast during the procedure were reviewed. Radiation exposure from subsequent computedtomography (CT) imaging was included in the overall exposure. Results are expressed as mean � standard deviation.Results: From October 1998 to October 2008, 320 elective patients underwent EVAR. Mean screening time was 29.4 �23.3 minutes, and the radiation dose was 11.7 � 7.1 mSv. The EVAR was an emergency in 64 patients. The meanscreening time was 22.9 � 18.2 minutes, and the radiation dose was 13.4 � 8.6 mSv. During the first postoperative year,follow-up CT scans exposed the patients to 24.0 mSv, with 8.0 mSv in subsequent years. Abdominal radiographs addedan additional 1.8 mSv each year.Conclusion: EVAR and the follow-up investigations involve substantial amounts of radiation, with well-recognizedcarcinogenic risks. Because patient safety is paramount, radiation exposure should be minimized. This may be possible bystandardizing radiation exposure throughout the United Kingdom by implementing national guidelines and considering

other imaging modalities for follow-up. (J Vasc Surg 2010;52:298-302.)

Vascular surgery has evolved significantly in recentyears with the introduction of endovascular procedures.Endovascular aortic aneurysm repair (EVAR) was first re-ported in 1991 and has now become an integral part ofvascular surgery as an established less invasive treatmentoption for the repair of abdominal aortic aneurysms(AAA).1-4 The benefits to the patient are apparent, with atwo-thirds reduction in 30-day operative mortality. Otherbenefits include a reduction in perioperative blood loss,shorter procedure time, less time spent in the intensive areunit postoperatively, and an overall shorter hospital lengthof stay.2-4

The use of fluoroscopy is common in endovascularprocedures, which therefore raises the issue of patient ex-posure to potentially harmful radiation. To minimize intra-operative radiation exposure, some units practice intravas-cular ultrasound imaging, without angiography, reportingsimilar outcomes to those exposed to angiography.5 Most,however, regard ultrasound imaging as an adjuvant toensure direct apposition of the stent graft to the proximallanding zone rather than as a sole imaging modality.

The short-term adverse effects of radiation exposureinclude skin erythema, cataracts, permanent epilation, anddelayed skin necrosis, whereas the long-term risks may

From the Vascular and Endovascular Surgery Unit, Belfast City Hospital.Competition of interest: none.Reprint requests: Claire Jones, Specialist Surgical Trainee, Belfast City

Hospital, Lisburn Rd, Belfast, BT9 7AB Ireland (e-mail: cjones82@hotmail.co.uk).

The editors and reviewers of this article have no relevant financial relationshipsto disclose per the JVS policy that requires reviewers to decline review of anymanuscript for which they may have a competition of interest.

0741-5214/$36.00Copyright © 2010 Published by Elsevier Inc. on behalf of the Society for

Vascular Surgery.

doi:10.1016/j.jvs.2010.03.004

298

include cancer of the thyroid, central nervous system, skin,and breast.6-9 Although radiologic imaging is essential forEVAR, the radiation exposure should be limited, particu-larly in view of the carcinogenic potential, to a lifetimecumulative total of 400 mSv. A recent study found a13-fold variation between the highest and lowest effectiveradiation dose for the same imaging technique within andacross institutions, highlighting the variation of radiationexposure and the need for standardization.10

EVAR can be performed in a dedicated angiographicsuite, where the images may be better, or more commonlyin an operating theater using a portable C-arm imageintensifier. Although the difference in radiation dose be-tween the two systems is not significant, the latter tends toproduce a less focused beam, with wider scatter of x-rays.Individual patients do not suffer, but the endovascular teammay be at higher risk.

The goal of this study was to determine radiationexposure to the patient while undergoing an EVAR bymeasuring the radiation effective dose and screening timefor each procedure, and also in the follow-up period, andthen to compare the standards of our unit with otherpublished data to ensure patient safety is not being com-promised.

METHODS

Patients. All patients who had undergone EVAR inthe Belfast City Hospital for an AAA were retrospectivelyidentified. Elective patients had an AAA with a maximumdiameter of �55 mm. Patients undergoing emergencyEVAR were similar but with radiologic evidence of leak orrupture. The endovascular database, theatre logs, and therecords of the endovascular suite were used to capture all

patients who underwent EVAR.

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All patients who underwent EVAR had been scannedby computed tomography (CT) to ensure appropriate se-lection of anatomically suitable aneurysms based on widelyaccepted anatomic criteria.11 Although angiography mayhave been performed after CT, it was not used as themodality for EVAR planning or patient selection.12 Thetotal number of aneurysm repairs increased in our unitduring the study, and the proportion undergoing EVARincreased from 22% in 1999 to 53% in 2008. Customizedbifurcated stent grafts from a variety of different manufac-turers were deployed in elective patients under radiologicguidance. The data recorded included:

● the screening time, which is the time duration of theprocedure;

● the radiation dose, which measures the dose of radia-tion that strikes the x-ray film behind the patient andturns the x-ray system off when the predetermineddose for that screen-film combination has beenreached; and

● the volume of intravenous contrast required.

From this was calculated the effective radiation dose, whichexpresses the dose and the volume of tissue irradiated, andtherefore the amount of radiation the patient absorbs.

All emergency patients underwent preoperative CTconfirmation of AAA with intravenous contrast extravasa-tion. Those who had a symptomatic AAA with no extrava-sation were included in the elective group of this study. Inemergency patients a uniiliac aortic stent graft was deployedwith contralateral iliac occlusion. This was usually per-formed under local anaesthetic, but to achieve hemody-namic control by aneurysm exclusion, the subsequentfemorofemoral crossover graft was performed under a briefgeneral anesthetic. The placement of a contralateral occlu-sive device is usually rapid and requires only one angio-graphic run, thus only increasing the radiation doseslightly. Similar radiation data were also recorded for thesepatients.

Nearly all emergency and most elective procedureswere performed in an operating theater and a portableC-arm was used, although some elective cases in the initialyears were performed in the angiography suite. There wasno update in the equipment during the study period.

The details of the surgical procedures have been de-scribed before.13,14 Patients who had moderate renal dys-function were given intravenous fluids before EVAR orfollow-up CT. Those with severe dysfunction were givenN-acetylcysteine in addition to fluid. There was no differ-ence in operative strategy.

Data collection and analysis. The radiation data of allprimary elective and emergency procedures were collectedand compiled in Excel (Microsoft Corp, Redmond, Wash).Secondary interventions directly related to the EVAR werealso identified and included in the database. All patientsroutinely had a CT preoperatively and then during postop-erative follow-up at 1, 3, and 12 months and annuallythereafter, according to the protocol of the EVAR trials.2,3

Annual abdominal x-ray (AXR) imaging was performed

with anteroposterior and 45° oblique projections to lookfor structural integrity or component separation. AlthoughAAA patients often have other cardiovascular diseases, theradiation exposure during coronary and peripheral vascularprocedures was not included because it was not within theremit of the study.

The average and distribution of the angiographicscreening time in minutes, radiation dose (Gycm2), andintravenous contrast volume (mL) were expressed in meanand standard deviation. The radiation dose was routinelyrecorded in Gycm.2 However, this was converted to aneffective dose equivalent (mSv) that was used to compareradiation doses on different body parts on an equivalentbasis using the conversion factor of 0.25 mSv/Gycm,2 asdemonstrated in previous guidelines.15 The radiation doseaffecting the radiologist and surgeon was not assessed inthis study because routine use of radiation counters wouldbe required, preferably in a prospective study.

The radiation exposure of an average CT was taken tobe 500 mGycm, or by using the multiplication conversionfactor of 0.015 mSv/mGycm, the effective dose was as-sumed to be 8.0 mSv. Two abdominal radiographs exposedthe patient to 6.0 mGy each, which using a conversionfactor of 0.15 mSv/mGy gave a total effective dose of 1.8mSv.15-17 The radiation dose per CT and AXR were incor-porated into the calculations of total radiation exposure.

A 4-slice CT scanner was initially used in our unit,whereas in latter years, a 16-slice scanner was used. This wasnot considered to be a source of variability because thefaster, modern multislice scanners may actually result inlower radiation owing to the decreased overlapping pen-umbral radiation zones.18 Although the figures used in thisstudy may not be accurate for every type of CT scanner,depending upon make and age, they were used to allow awider application of the results beyond our own unit andcan be modified according to local scanners.

The conversion of all measurements to mSv allowedcumulative calculations to be made. Although no specificguidelines are available for EVAR radiation exposure, theresults of the study were compared with other similarstudies in the published literature and general guidelines forradiation exposure.

RESULTS

Elective EVAR patients. Between October 1, 1998,and October 31, 2008, 320 patients (270 men, 50 women)underwent a primary EVAR. Their average age was 75.3 �7.0 years. A variety of stent grafts were used, including Ana-conda (Sulzer Vascutech, Bad Soden, Germany) in 3, Anson(Lombard Medical Technologies, Didcot, UK) in 12, Aorfix(Lombard) in 5, Cook (Cook, Bloomington, Ind) in 49,Endurant (Medtronic, Minneapolis, Minn) in 6, Gore (W. L.Gore and Assoc, Flagstaff, Ariz) in 3, and Vanguard (BostonScientific Corp, Natick Mass) in 3. A Talent (Medtronic,Sunnyvale, Calif) stent graft was used in the remaining pa-tients. In 30 patients, a balloon-expandable Palmaz (Cordis,Miami Lakes, Fla) stent graft was required in addition to

the primary stent graft during the initial repair.

JOURNAL OF VASCULAR SURGERYAugust 2010300 Jones et al

The mean screening time for this cohort was 29.4 �23.3 minutes, and the radiation dose was 46.9 � 28.4Gycm.2 The effective dose was calculated as 11.7 � 7.1 mSv(range, 0.3-51.2 mSv). During the procedures, 163.9 � 67.7mL of intravenous contrast was required. The correlationsbetween the screening time and radiation dose (r � 0.46,P � .0001) and contrast volume (r � 0.45, P � .0001),although statistically significant, were only moderate. Thecorrelation between radiation dose and contrast volumewas similar (r � 0.42, P � .00001). The effective dose ofpreoperative CT, EVAR, and postoperative surveillance forthe first year was a mean total of 45.5 mSv.

An additional 25 secondary procedures were requiredin a subgroup of 22 patients. The rate of secondary proce-dures declined with time. The indication was an endoleak in14 and stent graft migration in 11. This added another 24.0 �21.3 minutes of screening time, 31.8 � 29.7 Gycm2 ofradiation (7.9 � 7.4 mSV), and 10.3 � 5.5 mL of intrave-nous contrast was used.

Emergency EVAR patients. During the same period,64 patients (55 men, 9 women) underwent stent graftinsertion as an emergency for AAA. Their average age was75.5 � 7.5 years. Two patients underwent Zenith (Cook,Bloomington, Ind) stent graft placement to gain control oftheir AAA, and Talent stent grafts were used in the remain-ing patients. During their primary repair, 15 patients alsorequired a balloon-expandable Palmaz stent graft duringtheir primary repair.

The screening time was 22.9 � 18.2 minutes, and theradiation dose was 53.8 � 34.6 Gycm.2 The effective dosewas calculated as 13.4 � 8.6 mSv (range 1.0-41.0 mSv).The average contrast volume was 187.1 � 98.1 mL. Thecorrelation between screening time and radiation dose (r �0.49, P � .0002) and contrast volume (r � 0.53, P �.0001) was similarly moderate in emergencies, althoughbetter correlation was seen between the radiation dose and

Table. The radiation dose (in mSv) over time as a result o

Time Group EVAR

Preop ElectiveEmergency

Postop Elective 11.7Emergency 13.4

Year(s)1 Elective 2

Emergency 25 Elective 3

Emergency 310 Elective 4

Emergency 415 Elective 4

Emergency 420 Elective 4

Emergency 425 Elective 4

Emergency 4

AXR, Abdominal x-ray; CT, computed tomography.

contrast volume (r � 0.61, P � .0001). The lack of

strength in correlation between screening time and radia-tion dose is due to the variable proportions within a proce-dure of single fluoroscopic images and digital subtractionangiographic runs, which have a higher dose. These pro-portions had not been recorded separately and may varybetween primary and secondary operations and betweenelective and emergency procedures. The effective dose ofradiation in preoperative CT, EVAR, and postoperativesurveillance for the first year was a mean total of 47.2 mSv.

Four patients underwent an additional secondary inter-vention. The indication was endoleak in one and migrationin three. These had an average screening time of 21.5 �20.2 minutes, with a radiation dose of 49.9 � 42.6 Gycm2

(12.5 � 1.1 mSv) and contrast volume of 106.2 � 59.8mL. The effective dose was calculated as 8.4 � 7.1 mSv.

Long-term follow-up. The total radiation doses(mSv) for elective and emergency patients as a result of theEVAR procedure and preoperative and postoperative CTand AXR are reported in the Table. This calculation as-sumed that all patients complied with the same recom-mended postoperative follow-up from this unit, which wasCT at 1, 3, and 12 months and annually thereafter, alongwith annual AXR, in accordance with the protocol of theEVAR trials. Radiation exposure is nonsignificantly greaterin emergency patients due to the slightly higher doseintraoperatively; however, radiation exposure thereafter isassumed to be the same. For simplicity and because of thesmall number of patients involved, the risk of secondaryintervention was not included, although this would in-crease exposure further due to the intraoperative dose andas a result of the patient reverting back to the first-yearschedule of three CT scans after any intervention.

DISCUSSION

This study assessed radiation exposure during EVARand in the follow-up, although currently, no national

ergoing endovascular aneurysm repair (EVAR)

AXR Total Cumulative total

8.0 8.08.0 8.0

11.7 19.713.4 21.4

1.8 25.8 45.51.8 25.8 47.27.2 39.2 84.77.2 39.2 86.49.0 49.0 1133.79.0 49.0 135.49.0 49.0 182.79.0 49.0 184.49.0 49.0 231.79.0 49.0 233.49.0 49.0 280.79.0 49.0 282.4

f und

CT

8.08.0

4.04.02.02.00.00.00.00.00.00.00.00.0

guidelines are available regarding radiation exposure with

JOURNAL OF VASCULAR SURGERYVolume 52, Number 2 Jones et al 301

which to compare the results. The study has a number ofstrengths. Firstly, it has the largest patient cohort in theliterature to date, during a 10-year period. Secondly, theconsideration of radiation exposure in emergency repairs,which is becoming increasingly common, has not beenpreviously reported to our knowledge. Finally, the incor-poration of preoperative and postoperative radiographicimaging helps to provide an overall impression of radiationexposure associated with EVAR.

Radiation exposure is a risk factor for developing cancerbut is associated with a latency period of between 10 and 20years.6 The mean age of patients in this study of 75 yearsrepresents most EVAR patients, and therefore, this risk maynot be of significant clinical importance. The other associ-ated risk of radiation exposure is acute skin injury, which isusually seen with skin doses �2 Gy.6 Imaging equipmentcan be adapted to reduce this by using a heavy copperinfiltration beam in the mobile C arm, resulting in a rela-tively low output. With these recognized dangers thereforein mind, it reinforces the importance of monitoring theradiation exposure involved in EVAR, with patient safetybeing paramount.

The screening time within this present study comparesfavorably with other smaller studies of 24 and 12 patients,which reported average screening times of 28 in electivecases and 20.6 minutes in emergency cases.19,20 The effec-tive radiation dose in elective patients also is comparablewith other published data of 10.5 mSv.19 One weakness inour results is the lack of recorded data on patient weightand body mass index, because obese patients require in-creased radiation to maintain image quality.20 Therefore,any prospective trial should incorporate this variable intothe study design and statistical model with the use ofpatient radiation counters.

The different stent grafts that were used might haveinfluenced the three radiologic parameters. Although aTalent device was used in 97% of emergency procedures,this proportion dropped to 75% in elective repairs. A lack offamiliarity in the occasional use of other devices may resultin longer repair times and higher radiation doses in thesepatients, but the wide experience of the unit in EVARshould more than compensate for this additional variable.

The radiation exposure of secondary procedures hasnot been incorporated into the cumulative data during thefollow-up years. This is because although it influenced theresults for those individuals, most of the secondary inter-ventions were performed on a small number of patientswho sometimes required repeated procedures; therefore,the patients would not be representative of the overallcohort and their results not widely applicable.

Elective EVARs were commenced in the vascular unitbefore emergency repairs were attempted, therefore gain-ing sufficient experience before the first emergency repair.Although the screening time was lower, reflecting differingsurgical strategies, the radiation dose and contrast volumeswere higher, suggesting that less emphasis was placed uponradiation reduction in emergency EVARs. Patients present-

ing with ruptured AAA have a higher morbidity and mor-

tality rates than patients undergoing elective repair. How-ever, because EVAR for rupture has a lower morbidity andmortality than open repair, it would be reasonable to acceptthis higher radiation exposure in these patients withoutimplying any compromise of patient safety.21 Thus, thisstudy further strengthens the argument in favor of EVAR ofemergency patients, where anatomically suitable.

Weerakkody et al22 demonstrated a mean effective ra-diation dose of 79 mSv during a 1-year period, includingEVAR and follow-up. We have reported an effective dose of45.5 mSv in a 1-year follow-up, which included preopera-tive investigations, the procedure, and 1 year of surveillancefor elective patients. The benefit in exposing patients tofurther postoperative radiation is questionable. A recentstudy of 304 patients with a total of 1167 CT scans dem-onstrated that only 9.3% of patients benefitted from post-operative follow-up CT scanning as abnormalities that re-quired further intervention were detected in otherwiseasymptomatic patients.23 In the presence of a normal CTresult at 1 month, there was no benefit to the patient toundergo a further CT until the scan at 1 year.24

To avoid excessive radiation, follow-up of EVAR pa-tients using a different imaging modality may be appropri-ate. Duplex ultrasound imaging has a sensitivity of 86% todetect endoleaks and a specificity of 67% due to a largenumber of false-positives.25 It can determine graft patencyand sac size as well as determine postoperative complica-tions of EVAR that require reintervention, with the recog-nized benefits of reduced cost and radiation exposure.26

Thus, the accuracy of duplex imaging may negate therequirement for regular CT, particularly for type II en-doleaks in the presence of decreasing sac size.27 Althoughtype I and III endoleaks may require intervention, furtherresearch into flow characteristics of type II endoleak mayallow patient selection for reintervention to be decided onduplex criteria. This alternative follow-up option may beespecially relevant in younger patients to reduce the long-term carcinogenic risks of radiation exposure but is lesspertinent for older patients because of the recognized la-tency period.28 The protocol of our unit is under review tocommence utilization of duplex imaging and AXR as thesole follow-up rather than annual CT scans.

CONCLUSIONS

EVAR and the follow-up investigations involve sub-stantial amounts of radiation, with well-recognized carci-nogenic risks. Because patient safety is paramount, radia-tion exposure should be minimized. This may be possibleby standardizing radiation exposure throughout theUnited Kingdom by the implementation of national guide-lines, along with considering other imaging modalities forfollow-up.

AUTHOR CONTRIBUTIONS

Conception and design: CJ, SBAnalysis and interpretation: CJ, SBData collection: CJ, SB

Writing the article: CJ, SB

JOURNAL OF VASCULAR SURGERYAugust 2010302 Jones et al

Critical revision of the article: CB, SVFinal approval of the article: CJ, CBStatistical analysis: SBObtained funding: Not applicableOverall responsibility: CJ

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Submitted Dec 20, 2009; accepted Mar 4, 2010.