| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Evidence-based Practice |
1 From the Dept of Radiology, Massachusetts General Hospital, Harvard Medical School, Zero Emerson Pl, Ste 2H, Boston, MA 02114 (M.E.A.P.M.A., J.L.B., E.F.H., G.S.G.); Depts of Radiology (M.E.A.P.M.A., M.G.M.H.) and Epidemiology and Biostatistics (M.E.A.P.M.A., J.L.B., M.G.M.H.), Erasmus Univ Med Ctr, Rotterdam, the Netherlands; and Dept of Health Policy and Management, Harvard School of Public Health, Boston, Mass (M.G.M.H., G.S.G.). From the 2001 RSNA scientific assembly. Received Oct 12, 2001; revision requested Dec 26; revision received Jan 15, 2002; accepted Mar 12. M.E.A.P.M.A. supported by grants from Foundation Fundatie van de Vrijvrouwe van Renswoude, Foundation Gerrit Jan Mulder Stichting, Netherland-America Foundation, Netherlands Heart Foundation, Foundation Stichting Dr Hendrik Muller’s Vaderlandsch Fonds, Foundation Stichting Jo Kolk Studiefonds, Talentenprogramma Award for Talented Students by the Dutch Ministry of Education, Foundation Van Walree Fonds of the Royal Netherlands Academy of Arts and Sciences, Foundation Vereniging Trustfonds Erasmus Univ Rotterdam, and VSB Foundation. J.L.B., E.F.H., G.S.G. supported in part by the U.S. Dept of the Army under DAMD 17-99-2-9001. The information presented does not necessarily represent the position of the government, and no official endorsement should be inferred. Address correspondence to G.S.G.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONAPPENDIXREFERENCES |
|---|
MATERIALS AND METHODS: A MEDLINE search of the English literature was performed. Studies with at least 10 patients in each treatment group were included if they reported patient characteristics, complications, and mortality. Two reviewers independently extracted the data. A random-effects model was used to pool the data and calculate pooled odds ratios (endovascular vs open surgical repair).
RESULTS: Nine studies were included, reporting results of 1,318 procedures (687 endovascular repair and 631 open surgical repair). Mean blood loss was 456 mL for endovascular repair and 1,202 mL for open surgical repair (P = .003). On average, patients undergoing endovascular repair spent 0.5 days in the intensive care unit and 3.9 days in the hospital, and patients undergoing open surgical repair spent 2.2 days (P = .04) in the intensive care unit and 10.3 days (P = .02) in the hospital. The pooled 30-day-mortality was 0.03 for endovascular repair (95% CI: 0.02, 0.04) and 0.04 for open surgical repair (95% CI: 0.00, 0.07) (P = .03), and the odds ratio was 0.55 (95% CI: 0.33, 0.92). The pooled local and/or vascular complication rate was 0.16 for endovascular repair (95% CI: 0.06, 0.25) and 0.12 for open surgical repair (95% CI: 0.06, 0.18) (P = .46), and the odds ratio was 0.97 (95% CI: 0.62, 1.54). The pooled systemic and/or remote complication rate was 0.17 for endovascular repair (95% CI: 0.09, 0.25) and 0.44 for open surgical repair (95% CI: 0.21, 0.66) (P < .001), and the odds ratio was 0.22 (95% CI: 0.11, 0.45).
CONCLUSION: On the basis of this systematic review, endovascular repair results in less blood loss, shorter intensive care unit and hospital stays, lower 30-day mortality, and lower systemic and/or remote complication rates than those of open surgical repair.
© RSNA, 2002
Index terms: Aneurysm, abdominal, 943.73 • Aneurysm, aortic, 943.73 • Aneurysm, surgery, 943.1268, 943.73 • Data, analysis • Grafts, interventional procedures, 943.1268
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONAPPENDIXREFERENCES |
|---|
Open surgical repair was the first method used to treat abdominal aortic aneurysms electively. Since 1991, an alternative method—endovascular repair—has become available (4). Endovascular repair is less invasive and does not require abdominal laparotomy and long periods of aortic clamping. It has the potential to reduce procedure-related morbidity and mortality rates from those associated with open surgical repair and shorten the postprocedural recovery period.
Investigators in several reports have described short-term results for endovascular repair of abdominal aortic aneurysms. These reports provide a wide range of estimates for short-term morbidity and mortality. For example, estimates for the systemic and/or remote complication rate for endovascular repair varied between 0% and 39% (5,6), and estimates for the 30-day mortality rate for endovascular repair varied between 0% and 6.1% (7,8). To better understand the appropriate use of this new technology, it is important to evaluate these short-term results. Moreover, a published cost-effectiveness analysis comparing elective endovascular and open surgical repair of abdominal aortic aneurysms showed that the cost-effectiveness of endovascular repair is critically dependent on its potential to reduce morbidity and mortality rates from those associated with open surgical repair (9). That same analysis showed that varying the costs or incidence of repeat interventions for either endovascular repair (for graft thrombosis or endoleak) or open surgical repair (for graft thrombosis or hemorrhage) had no influence on the cost-effectiveness of endovascular repair (9). Furthermore, it was suggested that investigators should place primary focus on morbidity and mortality rates when considering the effectiveness of endovascular repair (9). So far, to our knowledge, no randomized controlled trial comparing elective endovascular and open surgical repair has been published. The purpose of this study was to summarize and compare published short-term results of elective endovascular and open surgical repair of abdominal aortic aneurysms.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONAPPENDIXREFERENCES |
|---|
Nine studies (5–8,10–14) met our inclusion criteria, in which the results of 1,318 procedures were reported. The total number of patients undergoing endovascular repair (n = 687) was higher than the total number of patients undergoing open surgical repair (n = 631). In Table 1, the characteristics of the included studies are given. The publication dates of the studies varied from June 1998 to February 2001. Patients were enrolled in these studies from 1992 to 1999. All studies were observational. Various strategies were used to enroll patients in the endovascular and open surgical groups (Appendix). In most studies, one or two institutions were involved, with the exception of the study by Zarins et al (14), in which 12 institutions were involved. In six of the nine studies, the first endovascular procedures performed at the institution were included in the endovascular repair group (5,8,10,11,13,14). May et al (12) performed their first endovascular procedure in 1992, but their study period started in May 1995. It is unclear if the other investigators (6,7) had performed any endovascular procedures before the start of their study periods.
|
Short-term results were defined as all measurable results within 30 days of the procedure, including duration of the procedure, blood loss during the procedure, number of days in the intensive care unit, number of days in the hospital, and 30-day mortality and complication rates. Complications were extracted as they were described in the studies. We made a distinction between complications and outcomes related to the aneurysm or to the graft. Complications included, for example, wound infection, postoperative hemorrhage, myocardial infarction, pneumonia, and sepsis. The existence of an endoleak, graft thrombosis, or graft occlusion; increasing aneurysm size over time; aneurysm rupture; and conversion to open surgical repair were considered treatment outcomes—that is to say, they were considered to be potential aneurysm- and graft-related failures rather than complications.
Data Synthesis
To assess the possibility of publication bias (ie, bias resulting from more studies with a desirable result being published than those with an undesirable result), we constructed a funnel plot (15). In a funnel plot, an estimate of the precision of the effect size for each study (in our study, the reciprocal of the standard error of the 30-day mortality odds ratio) is plotted as a function of the corresponding effect-size estimate (in our study, the natural logarithm of the odds ratio). In the absence of publication bias, the data points from all studies (one point for each study) should take the shape of a symmetrical inverted funnel-shaped distribution (inverted V shape); the effect-size estimates from larger, more precise studies will converge; and the effect-size estimates from smaller, less precise studies will be scattered symmetrically at the bottom of the funnel plot. If publication bias is present, the data points will be distributed in an asymmetrical fashion. For example, one side of the funnel shape can be missing. We used 30-day mortality as effect size, since it was the most robust, most standardized outcome presented in the studies.
In our meta-analysis, we assumed that the individual studies were a random sample of a hypothetical population of studies comparing elective endovascular and open surgical repair of abdominal aortic aneurysms (16). Therefore, we used a random-effects model, which takes into account the between-study variance (derived from the sampling of studies) and the within-study variance (derived from the limited sample size of each study), to pool discrete variables throughout our study (16).
From the data provided in the individual studies, we calculated weighted means for patient age and abdominal aortic diameter. The estimates were weighted for sample size. For patient sex and preoperative risk factors, we calculated pooled estimates and their 95% CIs by using the random-effects model described by Laird and Mosteller (16).
To summarize the short-term results of both treatment groups, we calculated weighted means for duration of the procedure, blood loss during the procedure, days in the intensive care unit after the procedure, and total length of stay in the hospital. For the overall 30-day mortality and complication rates, we calculated pooled estimates and their 95% CIs by using the random-effects model described by Laird and Mosteller (16). In addition to reporting the total complication rate of endovascular and open surgical repair, we divided the total complication rate into a local and/or vascular complication rate and a systemic and/or remote complication rate, as has been suggested by several investigators in articles about reporting standards (17–21). We also reported complications according to type (ie, arterial injury, embolization and/or occlusion, limb ischemia, wound, bleeding, renal sepsis, and cardiac, neurologic, pulmonary, gastrointestinal, and other complications). The word occlusion was used to refer to coverage of renal arteries and unintentional branch occlusion.
All pooled estimates were compared between treatment groups by using the Student t test and the 
2 test as appropriate. Two-sided P values of .05 or less were considered to indicate a statistically significant difference.
To compare 30-day mortality, total complication rates, local and/or vascular complication rates, and systemic and/or remote complication rates between the two treatment groups, we also calculated pooled odds ratios (endovascular vs open surgical repair). Pooled odds ratios and their 95% CIs were calculated by using the random-effects model described by DerSimonian and Laird (22,23).
To test for heterogeneity in patient characteristics and short-term results across the studies, we used the 2 test, and to test for heterogeneity in the odds ratios across the studies, we used the Cochran-Mantel-Haenszel test.
Most analyses were performed with Microsoft Excel software (Redmond, Wash). Only the Cochran-Mantel-Haenszel test was performed with SAS version 7 software (Statistical Analysis Systems, Cary, NC).
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONAPPENDIXREFERENCES |
|---|
|
|
|
Conversion to open surgical repair during the initial procedure or within 30 days after endovascular repair was seen in 0%–10% of patients treated with endovascular repair, with a pooled estimate of 0.03 (95% CI: 0.00, 0.05). In four additional patients in whom iliac arterial access was impossible, the endovascular procedure was abandoned, and no open surgical repair was performed (14). Early endoleak was seen in 7%–29% of patients in the individual studies. The pooled estimate of early endoleak after endovascular repair was 0.20 (95% CI: 0.15, 0.24).
The duration of an endovascular procedure (mean, 192 minutes) was not significantly different from the duration of an open surgical procedure (mean, 200 minutes) (P = .79) (Table 3). Blood loss during the procedure was significantly less for endovascular repair (mean, 456 mL) than for open surgical repair (mean, 1,202 mL) (P = .003) (Table 3). The number of days spent in the intensive care unit after the procedure and the number of days spent in the hospital were both significantly less for endovascular repair (mean, 0.5 and 3.9 days, respectively) than for open surgical repair (mean, 2.2 and 10.3 days, respectively) (P = .04 and P = .02, respectively) (Table 3).
The 30-day mortality ranged from 0.00 to 0.06 for endovascular repair and from 0.00 to 0.16 for open surgical repair. The pooled estimate of 30-day mortality for endovascular repair (0.03; 95% CI: 0.02, 0.04) was significantly lower than that for open surgical repair (0.04; 95% CI: 0.00, 0.07) (P = .03) (Table 3). The likelihood of dying within 30 days after elective repair of an abdominal aortic aneurysm was reduced by undergoing an endovascular procedure (pooled odds ratio, 0.55; 95% CI: 0.18, 0.71).
The pooled estimate of total complication rate for endovascular repair (0.30; 95% CI: 0.20, 0.40) was significantly lower than that for open surgical repair (0.53; 95% CI: 0.30, 0.75) (P < .001) (Table 3). The likelihood of experiencing a complication after elective repair of an abdominal aortic aneurysm was reduced by undergoing an endovascular procedure (pooled odds ratio, 0.26; 95% CI: 0.09, 0.78).
For local and/or vascular complication rates, the pooled estimate was 0.16 (95% CI: 0.06, 0.25) for endovascular repair and 0.12 (95% CI: 0.06, 0.18) for open surgical repair (P = .46) (Table 3). No significant difference was found in the likelihood of experiencing a local and/or vascular complication after endovascular or open surgical repair (pooled odds ratio, 0.97; 95% CI: 0.62, 1.54).
The pooled estimate of systemic and/ or remote complication rates for endovascular repair (0.17; 95% CI: 0.09, 0.25) was significantly lower than that for open surgical repair (0.44; 95% CI: 0.21, 0.66) (P < .001) (Table 3). The likelihood of experiencing a systemic and/or remote complication after elective repair of an abdominal aortic aneurysm was reduced by undergoing an endovascular procedure (pooled odds ratio, 0.22; 95% CI: 0.11, 0.45).
Variation in the presence of risk factors and reported short-term results across the studies included in this systematic review was present, as shown by results of tests for heterogeneity. However, no relationship between the presence of risk factors and worse short-term results could be detected by eyeballing the data. Variations in odds ratios across the studies were demonstrated for total complication rate and systemic and/or remote complication rate.
Table 4 presents a more detailed overview of the reported complications. Significant differences were found in the proportion of arterial injury, bleeding, and cardiac, pulmonary, renal, and gastrointestinal complications. With the exception of arterial injury, the proportions were higher for open surgical repair. Arterial injury was observed more often after endovascular repair than after open surgical repair (P < .001). Cardiac, pulmonary, renal, and gastrointestinal complications, as well as bleeding, were observed more often after open surgical repair than after endovascular repair (P < .001, P < .001, P = .02, P = .002, and P = .04, respectively).
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONAPPENDIXREFERENCES |
|---|
The pooled 30-day mortality of 3% for endovascular repair in this systematic review was in agreement with the 30-day mortality for endovascular repair in the EUROSTAR registry, in which 40 of 1,554 patients (2.6%) died (24). Data from the EUROSTAR registry were not included in this systematic review because a control group of patients treated with open surgical repair was not reported. Two other studies with a large cohort of patients treated with endovascular repair reported a lower 30-day mortality. Twenty-three of 1,192 patients (2.0%) treated within the first 4 years of the U.S. AneuRx clinical trial died within 30 days of the procedure, and 10 of 669 patients (1.5%) treated worldwide with an EVT tube or bifurcated graft between February 1993 and October 1997 died within 30 days of the procedure (25,26). Less blood loss, fewer blood transfusions, and shorter intensive care unit and hospital stays with endovascular repair than those associated with open surgical repair have also been reported in other studies (27–31).
We found that the duration of an endovascular procedure (mean, 192 minutes) was not significantly different from the duration of an open surgical procedure (mean, 200 minutes). Other studies (27–31) reporting procedure times for both treatment options also found a slightly shorter procedure time for endovascular repair than that for open surgical repair, but the difference was only significant in three of five of these studies (27,28,31). It should be noted, however, that endovascular repair was a new procedure, and most of the studies in this systematic review included consecutive endovascular repairs starting from the first endovascular procedure performed at their institution.
Results of a previous study demonstrated that the cost-effectiveness of endovascular repair was critically dependent on its potential to reduce morbidity and mortality rates from those associated with open surgical repair (9). If the mortality rate for endovascular repair increased from 1.2% to greater than 4.4% or if the mortality rate for open surgical repair decreased from 4.4% to less than 1.7%, endovascular repair was no longer cost-effective (9). Endovascular repair will be a cost-effective alternative if it can produce a substantial decrease in morbidity and mortality rates, which is most likely to occur in patients at high risk (9). On the basis of our results, endovascular repair does indeed seem to reduce short-term morbidity and mortality rates. There is still uncertainty, however, regarding the long-term effectiveness of endovascular repair. Threats to the long-term effectiveness of endovascular repair could include endoleaks, graft distortion, limb graft occlusion, and material fatigue (32). The consequences of having an endoleak are still unclear. Different consequences have been published, varying from a decreased maximum transverse diameter in patients with temporary endoleak and no change in patients with persistent endoleak to no statistically significant diameter changes between patients with and patients without endoleak and an increased diameter in patients with persistent endoleak (33–35). Furthermore, aneurysm rupture occurred in patients with and patients without endoleak (36). Threats to the long-term effectiveness of open surgical repair include pseudoaneurysm rupture, suprarenal and iliac aneurysm formation, graft infection, aortoenteric fistula, and graft thrombosis (25,26). Also, endoleaks have been reported after open surgical repair (37). The same cost-effectiveness analysis showed, however, that varying the costs or incidence of repeat interventions for either endovascular repair (for graft thrombosis or endoleak) or open surgical repair (for graft thrombosis or hemorrhage) had no influence on the cost-effectiveness of endovascular repair (9). Before a final comparison between endovascular and open surgical repair can be made and a definite conclusion reached, however, long-term mortality rates should be taken into account, as well.
The principal limitation of our study was that the individual studies included in our systematic review were not based on randomized controlled clinical trials. Various strategies were used to enroll patients in the endovascular and open surgical repair groups (Appendix). Demographic and clinical characteristics were not significantly different between groups, however, with the exception of male sex and the presence of cardiac comorbidities, which were more common in the endovascular group, and smoking, which was more common in the open surgical group. Of course, we could not compare unknown confounders and unpublished characteristics between the treatment groups. For example, the average number of risk factors per patient was not reported. Only Becquemin et al (10) reported that the percentage of patients with two or more risk factors was higher in the endovascular repair group than in the open surgical repair group (P = .01). In a cohort study of endovascular repair in 116 high-risk patients, the 30-day mortality and total complication rate were 2% and 20%, respectively (38), which is lower than the 3% and 30% found in our systematic review.
Publication bias may have affected our results. To assess publication bias, we constructed a funnel plot. The funnel plot suggested that small studies with a low mortality in the endovascular repair group when compared with that in the open surgical repair group may have been underrepresented. Therefore, if present, any publication bias worked against endovascular repair. In spite of this bias, the pooled estimate was still in favor of endovascular repair.
Data collection within the individual studies may also have been a source of bias, especially when data were collected retrospectively in one treatment group and prospectively in the other. In three studies, it was not clear how the open surgical repair data were collected (8,12,13), but the endovascular repair data were collected prospectively. The other studies used the same method for both groups. Because prospectively collected data are likely to be more carefully scrutinized, this potential bias would be expected to work against endovascular repair.
Our study was limited by the originally reported data and the lack of standardization. To reduce the effect of differing interpretations of reported data, two authors independently extracted the data. Lack of standardization was most apparent while dealing with morbidity. Each study defined morbidity differently or did not define it at all, resulting in heterogeneity in the total complication rate and systemic and/or remote complication rate across the studies. To present a complete overview of all complications, we reported all complications as described in the individual studies. Furthermore, we classified complications into local and/or vascular and systemic and/or remote groups, as has been suggested by several authors who were trying to improve reporting standards (17–21). Fatal complications were excluded from the complication rate and were included in the 30-day mortality rate, according to common practice. Events related to the aneurysm and the patency of the graft were excluded from the complication rate, since the reporting of these events is dependent on the available follow-up in the individual studies, which was generally not performed for patients who underwent open surgical repair, and would thus have introduced uncertainty and potential bias into the analysis.
Unfortunately, incorporation of the severity of the complications into our analysis was not possible, because severity was not reported consistently in the included studies. Two European cohort studies, one on endovascular repair and one on open surgical repair, graded complications as mild, moderate, and severe, following the recommendations of the Ad Hoc Committee on Reporting Standards (39,40). The distribution of complications was 24% mild, 55% moderate, and 21% severe for endovascular repair (40) and 29% mild, 36% moderate, and 34% severe for open surgical repair (39). It was not possible to incorporate the actual number of patients with a complication into our analysis, since only Birch et al (11) and Brewster et al (8) reported those numbers. Since one patient could experience more than one complication, the number of patients with complications need not equal the number of complications. We extracted the total number of complications reported in each study. Brewster et al (8) reported a total of 14 complications in 13 patients who had at least one complication after endovascular repair and a total of 20 complications in 14 patients who had at least one complication after open surgical repair. The EUROSTAR registry reported a total of 369 systemic complications in 279 of 1,554 patients who underwent endovascular repair (24).
In conclusion, our results suggest that elective endovascular repair for abdominal aortic aneurysms results in less blood loss, shorter intensive care unit and hospital stays, lower 30-day mortality, and lower systemic and/or remote complication rates than those of elective open surgical repair for abdominal aortic aneurysms. These favorable short-term results add further support to prior studies citing the benefits of endovascular repair.
|
APPENDIX |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONAPPENDIXREFERENCES |
|---|
|
FOOTNOTES |
|---|
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONAPPENDIXREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  E. J. R. van Beek and D. E. Malone Evidence-based Practice in Radiology Education: Why and How Should We Teach It? Radiology, June 1, 2007; 243(3): 633 - 640. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. J. Leurs, J. Buth, R. J. F. Laheij, and for the EUROSTAR Collaborators Long-term Results of Endovascular Abdominal Aortic Aneurysm Treatment With the First Generation of Commercially Available Stent Grafts Arch Surg, January 1, 2007; 142(1): 33 - 41. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. N. Ghansah and J. T. Murphy Complications of Major Aortic and Lower Extremity Vascular Surgery Seminars in Cardiothoracic and Vascular Anesthesia, December 1, 2004; 8(4): 335 - 361. [Abstract] [PDF]
|
|
|
|
 |
|
 M. Prinssen, E. L.G. Verhoeven, J. Buth, P. W.M. Cuypers, M. R.H.M. van Sambeek, R. Balm, E. Buskens, D. E. Grobbee, J. D. Blankensteijn, and the Dutch Randomized Endovascular Aneurysm Managem A Randomized Trial Comparing Conventional and Endovascular Repair of Abdominal Aortic Aneurysms N. Engl. J. Med., October 14, 2004; 351(16): 1607 - 1618. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. S. Lee and C. K. Zarins Endograft Migration: Incidence, Causes, and Clinical Significance Perspectives in Vascular Surgery and Endovascular Therapy, September 1, 2004; 16(3): 187 - 191. [Abstract] [PDF]
|
|
|
|
|
|
H. O. Stolberg Treatment of Abdominal Aortic Aneurysms: Review with Evidence-based Methods Radiology, September 1, 2003; 228(3): 614 - 616. [Full Text] [PDF]
|
|
|
|
|
|
M. M. Maher, A. M. McNamara, P. M. MacEneaney, S. J. Sheehan, and D. E. Malone Abdominal Aortic Aneurysms: Elective Endovascular Repair versus Conventional Surgery--Evaluation with Evidence-based Medicine Techniques Radiology, September 1, 2003; 228(3): 647 - 658. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. A Michaels Screening for abdominal aortic aneurysms was cost effective for prolonging survival from AAA related death in older men Evid. Based Med., July 1, 2003; 8(4): 125 - 125. [Full Text] [PDF]
|
|
|
|
|
|
J. L. Bosch, J. A. Kaufman, M. T. Beinfeld, M. E. A. P. M. Adriaensen, D. C. Brewster, and G. S. Gazelle Abdominal Aortic Aneurysms: Cost-effectiveness of Elective Endovascular and Open Surgical Repair Radiology, November 1, 2002; 225(2): 337 - 344. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| RADIOLOGY | RADIOGRAPHICS | RSNA JOURNALS ONLINE |
= studies.