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Barotrauma due to stent deployment in endovascular brachytherapy for restenosis prevention
Int. J. Radiation Oncology Biol. Phys., Vol. 47, No. 4, pp. 1021–1024, 2000 Copyright © 2000 Elsevier Science Inc. Printed in the USA. All rights reserved 0360-3016/00/$–see front matter
PII S0360-3016(00)00515-0
CLINICAL INVESTIGATION
Benign Disease
BAROTRAUMA DUE TO STENT DEPLOYMENT IN ENDOVASCULAR BRACHYTHERAPY FOR RESTENOSIS PREVENTION HUAN GIAP, M.D., PH.D.,* PAUL TEIRSTEIN, M.D.,† VINCENT MASSULLO, M.D.,* PRABHAKAR TRIPURANENI, M.D., F.A.C.R.*
AND
Divisions of *Radiation Oncology and †Interventional Cardiology, Scripps Clinic, La Jolla, CA Purpose: In this study, the effect of barotrauma due to stent deployment is investigated for several commonly used commercial stents used in endovascular brachytherapy for restenosis prevention. Methods and Materials: Restenosis due to intimal hyperplasia can occur anywhere along the clinical target volume, which is defined as the length of vessel receiving intervention or injury. The injury may be due to angioplasty, atherectomy (tissue removing), stenting, and stent deployment. Manufacturer specifications for several commonly used stents were reviewed and the results were tabulated. Results: The barotrauma length of stents reviewed in this study ranges from 0.5 to 2.5 mm; the average was 1.7 mm. Conclusions: By considering specific barotrauma into the treatment length, one can provide adequate treatment margins to minimize edge failure or to avoid “geographic miss,” which may improve the efficacy of endovascular brachytherapy. © 2000 Elsevier Science Inc. Barotrauma, Stent deployment, Endovascular brachytherapy, Restenosis.
of radioactive sources (endovascular brachytherapy) might prevent restenosis. Experimental studies in animal models have documented the profound effects of endovascular brachytherapy (EVBT) in reducing restenosis following angioplasty and stenting. Early results of several prospective, double-blind, randomized clinical trials are encouraging and confirm the positive results. Within several years, more than a dozen prospective, multicenter, randomized trials have been initiated to test the safety and efficacy of EVBT. This new field involves many specialties with no history of collaboration, and the role of each discipline is still evolving, and remains undefined. There are several wellestablished concepts in radiation therapy that require clarification for cardiologists, interventional radiologists, and vascular surgeons. One of these important concepts is the target definition for EVBT. Current clinical trials in EVBT emphasize the total prescribed dose at a specific radial distance; however, few trials explicitly define the treatment length or specify how a certain length of source train is chosen for treatment. The significance of an adequate treatment margin has been demonstrated recently by observation of local failures at the edge of stent and near the end of the angioplasty balloon (6 – 8). In the Scripps I study, minimal margin was provided, and approximately one-half of reste-
INTRODUCTION There are approximately one million patients undergoing percutaneous transluminal coronary angioplasty (PTCA) annually, and 20 –50% develop re-narrowing of the treated artery (restenosis) within 6 months of the procedure date (1). Initial therapeutic approaches that focused on pharmaceutical agents, mechanical devices (atherectomy), physical devices (stenting), and more recently, gene therapy, have demonstrated limited success. The idea of using a balloon for simultaneous vessel dilation and stent delivery for canine non-coronary vessels was initially introduced by Palmaz et al. in 1985 (2). With the refinement of equipment and new stent design, the application of stent to canine coronary vessels was possible in 1987 (3). By early 1988, 117 self-expanding intravascular stents had been implanted in native coronary arteries or in bypass grafts of 105 patients (4). In 1991, Schatz et al. reported a multicenter study of elective stent placement in native coronary vessels after successful angioplasty in 213 patients, with 299 stents in 230 lesions. The successful delivery of these stents was 93%, and the restenosis rate was 36% (5). Recently, several investigators reported that localized irradiation of the angioplasty site by intraluminal placement
would like to thank the Scripps Clinic medical writer, Marcia Straile, for her excellent support in the writing of this manuscript. H.B.G. is grateful to Jeff Anderson and the Cardiac Cath Lab personnel for their assistance. Accepted for publication 10 February 2000.
Reprint requests to: Huan Giap, M.D., Ph.D., Division of Radiation Oncology, Scripps Clinic, 10666 North Torrey Pines Road, La Jolla, CA 92037. Tel (858) 554-2000; Fax: (858) 554-6082; E-mail: [email protected] Acknowledgments—We would like to acknowledge the unnamed reviewers of this article for their valuable comments. H. B. G. 1021
1022
I. J. Radiation Oncology
●
Biology
●
Physics
Fig. 1. Definition of barotrauma due to stent deployment.
nosis occurred at the stent margin. There are several postulations for the marginal failures, including inadequate length of radioactive source, source movements, inaccurate placement of radioactive source, and barotrauma (9). After angioplasty, a metallic stent is usually placed into the vessel by balloon expansion. The term “barotrauma” used in this paper refers to the injury to the vessel arising from the stent deployment balloon. This study reviews current stent design and estimates the length of barotrauma beyond the stented length. METHODS AND MATERIALS Adequate treatment of a vascular lesion using endovascular brachytherapy requires specification of the clinical target length (CTL), which is defined as the length of vessel receiving intervention or injury (10). This may be due to angioplasty, atherectomy (tissue removing), stenting, and stent deployment. Restenosis due to neointimal hyperplasia can occur anywhere along the CTL. When EVBT is used, the entire length of CTL must be covered by radioactive sources. The length of the balloon used for stent deployment is typically longer the stent itself (Fig. 1). The most proximal and most distal sites of injury constitute the CTL, and this is demonstrated schematically in Fig. 2. Accurate localization of CTL is crucial for successful application of EBVT to prevent restenosis. Current Food and Drug Administration (FDA)-approved stents for coronary intervention are reviewed in Table 1. Nine different stent designs available at Scripps Clinic were reviewed in this study. The stent trade name and
Fig. 2. Definition of CTL for endovascular brachytherapy to prevent restenosis.
Volume 47, Number 4, 2000
corresponding manufacturers are as follows: Palmaz-Schatz Crown™ and Mini-Crown™ (Cordis Corp., Miami, FL), GFX™ (Arterial Vascular Engineering, Santa Rosa, CA), ACS Multi-Link™, ACS Multi-Link OTW Duet™, ACS Multi-Link Rx Duet™ (GUIDANT Advanced Cardiovascular Systems, Temecula, CA), NIR Primo, NIR on Ranger™, NIR on Ranger with SOX™ (Boston Scientific Corp/ SciMed, Maple Grove, MN). The specifications from the manufacturer’s package inserts were reviewed, and the lengths of each stent and balloon were obtained and tabulated in Table 1. Barotrauma length indicates the length of the balloon beyond the stent edge, and this value is half of the difference between the balloon length and the stent length. This calculation of barotrauma length assumes that the proximal and distal extensions of the balloon are equal and that the stent is mounted centrally on the balloon. RESULTS AND DISCUSSION In this study, the mean length of barotrauma beyond the stent margin was 1.7 mm, ranging from 0.5 to 2.5 mm. Some relevant factors in stent design include flexibility, tractability, low-unconstrained profile, radio-opacity, thromboresistance, biocompatibility, reliable expandability, radial strength, circumferential coverage, low surface area, and hydrodynamic compatibility (11). The length of its barotrauma should not determine the merit of the stent. In fact, for most stents, the length of barotrauma is similar and approximately equal to half the length of commonly used brachytherapy seeds. In endovascular brachytherapy, stenting is often accompanied by the brachytherapy, either before or after the irradiation. The length of barotrauma must be taken into account to determine the overall length of the radioactive seed. Often, only the stent is visualized fluoroscopically. One must add the barotrauma length proximal and distal to the stent to define the CTL, assuming that the other vascular intervention (angioplasty and/or atherectomy) is contained within the stented length. To determine the required radioactive seed length, one must define the planning target length (PTL), which is the CTL plus additional margins to account for the longitudinal source movement and the uncertainty in target localization. The source movement refers to longitudinal displacement of the source and the catheter relative to the vessel. Preliminary analysis at Scripps Clinic shows that the magnitude of source/catheter displacement could range up to 5.4 mm. The uncertainty in target localization refers to the fact that the visual estimation of proximal and distal ends is not absolute, and this uncertainty is estimated on the order of 1–5 mm. The schematic for PTL is shown in Fig. 3. Figure 4 presents an example of how the source length is determined using the above concept. Because the GFX™ stent was used, a 2-mm margin was added to the proximal and distal stent edges to define CTL. In practice, defining the proximal and distal ends of CTL with coronary angiography is not trivial, due to the following factors: (1) difficulty in defining a reference coordinate because the position
Barotrauma due to stent deployment
● H. GIAP et al.
1023
Table 1. Review of nine commonly used stents and their corresponding barotrauma lengths Stent deployment pressure (atm)
Balloon length (mm)
Barotrauma length (mm)
8, 13, 18, 23, 28, 38 9, 16, 25, 32
17, 24, 32 13, 17 12, 16, 22, 28, 34 20, 30 11.5, 17.2, 21.9, 26.8, 30.5, 41.2 11.5, 17.2, 21.9, 27.3, 30.5, 41.2 13, 20, 29, 36
1.0 1.0 2.0 2.5 1.75, 2.1, 1.95, 1.9, 1,25, 1.6 1.75, 2.10, 1.95, 2.15, 1.25, 1.60 2.0
2.5, 3.0, 3.5, 4.0
9, 16, 25, 32
13, 20, 29, 36
2.0
7.0
2.5, 3.0, 3.5, 4.0
16, 25, 32
17, 26, 32
0.5
7.0
Stent (Manufacturer)
Stent diameter (mm)
Stent length (mm)
Crown™ (J&J, Cordis) Mini-Crown™ (J&J, Cordis) GFX™ (AVE) Multi-Link™ (ACS) Multi-Link OTW Duet™ (ACS) Multi-Link Rx Duet™ (ACS) NIR Primo™ (BSC/SciMed) NIR on Ranger™ (BSC/ SciMed) NIR on Ranger with SOX™ (BSC/SciMed)
3.0, 3.5, 4.0 2.25, 2.5, 2.75, 3.0, 3.25 3.0, 3.5, 4.0 3.0, 3.5
15, 22, 30 11, 15 8, 12, 18, 24, 30 15, 25
3.0, 3.5, 3.75
8, 13, 18, 23, 28, 38
3.0, 3.5, 3.75 2.5, 3.0, 3.5, 4.0
of the image intensifier varies at different steps; (2) the process of coronary interventions (angioplasty, stent, radiation) is applied in sequence; and (3) cardiac vessels are constantly moving. It is recommended that a branching vessel, which is most proximal to the intervened target vessel during a contrast phase, be used as the reference point. CONCLUSION In this study, the effect of barotrauma due to stent deployment was investigated and tabulated for several commonly used commercial stents. The range of barotrauma for the stents reviewed in this study is from 0.5 to 2.5 mm, and the average is 1.7 mm. This is approximately one-half of a seed of currently used Ir-192 (192Ir) seed ribbon, which has an active seed length of 3-mm and 1-mm interseed spacing (Best Industries, Springfield, VA). It is recommended that the length of barotrauma
Fig. 3. Definition of PTL for endovascular brachytherapy to prevent restenosis.
7.0 10.0 9.0 6.0–7.0 6.0 6.0 7.0
should be determined specifically for each stent, and be included in the CTL. The CTL is then converted into the treatment length as described previously and as shown in Fig. 3. The accurate specification of treatment length serves several important purposes. First, by considering different factors constituting the treatment length, one can provide adequate treatment margins to minimize edge failure or to avoid “geographic miss”; therefore, one can further improve the effect of EVBT in reducing restenosis. Second, it assures treatment consistency among practitioners, especially for multi-institutional clinical trials.
Fig. 4. Example of incorporating barotrauma length into CTL in endovascular brachytherapy.
1024
I. J. Radiation Oncology
●
Biology
●
Physics
Volume 47, Number 4, 2000
REFERENCES 1. Popma JJ, Califf RM, Topol EJ. Clinical trials of restenosis after coronary angioplasty. Circulation 1991;84:1426 –1436. 2. Palmaz JC, Sibbit RR, Reuter SR, et al. Expandable intraluminal graft: A preliminary study. Radiology 1985;156:69 –72. 3. Rousseua H, Puel J, Joffre F, et al. Self-expanding endovascular prosthesis: An experimental study. Radiology 1987;164: 709 –714. 4. Serruys PW, Strauss BH, Beatt KJ, et al. Angiographic follow-up after placement of a self-expanding coronary artery stent. N Engl J Med 1991;324:13–17. 5. Schatz RA, Baim DS, Leon M, et al. Clinical experience with Palmaz-Schatz coronary stent. Initial results of a multicenter study. Circulation 1991;83:148 –161. 6. Teirstein PS, Massullo V, Jani S, et al. Catheter-based radiotherapy to inhibit restenosis after coronary stenting. N Engl J Med 1997;336:1697–1703.
7. Raizner AE. PREVENT and INHIBIT Trials. Proceedings to Scripps Clinic Third Annual Symposium on Radiotherapy to Reduce Restenosis. January 15–16, 1999. 8. Hehrlein C. IRIS Trial. Proceedings to the Scripps Clinic Third Annual Symposium on Radiotherapy to Reduce Restenosis. January 15–16, 1999. 9. Giap H, Massullo V, Jani S, et al. Proposed definition of treatment volume in endovascular brachytherapy. Proceedings to the Scripps Clinic Third Annual Symposium on Radiotherapy to Reduce Restenosis. January 15–16, 1999. 10. Tripuraneni P, Giap H, et al. Definition of treatment length in endovascular brachytherapy for restenosis prevention. Cardiac Catheterization Intervention (In press). 11. Kutryk MJB, Serruys PW. Coronary stenting: current perspectives. Chapter 1: Overview. London: Martin Dunitz; 1999.
PII S0360-3016(00)00515-0
CLINICAL INVESTIGATION
Benign Disease
BAROTRAUMA DUE TO STENT DEPLOYMENT IN ENDOVASCULAR BRACHYTHERAPY FOR RESTENOSIS PREVENTION HUAN GIAP, M.D., PH.D.,* PAUL TEIRSTEIN, M.D.,† VINCENT MASSULLO, M.D.,* PRABHAKAR TRIPURANENI, M.D., F.A.C.R.*
AND
Divisions of *Radiation Oncology and †Interventional Cardiology, Scripps Clinic, La Jolla, CA Purpose: In this study, the effect of barotrauma due to stent deployment is investigated for several commonly used commercial stents used in endovascular brachytherapy for restenosis prevention. Methods and Materials: Restenosis due to intimal hyperplasia can occur anywhere along the clinical target volume, which is defined as the length of vessel receiving intervention or injury. The injury may be due to angioplasty, atherectomy (tissue removing), stenting, and stent deployment. Manufacturer specifications for several commonly used stents were reviewed and the results were tabulated. Results: The barotrauma length of stents reviewed in this study ranges from 0.5 to 2.5 mm; the average was 1.7 mm. Conclusions: By considering specific barotrauma into the treatment length, one can provide adequate treatment margins to minimize edge failure or to avoid “geographic miss,” which may improve the efficacy of endovascular brachytherapy. © 2000 Elsevier Science Inc. Barotrauma, Stent deployment, Endovascular brachytherapy, Restenosis.
of radioactive sources (endovascular brachytherapy) might prevent restenosis. Experimental studies in animal models have documented the profound effects of endovascular brachytherapy (EVBT) in reducing restenosis following angioplasty and stenting. Early results of several prospective, double-blind, randomized clinical trials are encouraging and confirm the positive results. Within several years, more than a dozen prospective, multicenter, randomized trials have been initiated to test the safety and efficacy of EVBT. This new field involves many specialties with no history of collaboration, and the role of each discipline is still evolving, and remains undefined. There are several wellestablished concepts in radiation therapy that require clarification for cardiologists, interventional radiologists, and vascular surgeons. One of these important concepts is the target definition for EVBT. Current clinical trials in EVBT emphasize the total prescribed dose at a specific radial distance; however, few trials explicitly define the treatment length or specify how a certain length of source train is chosen for treatment. The significance of an adequate treatment margin has been demonstrated recently by observation of local failures at the edge of stent and near the end of the angioplasty balloon (6 – 8). In the Scripps I study, minimal margin was provided, and approximately one-half of reste-
INTRODUCTION There are approximately one million patients undergoing percutaneous transluminal coronary angioplasty (PTCA) annually, and 20 –50% develop re-narrowing of the treated artery (restenosis) within 6 months of the procedure date (1). Initial therapeutic approaches that focused on pharmaceutical agents, mechanical devices (atherectomy), physical devices (stenting), and more recently, gene therapy, have demonstrated limited success. The idea of using a balloon for simultaneous vessel dilation and stent delivery for canine non-coronary vessels was initially introduced by Palmaz et al. in 1985 (2). With the refinement of equipment and new stent design, the application of stent to canine coronary vessels was possible in 1987 (3). By early 1988, 117 self-expanding intravascular stents had been implanted in native coronary arteries or in bypass grafts of 105 patients (4). In 1991, Schatz et al. reported a multicenter study of elective stent placement in native coronary vessels after successful angioplasty in 213 patients, with 299 stents in 230 lesions. The successful delivery of these stents was 93%, and the restenosis rate was 36% (5). Recently, several investigators reported that localized irradiation of the angioplasty site by intraluminal placement
would like to thank the Scripps Clinic medical writer, Marcia Straile, for her excellent support in the writing of this manuscript. H.B.G. is grateful to Jeff Anderson and the Cardiac Cath Lab personnel for their assistance. Accepted for publication 10 February 2000.
Reprint requests to: Huan Giap, M.D., Ph.D., Division of Radiation Oncology, Scripps Clinic, 10666 North Torrey Pines Road, La Jolla, CA 92037. Tel (858) 554-2000; Fax: (858) 554-6082; E-mail: [email protected] Acknowledgments—We would like to acknowledge the unnamed reviewers of this article for their valuable comments. H. B. G. 1021
1022
I. J. Radiation Oncology
●
Biology
●
Physics
Fig. 1. Definition of barotrauma due to stent deployment.
nosis occurred at the stent margin. There are several postulations for the marginal failures, including inadequate length of radioactive source, source movements, inaccurate placement of radioactive source, and barotrauma (9). After angioplasty, a metallic stent is usually placed into the vessel by balloon expansion. The term “barotrauma” used in this paper refers to the injury to the vessel arising from the stent deployment balloon. This study reviews current stent design and estimates the length of barotrauma beyond the stented length. METHODS AND MATERIALS Adequate treatment of a vascular lesion using endovascular brachytherapy requires specification of the clinical target length (CTL), which is defined as the length of vessel receiving intervention or injury (10). This may be due to angioplasty, atherectomy (tissue removing), stenting, and stent deployment. Restenosis due to neointimal hyperplasia can occur anywhere along the CTL. When EVBT is used, the entire length of CTL must be covered by radioactive sources. The length of the balloon used for stent deployment is typically longer the stent itself (Fig. 1). The most proximal and most distal sites of injury constitute the CTL, and this is demonstrated schematically in Fig. 2. Accurate localization of CTL is crucial for successful application of EBVT to prevent restenosis. Current Food and Drug Administration (FDA)-approved stents for coronary intervention are reviewed in Table 1. Nine different stent designs available at Scripps Clinic were reviewed in this study. The stent trade name and
Fig. 2. Definition of CTL for endovascular brachytherapy to prevent restenosis.
Volume 47, Number 4, 2000
corresponding manufacturers are as follows: Palmaz-Schatz Crown™ and Mini-Crown™ (Cordis Corp., Miami, FL), GFX™ (Arterial Vascular Engineering, Santa Rosa, CA), ACS Multi-Link™, ACS Multi-Link OTW Duet™, ACS Multi-Link Rx Duet™ (GUIDANT Advanced Cardiovascular Systems, Temecula, CA), NIR Primo, NIR on Ranger™, NIR on Ranger with SOX™ (Boston Scientific Corp/ SciMed, Maple Grove, MN). The specifications from the manufacturer’s package inserts were reviewed, and the lengths of each stent and balloon were obtained and tabulated in Table 1. Barotrauma length indicates the length of the balloon beyond the stent edge, and this value is half of the difference between the balloon length and the stent length. This calculation of barotrauma length assumes that the proximal and distal extensions of the balloon are equal and that the stent is mounted centrally on the balloon. RESULTS AND DISCUSSION In this study, the mean length of barotrauma beyond the stent margin was 1.7 mm, ranging from 0.5 to 2.5 mm. Some relevant factors in stent design include flexibility, tractability, low-unconstrained profile, radio-opacity, thromboresistance, biocompatibility, reliable expandability, radial strength, circumferential coverage, low surface area, and hydrodynamic compatibility (11). The length of its barotrauma should not determine the merit of the stent. In fact, for most stents, the length of barotrauma is similar and approximately equal to half the length of commonly used brachytherapy seeds. In endovascular brachytherapy, stenting is often accompanied by the brachytherapy, either before or after the irradiation. The length of barotrauma must be taken into account to determine the overall length of the radioactive seed. Often, only the stent is visualized fluoroscopically. One must add the barotrauma length proximal and distal to the stent to define the CTL, assuming that the other vascular intervention (angioplasty and/or atherectomy) is contained within the stented length. To determine the required radioactive seed length, one must define the planning target length (PTL), which is the CTL plus additional margins to account for the longitudinal source movement and the uncertainty in target localization. The source movement refers to longitudinal displacement of the source and the catheter relative to the vessel. Preliminary analysis at Scripps Clinic shows that the magnitude of source/catheter displacement could range up to 5.4 mm. The uncertainty in target localization refers to the fact that the visual estimation of proximal and distal ends is not absolute, and this uncertainty is estimated on the order of 1–5 mm. The schematic for PTL is shown in Fig. 3. Figure 4 presents an example of how the source length is determined using the above concept. Because the GFX™ stent was used, a 2-mm margin was added to the proximal and distal stent edges to define CTL. In practice, defining the proximal and distal ends of CTL with coronary angiography is not trivial, due to the following factors: (1) difficulty in defining a reference coordinate because the position
Barotrauma due to stent deployment
● H. GIAP et al.
1023
Table 1. Review of nine commonly used stents and their corresponding barotrauma lengths Stent deployment pressure (atm)
Balloon length (mm)
Barotrauma length (mm)
8, 13, 18, 23, 28, 38 9, 16, 25, 32
17, 24, 32 13, 17 12, 16, 22, 28, 34 20, 30 11.5, 17.2, 21.9, 26.8, 30.5, 41.2 11.5, 17.2, 21.9, 27.3, 30.5, 41.2 13, 20, 29, 36
1.0 1.0 2.0 2.5 1.75, 2.1, 1.95, 1.9, 1,25, 1.6 1.75, 2.10, 1.95, 2.15, 1.25, 1.60 2.0
2.5, 3.0, 3.5, 4.0
9, 16, 25, 32
13, 20, 29, 36
2.0
7.0
2.5, 3.0, 3.5, 4.0
16, 25, 32
17, 26, 32
0.5
7.0
Stent (Manufacturer)
Stent diameter (mm)
Stent length (mm)
Crown™ (J&J, Cordis) Mini-Crown™ (J&J, Cordis) GFX™ (AVE) Multi-Link™ (ACS) Multi-Link OTW Duet™ (ACS) Multi-Link Rx Duet™ (ACS) NIR Primo™ (BSC/SciMed) NIR on Ranger™ (BSC/ SciMed) NIR on Ranger with SOX™ (BSC/SciMed)
3.0, 3.5, 4.0 2.25, 2.5, 2.75, 3.0, 3.25 3.0, 3.5, 4.0 3.0, 3.5
15, 22, 30 11, 15 8, 12, 18, 24, 30 15, 25
3.0, 3.5, 3.75
8, 13, 18, 23, 28, 38
3.0, 3.5, 3.75 2.5, 3.0, 3.5, 4.0
of the image intensifier varies at different steps; (2) the process of coronary interventions (angioplasty, stent, radiation) is applied in sequence; and (3) cardiac vessels are constantly moving. It is recommended that a branching vessel, which is most proximal to the intervened target vessel during a contrast phase, be used as the reference point. CONCLUSION In this study, the effect of barotrauma due to stent deployment was investigated and tabulated for several commonly used commercial stents. The range of barotrauma for the stents reviewed in this study is from 0.5 to 2.5 mm, and the average is 1.7 mm. This is approximately one-half of a seed of currently used Ir-192 (192Ir) seed ribbon, which has an active seed length of 3-mm and 1-mm interseed spacing (Best Industries, Springfield, VA). It is recommended that the length of barotrauma
Fig. 3. Definition of PTL for endovascular brachytherapy to prevent restenosis.
7.0 10.0 9.0 6.0–7.0 6.0 6.0 7.0
should be determined specifically for each stent, and be included in the CTL. The CTL is then converted into the treatment length as described previously and as shown in Fig. 3. The accurate specification of treatment length serves several important purposes. First, by considering different factors constituting the treatment length, one can provide adequate treatment margins to minimize edge failure or to avoid “geographic miss”; therefore, one can further improve the effect of EVBT in reducing restenosis. Second, it assures treatment consistency among practitioners, especially for multi-institutional clinical trials.
Fig. 4. Example of incorporating barotrauma length into CTL in endovascular brachytherapy.
1024
I. J. Radiation Oncology
●
Biology
●
Physics
Volume 47, Number 4, 2000
REFERENCES 1. Popma JJ, Califf RM, Topol EJ. Clinical trials of restenosis after coronary angioplasty. Circulation 1991;84:1426 –1436. 2. Palmaz JC, Sibbit RR, Reuter SR, et al. Expandable intraluminal graft: A preliminary study. Radiology 1985;156:69 –72. 3. Rousseua H, Puel J, Joffre F, et al. Self-expanding endovascular prosthesis: An experimental study. Radiology 1987;164: 709 –714. 4. Serruys PW, Strauss BH, Beatt KJ, et al. Angiographic follow-up after placement of a self-expanding coronary artery stent. N Engl J Med 1991;324:13–17. 5. Schatz RA, Baim DS, Leon M, et al. Clinical experience with Palmaz-Schatz coronary stent. Initial results of a multicenter study. Circulation 1991;83:148 –161. 6. Teirstein PS, Massullo V, Jani S, et al. Catheter-based radiotherapy to inhibit restenosis after coronary stenting. N Engl J Med 1997;336:1697–1703.
7. Raizner AE. PREVENT and INHIBIT Trials. Proceedings to Scripps Clinic Third Annual Symposium on Radiotherapy to Reduce Restenosis. January 15–16, 1999. 8. Hehrlein C. IRIS Trial. Proceedings to the Scripps Clinic Third Annual Symposium on Radiotherapy to Reduce Restenosis. January 15–16, 1999. 9. Giap H, Massullo V, Jani S, et al. Proposed definition of treatment volume in endovascular brachytherapy. Proceedings to the Scripps Clinic Third Annual Symposium on Radiotherapy to Reduce Restenosis. January 15–16, 1999. 10. Tripuraneni P, Giap H, et al. Definition of treatment length in endovascular brachytherapy for restenosis prevention. Cardiac Catheterization Intervention (In press). 11. Kutryk MJB, Serruys PW. Coronary stenting: current perspectives. Chapter 1: Overview. London: Martin Dunitz; 1999.