Intracoronary irradiation: Dose response for the prevention of restenosis in swine

Weinberger, Judah; Amols, Howard; Ennis, Ronald D.; Schwartz, Allan; Wiedermann, J; Marboe, Charles C.

doi:10.1016/s0360-3016(96)00294-5

Cited by 140 publications

(48 citation statements)

References 26 publications

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“…Both phenomena, positive remodeling stimulated by intravascular radiation after balloon angioplasty and different patterns of vascular remodeling (positive, negative, or no remodeling) in nonirradiated coronary segments, have been reported previously. 5,18 -20 Although the stimulatory effect of low-dose radiation on plaque proliferation has been demonstrated in injured animal arteries, 6,7 no enhanced plaque growth was observed in the noninjured edges compared with placebo. Plausible explanations for the PV increase in the noninjured edges of both irradiated and placebo groups would be the nonmeasurable vessel injuries caused by the guiding catheter (ie, deep engagement) during the procedure or the devices that cross coronary segments (guidewires, stents, balloons, IVUS catheter, and the 5F radiation delivery catheter).…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, the potential stimulatory effect of low-dose radiation after injury has been demonstrated in animal studies. 6,7 In consideration that the coronary segments adjacent to the irradiated site will invariably receive a lower dose of radiation to some extent, an important issue remains to be clarified: Does the edge effect also occur in noninjured segments? To address this issue, we (1) assessed the midterm (6 to 8 months) geometrical change of the noninjured edge segments in the irradiated coronary vessels and (2) compared these edge segments with both irradiated segments (IRS) and nonirradiated (sham source), noninjured coronary segments by means of a volumetric 3-D IVUS assessment.…”

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Three-Dimensional Intravascular Ultrasound Assessment of Noninjured Edges of β-Irradiated Coronary Segments

et al. 2000

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Background-The "edge effect," late lumen loss at the margins of the treated segment, has become an important issue in the field of coronary brachytherapy. The aim of the present study was to assess the edge effect in noninjured margins adjacent to the irradiated segments after catheter-based intracoronary ␤-irradiation. Methods and Results-Fifty-three vessels were assessed by means of 3-dimensional intravascular ultrasound after the procedure and at 6-to 8-month follow-up. Fourteen vessels (placebo group) did not receive radiation (sham source), whereas 39 vessels were irradiated. In the irradiated group, 48 edges (5 mm in length) were identified as noninjured, whereas 18 noninjured edges were selected in the placebo group. We compared the volumetric intravascular ultrasound measurements of the noninjured edges of the irradiated vessels with the fully irradiated nonstented segments (IRS, nϭ27) (26-mm segments received the prescribed 100% isodose) and the noninjured edges of the vessels of the placebo patients. The lumen decreased (6 mm 3 ) in the noninjured edges of the irradiated vessels at follow-up (Pϭ0.001). We observed a similar increase in plaque volume in all segments: noninjured edges of the irradiated group (19.6%), noninjured edges of the placebo group (21.5%), and IRS (21.0%). The total vessel volume increased in the IRS in the 3 groups. No edge segment was subject to repeat revascularization. Conclusions-The edge effect occurs in the noninjured margins of radiation source train in both irradiated and placebo patients. Thus, low-dose radiation may not play an important role in this phenomenon, whereas nonmeasurable device injury may be considered a plausible alternative explanation.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Three-Dimensional Intravascular Ultrasound Assessment of Noninjured Edges of β-Irradiated Coronary Segments

et al. 2000

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“…It has been demonstrated in animal models [3][4][5][6][7] and more recently in clinical studies that intracoronary irradiation significantly reduces restenosis, presumably by inhibiting smooth muscle cell proliferation and neointima formation. Irradiation of human femoral arteries appears to confirm these findings.…”

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Intracoronary Radiation for Prevention of Restenosis

1998

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Background-Intravascular irradiation with ␤-emitters has been proposed for inhibition of restenosis in coronary arteries after balloon angioplasty or stent implantation. Previous studies have shown the effectiveness of ␥-radiation to prevent recurrent restenosis, even in the presence of an implanted stent. The limited range of ␤-particles compared with ␥-radiation, however, opens the question of whether absorption and scattering of ␤-particles by stent struts will cause significant perturbations in the uniformity and magnitude of the radiation dose, which may in turn compromise treatment. Methods and Results-Nine different stents were deployed with a balloon filled with a ␤-emitting radioactive liquid. Dose distributions were measured with Gafchromic film. Stents varied significantly in their absorption of ␤-particles. Some stents, constructed of fine meshed wires, produced minimal dose perturbations. Others, with thicker, high-atomicnumber struts, induced cold spots in the dose distribution adjacent to the wires of Յ35%. Average dose reduction varied from 4% to 14% in the presence of various stents. Conclusions-Radiation strategy may have to be tailored to stent design. Stents that minimally perturb the dose distribution may be deployed before irradiation. Those that significantly alter the radiation dose might be better deployed after irradiation. Dose prescriptions may require modification if such perturbations prove clinically significant. Observed dose perturbations, however, decreased rapidly with increasing distance from the stent, which may mitigate the clinical impact of these findings. This, as well as the effects of stents on ␥-dose distributions, requires further investigation.

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“…The Geneva II trials 19 similarly showed restenosis rates of 28% to 8% for doses ranging from 9 to 18 Gy. Lower doses might not only be subtherapeutic but might paradoxically stimulate neo‐intimal proliferation, 20 , 21 while higher doses might be associated with increased morbidity rates such as aneurysm formation and thrombosis 22 . The issues surrounding the centering debate have been clearly summarized by Raizner 23 …”

Section: Resultsmentioning

confidence: 99%

Wire or coated balloon? Searching for an optimal source for intravascular brachytherapy with β emitters using as an example

Lehmann

King

2003

J Applied Clin Med Phys

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This study identifies basic dosimetric differences between two designs for intravascular brachytherapy (IVBT) in current clinical practice and ongoing trials and their clinical implications within beta emitting systems using P‐32 as an example. The two designs are (i) the wire‐type source, where the radioactive source material is confined to a wirelike structure within the vessel lumen, and (ii) the balloon‐surface source, where the radioactive source material is distributed over a surface area (balloon‐wall) which is brought in close proximity with the vessel wall. Using Monte Carlo simulations with the EGS4 code, the target coverage, the influence of centering errors, and the perturbation of the dose distribution caused by metallic stents have been compared. The radial dose fall‐off in the target region was found to be steeper for balloon surface systems compared with wire systems. The inner lumen wall dose for a balloon surface source was 25% higher than that for a wirelike source (2.5 mm vessel diameter). However, the comparably shallower fall‐off from wire‐type systems is very sensitive to centering uncertainties. A 0.5 mm displacement, for example, will cause the dose to change by a factor of 2 at the inner vessel wall and by a factor of 1.8 at the prescription point. It is shown that the interference from metallic stents is more significant for wire‐type systems than it is for balloon‐surface‐type systems, where double the dose variation beyond the stent at the radial prescription distance may occur. Centering uncertainties dominate the dose perturbation effects for wire‐type systems. Balloon‐surface‐type designs show a more predictable dose distribution that features, however, a higher inner vessel surface dose. Since a direct clinical comparison of systems of both types is not likely, these findings should be considered when interpreting clinical results from treatments with either type of source and, possibly, for future source design. © 2003 American College of Medical Physics. PACS number(s): 87.53.–j, 87.90.+y

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Intracoronary irradiation: Dose response for the prevention of restenosis in swine

Cited by 140 publications

References 26 publications

Three-Dimensional Intravascular Ultrasound Assessment of Noninjured Edges of β-Irradiated Coronary Segments

Three-Dimensional Intravascular Ultrasound Assessment of Noninjured Edges of β-Irradiated Coronary Segments

Intracoronary Radiation for Prevention of Restenosis

Wire or coated balloon? Searching for an optimal source for intravascular brachytherapy with β emitters using as an example

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