Dose perturbation caused by stents: experiments with a model 90Sr/90Y source.
OBJECTIVE
Biological effects of intravascular brachytherapy are very sensitive to discrepancies between the prescription and the applied dose. If brachytherapy is aimed at in-stent restenosis, shielding and shadowing effects of metallic stents may change the dose distribution relative to that produced by the bare source. The development of new generations of stents inspired us to a new experimental study in this field. The effect was studied for 14 stents which we have recently encountered in clinical practice.


METHODS
The model source was a continuous 20-mm column of (90)Sr/(90)Y solution sealed in a 1-mm-I.D. Plexiglas capillary. The dose distribution in the Plexiglas phantom was mapped using GafChromic MD-55-2 film. The stent masses varied from 2.5 to 25 mg; the strut thicknesses, from 0.075 to 0.15 mm; and the atomic numbers of stent materials, from 24 (Cr) to 79 (Au).


RESULTS
Dose perturbations depend on a variety of stent features. Local reduction of the mean dose rates near the reference distance (r(0) = 2 mm) varied from 11% to 47%. No simple correlation was found between these data and stent characteristics, but it seems that the atomic number of the stent material is less important than the strut thickness and mesh density.


CONCLUSIONS
The results provide a warning that clinical indications for in-stent radiation therapy must always be confronted with another aspect of the patient's history: the kind of implanted stent. Intravascular brachytherapy using pure beta sources may be recommended only for patients "wearing" light, thin-strut stents. The presence of thick-strut stents is a contraindication for this modality, due to excessive dose perturbation.
Wilczek
Krzysztof
K
The Silesian Center for Heart Diseases, 3rd Chair and Clinical Hospital for Heart Diseases, Medical University of Silesia, 41-800 Zabrze, Szpitalna 2, Poland.
Petelenz
Barbara
B
Strzała
Alicja
A
Marczewska
Barbara
B
Traczyk
Marek
M
Poloński
Lech
L
D015906:Angioplasty, Balloon, Coronary / Q000009:adverse effects / Q000295:instrumentation*; D000818:Animals; D001918:Brachytherapy / Q000379:methods*; D023903:Coronary Restenosis / Q000209:etiology / Q000532:radiotherapy*; D006801:Humans; D008422:Materials Testing; D011474:Prosthesis Design; D011829:Radiation Dosage; D015607:Stents; D013326:Strontium Radioisotopes; D015021:Yttrium Radioisotopes
D013326:Strontium Radioisotopes; D015021:Yttrium Radioisotopes