Low-energy X-radiation for prevention of restenosis results in localized inhibition of V79 fibroblast cell proliferation

Local delivery of high-energy ionizing radiation by using 3 or 3 emitters to injured vessels demonstrated inhibition of cell proliferation (CP) and neointima formation. Low-energy ('soft’) X-radiation (LEXR) offers logistic and safety advantages over the use of disposable radioisotopes. This study evaluated the efficacy of LEXR in penetration and inhibition of CP at doses similar to those prescribed for the use of radioisotopes for prevention of restenosis. Serial measurements in an ion chamber detected the attenuation of LEXR using potentials of 17 and 40 kV at a distance of 17 cm of air through 0-10 mm depths of serum-containing tissue culture medium. The effect of inhibition on CP was determined by exposing V79 fibroblasts to a potential of 17 kV in order to deliver a prescribed dose of 13 Gy at a dose rate of 2.17 Gy/min to the surface of the cells. Complete inhibition of CP at a height of 0.00 mm occurred with 13 Gy; however, a 50% attenuation of the dose was measured at a medium depth of 1.22 mm and was associated with a reduction of 60% of the CP. LEXR demonstrated an ability to inhibit CP at doses equivalent to those used in techniques involving 3 and 3 irradiation. Under such conditions, the dose gradient is too high, especially for large vessels. However, a catheter-based LEXR that could be inserted into the artery with the capability of varying effective energy would be ideal for intravascular applications.