Intravascular diseases are commonly treated by relatively non-invasive techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These therapeutic techniques are well-known in the art and typically involve the use of a balloon catheter with a guide wire, possibly in combination with other intravascular devices. A typical balloon catheter has an elongate shaft with a balloon attached to its distal end and a manifold attached to the proximal end. In use, the balloon catheter is advanced over the guide wire such that the balloon is positioned adjacent a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened.
Vascular restrictions that have been dilated do not always remain open. For example, the restriction may redevelop over a period of time, a phenomenon commonly referred to as restenosis. Various theories have been developed to explain the cause for restenosis. It is commonly believed that restenosis is caused, at least in part, by cellular proliferation over a period of time to such a degree that a stenosis or restriction is reformed in the location of the previously dilated restriction.
Intravascular radiation, including thermal, light and radioactive radiation, has been proposed as a means to prevent or reduce the effects of restenosis. For example, U.S. Pat. No. 4,799,479 to Spears suggests that heating a dilated restriction may prevent gradual restenosis at the dilation site. In addition, U.S. Pat. No. 5,417,653 to Sahota et al. suggests that delivering relatively low energy light, following dictation of a stenosis, may inhibit restenosis. Furthermore, U.S. Pat. No. 5,059,166 to Fischell et al. suggests that intravascular delivery of radioisotopes may be used to decrease the rate of arterial reclosure (i.e., restenosis).
Since the delivery of intravascular radiation may adversely affect otherwise healthy tissue, it is desirable to limit radiation exposure to areas requiring treatment. In addition, it is desirable to uniformly deliver radiation to the treatment site in order to avoid over-exposing some areas and underexposing other areas. Since the human vasculature is rarely linear, it is further desirable to provide for uniform distribution of radiation along vascular paths that are non-linear (i.e., curved). Accordingly, it is desirable to center the radiation source within the vasculature, including linear sections and non-linear sections, in order to uniformly irradiate the surrounding tissue. It is also desirable to maintain patency (i.e., retain a fluid path) across the treatment site while delivering radiation over a prolonged period of time. As such, it is desirable to provide structural support to the vessel at the treatment site while permitting blood perfusion.
Although some prior art references recognize these desirable aspects, the prior art does not disclose a device nor method for providing all of these desirable features in a single, functional and effective device. For example, U.S. Pat. No. 5,484,384 to Fearnot discloses a perfusion balloon catheter that has a central lumen for delivering radiation. However, this device will not adequately center the radiation source if the vasculature is tortuous or otherwise non-linear. Another example is disclosed in European Patent No. 0 688 580 A1 to Verin wherein a device is provided which includes a central radiation delivery lumen that remains centered in both linear and non-linear vessels. However, this device does not provide a means for blood perfusion.