Surgery – Instruments – Electrical application
Reexamination Certificate
1999-05-04
2001-12-04
Peffley, Michael (Department: 3739)
Surgery
Instruments
Electrical application
C606S041000, C607S101000, C607S156000
Reexamination Certificate
active
06325796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates, generally, to ablation instrument systems that use electromagnetic energy in the microwave frequencies to ablate internal bodily tissues, and, more particularly, to antenna arrangements and instrument construction techniques that direct the microwave energy in selected directions that are relatively closely contained along the antenna.
2. Description of the Prior Art
Hepatocellular carcinoma (HCC) is one of the most common liver malignancies in the world. Both in Asia and in the West, most HCC tumors emerge in patients with cirrhosis of the liver. In Japan, for example, liver cancer is the third most common cause of cancer death in men after gastric and cancers.
Yearly incidence of HCC in cirrhotic patients reaches 3-5%, and HCC is recognized as being part of the natural history of cirrhosis. In the past few years, owing to the careful follow-up of cirrhotic patients with ultrasonography (US) and serum alpha-fetoprotein assays, an increasing number of HCC lesions have been diagnosed in a preclinical stage. Although early detection of the tumors resulted in increased resectability rate, the number of patients with HCC eligible for surgery has remained relatively low. This is due to the severity of the associated liver cirrhosis (which may unacceptably increase the surgical risk) and to the frequent multifocality of the tumor. The latter is a critical issue since small doughter nodules may accompany the main tumor and go undetected causing early postoperative intrahepatic recurrences.
For patients who are considered ineligible for surgery, several nonsurgical treatments are available, such as percutaneous ethanol injection (PEI), transcatheter arterial chemoembolization (TACE) or a combination of TACE and PEI. The prognosis for patients with unresectable hepatocellular carcinoma (HCC) tumors is extremely poor, however. Even in the case of small nodular lesions detected by US screening, patients receiving no treatment showed a mean 3-year survival rate of only 12%. Among nonsurgical options, Percutaneous Ethanol Injection (PEI) can be considered the treatment of choice for patients with small (3 cm or less in diameter) HCC tumors. Studies in Japan and in Italy demonstrated the possibility of achieving complete alcohol-induced necrosis of such small lesions without adverse effects on the noncancerous liver parenchyma. Moreover, patients treated with PEI showed high long-term survival rates, comparable with those of patients submitted to surgical resection. The greatest drawback of PEI is represented by the difficulty to treat tumors larger than 3 cm. In these cases, alcohol diffusion is incomplete, being impeded by the texture of the tumor. As a result, residual viable neoplastic tissue can be found after treatment, particular along the periphery of the nodule or in portions isolated by septa.
Transcatheter Arterial Chemoembolization (TACE), most frequently performed by intraarterially injecting an infusion of antineoplastic agents mixed with iodized oil (Lipidol), has been extensively used in the treatment of large HCC tumors. However, although massive tumor necrosis can be demonstrated in most cases, a complete necrosis of the tumor has rarely been achieved with TACE, since residual tumor can be found in a noneligible number of the treated lesions. Indeed, TACE was found mostly effective in nodules less than 4 cm in diameter, with a thick tumor capsule.
Even if PEI or TACE can be effective for small tumors, there are still some patients with HCC who are not good candidates for resection, PEI or TACE because of poor hepatic reserve, poor vascularity, or the large size of the HCC. In these instances, microwave coagulonecrotic therapy may be employed as an alternative, the efficacy of which has been shown in several studies. Sato M. et al.,
Two Long-Term Survivors After Microwave Coagulation Therapy For Hepatocellular Carcinoma: A Case Report
, PEPATOGASTROENTEROLOGY, July (1996) 43(10):1035-1039; Sato M. et al.,
Microwave Coagulation Therapy For Hepatocellular Carcinom
, GASTROENTEROLOGY, May (1996) 110(5):1507-1514.
This coagulonecrotic technique consists of using microwave energy to the tumor cells to increase their temperature to around 55 to 60° C. Originally, a conventional microwave applicator was applied directly to the surface of the liver proximate the tumor cells. Such surface applications were necessary for these ablation catheters since the conventional microwave antennas were generally too diametrically large to be position inside the highly vascularized liver. Accordingly, the primary drawback of this surface application approach is that the tumor cells are not always within the penetration depth of the microwave energy.
In recent years, microwave needle antennas have been developed as a new option for destruction of unresectable HCCs. Using laparotomy, laparoscopy or through percutaneous methods, a relatively small diameter needle antenna may be punctured into the liver to ablate tumor cells from within the liver. This technique has been proven useful for penetrating this highly vascularized organ without causing excessive bleeding. The penetrations sites into the targeted tumor, however, must still be estimated.
Accordingly, there is a need for microwave coagulation therapy which can be more accurately applied within an organ.
SUMMARY OF THE INVENTION
The present invention provides a microwave ablation assembly including an elongated probe having a proximal access end and an opposite distal penetration end adapted to penetrate into bio-tissue. The probe further defines an insert passage extending therethrough from the access end to the penetration end thereof. A coaxial transmission line includes an inner conductor and an outer conductor separated by a dielectric material medium. A proximal end of the transmission line is coupled to a microwave energy source. The ablation assembly further includes an antenna device coupled to the transmission line for generating an electric field sufficiently strong to cause tissue ablation. The antenna device and the transmission line each have a transverse cross-sectional dimension adapted for sliding receipt through the insert passage while the elongated probe is positioned in the bio-tissue. Such sliding receipt occurs until the antenna device is advanced to a position beyond the penetration end and further into the bio-tissue.
Preferably, the antenna device is integrally formed by removing a portion of the outer conductor to expose a portion of the dielectric material medium. Thus, the transverse cross-sectional dimension of the antenna device is substantially equal or smaller than that of the transmission line. In one embodiment, the transverse cross-sectional dimension of dielectric material medium and that of the insert passage cooperate to prevent the outer conductor from extending through the insert passage. In this arrangement, a distal end of the outer conductor is adapted to electrically couple to the elongated probe proximate the access end of the elongated probe such that the probe functions as a shield for the transmission line.
In another arrangement, the outer conductor is provided by a conductive sleeve which is electrically coupled to the elongated probe prior. The dielectric material medium and the inner conductor are adapted for sliding receipt in the conductive sleeve and the insert passage of the probe as a unit to advance and retract the antenna device.
In still another embodiment, a microwave ablation assembly is provided for insertion through an insert passage of an elongated metallic biopsy needle having a penetration end adapted to penetrate into bio-tissue. The ablation assembly includes a coaxial transmission line including an inner conductor and an outer conductor separated by a dielectric material medium. An antenna device is coupled to the transmission line for generating an electric field sufficiently strong to cause tissue ablation. The antenna device and the transmission line each having a transverse cross-sectio
Berube Dany
Bush M. Elizabeth
AFx Inc.
Beyer Weaver & Thomas
Peffley Michael
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