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Michael F Hoey

Publications and source records attributed to Michael F Hoey.

4 recordsLinked to original sources
PubMed2005

Geometry and temperature distribution during radiofrequency tissue ablation: an experimental ex vivo model.

PURPOSE: To investigate the temperature distribution and geometry of lesions created by radiofrequency (RF) tissue ablation. MATERIALS AND METHODS: We developed an ex-vivo thermal model based on the ability of egg whites to coagulate at 62 degrees to 65 degrees C. This property allows us to observe and record the formation of "lesions" created by different commercially available RF generators and probes. RESULTS: The lesions created by the Radionics Cool-Tip RF system were mostly cylindrical or barrel-shaped, while RITA StarBurst XL and StarBurst XLi electrodes produced cone-like or mushroom-shaped lesions. The time required to achieve maximum lesion size was between 3 and 5 minutes in most trials. The formation of lesions stopped when thermodynamic equilibrium was achieved. CONCLUSIONS: The geometry of lesions does not correlate precisely with manufacturer reports, which describe spherical lesions for both RF systems. The 12-minute treatment cycle recommended by company's algorithm may not be necessary because lesion formation was completed and thermodynamic equilibrium was reached significantly earlier. We believe the results of our study may be useful in better understanding the RF ablation process, better planning, and improvement of clinical outcome.

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PubMed2003

Radiofrequency interstitial tissue ablation: wet electrode.

Minimally invasive methods for destroying tissue have been investigated for more than a decade, and growing interest has emerged in small probe or needle ablative techniques. Many energy sources that freeze or heat tissue have been studied. This paper discusses radiofrequency (RF) thermal therapy as delivered by the saline-augmented ("wet" or virtual) electrode. The technique modifies the electric field distribution and the resultant heat deposition within tissues by interstitially infusing a highly conductive electrolyte solution during the application of RF energy. We consider the mechanism of action of the saline-augmented probe, with emphasis on tissue electrical impedance, temperature distributions, and how the fluid circumvents the limitations of standard "dry" probes. If optimized for the particular application, the wet electrode can produce small to large ablation volumes quickly and controllably with a single needle stick. Because there is no desiccation or extremely high temperature, the tissue is not subjected to a phase shift of carbonization, which may reduce post-treatment inflammation and improve healing. The liquid RF electrode will find applications in the interstitial treatment of various tissues, including tumors.

Animals↗
PubMed2003

Estimation of acute blood loss in the anticoagulated rabbit model using 3 modalities of radio frequency energy ablation.

PURPOSE: An anticoagulated animal model was tested to evaluate estimated acute blood loss (EABL) following tissue ablation with 3 modalities of radio frequency (RF) thermal energy. MATERIALS AND METHODS: Four groups of randomly divided rabbits were established. Group 1 (3 control and 3 anticoagulated rabbits) underwent sham treatment (noRF), group 2 (2 control and 7 anticoagulated) received single probe dry RF (dRF) (475 KHz and 5 W for 2 minutes), group 3 (2 control and 7 anticoagulated) received single probe wet RF (wRF) (475 KHz with 14.6% hypertonic saline at 50 W for 40 seconds) and group 4 (3 control and 7 anticoagulated) was treated with vapor RF (vRF) (0.9% normal saline for 10 seconds). Oral warfarin sodium was the anticoagulant. Following a midline incision ablation was performed on the left kidney and liver. Pre-weighed gauze pads were used to collect EABL for a 5-minute observation period after needle probe removal. Temperature data were recorded from the right kidney using fiberoptic thermocouples. Lesions were grossly inspected and measured. RESULTS: Anticoagulation resulted in super anticoagulated animals with an average prothrombin time of almost 140 seconds. EABL was the least from the ablated left kidney for vRF (50 mg), followed by wRF (260 mg), dRF (390 mg) and noRF (1,800 mg). EABL was the least from the liver for vRF (10 mg), followed by wRF (470 mg), dRF (1,260 mg) and noRF (2,680 mg). A greater percent of total ablative time at 10 mm was spent at greater than 50C during wRF and vRF. Measured ablative lesions size was largest following vRF ablation. CONCLUSIONS: The thermal coagulative effects of RF ablation resulted in less bleeding compared with controls in this orally anticoagulated animal model. The novel RF modality vRF is introduced.

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