• Korean Journal of Radiology
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• v.2 no.3
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• pp.151-158
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• 2001

Objective: To determine the ability of MR imaging to detect the pathological changes occurring in radiofrequency (RF) thermal lesions and to assess its accuracy in revealing the extent of tissue necrosis. Materials and Methods: Using an RF electrode, thermal lesions were created in the livers of 18 rabbits. The procedure involved three phases. In the acute phase, six animals were killed the day after performing thermal ablation with RF energy, and two on day 3. In the subacute and chronic phases, eight rabbits underwent percutaneous hepatic RF ablation. After performing MR imaging, two animals were sacrificed at 1, 2, 4, and 7 weeks after the procedure, and MRpathologic correlation was performed. Results: In the acute phase, the thermal ablation lesions appeared at gross examination as well-circumscribed, necrotic areas, representing early change in the coagulative necrosis seen at microscopic examination. They were hypointense on T2-weighted images, and hyperintense on T1-weighted images. Gadolinium-enhanced MR imaging showed that a thin hyperemic rim surrounded the central coagulative necrosis. In the subacute phase, ablated lesions also showed extensive coagulative necrosis and marked inflammation at microscopic examination. Beyond two weeks, the lesions showed gradual resorption of the necrotic area, with a peripheral fibrovascular rim. The size of lesions measured by MR imaging correlated well with the findings at gross pathologic examination. Conclusion: MR imaging effectively demonstrates the histopathological tissue change occurring after thermal ablation, and accurately determines the extent of the target area.

• Journal of the Korean Society of Radiology
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• v.84 no.5
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• pp.1017-1030
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• 2023

Radiofrequency ablation (RFA) is a non-surgical treatment for symptomatic, benign thyroid nodules. This treatment works by heating and destroying the nodule tissue, which results in reduction of its size and alleviation of the symptoms involved. RFA is indicated for nodules which are confirmed to be benign on two or more cytological or histological examinations, and which result in clinical symptoms requiring medical treatment. It is associated with good short-term outcomes on one-year follow-up; however, 20%-30% of the nodules regrow after more than three years. Therefore, on the basis of long-term follow-up, management of regrowth is key to patient care following RFA. Regrowth is more likely to occur in nodules that are large in size prior to RFA, and in those with high or increased vascularity. Recently, new techniques such as hydrodissection, artery-first ablation, and venous ablation have been introduced to inhibit regrowth. In addition, appropriate criteria for additional RFA should be applied to manage regrowth and prolong its therapeutic effects. RFA is essentially an alternative to surgery; therefore, the ultimate goal of this procedure is to avoid surgery permanently, rather than to achieve temporary effects.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.68-71
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• 2008

Transdermal and topical drug delivery with minimal tissue damage has been an area of vigorous research for a number of years. Our research team has initiated the development of an effective method for delivering drug particles across the skin (transdermal) for systemic circulation, and to localized (topical) areas. The device consists of a micro particle acceleration system based on laser ablation that can be integrated with endoscopic surgical techniques. A layer of micro particles is deposited on the surface of a thin metal foil. The rear side of the foil is irradiated with a laser beam, which generates a shockwave that travels through the foil. When the shockwave reaches the end of the foil, it is reflected as an expansion wave and causes instantaneous deformation of the foil in the opposite direction. Due to this sudden deformation, the microparticles are ejected from the foil at very high speeds, and therefore have sufficient momentum to penetrate soft body tissues. We have demonstrated this by successfully delivering cobalt particles $3\;{\mu}m$ in diameter into gelatin models that represent soft tissue with remarkable penetration depth.

• Journal of Oral Medicine and Pain
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• v.45 no.2
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• pp.44-47
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• 2020

The case of pseudo-aneurysm of internal maxillary artery (IMA) in oral and maxillofacial region is known to be very rare. The etiology of this case was regarded as IMA injury by radiofrequency ablation (RFA) and such incidence was not reported previously. One case of false aneurysm in the IMA was referred from local dental clinic to our department. Left facial swelling was observed with severe trismus immediately after radiofrequency procedure for masseteric nerve block in local dental clinic. Despite of medication and surgical intervention, the swelling did not subside and there was massive bleeding and pulsation on one of the follow ups. The traumatic vascular disorder was suspected and finally diagnosed with angiography and treated by embolization procedure. RFA targeting masseteric nerve or trigeminal ganglion may cause traumatic injury to adjacent anatomic structures such as IMA, resulting in pseudo-aneurysm. Clinicians must be aware of potential damages of RFA. Angiography enables the solid diagnosis for pseudo-aneurysm, and selective embolization can be optimum treatment method.

• Investigative Magnetic Resonance Imaging
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• v.20 no.2
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• pp.132-135
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• 2016

We report the case of a 43-year-old male with both giant left atrial appendage (LAA) aneurysm and drug-refractory atrial fibrillation (AF). The patient was treated with percutaneous electrical isolation of cardiac arrhythmogenic substrate, and has been free of AF symptom over one year. Although the surgical resection of giant LAA aneurysm is mostly used to prevent systemic thromboembolism, we have performed follow-up of the giant LAA aneurysm using cardiac magnetic resonance (CMR) imaging and transesophageal echocardiography (TEE) after the successful catheter ablation of refractory AF. At one-year follow-up CMR, the giant LAA aneurysm showed remarkable enlargement as well as decreased contractility. Additionally, one-year follow-up TEE showed spontaneous echo contrast as an indicator of blood stasis in the giant LAA aneurysm. Those findings of giant LAA aneurysm suggest that the risk of thromboembolism may be high despite termination of AF.

• Archives of Plastic Surgery
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• v.41 no.3
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• pp.225-230
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• 2014

The increased application of the da Vinci robotic platform (Intuitive Surgical Inc.) for microsurgery has led to the development of new adjunctive surgical instrumentation. In microsurgery, the robotic platform can provide high definition $12{\times}-15{\times}$ digital magnification, broader range of motion, fine instrument handling with decreased tremor, reduced surgeon fatigue, and improved surgical productivity. This paper presents novel adjunctive tools that provide enhanced optical magnification, micro-Doppler sensing of vessels down to a 1-mm size, vein mapping capabilities, hydro-dissection, micro-ablation technology (with minimal thermal spread-$CO_2$ laser technology), and confocal microscopy to provide imaging at a cellular level. Microsurgical outcomes from the use of these tools in the management of patients with infertility and chronic groin and testicular pain are reviewed. All these instruments have been adapted for the robotic console and enhance the robot-assisted microsurgery experience. As the popularity of robot-assisted microsurgery grows, so will its breadth of instrumentation.

• Medical Lasers
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• v.9 no.2
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• pp.103-109
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• 2020

Transoral microsurgery has come a long way as a go-to surgical intervention technique for head and neck cancers. This minimally invasive procedure had gained acceptance through comparative clinical studies against radical neck surgical procedures, radiotherapy, and chemotherapy. Laser technology has vastly improved the oncological outcomes of this procedure and brought about an appreciation of transoral laser surgery (TLM) as a mainstay for re-sectioning malignant tumors along the throat. As an established procedure, TLM has undergone several upgrades regarding the different energy devices used for cutting, ablation, and hemostasis. Continued advances in automation have eventually led to surgical robotics, resulting in the emergence of transoral robotic surgery (TORS) as a viable advanced alternative for TLM. Similarly, expansions and enhancements (image-based guidance, fluorescence spectroscopy, and advanced robotic system) have also been investigated as potential upgrades for TORS. This paper reviews a selection of publications on the significant technological advancements to TLM and TORS over the past five years.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.86-90
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• 2001

Modified coaxial-slot antenna for minimally invasive microwave thermal therapy for liver tumor is studied in this paper. Minimally invasive microwave antenna in medicine are applied for hyperthermia for medical treatment for cancer, cardiac catheter ablation for ventricular arrhythmias treatments, microwave treatment of Benign prostatic hypertrophy, and so on. Microwave hyperthermal ablation for liver tumors is expected for enthusiasts as an alternative to curative surgical resection. Tumors have to heated up to 60 degree C to coagulate .cancer cells but less than 100 degree C to avoid evaporation. Temperature dependence of properties of the tissues should be considered for wide range of treatment. Electrical properties of liver tissue were measured for different temperatures. SAR distribution around the antenna into the liver are simulated using Remcom's XFDTD.

• Journal of Chest Surgery
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• v.43 no.2
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• pp.180-183
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• 2010

Submitral left ventricular aneurysm (SMLVA) is a rare disease entity that exclusively occurs in the black population. We herewith report on a surgical case of SMLVA in a 68-year-old male who presented with ventricular tachycardia. He underwent surgical repair under standard hypothermic cardiopulmonary bypass. In the state of apical elevation, a vertical ventriculotomy was made directly over the aneurysm, which was located at the posterobasal aspect of the left ventricle. Radiofrequency ablation was performed on the endocardium all around the neck of the aneurysm and then patch endoaneurysmorrhaphy was carried out with particular care not to injure the mitral valve and subvalvular structure. His postoperative recovery was uneventful. There has been no dysfunction of the mitral valve or recurrence of the ventricular tachycardia at 2 years' follow-up.

• Journal of Chest Surgery
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• v.51 no.4
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• pp.266-272
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• 2018

Background: Limited comparative data are available on the efficacy of cryoablation versus radiofrequency ablation in patients with atrial fibrillation. This study aimed to compare radiofrequency ablation and cryoablation with regard to clinical outcomes and the restoration of sinus rhythm or atrial contractility. Methods: A total of 239 patients who underwent surgical ablation between August 2003 and December 2016 at our institution were included. The patients were divided into 2 groups according to the energy device that was used (group A: n=140, radiofrequency ablator; group B: n=99, cryoablator). Echocardiographic data, overall survival, and major cardiovascular and cerebrovascular event (MACCE)-free survival were compared between the 2 groups. Results: At 1 year of follow-up, the atrial contractility recovery rate was 32.2% (19 of 59) in group A and 48.8% (21 of 44) in group B. In addition, cryoablation was found to be a predictive factor for the recovery of atrial contractility (cryoablation vs. radiofrequency ablation: odds ratio, 2.540; 95% confidence interval, 1.063-6.071; p=0.036). The left ventricular ejection fraction was significantly higher in group B ($53.1%{\pm}11.5%$ vs. $59.1%{\pm}6.3%$, p=0.001). The median follow-up duration was 36 months. The 5-year overall survival rate was $80.1%{\pm}3.6%$ in group A and $92.1%{\pm}2.9%$ in group B (p=0.400). The 5-year MACCE-free survival rate was $70.3%{\pm}4.0%$ in group A and $70.9%{\pm}5.6%$ in group B (p=0.818). Conclusion: Cryoablation was associated with a higher atrial contractility restoration rate and better left ventricular function than radiofrequency ablation. However, no significant relationship was observed between the energy source and overall or MACCE-free survival.