Thermal Ablation Treatment Research Articles

Efficacy of point-of-care thermal ablation among high-risk human papillomavirus positive women in China.

Thermal ablation is a point-of-care ablative treatment technique for cervical intraepithelial neoplasia (CIN). However, limited information is available about its efficacy in low- and middle-income countries. We evaluated the efficacy of thermal ablation in treatment of CIN detected through high-risk human papillomavirus (HPV) screening in China. Women positive on high-risk HPV and having colposcopically suspected lesions eligible for ablation underwent colposcopy, biopsy and thermal ablation in one visit. Women ineligible were recalled for large loop excision of transformation zone (LLETZ) when histopathology results were high-grade CIN. Posttreatment follow-up at 6 months or more was with HPV test and cytology followed by colposcopy and biopsy for HPV and/or cytology-positive women. Cure was defined as either negative cytology and HPV test or absence of histopathology proved CIN in any positive women. Of total 218 HPV-positive women treated with thermal ablation (n = 170) or LLETZ (n = 48), 196 reported for follow-up evaluation. For women with histologically confirmed CIN at baseline (thermal ablation-104; LLETZ-38), cure rates were 84.6% for thermal ablation and 86.8% for LLETZ. Cure rates after thermal ablation were 90.3% for CIN grade one (CIN1) and 76.2% for CIN grade two or worse (CIN2+). HPV clearance rate was 80.4% in women undergoing thermal ablation, which was lower for HPV16/18 compared to other oncogenic types (67.6% vs 85.7%). HPV test had a negative predictive value (NPV) of 98.7% to detect CIN2+ at follow-up and the positive predictive value (PPV) was 40.4%. Thermal ablation is effective to treat CIN as well as to clear the high-risk HPV infection. HPV test has high PPV and NPV in following up patients posttreatment.

Heat-induced thrombosis extension after endovenous laser ablation: a clinical case

Endothermal heat-induced thrombosis (EHIT) is a complication of endovenous thermal ablation in treatment of varicose veins. Existing classifications do not account for the length of thrombus extension floating in the deep venous system. While the risk of extension is minor, the consequences can be baleful.Aim. To report a rare clinical case of endothermal heat-induced thrombosis extension formed in spite of ongoing anticoagulant treatment in a patient with endovenous laser ablation.Results. A 39 years-old man with endovenous laser ablation of the right great saphenous vein had class 2 EHIT with 1.92 cm length on the next day after surgery. Rivaroxaban was prescribed at a dose of 15 mg 2 times a day. EHIT extension above the inguinal ligament occurred on the 15th day after surgery, despite oral anticoagulant treatment. Open thrombectomy with high ligation was ordered. Postoperative period without complications. Preoperative Caprini score was 6 (varicose veins, BMI> 25 kg/m2 , minor surgery, personal history of venous thromboembolism (VTE)).Conclusion. The reported clinical case illustrates that both the choice of treatment strategy and follow-up of patients with EHIT need to account for the combined risk of embolism with existing EHIT and potential thrombus extension with subsequent massive embolism.

TACE-Sorafenib With Thermal Ablation Has Survival Benefits in Patients With Huge Unresectable Hepatocellular Carcinoma.

PurposeTo investigate the effectiveness and safety of transarterial chemoembolization (TACE) combined with sorafenib and thermal ablation in patients with huge hepatocellular carcinoma (HCC).Materials and MethodsThis retrospective study examined 50 patients with huge unresectable HCC treated from January 2009 to December 2015. Among them, 28 cases received TACE-sorafenib treatment (TACE-sorafenib group), and 22 cases received TACE-sorafenib plus thermal ablation treatment (TACE-sorafenib-thermal ablation group). The Overall survival (OS), progression-free survival (PFS), and adverse events (AEs) were compared.ResultsThe median follow-up was 13.5 months (ranges 4.2 to 96.7 months). The median OS was significantly longer in the TACE-sorafenib-thermal ablation group than that in the TACE-sorafenib group (20.8 vs. 10.4 months, P=0.003). The median PFS of the ablation and no ablation groups were 4.3 vs. 7.1 months (P=0.546). The treatment modality was an independent predictor of OS (P=0.004). There were no notable drug-related high grade adverse events or permanent adverse sequelae.ConclusionTACE-sorafenib-thermal ablation provided extended OS to patients with huge unresectable HCC and could be a better choice than TACE-sorafenib.

Acoustic streaming and thermosensitive liposomes for drug delivery into hepatocellular carcinoma tumor adjacent to major hepatic veins; an acoustics–thermal–fluid-mass transport coupling model

While researchers have focused on thermal ablation techniques for the treatment of hepatocellular carcinoma tumors for patients who are not candidates for surgical resection, the treatment is still challenging because of disease recurrence after thermal ablation treatment, particularly for tumors that are close to the major blood vessels of liver. Meanwhile, chemotherapy has received less attention because of its low efficacy and adverse side effects. Herein, using an acoustics-thermal-fluid-mass transport coupling model, we present a novel drug delivery system based on the use of acoustic waves and temperature-sensitive liposomes (TSL). Simulation involves solving the acoustic, bioheat, fluid flow and mass transfer equations. The acoustic streaming effect is also considered in this modeling. The main idea behind the proposed system is the simultaneous use of thermal and hydrodynamic effects of acoustic waves for drug delivery in a TSL-based system. HIFU-induced mild hyperthermia allows drug release and acoustic streaming pushes TSL particles from the vessel wall to the target area. To investigate the effects of using acoustics and liposomes, four different systems, including without-acoustic-without-liposome, with-acoustic-without-liposome, without-acoustic-with-liposome and with-acoustic-with-liposome, have been studied. Also, the effect of TSL particle size and acoustic frequency has been investigated. We found that a with-acoustic-with-liposome system can achieve targeted drug delivery by reducing chemotherapy adverse side effects and enhancing drug delivery to the target area. The results show that using such a system, the effective drug penetration into the tissue increased by 56% compared to conventional drug delivery. In addition, the results of the parametric study show that increasing the acoustic frequency in this method results in improved drug delivery. The study of TSL size also indicates that for TSL particles with the same drug-carrying capacity, smaller TSLs perform better.

Genomic DNA methylation profiling indicates immune response following thermal ablation treatment for HBV-associated hepatocellular carcinoma.

Hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) is the most common type of liver cancer in China. Thermal ablation is one of the main strategies for HCC treatment. However, few studies have investigated the properties of the immune response following thermal ablation thus far. In the present study, five subjects with HBV-associated HCC were recruited from The Beijing Youan Hospital. Peripheral blood mononuclear cells (PBMCs) were collected at three time points: Prior to thermal ablation (PR), 1–3 days post-ablation (P1) and 5–7 days post-ablation (P7). An Illumina 850K methylation microarray was employed to determine the DNA methylation profile of each sample. Data were analyzed using different methylation probes with the Bioconductor package in R. Following annotation of different methylation CG sites (CGs), the associated genes were subjected to an Ingenuity Pathway Analysis. A total of 3,000 significantly different CGs (adjusted P<0.05; |log(fold-change)|>0.5) were identified within the PR, P1 and P7 time points. Of these, 744 (24.8%) sites increased between the PR and P1 time points but gradually decreased at the P7 time point. The remaining 2,256 (75.2%) sites decreased between the PR and P1 time points gradually increased at the P7 time point. Following gene annotation of different CGs on the promoter, signaling pathways analysis demonstrated that ‘p70S6K signaling’, ‘CXCR4 signaling’, ‘dendritic cell maturation’, ‘production of nitric oxide and reactive oxygen species in macrophages’ pathways were activated at the P7 time point. The present study suggested that PBMC DNA methylation had changed soon after thermal ablation for subjects with HBV-associated HCC, and systemic immune responses were activated, particularly at the P7 time point.

4D Flow MR Imaging to Improve Microwave Ablation Prediction Models: A Feasibility Study in an In Vivo Porcine Liver

PurposeTo characterize the effect of hepatic vessel flow using 4-dimensional (4D) flow magnetic resonance (MR) imaging and correlate their effect on microwave ablation volumes in an in vivo non-cirrhotic porcine liver model. Materials and MethodsMicrowave ablation antennas were placed under ultrasound guidance in each liver lobe of swine (n = 3 in each animal) for a total of 9 ablations. Pre- and post-ablation 4D flow MR imaging was acquired to quantify flow changes in the hepatic vasculature. Flow measurements, along with encompassed vessel size and vessel-antenna spacing, were then correlated with final ablation volume from segmented MR images. ResultsThe linear regression model demonstrated that the preablation measurement of encompassed hepatic vein size (β = –0.80 ± 0.25, 95% confidence interval [CI] –1.15 to –0.22; P = .02) was significantly correlated to final ablation zone volume. The addition of hepatic vein flow rate found via 4D flow MRI (β = –0.83 ± 0.65, 95% CI –2.50 to 0.84; P = .26), and distance from antenna to hepatic vein (β = 0.26 ± 0.26, 95% CI –0.40 to 0.92; P = .36) improved the model accuracy but not significantly so (multivariate adjusted R2 = 0.70 vs univariate (vessel size) adjusted R2 = 0.63, P = .24). ConclusionsHepatic vein size in an encompassed ablation zone was found to be significantly correlated with final ablation zone volume. Although the univariate 4D flow MR imaging-acquired measurements alone were not found to be statistically significant, its addition to hepatic vein size improved the accuracy of the ablation volume regression model. Pre-ablation 4D flow MR imaging of the liver may assist in prospectively optimizing thermal ablation treatment.

3:09 PM Abstract No. 128 Development of real-time optical image-assessed thermal ablation of hepatic tumor

To investigate the feasibility of using indocyanine green (ICG)-based optical imaging to instantly assess the effective radiofrequency ablation (RFA) on VX2 tumor cells, towards the development of intratumoral real-time optical imaging-guided RFA of larger tumors. We first optimized the uptake characteristics of a clinically applicable optical contrast, indocyanine green (ICG), by VX2 tumor cells. 1×104 VX2 cells in each of different cell groups were treated with various ICG concentrations from 0 to 125 μg/mL, over incubation times from 0 min to 48 hours. Then, in comparison to ICG solution-only, ICG-labeled VX2 cells were treated by thermal ablation at 80 °C for 30 minutes. ICG in cells were subsequently qualitatively and quantitatively evaluated by fluorescence microscopy and optical imaging. The optimization of the ICG concentration demonstrated a linear increase of fluorescent signal intensities (SI), with the peak SI at 100 μg/mL of ICG, starting at the time point of 24 hours post-ICG labeling. Both the fluorescent SIs of ICG-only and ICG-labeled VX2 cell groups were significantly decreased after the thermal ablation treatment (For ICG solution: average SI pretreatment vs. SI posttreatment = 11075.2 ± 1060.9 count vs. 4681.1 ± 442.1 count, P <0.001; and for ICG-labeled VX2 cells: 926.2 ± 197.1 count vs. 301.4 ± 53.9 count, P <0.001). This study demonstrated the feasibility of using indocyanine green (ICG)-based optical imaging to evaluate the instant treatment effect of thermal ablation on VX2 tumor cells, which has encouraged the further on-going studies for developing the new interventional molecular imaging technique to ensure the complete removal of larger tumors during a single RFA session.

Systematic review of endoscopy ultrasound-guided thermal ablation treatment for pancreatic cancer.

The development of curvilinear-array EUS and EUS-guided fine-needle aspiration (EUS-FNA) has led these approaches to become interventional procedures rather than purely diagnostic, as a minimally invasive antitumor therapeutic alternative to radiological and surgical treatments. The possibility to accurately position needle devices and to reach a deep target like the pancreas gland under real-time imaging guidance has expanded the use of EUS to ablate tumors. Currently, a variety of probes specifically designed for EUS ablation are available, including radiofrequency, hybrid cryothermal ablation (combining radiofrequency with cryotechnology), photodynamic therapy, and laser ablation. To date, several studies have demonstrated the safety and feasibility of these ablation techniques in the pancreatic setting, but only a few small series on pancreatic thermal ablation under EUS guidance are available. EUS-guided thermal ablation is primarily used for pancreatic cancer. It is well suited to this disease because of its superior anatomical access compared with other imaging modalities and the dismal prognosis despite improvements in chemoradiotherapy and surgery in the management of pancreatic cancer. Other targets are pancreatic neuroendocrine tumors and pancreatic cystic neoplasms, which are curable by surgical resection, but some patients are poor surgical candidates or prefer conservative management. This is a literature review of previously published clinical studies on EUS-guided thermal ablative therapies. Data on the long-term efficacy of EUS-guided antitumor thermal ablation therapy and large prospective randomized studies are still needed to confirm the real clinical benefits of these techniques for the management of pancreatic neoplasms.

Fast computation of soft tissue thermal response under deformation based on fast explicit dynamics finite element algorithm for surgical simulation

Background and objectivesDuring thermal heating surgical procedures such as electrosurgery, thermal ablative treatment and hyperthermia, soft tissue deformation due to surgical tool-tissue interaction and patient movement can affect the distribution of thermal energy induced. Soft tissue temperature must be obtained from the deformed tissue for precise delivery of thermal energy. However, the classical Pennes bio-heat transfer model can handle only the static non-moving state of tissue. In addition, in order to enable a surgeon to visualise the simulated results immediately, the solution procedure must be suitable for real-time thermal applications. MethodsThis paper presents a formulation of bio-heat transfer under the effect of soft tissue deformation for fast or near real-time tissue temperature prediction, based on fast explicit dynamics finite element algorithm (FED-FEM) for transient heat transfer. The proposed thermal analysis under deformation is achieved by transformation of the unknown deformed tissue state to the known initial static state via a mapping function. The appropriateness and effectiveness of the proposed formulation are evaluated on a realistic virtual human liver model with blood vessels to demonstrate a clinically relevant scenario of thermal ablation of hepatic cancer. ResultsFor numerical accuracy, the proposed formulation can achieve a typical 10−3 level of normalised relative error at nodes and between 10−4 and 10−5 level of total errors for the simulation, by comparing solutions against the commercial finite element analysis package. For computation time, the proposed formulation under tissue deformation with anisotropic temperature-dependent properties consumes 2.518 × 10−4 ms for one element thermal loads computation, compared to 2.237 × 10−4 ms for the formulation without deformation which is 0.89 times of the former. Comparisons with three other formulations for isotropic and temperature-independent properties are also presented. ConclusionsCompared to conventional methods focusing on numerical accuracy, convergence and stability, the proposed formulation focuses on computational performance for fast tissue thermal analysis. Compared to the classical Pennes model that handles only the static state of tissue, the proposed formulation can achieve fast thermal analysis on deformed states of tissue and can be applied in addition to tissue deformable models for non-linear heating analysis at even large deformation of soft tissue, leading to great translational potential in dynamic tissue temperature analysis and thermal dosimetry computation for computer-integrated medical education and personalised treatment.

Acceptability and safety of thermal ablation for the treatment of precancerous cervical lesions in Honduras.

ObjectiveTo evaluate the acceptability and safety of thermal ablation (TA) for the treatment of precancerous cervical lesions in women in Honduras.MethodsHuman papillomavirus (HPV) and visual inspection with acetic acid (VIA) screen‐positive eligible women received TA. After treatment, women rated the level of pain experienced during treatment using the Wong‐Baker FACES® pain‐rating scale from 0 to 10. Short‐term safety outcomes that could require medical attention were assessed one month after treatment.ResultsA total of 319 women received TA treatment. The average pain rating was 2.5 (95% CI: 2.3–2.8), and 85% rated their pain levels as less than 6. No significant differences in low (below 6) or high (6 and above) pain were found by age or number of biopsies performed, but there was a significant difference by the number of TA applications (P < 0.01). When asked if they would recommend this treatment, all women said they would. At the one‐month follow‐up visit, the most common reported discomforts were bleeding (10%) and cramping (8.4%); 11 women reported severe lower abdominal pain, and none required medical attention.ConclusionsTA is safe and acceptable to patients as a treatment option for precancerous cervical lesions in low‐resource settings.

Real-time computation of bio-heat transfer in the fast explicit dynamics finite element algorithm (FED-FEM) framework

Real-time analysis of bio-heat transfer is very beneficial in improving clinical outcomes of hyperthermia and thermal ablative treatments but challenging to achieve due to large computational costs. This paper presents a fast numerical algorithm well suited for real-time solutions of bio-heat transfer, and it achieves real-time computation via the (i) computationally efficient explicit dynamics in the temporal domain, (ii) element-level thermal load computation, (iii) computationally efficient finite elements, (iv) explicit formulation for unknown nodal temperature, and (v) pre-computation of constant simulation matrices and parameters, all of which lead to a significant reduction in computation time for fast run-time computation. The proposed methodology considers temperature-dependent thermal properties for nonlinear characteristics of bio-heat transfer in soft tissue. Utilizing a parallel execution, the proposed method achieves computation time reduction of 107.71 and 274.57 times compared to those of with and without parallelization of the commercial finite element codes if temperature-dependent thermal properties are considered, and 303.07 and 772.58 times if temperature-independent thermal properties are considered, far exceeding the computational performance of the commercial finite element codes, presenting great potential in real-time predictive analysis of tissue temperature for planning, optimization and evaluation of thermo-therapeutic treatments.

Role of CD200/CD200R Signaling Pathway in Regulation of CD4+T Cell Subsets During Thermal Ablation of Hepatocellular Carcinoma.

BackgroundIn this study, we assessed the role of CD200 and CD200 receptor (CD200R) in regulating CD4+T cell subsets and assessed the therapeutic efficacy of thermal ablation for liver hepatocellular carcinoma (HCC) in rats.Material/MethodsSeventy-eight male C57BL/6 rats were randomly divided into 7 groups: a control group, a model group, a CD200FC group, an anti-CD200R1 mAb group, a thermal ablation group, a thermal ablation+CD200 FC group, and a thermal ablation+anti-CD200R1 mAb group. The levels of CD200, CD200R1, Th1, Th17, and Treg in peripheral blood were detected by flow cytometry. Immunohistochemistry was used to detect CD200, CD200R1, IFN-γ, IL-17, Foxp3 protein expression in tumor tissues.ResultsThe levels of CD200, CD200R1, Th17, and Treg were significantly increased after CD200FC treatment (p<0.05). After treatment with anti-CD200R1 mAb, the levels of CD200, CD200R1, Th17, and Treg decreased and Th1 increased. Compared with the control group, the expression of CD200, CD200R1, IL-17, and Foxp3 in the model group increased significantly, and the expression of IFN-γ decreased significantly (p<0.05). The expression of CD200, CD200R1, IL-17, and Foxp3 was significantly reduced by adding anti-CD200R1 mAb, and the expression of IFN-γ was increased (p<0.05). After the thermal ablation treatment, the proteins continued to decrease and the expression of IFN-γ continued to increase.ConclusionsThe CD200/CD200R pathway participates in HCC tumor growth and the expression of CD4+T cell subsets in cancer tissues. Furthermore, thermal ablation treatment inhibited cancer recurrence.

Potential threat of pharyngo-esophageal diverticulum to thermal ablation treatment of thyroid nodule and rapid differential diagnosis through swallow contrast-enhanced ultrasonography

Objective To explore the potential risk of misdiagnosis of pharyngeal esophageal diverticulum(PED) for the treatment of thyroid nodules with thermal ablation and its rapid and effective method of diagnosis. Methods The process of diagnosis and treatment were reviewed on 5 cases of PEDs which had been misdiagnosed as thyroid nodules and recommended for thermal ablation therapy. A comprehensive analysis was carried out for the reasons of misdiagnosis, the timing and clues of the diagnosis as well as the advantage of swallow contrast-enhanced ultrasonography(sCEUS) in achieving rapid and correct diagnosis. Results The lack of recognition and vigilance to the acoustic image of PED were the direct causes of misdiagnosis. Five cases of PED misdiagnosed as thyroid nodules were all discovered by the same chief operator before thermal ablation. They were confirmed through sCEUS and mistreatment by ablation were fortunately avoided, but all true thyroid nodules requiring treatment were safely ablated. Conclusions PED is easily misdiagnosed as thyroid nodule.Improving the recognition and vigilance of the ultrasonic features of PED, strictly implementing the reconfirming ultrasound examination by the chief operator, and promptly conducting sCEUS are sensible measures to quickly correct the diagnosis and prevent wrong ablation of PED. Key words: Contrast-enhanced ultrasonography; Thermal ablation; Pharyngo-esophageal diverticulum; Thyroid nodule; Differential diagnosis

Effects of thermal ablation on Treg/Th17 in hepatocellular carcinoma of mice

The study was aimed to explore the possible function of thermal ablation treatment on T helper 17 (Th17) cells and regulatory T (Treg) cells in transplantation of hepatocellular carcinoma in mice. In total, 60 male C57BL/6 mice were divided into control group, model group, and treat group. Flow cytometry was used to detect the frequency of Th17 and Treg cells in peripheral blood. The levels of interleukin (IL)-17, IL-23, IL-10, and transforming growth factor beta (TGF-β) in serum were detected by enzyme-linked immunosorbent assay (ELISA).The levels of IL-17, RORγt, Foxp3, and TGF-β mRNA in tumor tissues were detected by real-time fluorescence quantitative PCR (qRT-PCR). Compared with the model group, tumor size was significantly decreased after thermal ablation treatment. After treatment, the frequency of Th17 cells in peripheral blood was significantly decreased, while the frequency of Treg cells was profoundly increased ( P &lt; 0.05). The levels of IL-17 and IL-23 were significantly downregulated, while IL-10 and TGF-β levels were upregulated ( P &lt; 0.05). IL-17 and RORγt mRNA levels in tumor tissues were significantly decreased ( P &lt; 0.05), and Foxp3 and TGF-β mRNA levels were significantly increased ( P &lt; 0.05). Thermal ablation treatment plays a positive role in the treatment of hepatoma in mice through affecting the imbalance of Th17/Treg cells.

Potential Threat of Tracheal Diverticulum to Thermal Ablation Treatment of Thyroid Nodule

Potential Threat of Tracheal Diverticulum to Thermal Ablation Treatment of Thyroid Nodule

Monitoring Thermal Ablation via Microwave Tomography: An Ex Vivo Experimental Assessment.

Thermal ablation treatments are gaining a lot of attention in the clinics thanks to their reduced invasiveness and their capability of treating non-surgical patients. The effectiveness of these treatments and their impact in the hospital’s routine would significantly increase if paired with a monitoring technique able to control the evolution of the treated area in real-time. This is particularly relevant in microwave thermal ablation, wherein the capability of treating larger tumors in a shorter time needs proper monitoring. Current diagnostic imaging techniques do not provide effective solutions to this issue for a number of reasons, including economical sustainability and safety. Hence, the development of alternative modalities is of interest. Microwave tomography, which aims at imaging the electromagnetic properties of a target under test, has been recently proposed for this scope, given the significant temperature-dependent changes of the dielectric properties of human tissues induced by thermal ablation. In this paper, the outcomes of the first ex vivo experimental study, performed to assess the expected potentialities of microwave tomography, are presented. The paper describes the validation study dealing with the imaging of the changes occurring in thermal ablation treatments. The experimental test was carried out on two ex vivo bovine liver samples and the reported results show the capability of microwave tomography of imaging the transition between ablated and untreated tissue. Moreover, the discussion section provides some guidelines to follow in order to improve the achievable performances.

Multidimensional thermal mapping during radiofrequency ablation treatments with minimally invasive fiber optic sensors.

Temperature mapping is a key asset in supporting the clinician during thermal ablation (TA) treatment of tumors without adding additional risk to the TA procedure. Herein we report our experiments on multidimensional thermal mapping during radio frequency (RF) thermal ablation treatments of an ex-vivo animal organ. The temperature was monitored using several arrays of fiber Bragg gratings properly positioned around the RF applicator. The results show the effectiveness of our proposed method at assessing the TA probe depth and demonstrating how the insertion depth directly influences the maximum temperature and the treated area of the radio frequency ablation.

Thermal Ablation of Bone Metastases.

Image-guided, minimally invasive, percutaneous thermal ablation of bone metastases has unique advantages compared with surgery or radiation therapy. Thermal ablation of osseous metastases may result in significant pain palliation, prevention of skeletal-related events, and durable local tumor control. This article will describe current thermal ablation techniques utilized to treat bone metastases, summarize contemporary evidence supporting such thermal ablation treatments, and outline an approach to percutaneous ablative treatment.

Place of radiofrequency thermal ablation in treatment of patients with colorectal cancer metastasis after previous liver resection

Place of radiofrequency thermal ablation in treatment of patients with colorectal cancer metastasis after previous liver resection

Ex Vivo and In Vivo Monitoring and Characterization of Thermal Lesions by High-Intensity Focused Ultrasound and Microwave Ablation Using Ultrasonic Nakagami Imaging.

The feasibility of ultrasonic Nakagami imaging to evaluate thermal lesions by high-intensity focused ultrasound and microwave ablation was explored in ex vivo and in vivo liver models. Dynamic changes of the ultrasonic Nakagami parameter in thermal lesions were calculated, and ultrasonic B-mode and Nakagami images were reconstructed simultaneously. The contrast-to-noise ratio (CNR) between thermal lesions and normal tissue was used to estimate the contrast resolution of the monitoring images. After thermal ablation, a bright hyper-echoic region appeared in the ultrasonic B-mode and Nakagami images, identifying the thermal lesion. During thermal ablation, mean values of Nakagami parameter showed an increasing trend from 0.72 to 1.01 for the ex vivo model and 0.54 to 0.72 for the in vivo model. After thermal ablation, mean CNR values of the ultrasonic Nakagami images were 1.29 dB (ex vivo) and 0.80 dB (in vivo), significantly higher ( ) than those for B-mode images. Thermal lesion size, assessed using ultrasonic Nakagami images, shows a good correlation to those obtained from the gross-pathology images (for the ex vivo model: length, = 0.96; width, = 0.90; for the in vivo model: length, = 0.95; width, = 0.85). This preliminary study suggests that ultrasonic Nakagami parameter may have a potential use in evaluating the formation of thermal lesions with better image contrast. Moreover, ultrasonic Nakagami imaging combined with B-mode imaging may be utilized as an alternative modality in developing monitoring systems for image-guided thermal ablation treatments.