Physiological Motion Reduction Using Lagrangian Tracking for Electrode Displacement Elastography

Minimally invasive treatments such as microwave ablation (MWA) have been growing in popularity for extending liver cancer survival rates in patients, when surgery is not an option. As a non-ionizing, real-time alternative to contrast-enhanced computed tomography, electrode displacement elastography (EDE) has shown promise as an imaging modality for MWA. Despite imaging efficacy, motion artifacts caused by physiological motion result in unintended speckle pattern variance, thereby inhibiting consistent and accurate ablated region visualization. To combat these unavoidable motion artifacts, a Lagrangian deformation tracking (LDT) approach based on freehand EDE was developed to track tissue movement and better define tissue properties. For validating LDT efficacy, a spherical inclusion phantom as well as seven in vivo data sets were processed, and strain tensor images were compared with identical time sampled images estimated using a traditional Eulerian approach. In vivo results revealed greater consistency among visualized LDT strain tensor images, with segmented ablated regions exhibiting standard deviation reductions of up to 98% when compared with Eulerian strain tensor images. Additionally, Lagrangian strain tensor images provided Dice coefficient improvements up to 25%, and success rates improved from approximately 50% to nearly 100% for ablated region visualization.     

Delineation of Post-Procedure Ablation Regions with Electrode Displacement Elastography with a Comparison to Acoustic Radiation Force Impulse Imaging

We compared a quasi-static ultrasound elastography technique, referred to as electrode displacement elastography (EDE), with acoustic radiation force impulse imaging (ARFI) for monitoring microwave ablation (MWA) procedures on patients diagnosed with liver neoplasms. Forty-nine patients recruited to this study underwent EDE and ARFI with a Siemens Acuson S2000 system after an MWA procedure. On the basis of visualization results from two observers, the ablated region in ARFI images was recognizable on 20 patients on average in conjunction with B-mode imaging, whereas delineable ablation boundaries could be generated on 4 patients on average. With EDE, the ablated region was delineable on 40 patients on average, with less imaging depth dependence. Study of tissue-mimicking phantoms revealed that the ablation region dimensions measured on EDE and ARFI images were within 8%, whereas the image contrast and contrast-to-noise ratio with EDE was two to three times higher than that obtained with ARFI. This study indicated that EDE provided improved monitoring results for minimally invasive MWA in clinical procedures for liver cancer and metastases.     

Differential Imaging of Liver Tumors before and after Microwave Ablation with Electrode Displacement Elastography

Liver cancer is a leading cause of cancer-related deaths; however, primary treatment options such as surgical resection and liver transplant may not be viable for many patients. Minimally invasive image-guided microwave ablation (MWA) provides a locally effective treatment option for these patients with an impact comparable to that of surgery for both cancer-specific and overall survival. MWA efficacy is correlated with accurate image guidance; however, conventional modalities such as B-mode ultrasound and computed tomography have limitations. Alternatively, ultrasound elastography has been used to demarcate post-ablation zones, yet has limitations for pre-ablation visualization because of variability in strain contrast between cancer types. This study attempted to characterize both pre-ablation tumors and post-ablation zones using electrode displacement elastography (EDE) for 13 patients with hepatocellular carcinoma or liver metastasis. Typically, MWA ablation margins of 0.5–1.0 cm are desired, which are strongly correlated with treatment efficacy. Our results revealed an average estimated ablation margin inner quartile range of 0.54–1.21 cm with a median value of 0.84 cm. These treatment margins lie within or above the targeted ablative margin, indicating the potential to use EDE for differentiating index tumors and ablated zones during clinical ablations. We also obtained a high correlation between corresponding segmented cross-sectional areas from contrast-enhanced computed tomography, the current clinical gold standard, when compared with EDE strain images, with r² values of 0.97 and 0.98 for pre- and post-ablation regions.     

实时剪切波弹性成像评估乳腺良性结节微波消融效果的价值探讨

目的探讨实时剪切波弹性成像(SWE)技术在评估乳腺良性结节微波消融效果的应用价值。方法选取23例乳腺良性结节患者(共25个结节),分别于行微波消融治疗前后行常规超声、超声造影及SWE检查,比较超声造影与SWE显示的有效消融区横切面及纵切面最大径,以及消融前后消融区的杨氏模量值,包括最大弹性值(E_(max))、平均弹性值(E_(mean))、弹性标准差(E_(sd))及病灶与正常脂肪组织弹性比(E_(ratio))。结果微波消融术后,超声造影显示有效消融区无造影剂灌注;SWE显示消融区以红黄相间的不均匀彩色改变为主,与周围组织分界清晰,两种方法获得的消融区横切面及纵切面最大径比较差异均无统计学意义。消融区杨氏模量值(E_(max)、E_(mean)、E_(sd)及E_(ratio))均较术前显著增加,差异均有统计学意义(均P0.01)。结论 SWE可较准确地反映乳腺结节微波消融术后的消融范围,并能够定量分析消融区硬度变化,有望成为无创、有效评价消融效果的方法。     

微波消融人离体子宫肌瘤与猪离体肌组织的对比观察

目的 比较单导植入式微波消融人离体子宫肌瘤与猪离体肌组织的异同点,探讨微波消融离体猪肌组织的各项参数对临床微波消融子宫肌瘤的指导和参考价值.方法 采用单导2450 MHz微波,作用功率50 W,作用时间300 s,分别进行离体肌组织和离体子宫肌瘤消融,对比观察消融区形态、范围、消融时声像图表现、病理表现等参数.结果 同剂量微波消融离体子宫肌瘤的范围小于离体肌组织范围;二者消融时的声像图表现及消融形态类似.肌瘤被膜不连续处有热外泄.结论 微波消融离体猪肌组织的各项参数对临床微波消融子宫肌瘤有指导和参考价值.     

模拟甲状腺囊实性结节囊性成分射频和微波消融的离体实验研究

目的探讨甲状腺囊实性结节射频和微波消融的可行性及效能。 方法使用目前常用的热消融方式（射频和微波）对甲状腺囊实性结节囊性成分的模拟液体（蒸馏水、生理盐水、血液、肝囊肿穿刺液和甲状腺囊实性结节穿刺液）进行消融。作用功率为目前临床常用的热消融功率（35 W和50 W）,每30 s记录温度值,连续监测10 min,绘制时间温度曲线。观察消融针针尖情况,记录针尖液体固化大小、形态及内部结构特点,必要时送病理检查。比较相同功率消融达到目标温度（60 ℃）的时间,并使用方差分析比较相同功率的射频和微波消融的热效能差异。 结果蒸馏水仅能进行微波消融,而无法进行射频消融。35 W射频消融在生理盐水、肝囊肿穿刺液中比微波消融较早达到消融目标温度［（171.4±3.9）s vs（343.6±5.7）s、（170.2±4.8）s vs（444.5±7.2）s］,时间温度曲线上具有较好的热效能（F=228.311、193.632,P均＜0.001）;50 W射频消融在肝囊肿穿刺液中比微波消融较早达到消融目标温度［（127.3±3.1）s vs（165.7±3.4）s］,时间温度曲线上具有较好的热效能（F=47.429,P＜0.001）;但射频消融在血液和甲状腺囊实性结节穿刺液中无法达到消融目标温度。而50 W微波消融能在所有模拟液体中达到消融目标温度,且在血液和甲状腺囊实性结节穿刺液中的热效能明显优于射频消融（F=47.429、22.859,P均＜0.001）。 结论微波消融能对各甲状腺囊实性结节囊性成分的模拟液体进行消融,且性能相对稳定。射频消融热效能较高,但对蒸馏水无法消融,对血液和甲状腺囊实性结节穿刺液因针尖容易形成积碳而效果不佳。     

Estimation of the transverse strain tensor in the arterial wall using IVUS image registration

Intravascular ultrasound (IVUS) elastography is an imaging technique that obtains the local mechanical properties of the artery wall and atherosclerotic plaques through strain measurements using IVUS. Knowledge of these mechanical properties may provide crucial information that can help in estimating plaque composition and its vulnerability. Here, we present a new method to estimate the transverse strain tensor of the arterial wall based on nonrigid image registration using IVUS images. This method registers a pair of images acquired at a vessel site under different levels of luminal pressure. The 2-D displacement field in the vessel cross-section is estimated from image registration; then the displacement field is used to calculate the 2-D local strain tensor. From the strain tensor, the strain in any direction in the cross-section can be obtained; here, the radial and circumferential strain distributions are presented. This strain estimation method has been validated with synthetic motion IVUS images and evaluated using the IVUS images of a polyvinyl alcohol cryogel phantom. The accuracy of the estimated strain and the ability of the method to overcome IVUS system noise are demonstrated.     

Real-time calibration of temperature estimates during radiofrequency ablation

Radiofrequency ablation is an interstitial focal ablative therapy that can be used in a percutaneous fashion and permits in situ destruction of hepatic tumors. Recurrence rates after rf therapy are as high as 34-55%, due to difficulties in accurately identifying the zone of necrosis (thermal lesion) because of the low intrinsic acoustic contrast between normal and ablated liver tissue. Our goal is to provide real-time ultrasonic tracking of temperature changes over the large range of temperatures traditionally used (40-100 degrees C) in rfablation procedures using an external ultrasound transducer. Temperature estimates are obtained using a cross-correlation algorithm applied to rf ultrasound echo signal data acquired at discrete intervals during heating. Apparent tissue displacement estimates obtained at these discrete time-intervals are accumulated to obtain a cumulative displacement map, whose gradient provides after appropriate scaling provides a temperature map at the specified elapsed ablation duration. Temperature maps are used to display the initial temperature rise and to continuously update a thermal map of the treated region. In this paper, we develop calibration curves that relate the echo shift due to the change in the speed of sound and thermal expansion to the corresponding temperature increase on in-vitro tissue specimens. These calibration curves can then be utilized for the real time calibration and analysis of temperature estimates obtained from the rf echo signals during ablation. Temperature maps obtained using the calibration curve compare favorably to temperature estimates observed using the invasive thermosensor readings on the ablation electrode and previous results that utilized a linear calibration factor.     

Ultrasound elastography using multiple images

Displacement estimation is an essential step for ultrasound elastography and numerous techniques have been proposed to improve its quality using two frames of ultrasound RF data. This paper introduces a technique for calculating a displacement field from three (or multiple) frames of ultrasound RF data. To calculate a displacement field using three images, we first derive constraints on variations of the displacement field with time using mechanics of materials. These constraints are then used to generate a regularized cost function that incorporates amplitude similarity of three ultrasound images and displacement continuity. We optimize the cost function in an expectation maximization (EM) framework. Iteratively reweighted least squares (IRLS) is used to minimize the effect of outliers. An alternative approach for utilizing multiple images is to only consider two frames at any time and sequentially calculate the strains, which are then accumulated. We formally show that, compared to using two images or accumulating strains, the new algorithm reduces the noise and eliminates ambiguities in displacement estimation. The displacement field is used to generate strain images for quasi-static elastography. Simulation, phantom experiments and in vivo patient trials of imaging liver tumors and monitoring ablation therapy of liver cancer are presented for validation. We show that even with the challenging patient data, where it is likely to have one frame among the three that is not optimal for strain estimation, the introduction of physics-based prior as well as the simultaneous consideration of three images significantly improves the quality of strain images. Average values for strain images of two frames versus ElastMI are: 43 versus 73 for SNR (signal to noise ratio) in simulation data, 11 versus 15 for CNR (contrast to noise ratio) in phantom data, and 5.7 versus 7.3 for CNR in patient data. In addition, the improvement of ElastMI over both utilizing two images and accumulating strains is statistically significant in the patient data, with p-values of respectively 0.006 and 0.012.     

Characterization of enamel and dentin response to Nd:YAG picosecond laser ablation

OBJECTIVE: We investigated the main characteristics of human dental tissue under Nd:YAG picosecond laser ablation. SUMMARY BACKGROUND DATA: The use of ultrashort laser pulses for teeth ablation prevents overheating and is an alternative for mechanical material removal; it also minimizes the volume of damaged material. METHODS: Laser pulses of picosecond at 15 Hz repetition rates from a Q-switched and mode-locked Nd:YAG laser were focused on sound human molars for 30 seconds. Variation of light intensity in the pulse train allowed us to obtain drilled holes with different characteristics. Enamel and dentin surfaces were examined by optical and scanning electron microscope (SEM). The samples consisted of three sound human molars. The ablation rate was determined after taking an average of all samples. RESULTS: Images from the SEM showed an interesting contrast between the morphology of the ablated enamel and dentin regions. In enamel, the ablated region appears to be more superficial than in dentin. The dentin fragility normally causes cracks that originate in the ablated region. The ablation rates in both enamel and dentin demonstrate a saturation behavior as the laser intensity increases. Furthermore, the ablation rate in dentin is about eight times greater than in enamel for the same laser fluence. CONCLUSION: Our results show an important correlation between the surface morphology and the pulsed laser fluence, which is compatible to the ablation mechanisms presented when ultrashort laser pulses are used.     

Monitoring Microwave Ablation of Ex Vivo Bovine Liver Using Ultrasonic Attenuation Imaging

Thermal ablation of soft tissue changes the tissue microstructure and, consequently, induces changes in its acoustic properties. Although B-mode ultrasound provides high-resolution and high-frame-rate images of ablative therapeutic procedures, it is not particularly effective at delineating boundaries of ablated regions because of poor contrast in echogenicity between ablated and surrounding normal tissue. Quantitative ultrasound techniques can provide quantitative estimates of acoustic properties, such as backscatter and attenuation coefficients, and differentiate ablated and unablated regions more effectively, with the potential for monitoring minimally invasive thermal therapies. In this study, a previously introduced attenuation estimation method was used to create quantitative attenuation coefficient maps for 11 microwave ablation procedures performed on refrigerated ex vivo bovine liver. The attenuation images correlate well with the pathologic images of the ablated region. The mean attenuation coefficient for regions of interest drawn inside and outside the ablated zones were 0.9 (±0.2) and 0.45 (±0.15) dB/cm/MHz, respectively. These estimates agree with reported values in the literature and establish the usefulness of non-invasive attenuation imaging for monitoring therapeutic procedures in the liver.     

Analysis of 2-D Ultrasound Cardiac Strain Imaging Using Joint Probability Density Functions

Ultrasound frame rates play a key role for accurate cardiac deformation tracking. Insufficient frame rates lead to an increase in signal de-correlation artifacts resulting in erroneous displacement and strain estimation. Joint probability density distributions generated from estimated axial strain and its associated signal-to-noise ratio provide a useful approach to assess the minimum frame rate requirements. Previous reports have demonstrated that bi-modal distributions in the joint probability density indicate inaccurate strain estimation over a cardiac cycle. In this study, we utilize similar analysis to evaluate a 2-D multi-level displacement tracking and strain estimation algorithm for cardiac strain imaging. The effect of different frame rates, final kernel dimensions and a comparison of radio frequency and envelope based processing are evaluated using echo signals derived from a 3-D finite element cardiac model and five healthy volunteers. Cardiac simulation model analysis demonstrates that the minimum frame rates required to obtain accurate joint probability distributions for the signal-to-noise ratio and strain, for a final kernel dimension of 1 λ by 3 A-lines, was around 42 Hz for radio frequency signals. On the other hand, even a frame rate of 250 Hz with envelope signals did not replicate the ideal joint probability distribution. For the volunteer study, clinical data was acquired only at a 34 Hz frame rate, which appears to be sufficient for radio frequency analysis. We also show that an increase in the final kernel dimensions significantly affect the strain probability distribution and joint probability density function generated, with a smaller effect on the variation in the accumulated mean strain estimated over a cardiac cycle. Our results demonstrate that radio frequency frame rates currently achievable on clinical cardiac ultrasound systems are sufficient for accurate analysis of the strain probability distribution, when a multi-level 2-D algorithm and kernel dimensions on the order of 1 λ by 3 A-lines or smaller are utilized.     

超声引导下经皮注射无水乙醇联合微波消融治疗甲状腺良性囊实性肿物

目的 观察超声引导下经皮注射无水乙醇（PEI）联合微波消融（MWA）治疗甲状腺良性囊实性肿物的价值。方法 前瞻性纳入100例拟接受超声引导下消融治疗的甲状腺单发良性囊实性肿物患者,随机将其均分为PEI组（行PEI联合MWA序贯消融治疗）和对照组（行单纯MWA治疗）,观察治疗前、后组内一般资料差异及组间疗效差异,评估序贯消融价值。结果 对100个甲状腺肿物均顺利完成超声引导下消融。随访期间PEI组5例、对照组3例失访。PEI组MWA用时、MWA总能量及治疗中患者疼痛程度均低于对照组（P均<0.05）。治疗后1、3、6及12个月,PEI组肿物体积缩小率（VRR）均高于对照组（P均<0.05）。治疗后3、6及12个月,2组肿物体积与治疗前差异均有统计学意义（P均<0.05）。治疗后12个月,PEI组与对照组治疗成功率分别为95.56%（43/45）和89.36%（42/47）,组间差异无统计学意义（P=0.451）。治疗后3、6及12个月,2组颈部美观评分及症状评分与治疗前差异均有统计学意义（P均<0.05）。PEI组并发症率为6.67%（3/45）,对照组为14.89%（7/47）,前者低于后者（P<0.05）。结论 超声引导下PEI联合MWA序贯消融治疗甲状腺良性囊实性肿物效果优于单纯MWA。     

A Fast Peak‐Searching Algorithm for Ultrasonic Elastography

Tissue axial strain estimation with ultrasound elastography has become a hot field in recent years. However, for keypoints tracking–based elastography algorithms, locating extrema in multimodal ultrasonic radiofrequency signals is still a challenging problem. In this paper, a new method is proposed to locate the local maxima and minima of the RF signals directly without derivation operation. This algorithm can accurately locate extrema even if disturbed peaks resulting from different noise exist. Furthermore, the new algorithm can speed up approximately 79% of the implementation process as compared with the standard cross‐correlation method on the same computing platform. In addition, the elastographic signal‐to‐noise ratio and the contrast‐to‐noise ratio are also significantly improved with this new method.     

Why Is Catheter Ablation Less Successful than Surgery for Treating Ventricular Tachycardia that Results from Coronary Artery Disease?

Nearly 80% of patients with coronary artery disease who have map-directed surgery for control of ventricular tachycardias require no drug therapy to prevent recurrences, while fewer than 50% of patients undergoing catheter ablation have similar outcomes. Catheter ablation will fail if arrbythmogenic sites are incompletely ablated by lesions that are too small or too far away from the reentrant pathway or if all arrbythmogenic sites are not identified. The underlying assumptions used to guide site selection are that: (a) ventricular tachycardias arise from reentrant mechanisms; (b) monomorphic ventricular tachycardias with similar QRS morphologies arise from the same pathway; (c) the ventricular tachycardia initiated during the procedure represents the patient's spontaneous arrhythmia; (d) the endocardial site that should be ablated can be identified from cardiac activation maps produced during induced ventricular tachycardia or from ancillary techniques; and (e) the patient has only one or two reentrant pathways. Relying on incorrect assumptions may account for the difference in success rates. Patients may have similar appearing ventricular tachycardias that arise from different pathways, and the entire thin layer of viable tissue between the infarct and the endocardium may contain many reentrant pathways. Some ventricular tachycardias may arise from the myocardium away from the endocardium, while others may arise from the epicardium. Small lesions may not be large enough to eliminate all possible reentrant pathways. Catheter ablation may be less successful because the lesions are inadequate, the assumptions guiding the selection of arrhythmogenic tissue are incorrect, or all arrhythmogenic sites are not identified. The primary reason catheter ablation is less successful than surgery in the treatment of ventricular tachycardias is that catheter ablation does not ablate as much tissue as is removed by surgery. The success rate of catheter ablation probably can be improved if the amount of tissue ablated is increased.     

High success rate with cryomapping and cryoablation of atrioventricular nodal reentrytachycardia

INTRODUCTION: Cryoablation is a new alternative to radiofrequency (RF) ablation for treatment of atrioventricular nodal reentry tachycardias (AVNRT). Mapping with reversible effect on the arrhythmia substrate or the AV node can be done before irreversible ablation is performed. This study evaluates an approach with systematic cryomapping, ablating only in areas with prompt effect on the arrhythmia substrate and evaluates whether the success rates and procedure times are similar to RF ablation. METHODS AND RESULTS: Seventy-five consecutive patients with typical slow-fast AVNRT were studied. Cryomapping at -30 degrees C was performed before ablation with a goal temperature of -70 degrees C for 240 seconds. The ablation procedure was successful in 74 of the 75 patients, giving an acute success rate of 99%. During a mean follow-up of 338 days, 70 of the 74 primarily successfully ablated patients were free from the treated arrhythmia, giving a recurrence rate of 5% and a total success rate of 93%. Total procedure time including a 30-minute test after successful ablation was 126+/-55 minutes. Fluoroscopy time was 18.5+/-14.9 minutes. CONCLUSION: Cryoablation of AVNRT appears to be as effective as RF ablation both acute and in long term with minimal risks for unwanted injuries on the conduction system. The procedure can be done with reasonable procedure and fluoroscopy times.     

超声引导经皮微波消融甲状腺良性结节的应用研究

目的探讨超声引导下经皮穿刺微波消融治疗甲状腺良性结节的临床疗效及并发症等情况.方法选取本院诊治的甲状腺良性结节患者86例（156个结节）,术前细胞学检查确定为良性结节,行超声引导下经皮穿刺结节微波消融术后即刻超声造影,对不全消融结节行二次消融.在术后随访观察消融术后结节大小变化及并发症情况.同时与此期间在我院行甲状腺次全切除术的65例甲状腺良性结节患者作为对照组,分析两组患者的术后并发症出现人数及甲状腺功能恢复等.结果仅4/156枚需二次消融,一次消融率达97.4%.消融后第1、3、6及12个月体积缩小率分别为20.98%,45.37%,75.12%和86.83%;23/156（14.7%）枚结节在随访6-12个月内消失.观察组患者甲状腺功能恢复人数多于对照组,其术后并发症出现人数少于对照组（均P〈0.05）.结论微波消融治疗甲状腺良性结节疗效显著,并发症少,是传统手术治疗的一个有效补充.     

MRI、超声显像在乳腺良性结节微波消融治疗中的应用

目的探讨磁共振成像(magnetic resonance imaging,MRI)和超声(ultrasound,US)显像评价乳腺良性结节微波消融治疗的价值。材料与方法选择超声引导下穿刺活检经病理证实的乳腺良性结节患者20例共41个结节,微波消融治疗前分别行US和MRI检查,观察结节的位置、大小、边界、内部回声、血流分布及造影增强等情况,超声引导定位,精确地将微波电极穿入结节内行微波消融,治疗后利用MRI和US显像判断消融治疗的效果。结果消融治疗前后结节平均大小分别为(17.5±5.6) mm和(15.9±6.9) mm,差异有统计学意义(t=2.752,P=0.012)。消融治疗前,灰阶超声结节表现为低回声,边界多清楚(83%);超声造影(contrast-enhanced ultrasound,CEUS)和MRI增强扫描显示结节内均有不同程度增强。消融治疗后,灰阶超声显示原结节区域呈不均匀高回声,边界不清;CEUS检查结节呈无增强35个(85%),结节边缘少量星点状增强6个,经再次消融治疗后结节内无增强;MRI显示结节内均呈无增强,消融区域周边见水肿带。超声引导下穿刺活检,消融区呈凝固样坏死。结论 MRI有助于全面了解结节的大小、空间结构及血流分布;US显像术前了解结节情况,实时引导和监测消融过程,两者联合应用对制定正确的消融策略和远期疗效的评价有重要作用。     

Feasibility of Using Ultrasonic Nakagami Imaging for Monitoring Microwave-Induced Thermal Lesion in Ex Vivo Porcine Liver

The feasibility of using ultrasonic Nakagami imaging to evaluate thermal lesions induced by microwave ablation (MWA) in ex vivo porcine liver was explored. Dynamic changes in echo amplitudes and Nakagami parameters in the region of the MWA-induced thermal lesion, as well as the contrast-to-noise ratio (CNR) between the MWA-induced thermal lesion and the surrounding normal tissue, were calculated simultaneously during the MWA procedure. After MWA exposure, a bright hyper-echoic region appeared in ultrasonic B-mode and Nakagami parameter images as an indicator of the thermal lesion. Mean values of the Nakagami parameter in the thermal lesion region increased to 0.58, 0.71 and 0.91 after 1, 3 and 5 min of MVA. There were no significant differences in envelope amplitudes in the thermal lesion region among ultrasonic B-mode images obtained after different durations of MWA. Unlike ultrasonic B-mode images, Nakagami images were less affected by the shadow effect in monitoring of MWA exposure, and a fairly complete hyper-echoic region was observed in the Nakagami image. The mean value of the Nakagami parameter increased from approximately 0.47 to 0.82 during MWA exposure. At the end of the postablation stage, the mean value of the Nakagami parameter decreased to 0.55 and was higher than that before MWA exposure. CNR values calculated for Nakagami parameter images increased from 0.13 to approximately 0.61 during MWA and then decreased to 0.26 at the end of the post-ablation stage. The corresponding CNR values calculated for ultrasonic B-mode images were 0.24, 0.42 and 0.17. This preliminary study on ex vivo porcine liver suggested that Nakagami imaging have potential use in evaluating the formation of MWA-induced thermal lesions. Further in vivo studies are needed to evaluate the potential application.     

超声引导下经皮微波消融治疗肝细胞性肝癌术后复发灶远期疗效评估

目的评价肝细胞性肝癌(hepatic cellular carcinoma,HCC)手术后复发灶(直径≤5 cm)超声引导下经皮微波消融(microwave ablation,MWA)治疗的远期疗效及其影响因素。方法 2005年5月~2011年12月,89例HCC复发患者行经皮微波消融治疗。所有HCC复发患者在MWA治疗后1个月均行超声造影、增强CT或者增强磁共振检查;以及血生化检查,包括血清甲胎蛋白(AFP)、肝功能等。结果消融治疗1个月后,病灶完全消融率91%(81/89)。HCC经皮MWA治疗后,1、3、5、7年生存率分别为73.3%、53.7%、39.6%、17.3%。肿瘤大小(P=0.046)、肿瘤数目(P=0.001)、Child-Pugh分级(P=O.023)、AFP水平(P=0.003)以及HCC早期复发(≤1年)(P=0.013)为总体生存率的单因素回归分析的危险预后因素。肿瘤数目(P=0.000)、Child-Pugh分级(P=0.000)和AFP水平(P=0.001)是HCC经皮MWA治疗后总体生存率重要的独立危险因素。结论经皮MWA对于肝细胞性肝癌切除术后复发灶是有效、安全的治疗方法 。