Combined utility of one lung ventilation and artificial pneumothorax in thermal ablation of hepatic dome tumor: a technical note

Radiofrequency ablation and microwave ablation are established treatment modalities for smaller (<3 cm) or isolated hepatic tumors. Transthoracic ablation of hepatic dome lesions is a well described technique. We report the use of one lung ventilation to facilitate the successful percutaneous transthoracic microwave ablation of a segment 8 hepatic dome lesion after induction of artificial pneumothorax. This involved the use of general anesthesia and insertion of a double lumen endotracheal tube to allow isolated ventilation of one lung, followed by creation of an artificial pneumothorax under computed tomography (CT) guidance. Complete ablation of the lesion was confirmed on CT liver at 1 and 7 months with no local recurrence. The combined techniques of one lung ventilation and artificial pneumothorax enabled a safe and accurate transthoracic targeting of the hepatic dome lesion.

Thermal ablation techniques such as radiofrequency ablation (RFA) and microwave ablation (MWA) are alternative treatment options for patients with small (<3 cm) or isolated lesions. Transthoracic ablation of lesions is safe and effective for treatment of hepatic dome lesions.Current standard of practice in most centers is the administration of local anesthesia with moderate conscious sedation for percutaneous RFA or MWA. Thermal ablation under sedation is poorly tolerated in patients whose lesions are more than 3 cm in size or in the sub-diaphragmatic location, commonly requiring conversion to general anesthesia due to pain on ablation and/or need for controlled apnea to allow for accurate targeting of the lesion (1). Additionally, incomplete ablation of tumors is more common in procedures with sedation compared to general anesthesia (1).Even under general anesthesia, hepatic dome lesion targeting is affected by the constant respiratory movements of the liver and diaphragm. We report the use of one-lung ventilation (OLV) to facilitate safe and successful transthoracic percutaneous computed tomography (CT)-guided MWA of a hepatic dome hepatocellular carcinoma (HCC) lesion after induction of artificial pneumothorax to avoid injury to the lung and visceral pleura.     

MR-guided microwave thermocoagulation therapy of liver tumors: initial clinical experiences using a 0.5 T open MR system

PURPOSE: To utilize a microwave coagulator for MR-guided interstitial thermal therapy of liver tumors as a clinically feasible heating device. MATERIALS AND METHODS: MR-guided microwave thermocoagulation therapy was carried out 34 times in 30 patients with liver tumors (eight hepatocellular carcinoma, 22 metastatic tumors) using a 0.5 T open configuration MR system. RESULTS: Percutaneous puncture could be accomplished both accurately and safely while monitoring real-time magnetic resonance imaging (MRI). Using a notch filter, MR images could be observed without electromagnetic interference even during microwave ablation. Temperature monitoring during ablation was possible using the proton resonance frequency method. All procedures could be successfully carried out without any complications, and the therapeutic effects were deemed satisfactory. CONCLUSION: MR-guided microwave thermocoagulation therapy could be one promising procedure of minimally invasive treatment for liver tumors.     

Advanced computer assistance for magnetic resonance-guided microwave thermocoagulation of liver tumors

Rationale and Objectives. The purpose of this study was to utilize computer assistance effectively for both easy and accurate magnetic resonance (MR) image-guided microwave thermocoagulation therapy of liver tumors.

Materials and Methods. An open configuration MR scanner and a microwave coagulator at 2.45 GHz were used. Navigation software, a 3D Slicer, was customized to combine fluoroscopic MR images and preoperative MR images for the navigation. New functions to display MR temperature maps with simple parameter setting, and to record and display the coagulated areas by multiple microwave ablations in the 3-dimensional space (footprinting), were also introduced into the software. The VGA signal of the computer display was directly transferred to the surgeon’s monitor.

Results. The customized software could be used for both accurate image navigation and convenient and easy temperature monitoring. Because repeated punctures and ablations are usually required in this procedure, the footprinting function made targeting of the tumors both easy and accurate and was quite effective in achieving the necessary and sufficient treatment. Furthermore, clear display on the surgeon’s monitor, which was obtained by direct transfer of the VGA signal, enabled precise image navigation.

Conclusion. The newly developed computer assistance was quite useful and helpful for this MR-guided procedure.     

Invited. Interactive MRI-guided radiofrequency interstitial thermal ablation of abdominal tumors: Clinical trial for evaluation of safety and feasibility

This clinical trial was performed to evaluate the safety and feasibility of interactive MR-guided radiofrequency (RF) interstitial thermal ablation (ITA) performed entirely within the MR imager. RF-ITA was performed on 11 intra-abdominal metastatic tumors during 13 sessions. The RF electrode was placed under MR guidance on a .2-T system using rapid fast imaging with steady state precession (FISP) and true FISP images. A custom 17-gauge electrode was used and was modified in four sessions to allow circulation of iced saline for cooling during ablation. Tissue necrosis monitoring and electrode repositioning were based on rapid T2-weighted and short-inversion-time inversion recovery (STIR) sequences. Morbidity and toxicity were assessed by clinical and imaging criteria. The region of tissue destruction was visible in all 11 tumors treated, as confirmed on subsequent contrast-enhanced images. No significant morbidity was noted, and patient discomfort was minimal. In conclusion, interactive MR-guided RF-ITA is feasible on a clinical .2-T C-arm system with supplemental interventional accessories with only minor patient morbidity. The ability to completely ablate tumors with RF-ITA depends on tumor size and vascularity.     

Magnetic resonance-guided focused ultrasound surgery (MRgFUS): ablation of liver tissue in a porcine model

BACKGROUND: Liver surgery is technically demanding and is considered a major procedure with relatively high morbidity rates. Magnetic resonance-guided focused ultrasound surgery (MRgFUS) uses focused ultrasonic energy to create a heat coagulation lesion, which can be achieved in a totally controlled, very accurate manner (<1 mm). The aim of this study was to evaluate the safety and accuracy of non-invasive focal ablation of liver tissue achieved by consecutive MRgFUS sonications. MATERIALS AND METHODS: Six MRgFUS procedures were performed in five pigs under general anesthesia, with the ExAblate 2000 system (InSightec, Israel). Real-time imaging and temperature mapping (Signa Twinspeed 1.5T, GEHC, USA) enabled the immediate evaluation of the results of each sonication. Different foci were chosen within the liver. These mock lesions were ablated by several sonications, each of them performed during 20-30 s of apnea. Between sonications, the pigs were normally ventilated. The pigs were sacrificed 3-21 days after the procedure and their livers were examined. RESULTS: The MRgFUS created complete tissue destruction of mock lesions in different areas of the pig's liver. The lesion sizes in each animal varied according to the number of sonications used and the extent of overlap between adjacent sonications. The lesion ranged in size from 1.5 cm x 1.5 cm x 2.0 cm to 5.5 cm x 4.5 cm x 2.0 cm. There was no morbidity. CONCLUSIONS: MRgFUS under general anesthesia is a safe, completely non-invasive technology for the ablation of liver tissue. Liver tissue can be ablated in a very accurate manner, based on the pre-treatment planning on the MR images. The MR imaging characteristics, including real-time temperature mapping, enable real-time control of every step of the ablation process. Mechanical ventilation with intermittent periods of apnea is a technique that overcomes the problem of the respiratory movements of the liver.     

人工液胸辅助超声引导微波消融治疗肝癌的临床应用价值

 目的 探讨人工液胸在辅助超声引导经皮微波消融治疗近膈顶肝癌的临床应用价值。方法 回顾性研究2011-01至2013-12行人工液胸操作辅助超声引导微波消融治疗肝癌的患者115例临床资料,年龄35～82岁,对人工液胸操作的可行性、有效性和安全性指标进行评估。结果 人工液胸操作成功率97.4%(112/115),滴注的生理盐水量为500～1500 ml,平均(962.9±219.4)ml。操作成功的112例患者中110例完成了肝癌的超声引导微波消融治疗,操作有效率98.2%。本组病例术中和术后未出现与人工液胸操作有关的严重并发症,轻微并发症包括疼痛、咳嗽等。结论 人工液胸技术具有良好的可行性,可以安全有效地用于辅助超声引导经皮微波消融治疗近膈顶肝癌,扩大了适应证范围。     

局限性人工腹水在临近胃肠管肝肿瘤消融中的应用

目的探讨CT引导下局限性人工腹水辅助在经皮微波消融治疗临近肠管肝肿瘤的有效性和安全性。 方法我院2015年至2019年中对48例临近肠管肝肿瘤病灶行CT引导下人工腹水辅助下微波消融术。对局限性人工腹水技术成功率、微波消融局部复发率、手术并发症等进行评估。 结果48例患者中47例成功行局限性人工腹水,28例患者之前有外科手术史,1例因局部粘连未能成功行局限人工腹水。47例患者均成功行微波消融术,1例术后腹腔少量出血,术后1月复查均完全消融。 结论局限性人工腹水辅助微波消融治疗临近胃肠道肝肿瘤病灶是一种安全、有效的治疗方法。     

Intraluminal high intensity ultrasound treatment in the esophagus under fast MR temperature mapping: in vivo studies.

New curative and palliative treatments are needed to respond to the poor prognosis of esophageal cancer. The purpose of this study was to determine whether magnetic resonance imaging (MRI) and MR thermometry can be used to monitor the thermal ablation induced by an intraluminal high-intensity ultrasound applicator positioned in the esophagus. Experiments were performed in vivo in 2 pig esophagi (25 thermal lesions per pig). Respiratory gated or cardiac gated MR thermometry was performed with segmented echo-planar imaging gradient echo sequences. All MR acquisitions were performed without susceptibility artifacts or radiofrequency interference with the ultrasound device. The experimental procedure proposed for accurate measurement of temperature in the esophagus was found to achieve an SD of +/- 1.5 degrees C for respiratory gating and +/- 3.1 degrees C for cardiac gating. Gd-enhanced T(1)-weighted images were used to depict coagulation necrosis. Autopsy was performed immediately after the treatment. Ultrasound effects were inspected visually, and the dimensions of the lesions in the liver neighboring the esophagus were compared with those determined on the MRI images. The visually assessed thermal lesions showed good correlation with the MRI data (10% mean volume difference). The feasibility of esophageal thermal ablation using intraluminal high-intensity ultrasound and of on-line MR temperature monitoring was demonstrated.     

Real-time MR temperature mapping of rabbit liver in vivo during thermal ablation.

It has been shown that quantitative MRI thermometry using the proton resonance frequency (PRF) method can be used to noninvasively monitor the evolution of tissue temperature, and to guide minimally-invasive tumor ablation based on local hyperthermia. Although hepatic tumors are among the main targets for thermal ablation, PRF-based temperature MRI of the liver is difficult to perform because of motion artifacts, fat content, and low T(*) (2). In this study the stability of real-time thermometry was tested on a clinical 1.5 T scanner for rabbit liver in vivo. The fast segmented EPI principle was used together with respiratory gating to limit respiratory motion artifacts. Lipid signal suppression was achieved with a binomial excitation pulse. Saturation slabs were applied to suppress artifacts due to flowing blood. The respiratory-gated MR thermometry in the rabbit liver in vivo showed a standard deviation (SD) of 1-3 degrees C with a temporal resolution of 3 s per slice and 1.4 mm x 1.9 mm spatial resolution in plane (slice thickness = 5 mm). The method was used to guide thermal ablation experiments with a clinical infrared laser. The estimated size of the necrotic area, based on the thermal dose calculated from MR temperature maps, corresponded well with the actual lesion size determined by histology and conventional MR images obtained 5 days posttreatment. These results show that quantitative MR temperature mapping can be obtained in the liver in vivo, and can be used for real-time control of thermal ablation and for lesion size prediction.     

Real time monitoring of radiofrequency ablation based on MR thermometry and thermal dose in the pig liver in vivo

To evaluate the feasibility and accuracy of MR thermometry based on the thermal dose (TD) concept for monitoring radiofrequency (RF) ablations, 13 RF ablations in pig livers were performed under continuous MR thermometry at 1.5 T with a filtered clinical RF device. Respiratory gated fast gradient echo images were acquired simultaneously to RF deposition for providing MR temperature maps with the proton resonant frequency technique. Residual motion, signal to noise ratio (SNR) and standard deviation (SD) of MR temperature images were quantitatively analyzed to detect and reject artifacted images in the time series. SD of temperature measurement remained under 2°C. Macroscopic analysis of liver ablations showed a white zone (Wz) surrounded by a red zone (Rz). A detailed histological analysis confirmed the ongoing nature of the coagulation necrosis in both Wz and Rz. Average differences (±SD) between macroscopic size measurements of Wz and Rz and TD predictions of ablation zones were 4.1 (±1.93) mm and −0.71 (±2.47) mm, respectively. Correlation values between TD and Wz and TD and Rz were 0.97 and 0.99, respectively. MR thermometry monitoring based on TD is an accurate method to delineate the size of the ablation zone during the RF procedure and provides a clinical endpoint.     

New assistive devices for MR-guided microwave thermocoagulation of liver tumors

RATIONALE AND OBJECTIVES: The purpose of this study was to develop and test new assistive devices to aid in the performance of safe, easy, and accurate microwave thermocoagulation therapy guided by magnetic resonance (MR) imaging. MATERIALS AND METHODS: An open-configuration MR imager with an optical tracking system for image plane control and a microwave coagulator operating at 2.45 GHz were used. Liver tumors were percutaneously punctured under the guidance of MR images and ablated. Handpiece adapters were then prepared for the optical tracking system. An MR-compatible endoscopic system also was used. Navigation software was installed and customized. These devices were combined to provide near-real-time MR image-guided navigation during thermocoagulation therapy for liver tumors. RESULTS: The handpiece adapters improved the flexibility of approaches for percutaneous puncture of tumors. The MR-compatible endoscope was used as a thoracoscope, and tumors just below the diaphragm were safely and easily punctured through the diaphragm. The customized navigation software displayed near-real-time MR images together with two reformatted images (on the same plane and on a perpendicular plane) from the registered high-resolution three-dimensional data, enabling accurate MR imaging navigation. CONCLUSION: These new assistive devices made it easier to perform safe, easy, and accurate MR-guided thermocoagulation therapy of liver tumors.     

Real-time monitoring of radiofrequency ablation of rabbit liver by respiratory-gated quantitative temperature MRI

PURPOSE: To evaluate the feasibility and precision of magnetic resonance imaging (MRI) thermometry for monitoring radiofrequency (RF) liver ablation in vivo and predicting the size of the ablation zone. MATERIALS AND METHODS: At 1.5T, respiratory-triggered real-time MR temperature mapping (the proton resonance frequency (PRF) method) was used to monitor RF ablation in rabbit liver (N = 6) under free breathing. The size of the ablation zones, as assessed by histological analyses, was compared with that predicted from MR thermal dose (TD) maps or derived from conventional T1-weighted (T1w), T2-weighted (T2w), and T1w gadolinium (Gd)-enhanced (T1w-Gd) images acquired immediately after the ablation, and on days 4 and 8 postprocedure. RESULTS: MR temperature uncertainty remained under 1-2 degrees C even during RF deposition. The TD maps were shown to be more predictive and precise than the other MR images, with an average predictive precision for the final ablation zone size of about 1 mm as compared to the histologically proven lesion on day 8. CONCLUSION: Quantitative temperature MRI during RF ablation is feasible and offered a precise indication of the ablation zone size in this preclinical study based on the lethal dose threshold.     

Phase II clinical trial of interactive MR imaging-guided interstitial radiofrequency thermal ablation of primary kidney tumors: initial experience

PURPOSE: To perform a phase II clinical trial to evaluate efficacy and safety of interactive magnetic resonance (MR) imaging-guided radiofrequency (RF) interstitial thermal ablation (ITA) of primary renal tumors. MATERIALS AND METHODS: Ten male patients (age range, 25-83 years) with peripheral renal cell carcinoma and contraindications to surgery were treated with percutaneous RF ITA entirely guided and monitored with a 0.2-T MR imaging unit. By using a 200-W RF ablation system and custom-fabricated MR imaging-compatible cool-tip electrodes, pulsed RF current was applied for single or multiple ablation cycle(s) of 12-15 minutes until the entire tumor was replaced by an enlarging zone of low signal intensity on T2-weighted and/or short inversion time inversion-recovery images acquired intermittently during the procedure. Kidney MR images were acquired before, immediately after, and 2 weeks after ablation and then every 3 months for 1 year and every 6 months thereafter. Intra- and postprocedural complications were assessed with clinical evaluation of patients for pain and hemodynamic instability and evaluation of MR images for evidence of hemorrhage or other unexpected findings. Follow-up images were assessed for delayed complications such as renal ischemia, infarct, urinoma, or tumor recurrence. RESULTS: Treated tumors ranged between 0.63 and 16.90 mL in volume and 1.0 and 3.6 cm in maximum diameter. Successful RF electrode insertion and/or repositioning into the renal mass was achieved in all cases with direct MR "fluoroscopic" guidance. Thirty ablation cycles were conducted at 21 electrode positions in the 10 procedures, and complete ablation, as defined with MR imaging, was achieved in all cases by the end of the procedure. Apart from two small self-limited perirenal hematomas, no intra- or postprocedural complications were observed. No delayed complications or tumor recurrence occurred during a mean follow-up period of 25 months +/- 9.4 (standard deviation). CONCLUSION: Although these results are preliminary, interactive MR imaging-guided RF ITA for treatment of primary renal tumors has a high success rate.     

Interventional MR-guided excisional biopsy of breast lesions

Interventional MR (IMR) machines have produced unique opportunities for image-guided surgery. The open configuration design and fast pulse sequences allow intraoperative scanning to monitor procedures. This study was undertaken to assess the potential use of IMR for image-guided surgery. Benign breast lesion excision was chosen as an uncomplicated surgical model. Ten female patients with known benign tumors underwent excision biopsy under general anesthesia in a Signa SP10 .5-T IMR machine (General Electric Medical Systems, Milwaukee, WI). Lesions were localized with precontrast and postcontrast (intravenous gadolinium-diethylenetriamine pentaacetic acid, .2 mmol/kg) fast multiplanar spoiled gradient-recalled acquisition in the steady state (GRASS) sequences. Preoperative “real-time” fast gradient-recalled sequences were also obtained using the Flashpoint (General Electric Medical Systems, Milwaukee, WI) tracker device. The maximum dimensions of each lesion were measured from the resulting images. Excision was performed using titanium instruments and an ultrasonically activated scalpel. Intraoperative real-time scanning demonstrated the resection margin and confirmed complete excision. The maximum dimensions of the macroscopic specimens were compared with those from the MR images. All tumors were visualized with the Signa scanner and real-time imaging and the images were enhanced after intravenous contrast. Maximum dimensions on histologic examination were not significantly different from those measured from Signa (P > .17) or real-time images (P > .4). There was no significant difference between lesion size from Signa and real-time images (P > .25). All postprocedure scans demonstrated complete excision. There were six fibroadenomas, two foci of sclerosing adenosis, one area of fibrocystic disease, and one schwannoma. Intraoperative MR scanning reliably identifies palpable breast tumors and can accurately guide surgical excision. Further work using MR guidance can now be performed in other general surgical areas.     

Magnetic resonance guidance for radiofrequency ablation of liver tumors

Image-guided thermal ablation of liver tumors is a minimally invasive treatment option. Techniques used for thermal ablation are radiofrequency (RF) ablation, laser interstitial thermotherapy (LITT), microwave (MW) ablation, high-intensity focused ultrasound (HIFU), and cryoablation. Among these techniques RF ablation attained widespread consideration. Image guidance should ensure a precise ablation therapy leading to a complete coagulation of tumor tissue without injury to critical structures. Therefore, the modality of image guidance has an important impact on the safety and efficacy of percutaneous RF ablation. The current literature regarding percutaneous RF ablation mainly describes the use of computed tomography (CT) and ultrasonography (US) guidance. In addition, interventional MR systems offer the possibility to utilize the advantages of MR imaging such as excellent soft-tissue contrast, multiplanar and interactive capabilities, and sensitivity to thermal effects during the entire RF ablation procedure. Monitoring of thermally induced coagulation by MR imaging is supportive to control the ablation procedure. MR imaging can be advantageously used to guide overlapping ablation if necessary as well as to define the endpoint of RF ablation after complete coverage of the target tissue is verified. Furthermore, monitoring of thermal effects is essential in order to prevent unintended thermal damage from critical structures surrounding the target region. Therefore, MR-guided RF ablation offers the possibility for a safe and effective therapy option in the treatment of primary and secondary hepatic malignancies. The article summarizes the role of MR guidance for RF ablation of liver tumors.     

Microwave coagulation therapy: ex vivo comparison of MR imaging and histopathology

We compared the findings of magnetic resonance (MR) images and pathological examination to determine whether or not MR images reflect pathological changes following microwave coagulation therapy (MCT) on liver tissue. We used microwave (generating frequency 2450 Mhz, wave length 12 cm, output 50 W, 60 second duration) to irradiate six canine livers under general anesthesia. After the animals were sacrificed, the livers were resected. The irradiated regions were cut with margins and divided into two pieces, one for MR study, and the other for pathological examination. The findings were compared. From the center to the marginal layer, the irradiated region presented 4/3 laminal patterns on T1/T2-weighted images: low/high, high/low, very high/high, and iso-low/high intensity. On gradient-echo imaging, the irradiated regions presented no decreasing signals using several echo time lengths. With hematoxylin and eosin stain, MR laminar patterns reflected the histopathological changes, as follows: a tissue loss area surrounding the inserted needle, low/high; decreased sinusoidal width with/without necrotic tissue, high/low; sinusoidal width dilation at the periphery, very high/high; and fatty degenerated tissue surrounding the irradiated area at the boundary of the normal hepatocytes, iso-low/high. The MR signal intensity, which reflected the histopathological changes, presented tissue characterization after MCT, and the macromolecular hydration effect influenced the high intensity on T1-weighted images.     

MRI assessment of percutaneous ablation of liver tumors: Value of subtraction images

Purpose:

To evaluate the value of subtraction images when using MRI to assess liver tumors treated with percutaneous ablation.

Materials and Methods:

Following percutaneous ablation of 35 liver tumors, two abdominal radiologists, blinded to outcomes, independently reviewed follow‐up MRI examinations for tumoral enhancement suggestive of residual/recurrent tumor and rated their confidence level. After one year, the readers reviewed the same examinations with added subtraction images. Accuracy of the detection of residual/recurrent tumor and contrast‐to‐noise ratios (CNR; for tumoral enhancement‐to‐liver, tumoral enhancement‐to‐ablation zone, and ablation zone‐to‐liver) were calculated with and without subtraction images and compared using Wilcoxon signed rank test. Interobserver variability was computed using Kappa (κ) statistics.

Results:

Residual/recurrent tumor was present in 8 (23.5%) of 34 tumors. Accuracy of detecting residual/recurrent tumor with subtraction images and interobserver agreement (κ = 0.72, good) were better than accuracy of detecting residual/recurrent tumor and interobserver agreement (κ = 0.57, moderate) of enhanced MR images without subtraction. Mean CNR of subtraction images was significantly higher than that of enhanced MR images for tumoral enhancement‐to‐liver (0.2 ± 5 versus 11.6 ± 14.4, P = 0.03), tumoral enhancement‐to‐ablation zone (10.1 ± 12.5 versus 34.4 ± 29.4, P = 0.02), and ablation zone‐to‐liver (11.8 ± 13.3 versus 102.5 ± 238.4, P = 0.03).

Conclusion:

When using MRI, subtraction images help both detect and exclude residual/recurrent tumor following percutaneous liver ablations. J. Magn. Reson. Imaging 2013;37:407–413. © 2012 Wiley Periodicals, Inc.     

MR appearances of radiofrequency thermal ablation region: histopathologic correlation with dog liver models and an autopsy case

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the utility of magnetic resonance (MR) imaging for indicating the extent of true tissue necrosis of the liver after radiofrequency (RF) ablation in comparison with histopathologic findings in dog models and an autopsy case. MATERIALS AND METHODS: RF ablation of the liver parenchyma was performed on three dogs under general anesthesia. MR appearances of the RF-ablated regions on T1-weighted fast-low angle shot (FLASH; repetition time/echo time [TR/TE]/flip angle: 120/3.8/70),T2-weighted turbo spin echo (3000/80/echo train = 25) and contrast-enhanced T1-weighted images were compared with histopathologic findings. An autopsy case with hepatocellular carcinoma was also enrolled in this study. RESULTS: All ablated regions showed three zones on T1-weighted FLASH images: a central zone with low intensity, a broad hyperintense middle zone, and a surrounding hypointense band. The central and middle zones corresponded to the degrees of coagulation necrosis observed during histopathologic examination, whereas no viable cells were seen in these zones during the microscopic examination using nicotinamide adenine dinucleotide diaphorase stain. The surrounding hypointense band corresponded to sinusoidal congestion in the acute phase and to fibrotic change in the subacute phase. CONCLUSION: MR imaging using the FLASH sequence can accurately determine the extent of the necrotic area after RF ablation.     

肝癌冷冻消融治疗中CT和MRI引导效果对照研究

目的 探讨CT和MR两种影像技术在肝癌冷冻消融治疗中的价值.方法 121例肝癌患者共131个病灶行氩氦刀治疗,其中男73例、女48例,平均年龄(60±8)岁,61例行CT引导下冷冻消融、60例行MR引导下冷冻消融.CT引导采用大孔径16层扫描仪,带有CT透视功能;MR引导采用0.35 T开放式扫描仪,辅助红外导航仪,应用快速梯度回波和快速自旋回波扫描序列.氩氦刀采用MR兼容冷冻系统,冷冻探针为17 G、外径1.47 mm.根据病灶位置、形态、毗邻结构,采用多针组合,适形冷冻.冷冻消融模式为2次冻-融循环消融法,术中间断扫描监测病灶消融情况.以平均扫描时间、病灶显示及冰球监测、肿瘤消融有效率、并发症、生存时间为评价指标,肿瘤消融有效率的比较采用x2检验.结果 CT引导平均扫描时间为(5.6±1.8)min,MR引导平均扫描时间(22.0±2.6)min.CT在病灶精细程度及肋骨等结构的显示方面优于MR;CT扫描中金属探针可以产生伪影,难于显示碘油栓塞后病灶的冰球形成情况.MR在显示、导引和监测邻近膈肌、肝门、胆囊区等特殊部位病灶方面优于CT;而且MR不受高密度栓塞剂及金属探针的影响,在显示病灶、监测冰球形成和病灶消融情况等方面优于CT.但是,MR扫描时间长,低场强开放式MR图像质量不及CT.两组病例随访12个月,CT引导组和MR引导组1年生存率分别为90.2%(55/61)、90.0%(54/60),术后1个月两组病例肿瘤消融有效率分别为75.4%(46/61)、83.4%(50/60).(x2检验=4.4056,P＜0.05).结论 CT引导快速直接,尤其对穿刺路径中的肋骨等结构显示优于MR.MR具有多平面成像对显示病灶与肿瘤的关系,监测治疗效果方面优于CT,尤其在显示、导引和监测邻近膈肌、肝门、胆囊区等特殊部位病灶的穿刺消融优于CT引导.     

Perfusion-modulated MR imaging-guided radiofrequency ablation of the kidney in a porcine model.

OBJECTIVE: This study was performed to test the hypothesis that temporary renal ischemia will result in increased thermal lesion size during radiofrequency thermal ablation in the kidney. MATERIALS AND METHODS: Twelve kidneys were treated in six pigs that were placed under general anesthesia in the MR suite, using a 0.2-T open C-shaped MR imaging system. A 4-cm-long, 14-mm-diameter balloon catheter was placed into the aorta using a transfemoral approach, and the balloon was positioned proximal to the renal arteries via guidance with MR imaging. A 2-cm exposed-tip MR-compatible 17-gauge radiofrequency electrode was placed into one kidney under MR fluoroscopy using fast imaging with steady-state free precession (FISP) sequences. Thermal ablation was performed with the electrode tip temperature maintained at 90 +/- 2 degrees C for 10 min. This procedure was repeated in the contralateral kidney. The balloon was inflated during one ablation. Postablation images were obtained, the pigs were sacrificed, and both kidneys of each animal were harvested for pathologic correlation. RESULTS: Technical success was achieved in all animals. The lesion measured 14.2 +/- 2.2 mm (mean +/- standard deviation) for the ischemic kidney versus 8.0 +/- 2.6 mm in the normally perfused kidney (p = 0.00002). No significant complications were noted. In all images, thermal lesions displayed low signal intensity with a sharp rim of high signal intensity best visualized using short tau inversion recovery (STIR) sequences with a mean accuracy of 1.3 +/- 1.2 mm when compared with pathologic findings and a mean contrast-to-noise ratio of 4.9 +/- 2.5. CONCLUSION: We accept the hypothesis that temporary renal ischemia leads to a significantly increased radiofrequency ablation lesion size. We conclude that catheter-based balloon perfusion reduction is feasible, that the procedure does not lead to major complications, and that it can be performed using MR imaging as the sole imaging modality.