MR-guided aspiration biopsy: needle design and clinical trials

Nonferrous needles of pure brass, titanium, or copper, and ferrous needles of different alloys of stainless steel were analyzed for the size, area, and distribution of the image artifact created when the needles were placed in a 0.6-T magnet. Results demonstrated that a stainless steel prototype needle (type 316) would be visible on magnetic resonance images and would provide an artifact similar to that seen in computed tomographic-guided biopsies. Further testing of this prototype included assessment of the effect on the artifact when changes were made in annealing properties, gauge, length, needle-tip geometry, pulse sequence, and orientation relative to the magnetic field. To date, three human liver biopsies have been successfully and safely performed using a stainless steel type 316 needle.     

MR-guided microwave ablation in hepatic tumours: initial results in clinical routine

Objectives

Evaluation of the technical success, patient safety and technical effectiveness of magnetic resonance (MR)-guided microwave ablation of hepatic malignancies.

Methods

Institutional review board approval and informed patient consent were obtained. Fifteen patients (59.8 years?±?9.5) with 18 hepatic malignancies (7 hepatocellular carcinomas, 11 metastases) underwent MR-guided microwave ablation using a 1.5-T MR system. Mean tumour size was 15.4 mm?±?7.7 (7-37 mm). Technical success and ablation zone diameters were assessed by post-ablative MR imaging. Technique effectiveness was assessed after 1 month. Complications were classified according to the Common Terminology Criteria for Adverse Events (CTCAE). Mean follow-up was 5.8 months?±?2.6 (1-10 months).

Results

Technical success and technique effectiveness were achieved in all lesions. Lesions were treated using 2.5?±?1.2 applicator positions. Mean energy and ablation duration per tumour were 37.6 kJ?±?21.7 (9-87 kJ) and 24.7 min?±?11.1 (7-49 min), respectively. Coagulation zone short- and long-axis diameters were 31.5 mm?±?10.5 (16-65 mm) and 52.7 mm?±?15.4 (27-94 mm), respectively. Two CTCAE-2-complications occurred (pneumothorax, pleural effusion). Seven patients developed new tumour manifestations in the untreated liver. Local tumour progression was not observed.

Conclusions

Microwave ablation is feasible under near real-time MR guidance and provides effective treatment of hepatic malignancies in one session.

Key Points

? Planning, applicator placement and therapy monitoring are possible without using contrast enhancement ? Energy transmission from the generator to the scanner room is safely possible ? MR-guided microwave ablation provides effective treatment of hepatic malignancies in one session ? Therapy monitoring is possible without applicator retraction from the ablation site

     

Performing MR-guided biopsies in clinical routine: factors that influence accuracy and procedure time

Objective  

To assess the accuracy, the duration and factors that influence the duration of MRI-guided liver or soft-tissue biopsies.     

MR导向下穿刺活检的临床路径:影响准确性及操作时间的因素

目的旨在评价MR导向下肝脏或软组织穿刺活检的准确性、持续时间及其相关影响因素。方法回顾性分析1.5TMR导向下19例肝脏活检及19例软组织活检的病例。评价其诊断效果和并发症。将介入操作时程分为准备期、穿刺期和控制期。分析操作时间与靶区大小、皮肤至靶区距离、     

MR-guided radiofrequency ablation using a wide-bore 1.5-T MR system: clinical results of 213 treated liver lesions

Objective

To evaluate the technical effectiveness, technical success and patient safety of MR-guided radiofrequency (RF) ablation of liver malignancies using a wide-bore 1.5-T MR system.

Methods

In 110 patients, 56 primary liver lesions and 157 liver metastases were treated in 157 sessions using percutaneous RF ablation. Mean lesion diameter was 20?mm (range 4–54?mm). All planning, procedural and post-interventional control MR investigations were carried out using a wide-bore 1.5-T MR system. Technical success was assessed by a contrast-enhanced MR liver examination immediately after the intervention. Technique effectiveness was assessed by dynamic hepatic MR study 1?month post ablation; mean follow-up period was 24.2?months (range 5–44).

Results

Technical success and technique effectiveness were achieved in 210/213 lesions (98.6?%). In 18/210 lesions (8.6?%), local tumour progression occurred 4–28?months after therapy. Seven of these 18 lesions were treated in a second session achieving complete ablation, 6 other lesions were referred to surgery. Overall RF effectiveness rate was 199/213 (93.4?%); overall therapy success (including surgery) was 205/213 (96.2?%). Two major complications (1.3?%) (bleeding and infected biloma) and 14 (8.9?%) minor complications occurred subsequent to 157 interventions.

Conclusion

Wide-bore MR-guided RF ablation is a safe and effective treatment option for liver lesions.

Key Points

? Magnetic resonance-guided radiofrequency ablation offers various options for monitoring therapy. ? All steps of RF ablation carried out in 1.5-T wide-bore system. ? Therapeutic decisions were based on T1-weighted imaging. ? Technical success and technical effectiveness were high. ? Local tumour progression rate was 8.6?% over a 24-month mean follow-up.     

213例使用宽口径1.5TMR设备引导下射频消融治疗肝脏病变

目的探讨使用宽口径1.5TMR设备引导下射频消融(RF)治疗肝脏恶性肿瘤的有效性、成功性和安全性。方法在110例病人中,56个原发性肝癌病变和157个肝转移病变接受了157次经皮射频消融治疗。平均病灶直径为20mm(4～54mm)。所有的治疗计划、程序和介入治疗后监测均在宽口径1.5TMR设备下进行。介入治疗后立即行肝脏MR增强扫描检查对技术的成功性进行评估。通过肝脏的动态MR成像,对消融技术治疗1个月后的有效性进行了研究评估,平均随访时间为24.2个月(范围5～44个月)。结果 210/213个病变(98.6%)达到技术成功和技术有效。18/210病变(8.6%)治疗4～28个月后发生肿瘤局部复发浸润。18个病变中的7个取得二次完全消融治疗,其他6例病变行手术治疗。总体射频消融(RF)有效率为93.4%(199/213),整体治疗成功率(包括手术)为96.2%(205/213)。发生2种严重并发症(1.3%)(出血和感染性胆汁瘤)和14种(8.9%)轻微并发症,其中有157个病变接受了干预措施。结论宽口径MR引导下射频消融治疗肝脏病变是一种安全、有效的治疗方法。     

Electromagnetic tracking for thermal ablation and biopsy guidance: clinical evaluation of spatial accuracy

PURPOSE: To evaluate the spatial accuracy of electromagnetic needle tracking and demonstrate the feasibility of ultrasonography (US)-computed tomography (CT) fusion during CT- and US-guided biopsy and radiofrequency ablation procedures. MATERIALS AND METHODS: The authors performed a 20-patient clinical trial to investigate electromagnetic needle tracking during interventional procedures. The study was approved by the institutional investigational review board, and written informed consent was obtained from all patients. Needles were positioned by using CT and US guidance. A commercial electromagnetic tracking device was used in combination with prototype internally tracked needles and custom software to record needle positions relative to previously obtained CT scans. Position tracking data were acquired to evaluate the tracking error, defined as the difference between tracked needle position and reference standard needle position on verification CT scans. Registration between tracking space and image space was obtained by using reference markers attached to the skin ("fiducials"), and different registration methods were compared. The US transducer was tracked to demonstrate the potential use of real-time US-CT fusion for imaging guidance. RESULTS: One patient was excluded from analysis because he was unable to follow breathing instructions during the acquisition of CT scans. Nineteen of the 20 patients were evaluable, demonstrating a basic tracking error of 5.8 mm +/- 2.6, which improved to 3.5 mm +/- 1.9 with use of nonrigid registrations that used previous internal needle positions as additional fiducials. Fusion of tracked US with CT was successful. Patient motion and distortion of the tracking system by the CT table and gantry were identified as sources of error. CONCLUSIONS: The demonstrated spatial tracking accuracy is sufficient to display clinically relevant preprocedural imaging information during needle-based procedures. Virtual needles displayed within preprocedural images may be helpful for clandestine targets such as arterial phase enhancing liver lesions or during thermal ablations when obscuring gas is released. Electromagnetic tracking may help improve imaging guidance for interventional procedures and warrants further investigation, especially for procedures in which the outcomes are dependent on accuracy.     

Some technical parameters influencing the precision and accuracy of fragment size determination for RFLP's

Summary A comparison was carried out between 3 computer-assisted systems for the estimation of DNA fragment length: (1) the Digitab system (developed at our institute), (2) the FBI analysis system (FBI Quantico, USA) and (3) the BioImage system (Waters/Millipore, USA). Both the FBI system and the Biolmage system were found to be much more precise than the manual Digitab system. In an additional experiment, a possible influence of the field strength on the accuracy of fragment size measurement was checked. Lowering the field strength to approx. 1 V/cm led to a statistically significant increase in the measured fragment size.     

磁共振引导下肝肿瘤热消融治疗现状与进展

影像引导热消融治疗肝恶性肿瘤得到广泛认可并成为肝肿瘤微创治疗的首选方案.MR软组织分辨率高、无辐射损伤、任意角度成像和无创热成像等优势,可提高肿瘤定位精度并实时显示消融过程、监测消融范围,为精准热消融提供助力.近年来,随着MR引导下肝肿瘤热消融逐渐成熟,热消融治疗近膈部、血管等特殊部位肝肿瘤成为可能.本文旨在对MR引导...     

Interactive MR-guided biopsies of maxillary and skull-base lesions in an open-MR system: first clinical results

The purpose of this study was to explore the potential of interactive MR-guided biopsies in the maxillary and skull base region using a 0.5-T open-configuration scanner in patients with tumours affecting the maxilla or skull base. Ten patients with cystic or solid tumours affecting the maxillary and skull base regions underwent MR-guided biopsy in a superconducting, open 0.5-T MR system equipped with an optical frameless stereotaxic system. T2-weighted spin-echo images were acquired prior to and following biopsy, which was performed with 18- or 22-G needles using an enoral or percutaneous approach following infiltration of the skin, mucosa and periosteum with local anaesthetics. The position of the needle tip was continuously updated on fast T1-weighted gradient-recalled-echo images (TR 19 ms, TE 7.1 ms, flip angle 30 °, slice thickness 1 cm, field of view 24 × 24 cm) using the frameless stereotaxic system. In addition, the needle was identified based on the associated susceptibility artefact in all three planes. Once the target lesion had been reached, cytology material was aspirated. All ten patients tolerated the interactive MR-guided biopsies well without complications. Vital structures, including the brain, neurovascular bundles, vessels and eyes, were visualized on MR imaging and could be spared. There was no difference in the use of 18- or 22-G non-ferromagnetic needles concerning the susceptibility artefact. Sufficient material for cytological analysis was obtained in nine of ten cases. The mean biopsy time was 15 min. Interactive MR-guided biopsies of the head and neck in an open system are technically feasible and safe. Monitoring of the needle path in multiple planes permits the interactive adjustment of the needle course in near real time. Interactive MR-guided biopsies may well replace open surgical procedures in the maxillary region in selected patients. Received: 26 May 1998; Revision received: 18 August 1998; Accepted: 7 September 1998     

MR-guided radiofrequency ablation in a 0.2-T open MR system: technical success and technique effectiveness in 100 liver tumors

PURPOSE: To evaluate the feasibility and technique effectiveness of magnetic resonance (MR)-guided radiofrequency (RF) ablation of hepatic malignancies. MATERIALS AND METHODS: In 64 patients, 100 primary (N = 19) or secondary (N = 81) liver tumors (mean diameter = 24.7 mm; range = 4-60 mm) were treated with 87 sessions of MR-guided RF ablation. The entire ablation procedure was carried out at an 0.2-T open MR system by using MR-compatible internally cooled electrodes. T2-weighted turbo spin echo sequences (TR/TE = 3500 msec/110 msec) were used to monitor thermally induced coagulation. Technique effectiveness was assessed four months after the last RF ablation by dynamic MR imaging at 1.5-T. RESULTS: MR-guided RF ablation procedures were technical successful in 85 of 87 (97.7%) assessed at the end of each session. Complete coagulation was intended in 99 of 100 tumors. Technique effectiveness was observed in 92 of 99 (92.9%) of these tumors. To achieve complete coagulation 82 of 92 (89.1%) tumors required a single session. T2-weighted sequences were accurate to monitor the extent of coagulation and were supportive to guide overlapping ablation. There were two of 87 (2.3%) major and seven of 87 (8.0%) minor complications. CONCLUSION: MR-guided RF ablation is a safe and effective therapy in the treatment of hepatic malignancies. MR imaging offers an accurate monitoring of thermally-induced coagulation, thus enabling complete tumor coagulation in a single session.     

MR-guided laser thermal ablation of primary and secondary liver tumours

AIM: To test the hypothesis that magnetic resonance (MR)-guided hepatic tumour ablation is (i) safe and feasible, (ii) is associated with favourable patient survival, and (iii) decreases viable tumour. MATERIALS AND METHODS: One hundred and twenty-five MR-guided laser thermal ablations (LTA) were performed on 35 patients with hepatocellular carcinoma (HCC, n=19), hepatic metastases (n=11, mainly colorectal) and carcinoid liver tumours (n=5). RESULTS: Mean overall survival was 14.8 months (HCCs 14.6 months, metastases 15.2 months). Near real-time T1-weighted colourized thermal maps correlated moderately with follow-up gadolinium-enhanced MR imaging in predicting ablated tumour area (Pearson correlation coefficient=0.5). There was a significant difference in percentage enhancing pre- and post-LTA (Wilcoxon signed ranks test=0.0001). An average of 50.7% of tumour was ablated by each treatment. In patients with multiple liver tumours ablated tumours grew significantly less than untreated tumours (108%compared with 196% growth, follow-up period 5.8 months, WSRTp=0.07). CONCLUSION: MR- guided LTA of primary and secondary liver tumours is safe, feasible, and significantly decreased amount of enhancing or viable tumour. MR-guided LTA produces a better survival in patients with HCC than would be expected in untreated patients, and has a mean survival in patients with metastases at least equal to the longest median survival in untreated patients.     

Three-dimensional model of lesion geometry for evaluation of MR-guided thermal ablation therapy

RATIONALE AND OBJECTIVES: High-radiofrequency energy is used clinically to ablate pathologic tissue with interventional magnetic resonance (MR) imaging. For many tissues, resulting lesions have a characteristic appearance on contrast-enhanced T1- and T2-weighted MR images, with two boundaries enclosing an inner hypointense region and an outer hyperintense margin. Geometric modeling of three-dimensional thermal lesions in animal experiments and patient treatments would improve analyses and visualization. MATERIALS AND METHODS: The authors created a model with two quadric surfaces and 12 parameters to describe both lesion surfaces. Parameters were estimated with iterative optimization to minimize the sum of the squared shortest distances from segmented points to the model surface. The authors validated the estimation process with digital lesion phantoms that simulated varying levels of segmentation error and missing surface information. They also applied their method to in vivo images of lesions in a rabbit model. RESULTS: For simulated phantom lesions, the lesion geometry was accurate despite manual segmentation error and incomplete surface data. Even when 50% of the surface was missing, the median error was less than 0.5 mm. For all in vivo lesions, the median distance from the model surface to data was no more than 0.58 mm for both inner and outer surfaces, less than a voxel width (0.7 mm). The interquartile range was 0.89 mm or less for all data. CONCLUSION: The authors' model provides a good approximation of actual lesion geometry and is highly resistant to missing segmentation information. It should prove useful for three-dimensional lesion visualization, volume estimation, automated segmentation, and volume registration.     

Sub-acute changes in lesion conspicuity and geometry following MR-guided radiofrequency ablation

PURPOSE: To evaluate MR signal and lesion zone volume evolution through the sub-acute phase following image-guided radiofrequency (RF) thermal ablation. MATERIALS AND METHODS: For many tissues, including muscle and liver, thermal lesions that result from RF heating have a characteristic two-boundary appearance featuring an inner core (zone I) surrounded by a hyper-intense margin (zone II) and normal tissue (zone III), found in both T(2) and contrast enhanced (CE) T(1)-weighted MR images, both immediately post-ablation and four days later. First, we compared corresponding points between manually segmented zone boundaries apparent in T(2)- and CE T(1)-weighted images. Second, we examined the contrast-to-noise ratio (CNR) between all zone combinations. Third, we quantified the volume of zone I, zone II, and the entire lesion using a three-dimensional lesion geometry model fitted to segmented images. RESULTS: On a slice-by-slice basis, no statistically significant differences were found between zone boundaries apparent in T(2) and CE T(1)-weighted images. The contrast to noise ratio (CNR) of zone I vs. zone II, zone I vs. background muscle, and zone II vs. background muscle was always equal or greater for T(2)-weighted images than for CE T(1)-weighted images. In addition, by day four, zone II significantly increased in intensity compared to background muscle. The median Zone I volume increase was 44.2% (42.6%) using T(2) weighted images and 55.5% (68.7% interquartile range) using CE T(1)- weighted images. This expansion likely corresponds to an enlargement of the ablated, coagulative necrosis, region. The median Zone II volume increase was 15.0% (42.6%) using T(2)- weighted images 1.5% (38.8%) using CE T(1)-weighted images. CONCLUSIONS: 1) There are no significant differences between the apparent zone boundaries in T(2)- and CE T(1)-weighted images; 2) CNR is equal or greater for T(2)-weighted images as compared to CE T(1)-images; and 3) both the inner and outer lesion zone volumes typically increase several days post-ablation.     

MR-guided radiofrequency ablation of hepatic malignancies at 1.5 T: initial results

Purpose

To assess the feasibility of magnetic resonance (MR)‐guided radiofrequency ablation (RFA) of hepatic malignancies using a high‐field MR scanner.

Materials and Methods

A total of 10 patients with 14 primary (N = 1) or secondary (N = 13) hepatic malignancies underwent MR‐guided RFA using a closed‐bore 1.5 T MR scanner. Lesion diameters ranged from 2.0 cm to 4.7 cm. RFA was performed using a 200‐W generator in combination with a 3.5‐cm LeVeen electrode applying a standardized energy protocol.

Results

RFA was technically feasible in all patients. Necrosis diameter ranged from 2.5 cm to 6.8 cm. The mean follow‐up period is 12.2 ( 1 - 18 ) months. In nine out of 10 patients, local tumor control was achieved. For this purpose, a second CT‐guided RFA was required in two patients. In four patients, multifocal hepatic tumor progression occurred, with the treated lesion remaining tumor‐free in three of these patients. Two patients showed extrahepatic tumor progression. Four patients remained tumor‐free. No major complications occurred.

Conclusion

MR‐guided RFA of hepatic malignancies in a closed‐bore high‐field MR scanner is technically feasible and safe. It can be advantageous in locations considered unfavorable for CT‐guided puncture or in patients in which iodinated contrast material is contraindicated. J. Magn. Reson. Imaging 2004;19:342–348. © 2004 Wiley‐Liss, Inc.

     

3.0T 闭合式大孔径MR引导下肝癌微波消融15例

【摘要】 目的 探讨3.0T 闭合式大孔径MR引导原发性肝癌微波消融的可行性和有效性。方法 回顾性分析15例原发性肝癌患者（24个病灶）采用3.0T 闭合式大孔径MR引导行微波消融术。记录病灶大小、扫描序列、消融参数、并发症,比较术前、术后2个月生化指标和甲胎蛋白（AFP）,采用mRECIST评价肿瘤局部消融情况。 结果 肿瘤最大径均值2.6 cm,扫描序列T1 Vibe fs 16 s, T2 haste fs 16 s。单病灶平均功率/时间: 62.0 W/14.8 min。次要并发症发生率20%,无大出血、感染、胆瘘、肝功能衰竭等主要并发症。术前术后2个月血常规、肝肾功能无明显变化（P＞0.05）,甲胎蛋白明显下降,（944.9 ± 602.0） μg/L比（ 40.2 ± 37.1） μg/L, 差异有统计学意义（P＜0.05）。病灶评价完全缓解率（CR）95.8%（23/24）,部分缓解率（PR）4.2%（1/24）,局部控制率（LCR）100%。结论 3.0T 闭合式大孔径MR引导下肝癌微波消融术安全可行有效。     

MR-guided vacuum-assisted breast biopsy: accuracy of targeting and success in sampling in a phantom model

An 11-gauge MR-compatible system was designed for use in magnetic resonance vacuum-assisted breast biopsy. The system uses a detachable needle with minimal artifact to allow imaging after placement and before biopsy to confirm lesion location. A phantom study involving 16 biopsies of lesions smaller than 10 mm was conducted to assess the performance of this system. Fifteen (94%) of 16 biopsies resulted in successful lesion sampling. Eighty-five percent of all core samples contained specimen materials targeted lesion material. Further research to evaluate the efficiency, accuracy, and safety of this system in a patient population is recommended.     

Reporting of ventilation perfusion images for pulmonary embolism: accuracy and precision

Thirty-four hospital patients with suspected pulmonary embolism (PE) had ventilation perfusion (VP) imaging after pulmonary angiography to assess the performance of highly specific criteria for diagnosis of PE and to evaluate the precision of image reporting. A diagnostic result was obtained from VP imaging in 21 of 34 patients giving a sensitivity for PE of 80% and a specificity of 100% in this subgroup. Six of 11 patients with PE had an indeterminate study which reduced the overall sensitivity of the technique for PE in the whole group. A critical analysis of image reporting by two readers gave an 85% inter-observer agreement on ranking as diagnostic or indeterminate for PE (k 0.69) and 91%-94% agreement for consensus reproducibility (k 0.82). We conclude that the degree of accuracy and precision of reporting that can be obtained using specific criteria will provide a reliable diagnosis in a significant number of patients suspected of having PE. Consensus reporting by two readers is shown to be more reliable than individual reporting.