|Year : 2022 | Volume
| Issue : 2 | Page : 384-390
Feasibility and efficacy of superconducting open-configuration magnetic resonance-guided microwave ablation of malignant liver tumors with real-time imaging sequences
Hui Yuan, Lujun Shen, Han Qi, Xiucheng Wang, Hongtong Tan, Fei Cao, Tao Huang, Da Li, Yan Zhang, Ting Wang, Ying Wu, Weijun Fan
Department of Minimally Invasive Interventional Therapy, Sun Yat-sen University Cancer Center; State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Sun Yat-sen University, Guangzhou, People's Republic of China
|Date of Submission||20-Sep-2021|
|Date of Decision||17-Dec-2021|
|Date of Acceptance||07-Feb-2022|
|Date of Web Publication||20-May-2022|
Department of Medical Imaging and Interventional Radiology Cancer Center, Sun Yat-sen University #651 Dongfeng East Road, Guangzhou - 510 060
People's Republic of China
Source of Support: None, Conflict of Interest: None
Objective: To evaluate the safety and effectiveness of open superconducting magnetic resonance (MR)-guided microwave ablation of liver tumors and explore feasibility of real-time imaging sequence-guided needle insertion technique.
Materials and Methods: Medical records of December 2019–May 2021 of microwave ablations of liver tumors under MR guidance in XX University Cancer Center were reviewed. Real-time imaging-guided puncture technique refers to real-time insertion and adjusting the position of a microwave applicator under a fast imaging sequence. The safety and efficacy of the procedure among the enrolled patients were assessed.
Results: Twenty-six patients underwent 27 procedures, with 30 lesions ablated (long diameter: 1.51 ± 0.81 cm, short diameter: 1.30 ± 0.61 cm). There were 20 cases of primary liver cancer and 10 of liver metastases. All lesions were identified by MR imaging (MRI), and all procedures were successfully performed using the finger positioning method for puncture sites. Five patients underwent real-time guided needle insertion techniques. Further, the microwave applicators reached the target position at once, and the entire insertion process was completed within 3 min. The completion rate of the real-time guided needle insertion technology was 100%, and 25 (92.6%) patients had minor complications. No severe complications were observed, and the technical success rate of 30 MRI-guided lesions was 100%. Finally, the complete ablation rate of the MRI-guided ablation after the first procedure was 93.1%.
Conclusion: Open MR-guided microwave ablation is safe and effective in treating liver tumors. Furthermore, real-time imaging sequence-guided puncture technique under MRI is feasible and efficient.
Keywords: Liver cancer, microwave ablation, MR guidance, open-configuration MR, real-time imaging
|How to cite this article:|
Yuan H, Shen L, Qi H, Wang X, Tan H, Cao F, Huang T, Li D, Zhang Y, Wang T, Wu Y, Fan W. Feasibility and efficacy of superconducting open-configuration magnetic resonance-guided microwave ablation of malignant liver tumors with real-time imaging sequences. J Can Res Ther 2022;18:384-90
|How to cite this URL:|
Yuan H, Shen L, Qi H, Wang X, Tan H, Cao F, Huang T, Li D, Zhang Y, Wang T, Wu Y, Fan W. Feasibility and efficacy of superconducting open-configuration magnetic resonance-guided microwave ablation of malignant liver tumors with real-time imaging sequences. J Can Res Ther [serial online] 2022 [cited 2022 Jul 7];18:384-90. Available from: https://www.cancerjournal.net/text.asp?2022/18/2/384/345529
Hui Yuan, Lujun Shen, Han Qi contributed equally to this work.
| > Introduction|| |
Percutaneous ablation is safe and effective in treating liver tumors clinically. According to the recommendation by European Association for the Study of the Liver clinical practice guidelines, percutaneous ablation is the first-line treatment for early-stage hepatocellular carcinoma, with a similar outcome to surgical resection. Also, it has become a preferred treatment option for patients with stages 0 and a liver cancer. Percutaneous ablation technology, including chemical ablation, radiofrequency ablation, microwave ablation, cryoablation, and so on, is constantly updated and developed. Among the thermal ablation methods, radiofrequency and microwave ablation, which are the most representative, have long been the first-line technologies for treating primary liver cancer.,,, However, microwave ablation is a relatively new technology compared with radiofrequency ablation. It has a larger ablation zone and supports multiple applicator ablation simultaneously to further expand the ablation area and improve ablation efficiency. In treating early-stage primary liver cancer, the ablation time required for microwave ablation is significantly reduced, the hospitalization cost is lower, and there are no statistically significant differences in complications and postoperative survival compared with radiofrequency ablation. Moreover, the efficacy of microwave ablation is better than radiofrequency ablation for lesions at specific locations.,,,,
Ultrasound and computed tomography (CT) are the most common techniques for imaging guidance during ablation, and each has its advantages.,,,,, Ultrasound-guided liver microwave ablation is convenient and gives real-time image display, however, gas interference makes it limited. Although CT guidance can make up for the shortcomings of ultrasound guidance and has many applications, CT scans have ionizing radiation and metal artifacts, degrading image quality. Additionally, when the enhanced scan is not done, it has limitations in observing iso-density lesions and the range of ablation zone. By contrast, MR guidance has the advantage of multi-parameter, multi-plane imaging, which can clearly and accurately display the location of a lesion and its relationship with adjacent structures. Furthermore, using a real-time imaging sequence, combined with open equipment, provides a guarantee for realizing real-time applicator insertion.,,, Therefore, this study evaluates the safety and effectiveness of microwave ablation of liver tumors under MR guidance and explores the feasibility of real-time imaging sequence-guided needle insertion technique.
| > Materials and Methods|| |
This study was approved by the institution's ethics committee and was granted a waiver of individual informed consent. The enrollment criteria for MR-guided liver microwave ablation were (1) no contraindication to MRI scanning; (2) the number of metastases in the liver is less than four; (3) the diameter of the target lesion for ablation ≤5 cm. From December 2019 to May 2021, 26 patients underwent microwave ablation treatment for 30 liver tumors under open MR guidance in XX University Cancer Center.
The guidance device is an open Philips Panorama HFO 1.0T MR, and the machine room is equipped with a degaussing display screen that can display the interface content of the console. Special coils for ablation are used, and the details of the conventional scanning sequence are shown in [Table 1]. The treatment modality is a Nonmagnetic Microwave Therapy Device (VISON MEDICAL lnc. Nanjing). In addition, the MR theater is equipped with a nonmagnetic electrocardiogram (ECG) monitor. The above equipment can be seen in [Figure 1].
|Table 1: Scanning sequence used under open MR guidance and important parameters|
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|Figure 1: Equipment configuration in MRI theater. (a) Superconducting 1.0 T open MRI machine. Special coil for interventional ablation. Non-magnetic screen. (b) Non-magnetic microwave ablation applicator, strong flexibility, not easy to break. (c) Non-magnetic ECG monitor. (d) Non-magnetic microwave ablation therapy instrument|
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All MR-guided microwave ablations were performed in accordance with the following procedures: preoperative preparations, preoperative scanning evaluation and positioning, real-time or step-by-step guidance for needle insertion, ablation and imaging evaluation, and postoperative review.
Preoperative preparations: The horizontal plane of the patient's liver area is placed in the center of the coil, and the breathing gate device is placed at the patient's abdominal wall with the largest motion. The nurse connected the ECG monitor, evaluated the patient's vital signs, and checked the patient's intravenous access before the procedure. Furthermore, all procedures were performed under intravenous analgesia.
Preoperative scanning evaluation and positioning: The preoperative scan sequence includes the coronal T2WI sequence and the transverse T2WI and T1WI sequences. The transverse T2WI fat suppression imaging sequence was added when necessary. The relationship between the target lesion and surrounding structures is evaluated by interventional radiologists, and the puncture route is planned. Positioning: finger positioning with a real-time scanning sequence was used to determine the target plane for puncture. When the finger reaches the planned position, a mark is made on the skin's surface [Figure 2]. Then a specialized coil is assembled, followed by skin preparation and draping.
|Figure 2: The puncture point can be found quickly and accurately through the finger positioning technique|
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Real-time and step-by-step applicator insertion: Real-time guidance generated one image every 0.725 s. This scanning frequency can facilitate rapid adjustment of the scanning level, timely evaluation of the applicator location, and real-time applicator insertion. Stepwise scanning guidance used repeated 3D T1-weighted Dixon volumetric interpolated breath-hold sequence. Finally, the results of the two guiding approaches were evaluated by the T2WI transverse image.
Ablation and imaging evaluation: The ablation plan is designed by interventional radiologists based on the size and location of the lesion. Transverse T2W scan (or fat suppression) and transverse T1W scan is performed whenever the ablation session is completed. The ablationists dynamically adjusted the ablation plan or the position of the microwave needle until the ablation zone exceeded at least 0.5 cm of the lesion's margin.
Postoperative review evaluation: The T2W and T1W sequences of the transverse were routinely scanned to evaluate the ablation zone and rule out postoperative complications.
Outcomes of ablation
The primary outcome is the patient's safety, and the secondary outcomes include the effectiveness of the technique and the feasibility of real-time imaging-guided insertion.
The Society of Interventional Radiology classification system was used to assess the patient's safety. Minor complications include (A) no therapy, no consequence; (B) nominal therapy, no consequence, including overnight admission for observation only. Major complications include (C) requiring therapy, minor hospitalization (<48 h); (D) requiring major therapy, unplanned increase in the level of care, prolonged hospitalization (>48 h); (E) permanent adverse sequelae; (F) death.
Treatment success was defined as the ablation zone being displayed and the entire lesion included in the ablation zone. The efficacy of ablation was evaluated by contrast-enhanced MRI or CT one month after completion of the procedure.
Data sources and statistical analysis
All data are obtained from the internal network resources of the hospital. The median and range or mean and standard deviation are provided for ordinal and continuous variables. Finally, all statistical analysis was performed using Statistical Package for the Social Sciences v. 23.0.
| > Results|| |
From December 2019 to May 2021, 26 patients were enrolled, 27 procedures were performed, and 30 lesions were ablated. Among the lesions, 20 were hepatocellular carcinoma, and 10 were metastatic liver lesions (three cases of nasopharyngeal cancer, three cases of colorectal cancer, two cases of renal cancer, and two cases of gastrointestinal stromal tumor). The average age of the 26 patients was 56.5 ± 12.2 years, and there were 24 cases with a single lesion and 3 cases with two lesions. The most common location of the lesions was S4, S6, and S8, with eight, six, and five cases, respectively [Table 2]. The follow-up time for assessing treatment response ranged from 6 to 20 months (median, 14 months).
All lesions were displayed by MRI, and all ablative procedures were performed successfully. The average long diameter of the 30 lesions was 1.51 ± 0.81 cm, and the transverse diameter was 1.30 ± 0.61 cm. Furthermore, the average power used during the treatment was 76.0 ± 9.6 W, the average duration of continuous treatment was 12.0 ± 5.8 min, the range of signal change in the lesion area after treatment was 2.86 ± 0.58 cm; the transverse diameter reached 2.13 ± 0.43 cm. The long and transverse diameters of the ablation zone after treatment were significantly larger than the associated parameters of the lesions [Table 3].
Except for one case of primary liver cancer with no follow-up imaging data, no residual lesion was observed in 27 of the remaining 29 lesions. An enhanced MRI showed that one case had viable residual lesions and four cases with suspicious viable lesions one month after ablation. The follow-up exams of the four suspicious cases showed one case of confirmed residual ablation, whereas the other three had complete ablation. Therefore, the complete ablation rate of local tumors under open MRI guidance reached 93.1%. Notably, the two residual lesions are primary liver cancer and liver metastasis. Thus, of the 20 hepatocellular carcinoma (HCC) cases, except for one with no follow-up imaging data, 18 lesions reached complete ablation. The complete ablation rate of primary liver cancer was 94.7% (18/19). Among the ten liver metastases, nine lesions reached the complete ablation; the complete ablation rate of liver metastases was 90% [Figure 3] and [Figure 4].
|Figure 3: The arrow points to the tumor location, and the triangle points to the ablation applicator. (e) Scan the tumor before the procedure. (f) The positional relationship between the microwave applicator and the tumor can be displayed during the procedure. (g) Intraoperative ablation images show changes in tumor signal. (h) Postoperative scan image showing the location of the tumor entirely covered by the ablation area. (i) One month's review data after the procedure. No residue. (j) Review data three months after the procedure. No recurrence|
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|Figure 4: MR-guided microwave ablation can show the range of ablation zone, and the signal changes in the tumor area after ablation in different sequences are different. (k) The tumor before ablation showed a high signal on the T2WI sequence. (m) After ablation, the tumor had a low signal on the T2WI sequence. (n) The tumor had a low signal at T1WI before ablation. (o) After ablation, the tumor had a high signal on T1WI|
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The SIR classification system was used to assess patients' safety. There were 25 cases of minor complications, and no severe complications were observed [Table 4]. Eighteen (66.7%) cases had class A complications, including mild pain, abdominal discomfort, and elevated liver enzyme. Seven (25.9%) cases had class B complications, of which three had a prominent elevation in the liver enzyme (more than five times the normal upper limit), and four had a small amount of subcapsular hemorrhage. Patients with hemorrhage were injected with hemostatic drugs and observed for more than 30 min. The patients were sent back to the ward after confirmation of no increase in bleeding by MRI scan. All patients with hemorrhage were discharged the next day after proof that the bleeding was stopped through the routine blood test.
The feasibility of real-time guided needle insertion technology
Among 30 tumor ablations, the real-time imaging-guided puncture was adopted in five cases. Through confirmation by the T2WI sequence, the applicator insertion in five cases using the real-time imaging-guided technique was successfully conducted. The error in tip position was less than 3 mm compared with the original plan. Finally, using real-time guided needle insertion technology, the puncture success rate is 100% [Supplement 1].
| > Discussion|| |
Our study showed that the technical success rate of microwave ablation of liver tumors under open MRI guidance was 100%, the one-time complete ablation rate of tumors reached 93.1%, and the incidence of major complications was 15.4%. Previous studies have shown that the technical success rate of CT or ultrasound-guided microwave ablation of the liver tumors ranged from 76.6% to 98.1%, the one-time complete ablation rate ranged from 73% to 94.7%, and the incidence of major complications ranged from 8.2% to 28.6%.,,,,,,, Furthermore, our results on the one-time complete ablation rate under MRI guidance are higher than most published data on ablation under CT/ultrasound guidance, suggesting the advantages of MRI guidance. The incidence of complications is significantly related to the location of the lesions. In a study by Vo Chieu VD et al., the complication rate of lesions in special locations was 24.8%, whereas that of tumors located in the center of the liver was 8.2%, which was different. In the one-time complete ablation rate of the tumor, the size of the lesion had a greater impact on it. Another study by Medhat E et al. highlighted that large lesions (5– 7 cm) were ablated under ultrasound guidance. Also, only 73% of patients achieved complete ablation after multiple punctures were performed in one or two courses. However, Jin T et al. showed that the complete ablation rate of ultrasound-guided microwave treatment of small nodules (0.6–3.8 cm) can reach 91.3%–94.6%. When applying common MR-guided microwave ablation of liver tumors, the technical success rate is 100%, and the complete ablation rate of the tumor reaches 90%–100%.,,,
Previous studies reported that the average length of ablation surgery under ordinary MR guidance is 95–211 min.,,, The average time cost of MR-guided ablation in our center was 155 min (90–200 min), consistent with previous studies. Furthermore, by analyzing the time cost of each process in the procedure, we found that the most influential factors were the selected scan sequence and postoperative complications. For example, the time cost of the T2WI sequence scan is significantly longer than T1WI. Therefore, optimizing the scan sequence and choosing a safe puncture path is crucial in shortening time.
Many scholars have also researched real-time imaging-guided puncture technology under open MR.,,,, For example, Sakarya M et al. proposed MR fluoroscopy for lung biopsy in 2003. Also, He X et al. discussed the application of brain puncture, but scanning time was long, with one image every 2.9 s. When Wang L et al. studied its application in liver biopsy, the speed of the real-time imaging sequence reached that of one image every 1.6 s. Matsui Y et al. further increased the scanning speed of the real-time imaging sequence to one image every 1 s. However, the abovementioned studies are all limited to needle biopsy. Until Dong J et al. studied microwave ablation in live pig liver, they used real-time-guided needle insertion technology to increase the scanning speed to one image every 0.202 s, achieving good experimental results. In this study, we further improved the real-time scanning sequence. By appropriately delaying the scan time to one image every 0.725 s, it can meet the needs of real-time scanning and imaging, considering the image quality to meet the requirements of real-time puncture. Five tumors with suitable positions were selected from 30 lesions, and the real-time imaging guidance technology (RIGT) was adopted when applicator insertion was done, with a technical success rate of 100%. The average time for puncture under RIGT is controlled within 2 min, which is greatly less than the conventional stepwise scanning and puncture approaches.
This open-MR-guided ablation system also has disadvantages. First, although we have a 1.0 T high magnetic field open MR, compared with conventional 3.0 T magnetic field MR, the 1.0 T is relatively low; the image quality and scanning speed are also lower. Second, only five lesions undergo puncture under RIGT, and more practices are needed to further optimize this technique's standard operation procedure and imaging parameters.
Summarily, open superconducting MR-guided microwave ablation of liver tumors is safe and effective, and real-time-guided needle insertion technology is also feasible, which can shorten the puncture time compared with conventionally stepwise scanning and puncture approach.
We would like to thank Ms. Huijuan Lan for pushing us on completing this project.
Financial support and sponsorship
This study was supported by Guangdong Province Key Field R&D Program Project (2019B110233001), National Natural Science Foundation of China (General Program, 81771954) and Guangdong Province Science and Technology Planning Project (2017A010105028).
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]