|Year : 2020 | Volume
| Issue : 5 | Page : 1014-1019
The application of magnetic resonance imaging-guided microwave ablation for lung cancer
Liu Nian-Long1, Yang Bo1, Chen Tian-Ming2, Feng Guo-Dong3, Yin Na1, Wang Yu-Huang1, Shen Wen-Rong1, Chen Shi-Lin4
1 Department of Medical Imaging, Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
2 Department of Medical Imaging, Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University; Department of Surgery, The Third Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
3 Department of Interventional Therapy, Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
4 Department of Thoracic Surgery, Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
|Date of Submission||20-Mar-2020|
|Date of Decision||12-May-2020|
|Date of Acceptance||01-Jul-2020|
|Date of Web Publication||29-Sep-2020|
Department of Thoracic Surgery, Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu 210009
Department of Medical Imaging, Jiangsu Cancer Hospital, Jiangsu Institute of Cancer Research, The Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, Jiangsu 210009
Source of Support: None, Conflict of Interest: None
Context: It is necessary to explore a minimally invasive, effective, and efficient treatment for those lung cancer patients who are poor candidates for surgery.
Aim: This study aimed to investigate the application of microwave ablation (MWA) in the treatment of lung cancer.
Settings and Design: A total of 43 patients with 44 pulmonary lesions were examined following identical procedures before being randomly divided into two groups. The experimental group consists of 17 patients with a total of 18 pulmonary lesions, while the control group consists of 26 patients with a total of 26 pulmonary lesions.
Materials and Methods: The experimental group was treated using magnetic resonance imaging (MRI)-guided MWA while the control group was treated using computer tomography (CT)-guided MWA. A transverse relaxation time-turbo spin echo (T2-TSE) sequence was used for signal collection in the experimental group to determine puncture location and microwave needle position while T2-TSE, T1-turbo field echo, and diffusion-weighted MRI (DWI) sequences were used for timely efficacy evaluation. Whereas in the control group, CT axial scanning was performed to serve similar purposes.
Statistical Analysis Used: A nonparametric Wilcoxon test, median (M [25%, 75%]).
Results: All of the 44 lesions were successfully located on the first attempt. The mean time for scanning and locating lung lesions under MRI and CT guidance were 64.53 and 42.96 min, the mean times of positioning were 12 and 18 min, and the mean durations of MWA were 12.48 and 15.06 min, respectively.
Conclusions: As a minimally invasive method for treating lung tumors, MRI-guided MWA requires fewer localization scans, a shorter MWA duration, no radiation, real-time observation of the curative effect, and it prevents overtreatment.
Keywords: Computer tomography guidance, lung cancer, microwave ablation, magnetic resonance guidance, T1-turbo field echo sequence, transverse relaxation time-turbo spin echo sequence
|How to cite this article:|
Nian-Long L, Bo Y, Tian-Ming C, Guo-Dong F, Na Y, Yu-Huang W, Wen-Rong S, Shi-Lin C. The application of magnetic resonance imaging-guided microwave ablation for lung cancer. J Can Res Ther 2020;16:1014-9
|How to cite this URL:|
Nian-Long L, Bo Y, Tian-Ming C, Guo-Dong F, Na Y, Yu-Huang W, Wen-Rong S, Shi-Lin C. The application of magnetic resonance imaging-guided microwave ablation for lung cancer. J Can Res Ther [serial online] 2020 [cited 2021 Sep 22];16:1014-9. Available from: https://www.cancerjournal.net/text.asp?2020/16/5/1014/296433
| > Introduction|| |
Currently, surgical removal is considered the primary treatment for lung cancer. However, it is not an option for ~70%–80% of patients because of their state of health or advanced tumor progression. Conventional therapies, such as chemoradiotherapy and molecular targeting, are effective but not without their limitations. Therefore, it is necessary to explore a minimally invasive, effective, and efficient treatment for those patients who are poor candidates for surgery. Thanks to technological advances in the medical field, microwave ablation (MWA), which is a new technology to treat tumors locally, has been widely applied to patients worldwide., When observing the real-time therapeutic effect of MWA, magnetic resonance imaging (MRI) has the advantages of multi-angle imaging, no radiation, and high tissue resolution. This study aimed to compare the average localization time, number of localization times, and ablation time of MWA treatment of lung lesions guided by MRI and computed tomography (CT).
| > Materials and Methods|| |
Sampling and pretreatment
[Figure 1] shows the flow of participants through various stages of the trial. A total of 60 patients were randomly divided into two groups of 30 patients. In the experimental group, 13 patients were excluded from the final analysis, most of which failed to complete the experiment due to pain, a pneumothorax, bleeding, or physical exhaustion (10) or rather claustrophobia (2), while another patient changed treatment method. Whereas in the control group, four patients were excluded from analysis, of which three failed to complete the experiment due to a pneumothorax or hemorrhage and one passed away within one month of treatment. For analysis, this left 17 patients in the experimental group and 26 patients in the control group.
[Table 1] shows the baseline characteristics of the patients under analysis. A total of 43 patients with 44 lung lesions, of which 31 lesions were pathologically diagnosed, and 13 lesions were clinically diagnosed, were randomly selected from January 2018 to June 2019. Of the 43 lesions, 22 were located in the left lungs, 15 lesions were located in the right lungs, six lesions were centrally, and one lesion was mediastinal. Six lesions had a diameter of <3 cm, 25 lesions had a diameter of 3–5 cm, and three lesions had a diameter of >5 cm. The average diameter of the lesions was 3.82 cm. The 28 male and 15 female patients were 43–75-year-old, and the median age was 57. Before MWA, all the patients undertook a cardiopulmonary function test to assess the likelihood of bleeding and lung infections and to determine the necessity of applying anticoagulants or bronchodilators.
Equipment and materials
Philips Ingenia 3.0T digital MRI scanner, 16-channel numerically controlled body coil, GE (General Electric Company) 64 row 128-layer Light Speed spiral CT (VCT), All ablation procedures are guided by these devices. VISON's MTC-3C MWA treatment instrument and 18G180CM nonmagnetic needle. The ablation device allows the ablation needle to generate high temperatures inside the tumor, killing the tumor cells.
An Ingenia 3.0T digital MRI scanner installed with SENSE (SENSitivity Encoding) technology was used to conduct MRI during MWA treatment. The coil, which consisted of sixteen units, used a body phased-array coil compatible with SENSE software. The transverse relaxation time-turbo spin echo (T2-TSE) imaging parameters were a 1129 ms repetition time (TR), an 80 ms echo time (TE), and a time of 17s with a receiver (REC) voxel of 0.78/0.78/4.00 mm, angle of 125°, a field of view (FOV) of 400 mm × 330 mm, with 15 axial positions of 4.0 mm thick and layer spacing of 0 mm, and one signal was used. The weighted image (T1)- turbo field echo (TFE) imaging parameters were a 10 ms TR, 2.3 ms, and a time of 14s; REC voxel of 0.93/0.93/4.00 mm, Flip angle of 15°, FOV of 400 mm × 330 mm; 15 axial positions of 4.0 mm thick, a layer spacing of 0 mm, and one signal was used. The diffusion-weighted MRI (DWI) parameters were a TR of 749 ms, TE of 70 ms, and time of 36 s with a REC voxel of 1.25/125/4.00 mm, flip angle of 90°, and FOV of 400 mm × 330 mm.
According to the locations of the lesions, supine, prone, or lateral positions were selected for the scanning patients. In a supine position, the patients placed both hands to the side of the body and relaxed naturally. In a prone or lateral position, the patient placed both hands over the chest and kept steady to maintain a comfortable position. Before MWA, an ablation plan was developed based on the imaging of the lesion, and before scanning, the body of each patient was marked corresponding to their lesions. The insertion angle, depth of the needle, and best puncture point were determined based on the body markings and lesion imaging.
Before local anesthesia, routine disinfection, and draping were performed. Then, a puncture needle was used to penetrate the skin through the puncture point. The ablation needle was inserted through the puncture point and advanced according to the predesigned needle route along the upper edge of the rib to avoid damage to the intercostal nerves, arteries, veins, big blood vessels, trachea, and interlobar pleura and bullae.
For the patients in the experimental group, the needle was inserted with guidance from the T2-TSE sequence images of the MRI, and T2-TSE, T1-TFE, and DWI sequence imaging were performed to observe treatment efficacy in real-time. However, for the control group, the needle was inserted with guided from thin-slice spiral CT imaging. The therapeutic effect was determined by varying the density of the CT imaging and the experiences of the clinical practitioners. The maximum ablation diameter was 5.0 cm. For lesions with a diameter of <5 cm, the treatment was completed in one session. However, for larger lesions or multiple lesions within the lung, multiple puncture treatments, or multiple puncture point treatments were conducted when the patient's health condition allowed. After tumor ablation was completed, ablation was performed on the needle track to prevent implantation. The core treatment temperature was up to 200°C. The treatment time was automatically controlled by the ablation instrument according to the impedance of the ablation needle in the lungs. The one-time ablation power was 60–90 W with duration of 3–5 min. The ablation power and time were adjusted based on the patient's tolerance level. After ablation, imaging results were used to assess the effect of ablation to determine the need for continued ablation and to adjust the ablation location further. The ablation boundary was 0.5 cm outside the lesion edge. During the ablation guided by MRI, T2-TSE, T1-TFE, and DWI, sequence scanning was performed to observe the imaging signals of the lesions. When the target area of the lesion showed a significantly low signal and formed an evident “ring sign,” the ablation was stopped, and needle track ablation was performed. Then, the treatment was terminated. If a lesion signal was found over the edge and the “ring shape” was not closed, then the position of the ablation needle was adjusted to perform the ablation again. However, the CT-guided ablation depended on the clinician's experience to observe changes in the density of the image in the ablation area. The ablation was stopped and followed by needle track ablation when a “bubble sign” or low density of the target area was observed, and then, the treatment was terminated. At the beginning of the treatment, the MRI, and CT-guided MWA localization scan time, the number of localization scans, and MWA duration was recorded. After treatment, the puncture point was covered with sterile gauze, antibiotic fluids were applied, and symptomatic treatment was performed if necessary. The follow-up for CT and MRI was performed 3 days after MWA, and the patients were safely discharged after being determined to be in good general condition. The follow-up CT scans were performed 3, 6, 9, and 12 months after MWA.
puncture success rate, positioning scan time, the number of positioning scans, and MWA time.
The data were processed using SPSS (Statistical Product and Service Solutions) 13.0 statistical software. The comparison of puncture time and the number of puncture times between MWA conducted with the guidance of MRI and computed tomography (CT) was performed using a nonparametric Wilcoxon test, Median (M [25%, 75%]) with P ≤0.05 considered as significant.
| > Results|| |
Of the 18 lesions treated with MRI-guided ablation, six developed a “ring sign” in one treatment, while the other 12 lesions developed a “ring sign” with 2–4 applications of supplementary MWA by adjusting the needle position. Of the 26 lesions treated with CT-guided ablation, nine lesions showed “bubble signs” or “honeycomb signs” during the first treatment. In comparison, the other 17 lesions showed “bubble signs” or “honeycomb signs” with 2–5 applications of supplementary MWA by adjusting the needle positions. [Figure 2] shows the positions, treatments, and efficacy images.
|Figure 2: Comparison of the puncture position and ablation process of the experimental group and control group. (a) Localization image under computed tomography guidance, where the solid arrow indicates the positioning marker; (b and c) computed tomography longitudinal window image, and lung window image, with ablation needles located in the lungs and tumors; (d) computed tomography longitudinal window image of the lesion after ablation, showing “honeycomb signs” in the tumor; (e) magnetic resonance imaging-guided positioning image, where the dotted arrow indicates the positioning marker; (f) microwave ablation needle at transverse relaxation time (T2) in ablation under magnetic resonance imaging guidance and the ablation needle track in the lung and the tumor. (g) Magnetic resonance imaging image of T2 after ablation, where the “ring sign” of the lesion can be seen. (h) diffusion-weighted magnetic resonance imaging image of the lesion after ablation and the original tumor site shows no lesions, as indicated by the bold arrow|
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During the ablation treatment, the average time of MWA localization scanning of lung lesions guided by MRI and CT was 64.53 and 42.96 min, the average localization times were 12 and 18 min, and the average MWA times were 12.48 and 15.06 min, respectively. The puncture time and the number of punctures (P < 0.05) of MRI-guided MWA of lung tumors were significantly lower than MWA guided by CT [Table 2].
|Table 2: Comparison of puncture time and the number of puncture times between microwave ablation conducted with the guidance of magnetic resonance imaging and computed tomography using a nonparametric Wilcoxon test, Median (M [25%, 75%])|
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| > Discussion|| |
MWA is a thermal ablation therapy in interventional radiology, which uses 2450 MHz microwave to generate thermal effects and cause tissue necrosis in solid tumors. Because of its safety, thermal efficiency, and precision at reaching target tissues,, it has become a commonly used as a minimally invasive cancer treatment that is applicable to the nonsurgical treatment of patients and palliative treatment of solid tumors. MWA can accurately and efficiently eliminate cancerous sites of peripheral lung cancer. In addition, as MWA works in the microwave field, there is no high-voltage electric field. Therefore, patients with slow heart rates and those wearing pacemakers and stents can receive treatment safely. For incurable central lung cancers, MWA can also effectively relieve symptoms, such as airway obstruction, obstructive pneumonia, atelectasis, and dyspnea. The curative effect of CT-guided MWA for lung cancer has been reported previously.
Conducting percutaneous MWA of lung lesions follows the same process, whether it is guided by MRI or CT,, and there is not much difference in the ablation time of the lesions. The main considerations are the accurate positioning of punctures, a clear display of the needle tip, fast scanning speed, real-time observation of the effect of ablation, and minimal radiation to the patient. MWA of lung lesions guided by MRI has the advantages of accurate needle insertion, clear needle path display, displaying the relationships between the needle tip and the lesion at different angles, displaying the response of the lesion and normal tissues, timely detection of bleeding, edema, necrosis, pneumothorax, and atelectasis during treatment to evaluate the effect of ablation in real time. By comparison, CT-guided MWA of lung lesions can only evaluate the treatment effect based on the size of the lesion and the ablation time. Currently, MRI provides a radiation- and injury-free examination of the human body. Compared with CT, MRI is not affected by time or frequency. The biggest bottleneck to developing MRI-guided MWA localization of lung lesions is selecting scan sequences. Selecting a sequence with a fast scanning speed and clear image display is essential for MWA treatment of lung lesions. In addition, shortening the time of ablation treatment and ensuring accurate position localization are also requirements. It is best to meet these requirements simultaneously to reduce the number of times ablation needles are inserted.
MWA of lung cancer guided by MRI can facilitate accurate observation of the position of the lesion relative to that of the ablation needle, making it easier for clinicians to locate and insert the needle. The effect of lesion ablation can be observed using MRI simultaneously. The T2-TSE, T1-TFE, and DWI sequences of MRI indicate necrotic and normal tissues, as well as stress edema during ablation.
The sequence used for MRI-guided ablation is characterized by a small number of acquired signals, large voxel, fast speed, and a relatively low signal-to-noise ratio of the obtained signal, so it is not appropriate for routine inspection. Due to local scanning and rapid acquisition, it is insensitive to respiratory movements. Therefore, it is especially suitable for patients who need a quick examination. It is advisable to minimize the microwave treatment time for lung cancer. First, the scanning parameters of the modified sequence can be adjusted to speed up the scanning of the sequence and shorten the total treatment time. In addition, the needle insertion path and treatment plan should be prepared in advance of the start of the positioning and treatment process. The axial and coronal position should be scanned when the needle is inserted to facilitate the accurate positioning of the puncture needle among blood vessels and lesions. It is necessary to continuously adjust the angle and depth of the needle to accurately penetrate the puncture needle into the distal end of the tumor. Only a fast sequence, such as the T1-TFE sequence, can meet this requirement. The T1-TFE, T2-TSE, and DWI sequences are used for effect verification after the treatment. The completion of lung cancer ablation is typically shown by a low internal signal, with a uniform signal, or a few high signals and a circular high signal band around it. The pathological basis for the completion of ablation is primarily the dehydration effect of high-temperature injury, followed by tissue coagulation necrosis.
It is necessary to discuss the possible complications and short-term follow-up to verify the safety and efficacy of MWA therapy. Our study found that pneumothorax and hemorrhage are common complications of MWA. Pneumothorax can occur when the probe is inserted into the tissue, especially in the process of constantly adjusting the insertion position and direction. The presence of a pleural leak can release excess gas into the chest cavity, thus compressing the lung, and shifting the tumor lesion. To prevent this, an artificial pneumothorax was manually aspirated through a 50 ml injection syringe during the operation process. Hemorrhage, which is a potentially life-threatening event, was rare in our study. However, it can occur by damaging an intrapulmonary blood vessel and can be associated with hemoptysis.
As the ablation results show, the CT-guided MWA treatment was simple to operate and short in operation time, but image acquisition was limited to axial scanning, and neither the ablation needles nor the lesions could not be observed stereoscopically. Thus, the positional relationship cannot be viewed in a timely manner, leading to long ablation duration. In contrast, the MRI scan images provided the best contrast between tumors and normal tissues, featuring guidance by multiple sequences and planes, more accurate spatial positioning, fewer positioning times, and no radiation. When MWA is performed in an examination room, MRI guidance can ensure the formulation of a surgical plan, the targeted placement of MWA electrodes, and intraoperative monitoring and manipulation. In addition, MRI-guided MWA has the advantages of less trauma, high safety, and fewer side effects. It provides an effective alternative therapy for patients who have been diagnosed with malignant lung cancer that cannot be surgically removed or who are unwilling to undergo surgery. With the shortening of the scan time and the accumulation of practitioners' surgical experience, the duration of MWA treatment of lung cancer guided by MRI will continue to shorten, and the effect of treatment will keep improving. Therefore, there is reason to believe that this approach will gradually become the mainstream lung cancer treatment in the future and will eventually bring exciting changes to the nonsurgical treatment of lung cancer.
| > Conclusions|| |
Our study shows the feasibility of performing MWA for treating patients with lung cancer in an MRI examination room. The T2-TSE, T1-TFE, and DWI sequences are the preferred examination sequences for MRI-guided MWA treatment. In spite of the advantages that have been dealt with in the discussion section, the disadvantages of MRI-guided MWA treatment should be acknowledged before a discussion of its wider application: (1) the MR imaging time is slightly longer than for CT; (2) the lungs move with breathing, leading to the inconstant position of the lung lesions; (3) complications, such as bleeding or pneumothorax can blur the image; (4) the instruments used in the surgery must be MRI-compatible; and (5) the tip of the microwave antenna suffers from poor visualization.
As a new technology for local tumor treatment, MWA has started being widely used in clinical practice at many tumor treatment centers in and beyond China., It is developing at a rapid speed with continuously expanding application, and its curative effect is recognized by clinicians. Because of its high thermal efficiency, MWA has become a minimally invasive treatment for cancer. Thus, it is often used for nonsurgical treatment of patients and palliative treatment of solid tumors and is characterized by its accurate curative effect, convenient operation, small trauma, high safety, fast recovery, and limited influence by the individual factors of patients. It is suitable for treating local tumors and palliative treatment of nonsurgical patients with limited numbers of solid lesions of a suitable size. MRI-guided MWA treatment causes less trauma than CT-guided MWA treatment and can be performed repeatedly and monitored in real-time while achieving a detectable effect.
This work was supported by Jiangsu Commission of Health (grant number: BJ18034) and Science and Technology Department of Jiangsu Province (grant number: BE2017758).
Financial support and sponsorship
This work was supported by Jiangsu Commission of Health (grant number: BJ18034) and Science and Technology Department of Jiangsu Province (grant number: BE2017758).
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]