Laser-guided percutaneous microwave ablation for lung nodules: a promising approach with reduced operation time

Abstract

Background

Pulmonary nodule ablation is an effective method for treating pulmonary nodules. This study is based on the traditional CT-guided percutaneous microwave ablation (MWA) of pulmonary nodules. By comparing laser guidance technology with freehand method, this study aims to explore the safety and efficacy and patients’ pain scores of these two approaches.

Methods

This study retrospectively analyzed 126 patients who underwent CT-guided percutaneous lung ablation at the First Affiliated Hospital of Soochow University from April 2020 to April 2024. Based on the guidance method, we divided those patients into the laser guidance group and the freehand group. The primary outcome such as operation time, the number of ablation needle adjustments, postoperative pain scores, postoperative hospital stay, and postoperative complications were analyzed.

Results

The laser guidance group had a significantly shorter mean operation time compared to the freehand group (39.3 ± 13.65 min vs. 43.82 ± 19.12 min, p < 0.01), and in the laser guidance group, fewer ablation needle adjustments were required than in the freehand group (3.3 ± 1.34 time vs. 4.37 ± 1.39 times, p < 0.001). As compared to the freehand group, the laser guidance group had fewer cases of mild pneumothorax (13.16% vs. 38.33%, p < 0.05). The postoperative pain score at 1 h and 1 day of the two groups showed no statistical difference.

Conclusion

Both methods are safe and effective. The laser guidance technology significantly reduces the number of puncture adjustments and the operation time compared to the freehand method. Laser guidance technology effectively reduces the incidence of mild pneumothorax.

Background

As one of the most prevalent malignant tumors in the world, lung cancer is one of the deadliest diseases [1]. Metastases from malignancies of other systems also frequently appear in the lung [2, 3]. Both primary and secondary lung tumors manifest as pulmonary nodules on CT imaging. Video-assisted thoracoscopic surgery is only suitable for patients with good cardiopulmonary function who can tolerate general anesthesia [4]. However, for nodules near the central region, ensuring safe and effective margins typically requires the removal of a substantial amount of lung tissue, which is unacceptable for patients with poor lung function. Additionally, for patients with poor cardiac function, coagulation disorders, or other conditions that render them unfit for surgery, ablation is a better option [5].

Ablation is a widely proven safe and effective surgical method for treating pulmonary nodules [6,7,8]. Traditional ablation techniques include percutaneous microwave ablation (MWA), radiofrequency ablation, and cryoablation of lung nodules [9, 10]. Recently, bronchoscopic ablation methods have also been shown to be safe [11]. However, there are still challenges to be addressed, such as how to ablate pulmonary nodules with less adjustment times of ablation needle, and how to minimize patient discomfort during and after the ablation procedure.

Numerical Rating Scale (NRS) for assessment of pain intensity (PI) is a widely used method in clinical practice for assessing pain perception [12]. It is simple and quick. Laser guidance technology is a newer auxiliary technique applied in clinical practice. In some CT-guided procedures, laser guidance technology has been shown to effectively shorten operation time and increase precision [13,14,15].

This study is based on traditional CT-guided percutaneous MWA of pulmonary nodules. By comparing laser-guided technology with traditional manual puncture methods, we aim to compare the safety, efficacy and pain scores of these two methods.

Methods

Study population

This study is a retrospective study that has received approval from the Ethics Committee of the First Affiliated Hospital of Soochow University, with the ethics approval number 2,023,510. A total of 126 patients who underwent CT-guided percutaneous pulmonary nodules ablation at the First Affiliated Hospital of Soochow University from April 2020 to April 2024 were included in this study. The patients were divided into two groups based on whether laser-guided technology was used during the ablation procedure: the laser guidance group (43 patients) and the freehand group (83 patients). (Fig. 1)

The inclusion criteria for this study are as follows: patients with indeterminate lung lesions who cannot tolerate surgery or strongly refuse lung resection surgery and require local treatment. Additionally, included patients must have normal coagulation function, no pregnancy, no pneumothorax or pleural effusion, and no contraindications to puncture.

Fig. 1

Included: 126 patients who underwent CT-guided percutaneous pulmonary nodules ablation at the First Affiliated Hospital of Soochow University from April 2020 to April 2024. Excluded: patients with poor coagulation function, pregnancy, or other contraindications to puncture; patients experiencing severe pulmonary hemorrhage, progressive hemothorax, or ablation needle breakage during the ablation process that necessitated emergency surgery; patients unable to communicate and cooperate normally during the procedure; patients with other severe somatic diseases; and patients with an expected survival of less than three months after the ablation

The exclusion criteria are as follows: patients with poor coagulation function, pregnancy, or other contraindications to puncture; patients experiencing severe pulmonary hemorrhage, progressive hemothorax, or ablation needle breakage during the ablation process that necessitated emergency surgery; patients unable to communicate and cooperate normally during the procedure; patients with other severe somatic diseases; and patients with an expected survival of less than three months after the ablation. (Fig. 1)

Ablation procedure

Prior to ablation, patients undergo a comprehensive examination to ensure normal coagulation function, cardiac and pulmonary capacity tolerable for the procedure. A CT scan of the lungs is performed to rule out pneumothorax or pleural effusion. Based on the CT images, a detailed ablation plan is formulated, which should be thoroughly discussed and approved by both experienced clinicians and radiologists with expertise in ablation. The clinician must comprehensively communicate the surgical plan and associated risks with the patients and their legal guardians, and obtain informed consent from both parties before proceeding.

Once the patient is positioned in the CT suite, they are arranged in a posture that is conducive to the operation and sustainable for an extended period. A CT scan is then conducted, and a precise puncture pathway is devised using real-time CT imaging. The exact entry point for the puncture is marked, disinfected, and covered with a sterile drape. Local infiltration anesthesia with lidocaine is administered at the puncture site. Guided by pre-measured puncture direction and depth, the ablation needle is advanced, with multiple scans performed prior to reaching the target location to promptly adjust the trajectory as needed, until ablation commences. (Fig. 2)

Fig. 2

A. MWA console. B. ablation needle. C. ablation procedure, the point laser provided the path of puncture

After the ablation needle reaches the tumor, connect the ablation machine and perform ablation according to the set power and time. During the process, pay attention to whether the patient has any discomfort. Conduct a CT scan during the ablation to monitor the ablation effect and whether any complications occur. Successful ablation is achieved when the ablation area exceeds the tumor margin by 5–10 mm as is shown in Fig. 3.

After the ablation is completed, the ablation needle is withdrawn, and the puncture site is locally compressed and dressed. A subsequent CT scan is performed to confirm the absence of postoperative complications such as pneumothorax and pleural effusion as is shown in Fig. 3.

Fig. 3

The CT images of patients before and after ablation, A and B were the images of a same patient and C and D were the same

Working principle of SimpliCT

The laser machine (Fig. 4) includes two laser emission devices: a line laser for calibration and a point laser for guidance. In the operation panel as is shown in Fig. 4(A), the gray knob located in the center serves to adjust the emission angle of the point laser. The specific numerical value of this angle is displayed above the gray knob. The button positioned below the gray knob functions to lock or unlock the adjustment capability of the gray knob. The buttons located at the bottom of the control dial serve the following purposes respectively: align, reset, standby, and power on/off. Before starting the procedure, the patient’s position and the approximate location of the laser machine are determined by referring to preoperative imaging. The laser machine is moved to the appropriate position, and the line laser along with the default laser guide lines of the CT machine are turned on. The CT machine’s default guide lines include those parallel and perpendicular to the long axis of the table. The positions of the line laser and the laser machine are adjusted so that the line laser coincides with or runs parallel to the CT machine’s laser guide lines. Once aligned, the base of the laser machine is fixed in place, completing the calibration. At this point, the movement plane of the point laser emitter is parallel to the cross-sectional plane shown in the CT images as is shown in Fig. 4.

After determining the entry point and puncture path on the body surface based on the CT image, the angle between the puncture path and the vertical line is measured; this angle is the emission angle of the point laser as is shown in Fig. 3. Following standard sterilization and draping, the horizontal position of the CT table and the position of the point laser emitter are adjusted so that as the laser pointer approaches, it aligns itself with the entry point on the body. A guideline laser path now represents the intended puncture path. After completing the procedure, all laser emitters are turned off.

Fig. 4

A The SimpliCT device. B the line laser is used to align. C the point laser provides a laser in a measured angle to guide a precise puncture path

The lasers provided by SimpliCT including a point laser and a line laser, are Class 2 lasers (IEC 60825-1:2014). The laser beam should not be staring at straight for safety. Additionally, the SimpliCT is in accordance with the Medical Device Directive (93/42/EEC). Doctors need no protective equipment during the ablation.

Statistical analysis

Software spss26.0 was used for statistical analysis. Numerical variables were presented as means and standard deviations, whereas categorical variables were presented as percentages. Comparisons of numerical variables between the laser guidance group and the freehand groups were analyzed using Student’s t-test and Mann-Whitney U test. The comparisons of categorical variables were compared using the Chi-square test or Fisher’s exact test. P values less than 0.05 were considered statistically significant.

Results

In the laser guidance group, 43 patients were included, including 25 men and 18 women. The mean age was 61.4 years with a standard deviation of 12.6 years, ranging from 23 to 84 years. There was an average CT nodule size of 13.86 ± 8.15 mm (range: 6–40 mm). Among the 83 patients in the freehand group, 42 were males and 41 were females. The mean age was 59.9 years with a standard deviation of 12.9 years, spanning from 14 to 86 years. The typical size of CT-detected nodules measured 12.04 ± 6.01 mm, with a range of 6 to 37 mm. The previously noted factors showed no significant differences between the two groups.

9 patients (20.93%) in the laser guidance group were localized in the right upper lobe, 1 patient (2.33%) in the middle lobe, 6 patients (13.95%) in the right lower lobe, 18 patients (41.86%) in the left upper lobe, and 9 patients (20.93%) in the left lower lobe. There were 24 patients (28.92%) in the freehand group who had localization in the right upper lobe, 5 (6.02%) in the right middle lobe, 21 (25.30%) in the right lower lobe, 18 (21.69%) in the left upper lobe, and 15 (18.07%) in the left lower lobe. The two groups did not differ statistically (p = 0.118).

The average depth of the nodules from the pleura in the laser guidance group was 12.79 ± 10.35 mm (range: 0–34 mm) and in the freehand group was 13.17 ± 9.99 mm (range: 0–55 mm). The two groups did not differ statistically (p = 0.689). The laser guidance group includes 6 central nodules (13.95%) and 37 peripheral nodules (86.05%). The freehand group includes 8 central nodules (9.64%) and 75 peripheral nodules (90.36%). The two groups did not differ statistically (p = 0.465). Moreover, in the laser guidance group, 8 patients (18.60%) were positioned in the lateral position, 25 patients (58.14%) were positioned in the supine position and 10 patients (23.26%) were positioned in the prone position. In the freehand group, 19 patients (22.89%) were positioned in the lateral position, 34 patients (40.96%) were positioned in the supine position and 30 patients (36.14%) were positioned in the prone position. The two groups did not differ statistically (p = 0.173).

The laser guidance group includes 17 patients (39.53%) with a history of lung surgery, 20 patients (46.51%) with malignant tumors, and 2 patients (4.65%) with chronic obstructive pulmonary disease (COPD). As for the freehand group, 38 patients (45.78%) had a lung surgery, 41 patients (49.40%) had a malignant tumor, and 2 patients (2.41%) had COPD. The two groups of data showed no statistically significant difference.

Among 28 patients treated with laser guidance technology, 28 show the appearance of solid nodule (SN) in CT images, 4 show mixed glass ground nodule (mGGN), and 11 show pure glass ground nodule (pGGN). The pulmonary nodules of 47 patients in the freehand group appeared as SN in CT images, 14 patients as mGGN, and 22 patients as pGGN. The two groups did not differ statistically (p = 0.475) (Table 1).

Table 1 Comparison of variables of the two groups before ablation

Before the ablation, the average adjustment times of puncture needle of laser guidance group was 3.30 ± 1.34 times and that of freehand group was 4.37 ± 1.39 times. The two groups differed statistically (p < 0.001). Moreover, the overall ablation duration in the laser guidance group was 39.30 ± 13.65 min and the average ablation duration in the freehand group was 43.82 ± 19.12 min. The two groups differed statistically (p = 0.009). The average postoperative hospital stay in the laser guidance group was 1.28 ± 0.73 days and in the freehand group was 2.00 ± 3.05 days. The difference between the two groups is not statistically significant (p = 0.062). Additionally, the NRS points were assessed. One hour after the ablation, 42 patients (97.67%) felt chest pain in the laser guidance group, the pain of 36 patients (83.72%) was mild and 6 patients (13.95%) was moderate. In the freehand group, the chest pain of 66 patients (79.52%) was mild and 13 patients (15.66%) was moderate and 4 patients (4.82%) was severe. In the two groups, no statistically significant difference exists (p = 0.249). Additionally, one day after the ablation, 5 patients (11.63%) in the laser guidance group and 16 patients (19.28%) in the freehand group experienced chest pain (p = 0.482).

After the ablation procedure, we performed another scan and the images showed 5 patients (11.63%) had mild pneumothorax (lung compression ≤ 20%) in the laser guidance group and 23 patients (27.71%) in the freehand group. Statistics show that the two groups differ statistically (p = 0.04). CT scans in the laser guidance group showed that 1 patient (2.33%) experienced moderate pneumothorax (lung compression > 20%) and 3 patients (3.61%) in the freehand group (p = 0.696). Meanwhile, the CT scans in the laser guidance group showed no severe pneumothorax (lung compression > 50%) but the CT images of 2 cases (2.41%) in the freehand group showed severe pneumothorax (p = 0.305). In the laser guidance group, 1 patient (2.33%) was inserted chest tube and 5 patients (11.63%) accepted chest tube insertion for drainage (p = 0.355). The laser guidance group had two patients (4.65%) and the freehand group had fourteen patients (16.87%) with pleural effusion (p = 0.051). The freehand group and laser guidance group both had 8 patients (18.60%) with pulmonary hemorrhage, indicating there was no statistical difference (p = 0.152). No severe infection or severe cough or bronchopleural fistula was reported in either group of patients (Table 2)

Table 2 Comparison of variables of the two groups during and after ablation

Discussion

In our study, we found that both laser-guided MWA and traditional MWA of the pulmonary nodules are safe and effective. The laser guidance technology has a better performance concerning the incidence of minor pneumothorax, ablation duration and adjustment times of ablation needle.

The incidence of minor pneumothorax was lower in the laser guidance group compared to the freehand group. However, there was no statistically significant difference in the incidence of other complications such as moderate to severe pneumothorax, pleural effusion, pulmonary hemorrhage, and pulmonary infection. This might be because the energy sources of both groups were the same.

During the ablation procedure, the laser guidance group performed better in the following aspects. The laser guidance group had a significantly reduced number of adjustments required for the puncture needle to reach the tumor and a shorter overall operation time as well compared to the freehand method. This advantage is primarily due to the laser-guided technology providing a clear puncture path, whereas traditional puncture techniques rely on multiple adjustments to ensure accuracy. According to the findings of an in vitro experiment, the combined use of laser-guided technology with auxiliary aiming devices can significantly enhance the accuracy of puncture procedures [13]. Currently, this technology is predominantly applied in orthopedic surgeries. Some studies have indicated that laser-guided technology can substantially reduce the radiation time required for C-Arm Cone-Beam CT-guided biopsy [14]. Furthermore, another study suggests that in the ablation surgery of osteoid osteoma, laser-guided technology is also effective in minimizing fluoroscopy time [15]. Our previous research also suggests that by using laser guidance technology, CT scan times and localization duration may be reduced when it comes to preoperatively localizing pulmonary nodules [16]. The shortened radiation time is beneficial for both doctors and patients, as it minimizes the exposure to radiation-induced harm. Our research has reached similar conclusions, demonstrating that laser-guided technology can shorten the operation time and reduce the number of needle adjustments required. This translates to a significant reduction in both radiation exposure and trauma caused by frequent punctures for patients.

Additionally, there was no significant difference in pain scores between the two groups one hour and one day after the procedure. Although in the laser guidance group, patients went through fewer puncture adjustment times, the pain feelings of patients did not vary between the two groups. This might be because the pain feelings mainly were generated by the puncture, the adjustment of the ablation needle happens in the lung parenchyma, as a result, the adjustment time was probably not an important factor.

With the advancement of technology, numerous novel techniques have emerged. The development of lung tissue ablation surgery via bronchoscopy has progressed from in vitro experiments to clinical applications [17]. Studies have indicated that both percutaneous lung ablation and bronchoscopic ablation are safe and effective [18]. These studies have also outlined the appropriate scopes of application for percutaneous lung ablation and bronchoscopic lung ablation, providing the most suitable options for ablating lung nodules in different locations. Furthermore, research by Chen et al. [19] has pointed out that the use of photodynamic therapy combined with bronchoscopic navigation technology in hybrid operating rooms can effectively treat peripheral lung tumors. Additionally, Chang et al. [20]’s research focuses on lung ablation surgery within hybrid operating rooms. Their study suggests that thermal ablation surgery for lung tumors under general anesthesia in hybrid operating rooms is a safe and effective treatment method.

All ablation procedures were performed by experienced clinicians, assisted by skilled radiological technicians. The decision on whether to use a laser guidance device was randomized by the operating surgeon. All surgical processes were conducted according to established protocols. However, minor differences in operational habits among different operators may lead to biases in the conclusions of this study. In the future, we may conduct prospective studies with precise control over the operators and other variables to ensure that the conclusions are more convincing. The scale of this study is also relatively small. Thus, multicenter, large-scale studies can be conducted in the future to further validate the findings of this research.

Due to the limited follow-up period of the study population, our research lacks long-term postoperative follow-up data. Therefore, the long-term ablation outcomes of the two ablation methods remain unknown. Currently, the technique of performing a lung tumor biopsy simultaneously with percutaneous ablation is quite advanced. Wang et al. presented that simultaneous lung biopsy and nodule ablation are safer and have fewer complications and similar effects compared to performing them sequentially [21]. Hu et al. indicated that non-coaxial biopsy and ablation have fewer complications than coaxial biopsy and ablation and CT-guided needle biopsy combined with MWA is safe and effective for the treatment of suspected malignant pulmonary nodules [22]. Therefore, whether laser guidance technology can benefit the simultaneous biopsy and ablation procedure still requires further investigation.

Laser guidance technology has significant advantages. In the future, laser guidance technology need be explored to see if it can offer benefits to additional medical treatment processes.

Conclusion

Both methods are all safe and effective. The laser guidance technology significantly reduces the number of puncture adjustments and the operation time compared to the freehand method. Laser guidance technology effectively reduces the incidence of mild pneumothorax, while there are no significant differences between the two groups regarding pain score and other complications. The limitation of this study is the lack of comparison of long-term postoperative follow-ups. The sample size of this study is relatively small as well, necessitating larger sample sizes and multi-center studies.