Localization techniques for small pulmonary nodules: a narrative review of current strategies and future perspectives

Introduction

With the widespread use of lung cancer screening using high-resolution imaging and low-dose computed tomography (CT), the number of small pulmonary nodules detected has increased, and the management of such lesions has become increasingly important (1). Early detection of pulmonary nodules, especially in non-small cell lung cancer (NSCLC), significantly improves prognosis (2). Recent large-scale clinical studies have demonstrated that sublobar resection is non-inferior to lobectomy for small peripheral lesions (3,4). However, these lesions are often ground-glass nodules (GGNs) or small nodules, and when located relatively deep in the lung parenchyma, they are often nonpalpable, making intraoperative identification difficult.

Video-assisted thoracic surgery (VATS) has become the standard approach for the diagnosis and treatment of small pulmonary nodules. In recent years, minimally invasive VATS approaches and robot-assisted surgery, which reduce the size of the thoracic incision and the number of ports, have also been applied to NSCLC surgery. These procedures are rapidly becoming more common due to the advantages of reduced postoperative pain and shorter hospital stays resulting from their minimal invasiveness (5,6). However, as surgery evolves towards a minimally invasive approach with smaller incisions, the tactile feedback on which surgeons traditionally rely is diminishing. The success of VATS wedge resections and segmentectomies for lesions close to the intersegmental line is highly dependent on accurate localization of the target nodules. This requirement has led to the development of a variety of localization strategies, each with its own advantages and disadvantages.

Traditional localization methods, such as CT-guided hook wire localization and dye or lipiodol injection, have been widely adopted due to their accessibility and relative simplicity. However, these methods are associated with risks such as pneumothorax, pulmonary hemorrhage, and air embolism, as well as marker displacement (7). In recent years, bronchoscopic localization techniques such as virtual-assisted lung mapping (VAL-MAP) and electromagnetic navigation bronchoscopy (ENB) have emerged, providing less invasive and safer alternatives (8,9).

At the same time, technological advances have made it possible to integrate intraoperative imaging into the surgical workflow. In a hybrid operating room (OR) equipped with cone-beam computed tomography (CBCT), combined with three-dimensional (3D) image analysis and surgical planning software, real-time 3D images can now be obtained during surgery. This allows the location of the lesion and the resection plan to be confirmed immediately in the OR without the need for special localizing procedures before surgery. In addition, we have used a method to virtually simulate the lung resection line and optimize the surgical margin using 3D images obtained from CBCT during surgery (10).

This review aims to provide a comprehensive and detailed analysis of various localization methods for small pulmonary nodules, integrating conventional, bronchoscopic, and intraoperative CBCT-guided techniques, and to offer thoracic surgeons practical guidance for selecting the optimal approach. Compared with prior reviews focused on preoperative CT-guided or bronchoscopic localization (11,12) and on decision frameworks for technique selection (13), our narrative review integrates hybrid-OR/CBCT-based intraoperative resection-line simulation (“mapping beyond localization”) and newer wireless/magnetic modalities [e.g., radiofrequency identification (RFID), magnetic-guided occult lesion localization (M-GOLL)] into a surgeon-oriented comparison table and flowchart. By building on these earlier frameworks and emphasizing margin assurance, we aim to provide a practical, up-to-date guide for contemporary thoracic surgery.

By providing these detailed overviews, we hope to assist thoracic surgeons in choosing the most appropriate localization method according to their patients' and their institution’s needs. We present this article in accordance with the Narrative Review reporting checklist (available at https://vats.amegroups.com/article/view/10.21037/vats-25-40/rc).

Methods

A comprehensive search of PubMed and Google Scholar was performed by two authors (M.A. and S.M.) on June 30, 2025. The search covered studies published from January 1, 2000 to June 30, 2025. Search terms included: “lung nodule”, “localization”, “VATS”, “thoracoscopic resection”, “cone-beam CT”, “hybrid OR”, “bronchoscopic marking”, “VAL-MAP”, “ENB”, “radioisotope”, “indocyanine green”, “near-infrared”, “RFID”, and “M-GOLL”.

Inclusion criteria: English-language original articles, clinical studies (prospective/retrospective), and systematic/narrative reviews that reported methods for localization or intraoperative identification of small pulmonary nodules.

Exclusion criteria: non-English publications, animal/phantom studies, conference abstracts only, and small exploratory studies.

Titles/abstracts were screened independently by M.A. and S.M.; disagreements were resolved by consensus with K.U. The detailed search strategy is summarized in Table 1.

Furthermore, we present our CBCT-guided localization and lung resection line simulation in a hybrid OR using 3D image analysis and surgical planning software, SYNAPSE VINCENT (Fujifilm Corporation, Tokyo, Japan), which is an innovative and highly accurate method for small pulmonary nodule resection (10).

Traditional CT-guided localization techniques

CT-guided localization remains one of the most widely used localization techniques due to its simplicity and wide availability. These techniques include hook wire, microcoil, anchored needle placement, dye, lipiodol, medical glue, and radioisotope injection. Each technique has its own procedural considerations, advantages, and limitations. It is also important to note that CT-guided localization is associated with a higher incidence of pneumothorax and pulmonary hemorrhage than other localization techniques. To the best of our knowledge, there have been no published reports of air embolism associated with CT-guided localization methods other than hook wire. However, because all percutaneous CT-guided localization techniques involve puncturing the lung parenchyma, air embolism is theoretically possible and should be kept in mind.

Hook wire

Hook wire localization is one of the oldest and most widely used localization techniques. Under CT guidance, a barbed wire is percutaneously placed near the target nodule. The external portion of the wire is fixed outside the body and serves as a physical guide during surgery. The success rate of this method is reported to be 93% to 100%, depending on the size and depth of the lesion (14-18). One major drawback is that the wire may become dislodged during patient positioning or transportation. Recently, it has been reported that hybrid OR equipped with CBCT can help overcome some of the drawbacks of localization using hook wires, such as wire dislodgement during patient transport. This is because it allows for localization and verification within the same room before resection (19). Relatively common complications include pneumothorax and pulmonary parenchymal hemorrhage. Guo et al. performed a robot-assisted localization method and reported a significant decrease in the incidence of pneumothorax compared to conventional manual localization (20). Rare complications have been reported, including hemothorax and air embolism. Air embolism in particular is a serious complication that can lead to cerebral embolism and ischemic heart disease, and has been reported to result in death (21-23).

Microcoil

Platinum microcoils are placed under CT guidance from within the lung directly under the visceral pleura on the surface of the lung, resulting in a dumbbell-shaped deployment. This shape makes them less likely to be dislodged and provides stable localization, allowing for a longer period between localization and surgery. However, because they are placed within the lung, visibility during surgery is sometimes reduced (24). In addition, the procedure is slightly more complicated than the hook wire method, so it requires the operator to be highly skilled. One advantage of microcoils is that they can be placed in areas that are difficult to reach with the hook wire method. Zuo et al. reported that they were able to place microcoils in 16 GGNs located in the “blind areas” of the hook wire method, including the mediastinum-adjacent region, interlobar fissure-adjacent areas, and scapula-shadowed areas, without any major complications (25). Sun et al. compared 184 microcoil-localized lesions with 157 hook wire-localized lesions and reported a higher success rate with microcoils than with hook wire (99% vs. 93%, respectively) and a significantly lower incidence of pneumothorax (26).

Anchored needle

This localization method involves placing a needle with multiple small “claws” or “hooks” at the tip near the lesion under CT guidance. Compared with microcoils, this method is simpler. In addition, because it is placed on the visceral pleural surface, it is easily visible from the lung surface during surgery. In a retrospective analysis of 395 GGNs localized using this method, the success rate of localization was 99%, and all lesions were resected by VATS (27). In a report comparing localization with hook wires and anchored needles, the success rate of lesion location was similar, with the anchored needle at 99.1%. In addition, the anchored needle had a significantly lower displacement rate than the hook wire (28). In another report comparing localizing with microcoil and anchored needle, the anchored needle showed a significantly shorter procedure time and a significantly higher localization success rate of 99.1%. The frequency of complications was similar (29). The disadvantage of this method is post-procedural pain. Qin et al. reported that approximately half of patients experienced moderate to severe pain after CT-guided needle placement (30).

Dye

The most common dyes used in lesion localization are methylene blue and patent blue V. These dyes are directly injected near the nodule under CT guidance. They can also be used for bronchoscopic localization. The use of these dyes allows visual identification of lesions during VATS. This method is cost-effective and technically simple. The difference between the two dyes is that patent blue V is brighter and more vivid than methylene blue, making it more visible even in lungs with severe anthracosis, and it tends to remain localized. However, it should be noted that patent blue V is more expensive than methylene blue and has a higher incidence of allergies (31). Methylene blue should be used with caution due to the risk of genotoxicity (32). In a report using methylene blue, the procedure was relatively simple, took only 7.6 minutes on average, and had a high success rate of 98.8% (33). In another report using patent blue V, the localization success rate was good at 99.5% with few complications (34). However, rapid diffusion of dyes through the alveolar space may reduce the accuracy of identifying the lesion site, especially for deep-seated nodules (35). In response to this issue, attempts have been made to localize the lesion by combining dyes with other medical agents. Aoun et al. reported that mixing methylene blue with collagen improved visibility and resection rates (36). Hasegawa et al. also reported the usefulness of a mixture of dye and radiopaque material, and showed that the use of a high-viscosity contrast agent in the mixture reduced diffusion in the lung parenchyma (37). In addition to methylene blue and patent blue V, indocyanine green (ICG) can also be used as a dye for CT-guided localization. This method enables intraoperative identification of small nodules under near-infrared imaging and has been reported to achieve high localization success rates (38). Details of ICG use in fluorescence-guided surgery are described in Section “ICG/near-infrared (NIR) fluorescence imaging”.

Lipiodol

Lipiodol, an iodized poppy seed oil, is radiopaque and can be identified by intraoperative fluoroscopy (39). Lipiodol is highly viscous and remains in the lung parenchyma for a long time, so surgery does not need to be performed immediately after localization, improving flexibility in surgical schedules. Watanabe et al. reported that they localized 174 pulmonary nodules with lipiodol 1–7 days before surgery and were able to identify their location intraoperatively in all patients (40). However, as with other CT-guided localization methods, there is a risk of pneumothorax and pulmonary hemorrhage. In a multicenter study conducted in Japan, pneumothorax occurred in 495 of 867 patients (57.1%), of whom 59 patients (6.8%) required thoracic drainage (41). In addition, a report investigating the effect of intrapulmonary diffusion of lipiodol on intraoperative visibility showed that patients with widespread diffusion were associated with increased operative time and bleeding (42). Regarding this issue, Fumimoto et al. reported the benefits of lipiodol localization in a hybrid OR equipped with CBCT and performing lung resection in a single procedure (43). Lipiodol is lipid-soluble and therefore poorly soluble in water, so there is a possibility of embolism if it migrates into blood vessels. Although fatal embolic events directly related to pulmonary nodule localization have not been reported, several cases of cerebral and systemic lipiodol embolism have been described in other procedures, raising safety concerns. Therefore, the use of lipiodol for pulmonary nodule localization has become limited to selected institutions in recent years (44,45).

Medical glue

The main component is n-butyl cyanoacrylate, which reacts with anions in the lung parenchyma after injection and instantly hardens to form an elastic thin film. This thin film seals the puncture hole, adheres to the lung parenchyma, and forms a scar that is visible during surgery. In a retrospective study comparing hook wire and medical glue in 158 patients, the localization rate with medical glue was 100%, and the incidence of pneumothorax and pulmonary hemorrhage was significantly lower with medical glue than with hook wire (46). Furthermore, a prospective randomized trial verifying the non-inferiority of medical glue to hook wire showed that in addition to the non-inferiority of medical glue, the incidence of pneumothorax and pulmonary hemorrhage and pain scores were significantly lower with medical glue than with hook wire (47).

Radioisotope

The radioactivity of a nuclide injected near a pulmonary nodule before surgery can be detected in real time using a gamma probe during surgery. Tc-99m-macroaggregated human serum albumin is mainly used, which has a half-life of about 6 hours, allowing a time interval of about 24 hours before surgery. Another advantage of this method is that the tracer does not diffuse within the lungs. The use of radioisotopes in uniportal VATS has been reported, and high localization rates and low complication rates comparable to those of multiportal VATS have been reported (48,49). In addition, a study comparing radioisotopes with hook wires reported that radioisotopes tended to have a lower incidence of pneumothorax and a smaller volume of resected tissue than hook wires (50). This method requires specialized equipment such as radiation protection facilities, gamma probes, and scintigraphy devices, and strict management is required for the handling, storage, and disposal of radioisotopes. For this reason, the cooperation of staff with nuclear medicine expertise is essential, which poses a barrier to implementation in many facilities

M-GOLL

A wireless localization technique termed M-GOLL has recently been introduced for non-palpable pulmonary nodules. A magnetic seed (Magseed^®, Endomag, UK) is placed near the target under CT guidance, and intraoperative detection is achieved with a handheld magnetic probe (Sentimag^®). This approach avoids wires and liquid tracers, provides real-time proximity feedback without fluoroscopy, and may reduce the risks of marker displacement or parenchymal leakage. In an exploratory feasibility study of 12 patients, all lesions were successfully localized and resected, with pneumothorax occurring in the two cases that used two seeds (one required a short chest-tube drainage) (51). Wider adoption will depend on availability of dedicated magnetic equipment and further prospective data.

Bronchoscopic localization techniques

CT-guided localization is effective, but requires careful coordination between the radiology and surgical teams due to the risks associated with patient movement and the risk of pneumothorax and pulmonary hemorrhage caused by puncture of the lung parenchyma. Bronchoscopy-guided localization reduces these risks. Moreover, unlike CT-guided localization, bronchoscopic localization - particularly with ENB - can be performed immediately before surgery in the same operating session, minimizing patient burden (52).

VAL-MAP

VAL-MAP is a bronchoscopic contrast localization method developed to overcome the limitations of the percutaneous approach. Based on the patient’s CT images, a 3D virtual bronchoscopic image is constructed, and 2–4 bronchi are selected as localization points. A catheter with a metal tip is inserted into the selected bronchus, and after confirming the tip of the catheter under fluoroscopy, indigo carmine is injected to mark it. After localization, a CT scan is taken to confirm the position. Sato et al. reported a high resection rate of 99.3% for 156 lung lesions using this method (53). However, it has been reported that many lesions, especially upper lobe lesions, cannot be visualized during surgery (54). In response to this, a method has been devised in which a microcoil is placed simultaneously with the dye to enable intraoperative fluoroscopy observation (55).

ENB

ENB is a technique that uses electromagnetic tracking to guide the bronchoscope to the target lesion based on preoperative CT image data. After reaching the target lesion, various markers can be placed through the working channel. The type of marker placed via ENB varies, including dyes and microcoils, and RFID tags (refer to next section), and therefore the intraoperative detection method also differs accordingly. The success rate of localizing pulmonary lesions has been reported to be high at about 94%, and the complication rate of the procedure is low (56-58). Moreover, when ENB is performed in a hybrid OR equipped with CBCT, immediate intraoperative confirmation and re-targeting become possible, which can improve localization accuracy and streamline workflow (59). However, Cho et al. reported that the success rate of localizing lesions using this method was somewhat lower at 87.5%, and all failure cases were right lower lobe lesions (60). The disadvantages of ENB are that it is difficult to introduce it in all medical facilities because it requires specialized knowledge and experience to operate, proficiency takes time to achieve, and equipment is expensive to introduce and maintain.

RFID

An RFID tag (1.8 mm in diameter and 7 mm in length) is placed via bronchoscope, and communication is possible from a distance of 3 cm during surgery using a dedicated detection probe. This eliminates the need for intraoperative confirmation using fluoroscopy or CT (61). A multicenter study conducted in Japan retrospectively analyzed 182 patients who underwent resection with RFID, and reported that the lesion was resected as planned in all patients, with no complications (62). However, there have been reports of cases in which the tag was placed far from the lesion even when using ENB or fluoroscopy, and cases in which the position of the RFID tag shifted in position due to coughing after placement in a large bronchus (63). In addition, advanced equipment such as a dedicated detection probe is required, but only a limited number of facilities possess this equipment, and the introduction of such equipment is expensive, so there are challenges to its popularization.

ICG/near-infrared (NIR) fluorescence imaging

When excited by NIR light, ICG emits longer wavelengths of NIR light. Using a fluorescence imaging device, it is possible to identify lesions that are difficult to see or that are located deeper inside the lung. ICG has been administered by injection into the lung parenchyma under CT guidance, intrabronchial administration using a bronchoscope, and intravenous administration. In a meta-analysis comparing these methods with 1,776 registered patients, the localization rate of the intrabronchial administration method was particularly excellent at 98.3% (64). In addition, a method combining VAL-MAP and ENB has also been performed, and both have been reported to have good localization rates (65,66). In addition, attempts have been made to administer ICG by combining Robotic Assisted-Bronchoscopy and CBCT, and it has been reported that this method is characterized by excellent operability and accurate navigation, especially compared to the ENB method (67). Moreover, a novel approach using a fiducial microcoil saturated with ICG has been reported to maintain fluorescence for a longer period and facilitate delayed surgical resection. This technique combines the radiographic visibility of the coil with the fluorescence properties of ICG, thereby allowing accurate localization even several days after placement (68).

Intraoperative image marking

Unlike the localization methods mentioned so far, the only preoperative examination required is a plain CT scan, and no additional procedures are needed. Another advantage is that damage to the lung surface caused by localizing can be addressed immediately. Identification of lung lesions using CBCT in hybrid ORs is steadily becoming more common.

Intraoperative ultrasonography (US)

US has long been used to detect small lung nodules, and its advantages are that it is minimally invasive, does not involve radiation exposure, and allow real-time observation. One study reported that the detection rate of lung lesions using US during VATS was 76–100% (69). Kondo et al. demonstrated that nonpalpable GGNs can be detected by US in completely collapsed lungs (70). Schauer et al. also used various US tools to observe 18 lesions immediately before resection. All lesions were detectable by B-mode, and tumor angiogenesis was observed in all lesions by power Doppler. Furthermore, contrast-enhanced US using sulfur hexafluoride showed early peripheral wash-in and central contrast enhancement almost simultaneously, findings that closely reflected the pathological results without the need for additional modalities (71). Thus, intraoperative US can be used not only to identify lesions, but also as an intraoperative diagnostic aid. However, the detection of pulmonary nodules, which have low specificity as imaging findings, depends heavily on operator skill, and considerable training is required to become proficient in this technique. On the other hand, several studies have reported that GGNs, especially those smaller than 10 mm or located deeper in the lung parenchyma, may be difficult to detect using intraoperative US. For instance, one series failed to localize a GGN measuring 10 mm located 10 mm below the visceral pleura using both US and palpation. Thus, while US is generally effective for superficial and solid nodules, caution is warranted for small or deep-seated GGNs (72).

CBCT marking in the hybrid OR

CBCT can be performed in the hybrid OR, and marking and positioning are guided based on the obtained images. In most reports, the CBCT system is permanently installed in the hybrid OR, and a metal ligating clip is used as the marker. The procedure is relatively straightforward, and a high resection success rate has been reported (73-75). Furthermore, since marking and lung resection can be completed in the OR, no additional procedures are required before surgery. This is also a major advantage of this method, as it reduces the burden on patients and medical staff. On the other hand, hybrid ORs require large-scale infrastructure, including dedicated space, CBCT-compatible equipment, and trained personnel. The initial installation costs and ongoing maintenance can be substantial. In addition, CBCT raises concerns about radiation exposure for both patients and medical staff compared with fluoroscopy. In previous reports, CBCT was usually performed more than twice during surgery (73-75). According to a study using a phantom by Mitsuoka et al., the radiation dose of CBCT is estimated to be 0.58 times that of conventional helical CT (74). Furthermore, several clinical studies have reported that CBCT-guided localization in the hybrid OR results in lower total radiation exposure than conventional CT-guided localization performed in the interventional radiology suite (19,76). Nevertheless, radiation exposure for OR staff must still be carefully managed with appropriate shielding and safety protocols.

Intraoperative simulation of lung resection line using 3D CBCT images

We introduced a method to simulate not only the lesion but also the planned resection line (approximated as a diamond or a hexagon) based on the 3D reconstruction of the preoperative CT, and reported the first 16 patients in 2022. Not only was the resection performed as planned in all patients, but determining the resection line preoperatively was also useful for planning the VATS port position (10). Since then, we have been improving and implementing this method since January 2023 based on our accumulated case experience. We have implemented a method in which CBCT is performed only once during surgery, and the obtained CBCT image is used to simulate a 3D model and adjust the marking of the planned resection line. Next, we briefly explain this method.

First, based on the CT data acquired before surgery, we use 3D image analysis and surgical planning software SYNAPSE VINCENT to visualize the lung lesion and simulate the resection line. The resection line is naturally determined by the stapler insertion direction, the distance from the pleural surface of the tumor, and the set margin length, as shown in Figure 1. After thoracotomy, ligating clips are placed at two or three locations near the tumor, based on landmarks such as the apex, pulmonary ridge, and trilobar junction, and CBCT scans are performed with the lung fully inflated. At our institution, CBCT scans are performed using an Artis zeego^® (Siemens Healthcare GmbH, Bayern, Germany) installed in a hybrid OR. Using the obtained CBCT data, 3D images are created using SYNAPSE VINCENT to simulate the location directly above the tumor (point A: apex point), the stapler entry point (point S: start point), the exit point (point G: goal point), and two intermediate points along the stapler trajectory (points W, W’: way points). Based on the initial CBCT scan, it is necessary to compensate for and account for the volume reduction of the lung in the collapsed state compared with when it is inflated. The positions of the two ligation clips (points C, C’: clipping points) placed before the CBCT scan and the marking points mentioned above are drawn on a film and projected onto the surface of the collapsed lung (Figure 2). At this time, marking is performed by cauterization with an electric scalpel, not by clips. This method makes it possible to determine the tumor location and stapler line with a single CBCT scan during surgery. This method has been performed in 64 patients, including the previously reported patients from May 2020, with a 100% tumor resection rate and favorable outcomes.

Figure 1 Overview of the CBCT-based simulation of the planned lung resection line. (A) Planned marking points derived from cone-beam CT. (B) Cross-sectional schematic showing planned way points and margin preservation. AT is the distance from the lung surface to the bottom of the tumor, and TB is the distance from the bottom of the tumor to the resection margin. The length of AW and AW' is equal to the length of AB. In other words, these lengths are determined by the margin to be secured from the bottom of the tumor. A, apex point; B, base point; C, C’, clipping points; CBCT, cone-beam computed tomography; G, goal point; S, start point; T, bottom of the tumor; W, W’, way points.

Figure 2 Intraoperative marking procedure based on cone-beam computed tomography. (A) Projection of the marking points derived from cone-beam computed tomography onto a film placed on the lung surface. (B) The marking points on the lung surface correspond to the intraoperative plan. (C) Schematic representation. A, apex point; B, base point; C, C’, clipping points; G, goal point; S, start point; W, W’, way points.

Although this intraoperative simulation technique has shown favorable results, several limitations should be noted. First, the method requires a hybrid OR equipped with a CBCT system and dedicated 3D reconstruction software, which restricts its application to specialized facilities. Second, variations in lung inflation and collapse may influence the geometric accuracy of the simulated resection line, and no standardized correction factor for deflation-related volume reduction has been established. Third, the procedure demands personnel experienced in CBCT acquisition and 3D image processing, which may lengthen the learning curve and procedural time. Finally, our current data are derived from a single-institution experience with a limited number of cases; therefore, further multicenter validation studies are warranted to confirm the generalizability and reproducibility of this method.

Future perspective

A detailed comparison of procedural characteristics, limitations, potential risks, and costs for each localization method is provided in Table 2. In Table 2, the “Risk of air embolism” column was categorized as “Yes” only for hook wire localization, where clinical cases have been documented, and as “Yes (theoretical)” for other CT-guided approaches. The term “theoretical” indicates a mechanistic possibility related to transpleural puncture, rather than a frequent or observed complication. This categorization aims to provide a balanced safety comparison across different localization techniques. The selection process for appropriate localization techniques according to lesion size, depth, and available resources is summarized in Figure 3. These will serve as a basis for discussing options in clinical practice and guiding future technological development. The future perspective is described below.

Figure 3 Flowchart illustrating the selection of localization techniques for small pulmonary nodules based on lesion size, depth from the pleural surface, and institutional resources. For superficial solid lesions larger than 10 mm, intraoperative US may be an option; however, the detection rate for GGNs located relatively deep is significantly lower, even when the lesion is ≥10 mm. Lesions located within approximately 20 mm from the pleural surface are generally suitable for CT-guided localization. Bronchoscopic localization can be considered for deep lesions or when percutaneous access is limited. In institutions equipped with a hybrid OR, intraoperative CBCT allows real-time 3D visualization and marking without preoperative localization. 3D, three-dimensional; CBCT, cone-beam computed tomography; CT, computed tomography; GGNs, ground-glass nodules; OR, operating room; US, ultrasonography.

Before discussing future directions, it should be noted that most of the existing studies on pulmonary nodule localization are retrospective and single-center in nature, with relatively small sample sizes and short follow-up periods. Furthermore, direct head-to-head comparisons among different localization techniques are still limited, and publication bias may favor positive outcomes. These factors should be taken into consideration when interpreting the current evidence, especially for emerging or rapidly evolving technologies such as hybrid OR-based CBCT-guided surgery and novel wireless or magnetic localization systems.

With the rapid development of engineering technology, mankind is getting new technologies and innovative tools every day. We surgeons have also benefited from this and have entered an era in which highly precise surgical instruments surpass conventional standards. CT equipment is no exception, and mobile CTs that are not fixed to the OR have been developed and are being used in clinical practice. Fujikawa et al. have reported intraoperative marking using a mobile CT scanner, the O-arm™ (Medtronic Japan Co. Ltd., Tokyo, Japan) (77). In the future, the development of more compact mobile CBCT systems may allow greater flexibility in surgical scheduling.

In addition, research is currently accelerating on the use of artificial intelligence (AI) in the detection of pulmonary nodules in clinical practice (78-80). In the near future, AI will also be applied to detect small pulmonary nodules during surgery. Furthermore, with the accumulation of cases, it will be possible to suggest the optimal resection line and port position for inserting an automatic stapler. The method practiced at our institution may provide important know-how for AI-based lung parenchymal resection line determination for reliable resection of pulmonary nodules. However, there are several challenges to integrating AI into surgical procedures. These include standardized datasets, regulatory approval, and robust validation of AI tools in various clinical settings. Ethical concerns regarding transparency of patient data and algorithms also need to be addressed.

Conclusions

In this review, we comprehensively outlined various localization methods for small pulmonary nodules, from traditional CT-guided techniques to bronchoscopic-assisted techniques and novel techniques using intraoperative imaging. Each technique has its own advantages and limitations. Therefore, the appropriate method should be selected according to the nature of the nodule, its anatomical location, and the resources and expertise of the institution.

The introduction of CBCT in hybrid ORs, which has gained increasing attention in recent years, is an innovative technology that can replace conventional localization. By utilizing dedicated software to obtain real-time 3D images during surgery, CBCT enables precise margin assessment and revision of resection plans. Looking ahead, integration with AI and robotics is expected to further enhance personalized surgical care.

In addition to prospective studies comparing the effectiveness of each technique, comprehensive evaluations, including resource utilization, safety, cost, and surgeon proficiency, are required. As technology advances, surgeons must continue to deepen their knowledge and maintain the flexibility to select the safest and most effective localization strategy for their patients.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://vats.amegroups.com/article/view/10.21037/vats-25-40/rc

Peer Review File: Available at https://vats.amegroups.com/article/view/10.21037/vats-25-40/prf

Funding: This research was partially supported by Research Support Project for Life Science and Drug Discovery [Basis for Supporting Innovative Drug Discovery and Life Science Research (BINDS)] from AMED (grant No. JP25ama121054).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://vats.amegroups.com/article/view/10.21037/vats-25-40/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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