Introduction

A hybrid operating room (HOR) is a high-technology space provided with imaging tools and equipped to allow minimally invasive and traditional surgical procedures. Originally developed for cardiac and vascular procedures, such as transcatheter aortic valve replacement (TAVR) and endovascular thoracic (TEVAR) or abdominal (EVAR) aortic repair, only in recent time, this particular type of surgical theatre has been used by thoracic surgeons also.

In 2015, Gill et al. [1] first described a new image-guided surgery workflow for intraoperative marker-guide video-assisted thoracoscopic surgery (VATS) wedge resection, in a HOR equipped with a C-arm cone-beam computed tomography (CBCT), to improve the precision of identifying and resecting non-palpable lung nodules and called this procedure image-guided video-assisted thoracoscopic surgery (iVATS). Since then, iVATS has gained increasing popularity, although still only a few groups of thoracic surgeons in the world have introduced this innovative surgical approach into their clinical practice.

iVATS includes the intraoperative percutaneous metallic marker placement in HOR, thus avoiding the potential complications associated with the traditional workflow performed in the radiology suite [1, 2]. Computed tomography (CT)-guided hookwire/coil localization, performed in the radiology suite, is the most commonly used localization method for non-palpable nodules [3]. However, metallic markers have the tendency to dislodge during patient transportation to the operating room with a significant risk of intra-parenchymal bleeding and pneumothorax. The onset of a tension pneumothorax in a chronic obstructive pulmonary disease (COPD) patient, with a reduced pulmonary function, during transportation may be a very serious condition.

The novelty of iVATS lies in the performance of nodule localization in real-time, in the same suite and proceeding immediately to resection in a HOR, thereby reducing the procedure-related complications and complexity of care [1, 2].

Lung nodules with a high probability of malignancy, not palpable through a VATS approach and with a high risk of conversion to thoracotomy, are ideal targets. The widespread availability of low-dose CT screening for lung cancer has increased the rate of detection of small lung nodules. Although the characterization of some of these nodules can be made using CT-guided percutaneous biopsy, the vast majority of them require an excisional lung biopsy using VATS. Some nodules, however, can be of difficult or impossible intraoperative VATS localization for specific characteristics of the lesions, such as size, density and depth from pleural surface, and of the lung parenchyma, when the lesion is located in a dystrophic area.

Procedural workflow

The procedural workflow of single-stage localization and removal of non-palpable lung nodules through iVATS is articulated into 6 steps [4] (Fig. 1).

Fig. 1
figure 1

The procedural workflow of single-stage localization and removal of non-palpable lung nodules through iVATS, articulated into 6 steps (see text)

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Patient placement

The anesthetized patient, with a double-lumen tube in place, is positioned in lateral decubitus position and draped for a VATS procedure. During the patient positioning, the target lesion is aligned to the table midline, to fall within the acquisition volume, because the field of view provided by the intraoperative CT is smaller than that of a standard multidetector CT. The arms are bent anteriorly, as close as possible to the face, with both elbows in line or cranial to the chin and within the table edge, whenever possible. The patient is fixed with elastic tape at the level of the pelvis and shoulders to allow tilting of the table. The vast majority of the hybrid rooms are equipped with angiographic non-breakable tables. For this reason, it may be necessary to insert a dome-shaped gel positioner under the patient’s chest, at the level of the xiphoid, to mimic table flexion and widen the intercostal spaces.

The patient position is accurately checked in order to avoid collision with the rotating C-arm of the robotized angiography that will acquire the CT images. The HOR is in fact equipped with a robotized angiography that allows the acquisition of multiplanar CT images of good quality (cone-beam CT). The patient placement is a critical step of the procedure and requires specific training for the surgeon, the anaesthetist and the operating room nurses. Hsieh et al. [5] reported that a collision between the rotating C-arm and the operating table occurs in up to 40% of the patients, although a reduction of the collision rate can be achieved after treating the initial 30 patients. The risk of collision is particularly evident for obese patients and those with a large thoracic cage.

CT images acquisition

Once prepping and draping is completed, cone-beam CT acquisition is performed. A common concern with CT acquisition is radiation exposure. During our first procedure, a higher quality cone-beam CT protocol was used (12-s scan protocol with 60 frame/s, 0.36 μGy/frame and 546 projections acquired over 220°) in order to have images similar to a standard CT scan. With increasing experience, the acquisition protocol was gradually changed (5 s scan protocol with 30 frame/s, 0.10 μGy/frame and 133 projections acquired over 200°), with a near 10-fold reduction in the total dose delivered in the last case compared to the first. This was obtained through collimation, applied to a different protocol combining a reduced number of projections acquired and lower radiation dose administered/frame. Despite poorer image definition, the pulmonary lesions can be easily differentiated from the surrounding parenchyma. As mentioned above, the main downside of this protocol is the reduction in size of the field of view which translates into considerable risk of not including the whole chest perimeter in the images. To overcome this limitation, we suggest, especially in obese patients, to minimize the distance between patient and OR table, removing any unnecessary layer and selecting the thinnest possible mattress [4].

Choice of trajectory for placement of metallic marker

Intraoperative CT images are jointly reviewed by radiologists and thoracic surgeons to confirm the presence of the lesion and to plan the trajectory for percutaneous placement of the metallic marker. The trajectory for the placement is planned using a dedicated software of the robotized angiography (Syngo X-Workplace; Siemens Healthcare GmbH, Erlangen, Germany). Whenever possible, the trajectory is driven perpendicular to the nearest pleural surface, avoiding anatomical obstacles (e.g., ribs and scapula). In case they are present, a deviation of ± 30° is considered acceptable. If this trajectory is not crossing any fissure and is presumably not in conflict with the stapler during the resection, a hookwire is placed. In all remaining situations, a coil is used (Fig. 2).

Fig. 2
figure 2

Criteria for marker selection. a, b A hookwire is preferred if the marker can be placed with a trajectory perpendicular to the nearest pleural surface (with a deviation of ± 30°). If that is impossible, an anatomical obstacle exists (e.g. scapula) or the lesion is very deep, a coil is used (c, d)

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Metallic marker placement

Both types of markers are inserted percutaneously through a needle and deployed close the lesion. The dedicated software provided fluoroscopic guidance during the procedure. Before the marker deploying, the exact position of the needle is checked by CBCT. If a coil is inserted, the marker final position is checked with CBCT.

iVATS

After lesion localization with hookwire single-lung ventilation is initiated immediately before pleural incision. The surgeon would slightly push on the free end of the wire, to prevent its withdrawal during lung deflation. To identify the lesion, gentle traction is applied on the wire. The resection is completed with endostaplers.

Following placement of a coil, lung collapse is established after patient positioning. Fluoroscopy allows intraoperative localization of the coil and cross-check of the relative position between coil and stapler, before firing. It is also used to confirm that the coil is within the specimen (Fig. 3).

Fig. 3
figure 3

a The preoperative chest CT scan showing a subsolid lesion of the apical segment of the right lower lobe. In the b, the needle trajectory is illustrated. The coil was inserted and the marker final position was checked with CBCT (c). During iVATS (d), fluoroscopy allowed intraoperative localization of the coil (e). The resection was performed with endostaplers. Fluoroscopy was also used to confirm that the coil was within the specimen (f)

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Our preferred VATS technique for this type of procedure is an anterior-approach three-port technique, although a bi- or mono-portal approach can also be used.

Result control

In particular cases, i.e. in presence of very small subsolid lesions, the surgeon may have the necessity to evaluate the efficacy of the resection, in order to be sure of having taken off the nodule. In this context, the availability in the HOR of an intraoperative CT scan may be very useful. In this patient (Fig. 4a), with a small (> 1 cm) subsolid lesion in the left upper lobe, we localized the target with a hookwire (Fig. 4b), and then, we performed a wedge resection in the attempt to remove the lesion. However, at the end of the resection, we were not completely confident to have removed the lesion. For this reason, after the re-inflation of the lung, a new CT scan was acquired and the lesion was identified in close proximity of the suture line (Fig. 4c). The lesion was therefore removed with a new wedge resection, through a standard muscle-sparing thoracotomy.

Fig. 4
figure 4

a Preoperative CT scan of the chest. b Intraoperative cone-beam CT scan performed after the hookwire placement. c Intraoperative cone-beam CT scan performed at the end of VATS resection (see text)

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Other techniques to localize lung nodules in a HOR

Virtually every technique for the preoperative localization of non-palpable lung nodules may be used in a HOR, and at present, no firm recommendation can be made on the optimal methodology [6]. Our preference, however, goes to the use of hookwires and coils. In our clinical practice, we have adopted an algorithm for the intraoperative localization of non-palpable nodules in the HOR based on the alternative use of both types of metallic markers, depending on the target position (Fig. 2). In our algorithm, the position of the target and the intraoperative strategy determine the choice of the marker. Placement of a hookwire is preferred as the marker can be seen directly and the resection can be completed without fluoroscopy. To be useful, a hookwire should be inserted perpendicular to the visceral pleura surface, so that the wire can be used as a retraction device to facilitate the resection with endostaplers. On the contrary, the usefulness of a coil is independent of its insertion route [4].

Analysis of the literature

Although the single-stage localization and removal of non-palpable lung nodules through iVATS is a relatively new procedure, a significant number of papers [1, 5, 7,8,9,10,11,12,13,14,15] have been already published in the literature (Table 1). In these studies, the median localization time ranges from 13 to 46 min, the percentage of successful marker-guided VATS resection ranges from 90 to 100% and the postoperative complication rate is similar to that of standard VATS procedures.

Table 1 Series from the literature of image-guide video-assisted thoracoscopic surgery (iVATS) procedures performed in hybrid operating rooms
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Two studies have recently compared the conventional nodule localization in the radiology suite, with that performed in the HOR, in terms of efficacy and safety.

Chen et al. [16] compared 50 patients who underwent preoperative CT-guided dye localization for VATS resection in the CT room and 25 patients who underwent intraoperative CT-guided dye localization and VATS surgery in the HOR. Localization was successfully performed in 50 patients (100%) and 23 patients (92%) in the CT room and HOR groups, respectively. In the HOR group, the global time was shorter and the localization time was longer. All nodules were successfully resected in both groups. The authors concluded that localization in the HOR seems an effective alternative method for managing small lung nodules.

Chao et al. [17] compared intraoperative computed tomography (IOCT)-guided nodule localization and resection performed in a HOR with conventional 2-stage preoperative CT (POCT)-guided approach for the treatment of non-palpable nodules. In this study, all lung nodules were successfully localized and removed using VATS. The use of a HOR significantly reduced the patient time at risk (e.g. the interval from completion of localization to skin incision). However, the IOCT-guided approach significantly increased the time under anaesthesia and the total operating room utilization time. The authors concluded, compared with the POCT-guided approach, the IOCT-guided approach decreased the time at risk, despite a significant increase in operating room utilization time. Because no significant outcome differences were evident, the choice between the two approaches should be based on the most readily available approach at a surgeon’s specific facility.

Personal experience

Between April 2016 and June 2019, 36 consecutive iVATS procedures were performed at our institution, removing in total 40 lung lesions. All included patients gave their informed written consent to surgery and to personal data management for scientific purposes. Only patients with lung nodules with high probability of malignancy and deemed not to be palpable through a VATS approach were included in the study. Exclusion criteria were previous homolateral thoracic surgery and pulmonary lesions larger than 3 cm in diameter. The median lesion size was 11 mm (range 5–25 mm); 14 lesions were subsolid and 26 solid. The median distance to the closest pleural surface was 12 mm (range 2–30 mm) from the superficial border of the lesion and 22 mm (range 9–42) from its deep edge. Lesion localization was performed with metal hookwires in 19 patients and with a coil in 17 cases. Median length of the localization procedure was 27 min (range 10–56 min). A dislodgment of the hookwire was observed in 2 patients (successful localization rate = 94.4%). In both patients, however, the planned VATS wedge resection was successfully performed under guidance of the puncture hole on the lung surface. Thirty-four wedge resections were completed by VATS, and 2 required conversion to thoracotomy (conversion rate = 5.5%). The reasons for conversion to thoracotomy were diffuse adhesions in one patient and the proximity of the lesion to the pulmonary vein in the other one. Nine lobectomies (7 VATS and 2 open) were performed (during the same operation) for primary lung cancer. Median surgical time was 77 min (range 33–280 min). Postoperative complication rate was 8.3% (3/36), and 2 patients showed postoperative prolonged air leak and 1 developed a postoperative pneumonia. Patients were discharged home on postoperative day 4 (median, range 2–21).

Conclusions

With the widespread availability of lung cancer screening programs, the number of small lung nodules requiring histological characterization has dramatically increased. Because both CT-guided fine-needle aspiration and bronchoscopic trans-bronchial biopsy may frequently yield false-negative results, excisional biopsy using VATS is frequently required. Although VATS procedure has been known to be ideal for nodule resection, the identification of very small, subsolid and deep pulmonary nodules may be still challenging. Precise lesion localization is a key prerequisite to avoid conversion to an unplanned thoracotomy [14, 18,19,20].

In the traditional workflow, the localization procedure is performed in the radiology suite after which the patient is moved to an operating room. With the availability of HORs, a new approach encompassing simultaneous localization and removal of non-palpable lung nodules has become feasible [1, 15].

On the basis of literature data and our experience, centralization of localizing and resecting procedures for the non-palpable nodules within a HOR seems to enhance diagnostic yield and minimize the likelihood of unplanned conversion to thoracotomy as well as avoid the potential complications of placing metallic markers according to the conventional strategies.

Future efforts should be tailored to compare iVATS with previously established localization techniques in terms of diagnostic accuracy, complication rates and cost-effectiveness. However, on the basis of current knowledge, it seems rational to suggest to all thoracic surgeons working in a hospital equipped with a HOR to use it as an adequate setting to localize and remove non-palpable lung nodules.