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1 Department of Radiology, Stanford University Medical Center, 300 Pasteur Dr.,
Rm. S-072, Stanford, CA 94305-5105.
2 Department of Radiology, University of Vienna, Waehringer Guertel 18-20, A
1090 Vienna, Austria.
3 Department of Cardio-Thoracic Surgery, University of Vienna, A 1090 Vienna,
Austria.
4 Institute of Clinical Pathology, University of Vienna, A 1090 Vienna,
Austria.
Received April 9, 2002;
accepted after revision August 8, 2002.
B. L. Partik is supported by a Max Kade Grant.
Abstract
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SUBJECTS AND METHODS. Guidewires were positioned under CT fluoroscopy guidance in 16 patients (11 men, five women; age range, 39-79 years; mean age, 60.4 years). We measured the size of the targeted nodule, its distance to the closest pleural surface, the angle between the introducer needle and the chest wall, and the time for performance of the procedure in each patient. Note was made of any complications after guidewire placement.
RESULTS. In the 16 patients, the average nodule size was 6.7 mm (range, 3-12 mm), the average distance to the pleural surface was 10.6 mm (range, 3-22 mm), and the average pleural puncture angle was 59° (range, 25-78°). The marking procedure was completed within an average of 9.5 min (range, 7-15 min). Small pneumothoraces occurred in five (31.3%) of 16 patients. In 15 (93.8%) of 16 patients, thoracoscopic resection of the targeted nodule was successful; in one patient with dyspnea (6.3%), inaccurate localization resulting in an open thoracotomy occurred because an intervening fissure was not visualized. Dislodgement of the guidewire into the pleural space occurred in one patient (6.3%).
CONCLUSION. The dedicated lung-marker system is a fast and effective method for localization of pulmonary nodules before thoracoscopic resection.
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Previous studies with limited numbers of patients have reported various localization techniques including injection of coils [6], contrast media [7, 8], cyanoacrylate [9], and methylene blue [10]. Localization using guidewires has been reported in larger series, sometimes performed in combination with methylene blue injection [11,12,13,14,15,16,17,18]. To our knowledge, all these reported guidewire systems were either custom-made or not specifically designed for lung tissue but rather for localization of breast lesions.
Recently, Kloeppel et al. [19] reported their initial results in five patients using a commercially available, CT-guided dedicated lung-marker system. In this study, planning of interventional parameters (cutaneous location, angle, and length of needle pass way) was performed using a laser marker system that was assembled in front of the gantry and calibrated to the CT unit with a phantom [20].
The goal of our study was to prospectively evaluate the effectiveness of the same lungmarker system in a larger number of patients under guidance of a more widely available CT fluoroscopy unit.
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25 mm), and were technically operable using video-assisted thoracoscopic
surgery. One patient with a 12-mm nodule was also included because surgeons
thought it would be technically difficult to target that particular nodule
without guidewire localization. Although no patient was excluded from this study, exclusion criteria for the procedure included nodules that would require a transfissural needle approach because of their location, bullae or blebs between the lesion and the pleural surface that were likely to cause an immediate pneumothorax and make deployment of the spiral guidewire tip impossible, severe dyspnea, and severe obesity requiring an introducer needle longer than 15 cm. In general, anticoagulation therapy would also be a contraindication for the marker procedure. However, all patients in our study population were scheduled for the procedure immediately before undergoing surgery; therefore, none was taking anticoagulation medication.
A primary malignancy was known to exist in nine patients at the time of referral. Melanoma was the most common malignancy, affecting three patients; carcinoma of the breast, rectum, kidney, liver, uterus, and myeloic leukemia were each present in one patient. The remaining individuals were referred for localization of asymptomatic nodules.
All examinations and interventions were performed on the same CT unit (Somatom Plus 4; Siemens, Erlangen, Germany) by one of three board-certified radiologists experienced in CT-guided interventional techniques. The nodule was localized on a thin-section CT scan (collimation, 3 mm; table feed, 5 mm; reconstruction increment, 4 mm; 140 kV; 120 mAs) covering a maximal length of 10 cm. On the basis of nodule location, the patients were placed in the CT gantry to minimize lesion depth and optimize the wire approach and angulation in the supine (n = 10), prone (n = 5), or oblique (n = 1) position. Patients were requested not to change body or arm positions for the duration of the procedure.
The marker system we used was a localization kit (Marker System for Lung Metastasis; Somatex, Rietzneuendorf, Germany) consisting of an 18-gauge introducer needle (length, 12 or 15 cm) with a stylet, an insertion device, and a guidewire. The guidewire is monofil and made of ninitol to provide shape memory for the helically formed atraumatic guidewire tip (2.5 turns; diameter when deployed, 10 mm) (Fig. 1). All sets are packed with the guidewire loaded in the insertion device. The helical guidewire tip is advanced out of the end of the insertion device and shielded by a small cap. Before the intervention, the cap must be removed and the guidewire tip completely drawn into the insertion device.
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Local anesthesia was obtained using 1-2% subcutaneous lidocaine, with the injection extended to the level of the parietal pleura in an attempt to achieve deep anesthesia [16]. The introducer needle was then advanced under intermittent CT fluoroscopy guidance (collimation, 10 mm; 120 kV; 50 mAs) or real-time CT fluoroscopy adjacent to or into the nodule. No additional devices were used for manipulating the introducer needle. After withdrawal of the stylet, the insertion device with the preloaded localization wire was deployed at the same location. Deployment of the guidewire requires no rotational or screwing motion. Before removing the insertion needle and insertion device, we confirmed that the guidewire tip was correctly positioned. The angle between the introducer needle and the pleural surface was noted. We measured the time needed to perform the procedure from the application of local anesthetic to the removal of the introducer needle.
The external portion of the wire was loosely coiled on the patient's chest and draped with sterile covers. Subsequently, we determined whether pneumothorax, hematoma, or any other finding was present on a final thin-section CT scan obtained using the same parameters that were used for the initial scanning. Finally, we assessed the distance of the helical-shaped wire tip from the target.
The patient was then transported in a bed to the preoperative holding area. Any subjective complaints of patients were documented. A short written report and copies of relevant CT images were sent to the operating room.
Patients underwent surgery no more than 1.5 hr after the marking procedure was completed. After surgery, the thoracic surgeons were requested to fill in a standardized form documenting the position and accuracy of the guidewire localization.
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After the intervention, small pneumothoraces were found in five (31.3%) of 16 patients. In four of the five patients, the pneumothorax consisted of a small localized tenting of the visceral pleura surrounding the wire insertion site, with a maximal separation between the visceral and parietal pleura of less than 10 mm (Fig. 3). In the remaining patient, a 5-mm separation between the visceral and parietal pleura was seen along a larger extent of the chest wall. No hematomas were identified in any patient. One (6.3%) of 16 patients complained about breath-dependent pain near the guidewire insertion site approximately 5 min after completion of the procedure. No pneumothorax or hematoma was seen on the final CT scans or on conventional posteroanterior and lateral chest radiographs.
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Intraoperatively, in 14 (87.5%) of 16 patients, the guidewire tip was found in or adjacent to the targeted nodule. Thoracoscopic resection of the targeted nodule was successful in 15 (93.8%) of 16 patients. In the patient with dyspnea, the nodule, which was assessed to be in the anterior aspect of the right lower lobe and localized via a posterior approach, was not found in the resection specimen. At open thoracotomy, the nodule was located in the posterior aspect of the upper lobe immediately anterior to the major fissure. Guidewire migration into the pleural space occurred at the time of lung deflation in one (6.3%) of 16 patients. In this patient, a puncture mark was seen on the visceral pleura, indicating the prior entry site of the wire into the lung. The nodule was successfully resected thoracoscopically using the entry site as a landmark.
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Unlike other guidewires, the lung-marker system used in our study was designed specifically for lung parenchyma and is commercially available. The helical tip provides a cross-sectional area of 78 mm2 that allows thoracic surgeons to apply mild retractile force when tenting the lung so that easier access to the resection site is available and removal of the tissue can be achieved without causing wire dislodgement. Moreover, the shape memory of the wire potentially enables repositioning without deformation of the helical tip. Although previous studies have reported hematoma rates of 6.9-35.3%, we found no hematomas in the lung or chest wall in our patients [15, 16]. It is likely that our results are attributable to the monofil structure and atraumatic tip of the wire. Moreover, pneumothoraces were seen in only 31.3% of patients in our study, as compared with 45.5-50% of patients in studies using other systems [14, 16, 18].
Under guidance of CT fluoroscopy, we achieved a rapid targeting of small nodules with an average size of 6.7 mm. Our marking procedure was completed within an average of 9.5 min, whereas Friedrich et al. [21] reported a range of 12-21 min for their first three procedures when using a laser marker system for guidance. Other authors have reported procedure times ranging from 20-60 min for the localization of pulmonary nodules under CT guidance [11, 12, 17, 18]. However, comparison of procedure times remains difficult, because precise definitions for times measured are not available in the literature.
Our technique was well tolerated by the patients. Only one (6.3%) of 16 patients complained of pain after the procedure, which likely was due to pleural irritation at the insertion site of the guidewire. No associated complications were seen on this patient's CT scan obtained after the intervention.
In 15 (93.8%) of 16 patients, the guidewire was located in or adjacent to a variety of benign and malignant lung lesions as documented on thin-section CT scans. In one patient, the guidewire tip was placed 13 mm dorsocaudad relative to the targeted 8-mm nodule, which was located 20 mm from the pleural surface. Repositioning was not attempted because video-assisted thoracoscopic resection usually includes all lung tissue within 20 mm of the wire tip and because this patient had severe dyspnea. However, the nodule was not present in the resection specimen. At open thoracotomy, the guidewire was found deployed in the lower lobe, whereas the nodule was located in the upper lobe just anterior to the major fissure. Retrospective review of the postintervention CT scan showed that significant motion artifact resulted in nonvisualization of the intervening fissure. In general, care must be taken when nodules are in a perifissural location to ensure that the needle approach does not cross any fissures and thus complicate thoracoscopic resection [16].
Guidewire dislodgement into the pleural space was found in one (6.3%) of 16 patients after surgical deflation of the lung. In this patient, the targeted nodule was 10 mm in maximal diameter and located 3 mm from the chest wall adjacent to a rib, near the medial border of the scapula. Successful placement of the guidewire required an acute pleural puncture angle of 25° (Fig. 4), whereas an average puncture angle of 61.6° (range, 40-78°) was used in the remainder of our patients. In our opinion, the shallow angle between the introducer needle and the pleural surface as well as the short length of the guidewire inserted into the lung parenchyma predisposed the wire to dislodgement.
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Previous studies have reported dislodged dedicated breast-marker systems in 6-60% of patients [14,15,16, 18, 22]. As an adjunct to guidewire placement, some investigators have also injected methylene blue to create a tattoo on the pleural surface that can serve as a guide in case of wire dislodgement [11, 16]. However, the use of methylene blue is controversial because some patients may suffer from adverse effects such as hypotension and bronchospasm [15]. Although no complications were encountered in the series by Thaete et al. [16], the site of the methylene blue injection was not visualized on videothoracoscopy in nine of their 22 cases of wire dislodgement.
In general, wire dislodgement may occur at the time of lung deflation, during the resection when the surgeon applies gentle retraction on the wire to tent the lung or during transport to the operating room [14]. The delicate parenchyma of the lung provides much less resistance when traction force is applied than does breast tissue. Because the anchoring power of the guidewire tip is related to the cross-sectional area of the hook, Mullan et al. [14] developed a custom-made guidewire with a hook in the shape of a cloverleaf consisting of four loops oriented at 90° to each other; none of the five cloverleaf wires deployed in their series dislodged. Kanazawa et al. [23, 24] developed a short guidewire with a long nylon suture attached to its proximal end to decrease guidewire inflexibility and rigidity—characteristics that these authors believe contribute to guidewire dislodgement, particularly during patient transport. Although wire dislodgement occurred in only three (8.1%) of 37 patients in the Kanazawa et al. series [24], the cross-sectional area of their hookwire (diameter, 0.28 mm) is small and may predispose the wire to dislodgement when greater degrees of tensile force are applied.
Our study has several limitations. First, the relatively small size of our sample precludes any firm conclusions regarding the incidence of complications in comparison with other techniques. However, the present data and usefulness for both patients and thoracic surgeons are promising. Second, it is possible that the true incidence of pneumothoraces was underestimated because the diagnosis was made on CT scans acquired after the intervention. We cannot rule out that delayed pneumothoraces might have occurred on the way to the operating room. However, no patient required drainage for relief of a symptomatic pneumothorax.
If the use of low-dose helical CT to screen for early-stage lung cancer becomes wide-spread, it is likely that radiologists in the near future will encounter an increasing number of small pulmonary nodules [25]. We presume that such findings will also increase the number of patients requiring thoracic surgery. The use of a feasible, safe, and fast marker system for small nodules can facilitate surgical resection by accurately localizing the lesion, thereby reducing the amount of resected tissue as well as obviating open thoracotomy. Compared with open thoracotomy, video-assisted thoracoscopic surgery decreases operating time, length of patient stay in the hospital, costs, and patient discomfort [4].
In conclusion, the dedicated lung-marker system used in conjunction with CT fluoroscopy is a fast and effective method for localization of pulmonary nodules. Small pneumothoraces were the most frequent complication in five (31.3%) of 16 patients. When nodules are in a perifissural location, care must be taken to ensure the needle approach does not cross any fissures, because this will complicate thoracoscopic resection.
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