The institutional review board of our hospital approved the present retrospective study and waived the requirement for informed consent for collecting data from the related patients. Written informed consent for CT-guided percutaneous localization has been obtained from all patients prior to performing the procedure.
Study Subjects
From June 2016 to March 2019, 249 consecutive patients (90 males, 159 females) with 279 pulmonary nodules underwent CT-guided microcoil localization prior to VATS at our radiology department were enrolled in this study. Exclusion criteria for CT-guided microcoil localization were the following: 1) nodules adjacent to the hilum or apparent vascular structure; 2) lesions located in the bronchi; 3) patients who refused to microcoil localization or VATS resection.
Of these, 28 patients (male/female: 10/18; mean age: 57.7 ± 8.0 years) underwent simultaneous localization for multiple pulmonary nodules (26 two-nodule, 2 three-nodule, total 58 nodules; Group A), and the other 221 patients (male/female: 80/141; mean age: 57.3 ± 11.3 years) underwent localization procedures for 221 nodules (Group B). None of them has received the examination of needle biopsy for the current pulmonary lesions before. The median interval between CT interventional procedure and VATS was 27.8 hours (range, 0.9∽95.7 hours). The clinical characteristics of the patients were summarized in Table 1.
Table 1
The clinical information of the patients underwent CT-guided microcoil localization
Variable | | Different groups | p-value |
| | Group A | Group B | |
Patients No. | | 28 | 221 | - |
Nodule No. | | 58 | 221 | - |
Age (y) | Mean ± SD(range) | 57.7 ± 8.0 (39∽77) | 57.3 ± 11.3 (26∽81) | 0.825 |
| ≤ 55/ >55 | 13/15 | 94/127 | 0.695 |
Gender | Male/ Female | 10/18 | 80/141 | 0.960 |
Smoking status | Ex- or current/ Never | 2/26 | 28/193 | 0.546 |
Cancer history | Primary lung/ Extra-pulmonary/ No | 0/2/26 | 10/18/193 | - |
Previous thoracic operation | Yes/ No | 0/28 | 10/211 | - |
FEV1.0/FVC (%) | Mean ± SD (range) | 74.3 ± 9.9 (44.6∽91.5) | 77.2 ± 7.4 (52.9∽91.5) | 0.061 |
Localization procedure time (min) | Median ± IQR (range) | 24 ± 7.5(13–45) | 13 ± 6(5–52) | < 0.001 |
The time to the operation (hour) | Median ± IQR (range) | 19.2 ± 16.9 (0.9∽72.6) | 20.0 ± 12.7 (1.0∽95.7) | 0.202 |
| ≤ 24/ >24 | 21/7 | 144/77 | 0.299 |
Abbreviation: FEV1.0/FVC, forced expiratory volume at 1 second/forced vital capacity; SD, standard deviation; IQR, interquartile range. |
Ct-guided Microcoil Localization
Before CT-guided localization procedures, patients were trained to hold the breath for 5–10 seconds at the end of inspiratory. All the planning and localization CT scans were carried out using the same 16-detector-row scanner (Aquilion 16;Canon Medical Systems, Japan). The following parameters for the planning CT: scanning method = helical acquisition mode; tube currents = 50mAs; tube voltage = 120kVp; rotation time = 0.5 sec; imaging FOV = 400; slice thickness = 5 mm, the following parameters for the localization CT: scanning method = axial acquisition mode; tube currents = 50mAs; tube voltage = 120kVp; rotation time = 0.5 sec; imaging FOV = 400; slice thickness = 4 mm. The limited slices were scanning including lesion and microcoil for saving radiation dose.
A planning CT scan was performed before percutaneous needle insertion. An appropriate puncture point on a patient’s skin was marked to get the shortest needle entry route meanwhile avoiding the inclusion of bullae and vessels structures. Embolization microcoil (Cook Incorporated, Bloomington, IN 47404, USA) was selected as a localization marker with a wire diameter of 0.018 inches and a length of 7 cm. After local anaesthesia with 2% lidocaine, an 18G/10 cm percutaneous introducer needle (Cook Incorporated, Bloomington, IN 47404, USA) was then advanced to puncture from the marked point on the skin without penetrating the parietal pleura. After confirming the direction of the tip of the puncture needle by the second CT scan, further insertion into the normal lung parenchyma around the lesions (within 5 mm) was carried out. Then the third CT scan was performed to confirm the final position of the tip of the needle before connecting the loading cannula of the microcoil to the needle. Our method for deploying the microcoil was a modified procedure from Powell’s method [5]. The microcoil was implanted adjacent to nodule within 5 mm instead of nodule penetration, which may incite hemorrhage or inflammation in the nodule and then affect histopathologic assessment [20]. The intention of our method was to leave the proximal end of the microcoil on the visceral pleura, which will be a direct clue for nodule’s position during VATS resection and significantly improve the efficiency of surgery [14].
Basing on the learning curve analysis described by Chao et al [21], the over-33-month (from June 2016 to March 2019) operational process of the interventional radiologists could be divided into two stages: the initial 16-month and the later 17-month. In the initial 16-month, the radiologists were with limited experience for evaluating microcoil dislodgement or migration (localization failure) on CT scans and the microcoil implantation used to be given only once for one nodule, while in the later 17-month, a repeated localization procedure would soon be done if the radiologists predicted the proximal end of the first microcoil was likely to dislodge or detach from the visceral pleura on post-procedural CT images. And the procedure-related complications were evaluated based on the Society of Interventional Radiology Standards of Practice Committee Classification [12].
Surgical Procedure
VATS was performed under single-lung ventilation with a double-lumen endotracheal tube and general anaesthesia. The patient was placed in the lateral decubitus position, with the involved lung in the superior location. According to preoperative images, a thoracoscopic port inserted into the pleural cavity through appropriate intercostal space. The other two ports were placed to insert a grasping instrument and a linear stapling device.
Under the guidance of VATS and preoperative localization CT (Fig. 1a-e), the excision of the complete microcoil and nodule was carefully performed and the specimen was immediately sent for frozen section. The frozen sections were used to evaluate whether the extended resection was necessary and/or the lesion was completely resected. Completion lobectomy was performed unless the lesion was found to be noninvasive cancer, or the patient had an inadequate cardiopulmonary reserve, or the patient had lung resection before, or the patient declined to extended resection.
Assessment
The successful targeting rate, localization rate, VATS rate, and procedure-related complications rate were calculated based on the total number of the nodules [11, 22]. Successful targeting was defined as implantation of microcoil at the target site adjacent to a nodule on CT image obtained immediately after the marking procedure and the rate was calculated as follows: (number of successful targeting procedures/number of all localization procedures in each group)x100; successful localization was defined as detection of nodule location and the rate was calculated as follows: ([number of successful targeting procedures-number of dislodgements or misses under the thoracoscope]/number of all localization procedures in each group)x100; successful VATS was defined as complete resection of the target nodule with adequate margin and the rate was calculated as follows: ([number of successful VATS /number of all localization procedures in each group)x100. The severity of procedural complications was also recorded according to the Society of Interventional Radiology Standards of Practice Committee classification of complications [12].
In addition, all preoperative CT data was transmitted to the picture archiving and communication system (PACS) and scanner workstation. Nodules were classified as solid, part-solid and ground-glass opacity (GGO) according to their density on CT images with a lung window setting (level:-450HU; width: 1300HU). One nodule was defined as GGO when it had increased attenuation relative to parenchyma but was not as dense as soft tissue density (such as the parenchymal vessels). Part-solid nodule contained some areas with solid attenuation component. The nodule characteristics and localization procedure-related variables, including nodule location, size, type, depth from pleura (the shortest vertical distance), presence of emphysema (around the needle insertion pathway), patient position for localization procedure (prone or supine), needle-pleural angle, pleura-microcoil distance (along the needle insertion pathway), presence of “pleural indentation” (defined as the manifestation that the pleura was not penetrated by the needle and protruded towards the nodule, resulting in a tent-shaped appearance of the pleura), scapulae-covered sign (nodule was shadowed by the scapulae), presence of procedure-related complications (pneumothorax or pulmonary hemorrhage), localization procedure time (defined as the interval time between the initial CT scan scout film before puncture and last CT scan followed localization procedure) as well as the time to the operation (defined as the interval time between the termination of the postprocedural CT scan in the interventional unit and the start of the general anaesthesia in the operating room) were measured and recorded. The comparison of clinical characteristics and procedure-related variables between Group A and B were recorded in Tables 1 and 2.
Table 2
Summary of nodule characteristics
Variable | | Different groups | p-value |
| | Group A | Group B | |
Nodule size (mm) | Median ± IQR (range) | 7.1 ± 3.6 (2.3∽18.9) | 9.8 ± 5.8 (2.8∽26.8) | < 0.001 |
| ≤ 5 mm | 10 | 12 | < 0.001 |
| > 5∽10 mm | 38 | 106 | |
| > 10∽15 mm | 9 | 74 | |
| > 15 mm | 1 | 29 | |
Nodule location | Right/ Left side | 39/19 | 131/90 | 0.268 |
| RUL/RML/RLL | 21/0/18 | 86/14/31 | 0.011 |
| LUL/LLL | 10/9 | 63/27 | |
Nodule type | Solid/Part-solid/GGO | 20/12/26 | 36/33/152 | 0.002 |
Depth from pleura (mm) | Median ± IQR (range) | 12.6 ± 13.6 (0.0∽44.4) | 10.3 ± 16.7 (0.0∽53.1) | 0.781 |
| ≤ 5 mm | 14 | 52 | 0.159 |
| > 5∽10 mm | 12 | 57 | |
| > 10∽15 mm | 13 | 25 | |
| > 15 mm | 19 | 87 | |
Presence of emphysema★ | Yes/ No | 4/54 | 6/215 | 0.224 |
Position for localization procedure | Supine/ Prone | 24/34 | 108/113 | 0.309 |
Needle-pleura angle (°) | Mean ± SD(range) | 64.0 ± 14.0 (32.4∽88.9) | 61.2 ± 15.7 (21.1∽89.8) | 0.225 |
| ≤ 30° | 0 | 8 | 0.410 |
| > 30∽60° | 23 | 93 | |
| > 60° | 35 | 120 | |
Pleura-microcoil distance▼(mm) | Mean ± IQR (range) | 35.2 ± 9.4 (4.0∽57.8) | 34.07 + 10.3 (1.0∽55.9) | 0.378 |
| ≤ 10 mm | 2 | 11 | 0.211 |
| > 10∽20 mm | 0 | 13 | |
| > 20∽30 mm | 11 | 43 | |
| > 30 mm | 45 | 154 | |
Presence of pleural indentation | Yes/ No | 10/48 | 60/161 | 0.121 |
Presence of the scapulae-covered | Yes/ No | 4/54 | 42/179 | 0.027 |
Procedure-related complications | Yes/ No | 19/39 | 68/153 | 0.771 |
Pneumothorax | Yes/ No | 16/42 | 67/154 | 0.686 |
Intrapulmonary haemorrhage | Yes/ No | 7/51 | 26/195 | 0.949 |
Surgical procedure | Wedge resection/ Anatomic resection●/ Open thoracotomy | 46/12/0 | 134/85/2 | - |
Pathologic result▼▼ | Primary lung cancer/ metastasis/ Benign lesion | 37/0/21 | 175/3/43 | - |
Abbreviation: IQR, interquartile range; SD, standard deviation; GGO, ground glass opacity; RUL, right upper lobe; RML, right middle lobe; RLL, right lower lobe; LUL, left upper lobe; LLL, left lower lobe. Note: “★” The emphysema region was around the needle insertion pathway. “▼” Pleura-microcoil distance was measured along the needle insertion pathway. “●”Anatomic resection included lobectomy and segmentectomy. “▼▼”Detailed pathologic results were summarized in the Table 3. |
Statistical analysis
Statistical analysis was performed using SPSS 17.0 software (SPSS 17.0 for Windows, Chicago, IL). The Kolmogorov-Smirnov test for normality was performed on continuous variables and the graphical spread of the data was visually inspected. Descriptive statistics were shown as mean ± standard deviation (SD) or median ± interquartile range (IQR) for continuous variables, and as frequency and percentage for categorical variables.
The comparison of clinical characteristics and microcoil localization procedure-related variables between group A and group B were analyzed by Independent-samples t-test/Mann-Whitney U test, and the chi-square test/Fisher exact test. A two-sided p-value less than 0.05 was considered statistically significant.