This retrospective research was authorized by the ethical board of the First Affiliated Hospital of Ningbo University. Because of the retrospective nature of this study, the requirement of informed consent was waived. This investigation included SPL patients who underwent CT- or US-guided PNB in our hospital between January 2022 to January 2023. The inclusion criteria included patients (a) with SPLs strictly adherent to pleural surface, (b) with solid SPLs, and (c) with a high risk for lung cancer based on clinical/radiology characteristics (3). The exclusion parameters were: (a) patients who underwent PNB previously, (b) SPLs that reduced in size during follow-up, (c) SPLs that were completely blocked by the bone, and (d) patients with chronic cardiac, renal, pulmonary, or coagulatory disorders.

The 16 Slice CT (Siemens, Berlin, Germany) was employed for CT-guided PNB. The CT-guided PNB was performed by 2 radiologists with more than 5 and 10 years of experience for lung biopsy. The set parameters were: 100 mA tube current, 120 kV tube voltage, 0.6 second gantry rotation time, 2 mm thickness, and 1.1 pitch. The patient’s position and needle paths were based on the lesion’s location ( Figure 1A ). During the procedure, the co-axial technique was employed. The lesion samples were harvested by inserting A 17G outer needle (DuoSmart™, Modena, Italy) into the lesions, followed by the insertion of an 18G inner semi-automatic core needle (Wego™, Weihai, China) via the outer needle ( Figure 1B ). From each lesion, more than 2 samples were acquired, which were then preserved in 10% formaldehyde for pathological assessment. In addition, the cell blocks were also prepared for cytology assessment. The biopsy procedure-related complications were assessed by a repeat CT scan. The histo-cytological diagnoses were made by two pathologists with 5 and 10 years expertise in lung cancer.

For the US-guided PNB, a US system (Philips, EPIQ7) with the convex array probe C5-1 was routinely employed. The US-guided PNB was performed by 2 radiologists with more than 5 and 10 years of experience for lung biopsy. The parameters of the US were: (a) depth: 10-13 cm; (b) time gain compensation: time gain compensation curve is adjusted for the shape of “|” or “”; (c) focus pointe: the focus pointe was set in the midfield zone. The tissue harmonic imaging was activated. The probe was equipped with a holed guide for needle insertion of various angle selections based on the lesions’ size and locations. For the small lesions (1-2 cm), we used a high frequency probe (eL18-4) to guide the PNB because the high frequency probe could provide a high image resolution. The patient’s position was decided in advance via the safest and shortest approach to visualize the US probe’s movement ( Figure 2A ). The biopsy needle path toward the lesion was visualized in real time ( Figure 2B ). The PNB procedure was same as the that for the CT group. The biopsy procedure-related complications were assessed by a chest CT scan. The histo-cytological diagnoses were made by two pathologists with 5 and 10 years expertise in lung cancer.

The PNB-based diagnoses can be categorized into 4 types: (a) Suspected malignancy (described as atypical cells suspected of indicated malignancy) (9), (b) Malignancy, (c) Non-specific benignity (defined as benign pathology features that existed through and did not suffice for a formal diagnosis) (9), and (d) Specific benignity (described as lesions that were related to specific infectious diseases or benign tumors) (9). The PNB-based specific benignity and malignancy can be considered as the final diagnoses. However, the PNB-based non-specific benignity and suspected malignancy should be assessed further, such as by repeat biopsy, surgical resection, or CT follow-up. If the lesion size is reduced (≥ 20%) during the follow-up or is maintained (< 20%) for at least 1 year, it could be accepted as benignity (9).

At the final diagnosis, when PNB-based malignancy/suspected malignancy was confirmed as malignant the results were considered true positive (1). Whereas, when PNB-based benignity was confirmed as benignity at the final diagnosis the results were considered true negative (1). Diagnostic accuracy = (true positive + true negative)/all cases. Diagnostic yield = (PNB-based malignancy + PNB-based specific benignity)/all cases.

The PNB-related complications were classified as minor and major complications according to the Society of Cardiovascular & Interventional Radiology guidelines (10).

The not normally distributed and normally distributed continuous data were compared via the Mann-Whitney U test and the independent sample t-test, respectively. χ²/Fisher exact test was carried out to compare categorical data. Pneumothorax risk factors were assessed via univariate and multivariate logistic regression tests. The variables which exhibited a p-value < 0.1 in univariate analyses would be included in the multivariate analysis. The subgroup analyses were conducted based on the patients with lung nodules. SPSS 16.0 (SPSS, Chicago, Illinois, USA) was employed for all the statistical measurements and statistically, the p-value of < 0.05 was deemed as the significance threshold.

This research included 213 patients who underwent CT- (n = 108) or US-guided (n = 105) PNB diagnosis and had SPLs at the final diagnosis ( Table 1 ). Furthermore, both groups indicated similar operation times (20.1 ± 8.1 min vs. 19.9 ± 6.9 min, p = 0.793), respectively.

In the CT group, the PNB-based diagnoses included specific benignity (n = 4), malignancy (n = 74), and non-specific benignity (n = 30). Whereas the final diagnoses included benignity (n = 33) and malignancy (n = 75). Supplementary Table indicates the details of the final diagnoses. The diagnostic accuracy and yield were 99.1% and 72.2%, respectively ( Table 2 ).

In the US group, the PNB-based diagnoses included specific benignity (n = 5), suspected malignancy (n = 6), malignancy (n = 63), and non-specific benignity (n = 31). The final diagnoses included benignity (n = 36) and malignancy (n = 69). Supplementary Table indicates the details of the final diagnoses. The diagnostic accuracy and yield were 100% and 64.8%, respectively ( Table 2 ).

The rates of diagnostic accuracy and yield were comparable in both groups (p = 0.561 and 1.000).

In the CT group, 26 patients (24.1%) experienced pneumothorax, while 3 patients (2.7%) suffered hemoptysis. Furthermore, of 26 patients, 7 required chest tube insertion. In the US group, 2 patients (1.9%) experienced pneumothorax, 3 (2.9%) experienced hemoptysis, and none required chest tube insertion. In comparison with the US group, the CT group indicated markedly increased rates of chest tube insertion (p = 0.014) and pneumothorax (p = 0.001), whereas the hemoptysis rates were comparable in both groups (p = 1.000, Table 1 ). In the CT group, 19 patients were classified as minor complication and 7 patients were classified as major complication. In the US group, all of the 5 patients were classified as minor complication.

Table 3 shows the logistic analyses of pneumothorax. In the univariate analysis, the smaller lesion size (p = 0.01), larger needle-pleura angle (p = 0.054), decubitus position (p = 0.016), and CT guidance (p = 0.001). When these factors were included into the multivariate analysis, the independent risk factor was assessed to be CT guidance (p = 0.003).

Table 4 shows the subgroup analyses based on the lung nodules. The results indicated comparable diagnostic yield (62.1% vs. 59.0%, p = 0.749) and accuracy (100% vs. 100%) between CT and US groups. Furthermore, the incident rate of pneumothorax was markedly higher in the CT group than in the US group (24.4% vs. 2.6%, p = 0.004), while that of the hemoptysis was comparable in both the groups (3.0% vs. 5.1%, p = 0.627).