This study aims to evaluate whether femtosecond laser imaging combined with FastLung AI model can provide intraoperative diagnostic performance that is non-inferior to standard frozen section diagnosis for pulmonary nodules or suspected pulmonary tumor lesions. Patients scheduled for lung surgery and requiring intraoperative pathological assessment will be prospectively enrolled. After tumor excision, the fresh tumor specimen will be bisected through the central plane. One half will be used for standard frozen section diagnosis, and the mirrored counterpart will be used for femtosecond laser imaging. Both diagnostic results will be compared with the final paraffin-embedded pathological diagnosis as the reference standard. The results of femtosecond laser imaging will not guide intraoperative clinical decision-making.

This is a prospective, multicenter, paired diagnostic accuracy study designed to evaluate the non-inferiority of femtosecond laser imaging compared with standard frozen section diagnosis for intraoperative assessment of pulmonary nodules or suspected pulmonary tumor lesions.

Eligible patients with pulmonary nodules, pulmonary space-occupying lesions, or suspected pulmonary tumor lesions who are scheduled to undergo surgical resection and require intraoperative pathological assessment will be prospectively enrolled from participating centers. After surgical excision of the tumor specimen, the fresh specimen will be bisected through the central plane. One half of the specimen will be submitted for routine frozen section diagnosis, while the mirrored counterpart will be used for femtosecond laser imaging. This paired design is intended to allow spatially corresponding comparison between the two diagnostic methods while preserving routine clinical workflow.

Frozen section diagnosis will be performed according to standard intraoperative pathological procedures and will continue to guide intraoperative clinical decision-making. Femtosecond laser imaging will be performed on fresh tissue specimens for research purposes. The imaging results will be recorded for diagnostic performance evaluation but will not be used to guide intraoperative surgical decisions.

The diagnostic results of femtosecond laser imaging and frozen section diagnosis will both be compared with the final paraffin-embedded pathological diagnosis, which will serve as the reference standard. The primary objective is to determine whether the diagnostic accuracy of femtosecond laser imaging is non-inferior to that of frozen section diagnosis. Secondary objectives may include comparisons of sensitivity, specificity, positive predictive value, negative predictive value, diagnostic concordance, and intraoperative assessment time between the two methods.

Inclusion Criteria:

1. Preoperative imaging suggests a pulmonary nodule, pulmonary space-occupying lesion, or suspected pulmonary tumor lesion.
2. The participant is scheduled to undergo pulmonary wedge resection, segmentectomy, lobectomy, or other pulmonary surgery.
3. Fresh lung tissue specimens can be obtained intraoperatively for femtosecond laser imaging.
4. Intraoperative frozen section diagnosis is planned to assess the nature of the tumor lesion.
5. Corresponding postoperative paraffin-embedded pathological diagnosis can be obtained.
6. The participant or the participant's legally authorized representative has signed the written informed consent form.

Exclusion Criteria:

1. The intraoperative specimen is insufficient and cannot simultaneously meet the requirements for routine clinical pathological diagnosis and research-related testing.
2. The specimen shows severe carbonization, necrosis, compression, contamination, or improper preservation, and the investigator determines that effective imaging cannot be completed.
3. The femtosecond laser imaging specimen cannot be matched with the corresponding lesion assessed by final paraffin pathology.
4. Final paraffin-embedded pathological diagnosis cannot be obtained.
5. The participant withdraws informed consent.
6. Other conditions that, in the opinion of the investigator, make the participant unsuitable for this study.

The study population will consist of patients with pulmonary nodules, pulmonary space-occupying lesions, or suspected pulmonary tumor lesions who are scheduled to undergo surgical resection at participating centers. Eligible patients will require intraoperative pathological assessment, and fresh lung tissue specimens must be available for both femtosecond laser imaging and standard frozen section diagnosis. All participants will be prospectively enrolled according to the predefined inclusion and exclusion criteria, and the diagnostic results will be compared with the final paraffin-embedded pathological diagnosis as the reference standard.

Individual participant data will not be publicly shared due to patient privacy considerations and institutional data-sharing restrictions. De-identified aggregate results may be made available in publications or upon reasonable request, in accordance with applicable regulations and institutional policies.