Advances in medical imaging technology have made it possible to detect patients with small-sized lung lesions early. Generally, invasive methods such as PCNA were used to diagnose peripheral lung nodule. However, Radial probe endobronchial ultrasonography (RP-EBUS) is widely used in the histological diagnosis of peripheral lung nodule in recent years. In order to carry out RP-EBUS, it is necessary to know the path to the lesion to access it. Conventionally, the path to the peripheral lung nodule is identified by the drawing, but recently, the path is reviewed by the virtual bronchoscopy navigation (VBN) which is reconstructed 3-dimension image using the CT data. Currently, VBN is driven by using raw data acquired using standard thin sectioned chest CT protocol, but the problem is that additional doses of radiation are exposed to patients who have initially discovered lung lesions using low dose CT. Therefore, we conduct a randomized controlled trial to verify the suitability of VBN using the raw data acquired by low dose CT.

The standard thin sectioned protocol CT consists of scout, enhanced and non-enhanced image. Therefore, in this study, non-enhanced protocol CT was taken with low dose protocols with three different radiation doses to acquire raw data and drive VBN, and compared with the VBN result driven with raw data obtained with standard protocol. The primary endpoint of this study is to verify the consistency and accuracy of the VBN results driven by the raw data obtained with the low dose protocol CT.

1. Inclusion Criteria:

   1. Patients older than 18 years
   2. Competent to give informed consent
   3. Patients requiring a pathological diagnosis of pulmonary nodules using RP-EBUS.
   4. Patients who need chest CT before RP-EBUS.

2. Exclusion Criteria:

   1. Pregnancy
   2. Patients who could not receive chest CT
   3. Inability to obtain informed consent
   4. Patients unable to perform RP-EBUS