The purpose of the study is to develop and validate an algorithm based on deep neural networks (DNNs) to identify interscalene brachial plexus on ultrasonography automatically.

The investigators plan to develop a deep learning-based network to automatically identify interscalene brachial nerves on ultrasound images. The trained model will be validated on an independent dataset. The performance of the network will also be compared against practicing anesthesiologists.

Inclusion Criteria:

• ASA physical status class I or II
• scheduled for elective surgery

Exclusion Criteria:

• skin lesion or infection of neck
• any known peripheral neuropathy
• brachial nerve plexus injury
• previous injury or operation on neck
• pregnancy
• allergic to ultrasound gel