The aim of this study: 1. To evaluate the correlation between the clinic tools and ultrasound elastography/ ARFI imaging in stroke patients. 2. To assess the reliability of elastography/ ARFI imaging in spasticity evaluation of stroke patients.

Modified Ashworth Scale (MAS) and Modified Tardieu Scale (MTS) are the most commonly used tools for spasticity assessment. But these clinic methods cannot reveal the architecture and stiffness of muscles. In recent years, ultrasound elastography and acoustic radiation force impulse (ARFI) are used in musculoskeletal disorders, including spasticity. There are no studies about the correlation between spasticity and ultrasound elastography /ARFI imaging in stroke patients. The investigators will enroll 50 stroke patients with hemiplegia and biceps brachii muscle spasticity. One physical therapist will measure MAS and MTS for spasticity of biceps brachii muscle. Two physiatrists will perform ultrasound elastography and ARFI for intra-rater and inter-rater reliability evaluation. The evaluations of B-mode ultrasound, elastography and ARFI included Heckmatt scale, biceps brachii ratio, strain ratio, dynamic sonoelastography score, color intensity, and shear wave velocity. After performing all assessments, the investigators will analyze the correlation between the clinic tools and elastography/ ARFI imaging and evaluate the reliability of elastography/ ARFI imaging in spasticity evaluation.

Inclusion Criteria:

• stroke patients with hemiplegia and biceps brachii muscle spasticity.

Exclusion Criteria:

• elbow joint contracture deformity
• combined other neuromuscular system disease
• affected upper extremity has local infection
• patient who can't follow instruction, who is restlessness and whose elbow can't meet the positioning criteria

refer from physiatrists in Kaohsiung Chang Gung Memorial Hospital