Photoacoustic imaging (PAI) is an emerging biomedical modality that integrates the advantages of optical contrast and ultrasound imaging depth. Capable of providing morphological, functional, and molecular information, PAI shows significant promise for visualizing human superficial tissue. The goal of this clinical trial is to build a PAI evaluation method for DM skin lesions, explore its application value in assessing DM disease severity and evaluation of treatment response. The main questions it aims to answer are:

1. How to establish a non-invasive PA/US imaging evaluation method for DM skin lesions?
2. Can PAI precisely assess DM disease severity?
3. Can PAI systems predict the treatment response in DM with calcinosis cutis? Participants will receive regular PA/US imaging examinations during five stages of treatment (before treatment, 3 months, 6 months, 9 months and 12 months). And the effectiveness of PA/US in treatment response for DM at different time points will be evaluated.

A multimodal photoacoustic-ultrasound (PA/US) system was integrated into a high-end commercial US platform, enabling real-time acquisition of grayscale imaging, color Doppler (CDUS), and dual-wavelength photoacoustic (PAI) data. The PA/US images were acquired using a hand-held probe integrated optical devices and US transducers. Researchers plan to recruit participants of DM with calcinosis cutis from the department of rheumatology in Peking Union Medical College Hospital. The patients are scheduled to receive multi-modality PA/US imaging examinations, which integrated gray scale ultrasound (GSUS), ultra-micro-angiography (UMA) and PAI to realize visualization and assessment of subcutaneous soft tissues in morphology, hemodynamics, blood flow and oxygenation. This clinical trial aims to address three key objectives: the establishment of a non-invasive PA/US imaging evaluation method for DM skin lesions, the applicaiton to assess DM disease severity, and the use of PAI to monitor the treatment response.

Inclusion Criteria:

• All patients fulfilled the 2017 EULAR/ACR classification criteria for idiopathic inflammatory myositis. Of the adult DM patients enrolled, those were found to have calcinosis and were subsequently included in our analysis.
• Among enrollees with idiopathic inflammatory myositis, patients with pathognomonic skin rashes were subclassified as DM or amyopathic DM patients based on the 2017 EULAR/ACR classification tree.
• For patients without pathognomonic skin manifestations, DM was defined according to muscle biopsy.
• Patients with amyopathic DM were grouped with DM patients.
• Calcinosis diagnosis was based on clinical examination findings.

Exclusion Criteria:

• Patients whose age at disease onset was <18 years and those with overlap syndrome and/or IBM were excluded.