Second generation of linear array photoacoustic imaging for melanoma thickness measurement

Skin diseases represent a significant public health concern, underscoring the importance of early and accurate diagnosis to enhance patient outcomes. In response to the need for reducing patient discomfort and complications associated with diagnostic procedures, non-invasive techniques have been developed. These methodologies eliminate the necessity for surgical interventions and tissue sampling. Among these techniques is ultrasound imaging, which enables the visualization of skin structures and their respective layers, thereby providing critical anatomical information without the need for invasive procedures. Additionally, photoacoustic imaging is a noteworthy noninvasive modality that employs light to generate ultrasound waves within the tissue. This approach facilitates the collection of functional information based on the absorption characteristics of the tissue, including the distribution of vasculature. This study introduces a novel photoacoustic ultrasound probe for high-resolution skin imaging, focusing on accurate melanoma thickness measurement. The probe features a compact linear array transducer with 256 elements operating at 44MHz. It employs a coaxial illumination system using a thin chromium film and thin film mirror within a gelatin block attached to the transducer by a 3D holder. This setup efficiently transmits ultrasound waves and reflects light, optimizing tissue illumination and reducing out-of-plane artifacts. In addition, a synthetic aperture focusing technique was implemented to improve the image quality during reconstruction. This compact, handheld probe integrates ultrasound and photoacoustic imaging, offering significant advancements in melanoma visualization and thickness measurement for improved diagnosis and treatment planning.