Abstract
.For early diagnosis of rheumatoid arthritis (RA), it is important to visualize its potential marker, vascularization in the synovial membrane of the finger joints. Photoacoustic (PA) imaging, which can image blood vessels at high contrast and resolution, is expected to be a potential modality for earlier diagnosis of RA. In previous studies of PA finger imaging, different acoustic schemes, such as linear-shaped arrays, have been utilized, but these have limited detection views, rendering inaccurate reconstruction, and most of them require rotational detection. We are developing a PA system for finger vascular imaging using a ring-shaped array ultrasound (US) transducer. By designing the ring-array sensor based on simulations, using phantom experiments, it was demonstrated that we have created a system that can image small objects around 0.1 to 0.5 mm in diameter. The full width at half maximum of the slice direction of the system was within 2 mm and corresponded to that of the simulation. Moreover, we could clearly visualize healthy index finger vasculature and the location of the distal interphalangeal and proximal interphalangeal joints by PA and US echo images. In the future, this system could be used as a method for visualizing the three-dimensional vascularization of RA patients’ fingers.
Highlights
Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that causes progressive articular and extra-articular destruction
The 2010 American College of Rheumatology/European League Against Rheumatism criteria are being applied as a means to diagnose RA,[1,2] it remains quite difficult to identify the disease during the very early stage, which results in patients developing more severe symptoms
For imaging RA diagnosis, it has been reported that inflammation of the synovial membrane in the joint, known as synovitis, is associated with vascularization that results in increasing the thickness of the synovial membrane and hypoxia, which can be effective RA markers.[5,6,7]
Summary
Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that causes progressive articular and extra-articular destruction. The improvement of imaging techniques, which are a secondary part of the diagnosis, is needed to overcome these difficulties.[4] Recently, for imaging RA diagnosis, it has been reported that inflammation of the synovial membrane in the joint, known as synovitis, is associated with vascularization that results in increasing the thickness of the synovial membrane and hypoxia, which can be effective RA markers.[5,6,7] During its early stages, RA often appears in the finger joints.[8] The imaging devices mainly used in clinical practice are conventional radiography (CR), magnetic resonance imaging (MRI), and Doppler ultrasound (US).[9] CR is sensitive to changes in joint spaces and bone erosion and is mainly applied during a later stage. Doppler US is widely used for assessing the vascularity of an inflamed synovium, but it is dependent on observational techniques and is difficult to quantify.[4]
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