In-vivo results for rheumatoid arthritis diagnosis with a 360° pulse-echo imaging system

Progress in medical ultrasound in recent years makes sonography a valuable method for early rheumatoid arthritis (RA) diagnosis today. However, detecting in ammatory processes in periarticular bones requires expert knowledge and training. 360° compound imaging has already proven to increase ultrasound B-mode image quality significantly, e.g. in breast cancer imaging. Therefore an existing Ultrasound Computed Tomography (USCT) system has been modified for RA diagnosis, with respect to finger joint imaging. Well known concepts in USCT to reconstruct the speed of sound (SOS) distribution can not be applied, as the bone inhibits transmission measurements of fingers. Therefore, an image based local contrast quantification method is proposed to estimate a mean SOS for the soft tissue surrounding the finger joint. Based on this estimation, ultrasound B-mode images can be corrected for refraction and TOF to yield high image quality in 360° compound imaging. This method has been validated by measurements on tissue mimicking phantoms. Healthy volunteers and RA patients have been examined with the USCT system. In-vivo results show a great potential for 360° compound imaging to visualize synovitis as well as bone erosion in RA of finger joints.