Skeletal muscle mass deficiency and quality degradation constitute sarcopenia for elderly people. Sarcopenia can result in musculoskeletal damage and accompany various metabolic problems, which make early sarcopenia diagnosis important. Various modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), have been developed for screening sarcopenia. Recently, ultrasound scanning was suggested for screening sarcopenia because of its safety, usability, and cost effectiveness. However, there has been no standardized assessment methodology for screening sarcopenia with ultrasound scanning. Therefore, prior to this study, we developed a four-degrees-of-freedom (DOF) sarcopenia detection system using an RGB-D camera and an ultrasound probe to automatically scan the human thigh without operator dependency. However, due to the eye-to-hand approach with the RGB-D camera, the system has limited usability for clinical trials. Therefore, in this study we modified the system such that it became eye-in-hand by attaching the RGB-D camera to the upper part of the system with an enhanced arc fitting algorithm. The modified system and enhanced algorithm were verified by an in-vitro test with bean curd-gelatin phantom. The results showed that the thickness of bean curd in the gelatin phantom was maintained at approximately 12.7 ± 0.35 mm over the 71.5∘ scanning range with 2.49 ± 0.15 N radial force at various thickness measuring points.