This paper presents a compact 122 GHz Terahertz FMCW radar using a plastic hollow-core dielectric waveguide for non-destructive testing. The guided approach simplifies the system, avoiding complex free-space optics and alignment, while improving signal-to-noise ratio by isolating endpoint reflections from internal ones. Various configurations, including solid immersion lenses, enhance spatial resolution and imaging capabilities. Experiments combine 3D electromagnetic simulations and raster-scanning to image fine details and detect subsurface defects. Applications span aerospace, automotive, and art conservation. Results demonstrate guided FMCW radar as a cost-effective, portable, and reliable alternative to traditional free-space setups, enabling broader, practical implementation across industries.