D.P.23 3D imaging of internal structures of skeletal muscle with an ultrathin side-viewing optical needle probe

Evaluation of degradation in the structure of skeletal muscle is important for the assessment or diagnosis of many myopathies, such as Duchenne muscular dystrophy. Histological analysis is the gold standard to evaluate such degradation but requires excision and fixation of the tissue. This is undesirably invasive in patients and precludes longitudinal study of disease progression in patients or animal models. Optical coherence tomography (OCT) is a high-resolution (∼10 μm) imaging modality capable of visualising muscle structure and the morphological changes in muscular dystrophy. However, because of the limited image penetration of OCT (∼2 mm), previous studies have been restricted to imaging only superficial tissue. To overcome this limitation, we have developed a miniaturised OCT probe, in which the distal focusing optics are encased within a 30-gauge hypodermic needle and inserted deep within tissue. By rotating and translating the OCT needle probe, it is possible to acquire a 3D image volume of the internal structure of skeletal muscle. This is the smallest published OCT needle probe (outer diameter 310 μm) capable of acquiring a 3D image volume. We have tested this probe with ex vivo murine muscle tissue. We demonstrate the use of this probe with ex vivo murine muscle tissue (Tibialis anterior from 12-week-old male mouse). The acquired multiple 3D image volumes allow visualisation of individual myofibers. Structures such as fascicles, tendon and connective tissue were also detected within the muscle sample. Such miniaturised imaging probes have the potential to extend high resolution optical imaging techniques to in vivo imaging of muscle.