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Spheroids have emerged as in vitro models that reproduce in a great extent the architectural microenvironment found in human tissues. However, the imaging of 3D cell cultures is highly challenging due to its high thickness, which results in a light-scattering phenomenon that limits light penetration. Therefore, several optical clearing methods, widely used in the imaging of animal tissues, have been recently explored to render spheroids with enhanced transparency. These methods are aimed to homogenize the microtissue refractive index (RI) and can be grouped into four different categories, namely (a) simple immersion in an aqueous solution with high RI; (b) delipidation and dehydration followed by RI matching; (c) delipidation and hyperhydration followed by RI matching; and (d) hydrogel embedding followed by delipidation and RI matching. In this review, the main optical clearing methods, their mechanism of action, advantages, and disadvantages are described. Furthermore, the practical examples of the optical clearing methods application for the imaging of 3D spheroids are highlighted., (© 2019 Wiley Periodicals, Inc.)

Background: Selective laser sintering (SLS), three-dimensional printing (3DP) and PolyJet are rapid prototyping (RP) techniques to fabricate prototypes from virtual biomedical images. To be used in maxillofacial surgery, these models must accurately reproduce the craniofacial skeleton., Purpose: To analyze the capacity of SLS, 3DP and PolyJet models to reproduce mandibular anatomy and their dimensional error., Material: Dry mandible, helical CT images, SLS, 3DP and PolyJet prototypes, and digital electronic caliper., Methods: Helical CT images were acquired from a dry mandible (criterion standard) and manipulated with the InVesalius software. Prototypes were produced using SLS, 3DP and PolyJet techniques. Thirteen linear measurements of each prototype were made and compared with the dry mandible measurements., Results: The results showed a dimensional error of 1.79%, 3.14% and 2.14% for SLS, 3DP and PolyJet models, respectively. The models satisfactorily reproduced anatomic details and the SLS and PolyJet prototypes showed greater dimensional precision and reproduced mandibular anatomy more accurately than the 3DP model., Conclusions: The SLS prototype had a greater dimensional accuracy than the PolyJet and 3DP models. The PolyJet technique reproduced anatomic details of the mandible more accurately.

Background: Selective laser sintering (SLS) and three-dimensional printing (3DPtrade mark) are rapid prototyping (RP) techniques to fabricate prototypes from biomedical images. To be used in maxillofacial surgery, these models must accurately reproduce the craniofacial skeleton., Purpose: To analyze the capacity of SLS and 3DPtrade mark models to reproduce craniomaxillary anatomy and their dimensional error., Material: Dry skull, helical computed-tomography images, SLS and 3DPtrade mark prototypes, and electronic calliper., Methods: Tomographic images of a dry skull were manipulated with the InVesalius biomedical software. Prototypes were fabricated using SLS and 3DPtrade mark techniques. Ten linear measurements were made on the models and compared with corresponding dry skull measurements (criterion standard) carried out with an electronic calliper., Results: We observed a dimensional error of 2.10 and 2.67% for SLS and 3DPtrade mark models, respectively. The models satisfactorily reproduced anatomic details, except for thin bones, small foramina and acute bone projections. The SLS prototypes showed greater dimensional precision and reproduced craniomaxillary anatomy more accurately than the 3DPtrade mark models., Conclusion: Both SLS and 3DPtrade mark models provided acceptable precision and may be useful aids in most maxillofacial surgeries.