Imaging and Analysis of P(L/D)LA 96/4 Joint Scaffold Using Computed Tomography

The architecture of tissue engineering scaffold has a strong effect on its functionality. The micro-computed tomography (?-CT) is a non-destructive X-ray irradiation based imaging method which has been widely used in scaffold characterization. The technique enables accurate visualization of the internal structures and morphology in two- and three-dimensions. In addition, image data can be used to calculate numerical values for several structural parameters including porosity and pores sizes. In the present study, the structure of five different types of joint scaffolds was studied using two different CT types. Studied scaffolds are designed for small joint (metacarpophalangeal joint) reconstruction. Imaging was performed using Planmeca ProMax 3Ds cone-beam computed tomography (CBCT) and high resolution SkyScan-1072 desktop fan-beam micro-CT. The main purpose of the study was to assess the suitability of Planmeca CBCT for structural characterization and for quality control of porous scaffolds. Main studied scaffold type was P(L/D)LA 96/4 joint scaffold. Motivation for this study comes from the specific properties of Planmeca CBCT which overcome the general limitations of micro-CT. The device is originally designed for dental imaging allowing fast image acquisition and has also a large measuring field which enables imaging the entire implant structure with a single scan. First goal in the present study was to find out the highest image quality which can be achieved with Planmeca device. In practice, different CT imaging parameters were tested and some of the samples were modified with different contrast enhancement techniques before imaging. The quality of obtained images was visually evaluated and the best images were selected for structural parameter determination. A SkyScan micro-CT was used in a comparative study in order to estimate the reliability of Planmeca CBCT study and to compare the suitability of these two devices for scaffold characterization. The spatial resolution of the SkyScan micro-CT was beforehand known to be significantly better than in Planmeca CBCT. Sample modification studies proved that it is very challenging to improve image contrast and use contrast enhancement techniques non-destructively without causing any structural changes to the scaffold. Without using any contrast enhancement, the CBCT image quality was good enough to apply them for image analysis and determine porosity degree and porosity degree distribution of scaffolds. Also glass content of two types of scaffolds was calculated successfully. Pore sizes (pore diameter) could not be calculated due to complex scaffold architecture and lack of sophisticated image analysis program but total pore volume distribution was determined instead. Quality of Planmeca CBCT images was not the best possible due to still poor accuracy and contrast even though the imaging parameters were optimized carefully. Planmeca CBCT characterization cannot be considered reliable because images did not give realistic overview of the scaffold fibrous structure, unlike the micro-CT images did. The use of Planmeca CBCT in the quality control would still be possible but that would require standardization of the CT imaging parameters and image analysis parameters. Parameter standardization would allow comparing the mutual differences in architectures of parallel samples. /Kir1