Tomographic x-ray–guided three-dimensional diffuse optical tomography of osteoarthritis in the finger joints

Abstract

We describe a multimodality imaging approach that combines x-ray tomosynthesis with near-infrared diffuse optical tomography (DOT) for high-resolution imaging of osteoarthritis in the finger joints. In this approach, we take advantage of high resolution x-ray imaging particularly of the bones and incorporate the fine structural maps obtained from x ray as a priori information into DOT reconstructions. To realize this multi-modality approach, we constructed a hybrid imaging platform that integrated a C-arm-based x-ray tomosynthetic system with a multichannel optic-fiber-based DOT system. We also implemented improved hybrid regularization-based reconstruction algorithms that have shown to be especially effective for high-resolution modality-guided DOT. Initial evaluation of our x-ray-guided DOT reconstruction approach in the finger joints shows that spatial resolution of DOT can be enhanced dramatically when the three-dimensional geometry of bones is known a priori. In particular, the improved quantitative capability of imaging absorption and scattering coefficients of the joint tissues allows for more accurate diagnosis of osteoarthritis over x-ray radiography or DOT alone.

Comparison of diffusion approximation and higher order diffusion equations for optical tomography of osteoarthritis

“…The relatively coarse mesh density generated inside the bone domain has no significant influence on our reconstruction accuracy, which has been demonstrated and validated by our previous simulation tests and phantom experiments. 8,18,21,28 As such, the mesh size used is good enough for diffuse optical imaging that only has a resolution limit of 2 to 3 mm. For the imaging systems, 64 sources and 64 detectors were distributed uniformly along the surface of the phantom at four planes ͑z = 2.5, z = 7.5, z = 12.5, and z = 17.5 mm; 16 sources and 16 detectors at each plane͒.…”

“…Both phantom and in-vivo data were collected using our homemade 64 ϫ 64-channel photodiodes-based stand-alone DOT system or the hybrid x-ray/DOT imaging system that integrates a modified mini-C-arm x-ray system with the 64 ϫ 64-channel DOT system, which were all detailed elsewhere. 8,22,28 This DOT system consists of several laser modules, a hybrid light delivery subsystem, a fiber optics/ tissue interface, a data acquisition module, and light detection modules. 22 The cylindrical fiber optics/tissue interface is composed of 64 source and 64 detector fiber bundles that are positioned in four layers along the surface of a plexiglass container and cover a volume of 15 ͑height͒ by 30 mm ͑di-ameter͒.…”

“…We found from our previous investigations that the improved quantitative capability of imaging absorption and scattering coefficients of the joint tissues allows for more accurate diagnosis of osteoarthritis over the DA-based DOT alone. 28 When anatomical a-priori information becomes available, we would like to study if a more accurate modeling of photon migration in tissue can bring in enhanced accuracy for image reconstruction in the finger joints.…”

“…8 In addition, we evaluate the performance of the HD model using an x-ray/DOT combined multimodality approach. 28 The idea of this multimodality approach is to incorporate the high resolution x-ray images of joint tissues into the DOT reconstruction so that both the resolution and accuracy of optical image reconstruction are enhanced. We found from our previous investigations that the improved quantitative capability of imaging absorption and scattering coefficients of the joint tissues allows for more accurate diagnosis of osteoarthritis over the DA-based DOT alone.…”

Quantitative fluorescence tomography using a trimodality system: in vivo validation

“…In most cases, the XCT and FT images are acquired in separate settings. Then XCT anatomical information is coregistered and used to aid visualization of fluorophores or to improve the quantitative accuracy of FT. 9,11,15 On the other hand, an alternative approach is to build integrated systems to acquire both FT and anatomical images in the same setting. 12,16 Accurate coregistration of optical and anatomical images is the key advantage of this approach.…”