Development of a platform for co-registered ultrasound and MR contrast imagingin vivo

Abstract

Imaging of the microvasculature is often performed using contrast agents in combination with either ultrasound (US) or magnetic resonance (MR) imaging. Contrast agents are used to enhance medical imaging by highlighting microvascular properties and function. Dynamic signal changes arising from the passage of contrast agents through the microvasculature can be used to characterize different pathologies; however, comparisons across modalities are difficult due to differences in the interactions of contrast agents with the microvasculature. Better knowledge of the relationship of contrast enhancement patterns with both modalities could enable better characterization of tissue microvasculature. We developed a co-registration platform for multi-modal US and MR imaging using clinical imaging systems in order to study the relationship between US and MR contrast enhancement. A preliminary validation study was performed in phantoms to determine the registration accuracy of the platform. In phantoms, the in-plane registration accuracy was measured to be 0.2 ± 0.2 and 0.3 ± 0.2 mm, in the lateral and axial directions, respectively. The out-of-plane registration accuracy was estimated to be 0.5 mm ±0.1. Co-registered US and MR imaging was performed in a rabbit model to evaluate contrast kinetics in different tissue types after bolus injections of US and MR contrast agents. The arrival time of the contrast agent in the plane of imaging was relatively similar for both modalities. We studied three different tissue types: muscle, large vessels and fat. In US, the temporal kinetics of signal enhancement were not strongly dependent on tissue type. In MR, however, due to the different amounts of agent extravasation in each tissue type, tissue-specific contrast kinetics were observed. This study demonstrates the feasibility of performing in vivo co-registered contrast US and MR imaging to study the relationships of the enhancement patterns with each modality.

Novel registration for microcomputed tomography and bioluminescence imaging based on iterated optimal projection

“…From the figure, we could also find that the registration deviation of our method was less than the registration deviation of Beattie's and Chandrana's methods. 10,11 With these experiments, we found that the average registration deviation using the registration method based on the marked Table 1 The registration results of three mice using the two registration methods. Note: IOP stands for the registration results of three mice using our registration methods based on the iterated optimal projection; MP stands for the registration results of three mice using the registration algorithm based on the marked points.…”

“…All of these results showed that our registration method was more stable than the registration method based on the marked points. 10,11 Furthermore, the bioluminescence distribution derived from the four-orientation 2-D images was mapped onto the 3-D surface of the mouse derived from the Micro-CT image using our registration method based on the iterated optimal projection. The 3-D bioluminescence distribution of transgenic mouse 1 after mapping based on the registration results using our registration method is shown in Fig.…”

“…8. Since the two figures were not easily distinguishable with the naked eye, the reconstruction results based on the registration results using Beattie's and Chandrana's methods 10,11 are not shown in this paper. Here, the bioluminescent source whose intensity was less than half of the highest intensity of the bioluminescent source is not shown in the figure.…”

“…Note: ED1 (error distance 1) stands for the error distance between the reconstructed center of the reconstructed element and the real center of the real element of mouse 1 using the FEM method based on our registration results; ED2 (error distance 2) stands for the error distance between the reconstructed center of the reconstructed element and the real center of the real element of mouse 1 using the FEM method based on Beattie's and Chandrana's methods. 10,11 and bioluminescence calibration, the permissible source region (PS) was set to PS ¼ ½ðx; y; zÞj14 < x < 40; 8 < y < 28; 62 < z < 72; ðx; y; zÞ ∈ Ω:…”

“…10 Chandrana's method provided a platform for coregistered ultrasound and MR contrast imaging in vivo. 11 Klose and his partners reconstructed the source distribution from coregistered CT and MR images and showed the performance of the coregistration method. 12 Beattie's group provided a multimodality registration method without a dedicated multimodality scanner.…”