Atlas-driven scan planning for high-resolution micro-SPECT data acquisition based on multi-view photographs: a pilot study

Abstract

Highly focused Micro-SPECT scanners enable the acquisition of functional small animal data with very high-resolution. To acquire a maximum of emitted photons from a specific structure of interest and at the same time minimize the required acquisition time, typically only a small subvolume of the animal is scanned that contains the organs of interest. This Volume of Interest (VOI) can be defined manually based on photographs of the animal taken prior to SPECT scanning, for example two lateral views and a top view. In these photographs however, only the surface of the animal is visible and therefore visual estimation of the location of these organs may be difficult.In this paper, we propose a novel atlas-based technique for estimating the organ VOI for the major organs by mapping a small animal atlas to optical scout images. The user is required to outline the animal contour in one lateral view, and to mark two lateral landmarks in the top view photograph. These landmarks subsequently serve as fiducial landmarks to define a 3D Thin-Plate-Spline mapping of an anatomical mouse atlas to the photographic coordinate space. Planar projections of the mapped atlas organs on the photographs greatly facilitate the estimation of the size and position of the target organ. To validate the proposed approach, the estimated organ VOIs were compared to manually drawn organ outlines in a Micro-CT scan, which was co-registered to the scout photographs using physical landmarks. The results demonstrate a highly promising volume correspondence between the real and the estimated organ VOIs.

Mouse Atlas Registration with Non-tomographic Imaging Modalities—a Pilot Study Based on Simulation

“…This result is slightly different from a real-world photo which is a gray-scale or RGB-color picture of the mouse body. For a real-world photo, an additional segmentation step would be required to extract the body silhouette, as in [1] and [13]. …”

“…b T =1 indicates the inclusion of a top-view 2D image, b T =0 indicates exclusion of the top-view 2D image, and so forth for b S and b L . For example, the combination of “C0+C90” has the b value of [1, 1, 0], and the combination of “X0+C90+L” has the b value of [1, 1, 1]. The deformations of different modalities are combined into one 3D global deformation according to…”

“…Some molecular imaging modalities also need complimentary anatomical information to help with image acquisition, reconstruction, and analysis, such as micro-single photon emission computed tomography (micro-SPECT) scan planning [1], optical tomography reconstruction [2–5], micro-positron emission tomography (micro-PET) attenuation correction [6], and tissue uptake quantification [7]. Currently, in vivo imaging of the mouse anatomy can be achieved with small animal tomographic imaging modalities such as micro-computed tomography (micro-CT) [8] and micro-magnetic resonance imaging (micro-MR) [9].…”

“…Baiker et al . registered the mouse atlas to optical profiles of the mouse body to assist scan planning of region-focused micro-SPECT [1]. Khmelinskii et al .…”

Estimation of Mouse Organ Locations Through Registration of a Statistical Mouse Atlas With Micro-CT Images

“…Most of these methods use high-contrast anatomical features (such as the body profile, skin, skeleton, and lungs) to register the atlas to individual subjects. Some studies acquire 2D silhouettes of the mouse body with optical cameras, and use these silhouettes to guide the atlas registration [12] or body surface alignment [13]. Other than 2D silhouettes, 3D body surface geometries are also acquired for atlas registration.…”