A method for small-animal PET/CT alignment calibration

Abstract

Small-animal positron-emission tomography/computed tomography (PET/ CT) scanners provide anatomical and molecular imaging, which enables the joint visualization and analysis of both types of data. A proper alignment calibration procedure is essential for small-animal imaging since resolution is much higher than that in human devices. This work presents an alignment phantom and two different calibration methods that provide a reliable and repeatable measurement of the spatial geometrical alignment between the PET and the CT subsystems of a hybrid scanner. The phantom can be built using laboratory materials, and it is meant to estimate the rigid spatial transformation that aligns both modalities. It consists of three glass capillaries filled with a positron-emitter solution and positioned in a non-coplanar triangular geometry inside the system field of view. The calibration methods proposed are both based on automatic line detection, but with different approaches to calculate the transformation of the lines between both modalities. Our results show an average accuracy of the alignment estimation of 0.39 mm over the whole field of view.

Combination of Single-Photon Emission Computed Tomography and Magnetic Resonance Imaging to Track 111In-Oxine–Labeled Human Mesenchymal Stem Cells in Neuroblastoma-Bearing Mice

“…The spatial rigid transformation to align MRI to SPECT images 21 was obtained by segmenting the capillaries, adjusting each capillary to a line, and matching the corresponding fiducials of both modalities following a method proposed by Pascau and colleagues, 28 which was based on minimizing the distance between corresponding segments of lines.…”

Performance evaluation of a rotatory dual-head PET system with 90̂increments for small animal imaging

“…For such a rotatory system, high precise geometry alignment is crucial for high spatial resolution. Methods for estimating geometrical parameters of CT and SPECT systems have been investigated by many researchers [20][21][22][23], but these are not the suitable for dual-head PET scanners. In our prototype system, the geometry offset along the z axis, namely the rotation axis, can be eliminated by a highly precise installation, while the geometry offset along the x and y axes, namely the offset between the center of field of view (FOV) and that of the rotation, was difficult to eliminate completely.…”

Automatic self-alignment and registration for PET/CT reconstruction by a cross-correlation maximization method

“…2) The alignment of the PET/CT gantry after calibrations and adjustments through the assembly and onsite installation will be verified and re-calibrated using special designed calibration tools or phantoms and softwares [1][2] [3]. Those phantoms consist of simple objects, such as the points or lines, as fiducial marks that can be seen in both PET and CT images.…”