Initial Evaluation of Three Novel Quantiative Imaging Utilities from a Newly Developed SPECT Camera in China

Objectives: A general purpose flexible angle dual head SPECT camera, ImaginE NET 632, was developed by Beijing Novel Medical Equipment Ltd and has been recently approved by China Food and Drug Administration (CFDA) for sale in China. The objective of this study was to evaluate three novel quantitative imaging utilities of this camera for bone,kidney and myocardium respectively.

Methods: The first utility is quantitative bone tomography for a certain axial region of interest (ROI) based on two-view whole body gamma scintigraphy and diagnostic CT images of the same ROI but from a separate scanner. The quantitative bone tomography was achieved by the following steps: first segmented 3D bone structures from CT images automatically, then registered the 3D CT bone segmentations with axial ROIs of whole body gamma planar images by iterative 3D transformation,3D to 2D projection and 2D registration, finally reconstructed gamma bone tomography with CT-based attenuation correction from the two-view gamma projection image ROI by incorporating the CT bone segmentations as prior information. Two patients were studied and the resulted tomography images were compared with the images from conventional SPECT scans. The second utility is quantitative renography featured by patient specific image-based estimation of the kidney depth for attenuation correction to improve the quantitation accuracy. The quantitative renography was achieved through a novel data acquisition procedure and subsequent data processing methods. For data acquisition, we employed the flexible angle option of ImaginE NET 632 SPECT which performed simultaneous dynamic renal imaging with the detector below staying stationary and tomosynthesis of kidneys with the detector above rotating while acquiring projections. For data processing, centroids of kidneys are estimated by segmentation and least square fit of the tomosynthetic data and then applied for kidney depth calculation and attenuation correction in renography. Three patients were studied and the gamma image-based estimations of kidney depths were compared with those from Tonnessen formula(i.e. based on patient’s height and weight) employing CT or MR image-based estimations as golden standard. The third utility is quantitative dynamic myocardium SPECT imaging achieved by V-mode acquisition of dual detector head. Equipped with a pair of multi-pinhole collimators of 24 pinholes in total, two SPECT detector span 180 degrees of sampling angle range on a 18cm-diameter spherical common field of view(CFOV). Phantom studies demonstrated 7mm spatial resolution and 0.06% sensitivity were achieved for the center of CFOV. Four patients were studied and compared with conventional SPECT with parallel-hole collimators and two dedicated cardiac SPECT cameras. Results: In the study of novel quantitative bone tomography, improved image resolution and enhanced detailed features were observed compared with the conventional bone SPECT images. These differences were mainly attributed to the CT prior information,smaller bin size and better statistics of the whole body planar image data compared with the SPECT projection data. In the study of quantitative renography, <6% error was achieved in the kidney depth estimation with the tomosynthesis method compared with >15% error with conventional Tonnessen formula. In the study of quantitative dynamic cardiac SPECT imaging, similar degree of improved defect detection and reduced variation of functional myocardium were observed for ImaginE NET 632 SPECT with dedicated multi-pinhole collimators and two other dedicated cardiac SPECT, compared with the parallel-hole SPECT. Conclusion: The ImaginE NET 632 SPECT camera with three novel imaging utilities has great potential to improve the corresponding bone, kidney and cardiac study applications. Systematic patient studies need to be carried out to further evaluate the utilities and optimize the clinical protocols.

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