Performance characterization of the Inveon preclinical small-animal PET/SPECT/CT system for multimodality imaging

Abstract

3Purpose: We analyzed the performance of the Inveon for an integrated small-animal PET/SPECT/CT system and compared the imaging capabilities of the SPECT and the PET components.Methods: For SPECT, energy resolution, tomographic spatial resolution, and system sensitivity were evaluated with 99m Tc solution using a single pinhole collimator. For PET, spatial resolution, absolute sensitivity, scatter fraction, and peak noise equivalent count (NEC) were evaluated. A micro-Derenzo phantom, cylindrical phantom, and National Electrical Manufacturers Association NU-4 image quality phantom were scanned to compare SPECT and PET image capabilities, and SPECT and PET bone imaging were performed on a normal rat in vivo.Results: SPECT spatial resolution was 0.84 mm full width at half maximum (FWHM) at a radius of rotation of 25 mm using the 0.5-mm pinhole aperture collimator, while PET spatial resolution was 1.63 mm FWHM at the center. SPECT system sensitivity at a radius of rotation of 25 mm was 35.3 cps/MBq (4 × 10 -3 %) using 0.5-mm pinhole aperture, while PET absolute sensitivity was 3.2% for 350-650 keV and 3.432 ns. Accordingly, the volume sensitivity of PET was three orders of magnitude 4 higher than that of SPECT.Conclusions: This integrated PET/SPECT/CT system provided high system performance with excellent spatial resolution for SPECT and sensitivity for PET.Based on tracer availability and system performance, SPECT and PET have complementary roles for multi-modality small-animal imaging.Key Words: integrated PET/SPECT/CT system; small-animal imaging; performance measurement; instrumentation; molecular imaging 5 INTRODUCTIONMolecular imaging of small laboratory animals using single photon emission tomography (SPECT), positron emission tomography (PET), and x-ray computed tomography (CT) has recently emerged as an important tool for the in vivo study of animal models of human disease. This imaging method enables longitudinal studies to be performed in the same animal, and animals can serve as their own control.SPECT and PET have been used in functional imaging, including brain, heart, gene expression, and oncology studies [1,2]. CT has also been used for anatomical imaging (e.g., bone imaging) because it provides high contrast between bone and soft tissue [3]. The use of SPECT, PET, and CT in combinations such as SPECT/CT, PET/CT, SPECT/PET, and SPECT/PET/CT-so-called "multi-modality imaging"-may enable the development of new and interesting protocols for investigating many biological phenomena more effectively than is possible using SPECT, PET, or CT modalities alone. Using these techniques, lesions visualized by functional imaging can be correlated with anatomic imaging. In general, CT is also used for attenuation and scatter correction of SPECT and PET images. However, in this 6 study, neither attenuation nor scatter correction was performed.Integration of SPECT, PET, and CT images can be achieved by a "software approach" that fuses the images acquired by separate scanners. These techniques, however, are hamper...

Appropriate collimators in a small animal SPECT scanner with CZT detector

“…On SPECT imaging, sensitivity with MPH was about 5-fold higher than that with SPH, while PAH yielded about 21-fold higher sensitivity than SPH. The sensitivity was lower than with other scanners with NaI detector [10,12,14,15,17].…”

“…These results are important because the sensitivity has not previously been reported on the SPECT scanner with CZT detector. In other scanners, the sensitivity of planar imaging using the Inveon SPECT scanner with NaI detector (Siemens Medical Solutions, TN, USA) was about 35 cps/MBq with SPH [12].…”

“…In other scanners, SPH provided 0.6-1.4 mm FWHM with NaI detector [12][13][14][15] [6,8]. PAH yielded about 8 mm FWHM with NaI detector [13].…”

“…Planar and SPECT projection data are acquired using various collimators in clinical settings. Almost all small-animal SPECT is performed with pinhole collimators (PH), including single-PH (SPH) [8,[12][13][14][15][16][17] and multi-PH (MPH) [6,[8][9][10]15], as these collimators will provide good resolution for small objects when compared with parallel hole collimators (PAH), which are more commonly used in clinical settings [20]. Although we have to select appropriate collimator to obtain high-quality images and accurate analysis results, there have been no comparative studies on image quality with various collimators in small animal imaging.…”

“…In current SPECT scanners, cadmium zinc telluride (CZT) semiconductor detectors have been applied to improve energy and spatial resolution [4][5][6][7][8], as compared with sodium iodide (NaI) scintillation detectors, which were used in conventional SPECT scanners [9][10][11][12][13][14][15][16][17][18][19]. Planar and SPECT projection data are acquired using various collimators in clinical settings.…”