Abstract
Abstract Nuclear medicine image can achieve the ultra-high resolution level through the design of detector and pinhole collimator. According to desired resolution and center field of view (CFOV), micro-SPECT is supplied with a lot of specification of collimators. Although adequate collimator allows micro-SPECT fully demonstrated its performance, it often needs high cost. On the other hand, dual tracer imaging with SPECT/PET imaging has active developed in recent years. The procedure is to inject dual tracer (ex: 99mTc and 18F) in body and perform SPECT and PET imaging simultaneously. The process is called “Dual Isotope Simultaneous Acquisition, DISA”. DISA has great advantage in both pre-clinical and clinical applications, it can evaluate the functional imaging of different tracers under identical condition, increase physiological assessment accuracy and reduce errors of separate scans. However, DISA would produce cross-talk scatter contamination to degrade the image quality. As a result, a robust cross-talk scatter correction is essential for classical DISA imaging with SPECT/PET. This study propose a novel Beam Stopper (BS) imaging technique based on PET scanner that enables SPECT/PET dual modality imaging. Instead of the insert of pinhole collimator inside SPECT, the BS insert inside PET scanner can achieve SPECT and PET imaging without the contamination of cross-talk scatter. BS device can be regarded as the opposite of pinhole collimator system, it uses high attenuated material to replace the part of pinhole aperture and remove the other part of pinhole collimator. Using the difference between complete projection data (scan w/o BS) and the BS-scanning projection data, we can obtain a projection data similar to the pinhole imaging. This BS device consisted of four tungsten BS rod with 0.8 mm diameter and forty one discs septa with 0.5-mm-thickness. BS device inserted into Inveon preclinical PET system can acquired full SPECT projection data sets via rotations of BS device, while obtaining PET images with normal PET acquisitions. The feasibility of the study is validated with extensive Monte Carlo simulations. The experiment is divided into two steps. In the first step, we evaluate the performance of BS-SPECT system. Next, we put the BS device inside Inveon preclinical PET to assess the feasibility of dual tracer imaging using BS technique. For BS-SPECT studies, high resolution (~1.2mm), uniformity (CV=6.49%) and 152.85 cps/Bq∙cm2 of volume sensitivity were obtained. For contrast phantom studies, CRC in hot area and cold area can achieve 94.90% and 90.35%, respectively. For DISA studies, the cross-talk scatters can be removed naturally during the subtraction of the sinograms with and w/o BS. SPECT/PET dual modality imaging can maintain the same image quality compared with single modality scan. This study has proposed a novel beam stopper imaging technique that opens the new way for high resolution molecular imaging. Comparing to other micro SPECT, BS has the advantages of low cost and more flexibility and enable the SPECT/PET dual modality imaging while eliminating the cross-talk scatter contaminations.