High SPECT Research Articles

Image synthesis of interictal SPECT from MRI and PET using machine learning.

Cross-modality image estimation can be performed using generative adversarial networks (GANs). To date, SPECT image estimation from another medical imaging modality using this technique has not been considered. We evaluate the estimation of SPECT from MRI and PET, and additionally assess the necessity for cross-modality image registration for GAN training. We estimated interictal SPECT from PET and MRI as a single-channel input, and as a multi-channel input to the GAN. We collected data from 48 individuals with epilepsy and converted them to 3D isotropic images for consistence across the modalities. Training and testing data were prepared in native and template spaces. The Pix2pix framework within the GAN network was adopted. We evaluated the addition of the structural similarity index metric to the loss function in the GAN implementation. Root-mean-square error, structural similarity index, and peak signal-to-noise ratio were used to assess how well SPECT images were able to be synthesised. High quality SPECT images could be synthesised in each case. On average, the use of native space images resulted in a 5.4% percentage improvement in SSIM than the use of images registered to template space. The addition of structural similarity index metric to the GAN loss function did not result in improved synthetic SPECT images. Using PET in either the single channel or dual channel implementation led to the best results, however MRI could produce SPECT images close in quality. Synthesis of SPECT from MRI or PET can potentially reduce the number of scans needed for epilepsy patient evaluation and reduce patient exposure to radiation.

Ultra-fast high resolution whole-body SPECT after treatment with 153Sm-EDTMP using 3D-ring CZT: applying new technology to an old tracer.

Ultra-fast high resolution whole-body SPECT after treatment with 153Sm-EDTMP using 3D-ring CZT: applying new technology to an old tracer.

Ultra high speed SPECT bone imaging enabled by a deep learning enhancement method: a proof of concept

BackgroundTo generate high-quality bone scan SPECT images from only 1/7 scan time SPECT images using deep learning-based enhancement method.Materials and methodsNormal-dose (925–1110 MBq) clinical technetium 99 m-methyl diphosphonate (99mTc-MDP) SPECT/CT images and corresponding SPECT/CT images with 1/7 scan time from 20 adult patients with bone disease and a phantom were collected to develop a lesion-attention weighted U2-Net (Qin et al. in Pattern Recognit 106:107404, 2020), which produces high-quality SPECT images from fast SPECT/CT images. The quality of synthesized SPECT images from different deep learning models was compared using PSNR and SSIM. Clinic evaluation on 5-point Likert scale (5 = excellent) was performed by two experienced nuclear physicians. Average score and Wilcoxon test were constructed to assess the image quality of 1/7 SPECT, DL-enhanced SPECT and the standard SPECT. SUVmax, SUVmean, SSIM and PSNR from each detectable sphere filled with imaging agent were measured and compared for different images.ResultsU2-Net-based model reached the best PSNR (40.8) and SSIM (0.788) performance compared with other advanced deep learning methods. The clinic evaluation showed the quality of the synthesized SPECT images is much higher than that of fast SPECT images (P < 0.05). Compared to the standard SPECT images, enhanced images exhibited the same general image quality (P > 0.999), similar detail of 99mTc-MDP (P = 0.125) and the same diagnostic confidence (P = 0.1875). 4, 5 and 6 spheres could be distinguished on 1/7 SPECT, DL-enhanced SPECT and the standard SPECT, respectively. The DL-enhanced phantom image outperformed 1/7 SPECT in SUVmax, SUVmean, SSIM and PSNR in quantitative assessment.ConclusionsOur proposed method can yield significant image quality improvement in the noise level, details of anatomical structure and SUV accuracy, which enabled applications of ultra fast SPECT bone imaging in real clinic settings.

Scintillation event localization in hemi-ellipsoid detector for SPECT, a simulation study using Geant4 Monte-Carlo

Purpose: a high sensitivity Cardiac SPECT system using curved crystals with pinhole collimation was proposed previously (Dey, IEEE Trans. Nucl. Sci. 59 (2012) 334). Using hemi-ellipsoid CsI crystals, in simulations, the system improved sensitivity by a factor of 3 over newer generation SPECT systems (DSPECT or GE Discovery) while keeping the resolution comparable (Bhusal et al., Med. Phys. 46 (2018) 116). In this work, we hypothesize that the high curvature detector results in measurable differences in light distribution from events at different depths in the crystal. We rigorously test this by analyzing the scintillation light using Monte-Carlo (Geant4) and propose a statistical event localization method in a hemi-ellipsoid detector. We evaluate the localization error of the algorithm and the back-projected errors in object space. Methods: to develop this localization capability for the proposed design, we used Geant4 to simulate the propagation of scintillation light in a monolithic hemi-ellipsoidal CsI crystal. A look-up table (LUT) was created to map the points inside the crystal to the expected light pattern on the crystal surface using the Geant4 simulation data. Thirteen zones were considered across the crystal. In each zone, gamma-rays were simulated and the resulting photon intensity on the surface was captured, serving as our experimental interactions. An algorithm based on Poisson statistics was developed to limit the search of the experimental gamma-ray event locations into smaller regions of the LUT. The localization was fine-tuned by comparing the light distribution of the gamma interactions in selected patterns from the LUT points and then recorded. The algorithm-localized gamma-ray events were also individually back-projected to the object mid-plane, (expected mid-plane of the heart), and the error at the plane was recorded as well. Results: the light patterns of adjacent LUT points showed visually discernible differences. Excluding some outliers (up to 2%), the localized errors averaged over all the zones was 0.71 (±0.44) mm with a worse case of 1.36 (± 0.67) mm at the apex. Moreover, when back-projected to the midplane of the region of interest for Cardiac SPECT, the errors were <1 mm due to the high system magnification afforded by the apex and other zones. The average back-projection error at the mid-plane of the object was 0.4 mm±0.22 mm. Conclusion: we modeled gamma-event interactions and scintillation light spread in CsI hemi-ellipsoid detector and developed a robust statistical algorithm that localized scintillation events to within 0.71 (±0.44) mm on the average within a hemi-ellipsoid CsI detector. Moreover, due to the high system magnification afforded by the crystal, the hemi-ellipsoid unit was capable of achieving <1 mm average localization in the object space, assuming perfect pinhole collimator resolution recovery. Thus, we show that this high sensitivity system will be able to deliver images with high resolution for Cardiac SPECT. In the future, the application of this may be extended to Brain SPECT and small animal imaging.

How to inject ictal SPECT? From manual to automated injection

BackgroundSuccessful surgery depends on the accurate localization of epileptogenic zone before surgery. Ictal SPECT is the only imaging modality that allows identification of the ictal onset zone by measuring the regional cerebral blood flow at the time of injection. The main limitation of ictal SPECT in epilepsy is the complex methodology of the tracer injection during a seizure. To overcome this limitation, we present the main features of the first automated injector for ictal SPECT (epijet, LemerPax; La Chapelle -sur-Erdre; France). In this study we compared traditional manual injection with automated injection for ictal SPECT in 122 patients with drug-resistant epilepsy. MethodsThe study included 55 consecutive prospective patients with drug-resistant epilepsy undergoing injection with the automated injector. The control group was our retrospective database of a historic pool of 67 patients, injected manually from 2014 to 2016. Calculated annual exposure/radioactive dose for operators was measured. Injection time, seizure focus localization with ictal SPECT, as well as repeated hospitalizations related to inconclusive findings of the SPECT were compared in these two groups of patients. ResultsThere were no differences in the average injection time with epijet (13 s) compared with the traditional manual injection (14 s). The seizure focus was successfully localized with ictal SPECT with epijet in 44/55 (80 %) patients and with manual injection in 46/67 (68 %) patients (p = 0.097). Repeated studies were required in 9/67 (23 %) patients in the manual injection group compared to 3 patients (7%) in the epijet group (p = 0.141). Calculated annual exposure/dose for operators of 0.39 mSv/year and administered dose error inferior to 5% are other advantages of epijet. ConclusionThe first results using epijet are promising in adjustment of the injection dose, reducing the rate of radiation exposure for patients and nurses, maintaining the same injection time and allowing high SPECT accuracy. These preliminary results support the use of an automated injection system to inject radioactive ictal SPECT doses in epilepsy units.

Positron range-free and multi-isotope tomography of positron emitters

Despite improvements in small animal PET instruments, many tracers cannot be imaged at sufficiently high resolutions due to positron range, while multi-tracer PET is hampered by the fact that all annihilation photons have equal energies. Here we realize multi-isotope and sub-mm resolution PET of isotopes with several mm positron range by utilizing prompt gamma photons that are commonly neglected. A PET-SPECT-CT scanner (VECTor/CT, MILabs, The Netherlands) equipped with a high-energy cluster-pinhole collimator was used to image 124I and a mix of 124I and 18F in phantoms and mice. In addition to positrons (mean range 3.4 mm) 124I emits large amounts of 603 keV prompt gammas that—aided by excellent energy discrimination of NaI—were selected to reconstruct 124I images that are unaffected by positron range. Photons detected in the 511 keV window were used to reconstruct 18F images. Images were reconstructed iteratively using an energy dependent matrix for each isotope. Correction of 18F images for contamination with 124I annihilation photons was performed by Monte Carlo based range modelling and scaling of the 124I prompt gamma image before subtracting it from the 18F image. Additionally, prompt gamma imaging was tested for 89Zr that emits very high-energy prompts (909 keV). In Derenzo resolution phantoms 0.75 mm rods were clearly discernable for 124I, 89Zr and for simultaneously acquired 124I and 18F imaging. Image quantification in phantoms with reservoirs filled with both 124I and 18F showed excellent separation of isotopes and high quantitative accuracy. Mouse imaging showed uptake of 124I in tiny thyroid parts and simultaneously injected 18F-NaF in bone structures. The ability to obtain PET images at sub-mm resolution both for isotopes with several mm positron range and for multi-isotope PET adds to many other unique capabilities of VECTor’s clustered pinhole imaging, including simultaneous sub-mm PET-SPECT and theranostic high energy SPECT.

Experimental study of SPECT imaging with novel myocardial perfusion imaging tracer: 99Tcm-3SPboroxime

Objective To assess the superiority of 99Tcm-3SPboroxime (99Tcm-3SP for short) as a fast-myocardial perfusion imaging (MPI) tracer in normal and acute myocardial infarction (AMI) mini-swine. Methods 99Tcm-3SP and 99Tcm-Teboroxime (99Tcm-TEBO for short) were prepared. Approximately 370 MBq 99Tcm-3SP or 99Tcm-TEBO was injected intravenously in 2 healthy mini-swine separately. Dynamic planar images were acquired immediately after injection and continued for 20 min using a standard SPECT camera. The radioactivity uptakes in the heart, liver, and lungs were measured, and heart/liver and heart/lung ratios over time were calculated. Dynamic SPECT studies were performed in 4 normal swine and 1 AMI-swine using cadmium zinc telluride-SPECT (CZT-SPECT). List mode acquisitions were immediately started and continued for 15 min after intravenous injection of approximately 370 MBq 99Tcm-TEBO and 99Tcm-3SP. The injection of two radiotracers in the same swine was completed within 2 d. The radioactivity uptakes in heart and liver were measured, and heart/liver ratio was calculated. Image quality was also evaluated. Paired t test was used to analyze the data. Results The radiochemical purity of 99Tcm-TEBO or 99Tcm-3SP were both above 95%. The initial heart uptake of 99Tcm-3SP was very close to that of 99Tcm-TEBO (planar image, 2 min postinjection: 309.32×103vs 314.13×103 counts/MBq; SPECT image, 2 min postinjection (corrected): 7.96±0.87 vs 8.24±1.53, t=0.277, P>0.05), but the myocardial retention time was much longer than that of 99Tcm-TEBO (planar image, 20 min postinjection: 218.67×103vs 143.19×103 counts/MBq; SPECT image, 15 min postinjection (corrected): 6.76±0.45 vs 5.06±0.33, t=-12.412, P=0.001). The uptake of liver and heart/liver ratio between 99Tcm-TEBO and 99Tcm-3SP were similar (t values: -1.332-1.101, all P>0.05 within 15 min). SPECT MPI images demonstrated uniform tracer distribution with clearly visualizable myocardial boundary in normal myocardium and intense perfusion defect in infarct myocardium. High quality SPECT images could be obtained in any of the 5 min imaging windows over the first 15 min after injection of 99Tcm-3SP in normal swine and AMI-swine. Conclusion 99Tcm-3SP is a promising 99Tcm-labeled radiotracer for fast-MPI considering its high heart uptake, long myocardial retention time (20 min postinjection) and superior SPECT image quality. Key words: Myocardial perfusion imaging; Oximes; Boronic acids; Technetium; Tomography, emission-computed, single-photon; Swine

Optimized sampling for high resolution multi-pinhole brain SPECT with stationary detectors

Brain perfusion SPECT can be used in the diagnosis of various neurologic or psychiatric disorders, e.g. stroke, epilepsy, dementia and posttraumatic stress disorder. As traditional SPECT provides limited resolution and sensitivity, we recently proposed a high resolution focusing multi-pinhole clinical SPECT scanner dubbed G-SPECT-I (Beekman et al 2015, Eur. J. Nucl. Med. Mol. Imaging 42 S209). G-SPECT-I achieves data completeness in the scan region of interest (ROI) by making small translations of the patient bed while using projections from all bed positions together for image reconstruction. A strategy to restrict the number of bed translations is desired to minimize overhead time. Previously we presented optimized bed translation paths for focused partial brain imaging, while here we focus on whole brain imaging which is the common procedure in perfusion studies. Thus, a series of noise-free scans using a reduced number of bed positions were simulated and compared to an oversampled reference scan acquired with 128 bed positions. Noisy simulations were included to validate the utility of the optimized sequences in more realistic situations. Brain uptake ratios (BURs) and left–right Asymmetry Indices (AIs) in 51 selected regions of interest (ROIs) were calculated for assessment. Results show that images were barely affected by decreasing the number of bed positions from 128 down to 18 (mean deviation from the reference of only 2.2% and 1.5% for the BUR and AI, respectively) while slightly larger deviations (2.9% and 2.7%, respectively) were obtained when using 12 positions. For both 18- and 12-position sequences these deviations due to sampling were much smaller than those induced by noise (mean deviation of 6.5% and 8.6%, respectively). Given an associated total overhead for bed movement of half a minute (18 positions) or 20 s (12 positions), G-SPECT-I can be a clinical platform that brings new protocols for fast (dynamic) whole brain SPECT and motion correction into reach.

MGMDcGAN: Medical Image Fusion Using Multi-Generator Multi-Discriminator Conditional Generative Adversarial Network

In this paper, we propose a novel end-to-end model for fusing medical images characterizing structural information, i.e., $I_{S}$ , and images characterizing functional information, i.e., $I_{F}$ , of different resolutions, by using a multi-generator multi-discriminator conditional generative adversarial network (MGMDcGAN). In the first cGAN, the generator aims to generate a real-like fused image based on a specifically designed content loss to fool two discriminators, while the discriminators aim to distinguish the structure differences between the fused image and source images. On this basis, we employ the second cGAN with a mask to enhance the information of dense structure in the final fused image, while preventing the functional information from being weakened. Consequently, the final fused image is forced to concurrently keep the structural information in $I_{S}$ and the functional information in $I_{F}$ . In addition, as a unified method, MGMDcGAN can be applied to different kinds of medical image fusion, i.e., MRI-PET, MRI-SPECT, and CT-SPECT, where MRI and CT are two kinds of $I_{S}$ of high resolution, PET and SPECT are typical kinds of $I_{F}$ of low resolution. Qualitative and quantitative experiments on publicly available datasets demonstrate the superiority of our MGMDcGAN over the state-of-the-art.

REST SCAN DOES NOT IMPROVE AUTOMATIC MACHINE LEARNING PREDICTION OF MAJOR ADVERSE CORONARY EVENTS AFTER HIGH SPEED MYOCARDIAL PERFUSION IMAGING

Background: We aimed to compare the prediction of major adverse cardiac events (MACE) by machine learning (ML) using clinical information and automatically derived image variables from stress and rest scans. Methods: 2619 consecutive patients (48% male, 62±13 years), undergoing high speed SPECT,

Brain Network Underlying the Improvement of Social Functioning in Schizophrenic Patients After One-year Treatment with Social Skills Training.

To assess changes in social and neuro-cognition and regional cerebral blood flow (rCBF) in schizophrenic patients with psychotic syndrome treated with Social Skill Training (SST). 17 patients underwent two high resolution rCBF SPECT at rest before and after a one-year treatment with SST. Patients were assessed using a neuropsychological evaluation (W.A.I.S.-R, T.M.T, Verbal Fluency, W.C.S.T.). SPM8 was used to investigate rCBF changes from the pre- to the post-SST condition and the relationship between rCBF and clinical scores used as covariates of interest. All patients presented with an improvement in social perception, ability to deal with abstract social conventions, rules and judgments about people (Comprehension and Picture Completion sub-tests) and some neuro-cognitive functions sustaining the process of socially relevant information. The main effect of SST was to produce rCBF increases in precuneus, PCC, superior parietal lobules, PMC, pre-SMA, precentral gyrus, dmPFC, dlPFC, vmPFC, OFC (p<0.0001 uncorrected). The SPM analysis showed that Comprehension was supported by PMC, dmPFC, OFC and vmPFC, while the Picture Completion was supported by PMC and dmPFC (p&lt;0.0001). SST in schizophrenic patients improves resting neural activity in cortical areas of the amigdala-based and non-amygdala networks of social brain, including dmPFC and vmPFC, and dlPFC, which are known to be part of default mode and task-positive networks and to be implicated in schizophrenia.

Sci‐Thur AM: YIS – 01: New technologies for astatine‐211 targeted alpha therapy research

Purpose:The short‐range, densely ionizing α‐particles emitted by 211At (t1/2=7.2h) are well suited for the treatment of diffuse microscopic disease, using cancer targeting biomolecules. 211At availability is limited by the rarity of α‐cyclotrons required for standard production. Image‐based dosimetry is also limited for 211At, which emits low intensity X‐rays. Our goal was to leverage state‐of‐the‐art infrastructure at TRIUMF to produce and evaluate two related isotopes, 211Rn (t1/2=14.6h, 73% decay to 211At) as a generator for 211At, and 209At (t1/2=5.4h, X‐ray/gamma‐ray emitter) as a novel 211At surrogate for preclinical imaging studies.Methods:Produced by spallation of uranium with 480 MeV protons, mass separated ion beams of short‐lived francium isotopes were implanted into NaCl targets where 211Rn or 209At were produced by radioactive decay, in situ. 211Rn was transferred to dodecane from which 211At was efficiently extracted and evaluated for clinical applicability. High energy SPECT/CT was evaluated for measuring 209At activity distributions in mice and phantoms.Results:Our small scale 211Rn/211At generator system provided high purity 211At samples. The methods are immediately scalable to the level of radioactivity required for in vivo experiments with 211At. 209At‐based high energy SPECT imaging was determined suitable for pursuing image‐based dosimetry in mouse tumour models. In the future, we will utilize quantitative 209At‐SPECT for image‐based dose calculations.Conclusion:These early studies provided a foundation for future endeavours with 211At‐based α‐therapy. Canada is now significantly closer to clinical targeted α‐therapy of cancer.

SPECT imaging of colorectal cancer by targeting CD 133 receptor with 99mTc-labeled monoclonal antibody.

Previous reports suggested that CD133-positive cells had biological features of cancer stem cells (CSCs). Furthermore, CD133 expression was reported as an unfavorable prognostic factor in patients. Therefore, a new radiolabeled probe, 99mTc labeled AC133 antibody which binding with CD133 specifically, was developed to noninvasively detect CSCs by SPECT in vivo. CD133 expression was evaluated by flow cytometry in three colon cancer cell lines (HCT116, Lovo and DLD1). AC133 antibody and control IgG were conjugated with succinimidyl-6-hydrazinonicotinate hydrochloride (SHNH), and then labeled with 99mTc. The new radiolabeled probe was named as 99mTc-SHNH-AC133. The vitro cell binding assays, series SPECT imaging and biodistribution analyses were performed. Flow cytometry, immunofluorescence staining of tumor tissues were carried to verify the in-vivo imaging results. 99mTc-SHNH-AC133 was labeled with a high radiochemical purity (97.7±2.4%, N.=3) and specific activity (4.07 MBq/µg). Cellular experiments showed that the labeled AC133 antibody retained with a high binding affinity on CD133-positive cells (HCT116 and Lovo cells). Biodistribution analyses showed high tumor uptake of the tracer in HCT116 and Lovo xenografts (8.82±0.73 and 7.37±0.26 %ID/g, respectively, N.=4) and high tumor-to-muscle ratios (13.18±2.84 and 11.13±0.53, respectively, N.=4) at 36 h after injection, resulting in high contrast SPECT images with high specific tumor uptake. However, the tumor bearing CD133-negative cell (DLD1 cells) showed no obvious uptake of 99mTc-SHNH-AC133 both in-vitro cell binding and in-vivo imaging study. Moreover, the tumor uptake of 99mTc-SHNH-AC133 in positive tumor models was significantly reduced by pre-injection of excess unlabeled AC133 antibody. Flow cytometric analysis and immunofluorescence staining confirmed the CD133 expression in tumors, which correlated well with the in-vivo results. This study showed that 99mTc-SHNH-AC133 exhibited high uptake in CD133-positive tumors. The high specificity and good tumor targeting properties of 99mTc-SHNH-AC133 may provide a new method to track or locate CSCs.

Novel 99mTc(III)-azide complexes [99mTc(N3)(CDO)(CDOH)2B-R] (CDOH2 = cyclohexanedione dioxime) as potential radiotracers for heart imaging

IntroductionIn this study, novel 99mTc(III)-azide complexes [99mTc(N3)(CDO)(CDOH)2B-R] (99mTc-ISboroxime-N3: R=IS; 99mTc-MPboroxime-N3: R=MP; 99mTc-PAboroxime-N3: R=PA; 99mTc-PYboroxime-N3: R=PY; and 99mTc-Uboroxime-N3: R=5U) were evaluated as heart imaging agents. MethodsComplexes [99mTc(N3)(CDO)(CDOH)2B-R] (R=IS, MP, PA, PY and 5U) were prepared by ligand exchange between NaN3 and [99mTcCl(CDO)(CDOH)2B-R]. Biodistribution and imaging studies were carried out in Sprague–Dawley rats. Image quantification was performed to compare their initial heart uptake and myocardial retention. Results99mTc-ISboroxime-N3, 99mTc-PYboroxime-N3 and 99mTc-Uboroxime-N3 were prepared with high RCP (93–98%) while the RCP of 99mTc-MPboroxime-N3 and 99mTc-PAboroxime-N3 was 80–85%. The myocardial retention curves of 99mTc-ISboroxime-N3, 99mTc-PYboroxime-N3 and 99mTc-Uboroxime-N3 were best fitted to the bi-exponential decay function. The half-time of the fast component was 1.6±0.4min for 99mTc-ISboroxime-N3, 0.7±0.1min for 99mTc-PYboroxime-N3 and 0.9±0.4min for 99mTc-Uboroxime-N3. The 2-min heart uptake from biodistribution studies followed the ranking order of 99mTc-ISboroxime-N3 (3.60±0.68%ID/g)>99mTc-PYboroxime-N3 (2.35±0.37%ID/g)≫99mTc-Uboroxime-N3 (1.29±0.06%ID/g). 99mTc-ISboroxime-N3 had the highest 2-min heart uptake among 99mTc radiotracers revaluated in SD rats. High quality SPECT images were obtained with the right and left ventricular walls being clearly delineated. The best image acquisition window was 0–5min for 99mTc-ISboroxime-N3. ConclusionBoth azide coligand and boronate caps had significant impact on the heart uptake and myocardial retention of complexes [99mTc(N3)(CDO)(CDOH)2B-R]. Among the radiotracers evaluated in SD rats, 99mTc-ISboroxime-N3 has the highest initial heart uptake with the heart retention comparable to that of 99mTc-Teboroxime. 99mTc-ISboroxime-N3 is a promising alternative to 99mTc-Teboroxime for SPECT MPI.

Theory and realization of a 2D high resolution and high sensitivity SPECT system with an angle-encoding attenuator pattern

The camera of the conventional SPECT system requires a collimator to allow incoming photons from a specific range of incident angle to reach the detector. It is the major factor that determines the spatial resolution of the camera. Moreover, it also greatly reduces the number of detected photons and hence increases statistical fluctuations in the acquired image data. The goal of this paper is to propose a theory and design for a novel high resolution and high sensitivity SPECT system without conventional collimators. The key is to resolve the incident photons from all directional angles and detected by every detector bin. Special ‘attenuators’ were designed to ‘encode’ the incoming photons from different directions similar to coded aperture to form projection data for image reconstruction. Each encoded angular pattern of detected photons was recorded as one measurement. Different angular patterns were achieved by changing the configurations of the attenuators so that angular pattern of different measurements or measurement matrix (MM) is invertible, which guarantee a unique reconstructed image. In simulation, the attenuators were fitted on a virtual full-ring gamma camera, as an alternative to the collimators in conventional SPECT systems. To evaluate the performance of the new SPECT system, analytical simulated projection data in 2D scenario were generated from the XCAT phantom. Noisy simulation using 100 noise realizations suggests that the new attenuator design provides much improved image quality in terms of contrast-noise trade-offs (~30% improvement). The results suggest that the new design of using attenuators to replace collimator is feasible and could potentially improve sensitivity without sacrificing resolution in today’s SPECT systems.

呼吸同期撮影に基づく胸腹部PET・SPECT 画像の高画質化技術

呼吸同期撮影に基づく胸腹部PET・SPECT 画像の高画質化技術

Impact of Boronate Capping Groups on Biological Characteristics of Novel 99mTc(III) Complexes [99mTcCl(CDO)(CDOH)2B-R] (CDOH2 = Cyclohexanedione Dioxime)

This study sought to explore the impact of boronate groups on the heart uptake and myocardial retention of novel (99m)Tc(III) complexes [(99m)TcCl(CDO)(CDOH)2B-R] ((99m)Tc-ISboroxime: R = isoxazol-4-yl (IS); (99m)Tc-MPboroxime: R = N-methylpyridinium (MP); (99m)Tc-PAboroxime: R = pyrazol-3-yl (PA); (99m)Tc-PYboroxime: R = pyridin-3-yl (PY); and (99m)Tc-5Uboroxime: R = uracil-5-yl (5U)). All five new (99m)Tc(III) radiotracers were prepared in high yield and high radiochemical purity (RCP = 90-98%), and they remained stable in the kit mixture for >6 h. Biodistribution and imaging (planar and SPECT) studies were carried out using Sprague-Dawley (SD) rats. Planar image quantification was performed to compare their myocardial retention and liver clearance kinetics. It was found that their heart retention and liver clearance curves were best fitted to the biexponential decay function. The initial heart uptake at 0-1 min after injection followed the general ranking order of (99m)Tc-ISboroxime (4.98 ± 1.05%ID) ∼ (99m)Tc-Teboroxime (4.56 ± 0.91%ID) ∼ (99m)Tc-PAboroxime (4.03 ± 1.23%ID) ∼ (99m)Tc-PYboroxime (4.07 ± 0.80%ID) > (99m)Tc-5Uboroxime (3.24 ± 0.67%ID) > (99m)Tc-MPboroxime (2.53 ± 0.65%ID). The fast-phase myocardial retention time followed the general order of (99m)Tc-PAboroxime (3.21 ± 0.29 min) > (99m)Tc-Teboroxime (1.63 ± 0.40 min) ∼ (99m)Tc-PYboroxime (1.57 ± 0.29 min) ∼ (99m)Tc-ISboroxime (1.55 ± 0.32 min) > (99m)Tc-MPboroxime (0.68 ± 0.16 min) > (99m)Tc-5Uboroxime (0.33 ± 0.11 min). (99m)Tc-PAboroxime (3.05 ± 1.10%ID/g) and (99m)Tc-ISboroxime (3.75 ± 0.68%ID/g) had the 2 min initial heart uptake very close to that of (99m)Tc-Teboroxime (3.30 ± 0.50%ID/g). However, the myocardial retention time of (99m)Tc-PAboroxime was significantly longer than that of (99m)Tc-ISboroxime and (99m)Tc-Teboroxime. Even though the best time window is 0-5 min for SPECT image acquisition, high quality SPECT images could be obtained during the first 30 min postinjection of (99m)Tc-PAboroxime in SD rats. This statement was supported by the SPECT/CT studies in normal pigs. On the basis of results from this study, it was concluded that boronate groups had significant impact on the heart uptake, myocardial retention, and liver clearance kinetics of (99m)Tc(III) complexes [(99m)TcCl(CDO)(CDOH)2B-R]. The combination of high initial heart uptake with longer myocardial retention makes it possible to image the heart with (99m)Tc-PAboroxime during the first 30 min using both standard and specialized cardiac SPECT cameras.

Design and Development of a High Performance Pinhole Array Dual Head SPECT Using Monte Carlo Simulation

Design and Development of a High Performance Pinhole Array Dual Head SPECT Using Monte Carlo Simulation

Abstract 212: Temporal Trends of SPECT Myocardial Perfusion Imaging in Patients with Coronary Heart Disease: A 22-Year Experience from a Tertiary Academic Medical Center

Background: Over the past 20 years, there has been an increasing decline in the prevalence of abnormal stress single-photon emission computed tomography myocardial perfusion imaging (SPECT) studies among patients with no history of coronary artery disease (CAD). The trend of SPECT studies among patients with known CAD has not been evaluated before. Methods: Using the Mayo Clinic nuclear cardiology database, we examined all stress SPECT tests performed between 1/1991-12/2012 in patients with prior history of CAD defined as having prior myocardial infarction, percutaneous coronary intervention, and/or coronary artery bypass grafting. Patients with left bundle branch block, paced rhythm, bicycle or rest-only tests, cardiomyopathy, valvular heart disease, and technically unsatisfactory studies were excluded. The study cohort was divided into 5 time periods: 1991-5, 1996-2000, 2001-5, 2006-10, and 2011-12. Results: There were 19373 eligible SPECT tests (mean age 66.2 ± 10.9y, 75.4% men). Annual utilization of SPECT studies in patients with history of CAD increased from an average of 495 tests per year between 1991-1995 to a peak of 1425 in 2003; and then decreased to 552 tests in 2012. Asymptomatic patients comprised 33% in 1991-1995, peaked at 48% in 2006, and then decreased back to 31% in 2012. Over time, patients with typical angina decreased while patients with dyspnea increased, P &lt;0.001 (Fig 1). The percentage of high risk SPECT tests significantly decreased, and the percentage of low-risk SPECT tests significantly increased despite the overall decline of SPECT utilization between 2003 and 2012. Almost 80% of all tests performed in 2012 had a low risk summed stress score compared to 29% in 1991, P &lt;0.001 (Fig 2). Conclusions: In Mayo Clinic Rochester, annual SPECT utilization in patients with prior CAD increased between 1992 and 2003, but then decreased significantly after 2003. Fewer patients had typical angina while patients with dyspnea increased over time. High risk SPECT tests declined while low risk tests increased dramatically. These data suggest that stress SPECT was being increasingly utilized in CAD patients without typical angina who are at low risk.

Microcystic Meningioma with Late-phase Accumulation on Thallium-201 Single-photon Emission Computed Tomography: Case Report

Microcystic meningiomas are rare but benign brain tumors. Previous reports have shown that Thallium-201 single-photon emission computed tomography (201Tl SPECT) demonstrated a higher late-phase accumulation of 201Tl in malignant or recurrent meningiomas than in nonaggressive meningiomas. No study has reported 201Tl SPECT findings in microcystic meningiomas. We here describe a case of a microcystic meningioma with a high 201Tl SPECT retention rate in a 62-year-old woman who complained of headache. Computed tomography revealed an intracranial tumor in the right frontal lobe. Moreover, 201Tl SPECT revealed a high uptake of 201Tl in the tumor, which was particularly prominent in the delayed phase. The uptake index on an early image was 1.46 and that on a delayed image was 1.35. Therefore, the retention index was 0.92. After 2 years of tumor growth, we performed successful radical resection, and histological examination revealed the presence of a microcystic meningioma. Therefore, we concluded that 201Tl SPECT may be useful for the preoperative diagnosis of microcystic meningiomas and that late-phase accumulation of 201Tl is not a specific finding of malignant brain tumors. Therefore, we need to be careful in the evaluation and judgment of high retention in a delayed image of 201Tl SPECT.