[Validation of Simulation Codes for Nuclear Imaging Using Digital Phantoms].

Validation study of simulation codes was performed based on the measurement of a sphere phantom and the National Electrical Manufacturers Association (NEMA) body phantoms. SIMIND and Prominence Processor were used for the simulation. Both source and density maps were generated using the characteristics of 99mTc energy. A full width at half maximum (FWHM) of the sphere phantom was measured and simulated. Simulated recovery coefficient and the background count coefficient of variation were also compared with the measured values in the body phantom study. When the two simulation codes were compared with actual measurements, maximum relative errors of FWHM values were 3.6% for Prominence Processor and -10.0% for SIMIND. The maximum relative errors of relative recovery coefficients exhibited 11.8% for Prominence Processor and -2.0% for SIMIND in the body phantom study. The coefficients of variation of the SPECT count in the background were significantly different among the measurement and two simulation codes. The simulated FWHM values and recovery coefficients paralleled measured results. However, the noise characteristic differed among actual measurements and two simulation codes in the background count statistics.

Optimization of scatter estimation window setting for quantitative analysis in 111 In-pentetreotide single photon emission computed tomography imaging.

OBJECTIVE: The aim of this study was to validate the optimal scatter correction method and scatter estimation window setting in terms of image quality and quantitative accuracy for quantitative indium-111 (111In)-pentetreotide SPECT imaging. MATERIALS AND METHODS: We used a positron emission tomography/computed tomography (PET/CT) phantom to validate image quality and quantitative accuracy, and the SPECT images were acquired by the multi-energy window (MEW) method. The scatter estimation was performed using four kinds of energy windows (MEW1, MEW2, MEW3, and MEW4). Scatter correction was also performed using a dual-energy window (DEW) for comparison with MEWs. Image quality was assessed using percent contrast (% contrast) and background variability, and quantitative accuracy was assessed using the mean standardized uptake value (SUVmean) with hot spheres. RESULTS: In the quantification, all MEW settings approached the theoretical SUVmean (MEW1, 0.99±0.06; MEW2, 0.99±0.05; MEW3, 1.00±0.08; MEW4, 0.97±0.12) in contrast to DEW (0.88±0.05). The SUVmean value for scatter correction of both photopeaks for a 28 mm sphere showed the smallest difference from the theoretical value. CONCLUSION: The scatter correction method that gave optimal image quality and quantitative accuracy was MEW3 with two 20% energy windows (one over each photopeak) and four adjacent 3% scatter estimation windows (one on each side of the two photopeaks).

[Influence of Scintillation Camera Uniformity on Artifact Generation: A Simulation Study].

PURPOSE: Non-uniformity of a scintillation camera can result in artifacts on planar, projection, and single-photon emission computed tomography (SPECT) images. The purpose of this study was to evaluate the effect of field uniformity on artifact generation. METHODS: Using a simulation phantom, we investigated the relationship between non-uniformity of the image and artifacts on planar, projection, and SPECT images. All the non-uniformity images were generated by decreasing the photomultiplier tube sensitivity ranging from 0% to 10%. Quantitative analysis was performed using integral and differential uniformity. We also visually assessed artifact magnitude. RESULTS: Integral and differential uniformity increased with decreasing the photomultiplier tube sensitivity and tended to be higher in SPECT images compared with planar and projection images. For visual assessment, mean scores in SPECT images were higher than in planar and projection images for artifact detection. CONCLUSIONS: Our results indicated that decreasing field uniformity is expected to produce artifacts in planar and SPECT images. Also, SPECT images require very high-field uniformity.

[Effect of Misregistration between SPECT and CT Images on Attenuation Correction for Quantitative Bone SPECT Imaging].

PURPOSE: The aim of this study was to evaluate the effect of misregistration between single-photon emission computed tomography (SPECT) and computed tomography (CT) images on bone SPECT. METHODS: We acquired SPECT and CT images of a body phantom filled with bone-equivalent solution and 99mTc for evaluation of bone SPECT. SPECT images were reconstructed using attenuation correction maps obtained by shifting the attenuation coefficients from non-shifted values (reference). Activity concentrations, SPECT standardized uptake values (SPECT-SUVs), and tumor background ratios (TBRs) were evaluated. RESULTS: Activity concentrations and SPECT-SUVs decreased with decreasing attenuation coefficient. The difference in attenuation coefficient was especially large between the shifted-to-lung (0.085 cm-1) and reference (0.249 cm-1) values. Non-shifted and shifted-to-lung SPECT-SUVs were 11.5±1.0 and 2.3±0.2, respectively. TBR also decreased with decreasing attenuation coefficient. The maximum percentage change in TBR was 86% in the shifted-to-lung value. CONCLUSIONS: Our results indicate that the accuracy of activity concentration and lesion detectability was commonly affected by misalignment between SPECT and CT images. Although the impact of SPECT/CT misregistration on bone SPECT is case-specific and difficult to predict, it is important to reduce the incidence of misregistration errors for quantitative bone SPECT imaging.

Novel Index (Hepatic Receptor: IHR) to Evaluate Hepatic Functional Reserve Using (99m)Tc-GSA Scintigraphy.

PURPOSE: This study aimed to evaluate the novel index of hepatic receptor (IHR) on the regression analysis derived from time activity curve of the liver for hepatic functional reserve. METHODS: Sixty patients had undergone (99m)Tc-galactosyl serum albumin ((99m)Tc-GSA) scintigraphy in the retrospective clinical study. Time activity curves for liver were obtained by region of interest (ROI) on the whole liver. A novel hepatic functional predictor was calculated with multiple regression analysis of time activity curves. In the multiple regression function, the objective variables were the indocyanine green (ICG) retention rate at 15 min, and the explanatory variables were the liver counts in 3-min intervals until end from beginning. Then, this result was defined by IHR, and we analyzed the correlation between IHR and ICG, uptake ratio of the heart at 15 minutes to that at 3 minutes (HH15), uptake ratio of the liver to the liver plus heart at 15 minutes (LHL15), and index of convexity (IOC). RESULTS: Regression function of IHR was derived as follows: IHR=0.025×L(6)-0.052×L(12)+0.027×L(27). The multiple regression analysis indicated that liver counts at 6 min, 12 min, and 27 min were significantly related to objective variables. The correlation coefficient between IHR and ICG was 0.774, and the correlation coefficient between ICG and conventional indices (HH15, LHL15, and IOC) were 0.837, 0.773, and 0.793, respectively. IHR had good correlation with HH15, LHL15, and IOC. CONCLUSIONS: The finding results suggested that IHR would provide clinical benefit for hepatic functional assessment in the (99m)Tc-GSA scintigraphy.

Effect of Reconstruction Strategies for the Quantification and Diagnostic Accuracy of (123)I-FP-CIT SPECT.

PURPOSE: This study evaluates the effect of reconstruction strategies for the quantification and diagnostic accuracy of (123)I-FP-CIT SPECT. METHODS: We evaluated the quantification of (123)I-FP-CIT SPECT obtained by several combinations of reconstruction using the striatal phantom. The phantom images were reconstructed using FBP and OSEM with/without attenuation correction (AC) and scatter correction (SC). We calculated the specific binding ratio (SBR) using volume of interest (VOI) analysis on each reconstructed images. For the clinical study, 40 patients who underwent (123)I-FP-CIT SPECT were selected. We grouped the patients into the normal binding group and decreased binding group according to their clinical diagnosis. The clinical images were reconstructed under the same conditions as the phantom study. The SBRs were calculated, and a receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic accuracy. RESULTS: The SBRs with AC and SC significantly increased compared with no corrections. In the clinical study, although ROC analysis showed no significant difference in the all combinations of reconstruction, the area under the curve using SC and AC tended to be higher than that obtained by other reconstruction. CONCLUSIONS: Quantification of (123)I-FP-CIT SPECT was affected by reconstruction strategies. In addition, both the AC and SC improved the diagnostic accuracy of (123)I-FP-CIT SPECT. Our results suggest that both the AC and SC are recommended for the improving the quantification and diagnostic accuracy in (123)I-FP-CIT SPECT.

[Accuracy of Modulation Transfer Function for Target Size and Field of View in a Circular Edge Strategy Using the CT Image Measurement Program].

PURPOSE: The purpose of this study was to evaluate the effects of target diameter and display-field of view (D-FOV) in modulation transfer function (MTF) by circular edge strategy using the computed tomography (CT) image measurement program "CTmeasure". METHODS: We calculated the MTF (MTF(edge)) using the circular edge strategy applied to cylindrical phantom (200 mmφ) that inserted with cylinders have 10, 20, 30, and 40 mm diameters. The phantom images were reconstructed using filtered back projection method varied with D-FOV (240, 320, 400, and 500 mm). The study compared both MTF(edge) and MTF(wire) at MTF50% and MTF(10%) for target diameter and D-FOV, respectively. RESULTS: The MTF(edge) by the different of target diameter indicated in rough compatibility. However, MTF(edge) of D-FOV diameters (320, 400, and 500 mm) decreased in the high frequency range. CONCLUSIONS: The circular edge strategy for MTF depended on the D-FOV, however, it was little dependent on target diameter using the CT image measurement program "CTmeasure".

[Accuracy of Resolution Recovery in PSF-based Fully-3D PET Image Reconstruction: Simulation and Phantom Study in Multicenter Trial].

PURPOSE: Recently, the quality of positron emission tomography (PET) images has rapidly improved using resolution recovery algorithm with point spread function (PSF). The aim of this study was to investigate the accuracy of the resolution recovery algorithm using three different PET systems. METHODS: Three PET scanner models, the GE Discovery 600 M (D600M), SIEMENS Biograph mCT (mCT), and SHIMADZU SET-3000GCT/X (3000GCT) were used in this study. The radial dependences of spatial resolution (full width at half maximum: FWHM) were obtained by point source measurements (0.9 mmφ). All PET data were acquired in three-dimensional (3D) mode and reconstructed using the filtered back projection (FBP) , 3D-ordered subsets expectation maximization (3D-OSEM or dynamic row-action maximum likelihood algorithm) , and 3D-OSEM+PSF (PSF) algorithms. Two indicators, aspect ratio (ASR) and resolution recovery ratio (RRR), were calculated from measured FWHMs and compared among the three PET scanners. RESULTS: In D600 and 3000GCT, distortions of the radial direction were slightly increased at circumference of field of view (FOV). On the other hand, random distortions were occurred in both radial and tangential direction in mCT. ASRs calculated from 3D-OSEM images at circumference of FOV were 2.06, 1.22, and 2.04 on D600M, mCT, and 3000GCT, respectively. ASR improved with PSF in all PET scanners. On the other hand, RRR with PSF were calculated 57.6%, 61.4%, and 31.6%, respectively. CONCLUSION: Our results suggest that the spatial resolutions of PET images could be improved with PSF algorithm in all PET systems; however, effect of PSF was different depending on PET systems. Furthermore, PSF algorithm could not completely improve spatial resolutions in circumference of FOV.

[Evaluation of Measurement Accuracy and Inter-institutional Comparison for Dose Calibrators].

PURPOSE: The aim of this study was to validate the reliability of dose calibrators for measuring the radioactivity of several radioisotopes in multi-institution. METHODS: We evaluated the measurement accuracy of dose calibrators using a commercially available source ((67) Ga, (99m) Tc, (123) I, (201) TL). Nine dose calibrators (five models) in seven institutions were performed in this study. Each source was measured at least 3 times a day over a period of 4 half-life. Linearity of concentration (%error value) and percent difference values (%diff measurement) between measured and estimated radioactivity were calculated to evaluate the measurement accuracy. In addition, difference among institutions (%diff institution) was evaluated by the error values between measured and reference institution values. RESULTS: Good linearity of concentration was found between measured and estimated radioactivity in (99m)Tc and (123)I. However, %error value was increased in (67)Ga and (201)TL (maximum 19.3%). %diff measurements were 1.9 ± 0.3% for (67)Ga, -0.9 ± 0.3% for (99m)Tc, 2.2 ± 0.4% for (123)I, and -0.7 ± 0.3% for (201)TL, respectively. Although there were no clear differences in six institutions, %diff institution in one institution tended to be higher than that obtained in other institutions. CONCLUSIONS: Our results indicated that measurement accuracy of nine dose calibrators (five models) was relatively stable. However, difference of measured values tended to be higher in a part of institution and source. It is important to perform quality assurance and quality control for dose calibrator using traceable source.

[Development of a Novel Body Phantom with Bone Equivalent Density for Evaluation of Bone SPECT].

We developed a custom-designed phantom for bone single photon emission computed tomography (SPECT)-specific radioactivity distribution and linear attenuation coefficient. The aim of this study was to evaluate the accuracy of the phantom. The lumbar phantom consisted of the trunk of a body phantom (background) containing a cylinder (vertebral body), a sphere (tumor), and a T-shaped container (processus). The vertebral body, tumor, and processus phantoms contained a K(2)HPO(4) solution of bone equivalent density and 50, 300 and 50 kBq/mL of (99m)Tc, respectively. The body phantom contained 8 kBq/mL of (99m)Tc solution. SPECT images were acquired using low-energy high-resolution collimation, a 128 × 128 matrix and 120 projections over 360° with a dwell time of 15 sec/view × 4 times. Thereafter, CT images were acquired at 130 kV and 70 ref mAs using adaptive dose modulation. The SPECT data were reconstructed with ordered subset expectation maximization with three-dimensional, scatter, and CT-based attenuation correction. Count ratio, linear attenuation coefficient (LAC), and full-width at half-maximum (FWHM) were measured. Count ratios between the background, the vertebral body, and the tumor in SPECT images were 463.8: 2888.0: 15150.3 (1: 6.23: 32.7). The LAC of the background and vertebral body in the CT-derived attenuation map were 0.155 cm⁻¹ and 0.284 cm⁻¹, respectively, and the FWHM measured from the processus was 15.27 mm. The precise counts and LAC indicated that the phantom was accurate and could serve as a tool for evaluating acquisition, reconstruction parameters, and quantitation in bone SPECT images.

[Validation of an optimal analysis method and reproducibility to calculate the heart-to-mediastinum ratio and washout rate in the iodine-123-labeled metaiodobenzylguanidine myocardial scintigraphy].

PURPOSE: The aim of this study was to investigate an appropriate analysis method and multicenter reproducibility of heart-to-mediastinum ratio (H/M) and washout rate (WR) in iodine-123-labeled metaiodobenzylguanidine (123I-MIBG) myocardial scintigraphy with a phantom. METHODS: We evaluated the optimal region of interest (ROI) setting method about the mediastinum and heart by varying the position and shape of the ROI. The mathematical method was changed to a combination of decay time correction (DTC) and background correction (BC). We evaluated the reproducibility of the H/M and WR between institutions. RESULT: H/M decreased to 23.49% and WR increased to 20.68% by changing the mediastinum ROI position from upper to lower. H/M increased to 26.03% by changing the heart ROI position from base to apex. H/M decreased to 38.36% with BC, and WR was reduced up to 48.51% with DTC. Reproducibility of the H/M and WR between institutions was improved by performing optimization of the ROI setting and unification of the mathematical method. DISCUSSION: The position of the mediastinum ROI should be set on the upper mediastinum. The position of the heart ROI should be set on the apex of the heart. WR should be calculated with DTC and BC. Our results suggest that the reproducibility of the H/M and WR between institutions was improved by performing optimization of the ROI setting and unification of the mathematical method.

[Validation of noise reduction in iterative reconstruction: a simulation phantom study].

PURPOSE: In the iterative reconstruction method, image noise tends to increase in proportion to falling available photon count and increasing update number. Image filtering is an important factor in single photon emission computed tomography (SPECT) image reconstruction, but it is frequently treated in a subjective way. The aim of this study was to evaluate the effects of pre-reconstruction filtering and post-reconstruction filtering on the iterative reconstruction process. METHODS: Using simulation phantoms, projection data were reconstructed using ordered subsets expectation maximization (OSEM) with or without compensation for resolution recovery. Pre- and post-reconstruction filtering was performed using a Butterworth filter (BW) (range: 0.3-1.3 cycles/cm) and a Gaussian filter (GA) (range: 0.3-1.3 mm) with various parameters. We evaluated the variances of full width at half maximum (FWHM), coefficients of variation (CV), image contrast and normalized mean squared error (NMSE) values. RESULTS: The FWHM values for pre-reconstruction filtering tended to be lower than those observed for post-reconstruction filtering. These values were 5.1 mm (pre-reconstruction) and 6.7 mm (post-reconstruction). The CV on pre- and post-reconstruction filtering was 7.5% and 11.6%. Pre-reconstruction filtering reduced image noise more effectively than post-reconstruction filtering. The contrast for pre-reconstruction filtering was similar to that observed after post-reconstruction filtering. However, contrast after filtering with a GA slowly decreased as compared to the BW. NMSE values obtained by pre-reconstruction filtering tended to be lower than those observed for post-reconstruction filtering. CONCLUSIONS: Pre-reconstruction filtering provided SPECT image quality comparable to that from post-reconstruction filtering, especially when using the BW. Our results suggest that pre-reconstruction filtering is a beneficial method when applied to the iterative reconstruction method with or without compensation for resolution recovery.

Feasibility of noise-reduction reconstruction technology based on non-local-mean principle in SiPM-PET/CT.

Quantitative values of positron emission tomography (PET) images using non-local-mean in a silicon photomultiplier (SiPM)-PET/computed tomography (CT) system with phantom and clinical images. The evaluation was conducted on a National Electrical Manufacturers Association body phantom with micro-spheres (4, 5, 6, 8, 10, 13 mm) and clinical images using the SiPM-PET/CT system. The signal-to-background ratio of the phantom was set to 4, and all PET image data was obtained and reconstructed using three-dimensional ordered subset expectation maximization, time-of-flight, point-spread function, and a 4-mm Gaussian filter (GF) and clear adaptive low-noise method (CaLM) in mild, standard, and strong intensities. The evaluation included the standardized uptake value (SUV), percent contrast (QH), coefficient of variation of the background area (CVbackground) clinical imaging for SUV of lung nodules, liver signal-to-noise ratio (SNR), and visual evaluation. SUVmax for 8-mm sphere in phantom images at 2 min for GF and CaLM (mild, standard, strong) were 2.11, 2.32, 2.02, and 1.72; the QH, 8 mm was 27.33 %, 27.47 %, 21.81 %, and 16.09 %; and CVbackground was 12.78, 11.35, 7.86, and 4.71, respectively. CaLM demonstrated higher SUVmax in clinical images than GF for all lung nodule sizes. The average SUVmax for nodules with a diameter of ≤ 1 cm were 5.9 ± 2.4, 9.9 ± 4.9, 9.9 ± 5.0, and 9.9 ± 5.0 for GF and CaLM-mild, standard, and strong intensities, respectively. Liver SNRs were higher for CaLM (mild, standard, strong) compared to GF, with increasing CaLM intensity causing higher liver SNR. CaLM-mild and standard demonstrated suitability for diagnosis in visual evaluation.

[Fundamental evaluation of wavelet transform based noise reduction using soft threshold method in single photon emission computed tomography image].

PURPOSE: The wavelet transform is a newly developed signal-processing tool that decomposes a signal into various levels of resolution. The wavelet transform based noise reduction has the characteristics of optimally separating signal from noise, preserving the rapid rises and falls of a signal, and reconstructing a smooth signal from noise-imposed observations. The aim of this study was to evaluate the effects of applying a new noise reduction technique, the wavelet transform based noise reduction, to single photon emission computed tomography (SPECT) images. METHODS: Three experiments were performed using cylindrical phantom, line source, and hot-rod phantom, respectively. We acquired SPECT image datasets of each phantom, and reconstructed SPECT images using the wavelet transform based noise reduction with filter back projection (FBP). Images were de-noised by 3 parameters of wavelet transform based noise reduction: 1st wavelet weight (WW), 2nd WW, and 3rd WW, respectively. We evaluated the variances of full width at half maximum (FWHM), coefficients of variation (%CV), and frequency domains (radius direction distribution function in the power spectrum), respectively. RESULTS: In the cylindrical phantom test, %CV was reduced from 27.92% to 15.38% using the wavelet approach. On the other hand, FWHM values showed no significant change. However, the increases of wavelet weights caused artifacts on the reconstructed images in some cases. CONCLUSIONS: The wavelet based noise reduction had the significant potential to improve SPECT image. Therefore, the wavelet method should prove to be a robust approach to improve image quantification and fidelity.

Impact of list-mode reconstruction and image-space point spread function correction on PET image contrast and quantitative value using SiPM-based PET/CT system.

We evaluate the effects of list-mode reconstruction and the image-space point spread function (iPSF) on the contrast and quantitative values of positron emission tomography (PET) images using a SiPM-PET/CT system. The evaluation is conducted on an NEMA body phantom and clinical images using a Cartesion Prime SiPM-PET/CT system. The signal-to-background ratio (SBR) of the phantom is set to 2, 4, 6, and 8, and all the PET image data are obtained and reconstructed using 3D-OSEM, time-of-flight, iPSF (-/ +), and a 4-mm Gaussian filter with several iterations. The evaluation criteria include % background variability (NB,10 mm), % contrast (QH,10 mm), iPSF change in QH,10 mm (ΔQH,10 mm) for edge artifact evaluation, profile curves, visual evaluation of edge artifacts, clinical imaging for the standardized uptake value (SUV) of lung nodules, and SNRliver. NB,10 mm demonstrates no significant difference in all SBRs with and without iPSF, whereas QH,10 mm is higher based on the SBR with and without iPSF. ΔQH,10 mm indicates increased iterations and a larger rate of change (> 5%) for small spheres of < 17 mm. The profile curves portrayed almost real concentrations, except for the 10-mm sphere of SBR2 without iPSF; however, with iPSF, an overshoot was observed in the 13-mm sphere of all SBRs. The degree of overshoot increased with increasing iteration and SBR. Edge artifacts were detected at values ≥ 17-22 mm in SBRs other than SBR2 with iPSF. Irrespective of the nodal size, SUV and SNRliver improved considerably after iPSF adjustment. Therefore, the effects of list-mode reconstruction and iPSF on PET image contrast were limited, and the overcorrection of the quantitative values was validated using iPSF.

Impact of bone-equivalent solution density in a thoracic spine phantom on bone single-photon emission computed tomography image quality and quantification.

This study aimed to evaluate the effects of dipotassium hydrogen phosphate (K2HPO4) solution density on single-photon emission computed tomography (SPECT) image quality and quantification. We used a JSP phantom containing six cylinders filled with K2HPO4 solutions of varying densities. Computed tomography (CT) was performed, and CT values and linear attenuation coefficients were measured. Subsequently, SPECT images of an SIM2 bone phantom filled with 99mTc with/without K2HPO4 solution were acquired using a SPECT/CT camera. The full width at half maximum (FWHM), percentage coefficient of variation (%CV), recovery coefficient, and standardized uptake value (SUV) were evaluated to investigate the impact of the K2HPO4 solution density. The CT values and linear attenuation coefficients increased with the K2HPO4 solution density. The CT values for cancellous and cortical bones were reflected by K2HPO4 solution densities of 0.15-0.20 and 1.50-1.70 g/cm3, respectively. FWHM values were significantly lower with the K2HPO4 solution than those with water alone (18.0 ± 0.9 mm with water alone, 15.6 ± 0.2 mm with 0.15 g/cm3 K2HPO4, and 16.1 ± 0.3 mm with 1.49 g/cm3 K2HPO4). Although the %CVs showed no significant differences, the recovery coefficients obtained with water alone tended to be slightly lower than those obtained with the K2HPO4 solution. The SUV obtained using the standard density of the K2HPO4 solution differed from that obtained using the optimized density. In conclusion, SPECT image quality and quantification depends on the presence and concentration of the bone-equivalent solution. The optimal bone-equivalent solution density should be used to evaluate the bone image phantoms.

Evaluation of standardized uptake value on 131I-6ß-iodomethyl-19-norcholesterol scintigraphy for diagnosis of primary aldosteronism and correspondence with adrenal venous sampling.

PURPOSE: Adrenal venous sampling (AVS) is a reliable method for lateralization of adrenal hormone secretion, which is important for discriminating between aldosterone-producing adenoma and bilateral adrenal hyperplasia, both of which cause primary aldosteronism (PA). The aim of this study was to evaluate the diagnostic accuracy of the maximum and mean standardized uptake values (SUVmax and SUVmean, respectively) of 131I-6ß-iodomethyl-19-norcholesterol (NP-59) single-photon emission computed tomography (SPECT) for PA and its correspondence with AVS. METHODS: Adrenal NP-59 scintigraphy was performed in 14 patients with suspected PA, and AVS was also performed in 7 of them. SUVmax and SUVmean of the adrenal lesions on the dominant side and their ratios to the values on the non-dominant side (SUVRmax and SUVRmean, respectively) were calculated on SPECT images using ordered-subset conjugate gradient minimization (OSCGM) and three-dimensional ordered-subset expectation maximization (3D-OSEM) reconstruction algorithms. RESULTS: SUVmax and SUVmean on NP-59 SPECT images were significantly higher for aldosterone-producing adenoma than for bilateral adrenal hyperplasia or non-functioning adenoma and slightly superior to SUVRmax and SUVRmean (P = 0.0475 and P = 0.0447 vs. P = 0.124 and P = 0.132, respectively, with OSCGM). The respective areas under the receiver-operating characteristic curve for SUV and SUVR were 0.933 and 0.725 with OSCGM and 0.844 and 0.750 with 3D-OSEM, while SUVmax and SUVRmax had exactly the same diagnostic accuracy as SUVmean and SUVRmean. SUV and SUVR were associated with the diagnostic features on AVS and consistent with lateralization by AVS in most patients. CONCLUSION: In this study, SUV on NP-59 SPECT helped in the diagnosis of PA and was consistent with the results of AVS in nearly all cases.

Compressed sensing reconstruction shortens the acquisition time for myocardial perfusion imaging: a simulation study.

Compressed sensing (CS) has been used to improve image quality in single-photon emission tomography (SPECT) imaging. However, the effects of CS on image quality parameters in myocardial perfusion imaging (MPI) have not been investigated in detail. This preliminary study aimed to compare the performance of CS-iterative reconstruction (CS-IR) with filtered back-projection (FBP) and maximum likelihood expectation maximization (ML-EM) on their ability to reduce the acquisition time of MPI. A digital phantom that mimicked the left ventricular myocardium was created. Projection images with 120 and 30 directions (360°), and with 60 and 15 directions (180°) were generated. The SPECT images were reconstructed using FBP, ML-EM, and CS-IR. The coefficient of variation (CV) for the uniformity of myocardial accumulation, septal wall thickness, and contrast ratio (Contrast) of the defect/normal lateral wall were calculated for evaluation. The simulation was performed ten times. The CV of CS-IR was lower than that of FBP and ML-EM in both 360° and 180° acquisitions. The septal wall thickness of CS-IR at the 360° acquisition was inferior to that of ML-EM, with a difference of 2.5 mm. Contrast did not differ between ML-EM and CS-IR for the 360° and 180° acquisitions. The CV for the quarter-acquisition time in CS-IR was lower than that for the full-acquisition time in the other reconstruction methods. CS-IR has the potential to reduce the acquisition time of MPI.