Myocardial perfusion imaging with retrospective gating and integrated correction of attenuation, scatter, respiration, motion, and arrhythmia.

BACKGROUND: Absolute quantitative myocardial perfusion SPECT requires addressing of aleatory and epistemic uncertainties in conjunction with providing image quality sufficient for lesion detection and characterization. Iterative reconstruction methods enable the mitigation of the root causes of image degradation. This study aimed to determine the feasibility of a new SPECT/CT method with integrated corrections attempting to enable absolute quantitative cardiac imaging (xSPECT Cardiac; xSC). METHODS: We compared images of prototype xSC and conventional SPECT (Flash3DTM) acquired at rest from 56 patients aged 71 ± 12 y with suspected coronary heart disease. The xSC prototype comprised list-mode acquisitions with continuous rotation and subsequent iterative reconstructions with retrospective electrocardiography (ECG) gating. Besides accurate image formation modeling, patient-specific CT-based attenuation and energy window-based scatter correction, additionally we applied mitigation for patient and organ motion between views (inter-view), and within views (intra-view) for both the gated and ungated reconstruction. We then assessed image quality, semiquantitative regional values, and left ventricular function in the images. RESULTS: The quality of all xSC images was acceptable for clinical purposes. A polar map showed more uniform distribution for xSC compared with Flash3D, while lower apical count and higher defect contrast of myocardial infarction (p = 0.0004) were observed on xSC images. Wall motion, 16-gate volume curve, and ejection fraction were at least acceptable, with indication of improvements. The clinical prospectively gated method rejected beats ≥20% in 6 patients, whereas retrospective gating used an average of 98% beats, excluding 2% of beats. We used the list-mode data to create a product equivalent prospectively gated dataset. The dataset showed that the xSC method generated 18% higher count data and images with less noise, with comparable functional variables of volume and LVEF (p = ns). CONCLUSIONS: Quantitative myocardial perfusion imaging with the list-mode-based prototype xSPECT Cardiac is feasible, resulting in images of at least acceptable image quality.

Optimal choice of OSEM and SD reconstruction algorithms in CZT SPECT for hypertrophic cardiomyopathy patients.

BACKGROUND: The spectrum dynamics (SD) algorithm is a cardiac reconstruction algorithm of D-SPECT, which improves spatial resolution compared with the ordered-subsets expectation maximization (OSEM) algorithm. We evaluated the wall thickness and left ventricular (LV) volume in patients with hypertrophic cardiomyopathy (HCM) using the SD algorithm. METHODS: In a phantom study, the myocardial wall was scanned with varying wall thicknesses (10-40 mm). In the clinical study, 30 and 27 normal and HCM patients underwent myocardial perfusion imaging. RESULTS: In a phantom study, LV volume using the SD algorithm was increased by thickening the wall of the phantom. In the clinical study, the wall thickness and LV volume of OSEM and SD algorithms showed a difference between HCM and normal groups. The wall thickness using OSEM and SD algorithms were 19.4 ± 2.0 and 16.7 ± 1.5 mm in patients with normal, and 27.9 ± 4.9 and 21.8 ± 2.6 mm in patients with HCM. CONCLUSION: The SD algorithm in cases of HCM may not be able to correctly assess wall thickness and LV volume. Our study suggests that the OSEM is more suitable in cases of HCM than the SD algorithm.

The utility of heart-to-mediastinum ratio using a planar image created from IQ-SPECT with Iodine-123 meta-iodobenzylguanidine.

AIMS: 123I-labeled meta-iodobenzylguanidine (MIBG) has used a planar image to measure the heart-to-mediastinum ratio (HMR). However, planar images are not available from IQ-SPECT with SMARTZOOM collimator due to its multi-focal collimation. Since we created the planar-equivalent (IQ-planar) images by adding all slices of the IQ-SPECT coronal image. The aim of this study was to demonstrate the utility of the new method for calculating HMR. METHODS: The planar image and transverse images of IQ-SPECT with attenuation and scatter corrections (ACSC) and without ACSC (NC) were obtained. Multi-planar reconstruction and ray-summation processing were applied to create IQ-planar images with NC and ACSC. Linear regression between the measured HMR from the planar image and the mathematically calculated HMR was used to calibrate HMR to standardized values. RESULTS: Scatterplots and linear regression lines between planar and IQ-planar HMRs before and after cross-calibration showed systematic differences in both NC and ACSC conditions. The IQ-planar HMR with NC and ACSC was significantly higher compared with that of the conventional planar image. However, the IQ-planar HMR with NC and ACSC after cross-calibration was similar to the standardized HMR calculated by planar image. CONCLUSION: The IQ-planar HMR using the new ray-summation processing method could be used along with the conventional planar HMR.

Experimental evaluation of the GE NM/CT 870 CZT clinical SPECT system equipped with WEHR and MEHRS collimator.

PURPOSE: A high-energy-resolution whole-body SPECT-CT device (NM/CT 870 CZT; C-SPECT) equipped with a CZT detector has been developed and is being used clinically. A MEHRS collimator has also been developed recently, with an expected improvement in imaging accuracy using medium-energy radionuclides. The objective of this study was to compare and analyze the accuracies of the following devices: a WEHR collimator and the MEHRS collimator installed on a C-SPECT, and a NaI scintillation detector-equipped Anger-type SPECT (A-SPECT) scanner, with a LEHR and LMEGP. METHODS: A line phantom was used to measure the energy resolutions including collimator characteristics in the planar acquisition of each device using 99m Tc and 123 I. We also measured the system's sensitivity and high-contrast resolution using a lead bar phantom. We evaluated SPECT spatial resolution, high-contrast resolution, radioactivity concentration linearity, and homogeneity, using a basic performance evaluation phantom. In addition, the effect of scatter correction was evaluated by varying the sub window (SW) employed for scattering correction. RESULTS: The energy resolution with 99m Tc was 5.6% in C-SPECT with WEHR and 9.9% in A-SPECT with LEHR. Using 123I, the results were 9.1% in C-SPECT with WEHR, 5.5% in C-SPECT with MEHRS, and 10.4% in A-SPECT with LMEGP. The planar spatial resolution was similar under all conditions, but C-SPECT performed better in SPECT acquisition. High-contrast resolution was improved in C-SPECT under planar condition and SPECT. The sensitivity and homogeneity were improved by setting the SW for scattering correction to 3% of the main peak in C-SPECT. CONCLUSION: C-SPECT demonstrates excellent energy resolution and improved high-contrast resolution for each radionuclide. In addition, when using 123I, careful attention should be paid to SW for scatter correction. By setting the appropriate SW, C-SPECT with MEHRS has an excellent scattered ray removal effect, and highly homogenous imaging is possible while maintaining the high-contrast resolution.

[Influence of the Each Correction Method for the Specific Binding Ratio and Standardized Uptake Value in the Dopamine Transporter SPECT].

This study was to reveal the characteristics for each correction effect of specific binding ratio (SBR) and standardized uptake value (SUV) in the dopamine transporter (DAT) single photon emission computed tomography (SPECT). We created the 123I solution of five radioactive concentrations, which was filled with two types of striatum phantom such as separated or integrated caudate and putamen. We created 10 striatum accumulation models by combining the 123I solution. Images were reconstructed using ordered subset expectation maximization (OSEM) incorporating attenuation correction (AC), scatter correction (SC) or resolution recovery (RR) for the collected data of 10 striatum accumulation models and 66 patients. Correction combinations were AC, ACSC, ACRR and ACSCRR. The SBR, SUVmean and SUVmax were evaluated correlation and relative error between SBR, SUVmean and SUVmax by each correction method. The SBR and SUV had a significant positive correlation with all correction methods. The minimum values of relative error for SBR, SUVmean and SUVmax were 39.7% with ACSCRR, 18.4% with AC and 16.5% with ACSC, respectively. In addition, the ACSC of SBR and SUVmean was almost same value. The SBR showed significantly higher values by incorporating SC, while the SUV was significantly higher values by incorporating RR. It was suggested that SUV could be used for the quantitative index of DAT SPECT. Furthermore, we demonstrated the characteristic among each correction for SBR and SUV.

[Simplification of Activity Measurement during Quantitative Value Estimation in Bone SPECT].

PURPOSE: To calculate the quantitative values in bone single-photon emission computed tomography, it is necessary to measure the amount of syringe radiation before and after the administration of a radiopharmaceutical. We proposed a method to omit the measurement of radioactivity. In this study, we clarified the effects of adopting this method and calculated its influence on quantitative values in a clinical setting. METHODS: We derived a relational expression of the administration time and dose of radioactivity from the measured value and the administration time of the syringe dose before and after the administration in each patient. Next, we determined the differences for radioactivity calculated from this relational expression (estimated dose) and actual administered radioactivity (actual dose). Furthermore, we calculated the differences in the quantitative values of a normal region (the fourth lumbar vertebra) on adopting these data. RESULTS: No significant differences between the estimated dose and actual dose were noted. Additionally, no significant differences in the quantitative values were observed. CONCLUSION: Our findings suggest that adoption of the estimated dose does not affect the quantitative value. When the estimated dose is adopted, it can be administered with an accuracy of 0.80%. Thus, it is possible to omit the actual measurement of radioactivity by using our proposed method.

An Exploratory Study of Washout Rate Analysis for Thallium-201 Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging Using Cadmium Zinc Telluride Detectors.

The aim of this study was to assess the washout rate (WOR) for thallium-201-chloride single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) using cadmium zinc telluride detectors for SPECT (CZT SPECT) versus conventional Anger-type SPECT (conventional SPECT). A total of 52 Japanese patients were examined using CZT SPECT and conventional SPECT, and the global WORs were compared. Additionally, the MPI WORs were compared for patients with a normal MPI versus those in whom MPI reflected the patients' multivessel disease (MVD) MPI. Washout rates were similar when approximated by CZT SPECT versus conventional SPECT 12.59 ± 2.26%/h vs 12.57 ± 2.27%/h ( P = .997), respectively. The WOR values for CZT SPECT versus conventional SPECT were 13.42%/h (1.53%/h) vs 13.93%/h (1.24%/h) ( P = .337), respectively, for 7 normal MPI patients, and 10.64 ± 2.20%/h vs 10.84 ± 2.26%/h ( P = .848), respectively, for 7 MVD-MPI patients. The WOR values for normal MPI versus MVD-MPI patients for CZT SPECT were 13.42 ± 1.53%/h vs 10.64 ± 2.20%/h ( P = .025), respectively. Thallium-201-chloride WOR values obtained with high-efficiency CZT SPECT, which enabled significantly reduced imaging times and use of a low-dose protocol, were similar to those obtained with conventional SPECT.

Optimal thallium-201 dose in cadmium-zinc-telluride SPECT myocardial perfusion imaging.

BACKGROUND: We aimed to determine the optimal thallium 201 chloride (thallium-201) dose using a novel ultrafast cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors (D-SPECT). METHODS AND RESULTS: The optimal thallium-201 dose for obtaining left ventricular (LV) myocardial counts was determined from a phantom study. Consecutive 292 patients underwent stress myocardial perfusion imaging with a thallium-201 injection. Stress test comprised exercise or pharmacological (adenosine) provocation. We calculated an optimal thallium-201 dose that resulted in better LV myocardial counts during 6 minutes of acquisition time. We corrected the respective values according to the patient's age, sex, body mass index (BMI), and type of stress test. The lowest thallium-201 dose for obtaining acceptable imaging was 1.2 million counts. Radiopharmaceutical doses showed a positive correlation with the patient's age (P < .001), sex (P = .012), BMI (P < .001), and type of stress test (P < .001). Multivariate analysis revealed that the patient's BMI and the type of stress test were statistically significant factors for determining the correct radiopharmaceutical dose (P < .001 for both). CONCLUSIONS: For clinical use of the CZT SPECT system, the optimal individual thallium-201 doses can be determined based on the patient's BMI and type of stress test.

Creation and characterization of normal myocardial perfusion imaging databases using the IQ·SPECT system.

BACKGROUND: Image acquisition by short-time single-photon emission-computed tomography (SPECT) has been made feasible by IQ·SPECT. The aim of this study was to generate normal databases (NDBs) of thallium-201 (201Tl) myocardial perfusion imaging for IQ·SPECT, and characterize myocardial perfusion distribution. METHODS AND RESULTS: We retrospectively enrolled 159 patients with a low likelihood of cardiac diseases from four hospitals in Japan. All patients underwent short-time 201Tl myocardial perfusion IQ·SPECT with or without attenuation and scatter correction (ACSC) in either supine or prone position. The mean myocardial counts were calculated using 17-segment polar maps. Three NDBs were derived from supine and prone images as well as supine images with ACSC. Differences between the supine and prone positions were observed in the uncorrected sex-segregated NDBs in the mid-inferolateral counts (p ≤ 0.016 for males and p ≤ 0.002 for females). Differences between IQ·SPECT and conventional SPECT were also observed in the mid-anterior, inferolateral, and apical lateral counts (p ≤ 0.009 for males and p ≤ 0.003 for females). Apical low counts attributed to myocardial thinning were observed in the apical anterior and apex segments in the supine IQ·SPECT NDB with ACSC. CONCLUSIONS: There were significant differences between uncorrected supine and prone NDBs, between uncorrected supine NDB and supine NDB with ACSC, and between uncorrected supine NDB and conventional SPECT NDB. Understanding the pattern of normal distribution in IQ-SPECT short-time acquisitions with and without ACSC will be helpful for interpretation of imaging findings in patients with coronary artery disease (CAD) or low likelihood of CAD and the NDBs will aid in quantitative analysis.

[Assessment of Left Ventricular Diastolic Function Using ECG-gated Myocardial Perfusion SPECT in Small Heart: Comparison with Ultrasound Echocardiography].

BACKGROUND: Assessment of left ventricular (LV) diastolic function is important because it is possible to detect early sign of myocardial ischemia by this assessment. The purpose of this study was to compare between electrocardiogram (ECG) -gated myocardial perfusion single photon emission computed tomography (G-SPECT) and ultrasound echocardiography in assessment of LV diastolic function in the small heart (SH). METHODS: The study population consisted of 144 patients who underwent both G-SPECT and ultrasound echocardiography. Peak filling rate (PFR), one-third mean filling rate (1/3 MFR) and the ratio of time to PFR to the RR interval (TPFR/RR) were calculated by quantitative gated SPECT (QGS) and heart risk view-F (HRV-F). Peak early mitral annular velocity (e') was used as the reference standard of LV diastolic function. RESULTS: There were 33 patients with end-systolic volume (ESV) of ≤10 ml (SH10), 51 patients with ESV of 11-20 ml (SH 20) and 60 patients with ESV of >20 ml (normal-sized heart: NH). In SH10, PFR calculated by QGS was not correlated with e'. However, that by HRV-F was significantly correlated with e' (r=0.47, p=0.006). On the other hand, 1/3 MFR and TPFR/RR calculated by QGS and HRV-F were not correlated with e' in SH10 and SH20. PFR, 1/3 MFR and TPFR/RR calculated by QGS and HRV-F were correlated with e' in NH.

Reducing the small-heart effect in pediatric gated myocardial perfusion single-photon emission computed tomography.

BACKGROUND: We compared two reconstruction algorisms and two cardiac functional evaluation software programs in terms of their accuracy for estimating ejection fraction (EF) of small hearts (SH). METHODS: The study group consisted of 66 pediatric patients. Data were reconstructed using a filtered back projection (FBP) method without the resolution correction (RC) and an iterative method based on an ordered subset expectation maximization (OSEM) algorithm with the RC. EF was evaluated using two software programs of quantitative gated single-photon emission computed tomography (SPECT) (QGS) and cardioREPO. We compared the EF of gated myocardial perfusion SPECT to echocardiographic measurement (Echo). RESULTS: Forty-eight of 66 patients had an end-systolic volume < 20 mL which was used as the criterion for being included in the SH group, and the SH effect led to an overestimation of EF. While significant differences were observed between Echo (66.9 ± 5.0%) and QGS-FBP without RC (76.9 ± 8.4%, P < .0001), QGS-OSEM with RC (76.6 ± 8.6%, P < .0001), and cardioREPO-FBP without RC (72.1 ± 10.0%, P = .0011), no significant difference was observed between Echo and cardioREPO-OSEM with RC (67.4 ± 6.1%) in SH group. CONCLUSIONS: In pediatric gated myocardial perfusion SPECT, the SH effect can be significantly reduced when an OSEM algorithm is used with RC in combination with the specific cardioREPO algorithm.

The high matrix acquisition technique for imaging of atherosclerotic plaque inflammation in fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography with time-of-flight: Phantom study.

BACKGROUND: Motion artifact and partial volume effect caused underestimation of coronary plaque inflammation. This study evaluated the high matrix acquisition technique using time-of-flight (TOF) positron emission tomography/computed tomography for imaging of atherosclerotic plaque inflammation with fluorine-18 fluorodeoxyglucose in small and moving phantoms. METHODS AND RESULTS: All images were reconstructed using a conventional algorithm without TOF (4 × 4 × 4 mm3 voxel size) and a high matrix algorithm with TOF (2 × 2 × 2 mm3 voxel size). Microsphere phantoms of 10, 7.9, 6.2, 5.0, and 4.0 mm diameters were acquired in 3-dimensional list-mode for 30 minutes. A heart phantom mimicking cardiac motion consisted of a hot spot simulating a plaque (φ 4 mm, φ 2 mm) on the outside of the left ventricle. In the microsphere and heart phantom study, visual discrimination, maximum activity, and target-to-background ratio using the high matrix algorithm with TOF were better than those using the conventional algorithm without TOF. CONCLUSION: The high matrix algorithm with TOF improves detection of small targets in phantoms.

[Development of Body Phantom for Evaluation of Appropriate Administered Radioactivities and Image Quality on 99mTc-DMSA Scintigraphy in Pediatric Nuclear Medicine].

PURPOSE: We conducted a field survey about pediatric nuclear medicine. As a result, it was suggested that 99mTc-DMSA scintigraphy was performed at many institutions, whereas various examinations such as image acquisition and processing are not carried out using the renal phantom. Therefore, we developed the body phantom for the evaluation of appropriate administered radioactivities and image quality with renal scintigraphy in pediatric nuclear medicine. METHODS: We created three differently sized body phantoms (1-, 5-, and 20-year-old models). These pediatric body phantoms were filled with a 99mTc solution based on the consensus guideline of pediatric radiopharmaceutical administered radioactivity in Japan. The planar image was evaluated using acquisition count, uniformity and defect contrast. SPECT images were evaluated with a recovery coefficient (RC). RESULTS: The acquisition counts for pediatric body phantoms were relatively corresponded to the clinical study. The appropriate acquisition counts and the pixel size for the planar image were approximately 140 counts per pixel and 1.23-1.35 mm at 5 min acquisition times in 1- and 5-year-old pediatric body phantom studies, respectively. Although the uniformity and the cold contrast did not depend on pixel size and body size, the cold contrast was affected by body size. The RC for SPECT images depended on the performance of SPECT systems, the resolution recovery algorithm and body phantom size. CONCLUSION: The developed pediatric body phantom could allow us to establish optimal image acquisition and more evidence on renal scintigraphy in pediatric nuclear medicine.

The reproducibility of time-of-flight PET and conventional PET for the quantification of myocardial blood flow and coronary flow reserve with (13)N-ammonia.

BACKGROUND: This study aimed to validate the reproducibility of quantitative analysis using time-of-flight (TOF) and conventional PET with (13)N-ammonia ((13)N-NH3). METHODS AND RESULTS: Phantom images were reconstructed with and without TOF, and recovery coefficients (RCs) and the percent contrast of each sphere over the percent background variability were assessed. In the clinical study, 21 subjects underwent dynamic (13)N-NH3 PET scanning under stress and rest conditions. The dynamic acquisition images and intra- and inter-observer reproducibility of myocardial blood flow (MBF) and coronary flow reserve (CFR) were compared between reconstructions (with and without TOF). In the phantom study, RCs and the percent contrast of each sphere over the percent background variability was improved with TOF. In the clinical study, the noise of blood pool and myocardial images with TOF was less than that without TOF. Territorial and global intra- and inter-observer reproducibility of MBF and CFR values was excellent. Although segmental intra- and inter-observer reproducibility was excellent, there were larger variations in apex and the segment near the right ventricle (RV) without TOF. These variations became inconspicuous with TOF. CONCLUSION: Visual image quality, RCs, and percent contrast over percent background variability with TOF were better than that without TOF. Excellent correlations and good agreements in quantitative values were observed. TOF improved the variation of segmental values.

[The Optimal Reconstruction Parameters by Scatter and Attenuation Corrections Using Multi-focus Collimator System in Thallium-201 Myocardial Perfusion SPECT Study].

The aim of this study was to reveal the optimal reconstruction parameters of ordered subset conjugates gradient minimizer (OSCGM) by no correction (NC), attenuation correction (AC), and AC+scatter correction (ACSC) using IQ-single photon emission computed tomography (SPECT) system in thallium-201 myocardial perfusion SPECT. Myocardial phantom acquired two patterns, with or without defect. Myocardial images were performed 5-point scale visual score and quantitative evaluations using contrast, uptake, and uniformity about the subset and update (subset×iteration) of OSCGM and the full width at half maximum (FWHM) of Gaussian filter by three corrections. We decided on optimal reconstruction parameters of OSCGM by three corrections. The number of subsets to create suitable images were 3 or 5 for NC and AC, 2 or 3 for ACSC. The updates to create suitable images were 30 or 40 for NC, 40 or 60 for AC, and 30 for ACSC. Furthermore, the FWHM of Gaussian filters were 9.6 mm or 12 mm for NC and ACSC, 7.2 mm or 9.6 mm for AC. In conclusion, the following optimal reconstruction parameters of OSCGM were decided; NC: subset 5, iteration 8 and FWHM 9.6 mm, AC: subset 5, iteration 8 and FWHM 7.2 mm, ACSC: subset 3, iteration 10 and FWHM 9.6 mm.

[Current situations and problems of quality control for medical imaging display systems].

Diagnostic imaging has been shifted rapidly from film to monitor diagnostic. Consequently, Japan medical imaging and radiological systems industries association (JIRA) have recommended methods of quality control (QC) for medical imaging display systems. However, in spite of its need by majority of people, executing rate is low. The purpose of this study was to validate the problem including check items about QC for medical imaging display systems. We performed acceptance test of medical imaging display monitors based on Japanese engineering standards of radiological apparatus (JESRA) X-0093*A-2005 to 2009, and performed constancy test based on JESRA X-0093*A-2010 from 2010 to 2012. Furthermore, we investigated the cause of trouble and repaired number. Medical imaging display monitors had 23 inappropriate monitors about visual estimation, and all these monitors were not criteria of JESRA about luminance uniformity. Max luminance was significantly lower year-by-year about measurement estimation, and the 29 monitors did not meet the criteria of JESRA about luminance deviation. Repaired number of medical imaging display monitors had 25, and the cause was failure liquid crystal panel. We suggested the problems about medical imaging display systems.

[Development of simple processing for deleting undershooting artifact using the FBP method ─evaluation of simulation data─].

The undershooting artifact occurs using the filtered back projection (FBP) method. This artifact is influenced by a ramp filter. Thereby, the fall of the target accumulation and a deficit arise and it becomes a clinical problem. We developed a new image reconstruction method based on the FBP method to delete the undershooting artifact of FBP. The image quality of the FBP method is equivalent to that obtained by an evaluation using a digital phantom. The two segmentation and ordinary FBP methods were evaluated in terms of hot contrast, cold contrast, coefficient of variation (%CV), and root mean square uncertainty (%RSMU). The two segmentation FBP method showed equivalent values of hot contrast, % CV, and% RSMU compared with those of the ordinary FBP method. With a threshold level value, cold contrast sharply changed. However, when the threshold level of the two segmentation FBP method was set as the proper value, 90% contrast was obtained. It is necessary to set a threshold level as a proper value using the two segmentation FBP methods. I thought that it can delete an artifact in a simple way, without impairing the image quality. However, it is an examination of only a digital phantom this time. Before using it clinically, one has to use and verify a real phantom.

[Usefulness of spatially adaptive noise reduction processing in computer-assisted diagnosis system for bone scintigraphy].

OBJECTIVES: The goal of this study was to assess the diagnostic accuracy of Pixon-processed images in comparison with raw images for computer-assisted interpretation of bone scintigraphy (BONENAVI). METHODS: Whole-body scans of 57 patients with prostate cancer who had undergone bone scintigraphy for suspected bone metastases were obtained approximately 3 h after intravenous injection of 740 MBq (99m)Tc-methylene diphosphonate. We obtained two image sets: raw images and images processed using the Pixon method. Artificial neural network (ANN) values, bone scan index (BSI), number of hotspots and regional ANN value of two images set were automatically calculated by the BONENAVI software. Areas under the receiver operator characteristic curves (AUC) were calculated in patient-based and lesion-based analyses. RESULTS: In ten cases with bone metastases, ANN, BSI and number of hotspots for processed images were equivalent to those in the raw images. However, in 47 cases without bone metastases, ANN, BSI and number of hotspots for processed images showed significantly lower values than those for the raw images (p<0.05). Sensitivity, specificity and accuracy of the raw images were 90.2, 44.7 and 65.9%, and those of the processed images were 90.2, 57.4 and 72.7%, respectively. The AUC for processed images was equivalent to that for raw images. CONCLUSIONS: Specificity and accuracy in the detection of bone metastases showed the Pixon-processed images to have high diagnostic performance. We conclude that the precision of computer-assisted interpretation of bone scintigraphy can be enhanced by using Pixon processing.

Influence of spill-over for 99mTc images and the effect of scatter correction for dual-isotope simultaneous acquisition with 99mTc and 18F using small-animal SPECT-PET/CT system.

A dual-isotope simultaneous acquisition (DISA) of 99mTc and 18F affects the image quality of 99mTc by crosstalk and spill-over from 18F. We demonstrated the influence of spill-over and crosstalk on image quality and its correction effect for DISA SPECT with 99mTc and 18F. A fillable cylindrical chamber of 30 mm with NEMA-NU4 image quality phantom was filled with 99mTc only or a mixed 99mTc and 18F solution (C100). Two small-region chambers were filled with 99mTc only or a mixed 99mTc and 18F solution made at half the radioactivity concentration of C100 (C50) and non-radioactive water (C0). The 18F/99mTc ratio for DISA was set at approximately 0.4-12. Two types of 99mTc transverse images with and without scatter correction (SC and nonSC) were created. The 99mTc images of single-isotope acquisition (SIA) were created as a reference. The DISA/SIA ratio and contrast of 99mTc were compared between SIA and DISA. Although the DISA/SIA ratios with nonSC of C100, C50 and C0 gradually increased with increasing 18F/99mTc ratio, it was nearly constant by SC. The contrasts of C100 and C50 were similar to a reference value for both nonSC and SC. In conclusion, DISA images showed lower image quality as the 18F/99mTc ratio increased. The image quality in hot-spot regions such as C100 and C50 was improved by SC, whereas cold-spot regions such as C0 could not completely remove the influence of spill-over even with SC.

Efficacy of a Novel Respiratory Motion Reduction Block in Reducing Motion Artifact on Myocardial Perfusion Single-Photon Emission Computed Tomography.

PURPOSE: Motion artifacts caused by heart motion during myocardial perfusion single-photon emission computed tomography (SPECT) can compromise image quality and diagnostic accuracy. This study aimed to evaluate the efficacy of the novel respiratory motion reduction block (RRB) device in reducing motion artifacts by compressing the hypochondrium and improving SPECT image quality. METHODS: In total, 91 patients who underwent myocardial perfusion SPECT with 99mTc-sestamibi were retrospectively analyzed. Patients (n = 28) who underwent SPECT without the RRB were included in the control group, and those (n = 63) who underwent SPECT with the RRB were in the RRB group. The distance of heart motion during dynamic acquisition was measured, and projection data were assessed for patient motion and motion artifacts. Patient motion was classified into various levels, and motion artifacts on SPECT images were visually examined. RESULTS: The distances of heart motion without and with the RRB were 15.4 ± 5.3 and 7.5 ± 2.3, respectively. Compared with the control group, the RRB group had a lower frequency of heart motion based on the projection data, particularly in terms of creep and shift motion. The RRB group had a significantly lower incidence of motion artifacts on SPECT images than the control group. CONCLUSIONS: The RRB substantially reduced specific types of motion, such as shift and creep, and had a low influence on bounce motion. However, it could effectively suppress respiratory-induced heart motion and reduce motion artifacts on myocardial perfusion SPECT, thereby emphasizing its potential for improving image quality.