Quantitative SPECT Research Articles

Quantitative imaging for 177Lu-PSMA treatment response monitoring and dosimetry.

PSMA-targeted radiopharmaceutical therapy is an established treatment option for metastatic castration-resistant prostate cancer (mCRPC). However, response rates and duration using 177Lu-PSMA-617 vary considerably between patients. Quantitative 177Lu SPECT imaging is one approach that may be leveraged to more closely monitor inter-cycle response, as well as patient-specific absorbed doses. In this work, we describe our experience implementing quantitative imaging throughout the course of 177Lu-PSMA treatment, including serial SPECT imaging to monitor response and for individualized dosimetry. We also describe our imaging protocols and dose calculation workflows for 3D voxelized patient-specific organ and tumor dosimetry, including a review of the current landscape and efforts towards harmonized dosimetry.

P-153 - Performance assessment of quantitative preclinical SPECT imaging with 155Tb and 161Tb

P-153 - Performance assessment of quantitative preclinical SPECT imaging with 155Tb and 161Tb

Follow-Up Findings in Multiple System Atrophy from [123I]Ioflupane Single-Photon Emission Computed Tomography (SPECT): A Prospective Study.

Multiple system atrophy (MSA) is subdivided into two types: MSA-P (parkinsonian) and MSA-C (cerebellar). Brain SPECT allows for the detection of nigrostriatal involvement, even in the early stages. To date, the scientific literature does not show a consensus on how to follow-up MSA, especially MSA-C. Our aim was to analyze the diagnostic effectiveness of repeat [123I]Ioflupane SPECT for the follow-up of MSA. A longitudinal observational study on 22 MSA patients (11 males and 11 females). Significant changes were obtained in the quantitative SPECT assessments in the three Striatum/Occipital indices. The qualitative SPECT diagnosis did not show differences between the initial and evolving SPECT, but the neurologist's clinical suspicion did. Our results showed a brain deterioration of around 31% at 12 months, this being the optimal cut-off for differentiating a diseased subject (capable of solving diagnostic error rate). Previous imaging tests were inconclusive, as they showed less deterioration in the SPECT and quantitative assessments with respect to the group of confirmed patients. Repeated SPECT increased the diagnostic sensitivity (50% vs. 75%) and positive predictive value (72.73% vs. 77%). In addition, repeated SPECT proved decisive in the diagnosis of initial inconclusive cases. Repeat SPECT at 12 months proves useful in the diagnosis and follow-up of MSA.

The clinical value of quantitative cardiovascular molecular imaging: a step towards precision medicine.

Cardiovascular diseases (CVD) are the leading cause of death worldwide and have an increasing impact on society. Precision medicine, in which optimal care is identified for an individual or a group of individuals rather than for the average population, might provide significant health benefits for this patient group and decrease CVD morbidity and mortality. Molecular imaging provides the opportunity to assess biological processes in individuals in addition to anatomical context provided by other imaging modalities and could prove to be essential in the implementation of precision medicine in CVD. New developments in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) systems, combined with rapid innovations in promising and specific radiopharmaceuticals, provide an impressive improvement of diagnostic accuracy and therapy evaluation. This may result in improved health outcomes in CVD patients, thereby reducing societal impact. Furthermore, recent technical advances have led to new possibilities for accurate image quantification, dynamic imaging, and quantification of radiotracer kinetics. This potentially allows for better evaluation of disease activity over time and treatment response monitoring. However, the clinical implementation of these new methods has been slow. This review describes the recent advances in molecular imaging and the clinical value of quantitative PET and SPECT in various fields in cardiovascular molecular imaging, such as atherosclerosis, myocardial perfusion and ischemia, infiltrative cardiomyopathies, systemic vascular diseases, and infectious cardiovascular diseases. Moreover, the challenges that need to be overcome to achieve clinical translation are addressed, and future directions are provided.

Mathematical Simulation in Nuclear Medicine for Optimization Diagnostic Accuracy of SPECT/CT

Purpose: To develop the method of mathematical simulation in the field of nuclear medicine and its
 practical application in research aimed at improving the diagnostic accuracy of the SPECT/CT method.
 The basic principles of the method of mathematical simulation in nuclear medicine and the main modules of the software package “Virtual Platform for Simulation Tests of the SPECT/CT Method”, created
 at the laboratory for simulation in nuclear medicine of Novosibirsk State University and the Institute of
 Theoretical and Applied Mechanics.
 Material and methods: The main principles of the developed software package are the realism of the ‘virtual patient’ mathematical model, the accuracy in modeling of physical processes in visualization, as
 well as simulation conducting close to clinical practice. All studies were carried out in collaboration
 with clinicians. The software complex was verified by comparison with clinical data. Numerical experiments have shown a close correspondence between the results of clinical and virtual studies. In simulation tests, the same errors were obtained on images that were observed on clinical images. Simulation
 computer tests were carried out using the software package “Virtual Platform...” in the field of nuclear
 oncology, cardiology and neurology, aimed at studying the accuracy of images of pathological foci to assess the possibility of switching to quantitative SPECT, as well as optimizing the protocol for examining
 patients.
 Results: Simulation tests have shown that in order to move to quantitative SPECT, it is not enough to be
 limited to the development of a methodology for calibrating SPECT systems for a particular radionuclide. There are problems without understanding and solving which it is impossible to talk about the diagnostic accuracy of the quantitative SPECT method. Such problems are edge artifacts that appear on
 the images of pathological foci, and the rule of stopping the iterative algorithm when the values of activity in the area of interest (pathological focus) that are closest to the true values are reached. A stopping
 criterion based on Pearson's modified chi-square test of goodness of fit is proposed. There is a significantly good correlation between the proposed stop criterion and the minimum RMS error of the image
 reconstruction. The results of simulation modeling with the aim of optimizing SPECT examinations of
 brain perfusion demonstrated the possibility of reducing the data recording time compared to the standard protocol by at least two times.
 Conclusion: The computer simulation method presented in this paper is a practical technology that
 contributes to the optimization and development of a quantitative SPECT method to achieve the best
 possible results in the imaging of pathological foci. Further development of the software package is focused on applications in radionuclide therapy and theranostics.

Physics-Guided Deep Scatter Estimation by Weak Supervision for Quantitative SPECT.

Accurate scatter estimation is important in quantitative SPECT for improving image contrast and accuracy. With a large number of photon histories, Monte-Carlo (MC) simulation can yield accurate scatter estimation, but is computationally expensive. Recent deep learning-based approaches can yield accurate scatter estimates quickly, yet full MC simulation is still required to generate scatter estimates as ground truth labels for all training data. Here we propose a physics-guided weakly supervised training framework for fast and accurate scatter estimation in quantitative SPECT by using a 100× shorter MC simulation as weak labels and enhancing them with deep neural networks. Our weakly supervised approach also allows quick fine-tuning of the trained network to any new test data for further improved performance with an additional short MC simulation (weak label) for patient-specific scatter modelling. Our method was trained with 18 XCAT phantoms with diverse anatomies / activities and then was evaluated on 6 XCAT phantoms, 4 realistic virtual patient phantoms, 1 torso phantom and 3 clinical scans from 2 patients for 177Lu SPECT with single / dual photopeaks (113, 208 keV). Our proposed weakly supervised method yielded comparable performance to the supervised counterpart in phantom experiments, but with significantly reduced computation in labeling. Our proposed method with patient-specific fine-tuning achieved more accurate scatter estimates than the supervised method in clinical scans. Our method with physics-guided weak supervision enables accurate deep scatter estimation in quantitative SPECT, while requiring much lower computation in labeling, enabling patient-specific fine-tuning capability in testing.

Long-Term Prognostic Value of Automated Measurements in Nuclear Cardiology: Comparisons with Expert Scoring.

Background and Objectives: Automated methods for the analysis of myocardial perfusion studies have been incorporated into clinical practice, but they are currently used as adjuncts to the visual interpretation. We aimed to investigate the role of automated measurements of summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) as long-term prognostic markers of morbidity and mortality, in comparison to the prognostic value of expert reading. Materials and Methods: The study was conducted at the Nuclear Medicine Laboratory of the University of Thessaly, in Larissa, Greece. A total of 378 consecutive patients with known or suspected coronary artery disease were enrolled in the study. All participants were referred to our laboratory for the performance of stress/rest myocardial perfusion single photon emission computed tomography. Automated measurements of SSS, SRS, and SDS were obtained by Emory Cardiac Toolbox (ECTb (Version 3.0), Emory University, Atlanta, GA, USA), Myovation (MYO, Xeleris version 3.05, GE Healthcare, Chicago, IL, USA), and Quantitative Perfusion SPECT (QPS (Version 4.0), Cedars-Sinai Medical Center, Los Angeles, CA, USA) software packages. Follow-up data were recorded after phone contacts, as well as through review of hospital records. Results: Expert scoring of SSS and SDS had significantly greater prognostic ability in comparison to all software packages (p < 0.001 for all comparisons). Similarly, ECTb-obtained SRS measurements had significantly lower prognostic ability in comparison to expert scoring (p < 0.001), while expert scoring of SRS showed significantly higher prognostic ability compared to MYO (p = 0.018) and QPS (p < 0.001). Conclusions: Despite the useful contribution of automated analyses in the interpretation of myocardial perfusion studies, expert reading should continue to have a crucial role, not only in clinical decision making, but also in the assessment of prognosis.

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

BackgroundAbsolute 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).MethodsWe 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.ResultsThe 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).ConclusionsQuantitative myocardial perfusion imaging with the list-mode-based prototype xSPECT Cardiac is feasible, resulting in images of at least acceptable image quality.

Prognostic value of myocardial flow reserve derived by quantitative SPECT for patients with intermediate coronary stenoses

BackgroundFunctional assessment of myocardial ischemia is critical for patients with intermediate coronary stenosis. As the diagnosis performance of absolute quantification of myocardial blood flow (MBF) and myocardial flow reserve (MFR) by single-photon emission tomography (SPECT) has been proven, its prognostic value in patients with intermediate coronary stenosis remains to be evaluated. MethodsPatients with one or more target lesions of ≥ 50% to ≤ 80% diameter stenoses on invasive coronary angiography were prospectively included in this study. All patients were scheduled for clinically indicated SPECT myocardial perfusion imaging (MPI) within 3 months and agreed to provide informed consent to participate in quantitative SPECT acquisitions to obtain MBF and MFR values. The primary endpoint was defined as a composite of the major adverse cardiac events (MACE): Cardiac death, myocardial infarction, late revascularization and heart failure or unstable angina-related rehospitalization. ResultsOne hundred and nineteen patients (mean age 57 ± 8 years, 62.2% men) were included in the analysis. The average lumen stenosis of patients was 67.0 ± 10.4%. Over a median follow-up duration of 1408 days (interquartile range 1297-1666 days), 18 patients (15.1%) had MACE. Patients with impaired MFR (MFR < 2) had a significantly higher incidence of events than those with preserved MFR (MFR ≥ 2) in Kaplan-Meier survival analysis (Log-rank = 8.105, P = 0.004), while no significant difference was found between patients with normal relative perfusion and those with relative perfusion abnormalities (log-rank = 0.098, P > 0.05). In a multivariate Cox hazards analysis, the SPECT-derived MFR remained an independent predictor of MACE (HR 0.352, 95% CI 0.145-0.854, P = 0.021). ConclusionsIn a cohort of patients with angiographic intermediate coronary lesions, SPECT-derived MFR was an independent predictor of prognosis.

A list-mode multi-energy window low-count SPECT reconstruction method for isotopes with multiple emission peaks

BackgroundSingle-photon emission computed tomography (SPECT) provides a mechanism to perform absorbed-dose quantification tasks for alpha-particle radiopharmaceutical therapies (alpha-RPTs). However, quantitative SPECT for alpha-RPT is challenging due to the low number of detected counts, the complex emission spectrum, and other image-degrading artifacts. Towards addressing these challenges, we propose a low-count quantitative SPECT reconstruction method for isotopes with multiple emission peaks.MethodsGiven the low-count setting, it is important that the reconstruction method extracts the maximal possible information from each detected photon. Processing data over multiple energy windows and in list-mode (LM) format provide mechanisms to achieve that objective. Towards this goal, we propose a list-mode multi energy window (LM-MEW) ordered-subsets expectation–maximization-based SPECT reconstruction method that uses data from multiple energy windows in LM format and include the energy attribute of each detected photon. For computational efficiency, we developed a multi-GPU-based implementation of this method. The method was evaluated using 2-D SPECT simulation studies in a single-scatter setting conducted in the context of imaging [^{223}Ra]RaCl{_2}, an FDA-approved RPT for metastatic prostate cancer.ResultsThe proposed method yielded improved performance on the task of estimating activity uptake within known regions of interest in comparison to approaches that use a single energy window or use binned data. The improved performance was observed in terms of both accuracy and precision and for different sizes of the region of interest.ConclusionsResults of our studies show that the use of multiple energy windows and processing data in LM format with the proposed LM-MEW method led to improved quantification performance in low-count SPECT of isotopes with multiple emission peaks. These results motivate further development and validation of the LM-MEW method for such imaging applications, including for alpha-RPT SPECT.

Characterization of left ventricular diastolic parameters of gated-single-photon emission computed tomography myocardial perfusion imaging in patients with diabetes and normal myocardial perfusion and systolic function.

Diabetic cardiomyopathy is defined as an independent entity with a specified pathological progression from diastolic dysfunction with preserved ejection fraction to overt heart failure. Myocardial perfusion imaging (MPI) with gated-single-photon emission computed tomography (G-SPECT) has been introduced as a feasible tool to evaluate left ventricular (LV) diastolic function. The aim of this study was to investigate the characteristics of diastolic parameters derived from G-SPECT MPI in diabetic patients compared to patients at very low risk of coronary artery disease (CAD) and with no other CAD risk factors. This cross-sectional study was performed on patients referred to the nuclear medicine department for G-SPECT MPI. Demographic and clinical data, as well as medical history, were extracted from a digital registry system including 4447 patients. Then, two matched groups of patients with only diabetes as cardiac risk factor ( n = 126) and those without any identifiable CAD risk factors ( n = 126) were selected. Diastolic parameters of MPI, including peak filling rate, time to peak filling rate, mean filling rate at the first third of diastole and second peak filling rate, were derived using quantitative software for eligible cases. The mean age of the diabetic and nondiabetic groups was 57.1 ± 14.9 and 56.7 ± 10.6 years, respectively ( P = 0.823). Comparison of quantitative SPECT MPI parameters between the two groups showed a statistically significant difference only in total perfusion deficit scores, whereas none of the functional parameters, including diastolic and dyssynchrony indices and the shape index, were significantly different. There were also no significant differences in diastolic function parameters between diabetes and nondiabetes patients in the age and gender subgroups. Based on the G-SPECT MPI findings, there is a comparable prevalence of diastolic dysfunction in patients with only diabetes as a cardiovascular risk factor and low-risk patients with no cardiovascular risk factors in the setting of normal myocardial perfusion and systolic function.

Activity recovery for differently shaped objects in quantitative SPECT

Objective. The aim was to theoretically and experimentally investigate recovery in SPECT images with objects of different shapes. Furthermore, the accuracy of volume estimation by thresholding was studied for those shapes. Approach. Nine spheres, nine oblate spheroids, and nine prolate spheroids phantom inserts were used, of which the six smaller spheres were part of the NEMA IEC body phantom and the rest of the inserts were 3D-printed. The inserts were filled with 99mTc and 177Lu. When filled with 99mTc, SPECT images were acquired in a Siemens Symbia Intevo Bold gamma camera and when filled with 177Lu in a General Electric NM/CT 870 DR gamma camera. The signal rate per activity (SRPA) was determined for all inserts and represented as a function of the volume-to-surface ratio and of the volume-equivalent radius using VOIs defined according to the sphere dimensions and VOIs defined using thresholding. Experimental values were compared with theoretical curves obtained analytically (spheres) or numerically (spheroids), starting from the convolution of a source distribution with a point-spread function. Validation of the activity estimation strategy was performed using four 3D-printed ellipsoids. Lastly, the threshold values necessary to determine the volume of each insert were obtained. Main results. Results showed that SRPA values for the oblate spheroids diverted from the other inserts, when SRPA were represented as a function of the volume-equivalent radius. However, SRPA values for all inserts followed a similar behaviour when represented as a function of the volume-to-surface ratio. Results for ellipsoids were in agreement with those results. For the three types of inserts the volume could be accurately estimated using a threshold method for volumes larger than 25 ml. Significance. Determination of SRPA independently of lesion or organ shape should decrease uncertainties in estimated activities and thereby, in the long term, be beneficial to patient care.

Quantitative SPECT/CT Parameters in the Assessment of Transthyretin Cardiac Amyloidosis—A New Dimension of Molecular Imaging

Aims: Cardiac transthyretin amyloidosis (ATTR) represents the accumulation of misfolded transthyretin in the heart interstitium. Planar scintigraphy with bone-seeking tracers has long been established as one of the three main steps in the non-invasive diagnosis of ATTR, but lately, single-photon emission computed tomography (SPECT) has gained wide recognition for its abilities to exclude false positive results and offer a possibility for amyloid burden quantitation. We performed a systematic review of the existing literature to provide an overview of the available SPECT-based parameters and their diagnostic performances in the assessment of cardiac ATTR. Methods and Methods: Among the 43 papers initially identified, 27 articles were screened for eligibility and 10 met the inclusion criteria. We summarised the available literature based on radiotracer, SPECT acquisition protocol, analysed parameters and their correlation to planar semi-quantitative indices. Results: Ten articles provided accurate details about SPECT-derived parameters in cardiac ATTR and their diagnostic potential. Five studies performed phantom studies for accurate calibration of the gamma cameras. All papers described good correlation of quantitative parameters to the Perugini grading system. Conclusions: Despite little published literature on quantitative SPECT in the assessment of cardiac ATTR, this method offers good prospects in the appraisal of cardiac amyloid burden and treatment monitoring.

Disappearance of hemichorea as the initial presentation of moyamoya disease after revascularization surgery regardless of residual hypoperfusion evaluated by quantitative N-isopropyl-p-123I-iodoamphetamine SPECT

Background and importanceAlthough hypoperfusion of the basal ganglia or the frontal subcortical matter is suspected, the pathology of chorea in moyamoya disease remains unclarified. Herein, we report a case of moyamoya disease presenting with hemichorea and evaluate pre- and postoperative perfusion using single photon emission computed tomography with N-isopropyl-p-123I-iodoamphetamine (123I-IMP SPECT). Clinical presentationAn 18-year-old woman presented with choreic movement of her left limbs. Magnetic resonance imaging revealed an ivy sign, and 123I-IMP SPECT demonstrated decreased cerebral blood flow (CBF) and cerebral vascular reserve (CVR) values in the right hemisphere. The patient underwent direct and indirect revascularization surgery to improve cerebral hemodynamic impairment. The choreic movements entirely resolved immediately after surgery. Although CBF and CVR values in the ipsilateral hemisphere demonstrated by quantitative SPECT increased, these did not reach the normal values threshold. ConclusionChoreic movement in moyamoya disease may be related to cerebral hemodynamic impairment. Further studies are required to elucidate its pathophysiological mechanisms.

Transient ischaemic dilation ratio thresholds in patients with zero coronary calcium score undergoing exercise or dipyridamole stress SPECT myocardial perfusion imaging using a cadmium-zinc-telluride camera.

Transient ischaemic dilation (TID) is a marker of underlying extensive coronary artery disease (CAD) during myocardial perfusion imaging (MPI). The cut-off for a normal TID ratio (TIDr) value is often derived from a cohort of individuals with no apparent CAD. Varying criteria have been used to define the absence of CAD. We aim to derive TIDr cut-offs using patients with normal MPI and coronary artery calcium (CAC) score of zero, and compare the TIDr obtained from different software packages. We studied 232 patients with zero CAC and normal MPI undergoing exercise or dipyridamole stress using either a 1- or 2-day protocol. All patients were scanned in the supine position with a cadmium-zinc-telluride camera. TIDr was automatically generated using quantitative perfusion SPECT (QPS) software initially, and subsequently using Myometrix for comparison. The TIDr cut-offs calculated using the mean + 2 standard deviation were 1.29 and 1.24 for the 1- and 2-day protocol groups, respectively. In patients undergoing a 2-day protocol, dipyridamole stress resulted in significantly higher mean TIDr when compared to exercise stress (1.07 ± 0.13 vs. 1.01 ± 0.12, P = 0.035). Myometrix-derived TIDr were also significantly lower compared to QPS-derived values for most protocols except for 2-day exercise stress. This study is the first to derive TIDr threshold values using a normal population defined by zero CAC and normal MPI. TIDr was found to vary depending on stress modality, protocol as well as the software used.

177Lu SPECT imaging in the presence of 90Y: does 90Y degrade image quantification? a simulation study

This work aims to investigate the accuracy of quantitative SPECT imaging of 177Lu in the presence of 90Y, which occurs in dual-isotope radiopharmaceutical therapy (RPT) involving both isotopes. We used the GATE Monte Carlo simulation toolkit to conduct a phantom study, simulating spheres filled with 177Lu and 90Y placed in a cylindrical water phantom that was also filled with activity of both radionuclides. We simulated multiple phantom configurations and activity combinations by varying the location of the spheres, the concentrations of 177Lu and 90Y in the spheres, and the amount of background activity. We investigated two different scatter window widths to be used with triple energy window (TEW) scatter correction. We also created multiple realizations of each configuration to improve our assessment, leading to a total of 540 simulations. Each configuration was imaged using a simulated Siemens SPECT camera. The projections were reconstructed using the standard 3D OSEM algorithm, and errors associated with 177Lu activity quantification and contrast-to-noise ratios (CNRs) were determined. In all configurations, the quantification error was within ± 6% of the no-90Y case, and we found that quantitative accuracy may slightly improve when 90Y is present because of reduction of errors associated with TEW scatter correction. The CNRs were not significantly impacted by the presence of 90Y, but they were increased when a wider scatter window width was used for TEW scatter correction. The width of the scatter windows made a small but statistically significant difference of 1%–2% on the recovered 177Lu activity. Based on these results, we can conclude that activity quantification of 177Lu and lesion detectability is not degraded by the presence of 90Y.

Diagnostic value of quantitative myocardial blood flow assessment by NaI(Tl) SPECT in detecting significant stenosis: a prospective, multi-center study

ObjectivesThe aim of this prospective multi-center study was to investigate the diagnostic value of myocardial blood flow (MBF) quantification using NaI(Tl)-based single-photon emission computed tomography (SPECT) for determining coronary artery disease (CAD) defined by quantitative coronary angiography (QCA). BackgroundAbsolute quantitation of MBF and myocardial flow reserve (MFR) using SPECT is clinically feasible; however, whether flow quantification using NaI(Tl) SPECT is superior to commonly performed SPECT myocardial perfusion imaging (MPI) in determining CAD has not been evaluated. MethodsPatients with suspected or known CAD underwent pharmacological stress/rest dynamic SPECT imaging and routine SPECT MPI followed by QCA. Obstructive disease was defined as ≥ 50% reduction in luminal diameter on QCA. ResultsOne hundred fifty-four patients (462 vessels) were included in the analysis. Obstructive CAD was detected in 76/154 patients (49.4%) and 112/462 vessels (24.2%). Optimal cut-off values were 1.86 mL/min/g for stress MBF and 1.95 for MFR, respectively. Stress MBF and MFR were more sensitive than MPI in both individual patients (stress MBF vs MPI: 81.6% vs 51.3%; MFR vs MPI: 72.4% vs 51.3%) and in coronary vascular regions (stress MBF vs MPI: 78.6% vs 31.3%; MFR vs MPI: 75.9% vs 31.3%; all P < .01). In receiver operating characteristic curve analysis, quantification revealed a significantly greater area under the curve than MPI at the patient (stress MBF vs MPI: 0.761 vs 0.641; MFR vs MPI: 0.770 vs 0.641) and the vessel (stress MBF vs MPI: 0.745 vs 0.613; MFR vs MPI: 0.756 vs 0.613; all P < .05) levels. Integrating quantitative SPECT measures with MPI significantly increased the area under the curve and improved the discriminatory and reclassification capacity. ConclusionFlow quantification using NaI(Tl) SPECT provides superior sensitivity and discriminatory capacity to MPI in detecting significant stenosis.Clinical trial registration NCT03637725.

QCard-NM: Developing a semiautomatic segmentation method for quantitative analysis of the right ventricle in non-gated myocardial perfusion SPECT imaging

BackgroundRecent studies have shown that the right ventricular (RV) quantitative analysis in myocardial perfusion imaging (MPI) SPECT can be beneficial in the diagnosis of many cardiopulmonary diseases. This study proposes a new algorithm for right ventricular 3D segmentation and quantification.MethodsThe proposed Quantitative Cardiac analysis in Nuclear Medicine imaging (QCard-NM) algorithm provides RV myocardial surface estimation and creates myocardial contour using an iterative 3D model fitting method. The founded contour is then used for quantitative RV analysis. The proposed method was assessed using various patient datasets and digital phantoms. First, the physician’s manually drawn contours were compared to the QCard-NM RV segmentation using the Dice similarity coefficient (DSC). Second, using repeated MPI scans, the QCard-NM’s repeatability was evaluated and compared with the QPS (quantitative perfusion SPECT) algorithm. Third, the bias of the calculated RV cavity volume was analyzed using 31 digital phantoms using the QCard-NM and QPS algorithms. Fourth, the ability of QCard-NM analysis to diagnose coronary artery diseases was assessed in 60 patients referred for both MPI and coronary angiography.ResultsThe average DSC value was 0.83 in the first dataset. In the second dataset, the coefficient of repeatability of the calculated RV volume between two repeated scans was 13.57 and 43.41 ml for the QCard-NM and QPS, respectively. In the phantom study, the mean absolute percentage errors for the calculated cavity volume were 22.6% and 42.2% for the QCard-NM and QPS, respectively. RV quantitative analysis using QCard-NM in detecting patients with severe left coronary system stenosis and/or three-vessel diseases achieved a fair performance with the area under the ROC curve of 0.77.ConclusionA novel model-based iterative method for RV segmentation task in non-gated MPI SPECT is proposed. The precision, accuracy, and consistency of the proposed method are demonstrated by various validation techniques. We believe this preliminary study could lead to developing a framework for improving the diagnosis of cardiopulmonary diseases using RV quantitative analysis in MPI SPECT.

CT-free quantitative SPECT for automatic evaluation of %thyroid uptake based on deep-learning

PurposeQuantitative thyroid single-photon emission computed tomography/computed tomography (SPECT/CT) requires computed tomography (CT)-based attenuation correction and manual thyroid segmentation on CT for %thyroid uptake measurements. Here, we aimed to develop a deep-learning-based CT-free quantitative thyroid SPECT that can generate an attenuation map (μ-map) and automatically segment the thyroid.MethodsQuantitative thyroid SPECT/CT data (n = 650) were retrospectively analyzed. Typical 3D U-Nets were used for the μ-map generation and automatic thyroid segmentation. Primary emission and scattering SPECTs were inputted to generate a μ-map, and the original μ-map from CT was labeled (268 and 30 for training and validation, respectively). The generated μ-map and primary emission SPECT were inputted for the automatic thyroid segmentation, and the manual thyroid segmentation was labeled (280 and 36 for training and validation, respectively). Other thyroid SPECT/CT (n = 36) and salivary SPECT/CT (n = 29) were employed for verification.ResultsThe synthetic μ-map demonstrated a strong correlation (R2 = 0.972) and minimum error (mean square error = 0.936 × 10−4, %normalized mean absolute error = 0.999%) of attenuation coefficients when compared to the ground truth (n = 30). Compared to manual segmentation, the automatic thyroid segmentation was excellent with a Dice similarity coefficient of 0.767, minimal thyroid volume difference of − 0.72 mL, and a short 95% Hausdorff distance of 9.416 mm (n = 36). Additionally, %thyroid uptake by synthetic μ-map and automatic thyroid segmentation (CT-free SPECT) was similar to that by the original μ-map and manual thyroid segmentation (SPECT/CT) (3.772 ± 5.735% vs. 3.682 ± 5.516%, p = 0.1090) (n = 36). Furthermore, the synthetic μ-map generation and automatic thyroid segmentation were successfully performed in the salivary SPECT/CT using the deep-learning algorithms trained by thyroid SPECT/CT (n = 29).ConclusionCT-free quantitative SPECT for automatic evaluation of %thyroid uptake can be realized by deep-learning.

Detecting obstructive coronary artery disease with machine learning: rest-only gated single photon emission computed tomography myocardial perfusion imaging combined with coronary artery calcium score and cardiovascular risk factors.

The rest-only single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has low diagnostic performance for obstructive coronary artery disease (CAD). Coronary artery calcium score (CACS) is strongly associated with obstructive CAD. The aim of this study was to investigate the performance of rest-only gated SPECT MPI combined with CACS and cardiovascular risk factors in diagnosing obstructive CAD through machine learning (ML). We enrolled 253 suspected CAD patients who underwent the 1-stop rest-only SPECT MPI and computed tomography (CT) scan due to stress test-related contraindications. Myocardial perfusion and wall motion were assessed using quantitative perfusion SPECT + quantitative gated SPECT (QPS + QGS) automated quantification software. The Agatston algorithm was used to calculate CACS. The clinical data of patients, including cardiovascular risk factors, were collected. Based on feature selection and clinical experience, 8 factors were identified as modeling variables. Subsequently, patients were divided randomly into 2 groups: the training (70%) and test (30%) groups. The performance of 8 supervised ML algorithms was evaluated in the training and test groups. Obstructive CAD was diagnosed by coronary angiography in 94 (37.2%, 94/253) patients. In the training group, the area under the receiver operator characteristic (ROC) curve (AUC) of the random forest was the highest, and the AUCs of Logistic, extreme gradient boosting (XGBoost), support vector machine (SVM), and adaptive boosting (AdaBoost) were all above 0.9. In the test group, the AUC of recursive partitioning and regression trees (Rpart) was the highest (0.911). Rpart and Naïve Bayes had the highest accuracy (0.840). Rpart had a sensitivity and specificity of 0.851 and 0.821, respectively; Naïve Bayes had a sensitivity and specificity of 0.809 and 0.893, respectively. Next was Logistic, with an accuracy of 0.827, a sensitivity of 0.872, and a specificity of 0.750. The random forest and XGBoost algorithms also had high accuracy, which was 0.813 for each algorithm. Rest-only SPECT MPI combined with CACS and cardiovascular risk factors using an ML algorithm to detect obstructive CAD is feasible. Among the algorithms validated in the test group, Rpart, Naïve Bayes, XGBoost, Logistic, and random forest are all highly accurate for diagnosing obstructive CAD. The application of ML in resting MPI and CACS may be used for screening obstructive CAD.