Single Photon Emission Computed Tomography Studies Research Articles

Measurable transitions during seizures in intracranial EEG: A stereoelectroencephalography and SPECT study

ObjectiveIctal Single Photon Emission Computed Tomography (SPECT) and stereo-electroencephalography (SEEG) are diagnostic techniques used for the management of patients with drug-resistant focal epilepsies. While hyperperfusion patterns in ictal SPECT studies reveal seizure onset and propagation pathways, the role of ictal hypoperfusion remains poorly understood. The goal of this study was to systematically characterize the spatio-temporal information flow dynamics between differently perfused brain regions using stereo-EEG recordings. MethodsWe identified seizure-free patients after resective epilepsy surgery who had prior ictal SPECT and SEEG investigations. We estimated directional connectivity between the epileptogenic-zone (EZ), non-resected areas of hyperperfusion, hypoperfusion, and baseline perfusion during the interictal, preictal, ictal, and postictal periods. ResultsCompared to the background, we noted significant information flow (1) during the preictal period from the EZ to the baseline and hyperperfused regions, (2) during the ictal onset from the EZ to all three regions, and (3) during the period of seizure evolution from the area of hypoperfusion to all three regions. ConclusionsHypoperfused brain regions were found to indirectly interact with the EZ during the ictal period. SignificanceOur unique study, combining intracranial electrophysiology and perfusion imaging, presents compelling evidence of dynamic changes in directional connectivity between brain regions during the transition from interictal to ictal states.

Exploring the potential of radiolabeled duramycin as an infection imaging probe.

The continuous pursuit of designing an ideal infection imaging agent is a crucial and ongoing endeavor in the field of biomedical research. Duramycin, an antimicrobial peptide exerts its antimicrobial action on bacteria by specific recognition of phosphatidylethanolamine (PE) moiety present on most bacterial membranes, particularly Escherichia coli (E. coli). E. coli membranes contain more than 60% PE. Therefore, duramycin is an attractive candidate for the formulation of probes for in situ visualization of E. coli driven focal infections. The aim of the present study is to develop 99m Tc labeled duramycin as a single-photon emission computed tomography (SPECT)-based agent to image such infections. Duramycin was successfully conjugated with a bifunctional chelator, hydrazinonicotinamide (HYNIC). PE specificity of HYNIC-duramycin was confirmed by a dye release assay on PE-containing model membranes. Radiolabeling of HYNIC-duramycin with 99m Tc was performed with consistently high radiochemical yield (>90%) and radiochemical purity (>90%). [99m Tc]Tc-HYNIC-duramycin retained its specificity for E. coli, in vitro. SPECT and biodistribution studies showed that the tracer could specifically identify E. coli driven infection at 3 h post injection. While 99m Tc-labeled duramycin is employed for monitoring early response to cancer therapy and cardiotoxicity, the current studies have confirmed, for the first time, the potential of utilizing 99m Tc labeled duramycin as an imaging agent for detecting bacteria. Its application in imaging PE-positive bacteria represents a novel and promising advancement.

Applications of PET and SPECT in Patients with Autism Spectrum Disorder.

Autism spectrum disorder (ASD) consists of neurological development disorders that manifest before three years of age and affect social interactions, markedly restricting range of interests and activities, often associated with some degree of intellectual disability. Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are non-invasive imaging tools to investigate the function of the brain in vivo. SPECT and PET studies exploring rCBF and brain glucose metabolism in patients with ASD have been performed, providing important insights into the brain regions involved in ASD. Abnormalities in serotonergic, dopaminergic, GABAergic, cholinergic, and glutamatergic systems have been suggested to contribute to the observed distorted brain circuitry associated with ASD. However, the specificity of such abnormalities needs to be fully clarified because schizophrenia and other psychiatric diseases have been shown to present with comparable changes in neurotransmitter systems. Neuroinflammation could also play a role in the development of autism. Therefore, ASD is a complicated process involving a number of factors. It is mandatory to perform more research studies to determine the molecular cornerstone of ASD and to improve our comprehension of the clinical correlates of ASD.

Practice recommendation for measuring washout rates in 123I-BMIPP fatty acid images

The purpose of this practice recommendation is to specifically identify the critical steps involved in performing and interpreting 123I-β-methyl-iodophenyl-pentadecanoic acid (BMIPP) single-photon emission computed tomography (SPECT) and measurement of washout rate (WR) from the heart. This document will cover backgrounds, patient preparation, testing procedure, visual image interpretation, quantitation methods using planar and SPECT studies, and reporting of WR. The pitfall and some tips for the calculation of 123I-BMIPP WR are also included. The targets of global and regional WR calculation include ischemic heart disease, cardiomyopathy, heart failure, and triglyceride deposit cardiomyovasculopathy, an emerging rare heart disease.

Identifying and troubleshooting the pitfalls of ictal/interictal brain perfusion SPECT studies.

Epilepsy is a prevalent condition, and surgical intervention can benefit patients with refractory seizures. Single photon emission computed tomography (SPECT) using 99mTc-HMPAO or 99mTc-ECD provides assessment of regional cerebral blood flow and is the primary non-invasive approach for imaging brain perfusion in ictal and interictal states. Ictal/interictal SPECT is valuable in localising epileptogenic foci, particularly when MRI and electroencephalography are negative. However, to obtain accurate images reflecting brain perfusion in both states, meticulous preparation of the patient, timely radiotracer injection and close coordination between neurology and nuclear medicine teams are essential. Tracers also have inherent limitations, and patients may present with coexisting brain pathologies for which coregistration of SPECT images with MRI is recommended to improve diagnostic accuracy. Inconclusive SPECT findings may require repeating the exam or considering additional investigations. A comprehensive approach, considering various factors, is crucial for accurate interpretation of SPECT studies in presurgical epilepsy evaluations. This article provides a summary of the organisation and key challenges involved in conducting ictal/interictal SPECT studies, covering the entire process from a patient's hospital arrival to the integration of results within their presurgical pathway and using our experience of 182 patients over 10 years.

Ex-SPECTing Success: predictors of successful SPECT radiotracer injection during pre-surgical video-EEG admissions.

To determine predictors of successful ictal Single Photon Emission Computed Tomography (SPECT) injections during Epilepsy Monitoring Unit (EMU) admissions for patients undergoing presurgical evaluation for drug resistant focal epilepsy. In this retrospective study, consecutive EMU admissions were analysed at a single centre between 2019-2021. All seizures that occurred during the admission were reviewed. 'Injectable seizures' occurred during hours when the radiotracer was available. EMU-level data were analysed to identify factors predictive of an EMU admission with a successful SPECT injection (successful admission). Seizure-level data were analysed to identify factors predictive of an 'injectable seizure' receiving a SPECT injection during the ictal phase (successful injection). A multivariate generalised linear model was used to identify predictive variables. 125 EMU admissions involving 103 patients (median 37 years, IQR27.0-45.5) were analysed. 38.8% of seizures that were eligible for SPECT (n=134) were successfully injected; this represented 17.4% of all seizures (n=298) that occurred during admission. Unsuccessful admissions were most commonly due to a lack of seizures during EMU-SPECT (19.3%) or no 'injectable seizures' (62.3%). Successful EMU-SPECT was associated with baseline seizure frequency >1 per week (95%CI 2.1-3.0, p <0.001) and focal PET hypometabolism (95%CI 2.0-3.7, p <0.001). On multivariate analysis, the only factor associated with successful injection was patients being able to indicate they were having a seizure to staff (95%CI 1.0-4.4, p=0.038). Completing a successful ictal SPECT study remains challenging. Baseline seizure frequency of >1 per-week, a PET hypometabolic focus and a patient's ability to indicate seizure onset were identified as predictors of success. These findings may assist EMUs in optimising their SPECT protocols, patient selection, and resource allocation.

Neuroimaging Correlates of Treatment Response to Transcranial Magnetic Stimulation in Bipolar Depression: A Systematic Review.

Transcranial magnetic stimulation (TMS) has become a promising strategy for bipolar disorder (BD). This study reviews neuroimaging findings, indicating functional, structural, and metabolic brain changes associated with TMS in BD. Web of Science, Embase, Medline, and Google Scholar were searched without any restrictions for studies investigating neuroimaging biomarkers, through structural magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), functional MRI (fMRI), magnetic resonance spectroscopy (MRS), positron emission tomography (PET), and single photon emission computed tomography (SPECT), in association with response to TMS in patients with BD. Eleven studies were included (fMRI = 4, MRI = 1, PET = 3, SPECT = 2, and MRS = 1). Important fMRI predictors of response to repetitive TMS (rTMS) included higher connectivity of emotion regulation and executive control regions. Prominent MRI predictors included lower ventromedial prefrontal cortex connectivity and lower superior frontal and caudal middle frontal volumes. SPECT studies found hypoconnectivity of the uncus/parahippocampal cortex and right thalamus in non-responders. The post-rTMS changes using fMRI mostly showed increased connectivity among the areas neighboring the coil. Increased blood perfusion was reported post-rTMS in PET and SPECT studies. Treatment response comparison between unipolar depression and BD revealed almost equal responses. Neuroimaging evidence suggests various correlates of response to rTMS in BD, which needs to be further replicated in future studies.

Ictal Single Photon Emission Computed Tomography (SPECT) In Patients with Focal Aware Seizure without Ictal Electroencephalographic Changes: A Single Center Experience (P2-1.012)

<h3>Objective:</h3> N/A <h3>Background:</h3> There is currently limited literature on the localization value of ictal SPECT tracer injection during patient-reported typical focal aware seizures (auras) that lack electrographic changes. One study reported that ictal SPECT studies in isolated auras lack reliability, with concordant localization with the seizure onset zone obtained in 5%, and lateralization in 35% of cases. In another study, localizing information of self-injection of ictal SPECT was better in three patients and obviated the need for intracranial monitoring in one patient. We present a study in which tracer injection was administered for patient-reported typical focal aware seizures, where the subsequent analysis of ictal and interictal SPECT helped inform further management. <h3>Design/Methods:</h3> We performed a retrospective review of cases who underwent ictal SPECT between 2020 to 2022 at University of Kentucky hospital. Cases with radiotracer injection during patient-reported auras lacking electrographic changes were identified. Timing of injection from onset of reported aura, hyperperfusion changes on ictal SPECT, and the outcome of imaging on further management of refractory epilepsy were noted. <h3>Results:</h3> 20 patients underwent ictal SPECT, of which 7 met our inclusion criteria. None of the 7 cases had electrographic correlate with aura on scalp EEG. Time of tracer injection ranged from 1–17 seconds following onset of aura. The ictal SPECT changes correctly localized the seizure onset zone in five patients. This was followed by intracranial monitoring and subsequent temporal lobectomy in three patients, interventricular ablation of epileptogenic focus in one patient, and Responsive Neurostimulation implant in one patient. One patient was managed medically, and one is ongoing pre-surgical evaluation. <h3>Conclusions:</h3> Ictal SPECT with radiotracer injection during typical focal aware seizures (patient reported auras) without ictal electrographic changes is helpful in the localization of the seizure onset zone. Additional studies with larger sample size and outcome information are needed to assess accuracy of localization. <b>Disclosure:</b> Dr. Pervin has nothing to disclose. Dr. Khan has received personal compensation for serving as an employee of University of Kentucky. Dr. Clay has nothing to disclose. Riham El Khouli has nothing to disclose. Dr. Mirza has nothing to disclose. Dr. Mathias has received research support from My Epilepsy Society Non Profit Organization.

Pharmacodynamic effect of gabapentin on central nervous system in patients with chronic low back pain: a [99mTc]Tc-ECD SPECT study

BackgroundGabapentin is an effective therapeutic alternative for chronic low back pain, indicated in several guidelines for treating neuropathic pain as first-line medication. This study aimed to describe the pharmacodynamics of...

Incidental Tc-99m MDP Uptake in Cortical-subcortical Parietotemporal Cerebral Area in a Patient with a History of Recent Ischemic Cerebrovascular Event who Underwent Whole-body Bone Scan.

The authors present Tc-99m methylene diphosphonate (MDP) uptake in the right parietotemporal area at whole-body bone scan (WBBS) in 75 years male patient with prostate adenocarcinoma Gleason score 3+4 (pT2N0Mx). No residual or metastatic disease was detected in the patient's Gallium-68 prostate-specific membrane antigen positron emission tomography/computed tomography four months before WBBS. The patient had undetectable prostate-specific antigen levels and underwent WBBS to restage prostate cancer due to equivocal findings in previous WBBS. Current WBBS planar views revealed heterogeneous Tc-99m MDP uptake in the right parietotemporal area and the sphenoid bone in addition to equivocal uptake on the lower lumbar vertebrae. Single-photon emission computed tomography study to identify the MDP-avid lesion on the right cranial area revealed heterogeneous Tc-99m MDP uptake in the right parietotemporal area and sphenoid bone. The patient had a history of transsphenoidal surgery for a hypophyseal tumor two years ago and a recent cerebrovascular event (CVE). Diffusion-weighted magnetic resonance imaging revealed a cortical-subcortical patchy area of restricted diffusion in the parietotemporal region compatible with acute ischemia. Heterogeneous Tc-99m MDP uptake in the right parietotemporal area was attributed to recent CVE and secondary vascular-tissue change-related dystrophic calcification.

The diagnostic value of ictal SPECT-A retrospective, semiquantitative monocenter study.

Ictal single photon emission computed tomography (SPECT) can be used as an advanced diagnostic modality to detect the seizure onset zone in the presurgical evaluation of people with epilepsy. In addition to visual assessment (VSA) of ictal and interictal SPECT images, postprocessing methods such as ictal-interictal SPECT analysis using SPM (ISAS) can visualize regional ictal blood flow differences. We aimed to evaluate and differentiate the diagnostic value of VSA and ISAS in the Bonn cohort. We included 161 people with epilepsy who underwent presurgical evaluation at the University Hospital Bonn between 2008 and 2020 and received ictal and interictal SPECT and ISAS. We retrospectively assigned SPECT findings to one of five categories according to their degree of concordance with the clinical focus hypothesis. Seizure onset zones could be identified more likely on a sublobar concordance level by ISAS than by VSA (31% vs. 19% of cases; OR=1.88; 95% Cl [1.04, 3.42]; P=0.03). Both VSA and ISAS more often localized a temporal seizure onset zone than an extratemporal one. Neither VSA nor ISAS findings were predicted by the latency between seizure onset and tracer injection (P=0.75). In people who underwent successful epilepsy surgery, VSA and ISAS indicated the correct resection site in 54% of individuals, while MRI and EEG showed the correct resection localization in 96% and 33% of individuals, respectively. It was more likely to become seizure-free after epilepsy surgery if ISAS or VSA had been successful. There was no MR-negative case with successful surgery, indicating that ictal SPECT is more useful for confirmation than for localization. The results of the most extensive clinical study of ictal SPECT to date allow an assessment of the diagnostic value of this elaborate examination and emphasize the importance of postprocessing routines.

Practice Recommendation for Measuring Washout Rates in 123I-BMIPP Fatty Acid Images.

The purpose of this practice recommendation is to specifically identify the critical steps involved in performing and interpreting 123I-β-methyl-iodophenyl-pentadecanoic acid (BMIPP) single-photon emission computed tomography (SPECT) and measurement of washout rate (WR) from the heart. This document will cover backgrounds, patient preparation, testing procedure, visual image interpretation, quantitation methods using planar and SPECT studies, and reporting of WR. The pitfall and some tips for the calculation of 123I-BMIPP WR are also included. The targets of global and regional WR calculation include ischemic heart disease, cardiomyopathy, heart failure, and triglyceride deposit cardiomyovasculopathy, an emerging rare heart disease.

99m-Tc TRODAT Single-Photon Emission Computerized Tomography Scan Image Compression using Singular Value Decomposition.

The objective of the study was to compress 99m-Tc TRODAT single-photon emission computerized tomography (SPECT) scan image using Singular Value Decomposition (SVD) into an acceptable compressed image and then calculate the compression factor. The SVD of every image from the image dataset of 2256 images (of forty-eight 99m-Tc TRODAT SPECT studies [48 studies X 47 trans-axial images = 2256 trans-axial images]) was computed and after truncating singular values smaller than a threshold, the compressed image was reconstructed. The SVD computation time and percentage compression achieved were calculated for each image. Two nuclear medicine physicians visually compared compressed image with its original image, and labeled it as either acceptable or unacceptable. Compressed image having loss of clinical details or presence of compression artifact was labeled unacceptable. The quality of compressed image was also assessed objectively using the following image quality metrics: Error, structural similarity (SSIM), brightness, global contrast factor (GCF), contrast per pixel (CPP), and blur. We also compared the TRODAT uptake in basal ganglia estimated from the compressed image and original image. Nuclear Medicine Physician labeled each image acceptable, as they found compressed image identical to its original image. The values of brightness, GCF, CPP, and blur metrics show that compressed images are less noisy, brighter, and sharper than its original image. The median values of error (0.0006) and SSIM (0.93) indicate that the compressed images were approximately identical to its original image. In 39 out of 48 studies, the percentage difference in TRODAT uptake (in basal ganglia from compressed and original image) was negligible (approximately equal to zero). In remaining 9 studies, the maximum percentage difference was 13%. The SVD computation time and percentage compression achieved for a TRODAT study were 0.17398 s and up to 54.61%, respectively. The compression factor up to 54.61% was achieved during 99m-Tc TRODAT SPECT scan image compression using SVD, for an acceptable compressed image.

Structural Cerebral Network Differences in Prodromal Alzheimer’s Disease and Prodromal Dementia with Lewy Bodies

Introduction: Alzheimer’s disease (AD) and dementia with Lewy bodies (DLB) have long prodromal phases without dementia. However, the patterns of cerebral network alteration in this early stage of the disease remain to be clarified. Method: Participants were 48 patients with mild cognitive impairment (MCI) due to AD (MCI-AD), 18 patients with MCI with DLB (MCI with Lewy bodies: MCI-LB), and 23 healthy controls who underwent a 1.5-Tesla magnetic resonance imaging scan. Cerebral networks were extracted from individual T1-weighted images based on the intracortical similarity, and we estimated the differences of network metrics among the three diagnostic groups. Results: Whole-brain analyses for degree, betweenness centrality, and clustering coefficient images were performed using SPM8 software. The patients with MCI-LB showed significant reduction of degree in right putamen, compared with healthy subjects. The MCI-AD patients showed significant lower degree in left insula and bilateral posterior cingulate cortices compared with healthy subjects. There were no significant differences in small-world properties and in regional gray matter volume among the three groups. Conclusions: We found the change of degree in the patients with MCI-AD and with MCI-LB, compared with healthy controls. These findings were consistent with the past single-photon emission computed tomography studies focusing on AD and DLB. The disease-related difference in the cerebral neural network might provide an adjunct biomarker for the early detection of AD and DLB.

Striatal Dopamine Transporter Availability is Associated with Sleep Disturbance among Patients with Bipolar I Disorder: A Single-photon Emission Computed Tomography Study Using [99mTc] TRODAT-1.

Bipolar disorder (BD) is characterized by the poor sleep quality. Whether the striatal dopamine transporter (DAT) availability is related to sleep quality among patients with BD is unclear. Fifty-three euthymic patients with BD (24 BD-I and 29 BD-II) and sixty-eight healthy controls were enrolled. The Chinese Version of the Pittsburgh Sleep Quality Index (PSQI) was used, and the availability of DAT was assessed by single-photon emission computed tomography (SPECT) using [99mTc] TRODAT-1. The sleep disturbance component of the PSQI was significantly associated with the level of DAT availability among patients with BD. The striatal dopaminergic activity that contributes to resilience to adversity was associated with sleep pattern among patients with BD.

A Comparative Study of Regional Cerebral Blood Flow Asymmetry Index in Stroke Patients with or without Poststroke Depression Using 99m Tc-ECD Single-Photon Emission Computed Tomography.

Introduction  Stroke is a major cause of death and disability around the globe. The development of depression following a stroke further increases the disability and impairs functional recovery. In recent decades, despite the advancement in structural and nuclear medicine imaging, the pathophysiologic basis of poststroke depression (PSD) is not well understood. Etiopathogenesis of PSD is multifactorial and afflictions of the frontal lobe, hippocampus, limbic region, and basal ganglia projections are implicated. Aim  The aim of this study was to assess the regional cerebral blood flow (rCBF) using 99m Tc-ethyl cysteinate dimer single-photon emission computed tomography (SPECT) in patients with (PSD + ) or without PSD (PSD–). Materials and Methods  To evaluate the hemispheric asymmetry, the percentage of asymmetry index (AI) was calculated for frontal, temporal, parietal, occipital, putamen, caudate, and thalamic regions of brain and compared between PSD+ and PSD–. The correlation between AIs over the different brain regions was also established in patients of PSD+ and PSD–. Our study cohort included 122 patients between 6 weeks and 1 year of stroke. Depression was present in 52 (42.6%) patients, assessed by hospital anxiety and depression scale (HADS) and general health questionnaire-28 items (GHQ-28) scale. The 28 patients with PSD+ and 18 PSD– gave consent for SPECT study. Results  Our results are based on 46 patients who underwent SPECT study. In patients with PSD+ and PSD–, the HADS and GHQ-28 scores were 8.93 ± 2.77 vs. 3.94 ± 2.15 ( p  = 0.001) and 40.96 ± 9.48 vs. 17.72 ± 5.38 ( p  = 0.001), respectively. A significant difference in rCBF AI was found in the temporal lobe ( p  = 0.03) between patients of PSD+ and PSD–. On logistic regression analysis, the odds ratio of rCBF AI for temporal lobe was 0.89 (95% confidence interval [CI]: 0.80–0.99; p  = 0.04) and caudate nucleus was 0.85 (95% CI: 0.73–0.98; p  = 0.03), which were statistically significant. PSD correlated with AI in temporal region ( r  = –0.03; p  = 0.03) but did not show significant correlation with other regions of brain between PSD+ and PSD–. Conclusion  The presence of temporal lobe rCBF AI on SPECT is significantly associated with PSD. This may reflect the dysfunction of the limbic system and contribute to the occurrence of PSD.

Real-world validation of fractional flow reserve computed tomography in patients with stable angina: Results from the prospective AFFECTS trial

BackgroundFractional flow reserve computed tomography (FFRct) allows for non-invasive assessment of hemodynamically significant coronary artery disease (CAD). Real-world data regarding the diagnostic performance of FFRct is scarce. We aim to validate the diagnostic performance of FFRct against invasive coronary angiography (ICA) in patients with stable angina and an abnormal single photon emission computed tomography (SPECT) study. MethodsThis prospective, single-cohort, real-world study enrolled consecutive adult patients with stable angina and an abnormal SPECT study who were referred for ICA. Prior to ICA, FFRct analysis was performed. Sensitivity and specificity of FFRct were evaluated at the patient and vessel level against ICA. Physician intuition-based diagnosis of hemodynamically significant CAD was also documented prior to ICA. ResultsA total of 66 patients were enrolled; 10 were excluded due to protocol deviation or missing studies. FFRct achieved 95% sensitivity and 83% specificity at the patient level, and 78% sensitivity and 88% specificity at the vessel level. FFRct was most accurate in the left circumflex artery (sensitivity 83%, specificity 92%) and the least in the left anterior descending artery (80% sensitivity, 78% specificity). FFRct identified hemodynamically significant CAD more accurately than physician intuition (sensitivity 95% vs 84%; specificity 83% vs 46%). If physicians had been unblinded to FFRct, ICA may have been avoided in up to 53% of patients. ConclusionWe performed a real-world study to validate the diagnostic performance of FFRct against gold-standard invasive imaging. FFRct has high sensitivity and specificity for the diagnosis of hemodynamically significant CAD in intermediate-to-high risk patients.

Predictive value of incidental right ventricular abnormalities identified on SPECT for mortality and pulmonary hypertension

BackgroundThe clinical significance of incidentally found RV abnormalities on low-risk SPECT studies is not well-defined. The objective of this study was to determine the predictive value of incidental right ventricular (RV) abnormalities identified on single photon emission computed tomography (SPECT) scans for mortality and pulmonary hypertension (PH). MethodsWe retrospectively analyzed all low-risk SPECT studies in patients without known coronary artery or pulmonary vascular disease, performed at our institution, from 2007-2020. Adjusted Cox proportional hazards models were used to evaluate the association between incidental RV abnormalities on low-risk SPECT studies and outcomes. ResultsOf the 4761 patients included in the analysis, mortality events were present in 494, and echocardiographic PH was present in 619. Incidental RV abnormalities on low-risk SPECT studies were significantly and independently associated with all-cause mortality (HR = 1.41, CI [1.07-1.86], P = 0.0152) and echocardiographic PH (HR = 2.06, CI [1.64-2.60], P < 0.0001). ConclusionsThese data suggest incidental RV abnormalities found on low-risk SPECT imaging studies are significantly and independently associated with increased mortality and risk of developing echocardiographic PH, and could identify high-risk patients for closer monitoring and additional diagnostic testing.

Accuracy and Reproducibility of Myocardial Blood Flow Quantification by Single Photon Emission Computed Tomography Imaging in Patients With Known or Suspected Coronary Artery Disease.

Single photon emission computed tomography (SPECT) has limited ability to identify multivessel and microvascular coronary artery disease. Gamma cameras with cadmium zinc telluride detectors allow the quantification of absolute myocardial blood flow (MBF) and myocardial flow reserve (MFR). However, evidence of its accuracy is limited, and of its reproducibility is lacking. We aimed to validate 99mTc-sestamibi SPECT MBF and MFR using standard and spline-fitted reconstruction algorithms compared with 13N-ammonia positron emission tomography in a cohort of patients with known or suspected coronary artery disease and to evaluate the reproducibility of this technique. Accuracy was assessed in 34 participants who underwent dynamic 99mTc-sestamibi SPECT and 13N-ammonia positron emission tomography and reproducibility in 14 participants who underwent 2 99mTc-sestamibi SPECT studies, all within 2 weeks. A rest/pharmacological stress single-day SPECT protocol was performed. SPECT images were reconstructed using a standard ordered subset expectation maximization (OSEM) algorithm with (N=21) and without (N=30) application of spline fitting. SPECT MBF was quantified using a net retention kinetic model' and MFR was derived as the stress/rest MBF ratio. SPECT global MBF with splines showed good correlation with 13N-ammonia positron emission tomography (r=0.81, P<0.001) and MFR estimates (r=0.74, P<0.001). Correlations were substantially weaker for standard reconstruction without splines (r=0.61, P<0.001 and r=0.34, P=0.07, for MBF and MFR, respectively). Reproducibility of global MBF estimates with splines in paired SPECT scans was good (r=0.77, P<0.001), while ordered subset expectation maximization without splines led to decreased MBF (r=0.68, P<0.001) and MFR correlations (r=0.33, P=0.3). There were no significant differences in MBF or MFR between the 2 reproducibility scans independently of the reconstruction algorithm (P>0.05 for all). MBF and MFR quantification using 99mTc-sestamibi cadmium zinc telluride SPECT with spatiotemporal spline fitting improved the correlation with 13N-ammonia positron emission tomography flow estimates and test/retest reproducibility. The use of splines may represent an important step toward the standardization of SPECT flow estimation.

Recovery of Cortical Neurotransmitter Receptor Function and Its Impact on Cognitive Improvement after Indirect Revascularization Surgery Alone for Adult Patients with Ischemic Moyamoya Disease: 123I-Iomazenil Single-Photon Emission Computed Tomography Study

Brain 123I-iomazenil single-photon emission computed tomography (SPECT) can assess the distribution of the binding potential of central benzodiazepine receptors in the cerebral cortex. This binding potential may reflect neuronal function in viable tissues. The present prospective study using brain 123I-iomazenil SPECT aimed to determine whether improvements in cognitive function after indirect revascularization surgery alone are associated with postoperative recovery in neurotransmitter receptor function in the affected cerebral hemisphere among adult patients with moyamoya disease accompanied by ischemic presentation due to misery perfusion. Twenty-two patients who underwent indirect revascularization surgery alone also underwent brain SPECT scanning at 180minutes after 123I-iomazenil administration and neuropsychological testing before and at 6months after surgery. The affected-to-contralateral cerebral hemispheric asymmetry of tracer uptake before and after surgery was then calculated. The asymmetry of tracer uptake was significantly increased after surgery (P<0.0001). A significant difference between the preoperative and postoperative asymmetry of tracer uptake was seen in patients with improved cognition compared with those with unchanged cognition (P=0.0001). The area under the receiver operating characteristic curve was 0.99 for the difference between the preoperative and postoperative asymmetry of tracer uptake to assess the ability to discriminate patients with improved cognition from those with unchanged cognition. Improvements in cognitive function after indirect revascularization surgery alone are associated with postoperative recovery in the binding potential of central benzodiazepine receptors in the affected cerebral hemisphere in adult patients with moyamoya disease accompanied by ischemic presentation due to misery perfusion.