Standard Single Photon Emission Computed Tomography Research Articles

Reduction of SPECT acquisition time using deep learning: A phantom study

Single photon emission computed tomography (SPECT) procedures are characterized by long acquisition time to acquire diagnostically acceptable image data. The goal of this investigation was to assess the feasibility of using a deep convolutional neural network (DCNN) to reduce the acquisition time. The DCNN was implemented using the PyTorch and trained using image data from standard SPECT quality phantoms. The under-sampled image dataset is provided to neural network as input, while missing projections were provided as targets. The network is to produce for the output the missing projections. The baseline method of calculating the missing projections as arithmetic means of adjacent ones was introduced. The obtained synthesized projections and reconstructed images were compared to original data and baseline data across several parameters using PyTorch and PyTorch Image Quality code libraries. Results obtained from comparisons of projection and reconstructed image data show the DCNN clearly outperforming the baseline method. However, subsequent analysis revealed the synthesized image data being more comparable to under-sampled than to fully-sampled image data. The results of this investigation imply that neural network can replicate coarser objects better. However, densely sampled clinical image datasets, coarse reconstruction matrices and patient data featuring coarse structures combined with a lack of baseline data generation methods will hamper the ability to analyse the neural network outputs correctly. This study calls for use of phantom image data and introduction of a baseline method in the evaluation of neural network outputs.

Synthesis and evaluation of N-isopropyl-p-[11C]methylamphetamine as a novel cerebral blood flow tracer for positron emission tomography

IntroductionIncreases in fasting plasma glucose (PG) levels lead to a decrease in 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) uptake in the normal brain, especially in the precuneus, resulting in an Alzheimer’s disease (AD)-like uptake pattern. Therefore, patients with higher PG levels, such as those with diabetes, can be erroneously diagnosed with AD when positron emission tomography (PET) imaging is done using [18F]FDG, due to reduced uptake of [18F]FDG in the precuneus. To help avoid an erroneous diagnosis of AD due to differences in glucose metabolism, evaluating cerebral blood flow (CBF) in the brain is useful. However, current techniques such as single photon emission computed tomography (SPECT) and [15O]H2O PET have limitations regarding early diagnosis of AD because the images they produce are of low resolution. Here, we developed a novel CBF PET tracer that may be more useful than [18F]FDG for diagnosis of AD.MethodsWe synthesized and evaluated N-isopropyl-p-[11C]methylamphetamine ([11C]4) as a carbon-11-labeled analogue of the standard CBF SPECT tracer N-isopropyl-p-[123I]iodoamphetamine. Fundamental biological evaluations such as biodistribution, peripheral metabolism in mice, and brain kinetics of [11C]4 in non-human primates with PET with successive measurement of [15O]H2O were performed.Results[11C]4 was synthesized by methylation of the corresponding tributyltin precursor (2) with [11C]MeI in a palladium-promoted Stille cross-coupling reaction. The brain uptake of [11C]4 in mice peaked at 5–15 min after injection and then promptly decreased. Most radioactivity in the brain was detected in the unchanged form, although in the periphery, [11C]4 was rapidly metabolized to hydrophilic components. Acetazolamide (AZM) treatment significantly increased the brain uptake of [11C]4 without affecting the blood levels of radioactivity in mice. Preliminary kinetics analysis showed that the K1 of [11C]4 reflected regional CBF in a vehicle-treated monkey, but that the K1 did not reflect CBF in higher flow regions after AZM loading.Conclusion[11C]4 is a potential novel CBF PET tracer. Further validation studies are needed before [11C]4 can be used in humans.

Role of stress in dynamic single-photon emission computed tomography with myocardial perfusion reserve determination in assessing the severity of coronary artery stenosis

Aim. To assess the role of global and selected scintigraphic scores of myocardial perfusion, blood flow and reserve in the anatomical and functional significance of coronary artery (CA) stenosis.Material and methods. The double-blind comparative study included 23 patients (mean age 61,2±6,8 years, 12 (52%) women, 11 (48%) men). All patients underwent stress dynamic single-photon emission computed tomography (SPECT) with adenosine triphosphate (ATP) (140 µg/kg/min in 6 minutes). Myocardial perfusion disorders were assessed by a semi-quantitative method, the total Summed Stress Score (SSS), the Summed Rest Score (SRS), and the Summed Difference Score (SDS) were determined. Global (g) and regional (r) myocardial perfusion (MP) were evaluated; myocardial perfusion reserve (MPR) was calculated as the ratio of MP at stress and at rest. Coronary angiography (CAG) was performed within 1 week after SPECT, the amount of CA narrowing was evaluated by diameter. Stenoses >50% were considered anatomically significant. The assessment of the fractional flow reserve (FFR) was performed by the ratio of the mean intracoronary pressure at the CA ostia to the pressure distal to the stenosis at the ATP infusion peak. FFR ≤0,80 was considered a sign of hemodynamically significant stenosis. Results. Neither regional nor global scintigraphic scores reflecting myocardial perfusion showed statistical significance as markers of CA stenosis >50%. Among perfusion markers, only SSSg (>4) showed good sensitivity and specificity in the diagnosis of hemodynamically significant (FFR ≤0,80) stenoses (AUC 0,76; p=0,002; sensitivity 81,8%, specificity 83,3%). The following regional flow scores allowed identification of hemodynamically significant CA: stress MPr ≤0,54 ml/min/g (AUC 0,8; p=0,0003; sensitivity 57%, specificity 92%) and MPR ≤1,5 (AUC 0,86; p< 0,0001; sensitivity 71,4%, specificity 92,8%).Conclusion. It is proved that global and regional scintigraphic scores of MP and MPR are sensitive and specific markers of hemodynamically significant (FFR ≤0,80) coronary stenosis. It can be more useful for localization diagnosis of the lesion than standard SPECT.

Does Ct volumetry accurately predict functional reserve of the future liver remnant after major hepatectomy?

Background: Precise quantitative tests are not available to measure synthetic liver function prior to major hepatectomy. Most centers rely on imperfect surrogates including laboratory studies and CT volumetry. Indocyanine green clearance can quantify functional hepatocyte mass, but does not provide regional assessment and has not been widely adopted in North America. Nuclear medicine tests are rarely used for preoperative planning, but are an additional option to asses overall, hemi-liver, and segmental hepatic function. The purpose of this study was to compare CT volumetry with functional nuclear medicine testing as an accurate measure to predict hepatic function of the future liver remnant. Methods: CT volumetry and functional nuclear medicine data were collected prospectively for patients undergoing evaluation for hepatocellular carcinoma (HCC) from February 2016-May 2018. Paired CT and nuclear medicine scans were obtained within 9 months (median 1 month) of one another. Nuclear medicine scans were performed with freshly prepared technetium 99m labeled mebrofenin (an iminodiacetic analogue), initially dynamic planar images were acquired and thereafter a single-photon emission computed tomography (SPECT) scan was performed. Total and regional liver volumes were calculated and reported by an attending radiologist. Extent of discrepancy between modalities was calculated. Clinical and demographic characteristics including the extent of chronic liver disease were recorded. Results: Over 27 months, 63 patients with HCC underwent both CT and functional nuclear medicine imaging. Median age was 64 years (range 25–85 yrs). Fifty patients (74.6%) were classified as cirrhotic. Of the cirrhotic patients, 60% (n = 30) had Child’s A, 38% Child's B (n = 19) and 2% Child's C cirrhosis (n = 1). Standard CT volumetry overestimated total functional liver volume, TLV, (median 1508 ml; range 570.2–4112.9 ml) when compared with functional nuclear medicine scan (median 1320 ml; range 6.9–3546.1 ml; p = 0.02). Significant discrepancy existed between regional liver volumes and percent contribution to hepatic function. The median volume of the right hemi-liver by CT volumetry was 906 ml (range 187–2324; 61% of TLV) and 721 ml by functional nuclear medicine study (range 12–2050; 65% of TLV; p = 0.03). Less discrepancy was found between left hemi-liver measurements: median volume by CT volumetry was 591 ml (range 100–2236; 38% of TLV) and 512 ml by functional nuclear medicine scan (range 69–2050; 35% of TLV; p = 0.21). Median discrepancy in hemi-liver volumes was 4.8% (range 0.2–51.5%) for the right, and 4.7% (0.2–51.5%) for the left hemi-liver. More than half of the patients (n = 34) had less than 5% discrepancy in hemi-liver volumes, 10 had 5–10% discrepancy, 11 had 10–20% discrepancy. Eight patients (12%) had volume discrepancies greater than 20% between CT volumetry and nuclear medicine imaging. Conclusion: Significant discrepancy exists between standard CT volumetry and nuclear medicine SPECT for estimating functional liver volumes. Compared with functional nuclear medicine imaging, CT volumetry appears to overestimate liver volume. Functional nuclear medicine scans provide additional information and may be a useful and affordable tool for preoperative assessment of the future liver remnant when planning major hepatectomy.

Comparison of Coronary Computed Tomography Angiography, Fractional Flow Reserve, and Perfusion Imaging for Ischemia Diagnosis

BackgroundFractional flow reserve (FFR) computation from coronary computed tomography angiography (CTA) datasets (FFRCT) has emerged as a promising noninvasive test to assess hemodynamic severity of coronary artery disease (CAD), but has not yet been compared with traditional functional imaging. ObjectivesThe purpose of this study was to evaluate the diagnostic performance of FFRCT and compare it with coronary CTA, single-photon emission computed tomography (SPECT), and positron emission tomography (PET) for ischemia diagnosis. MethodsThis subanalysis involved 208 prospectively included patients with suspected stable CAD, who underwent 256-slice coronary CTA, 99mTc-tetrofosmin SPECT, [15O]H2O PET, and routine 3-vessel invasive FFR measurements. FFRCT values were retrospectively derived from the coronary CTA images. Images from each modality were interpreted by core laboratories, and their diagnostic performances were compared using invasively measured FFR ≤0.80 as the reference standard. ResultsIn total, 505 of 612 (83%) vessels could be evaluated with FFRCT. FFRCT showed a diagnostic accuracy, sensitivity, and specificity of 87%, 90%, and 86% on a per-vessel basis and 78%, 96%, and 63% on a per-patient basis, respectively. Area under the receiver-operating characteristic curve (AUC) for identification of ischemia-causing lesions was significantly greater for FFRCT (0.94 and 0.92) in comparison with coronary CTA (0.83 and 0.81; p < 0.01 for both) and SPECT (0.70 and 0.75; p < 0.01 for both), on a per-vessel and -patient level, respectively. FFRCT also outperformed PET on a per-vessel basis (AUC 0.87; p < 0.01), but not on a per-patient basis (AUC 0.91; p = 0.56). In the intention-to-diagnose analysis, PET showed the highest per-patient and -vessel AUC followed by FFRCT (0.86 vs. 0.83; p = 0.157; and 0.90 vs. 0.79; p = 0.005, respectively). ConclusionsIn this study, FFRCT showed higher diagnostic performance than standard coronary CTA, SPECT, and PET for vessel-specific ischemia, provided coronary CTA images were evaluable by FFRCT, whereas PET had a favorable performance in per-patient and intention-to-diagnose analysis. Still, in patients in whom 3-vessel FFRCT could be analyzed, FFRCT holds clinical potential to provide anatomic and hemodynamic significance of coronary lesions.

Performance of cardiac cadmium-zinc-telluride gamma camera imaging in coronary artery disease: a review from the cardiovascular committee of the European Association of Nuclear Medicine (EANM)

The trade-off between resolution and count sensitivity dominates the performance of standard gamma cameras and dictates the need for relatively high doses of radioactivity of the used radiopharmaceuticals in order to limit image acquisition duration. The introduction of cadmium-zinc-telluride (CZT)-based cameras may overcome some of the limitations against conventional gamma cameras. CZT cameras used for the evaluation of myocardial perfusion have been shown to have a higher count sensitivity compared to conventional single photon emission computed tomography (SPECT) techniques. CZT image quality is further improved by the development of a dedicated three-dimensional iterative reconstruction algorithm, based on maximum likelihood expectation maximization (MLEM), which corrects for the loss in spatial resolution due to line response function of the collimator. All these innovations significantly reduce imaging time and result in a lower patient's radiation exposure compared with standard SPECT. To guide current and possible future users of the CZT technique for myocardial perfusion imaging, the Cardiovascular Committee of the European Association of Nuclear Medicine, starting from the experience of its members, has decided to examine the current literature regarding procedures and clinical data on CZT cameras. The committee hereby aims 1) to identify the main acquisitions protocols; 2) to evaluate the diagnostic and prognostic value of CZT derived myocardial perfusion, and finally 3) to determine the impact of CZT on radiation exposure.

Low-dose single acquisition rest 99mTc/stress 201Tl myocardial perfusion SPECT protocol: phantom studies and clinical validation

We developed and tested a single acquisition rest (99m)Tc-sestamibi/stress (201)Tl dual isotope protocol (SDI) with the intention of improving the clinical workflow and patient comfort of myocardial perfusion single photon emission computed tomography (SPECT). The technical feasibility of SDI was evaluated by a series of anthropomorphic phantom studies on a standard SPECT camera. The attenuation map was created by a moving transmission line source. Iterative reconstruction including attenuation correction, resolution recovery and Monte Carlo simulation of scatter was used for simultaneous reconstruction of dual tracer distribution. For clinical evaluation, patient studies were compared to stress (99m)Tc and rest (99m)Tc reference images acquired in a 2-day protocol. Clinical follow-up examinations like coronary angiography (CAG) and fractional flow reserve (FFR) were included in the assessment if available. Phantom studies demonstrated the technical feasibility of SDI. Artificial lesions inserted in the phantom mimicking ischaemia could be clearly identified. In 51/53 patients, the image quality was adequate for clinical evaluation. For the remaining two obese patients with body mass index > 32 the injected (201)Tl dose of 74 MBq was insufficient for clinical assessment. In answer to this the (201)Tl dose was adapted for obese patients in the rest of the study. In 31 patients, SDI and (99m)Tc reference images resulted in equivalent clinical assessment. Significant differences were found in 20 patients. In 18 of these 20 patients additional examinations were available. In 15 patients the diagnosis based on the SDI images was confirmed by the results of CAG or FFR. In these patients the SDI images were more accurate than the (99m)Tc reference study. In three patients minor ischaemic lesions were detected by SDI but were not confirmed by CAG. In one of these cases this was probably caused by pronounced apical thinning. For two patients no relevant clinical follow-up information was available for evaluation. The proposed SDI protocol has the potential to improve clinical workflow and patient comfort and suggests improved accuracy as demonstrated in the clinical feasibility study.

Comparison of Sulfur Hexafluoride Microbubble (SonoVue)-Enhanced Myocardial Contrast Echocardiography With Gated Single-Photon Emission Computed Tomography for Detection of Significant Coronary Artery Disease: A Large European Multicenter Study

The purpose of this study was to compare sulfur hexafluoride microbubble (SonoVue)-enhanced myocardial contrast echocardiography (MCE) with single-photon emission computed tomography (SPECT) relative to coronary angiography (CA) for assessment of coronary artery disease (CAD).Small-scale studies have shown that myocardial perfusion assessed by SonoVue-enhanced MCE is a viable alternative to SPECT for CAD assessment. However, large multicenter studies are lacking.Patients referred for myocardial ischemia testing at 34 centers underwent rest/vasodilator SonoVue-enhanced flash-replenishment MCE, standard (99m)Tc-labeled electrocardiography-gated SPECT, and quantitative CA within 1 month. Myocardial ischemia assessments by 3 independent, blinded readers for MCE and 3 readers for SPECT were collapsed into 1 diagnosis per patient per technique and were compared to CA (reference standard) read by 1 independent blinded reader.Of 628 enrolled patients who received SonoVue (71% males; mean age: 64 years; >1 cardiovascular [CV] risk factor in 99% of patients) 516 patients underwent all 3 examinations, of whom 161 (31.2%) had ≥70% stenosis (131 had single-vessel disease [SVD]; 30 had multivessel disease), and 310 (60.1%) had ≥50% stenosis. Higher sensitivity was obtained with MCE than with SPECT (75.2% vs. 49.1%, respectively; p < 0.0001), although specificity was lower (52.4% vs. 80.6%, respectively; p < 0.0001) for ≥70% stenosis. Similar findings were obtained for patients with ≥50% stenosis. Sensitivity levels for detection of SVD and proximal disease for ≥70% stenosis were higher for MCE (72.5% vs. 42.7%, respectively; p < 0.0001; 80% vs. 58%, respectively; p = 0.005, respectively).SonoVue-enhanced MCE demonstrated superior sensitivity but lower specificity for detection of CAD compared to SPECT in a population with a high incidence of CV risk factors and intermediate-high prevalence of CAD. (A phase III study to compare SonoVue® enhanced myocardial echocardiography [MCE] to single photon emission computerized tomography [ECG-GATED SPECT], at rest and at peak of low-dose Dipyridamole stress test, in the assessment of significant coronary artery disease [CAD] in patients with suspect or known CAD using Coronary Angiography as Gold Standard-SonoVue MCE vs SPECT; EUCTR2007-003492-39-GR).

Optimized analytic reconstruction for SPECT

Abstract. We develop optimized analytic reconstruction for the single-photon emission computed tomography (SPECT). This reconstruction is based on (1) Novikov's exact and Chang's approximate inversion formulas for the attenuated ray transform, (2) filtering techniques, and (3) Morozov type discrepancy principle. Our numerical examples include comparisons with the standard least square and expectation maximization iterative SPECT reconstructions.

Will the new advantages provided by PET in myocardial perfusion imaging help nuclear cardiology survive the test of time against conventional radiological techniques?

Dear Sir, In a very interesting article published in the European Journal of Nuclear Medicine and Molecular Imaging [1], Flotats et al. provide reasonable and interesting findings about the use of Rb PET in the evaluation of patients with and without coronary artery disease (CAD). It is widely accepted that, due to the small risk of complications related to conventional coronary angiography, which has up to now been the gold standard for detecting CAD, noninvasive cardiac imaging is now central to the diagnosis and management of patients with known or suspected CAD. Nuclear cardiology has played an important role in recent years: single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has been widely validated for the diagnosis and prognosis of cardiac disease, and the technique is heavily embedded in national and international guidelines [2]. In recent years, after a long period dominated by SPECT imaging, the availability of promising perfusion PET tracers such as Rb (1995) and, more recently, N-ammonia has led to various studies comparing PET and SPECT techniques. Although data obtained more than 15 years ago support the superiority of PET over SPECT for diagnosing CAD, it is unclear whether PET would still be found to be superior because of major advances in SPECT instrumentation [3] and imaging protocols [4]. The excellent work by Flotats et al., although comparing PET with standard protocol SPECT acquisition, seems to indicate that PET perfusion imaging may be a better weapon to help nuclear cardiology survive the test of time. It is undoubtedly clear that more recently cardiac magnetic resonance (CMR) may be able to play an important role in CAD detection and evaluation. During a reasonably short acquisition time (on average 45–60 min) CMR may offer a comprehensive cardiac assessment, including qualitative and quantitative functional analysis, detection of valve anomalies, accurate demonstration of infarct size and identification of inducible ischaemia [5]. Information from scanning the heart during pharmacologically induced stress is also provided. With regard to the other noninvasive techniques, a range of agents (i.e. dobutamine, adenosine, dipyridamole) are available, but adenosine is the most widely used because major cardiac events are rare and because the short half-life of the drug allows easier and safer management of patients both under normal conditions and in the event of adverse events. After the administration of adenosine, inducible ischaemia may be indirectly heralded by the onset of regional wall motion abnormalities demonstrated by the acquisition of cine MR images; however, the sensitivity of this technique is quite poor. More commonly, the effects of adenosine are directly assessed through the acquisition of a stack of images with high temporal resolution (typically one image every heartbeat) during the first pass of a bolus of gadolinium-based contrast agent. Although a compromise must be reached between temporal resolution, spatial resolution and image coverage, on modern scanners stress perfusion may be assessed in at least three short-axis sections. When the patient’s heart rate allows it, one or two long-axis sections F. Caobelli (*) : C. Pizzocaro :U. P. Guerra Department of Nuclear Medicine, Fondazione Poliambulanza, Via Bissolati 57, 25100 Brescia, Italy e-mail: fedefournier@libero.it

Pulmonary Functional Imaging: Qualitative Comparison of Fourier Decomposition MR Imaging with SPECT/CT in Porcine Lung

To compare unenhanced lung ventilation-weighted (VW) and perfusion-weighted (QW) imaging based on Fourier decomposition (FD) magnetic resonance (MR) imaging with the clinical reference standard single photon emission computed tomography (SPECT)/computed tomography (CT) in an animal experiment. The study was approved by the local animal care committee. Lung ventilation and perfusion was assessed in seven anesthetized pigs by using a 1.5-T MR imager and SPECT/CT. For time-resolved FD MR imaging, sets of lung images were acquired by using an untriggered two-dimensional balanced steady-state free precession sequence (repetition time, 1.9 msec; echo time, 0.8 msec; acquisition time per image, 118 msec; acquisition rate, 3.33 images per second; flip angle, 75°; section thickness, 12 mm; matrix, 128 × 128). Breathing displacement was corrected with nonrigid image registration. Parenchymal signal intensity was analyzed pixelwise with FD to separate periodic changes of proton density induced by respiration and periodic changes of blood flow. Spectral lines representing respiratory and cardiac frequencies were integrated to calculate VW and QW images. Ventilation and perfusion SPECT was performed after inhalation of dispersed technetium 99m ((99m)Tc) and injection of (99m)Tc-labeled macroaggregated albumin. FD MR imaging and SPECT data were independently analyzed by two physicians in consensus. A regional statistical analysis of homogeneity and pathologic signal changes was performed. Images acquired in healthy animals by using FD MR imaging and SPECT showed a homogeneous distribution of VW and QW imaging and pulmonary ventilation and perfusion, respectively. The gravitation-dependent signal distribution of ventilation and perfusion in all animals was similarly observed at FD MR imaging and SPECT. Incidental ventilation and perfusion defects were identically visualized by using both modalities. This animal experiment demonstrated qualitative agreement in the assessment of regional lung ventilation and perfusion between contrast media-free and radiation-free FD MR imaging and conventional SPECT/CT.

Cerebral blood flow abnormalities in patients with neurally mediated syncope

The aim of this study is to investigate regional cerebral blood flow (rCBF) in patients with syncope. We compared brain single photon emission computed tomography (SPECT) images of neurally mediated syncope patients with those of age/sex matched healthy volunteers. (99m)Tc-ethylcysteinate dimer (ECD) brain SPECT was performed in 35 patients (M/F = 17/18, mean 36.6 years) with syncope during the asymptomatic period, and in 35 healthy volunteers. For statistical parametric mapping (SPM) analysis, all SPECT images were spatially normalized to the standard SPECT template and then smoothed using a 14-mm full width at half maximum Gaussian kernel. The mean duration of syncope history was 4.9 years and the mean number of syncope episodes was 6.3. In all patients, syncope or presyncope episodes occurred during head-up tilt tests, and all were the vasodepressive type. SPM analysis of brain SPECT images showed significantly decreased rCBF in the right anterior insular cortex, left parahippocampal gyrus, bilateral fusiform gyri, bilateral middle and inferior temporal gyri, left lingual gyrus, bilateral precuneus and bilateral posterior lobes of the cerebellum in syncope patients at a false discovery rate corrected p < 0.05. There were no brain regions that showed increased rCBF in syncope patients. Furthermore, we found a negative correlation between the total number of syncopal episodes and the rCBF of the right prefrontal cortex, and between the duration of syncope history and the rCBF of the right cingulate gyrus at uncorrected p < 0.001. Decreases of rCBF in multiple brain regions may be responsible for autonomic dysregulation and improper processing of emotional stress in neurally mediated syncope patients, and frequent syncope episodes may lead to frontal dysfunction.

Ventilation from four-dimensional computed tomography: density versus Jacobian methods

Two calculation methods to produce ventilation images from four-dimensional computed tomography (4DCT) acquired without added contrast have been reported. We reported a method to obtain ventilation images using deformable image registration (DIR) and the underlying CT density information. A second method performs the ventilation image calculation from the DIR result alone, using the Jacobian determinant of the deformation field to estimate the local volume changes resulting from ventilation. For each of these two approaches, there are variations on their implementation. In this study, two implementations of the Jacobian-based methodology are evaluated, as well as a single density change-based model for calculating the physiologic specific ventilation from 4DCT. In clinical practice, 99mTc-labeled aerosol single photon emission computed tomography (SPECT) is the standard method used to obtain ventilation images in patients. In this study, the distributions of ventilation obtained from the CT-based ventilation image calculation methods are compared with those obtained from the clinical standard SPECT ventilation imaging. Seven patients with 4DCT imaging and standard 99mTc-labeled aerosol SPECT/CT ventilation imaging obtained on the same day as part of a prospective validation study were selected. The results of this work demonstrate the equivalence of the Jacobian-based methodologies for quantifying the specific ventilation on a voxel scale. Additionally, we found that both Jacobian- and density-change-based methods correlate well with global measurements of the resting tidal volume. Finally, correlation with the clinical SPECT was assessed using the Dice similarity coefficient, which showed statistically higher (p-value < 10−4) correlation between density-change-based specific ventilation and the clinical reference than did either Jacobian-based implementation.

Brain perfusion SPECT and EEG findings in children with autism spectrum disorders and medically intractable epilepsy

Objective: We performed brain perfusion single-photon emission computed tomography (SPECT) to detect the abnormal brain region in children with both autism spectrum disorders (ASD) and medically intractable epilepsy. Methods: Fifteen children aged 4–16 years underwent multimodal examinations (MRI, interictal and/or ictal ECD-SPECT, EEG and MEG) to investigate their indications for surgical treatment. All children were diagnosed with ASD according to DSM-IV criteria and intractable epilepsy. Despite medical treatment for more than a year, all experienced at least one seizure per month. All had no underlying basic disorders. Each SPECT result was statistically analyzed by comparing with standard SPECT images obtained from our institute (easy Z-score imaging system; eZIS). The relationship between the eZIS pattern and EEG abnormalities or clinical symptoms was investigated. Results: All children showed focal abnormal patterns on eZIS and focal spikes on EEG. In all children, eZIS revealed a mixed hypoperfusion pattern, especially in the prefrontal cortex, medial frontal cortex, anterior cingulate cortex, medial parietal cortex, and/or anterior temporal cortex. In seven of 12 children who underwent interictal SPECT studies, areas of hypoperfusion were related to the focus observed on EEG; in six children, the focal EEG spikes represented areas of hyperperfusion. The children were divided into two groups according to the main type of hypoperfusion patterns seen on eZIS; medial-cingulate type and temporal type. No significant relationship was observed between the areas of hypoperfusion and clinical symptoms. eZIS showed the epileptic focus clearly on ictal SPECT. Conclusions: SPECT was useful to detect the abnormal brain region not only in searching for the epileptic focus but also in assessing the low or high functioning region of the brain.

Assessment of left ventricular function with magnetic resonance imaging vs. echocardiography, contrast echocardiography, and single-photon emission computed tomography in patients with recent ST-elevation myocardial infarction

Magnetic resonance imaging (MRI) is often considered to be the gold standard in measuring left ventricular function and volumes. The aim of this study was to assess the agreements between standard echocardiography (standard echo), contrast echocardiography (contrast echo), single-photon emission computed tomography (SPECT), and MRI in the determination of left ventricular ejection fraction (EF) and end-diastolic volumes (EDV) in patients treated for acute ST-elevation myocardial infarction (STEMI). Standard echo, contrast echo, SPECT and MRI were performed on the same day, 3 months after STEMI in 150 patients participating in the NORwegian Study on District Treatment of ST-Elevation Myocardial Infarction (NORDISTEMI). Bland-Altman analysis of EF measured by all four imaging modalities showed generally low mean differences but wide limits of agreement. The mean EDV difference, however, was consistently higher when MRI was compared with standard echo (54.9 mL), contrast echo (41.7 mL) and SPECT (54.6 mL), and the limits of agreement were wider. The mean EDV differences between contrast echo vs. standard echo, SPECT vs. standard echo and contrast echo vs. SPECT were small. Our data suggest that all four imaging modalities measured EF closely similar after STEMI as demonstrated by a very small bias. The limits of agreement were however wide. EDV measured by MRI was consistently higher when compared with the other methods which may be caused by different tracing-methods and imaging principles. As echocardiography is preferable from a cost-benefit point of view, further analysis would be needed to clarify the nature of such differences.

Wireless Synchronization of a Multi-Pinhole Small Animal SPECT Collimation Device With a Clinical Scanner

A multi-pinhole collimation device for small animal single photon emission computed tomography (SPECT) uses the gamma camera detectors of a standard clinical SPECT scanner. The collimator and animal bed move independently of the detectors, and therefore their motions must be synchronized. One approach is manual triggering of the SPECT acquisition simultaneously with a programmed motion sequence for the device. However, some data blurring and loss of image quality result, and true electronic synchronization is preferred. An off-the-shelf digital gyroscope with integrated Bluetooth interface provides a wireless solution to device synchronization. The sensor attaches to the SPECT gantry and reports its rotational speed to a notebook computer controlling the device. Software processes the rotation data in real-time, averaging the signal and issuing triggers while compensating for baseline drift. Motion commands are sent to the collimation device with minimal delay, within approximately 0.5 second of the start of SPECT gantry rotation. Test scans of a point source demonstrate an increase in true counts and a reduction in background counts compared to manual synchronization. The wireless rotation sensor provides robust synchronization of the collimation device with the clinical SPECT scanner and enhances image quality.

Effect of modafinil on cerebral blood flow in narcolepsy patients.

To investigate the effects of modafinil on regional cerebral blood flow (rCBF) in narcolepsy, we performed 99mTc-ethylcysteinate dimer single photon emission computed tomography (SPECT) before and after modafinil or placebo medication. Brain SPECT was performed twice during the awake state before and after modafinil or placebo administration for 4 weeks in 43 drug-naive narcoleptics with cataplexy (M/F = 23/20, 29.5 +/- 5.8 years). For SPM analysis, all SPECT images were spatially normalized to the standard SPECT template and then smoothed using a 12-mm full width at half-maximum Gaussian kernel. The paired t-test was used to compare pre- and post-modafinil or placebo SPECT images. The mean modafinil dose used was 207.8 +/- 62.3 mg/day. Modafinil significantly reduced Epworth Sleepiness Scale scores from 20.3 +/- 2.1 to 5.2 +/- 3.1 (P < 0.01), while placebo did not. Compared to the off-modafinil condition, the on-modafinil condition showed significantly increased rCBF in the right dorsolateral and bilateral medial prefrontal cortices. Conversely, after modafinil administration, rCBF was decreased in bilateral precentral gyri, left hippocampus, left fusiform gyrus, bilateral lingual gyri, and cerebellum. There was no significant rCBF change after placebo administration. By a chronic administration of modafinil in narcoleptic patients, rCBF increased in the bilateral prefrontal cortices, whereas it decreased in left mesio/basal, temporal, bilateral occipital areas, and cerebellum.

Cerebral blood flow changes in man by wake‐promoting drug, modafinil: a randomized double blind study

To investigate the effects of a wake-promoting drug, modafinil on regional cerebral blood flow (rCBF) in healthy volunteers, we performed (99m)Tc-ethylcysteinate dimer single photon emission computed tomography (SPECT) before and after modafinil or placebo administration. Twenty-one healthy subjects received single doses of 400 mg modafinil or placebo in a double blind randomized crossover study design. Administrations of modafinil or placebo in a subject were separated by a 2-week washout. Brain SPECT was performed twice before and 3 h after modafinil or placebo administration. For statistical parametric mapping analysis, all SPECT images were spatially normalized to the standard SPECT template and then smoothed using a 12-mm full width at half-maximum Gaussian kernel. The paired t-test was used to compare pre- versus post-modafinil and pre- versus post-placebo SPECT images. Differences in rCBF between post-modafinil and post-placebo conditions were also tested. Modafinil decreased Epworth and Stanford sleepiness scales whereas placebo did not. The post-modafinil condition was associated with increased rCBF in bilateral thalami and dorsal pons, whereas the post-placebo condition showed increased rCBF in a smaller area of the dorsal pons when compared with the drug naïve baseline condition. Compared with the post-placebo condition, the post-modafinil condition showed higher rCBF in bilateral frontopolar, orbitofrontal, superior frontal, middle frontal gyri, short insular gyri, left cingulate gyrus, left middle/inferior temporal gyri, left parahippocampal gyrus, and left pons. In healthy volunteers, modafinil increased wakefulness and rCBF in the arousal-related systems and in brain areas related to emotion and executive function.

Reduced Cerebral Blood Flow During Wakefulness In Obstructive Sleep Apnea-Hypopnea Syndrome

To investigate changes in regional cerebral blood flow (rCBF) in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). We compared the 99mTc-ethylcysteinate dimer (ECD) single photon emission computed tomography (SPECT) images of patients with OSAHS with those of age- and sex-matched healthy volunteers. University hospital. Twenty-seven patients with severe OSAHS and 27 healthy volunteers underwent 99mTc-ECD brain SPECT studies. For statistical parametric mapping analysis, all SPECT images were spatially normalized to the standard SPECT template and then smoothed using a 14-mm full-width at half-maximum Gaussian kernel. The Student t test was used for the statistical analysis. The mean age of patients and subjects was 44.3 years (range 31-58). All patients underwent overnight polysomnography. The mean apnea-hypopnea index of patients was 60.4 +/- 17.6 per hour (range 33 -104), indicating severe OSAHS. All patients snored heavily and had daytime sleepiness (mean Epworth Sleepiness Scale score, 10.7 +/- 3.7, range 6-12). Statistical parametric mapping analysis showed that rCBF in patients with OSAHS was significantly reduced in bilateral parahippocampal gyri and in the right lingual gyrus, as compared with that of healthy volunteers (P < 0.05 with false discovery rate correction). Moreover, apnea-hypopnea indexes of patients were negatively correlated with rCBF in the right pericentral gyrus and right cuneus at uncorrected P < 0.001. Our results show the altered rCBF pattern in bilateral parahippocampal gyri, right lingual gyrus, pericentral gyrus, and cuneus in patients with severe OSAHS. These findings may partly explain the deficit in memory, spatial learning, executive function, and attention, which are frequently found in patients with OSAHS.

TH‐D‐M100F‐01: An Evaluation of Noise in Radiotracer Emission Imaging Using Flat‐Panel Detectors

Purpose: Single Photon Emission Computed Tomography (SPECT) onboard radiation therapy machines could enable the use of functional and molecular imaging in guiding the therapy beam and in monitoring disease. Costs and spatial constraints of onboard SPECT might be minimized if SPECT could be accomplished using the same flat‐panel detectors (FPDs) employed for onboard transmission imaging. This may require some re‐engineering of FPDs, and it is therefore important to understand the emission imaging performance of present‐day FPDs. Here we evaluate the electronic and offset‐and‐gain (OG) noise of current FPDs relative to the quantum noise characteristic of SPECT imaging. Method and Materials: A standard SPECT collimator was placed over a FPD. A flat circular radiotracer phantom was constructed with an outer region of 18 μCi/ml and a smaller inner region of 53 μCi/ml. (Typical human dose is 1 μCi/ml.) The phantom was placed on the collimator/FPD. Large low‐frequency variations in FPD response were removed by fitting each region (no activity, low activity, high activity) of the emission image with low‐order polynomials. Noise (standard deviation) was computed within each region as a function of number of acquisition frames, enabling separate estimates of electronic, OG, and quantum noise. Results: Electronic and quantum noise were comparable at 12 times the radiotracer doses typical of human SPECT imaging. For the particular OG correction considered, OG noise exceeded quantum noise after about 8 seconds (4 frames) of acquisition. Conclusion: For the FPD considered, electronic noise is about an order of magnitude above the quantum noise that would arise from radiotracer concentrations typical of human imaging. OG noise is also significant. These conclusions should be considered in the context of other aspects of FPD design. For example, thicker scintillators could boost emission‐imaging signal, thereby alleviating requirements on noise reduction.