Perfusion SPECT Imaging Research Articles

Two-position supine/prone myocardial perfusion SPECT (MPS) imaging improves visual inter-observer correlation and agreement

ObjectivesWe aimed to compare the inter-observer agreement between two experienced readers using supine vs combined supine/prone myocardial perfusion SPECT (MPS) in a large population. Methods1,181 consecutive patients without known coronary artery disease (CAD) undergoing rest 201Tl/stress 99mTc-sestamibi MPS studies were evaluated. Visual reads were performed in two consecutive steps, with readers scoring the stress supine perfusion images during step 1 and rescoring the images using both supine/prone data during step 2. Visual summed stress scores (SSS) of two readers including regional scores in different vascular territories were compared. ResultsThe specificity for both readers improved using combined supine/prone imaging (reader 1: 92% vs 86% [P = .0002], reader 2: 88% vs 72% [P < .0001]). The inter-observer correlation for SSS (0.90 vs 0.84, P < .0001) and inter-observer agreement for combined supine/prone reading (bias = 1.0, 95% confidence interval (CI) 0.9-1.2 vs bias = 3.1, 95% CI 2.8-3.4, P < .0001) were significantly better as compared to supine-only reading. The overall correlation between SSS scores for two readers improved with supine/prone imaging for both genders, as well as in the left anterior descending and right coronary territories. ConclusionThe inter-observer correlation and agreement significantly improve using two-position supine/prone vs supine-only imaging.

Clinical Impact of Nonuniform CT-Based Attenuation Correction in Brain Perfusion SPECT/CT Using 99mTc-ECD

Brain perfusion SPECT is commonly used to evaluate patients with cognitive impairments. Physical limits such as attenuation compromise image quality do not allow the most accurate depiction of radionuclide distribution, and thus, application of attenuation correction (AC) has been recommended. Some reports have demonstrated discordances between the uniform (UAC) and nonuniform CT-based correction (NUAC) procedures. The aim was to study the impact of these discordances on visual interpretation and their concordance with clinical symptoms. Twelve patients presenting cognitive impairments were included. Brain perfusion SPECT images were reconstructed using 2 AC methods. Qualitative image assessment was performed as uptake analysis in 21 predefined cortical ROIs for each patient. Interpretation of perfusion patterns was based on a 2-score uptake scale (normal and reduced/pathologic). Variation of uptake scores in UAC- versus NUAC-processed images and their concordance with clinical symptoms were studied. Normal image patterns generated by UAC and NUAC methods were found in 226 (90%) of 252 and in 201 (80%) of 252 ROIs, respectively. No difference between UAC and NUAC methods was found in posterior brain areas. However, differences were recorded in 51 (20%) of 252 ROIs, and this discordance was located in the anterior areas (frontal and temporal lobes), and evaluation changed from normal to pathological patterns using NUAC method. Two years later, patients showing frontal hypoperfusion on NUAC brain SPECT images expressed clinical frontal lobe dysfunctions. Discordances between UAC- and NUAC-processed images impact visual analysis of brain perfusion SPECT images. The NUAC-processed images show a good concordance with clinical symptoms, suggesting that it is an accurate method to correct attenuation.

Design of a digital phantom population for myocardial perfusion SPECT imaging research

Digital phantoms and Monte Carlo (MC) simulations have become important tools for optimizing and evaluating instrumentation, acquisition and processing methods for myocardial perfusion SPECT (MPS). In this work, we designed a new adult digital phantom population and generated corresponding Tc-99m and Tl-201 projections for use in MPS research. The population is based on the three-dimensional XCAT phantom with organ parameters sampled from the Emory PET Torso Model Database. Phantoms included three variations each in body size, heart size, and subcutaneous adipose tissue level, for a total of 27 phantoms of each gender. The SimSET MC code and angular response functions were used to model interactions in the body and the collimator-detector system, respectively. We divided each phantom into seven organs, each simulated separately, allowing use of post-simulation summing to efficiently model uptake variations. Also, we adapted and used a criterion based on the relative Poisson effective count level to determine the required number of simulated photons for each simulated organ. This technique provided a quantitative estimate of the true noise in the simulated projection data, including residual MC simulation noise. Projections were generated in 1 keV wide energy windows from 48–184 keV assuming perfect energy resolution to permit study of the effects of window width, energy resolution, and crosstalk in the context of dual isotope MPS. We have developed a comprehensive method for efficiently simulating realistic projections for a realistic population of phantoms in the context of MPS imaging. The new phantom population and realistic database of simulated projections will be useful in performing mathematical and human observer studies to evaluate various acquisition and processing methods such as optimizing the energy window width, investigating the effect of energy resolution on image quality and evaluating compensation methods for degrading factors such as crosstalk in the context of single and dual isotope MPS.

Evaluation of simultaneous 201Tl/99mTc dual-isotope cardiac SPECT imaging with model-based crosstalk compensation using canine studies

BackgroundSimultaneous 201Tl/99mTc-sestamibi dual-isotope myocardial perfusion SPECT imaging can reduce imaging time and produce perfectly registered rest/stress images. However, crosstalk from 99mTc into 201Tl images can significantly reduce 201Tl image quality. We have developed a model-based compensation (MBC) method to compensate for this crosstalk. The method has previously been validated with phantom and simulation studies. In this study, we evaluated the MBC method using a canine model. MethodsLeft anterior descending or left circumflex coronary artery stenoses were created in 50 adult mongrel dogs weighing 20-30 kg. The dogs were injected with 111 MBq (3 mCi) of 201Tl at rest, and a SPECT study acquired. Stress was induced by administering adenosine to the dog, followed by injection of 740 MBq (20 mCi) of 99mTc-sestamibi at peak stress. A second SPECT study was performed with data acquired in both 201Tl and 99mTc energy windows to provide simultaneous dual-isotope projection data. The images were reconstructed using the ordered-subsets expectation-maximization reconstruction algorithm with compensation for attenuation, scatter, and detector response. For simultaneously acquired 201Tl data, we also applied the MBC method to compensate for crosstalk contamination from 99mTc. ResultsWithout compensation, 99mTc crosstalk increased the estimated 201Tl activity concentration in the rest images and reduced defect contrast. After MBC, the 201Tl images were in good agreement with the registered single-isotope images and ex vivo count data. The ischemic (IS) to non-ischemic (NIS) region 201Tl activity concentration ratios were computed for single-isotope and dual-isotope studies. The correlation with ex vivo IS-NIS ratios was 0.815 after MBC, compared to the 0.495 from data without compensation. In addition, the regression line for the IS-NIS ratios with MBC was almost parallel to the line of identity with a slope of 0.93, compared to a slope of 0.45 without compensation. ConclusionsThese results demonstrate that model-based crosstalk compensation can provide substantial reduction of crosstalk effects in simultaneously acquired myocardial perfusion SPECT images in living biological systems.

The assessment of ischaemic burden: thoughts on definition and quantification

The most recent guidelines recommend some proof of ischaemia before invasive angiography or revascularization.1 This is based on multiple outcome studies, mainly from SPECT perfusion imaging,2 but also from stress echocardiography,3 or cardiovascular magnetic resonance (CMR) imaging either using adenosine stress first pass perfusion or dobutamine stress wall motion analysis.4,5 The majority of these studies show that patients without ischaemia have an excellent prognosis, while those with some grade of ischaemia have more events. Using invasive pressure measurements in the coronary arteries (FFR) to guide revascularization has convincingly demonstrated that patients without proof of ischaemia should not be revascularized.6 There is less data on the benefit of revascularizing patients with ischaemia, but there is increasing evidence that patients should be guided by the amount, rather than the pure presence of ischaemia.7 Most of these data stems from SPECT studies either assessing outcome from retrospective data or subgroup analyses in prospective trials. There is no prospective randomized trial assessing the amount of ischaemia a patient can tolerate without increasing the likelihood for a cardiac event or prospective randomized data on the benefit of revascularization in stable angina. Thus, the assessment and quantification of ischaemic …

Du Yanrong , Li Fang, Wang Qian, Li Dianfu, Long Mingqing, Liu Yimin, Li Bilu. （Department of Nuclear Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Belting 100730, China）

Objective To evaluate the effectiveness and safety of higenamine （HG）, a pharmacological stress agent, for the detection of myocardial ischemia using SPECT. Methods This study was an open, multi-center, randomized and positively controlled trial with crossover references. It consisted of 120 patients clinically confirmed or suspected of myocardial ischemia. Each patient underwent a resting MPI and two separate stress MPI in a randomized crossover manner with intravenous administration of HG or adenosine （Ad） on different days. The severity and extent of myocardial ischemia were diagnosed on stress MPI. The degree of vascular stenosis in terms of percentage narrowing was measured by CAG （ 〉50% was defined as coronary disease）, thus defined as gold standard. The diagnostic efficacy of HG and Ad was compared. Vital signs, routine blood and urine tests, blood biochemical items and side effects were documented for evaluation of procedure safety. Two-sample t test, X2 or Fisher＇s exact test, and Kappa test were used. Results A total of 109 patients completed the trial and CAG. The diagnostic sensitivity, specificity, accuracy, positive predictive value, negative predictive value of HG MPI were 56.1% （32/57）, 78.8% （41/52）, 67.0% （73/109）, 74.4% （32/43） and 62.1% （41/66）, respectively, which were not significantly different from those of Ad MPI （52.6% （30/57）, 82.7% （43/52）, 67.0% （73/109）, 76.9% （30/39） and 61.4% （43/70） ;X2 =0-0.2476, all P〉0.05）. The sensitivity of HG vs Ad MPI in the diagnosis of single-, doub- le- and triple-vessel ischemia was 29.6% （8/27） vs 22.2% （6/27）, 64.7% （11/17） vs 64.7% （11/17） and 100% （13/13） vs 100% （ 13/13）, respectively. The concordance between HG and Ad for the detec- tion of LAD, LCX and RCA ischemia was 95.41% （ 104/109）, 97.25% （106/109） and 97.25% （ 106/ 109） （Kappa = 0.8905, 0.8420 and 0.8874）. HG did not induce significant systolic blood pressure change during or after administration. Both HG and Ad could induce temporary decrease of diastolic blood pressure. Either HG or Ad induced significantly increased HR during administration and 5 min after administration. The clinical laboratory profile （hematology, serum chemistry, and urinalysis） was either normal or with no significant change. A total of 176 side effects （e.g, dyspnea, short breath, palpitation, dizziness, headache） were found related to HG （69.2%, 83/120） and Ad （77.5%, 93/120） administration （X2 = 2. 1307, P〉0.05）, which were mostly mild and transient. Conclusion HG is a safe and effective pharma- cological stress test agent as compared to adenosine for the detection of CAD with SPECT perfusion imaging. Key words: Coronary disease ; Higenamine hydrochloride ; Adenosine ; Tomography, emission-computed, single-photon ; MIBI

The value of right lateral decubitus position to decrease artificial defect of cardiac anterior wall in 99 Tc m -MIBI SPECT myocardial perfusion imaging for women

Objective To explore the value of right lateral decubitus position MPI for differentiating myocardial perfusion defect from cardiac anterior wall attenuation artificial defect,caused by breast of woman.Methods Forty-nine patients(average age (61.5±8.4) years) who had low likelihood of coronary artery disease and had perfusion defect in the anterior wall after exercise stress 99Tcm-MIBI MPI were included.All underwent supine and right lateral decubitus position during resting SPECT images.The myocardial perfusion SPECT images at left ventricle were reconstructed and were measured by Bull's-eye,based on the counts.Results from both supine position imaging and right lateral decubitus position imaging were compared.Paired t test was used to statistically analyse the data by SPSS 13.0.Results Compared with supine position,the counts of the anterior,inferior,apex and lateral wall in right lateral decubitus position were significantly higher:(71.30±3.53) ％ vs (66.50±3.85) ％,(70.06±4.45) ％ vs (65.44±4.16) ％,(77.90±3.00)％ vs (75.81±4.08)％,(79.30±2.26)％ vs (72.60±3.87)％ (t=6.731,5.286,3.555,10.885,all P＜0.01).The counts of septal wall were significantly lower ((66.60±3.98)％ vs (70.06±4.51)％,t=-4.625,P＜0.01) in right lateral decubitus position than that in supine position.Among the different regions of anterior wall,the counts of the anterior-middle ((76.40 ± 3.80) ％ vs (68.60 ± 4.76) ％) and anterior-apex region ((77.10±3.24) ％ vs (69.00±3.54) ％) were significantly higher (t =9.916,8.870,both P＜0.01) in right lateral decubitus position than those in supine position,but there was insignificance ((56.94±6.06)％ vs (58.50±4.98) ％,t =-1.493,P＞0.05) at anterior-basal region.The artificial defect of different degrees in anterior wall was observed in all patients in supine position,23 cases (46.9％,23/49) showed artificial defect in the anterior-middle region and 16 cases (32.7％,16/49) in the anterior-apex region.All artificial defect showed radioactive filling in right lateral position imaging,12 cases(24.5％,12/49) filled markedly and 32 cases(65.3％,32/49) filled completely.Conclusions The artificial defects caused by breast of woman mainly present in anterior-middle region and in anterior-apex region of the anterior wall in supine position imaging.The right lateral decubitus position imaging can markedly improve these artificial defects. Key words: Myocardium ; Tomography, emission-computed, single-photon; Posture; Artifacts ; MIBI

Combined Measurement of Cerebral and Cerebellar Blood Flow on Preoperative Brain Perfusion SPECT Imaging Predicts Development of New Cerebral Ischemic Events After Endarterectomy for Symptomatic Unilateral Cervical Carotid Stenosis

The aim of this study was to determine whether the ratio of blood flow contralateral-to-affected asymmetry in the cerebellar hemisphere to blood flow affected-to-contralateral asymmetry in the middle cerebral artery (MCA) territory (AR(cbl)/AR(MCA)) on preoperative brain perfusion SPECT could identify patients at risk for new cerebral ischemic events after carotid endarterectomy (CEA) for symptomatic unilateral cervical carotid stenosis. For the purposes of this study, new cerebral ischemic events included neurological deficits and cerebral ischemic lesions on diffusion-weighted MRI. Brain blood flow was assessed using 123I-IMP SPECT in 101 patients. A region of interest was automatically placed in the bilateral MCA territories and in the bilateral cerebellar hemispheres using a 3-dimensional stereotaxic region-of-interest template, and the AR(cbl)/AR(MCA) was calculated. Diffusion-weighted MRI was performed within 3 days before and 24 hours after surgery. Patients were neurologically tested before induction of general anesthesia and after recovery from general anesthesia. New cerebral ischemic events after CEA were observed in 12 patients (12%). Multivariate analysis revealed that only high AR(cbl)/AR(MCA) was significantly associated with the development of new postoperative cerebral ischemic events (95% confidence interval, 1.945-8.452; P = 0.0070). The AR(cbl)/AR(MCA) provided 75% sensitivity, 84% specificity, and 39% positive and 96% negative predictive values in predicting development of new postoperative cerebral ischemic events. The AR(cbl)/AR(MCA) on preoperative brain perfusion SPECT could identify patients at risk for new cerebral ischemic events after CEA for unilateral cervical carotid stenosis.

Left ventricular synchrony assessed by phase analysis of gated myocardial perfusion SPECT imaging in healthy subjects

Objective To investigate the value of Cedars-Sinai quantitative gated SPECT (QGS) phase analysis for left ventricular synchrony assessment in healthy subjects.Methods Seventy-four healthy subjects (41 males,33 females,average age:(60±13) years) underwent both rest and exercise 99Tcm-MIBI G-MPI.QGS software was used to analyze the reconstructed rest gated SPECT images automatically,and then the parameters of left ventricular synchrony including phase bandwidth (BW) and phase standard deviation (SD) were obtained.The influences of gender and age (age＜60 years,n =36; age ≥ 60 years,n =38) on left ventricular systolic synchronicity were analyzed.The phase angle for original segmental contraction was measured to determine the onset of the ventricular contraction using 17-segment model.Forty healthy subjects were selected by simple random sampling method to evaluate the intra-observer and interobserver repeatability of QGS phase analysis software.Two-sample t test and linear correlation analysis were used to analyze the data.Results The BW and SD of left ventricular in healthy subjects were (37.22 ±11.71)°,(11.84±5.39)° respectively.Comparisons between male and female for BW and SD yielded no statistical significance (BW:(36.00±9.70)°,(38.73±13.84)°; SD:(11.88±5.56)°,(11.79±5.26)°; t=0.96 and-0.07,both P＞0.05) ; whereas the older subjects (age≥60 years) had larger BW than the others (age＜60 years ; (39.95± 12.65) °,(34.33± 10.00) ° ; t =-2.11,P＜0.05) and no statistical significance was shown for SD between the two age groups ((11.18±4.31) °,(12.54±6.33) ° ; t =1.08,P＞0.05).Of the 74 subjects,the mechanical activation started from the ventricular base to apex in 54 subjects (73％),and from apex to base in only 20 subjects (27％).High repeatability of phase analysis was observed for both intra-observer and inter-observer (r=0.867-0.906,all P＜0.001).Conclusions Good left ventricular segmental synchrony is shown in healthy subjects.No gender difference exists for ventricular synchrony assessment.Age (＜60 years) is important for better synchrony.Cedars-Sinai QGS cardiac phase analysis software is valuable in quantitative assessment of left ventricular synchrony with high repeatability. Key words: Myocardial contraction synchrony; Ventricular function, left; Tomography,emission-computed, single-photon; Reference values; MIBI

Comparison of Coronary CT Angiography and Stress/Rest Myocardial Perfusion SPECT Imaging in a Chinese Population

The relationship between luminal stenosis measured by coronary CT angiography and stress-induced ischemia by SPECT myocardial perfusion imaging is not clearly defined. The aims of this study were to evaluate the relationship between stenosis severity by coronary CT angiography and abnormal SPECT finding and to explore the impact of clinical factors on this relationship. Seven hundred six consecutive patients with suspected coronary artery disease between January 2008 and October 2010 were prospectively enrolled. SPECT revealed 348 reversible and 58 fixed defects in 91 patients. Coronary CT angiography revealed that 339 patients had a maximal luminal stenosis 50% or greater. Total coronary artery calcium score was calculated in 428 patients, including 193 without calcification as well as 128 with mild, 59 with moderate, and 48 with severe-to-extensive calcification. Sensitivity, specificity, positive predictive value and negative predictive value (NPV) of coronary CT angiography for detecting abnormal SPECT finding were, respectively, 48.4%, 90.4%, 42.7%, and 92.2% on a patients' level and 40.2%, 95.6%, 33.6%, and 96.6% on vascular level when cutoff value of stenosis was set at 75%. Receiver operating characteristic analysis showed that the best cutoff value of stenosis for detecting abnormal SPECT finding was 55% on patients' level and 43% on vascular level. Patients with severe-to-extensive calcification had lowest specificity (56.3%) and NPV (69.2%). The sensitivity and positive predictive value of coronary CT angiography were not affected by any clinical factors (P = nonsignificant), whereas the specificity was higher in female patients, population younger than 60 years, and population without hypertension or family history of coronary artery disease (P < 0.05), and the NPV was higher among female patients and population without hypertension (P < 0.05). Coronary CT angiography has good agreement with stress/rest myocardial perfusion SPECT imaging. Coronary calcification and several clinical factors could affect the specificity and NPV of coronary CT angiography for detecting abnormal SPECT finding.

The coronary calcium treadmill test: A new approach to the initial workup of patients with suspected coronary artery disease

Due to the growth of cardiac testing and increasing cost of cardiovascular healthcare, the development of more cost-effective strategies has now become a dominant issue regarding future utilization of cardiac imaging procedures. To that end, we review the potential of combining two relatively inexpensive tests, the coronary artery calcium (CAC) scan and exercise electrocardiography (ECG), as a first-line test for the workup of patients with suspected coronary artery disease (CAD). The CAC scan was initially introduced as a screening test for CAD, based on data indicating that it is a specific marker for atherosclerosis, predicts clinical risk in accordance with the magnitude of CAC, and provides incremental information for prognostic risk compared to more readily available clinical data. However, CAC scores also predict the likelihood of observing myocardial ischemia among patients undergoing exercise myocardial perfusion SPECT imaging. Exercise ECG predicts clinical events according to the ST-segment response and according to functional exercise capacity, with the latter parameter as a stronger predictor of clinical outcomes. Like CAC scores, exercise functional capacity can also be used to predict the likelihood of ischemia since ischemia diminishes proportionally with increasing exercise capacity. Recent work indicates that when patients are designated by Bayesian analyses into low, intermediate, and high likelihood categories for CAD based on clinical data and the response to exercise ECG, the frequency of inducible myocardial ischemia is very low among both low and intermediate CAD likelihood patients who have a CAC score <400. Future studies are needed to investigate what clinical factors might further modify the CAC-ischemia relationship. On the basis of current data, an initial testing strategy that employs the combined calcium treadmill test has the inherent ability to designate a substantial number of intermediate likelihood patients who would not require further testing due to relatively low CAC scores and reasonable functional capacity.

Differential impact of multi-focus fan beam collimation with L-mode and conventional systems on the accuracy of myocardial perfusion imaging: Quantitative evaluation using phantoms.

A novel IQ-SPECT™ method has become widely used in clinical studies. The present study compares the quality of myocardial perfusion images (MPI) acquired using the IQ-SPECT™ (IQ-mode), conventional (180° apart: C-mode) and L-mode (90° apart: L-mode) systems. We assessed spatial resolution, image reproducibility and quantifiability using various physical phantoms. SPECT images were acquired using a dual-headed gamma camera with C-mode, L-mode, and IQ-mode acquisition systems from line source, pai and cardiac phantoms containing solutions of (99m)Tc. The line source phantom was placed in the center of the orbit and at ± 4.0, ± 8.0, ± 12.0, ± 16.0 and ± 20.0 cm off center. We examined quantifiability using the pai phantom comprising six chambers containing 0.0, 0.016, 0.03, 0.045, 0.062, and 0.074 MBq/mL of 99m-Tc and cross-calibrating the SPECT counts. Image resolution and reproducibility were quantified as myocardial wall thickness (MWT) and %uptake using polar maps. The full width at half maximum (FWHM) of the IQ-mode in the center was increased by 11% as compared with C-mode, and FWHM in the periphery was increased 41% compared with FWHM at the center. Calibrated SPECT counts were essentially the same when quantified using IQ-and C-modes. IQ-SPECT images of MWT were significantly improved (P<0.001) over L-mode, and C-mode SPECT imaging with IQ-mode became increasingly inhomogeneous, both visually and quantitatively (C-mode vs. L-mode, ns; C-mode vs. IQ-mode, P<0.05). Myocardial perfusion images acquired by IQ-SPECT were comparable to those acquired by conventional and L-mode SPECT, but with significantly improved resolution and quality. Our results suggest that IQ-SPECT is the optimal technology for myocardial perfusion SPECT imaging.

Dekstrokardide Miyokard Perfüzyon Spect Görüntüleme: Olgu Sunumu

The myocardial perfusion scintigraphy acquisition and analysis present some technical differences in the rare dextrocardia cases. Here we report a case of a 38 year-old woman with dextrocardia who had been applied myocardial perfusion scintigraphy. Presented case showed that the thoracic and abdominal organs had a mirror image with situs inversus totalis type dextrocardia. The incidence of coronary heart disease and life span of people with situs inversus totalis are the same as the normal population. So we may apply myocardial perfusion scintigraphy to this patient group. The current case is presented in order to remind the special applications of myocardial perfusion SPECT imaging in patients with dextrocardia. Conflict of interest:None declared.

Brain Tissue Volumes and Perfusion Change with the Number of Optic Neuritis Attacks in Relapsing Neuromyelitis Optica: A Voxel-Based Correlation Study

Recent neuroimaging studies show that brain abnormalities in neuromyelitis optica (NMO) are more frequent than earlier described. Yet, more research considering multiple aspects of NMO is necessary to better understand these abnormalities. A clinical feature of relapsing NMO (RNMO) is that the incremental disability is attack-related. Therefore, association between the attack-related process and neuroimaging might be expected. On the other hand, the immunopathological analysis of NMO lesions has suggested that CNS microvasculature could be an early disease target, which could alter brain perfusion. Brain tissue volume changes accompanying perfusion alteration could also be expected throughout the attack-related process. The aim of this study was to investigate in RNMO patients, by voxel-based correlation analysis, the assumed associations between regional brain white (WMV) and grey matter volumes (GMV) and/or perfusion on one side, and the number of optic neuritis (ON) attacks, myelitis attacks and/or total attacks on the other side. For this purpose, high resolution T1-weighted MRI and perfusion SPECT imaging were obtained in 15 RNMO patients. The results showed negative regional correlations of WMV, GMV and perfusion with the number of ON attacks, involving important components of the visual system, which could be relevant for the comprehension of incremental visual disability in RNMO. We also found positive regional correlation of perfusion with the number of ON attacks, mostly overlapping the brain area where the WMV showed negative correlation. This provides evidence that brain microvasculature is an early disease target and suggests that perfusion alteration could be important in the development of brain structural abnormalities in RNMO.

Perfusion SPECT in patients with suspected pulmonary embolism

Ventilation/perfusion tomography (V/PSPECT), with new interpretation criteria and newer tracers for ventilation imaging, has markedly improved the diagnostic yield in acute pulmonary embolism (PE). Here, we evaluated the diagnostic performance of perfusion SPECT (PSPECT) without ventilation imaging. We studied 152 patients with clinically suspected PE who had been examined with both V/PSPECT and multidetector computed tomographic angiography (MD-CTA). The diagnosis or exclusion of PE was decided by the referring clinician based on both the V/PSPECT and/or MD-CTA findings in combination with the clinical findings. PSPECT images were retrospectively examined by a physician with experience in the interpretation of planar perfusion scans who was blinded to clinical, V/PSPECT and MD-CTA data. PSPECT images were interpreted without the aid of chest radiography. All the patients who were deemed to have PE were given anticoagulant therapy. Of the 152 patients, 59 (39%) received a final diagnosis of PE, and 19 (32%) had associated cardiopulmonary diseases such as pneumonia, COPD, or left heart failure. PSPECT correctly identified 53 (90%) of the 59 patients with PE. The specificity was 88 of 93 (95%). None of the PSPECT images was rated nondiagnostic. PSPECT yielded an overall diagnostic accuracy of 93% (95% confidence interval, CI, 87-96%). At the observed PE prevalence of 39 %, the positive and negative predictive values of PSPECT were 91% (95% CI, 80-97%) and 94% (95% CI, 86-97%), respectively. In managing critically ill patients, PSPECT might be a valid alternative to V/PSPECT or MD-CTA since it was able to identify most patients with PE with a low false-positive rate and no inconclusive results.

Rate dependent left bundle branch block: Does it have any effect on the myocardial perfusion SPECT

Dear Sir, the recent issue of Nuclear Medicine Review published an interesting study by Gholamrezanezhad et al. regarding rate dependent left bundle branch block and its effect on myocardial perfusion SPECT [1]. They reported four cases with rate dependent LBBB during exercise stress for myocardial perfusion imaging. Myocardial perfusion SPECT imaging showed no evidence of reversible perfusion defects in three of the patients. They concluded that “maybe it is possible to continue exercise tolerance test (ETT) for those patients undergoing myocardial perfusion scintigraphy and developing rate dependent LBBB”. As the authors themselves mentioned in their study, the number of cases in their case report was not statistically enough to draw any definite conclusion. We would like to report a case with rate dependent LBBB during ETT who developed perfusion defects in the septal wall which disappeared on the Dipyridamole stress imaging. The case was a 45 year old female patient with history of atypical chest pain since 2 years ago. Her rest ECG was normal. The patient had inconclusive ETT one month before. She was referred to our department for myocardial perfusion SPECT for diagnosis of possible coronary artery disease (CAD). Baseline blood pressure was 130/90 mmHg and baseline heart rate was 70. Five minutes after beginning of ETT (stage II of Bruce protocol and at heart rate of 147), the patient developed LBBB on the ECG monitoring (Figure 1). Rate dependent left bundle branch block: Does it have any effect on the myocardial perfusion SPECT

An Unusual Presentation of Coronary Artery Fistula in Athlete - Case Report

A 32-year-old active cyclist was referred fo r the evaluation because of syncope he had performed in preseason. He was found to be normostenic, acyanotic, normotensive with clear lungs and a regular pulse of 60 bp m, with normal dual heart sounds and a grade Levine 2/6 continuous diastolic murmu r in the second intercostal space of the left parasternal area. He had no family history of premature card iac death and his lipids were normal. Rest ECG showed a regular sinus rhythm of 62 bp m with inco mplete right bundle branch block and no significant ST-T changes. A transthoracic ECHO in parasternal short-axis view revealed an anomalous colour flow jet in diastole arising fro m the lateral wall into the main pulmonary artery and coronary artery fistula with non-significant left -to-right shunt (Qp/Qs ratio 1.2).came under suspicion. In contrast, it has not been confirmed clearly by the transoesophageal ECHO. Coronary angiography was without coronary stenosis and confirmed a 'serpentine' anomalous drainage supposedly from left anterior descending artery to the main pulmonary artery. A complex anato my of sacculary dilated fistula that originates fro m the pro ximal left anterio r descending artery and drainages the main pulmonary artery was showed in detail by a 64 slice MDCT scanning. Myocardial Tc-99m Myoview perfusion SPECT imag ing showed no perfusion defects in maximal physical stress and follo w-up without intervention was suggested. In addition, due to the results of holter ECG monitoring, head-up tilt testing, carotid sinus massage and programmed atrial stimulat ion syncope was concluded as vasovagal, but its nature still remains discussible. After a three year follow-up patient remains asympto matic and recently performed control myocardial perfusion SPECT showed no signs of stress related myo cardial ischemia. In conclusion, several imaging techniques are needed for an accurate diagnosis of coronary fistula and for the suggestion of proper further management. In some cases syncope may be the first man ifestation of CAF, but it is still unclear if it is directly related to the coronary anomaly.

Does Rubidium-82 PET Have Superior Accuracy to SPECT Perfusion Imaging for the Diagnosis of Obstructive Coronary Disease?: A Systematic Review and Meta-Analysis

The purpose of this study was to evaluate the accuracy of rubidium (Rb)-82 positron emission tomography (PET) for the diagnosis of obstructive coronary artery disease (CAD) in comparison to single-photon emission tomography (SPECT). Myocardial perfusion imaging is widely used in the assessment of patients with known or suspected CAD. PET using Rb-82 has potential advantages over SPECT that may make it more accurate and that reduce radiation exposure compared with SPECT but has increased costs. Comparisons of these technologies are highly relevant for policy makers and practice guidelines. However, studies directly comparing Rb-82 PET with contemporary SPECT have been limited. The authors therefore undertook a systematic review of studies where either Rb-82 PET or technetium-99m SPECT with both attenuation correction and electrocardiography-gating were used as a diagnostic test for obstructive CAD with invasive coronary angiogram as a reference standard. These technologies were then compared. Fifteen PET and 8 SPECT studies (1,344 and 1,755 patients, respectively) met inclusion criteria and pooled accuracy using weighted averages according to the size of the patient population was determined for PET and SPECT with sensitivities of 90% (confidence interval [CI]: 0.88 to 0.92) and 85% (CI: 0.82 to 0.87) and specificities of 88% (CI: 0.85 to 0.91) and 85% (CI: 0.82 to 0.87), respectively. Summary receiver-operating characteristic curves were computed: area under the curve was 0.95 and 0.90 for PET and SPECT, respectively (p < 0.0001). There was heterogeneity among study populations and some studies were limited by referral bias. Rb-82 PET is accurate for the detection of obstructive CAD and, despite advances in SPECT technology, remains superior. More widespread use of Rb-82 PET may be beneficial to improve CAD detection.

Correlation between neuropsychological tests and hypoperfusion in MCI patients: anatomical labeling using xjView and Talairach Daemon Software

Statistical analysis of brain perfusion SPECT images has shown mild to severe abnormalities, consistent with cortical dysfunctions in the brain. Recently, functional brain imaging such as fMRI, PET and SPECT is increasingly used for diagnosis of MCI. In this study, we calculate the correlation with perfusion of brain SPECT and neuropsychological test scores of patients by SPM analysis to evaluate the relationship with cerebral hypoperfusion and cognitive dysfunction in MCI patients. Anatomical labeling was performed automatically using the Talairach Daemon (TD) and xjView. Ninety-three patients (mean age 67.2 ± 7.42 years; 59 women and 34 men) with MCI were selected and examined by the comprehensive neuropsychological test. Tc-99m-HMPAO brain SPECT images were acquired on the patients using a two-head gamma camera. We analyzed the brain image of MCI patients by SPM8 software, and observed the anatomical correlated region, between the neuropsychological tests and cerebral hypoperfusion. The SPM8 tool provided correlation between neuropsychological score and brain perfusion by simple regression method. The neuropsychological test included attention, language function, visuospatial function, memory, frontal executive function, depression score and general cognitive function. Percentage of voxels with correlated area to the whole brain was calculated and the values by Rey complex figure test (CFT) copy score, MMSE score, Seoul verbal learning test (SVLT) immediate recall score and Rey CFT delayed recall score were 15.3, 12.33, 10.59 and 8.45 %, respectively. Rey CFT copy score was correlated with perfusion in the left middle temporal gyrus (BA 21), right inferior frontal gyrus (BA 45), right lingual gyrus, left lingual gyrus (BA 18), right postcentral gyrus (BA 40), right cingulate gyrus (BA 31) and left thalamus (pulvinar) with p < 0.01 FDR. The correlation related to MMSE included left parahippocampal gyrus, right fusiform gyrus and right middle frontal gyrus (BA 46). SVLT immediate recall score was correlated with left superior temporal gyrus and Rey CFT delayed recall score was correlated with left inferior frontal gyrus (BA 47), right inferior frontal gyrus, and left lentiform nucleus. Visuospatial and general cognitive dysfunctions in the patients with MCI were most correlated with cerebral hypoperfusion. Rey CFT copy and MMSE scores were more strongly correlated with blood perfusion of the brain than with other neuropsychological test scores. xjView was a useful tool to find out the anatomical name of the selected voxel or clusters and to display the cluster's anatomical information and list all cluster information and could be used instead of TD Client.

Association between plasma homocysteine and myocardial SPECT abnormalities in patients referred for suspected myocardial ischaemia

Elevated plasma homocysteine level has emerged as a relatively newly recognised risk factor for coronary artery disease (CAD). However, reduction of plasma homocysteine levels in large prospective studies did not appear to reduce the risk for subsequent cardiac events. In this study, we investigated the association between plasma homocysteine levels and quantitative indices of myocardial perfusion SPECT imaging in patients referred for myocardial ischaemia. Quantitative myocardial perfusion SPECT indices were obtained for 120 patients who were recruited for the study. All patients underwent a two-day rest-stress myocardial perfusion imaging. Plasma venous sampling was done on all patients after an overnight fast. Of the 120 participants (mean age 56 years, 53% males), 33% had elevated plasma homocysteine levels. The plasma homocysteine level was then compared to the results of imaging and other known risk factors. After adjustment for traditional risk factors of coronary artery disease, patients with elevated homocysteine levels had a significantly higher mean summed stress score (SSS) (11.3 vs 6.9, p = 0.02) than patients with a normal homocysteine level. This was true for both single- and multivessel disease. Also, patients with elevated homocysteine levels had a higher stress end-systolic volume (SESV) (137 vs 105 ml, p = 0.03) and lower post-stress left ventricular ejection fraction (SEF) (54 vs 64%, p = 0.02). The patients with elevated plasma homocysteine levels also had a significantly lower mean body mass index (BMI) (26.6 vs 30.6 kg/m(2), p = 0.002). There was a significant relationship between the total number of known risk factors in a patient with CAD and the proportion of patients presenting with elevated plasma homocysteine levels (p = 0.03). Also, the extent of infarct, as measured by the summed rest score (SRS), was more closely correlated with an elevated homocysteine level than with the degree of ischaemia. There was a correlation between plasma homocysteine level and the presence and extent of myocardial perfusion abnormalities in patients with established coronary artery disease, in particular those with multiple risk factors and multi-vessel infarction.