4D non-local means post-filtering for cardiac gated SPECT.

Cardiac gated images often suffer from increased noise in single photon emission computed tomography (SPECT) due to reduced data counts compared to non-gated studies. We investigate a spatiotemporal post-processing approach based on a non-local means (NLM) filter for suppressing the noise in gated SPECT images. In this filter, the output at a voxel location is computed from a weighted average of voxels in its four-dimensional (4D) neighborhood, wherein the filter coefficients are adjusted according to the similarity level in the local image pattern of individual voxels with respect to the output voxel. This adaptive property allows the filter to achieve noise reduction while avoiding excessive blur of the heart wall. In the experiments, we first evaluated the accuracy of the proposed NLM filtering approach using simulated SPECT imaging data. We then demonstrated the approach on eight sets of clinical acquisitions. In addition, we also explored the robustness of the NLM filter with imaging dose reduced by 50% in these clinical acquisitions. The quantitative results show that 4D NLM filtering could effectively reduce the noise level in gated images, leading to more accurate reconstruction of the myocardium. Compared to spatial filtering alone, using temporal filtering in NLM could reduce the mean-squared-error of the myocardium by 55.63% and improve the left ventricle resolution by 19.92%. It could also improve the visibility of perfusion defects in gated images. Similar results are also observed on the clinical acquisitions both at standard dose and at 50% reduced dose. The 4D NLM results are also found to be comparable to that of a motion-compensated 4D reconstruction approach which is computationally more demanding.

Clinical significance of right ventricular activity on treadmill thallium-201 myocardial single-photon emission computerized tomography using cadmium-zinc-telluride cameras.

OBJECTIVE: Identification of right ventricular (RV) abnormalities is important in patients with suspected coronary artery disease (CAD). RV activity can be better visualized on myocardial single-photon emission computerized tomography (SPECT) using a higher sensitivity cadmium-zinc-telluride (CZT) detector. The aim of this study was to investigate the clinical significance of RV/left ventricular (LV) uptake ratios during exercise thallium-201 SPECT using CZT detectors. PATIENTS AND METHODS: A total of 102 patients underwent treadmill ECG-gated SPECT, coronary angiography, and echocardiography. SPECT myocardial perfusion was interpreted using a 17-segment model and a 0-4-point scale. RV/LV uptake ratios were calculated on the basis of maximum counts per pixel within the entire RV and LV walls. The relationships between RV/LV uptake ratio and gated SPECT, presence of CAD (≥50% stenosis in the left main or ≥70% in the main branches), demographics, and echocardiographic parameters were analyzed. RESULTS: Stress RV/LV ratios correlated positively with the presence of left main or multivessel disease, and tricuspid regurgitation maximum pressure gradient. After multivariate regression, stress/rest RV/LV ratios correlated positively with mitral flow deceleration time, age, female sex, and use of ß-blockers. CONCLUSION: RV/LV uptake ratios on the basis of exercise myocardial perfusion SPECT imaging using CZT cameras are useful for the detection of severe CAD and could serve as an indicator of pulmonary hypertension and LV diastolic dysfunction.

The influence of number of counts in the myocardium in the determination of reproducible functional parameters in gated-SPECT studies simulated with GATE / Influencia del número de cuentas en el miocardio, en la determinación de los parámetros funcionales en los estudios de Gated-SPECT, simulados con GATE

Myocardial perfusion gated-single photon emission computed tomography (gated-SPECT) imaging is used for the combined evaluation of myocardial perfusion and left ventricular (LV) function. The aim of this study is to analyze the influence of counts/pixel and concomitantly the total counts in the myocardium for the calculation of myocardial functional parameters. Material and methods. Gated-SPECT studies were performed using a Monte Carlo GATE simulation package and the NCAT phantom. The simulations of these studies use the radiopharmaceutical 99mTc-labeled tracers (250, 350, 450 and 680 MBq) for standard patient types, effectively corresponding to the following activities of myocardium: 3, 4.2, 5.4–8.2 MBq. All studies were simulated using 15 and 30 s/projection. The simulated data were reconstructed and processed by quantitative-gated-SPECT software, and the analysis of functional parameters in gated-SPECT images was done by using Bland–Altman test and Mann–Whitney–Wilcoxon test. Results. In studies simulated using different times (15 and 30 s/projection), it was noted that for the activities for full body: 250 and 350 MBq, there were statistically significant differences in parameters Motility and Thickness. For the left ventricular ejection fraction (LVEF), end-systolic volume (ESV) it was only for 250MBq, and 350MBq in the end-diastolic volume (EDV), while the simulated studies with 450 and 680 MBq showed no statistically significant differences for global functional parameters: LVEF, EDV and ESV. Conclusion. The number of counts/pixel and, concomitantly, the total counts per simulation do not significantly interfere with the determination of gated-SPECT functional parameters, when using the administered average activity of 450 MBq, corresponding to the 5.4 MBq of the myocardium, for standard patient types (AU)

La gammagrafía de perfusión miocárdica sincronizada con el eletrocardiograma (Gated-SPECT) permite la evaluación de la perfusión miocárdica y la función ventricular izquierda. El objetivo de este estudio fue analizar la influencia de las cuentas/pixel y, las cuentas totales en miocardio en la determinación de los parámetros funcionales. Material y métodos. Hemos simulado estudios Gated-SPECT, por el método Monte Carlo GATE y el uso de fantoma NCAT. Las simulaciones de estos estudios han considerado un paciente estándar utilizando un radiofármaco marcado con 99mTc, con diferentes actividades (250, 350, 450 y 680 MBq) correspondientes a las siguientes actividades en miocardio: 3; 4,2; 5,4 a 8,2 MBq. Se simularon todos los estudios con un tiempo de 15 y 30 seg/proyección. Los datos simulados fueron reconstruidos, procesados y cuantificados por el software Quantitative-Gated-SPECT. El análisis de la influencia de las cuentas en los parámetros funcionales se llevó a cabo utilizando la prueba de Bland-Altman y Mann-Whitney-Wilcoxon. Resultados. En los estudios simulados con diferentes tiempos (15 y 30 seg/proyección), se encontró que para las actividades del cuerpo entero 250 y 350 MBq hubo diferencias estadísticamente significativas en los parámetros de motilidad y espesor; para la FEVI, VTS solo para 250 MBq, y VTD solo para 350 MBq. En los estudios simulados con 450 y 680 MBq no se encontraron diferencias estadísticamente significativas para los parámetros funcionales globales: FEVI, VTD y VTS. Conclusión. Por simulación en un paciente estándar, el número de cuentas/píxel y, de forma concomitante, las cuentas totales no interfiere significativamente en la determinación de los parámetros funcionales generales de Gated-SPECT, cuando se utiliza la actividad media de 450 MBq, correspondiente a 5,4 MBq en miocardio (AU)

Anatomical-based partial volume correction for low-dose dedicated cardiac SPECT/CT.

Due to the limited spatial resolution, partial volume effect has been a major degrading factor on quantitative accuracy in emission tomography systems. This study aims to investigate the performance of several anatomical-based partial volume correction (PVC) methods for a dedicated cardiac SPECT/CT system (GE Discovery NM/CT 570c) with focused field-of-view over a clinically relevant range of high and low count levels for two different radiotracer distributions. These PVC methods include perturbation geometry transfer matrix (pGTM), pGTM followed by multi-target correction (MTC), pGTM with known concentration in blood pool, the former followed by MTC and our newly proposed methods, which perform the MTC method iteratively, where the mean values in all regions are estimated and updated by the MTC-corrected images each time in the iterative process. The NCAT phantom was simulated for cardiovascular imaging with (99m)Tc-tetrofosmin, a myocardial perfusion agent, and (99m)Tc-red blood cell (RBC), a pure intravascular imaging agent. Images were acquired at six different count levels to investigate the performance of PVC methods in both high and low count levels for low-dose applications. We performed two large animal in vivo cardiac imaging experiments following injection of (99m)Tc-RBC for evaluation of intramyocardial blood volume (IMBV). The simulation results showed our proposed iterative methods provide superior performance than other existing PVC methods in terms of image quality, quantitative accuracy, and reproducibility (standard deviation), particularly for low-count data. The iterative approaches are robust for both (99m)Tc-tetrofosmin perfusion imaging and (99m)Tc-RBC imaging of IMBV and blood pool activity even at low count levels. The animal study results indicated the effectiveness of PVC to correct the overestimation of IMBV due to blood pool contamination. In conclusion, the iterative PVC methods can achieve more accurate quantification, particularly for low count cardiac SPECT studies, typically obtained from low-dose protocols, gated studies, and dynamic applications.

Técnicas de imagen en la insuficiencia cardiaca aguda / Imaging techniques in acute heart failure

En los últimos años las técnicas de imagen han revolucionado el diagnóstico de la insuficiencia cardiaca. Ante un cuadro clínico compatible con descompensación aguda, la instauración precoz de las medidas generales y el tratamiento etiológico determina en gran medida el pronóstico. Dada su rentabilidad diagnóstica y su portabilidad, la exploración con ultrasonidos se ha convertido en una herramienta fundamental en este contexto, y actualmente se encuentra en todos los ámbitos médicos que rodean al paciente crítico. La resonancia magnética cardiaca y la tomografía computarizada permiten caracterizar en detalle múltiples aspectos previamente inasequibles de la anatomía y la función cardiacas. Esto permite guiar y monitorizar la mayor parte de las decisiones terapéuticas en esta población de una forma completamente no invasiva. El presente artículo tiene por objeto revisar la utilidad de las técnicas de imagen clínicamente relevantes en el contexto de un episodio agudo de insuficiencia cardiaca. Se enfatizan con especial detalle sus indicaciones y limitaciones, y se proporcionan las bases para interpretar adecuadamente sus resultados (AU)

In recent years, imaging techniques have revolutionized the diagnosis of heart failure. In patients with a clinical picture of acute decompensation, prognosis is largely determined by early implementation of general measures and treatment of the underlying cause. Given its diagnostic yield and portability, ultrasound has become an essential tool in the setting of acute heart failure, and is currently found in all medical departments involved in the care of the critically ill patient. Cardiac magnetic resonance and computed tomography allow detailed characterization of multiple aspects of cardiac structure and function that were previously unavailable. This helps guide and monitor many of the treatment decisions in the acute heart failure population in an entirely noninvasive way. This article aims to review the usefulness of the imaging techniques that are clinically relevant in the context of an episode of acute heart failure. We discuss the indications and limitations of these techniques in detail and describe the general principles for the appropriate interpretation of results (AU)

Cardiac function changes with switching from the supine to prone position: analysis by quantitative semiconductor gated single-photon emission computed tomography.

BACKGROUND: Prone positioning is required in certain operations such as spinal surgery. Changes in cardiac function in the prone position have been studied with various methodologies. Few studies have investigated changes in left ventricular diastolic function and rhythm in subjects turned prone. METHODS AND RESULTS: Cardiac function was evaluated in the supine and prone positions in 90 patients without atrial fibrillation who underwent (99m)Tc-tetrofosmin quantitative gated single-photon emission computed tomography. Three groups of 30 patients each were classified as "no history of myocardial ischemia or cardiomyopathy" (Group A), "history of myocardial infarction" (Group B), and "ischemic heart disease without myocardial infarction history" (Group C). Upon assuming the prone position, the cardiac index and any dyssynchrony worsened in all groups. Ejection fraction changes occurred only in Group B, and diastolic function changes occurred in Groups B and C, but not in Group A. The changes caused by prone positioning were more severe in the patients with poor cardiac function. CONCLUSIONS: Prone positioning induces significant changes in systolic and diastolic function, as well as dyssynchrony. The negative effects of prone positioning are more severe in patients with poor baseline cardiac function.

End-expiration respiratory gating for a high-resolution stationary cardiac SPECT system.

Respiratory and cardiac motions can degrade myocardial perfusion SPECT (MPS) image quality and reduce defect detection and quantitative accuracy. In this study, we developed a dual respiratory and cardiac gating system for a high-resolution fully stationary cardiac SPECT scanner in order to improve the image quality and defect detection. Respiratory motion was monitored using a compressive sensor pillow connected to a dual respiratory-cardiac gating box, which sends cardiac triggers only during end-expiration phases to the single cardiac trigger input on the SPECT scanners. The listmode data were rebinned retrospectively into end-expiration frames for respiratory motion reduction or eight cardiac gates only during end-expiration phases to compensate for both respiratory and cardiac motions. The proposed method was first validated on a motion phantom in the presence and absence of multiple perfusion defects, and then applied on 11 patient studies with and without perfusion defects. In the normal phantom studies, the end-expiration gated SPECT (EXG-SPECT) reduced respiratory motion blur and increased myocardium to blood pool contrast by 51.2% as compared to the ungated images. The proposed method also yielded an average of 11.2% increase in myocardium to defect contrast as compared to the ungated images in the phantom studies with perfusion defects. In the patient studies, EXG-SPECT significantly improved the myocardium to blood pool contrast (p < 0.005) by 24% on average as compared to the ungated images, and led to improved perfusion uniformity across segments on polar maps for normal patients. For a patient with defect, EXG-SPECT improved the defect contrast and definition. The dual respiratory-cardiac gating further reduced the blurring effect, increased the myocardium to blood pool contrast significantly by 36% (p < 0.05) compared to EXG-SPECT, and further improved defect characteristics and visualization of fine structures at the expense of increased noise on the patient with defect. The results showed that the proposed methods can effectively reduce motion blur in the images caused by both respiratory and cardiac motions, which may lead to more accurate defect detection and quantifications. This approach can be easily adapted in routine clinical practice on currently available commercial systems.

Cardiac hybrid imaging.

Hybrid cardiac single photon emission computed tomography (SPECT)/CT imaging allows combined assessment of anatomical and functional aspects of cardiac disease. In coronary artery disease (CAD), hybrid SPECT/CT imaging allows detection of coronary artery stenosis and myocardial perfusion abnormalities. The clinical value of hybrid imaging has been documented in several subsets of patients. In selected groups of patients, hybrid imaging improves the diagnostic accuracy to detect CAD compared to the single imaging techniques. Additionally, this approach facilitates functional interrogation of coronary stenoses and guidance with regard to revascularization procedures. Moreover, the anatomical information obtained from CT coronary angiography or coronary artery calcium scores (CACS) adds prognostic information over perfusion data from SPECT. The use of cardiac hybrid imaging has been favoured by the dissemination of dedicated hybrid systems and the release of dedicated image fusion software, which allow simple patient throughput for hybrid SPECT/CT studies. Further technological improvements such as more efficient detector technology to allow for low-radiation protocols, ultra-fast image acquisition and improved low-noise image reconstruction algorithms will be instrumental to further promote hybrid SPECT/CT in research and clinical practice.

Monte Carlo simulation of the basic features of the GE Millennium MG single photon emission computed tomography gamma camera / Simulación de Monte Carlo de los rasgos básicos de la cámara gamma SPECT GE Millennium MG

OBJECTIVE: To describe and validate the simulation of the basic features of GE Millennium MG gamma camera using the GATE Monte Carlo platform. MATERIAL AND METHODS: Crystal size and thickness, parallel-hole collimation and a realistic energy acquisition window were simulated in the GATE platform. GATE results were compared to experimental data in the following imaging conditions: a point source of 99mTc at different positions during static imaging and tomographic acquisitions using two different energy windows. The accuracy between the events expected and detected by simulation was obtained with the Mann-Whitney-Wilcoxon test. Comparisons were made regarding the measurement of sensitivity and spatial resolution, static and tomographic. Simulated and experimental spatial resolutions for tomographic data were compared with the Kruskal-Wallis test to assess simulation accuracy for this parameter. RESULTS: There was good agreement between simulated and experimental data. The number of decays expected when compared with the number of decays registered, showed small deviation (<=0.007%). The sensitivity comparisons between static acquisitions for different distances from source to collimator (1, 5, 10, 20, 30 cm) with energy windows of 126-154 keV and 130-158 keV showed differences of 4.4%, 5.5%, 4.2%, 5.5%, 4.5% and 5.4%, 6.3%, 6.3%, 5.8%, 5.3%, respectively. For the tomographic acquisitions, the mean differences were 7.5% and 9.8% for the energy window 126-154 keV and 130-158 keV. Comparison of simulated and experimental spatial resolutions for tomographic data showed no statistically significant differences with 95% confidence interval. CONCLUSIONS: Adequate simulation of the system basic features using GATE Monte Carlo simulation platform was achieved and validated

Objetivo. Describir y validar la simulación de características básicas de la cámara gamma GE Millennium MG utilizando la plataforma GATE Monte Carlo. MATERIAL Y MÉTODOS: El tamaño y espesor del cristal, la colimación de agujeros paralelos y una ventana de adquisición de energía realista se simularon en la plataforma GATE. Los resultados GATE se compararon con los datos experimentales en las siguientes condiciones de formación de imágenes: fuente puntual 99mTc en diferentes posiciones durante la adquisición de imágenes estáticas y tomográficas utilizando 2 diferentes ventanas de energía. La precisión entre los eventos esperados y detectados por simulación se realizó utilizando la prueba de Mann-Whitney-Wilcoxon. Las comparaciones se hicieron con respecto a las medidas de los parámetros sensibilidad y resolución espacial, estáticas y tomográficas. Las resoluciones espaciales simulada y experimental de los datos tomográficos se compararon con la prueba de Kruskal-Wallis. RESULTADOS: Hubo buena concordancia entre los datos simulados y experimentales. El número de decaimientos esperado en comparación con los registrados, ha revelado una pequeña desviación (<=0,007%). Las comparaciones de sensibilidad entre las adquisiciones estáticas, para diferentes distancias desde la fuente al colimador (1, 5, 10, 20, 30 cm) con ventanas de energía de 126-154 keV y 130-158 keV, mostraron diferencias de 4,4; 5,5; 4,2; 5,5; 4,5 y 5,4; 6,3; 6,3; 5,8, y 5,3%, respectivamente. Las comparaciones entre sensibilidad tomográfica fueron 7,5 y 9,8% para la ventana de energía 126-154 keV y 130-158 eV. La comparación de resoluciones espaciales simuladas y experimentales para los datos tomográficos no ha mostrado diferencias estadísticamente significativas con un intervalo de confianza del 95%. CONCLUSIONES: Se ha conseguido efectuar y validar una simulación Monte Carlo con la plataforma GATE de características básicas de funcionamiento de una cámara gamma GE Millennium MG

Comment on "Analysis of the diastolic function by myocardial perfusion gated SPECT after coronary revascularization in acute myocardial infarction" / Comentario a "Análisis de la función diastólica mediante gated-SPECT de perfusión miocárdica tras revascularización coronaria en el infarto agudo de miocardio"

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Authors' reply to "Analysis of the diastolic function by myocardial perfusion gated SPECT after coronary revascularization in acute myocardial infarction" / Réplica a "Análisis de la función diastólica mediante gated-SPECT de perfusión miocárdica tras revascularización coronaria en el infarto agudo de miocardio"

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Clinical value of supine and upright myocardial perfusion imaging in obese patients using the D-SPECT camera.

PURPOSE: We have assessed whether additional upright imaging increases the confidence of interpretation of stress only supine myocardial perfusion imaging (MPI) in obese patients. METHODS AND RESULTS: Tc-MIBI stress MPI of 101 consecutive patients (M = 49, 62 ± 12 years) with BMI ≥30 scanned on the D-SPECT cardiac camera were assessed. Images were interpreted as diagnostic or equivocal and the need for a rest study was recorded. Stress supine MPI was interpreted first, then gated and finally upright data were added. Defects on supine but not on upright were defined as artefacts and defects seen on both as abnormal. The total perfusion deficit (TPD) was also quantified. There were 27 normal, 22 abnormal, and 52 equivocal supine scans. The median EF was 52%, unaffecting the need for rest imaging. Upright imaging reclassified 32/52 (62%) equivocal studies as normal and 6/52 (11%) as abnormal (P < 0.001). Rest scan was deemed needed in 74/101 patients on supine vs 42/101 on supine/upright (P < 0.001). Supine TPD was normal in 53 and supine/upright TPD was normal in 70 patients (P < 0.001). CONCLUSION: Supine stress MPI is inadequate in obese patients. The addition of upright imaging significantly increases the ability to interpret scans as diagnostic and may reduce considerably the need for rest imaging.

Rapid-acquisition myocardial perfusion scintigraphy (MPS) on a novel gamma camera using multipinhole collimation and miniaturized cadmium-zinc-telluride (CZT) detectors: prognostic value and diagnostic accuracy in a 'real-world' nuclear cardiology service.

AIMS: To study the prognostic value of rapid-acquisition adenosine stress-rest myocardial perfusion scintigraphy (MPS) on a gamma camera using multipinhole collimation and cadmium-zinc-telluride (CZT) detectors. The secondary aim was to assess the diagnostic accuracy of the technique compared with invasive coronary angiography. METHODS AND RESULTS: Retrospective analysis of 1109 consecutive patients undergoing MPS in a routine clinical setting on a high-efficiency multipinhole gamma camera. MPS acquisition, performed with a standard injection of 550 MBq of (99m)Tc-tetrofosmin, required a mean (±SD) scanning time of 322 ± 51 s. The hard cardiac event rate at a median (inter-quartile range) follow-up of 624 (552-699) days was 0.4% (95% CI 0.1-1.1) in patients with no significant perfusion abnormality versus 6.8% (95% CI 4.3-10.7%, P < 0.001) in those with an abnormal scan. In a sub-group of 165 patients, comparison with obstructive coronary artery disease on X-ray angiography gave a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for rapid-acquisition MPS of 84% (95% CI 74-91), 79% (95% CI 68-87), 82% (95% CI 72-89), 81% (95% CI 70-89), and 82% (95% CI 73-89), respectively. CONCLUSIONS: MPS performed on a CZT solid-state detector camera with multipinhole collimation is an evolutionary development that provides reliable prognostic and diagnostic information, while significantly reducing image acquisition time.

Gated SPECT evaluation of left ventricular function using a CZT camera and a fast low-dose clinical protocol: comparison to cardiac magnetic resonance imaging.

PURPOSE: CZT technology allows ultrafast low-dose myocardial scintigraphy but its accuracy in assessing left ventricular function is still to be defined. METHODS: The study group comprised 55 patients (23 women, mean age 63 ± 9 years) referred for myocardial perfusion scintigraphy. The patients were studied at rest using a CZT camera (Discovery NM530c; GE Healthcare) and a low-dose (99m)Tc-tetrofosmin clinical protocol (mean dose 264 ± 38 MBq). Gated SPECT imaging was performed as a 6-min list-mode acquisition, 15 min after radiotracer injection. Images were reformatted (8-frame to 16-frame) using Lister software on a Xeleris workstation (GE Healthcare) and then reconstructed with a dedicated iterative algorithm. Analysis was performed using Quantitative Gated SPECT (QGS) software. Within 2 weeks patients underwent cardiac magnetic resonance imaging (cMRI, 1.5-T unit CVi; GE Healthcare) using a 30-frame acquisition protocol and dedicated software for analysis (MASS 6.1; Medis). RESULTS: The ventricular volumes obtained with 8-frame QGS showed excellent correlations with the cMRI volumes (end-diastolic volume (EDV), r = 0.90; end-systolic volume (ESV), r = 0.94; p < 0.001). However, QGS significantly underestimated the ventricular volumes (mean differences: EDV, -39.5 ± 29 mL; ESV, -15.4 ± 22 mL; p < 0.001). Similarly, the ventricular volumes obtained with 16-frame QGS showed an excellent correlations with the cMRI volumes (EDV, r = 0.92; ESV, r = 0.95; p < 0.001) but with significant underestimations (mean differences: EDV, -33.2 ± 26 mL; ESV, -17.9 ± 20 mL; p < 0.001). Despite significantly lower values (47.9 ± 16 % vs. 51.2 ± 15 %, p < 0.008), 8-frame QGS mean ejection fraction (EF) was closely correlated with the cMRI values (r = 0.84, p < 0.001). The mean EF with 16-frame QGS showed the best correlation with the cMRI values (r = 0.91, p < 0.001) and was similar to the mean cMRI value (49.6 ± 16 %, p not significant). Regional analysis showed a good correlation between both 8-frame and 16-frame QGS and cMRI wall motion score indexes (8-frame WMSI, r = 0.85; 16-frame WMSI, r = 0.89; p < 0.01). CONCLUSION: Low-dose gated SPECT with a CZT camera provides ventricular volumes that correlate well with cMRI results despite significant underestimation in the measure values. EF estimation appeared to be more accurate with 16-frame reformatted images than with 8-frame images.

Análisis de la función diastólica mediante gated-SPECT de perfusión miocárdica tras revascularización coronaria en el infarto agudo de miocardio / Analysis of the diastolic function by myocardial perfusion gated SPECT after coronary revascularization in acute myocardial infarction

Objetivo. Valorar mediante gated-SPECT de perfusión miocárdica los cambios evolutivos de la función diastólica después de la revascularización coronaria percutánea (RCP) de un infarto agudo de miocardio (IAM). Material y métodos. Se estudiaron consecutivamente 32 pacientes (media 61,9±9,7 años; 7 mujeres) mediante 2 gated-SPECT de perfusión miocárdica en reposo: la primera gated-SPECT-1 con inyección de una dosis de 99mTc-tetrofosmina previa a la RCP y la segunda gated-SPECT-2 entre la cuarta y quinta semana después del IAM. Se valoraron los cambios de la velocidad máxima de llenado (Vmáx) y del tiempo a la velocidad máxima de llenado (TVmáx) entre ambos estudios, relacionándolos con la extensión del miocardio salvado (MS) y con los cambios observados en los volúmenes telediastólico (VTD) y telesistólico (VTS) y en la fracción de eyección del ventrículo izquierdo (FEVI). Resultados. En la gated-SPECT-2 se observó una mejoría de los parámetros de la función diastólica: la Vmáx aumentó significativamente (p = 0,011) mientras que el TVmáx disminuyó sin alcanzar significación estadística (p = 0,288). En el análisis multivariante, ajustado por variables clínicas y coronariográficas, el aumento de la Vmáx se relacionó significativamente con el porcentaje de MS (p = 0,030), el aumento de la FEVI (p = 0,004) y la reducción del VTS (p = 0,005). La mejoría del TVmáx solo se relacionó significativamente con el porcentaje de MS (p = 0,046). Por cada cm2 de aumento del área del MS la Vmáx aumentó 0,01 VTD/s y la TVmáx disminuyó 1,14 ms. Conclusiones. Tras la RCP en el IAM, la gated-SPECT de perfusión miocárdica permite valorar la mejoría significativa de la función diastólica que se relaciona fundamentalmente con la cantidad de MS (AU)

Objective. To evaluate the evolutive changes in diastolic function after percutaneous coronary revascularization (PCR) in acute myocardial infarction (AMI), using myocardial perfusion gated SPECT. Material and methods. Thirty-two patients (mean 61.9±9.7 years, 7 women) were studied by two at rest gated SPECT: the first gated-SPECT-1 was performed with an injection of a dose of 99mTc-tetrofosmin prior to PCR and the second gated-SPECT-2 between the fourth and fifth weeks after AMI. Changes of peak filling rate (PFR) and the time to peak filling rate (TTPF) were assessed between both studies, and were related to the extent of salvaged myocardium (SM), end-diastolic (EDV) and end-systolic (ESV) volumes, and left ventricular ejection fraction (LVEF) changes. Results. An improvement was observed in diastolic function parameters Gated-SPECT-2: PFR increased significantly (P=0.011) while the TTPF decreased without reaching statistical significance (P=0.288). In multivariate analysis, adjusted by clinical and coronary variables, improvement of PFR was significantly associated with percentage of SM (P=0.030), increase in LVEF (P=0.004) and with ESV volume reduction (P=0.005). Improvement of TTPF was only related significantly to the percentage of SM (P=0.046). PFR increased 0.01 EDV/sec. and TTPF decreased 1.14ms for each cm2 increase of the area of SM. Conclusions. After PCR in AMI, the myocardial perfusion gated SPECT makes it possible to assess the significant improvement in diastolic function mainly related to the amount of MS (AU)

Multimodality molecular imaging in the evaluation of pheochromocytoma. A case report / Imagen molecular multimodal en la evaluación de un feocromocitoma. A propósito de un caso

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Improved quantification in pinhole gated myocardial perfusion SPECT using micro-CT and ultrasound information.

Absolute quantification using single photon emission computed tomography (SPECT) was demonstrated in vitro and in large immobile organs in vivo. To determine the feasibility of in vivo quantification of myocardial perfusion in pinhole gated SPECT, we added an ultrasound derived partial volume correction factor to attenuation and scatter corrections, in combination with gated acquisitions. In nine male Wistar rats, cardiac ultrasound was performed prior to SPECT/CT scans to determine the myocardial wall thickness. SPECT/CT scans were then performed 30 min after injection of (99m) Tc Tetrofosmin. Animals were killed and six midventricular segments of the left ventricle were excised and counted in a γ-well counter. Using AMIDE, regional myocardial activity was measured after combined scatter correction (SC) and attenuation correction (AC). These image derived activities were compared with the ex vivo counted activity. To correct for the partial volume effect, a recovery coefficient was determined from a phantom study, to determine the thickness specific partial volume effect. Combined AC and SC led to a significant underestimation of activity compared with ex vivo data (root mean squared error = 0.145 mCi g(-1)). The recovery coefficient calculated from the phantom study showed a linear relationship with object size from 1 to 6 mm, positioned in the vicinity of the center of the field of view (R(2) = 0.98). Correction of nongated SPECT images with a recovery coefficient derived from the diastolic phase results in a global overestimation with root mean squared error = 0.04 mCi g(-1). Nongated SPECT images corrected with a recovery coefficient with a weighted average ratio diastolic and systolic phase led to an improved root mean squared error of 0.03 mCi g(-1). Combining attenuation correction with scatter correction and a gated partial volume correction yields the best correlation with ex vivo counting (root mean squared error = 0.021 mCi g(-1) (systolic) and 0.025 mCi g(-1) (diastolic). This study demonstrates a method for improved segmental myocardial perfusion quantification in pinhole gated SPECT, using combined attenuation-, scatter- and ultrasound-derived partial volume effect corrections.

Effects of motion, attenuation, and scatter corrections on gated cardiac SPECT reconstruction.

PURPOSE: In gated cardiac single photon emission computed tomography (SPECT), image reconstruction is often hampered by various degrading factors including depth-dependent spatial blurring, attenuation, scatter, motion blurring, and low data counts. Consequently, there has been significant development in image reconstruction methods for improving the quality of reconstructed images. The goal of this work is to investigate how these degrading factors will impact the reconstructed myocardium when different reconstruction methods are used. METHODS: The authors conduct a comparative study of the effects of these degrading factors on the accuracy of myocardium by several reconstruction algorithms, including (1) a clinical spatiotemporal processing method, (2) maximum likelihood (ML) estimation, (3) 3D maximum a posteriori (MAP) estimation, (4) 3D MAP with posttemporal filtering, and (5) motion-compensated spatiotemporal (4D) reconstruction. To quantify the reconstruction results, the authors use the following measures on different aspects of the myocardium: (1) overall error level in the myocardium, (2) regional accuracy of the left ventricle (LV) wall, (3) uniformity of the LV, (4) accuracy of regional time activity curves by normalized cross-correlation coefficient, and (5) perfusion defect detectability. The authors also assess the effectiveness of degrading corrections in reconstruction by considering an upper bound for each reconstruction method, which represents what would be achieved by each method if the acquired data were free from attenuation and scatter degradations. In the experiments the authors use Monte Carlo simulated cardiac gated SPECT imaging based on the 4D NURBS-based cardiac-torso (NCAT) phantom with different patient geometry and lesion settings, in which the simulated ground truth is known for the purpose of quantitative evaluation. RESULTS: The results demonstrate that use of temporal processing in reconstruction (Methods 1, 4, and 5 above) can greatly improve the reconstructed myocardium in terms of both error level and perfusion defect detection. In low-count gated studies, it can have even greater impact than other degrading factors. Both attenuation and scatter corrections can lead to reduced error levels in the myocardium in all methods; in particular, with 4D the bias can be reduced by as much as four-fold compared to no correction. There is a slight increase in noise level observed with scatter correction. A significant improvement in heart wall appearance is demonstrated in reconstruction results from three sets of clinical acquisitions as correction for degradations is combined with refinement of temporal filtering. CONCLUSIONS: Correction for degrading factors such as resolution, attenuation, scatter, and motion blur can all lead to improved image quality in cardiac gated SPECT reconstruction. However, their effectiveness could also vary with the reconstruction algorithms used. Both attenuation and scatter corrections can effectively reduce the bias level of the reconstructed LV wall, though scatter correction is also observed to increase the variance level. Use of temporal processing in reconstruction can have greater impact on the accuracy of the myocardium than correction of other degrading factors. Overall, use of degrading corrections in 4D reconstruction is shown to be most effective for improving both reconstruction accuracy of the myocardium and detectability of perfusion defects in gated images.