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(1) Background: The CT-based attenuation correction of SPECT images is essential for obtaining accurate quantitative images in cardiovascular imaging. However, there are still many SPECT cameras without associated CT scanners throughout the world, especially in developing countries. Performing additional CT scans implies troublesome planning logistics and larger radiation doses for patients, making it a suboptimal solution. Deep learning (DL) offers a revolutionary way to generate complementary images for individual patients at a large scale. Hence, we aimed to generate linear attenuation coefficient maps from SPECT emission images reconstructed without attenuation correction using deep learning. (2) Methods: A total of 384 SPECT myocardial perfusion studies that used 99mTc-sestamibi were included. A DL model based on a 2D U-Net architecture was trained using information from 312 patients. The quality of the generated synthetic attenuation correction maps (ACMs) and reconstructed emission values were evaluated using three metrics and compared to standard-of-care data using Bland-Altman plots. Finally, a quantitative evaluation of myocardial uptake was performed, followed by a semi-quantitative evaluation of myocardial perfusion. (3) Results: In a test set of 66 test patients, the ACM quality metrics were MSSIM = 0.97 ± 0.001 and NMAE = 3.08 ± 1.26 (%), and the reconstructed emission quality metrics were MSSIM = 0.99 ± 0.003 and NMAE = 0.23 ± 0.13 (%). The 95% limits of agreement (LoAs) at the voxel level for reconstructed SPECT images were: [-9.04; 9.00]%, and for the segment level, they were [-11; 10]%. The 95% LoAs for the Summed Stress Score values between the images reconstructed were [-2.8, 3.0]. When global perfusion scores were assessed, only 2 out of 66 patients showed changes in perfusion categories. (4) Conclusion: Deep learning can generate accurate attenuation correction maps from non-attenuation-corrected cardiac SPECT images. These high-quality attenuation maps are suitable for attenuation correction in myocardial perfusion SPECT imaging and could obviate the need for additional imaging in standalone SPECT scanners.
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Introducción: En nuestro medio se desconoce cuál ha sido la influencia de la evidencia clínica sobre las estrategias implementadas en el tratamiento de los síndromes coronarios agudos sin elevación del segmento ST (SCASEST). Objetivos: Evaluar la variación de las características clínicas, las estrategias adoptadas, las conductas terapéuticas y los eventos hospitalarios de los SCASEST en centros que participaron en dos registros realizados en la Argentina. Material y métodos: Se compararon pacientes incluidos en centros que participaron en los registros STRATEG-SIA (1999) y SCAR (Síndromes Coronarios Agudos en Argentina - 2011). Resultados: Se analizaron 238 pacientes del registro STRATEG-SIA y 452 del SCAR incluidos en 36 centros. La mayoría eran de género masculino y menores de 65 años (SCAR 57%, STRATEG-SIA 54%; p = ns). El grupo SCAR presentó mayor prevalencia de hipertensión arterial (75% vs. 60%; p = 0,001), dislipidemia (63% vs. 51%; p = 0,003), insuficiencia cardíaca crónica (10,5% vs. 4,6%; p = 0,02) y revascularización coronaria previa (30% vs. 17%; p = 0,001). Con una proporción mayor de puntaje TIMI de riesgo moderado y alto (3-4: 48% vs. 37%; 5-7: 18% vs. 8%; p = 0,0001), la coronariografía fue más frecuente en el SCAR (71% vs. 50%; p = 0,0001), duplicándose la angioplastia coronaria y reduciéndose a la mitad las cirugías de revascularización miocárdica. No hubo diferencias significativas en la tasa intrahospitalaria de muerte e infarto (7,2% vs. 5,9%; p = ns). Conclusiones: Los pacientes del registro SCAR (2011) representan un grupo de mayor riesgo. Las diferencias en las tasas de eventos hospitalarios no fueron estadísticamente significativas.
Background: The influence of clinical evidence on strategies implemented in the treatment of non-ST-segment elevation acute coronary syndromes (NSTEACS) is not known in our setting. Objectives: The aim of this study was to evaluate the differences in clinical characteristics, strategies adopted, therapeutic management and in-hospital events of NSTEACS in participating centers from two registries in Argentina. Methods: Patients included in participating centers of the STRATEG-SIA registry (1999) and SCAR registry (Síndromes Coronarios Agudos en Argentina - 2011) were compared. Results: We analyzed 238 patients of the STRATEG-SIA registry and 452 of the SCAR registry in 36 centers. Most patients were men and <65 years (SCAR 57%, STRATEG-SIA 54%; p=ns). The SCAR group presented higher prevalence of hypertension (75% vs. 60%; p=0.001), dyslipidemia (63% vs. 51%; p=0.003), chronic heart failure (10.5% vs. 4.6%; p=0.02) and history of myocardial revascularization (30% vs. 17%; p=0.001). In the SCAR registry, the proportion of moderate and high-risk patients (TIMI risk score 3-4: 48% vs. 37%; 5-7: 18% vs. 8%; p=0.0001) was higher and coronary angiography was more frequent (71% vs. 50%; p=0.0001), with a twofold increase in the proportion of percutaneous coronary interventions and 50% reduction in the number of myocardial revascularization surgeries. There were no significant differences in the rate of mortality and myocardial infarction during hospitalization (7.2% vs. 5.9%; p=ns). Conclusions: Patients of the SCAR (2011) registry represent a group at higher risk. The differences in the rates of in-hospital events were not statistically significant.
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Introducción La relación entre la viabilidad, el flujo miocárdico y el grado de estenosis epicárdica en pacientes con enfermedad coronaria y disfunción ventricular izquierda está poco investigada. Objetivo Determinar si los patrones de viabilidad por tomografía por emisión de positrones (PET) y el flujo miocárdico en reposo se relacionan con el grado de estenosis epicárdica. Material y métodos Se evaluó la viabilidad en 27 pacientes mediante el análisis combinado de la perfusión con 13N-amonio (13NH3) y el metabolismo con 18F-fluoro-2-desoxiglucosa (FDG) para identificar cuatro patrones PET: match (hipocaptación concordante de ambos radiotrazadores), mismatch (hipoperfusión con captación preservada de FDG), mismatch inverso (perfusión preservada e hipocaptación de FDG) y perfusión/metabolismo conservados. El flujo absoluto se calculó mediante un modelo bicompartimental. Las estenosis se clasificaron en leves ( 50%), graves (> 70%) y críticas (= 90%). Resultados De 459 segmentos resultaron match el 33%, mismatch el 12%, mismatch inverso el 11% y conservado el 44%. El flujo para mismatch, mismatch inverso y conservado fue mayor que para los segmentos con match (p < 0,01). Quince lesiones fueron leves, 7 moderadas, 20 graves y 39 críticas. No hubo correlación entre el grado de estenosis y los patrones de viabilidad (R < 0,2; p = ns) ni con los valores de flujo (R = 0,12). El análisis por territorio vascular no mostró correlación con el grado de estenosis (p = ns). Conclusiones No hubo correlación entre los patrones PET, el grado de estenosis epicárdica y el flujo mio-cárdico, lo que sugiere que la anatomía coronaria no puede discriminar miocardio viable del necrótico ni predecir el estado del flujo miocárdico en pacientes con disfunción ventricular izquierda.
Background The relationship between myocardial viability, myocardial flow and the degree of epicardial coronary stenosis in patients with coronary artery disease and left ventricular dysfunction is unclear. Objective The purpose of this study is to determine whether positron emission tomography (PET) viability and myocardial flow at rest correlate with the degree of epicardial coronary stenosis. Methods Myocardial viability was evaluated in 27 patients by the combined analysis of 13N-Ammonia (13NH3) perfusion and 18F-fluoro-2-deoxyglucose (FDG) metabolism to identify four PET patterns: match (concordant reduced uptake of both radiotracers), mismatch (hypoperfusion with preserved FDG uptake), reverse mismatch (preserved perfusion and reduced FDG uptake) and preserved uptake of both radiotracers. Myocardial blood flow was calculated using a two-compartment model. Coronary artery stenosis was classified as mild (50%), severe (>70%) and critical (= 90%). Results From 459 analyzed segments, 33% were match, 12% mismatch, 11% reverse-mismatch and 44% preserved. Mismatch, reverse-mismatch and preserved patterns exhibited higher flows than the match pattern (p < 0.01). Fifteen coronary lesions were mild, 7 moderate, 20 severe and 39 critical. There was no correlation between the degree of coronary stenosis and viability patterns (R< 0.2, p=NS) or blood flow values (R=0.12). Analysis by vascular territory did not correlate with the degree of coronary stenosis (p=NS). Conclusions Lack of correlation between PET viability patterns, degree of epicardial stenosis and myocardial blood flow suggest that coronary anatomy can neither differentiate viable from necrotic myocardium nor predict the functional status of myocardial flow in patients with left ventricular dysfunction.
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OBJECTIVES: Thallium-201 is efficient for myocardial perfusion imaging, but leads to relatively high radiation exposure in patients. The purpose of this study was to compare the efficiency of low-dose thallium-201 imaging with cadmium-zinc-telluride (CZT) cameras with regular-dose thallium-201 imaging with conventional cameras. METHODS: We prospectively studied 137 consecutive patients referred for stress myocardial perfusion imaging who had previously had a myocardial single-photon emission computed tomography with thallium-201. We injected at stress a low dose of thallium-201 (1.1 MBq/kg, 28 µCi/kg), performed a 5-7 min scan with a CZT camera (GE DNM 530c), and assessed redistribution imaging when the initial images were abnormal. We compared the CZT scan with the conventional dual-head tomographic camera scan taken previously with a regular dose of thallium-201. RESULTS: The average delay between both scans was 22 months. The stress dose was 88 ± 16 (2.38 ± 0.43 mCi) versus 125 ± 13 MBq (3.38 ± 0.34 mCi; a 30% reduction). The time for camera acquisition was 6 versus 13 min (a 54% reduction). The myocardial counts were increased two-fold with CZT (mean: 446 Kcounts). The quality of CZT images was better in 69% of the cases. There were 59 artifacts with conventional cameras and 29 artifacts with CZT (P<0.01). The diagnostic agreement was calculated in patients without clinical or angiographic changes between both scans (115 patients) and was high (97%). The effective dose at stress was less than 12 mSv. High myocardial counting allowed for further decrease in the injected activity, leading to an effective dose as low as 8 mSv. CONCLUSION: With reduced activities of thallium-201 and low effective doses, the CZT camera provides reliable, high-quality imaging.
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Imagen de Perfusión Miocárdica/instrumentación , Radioisótopos de Talio/administración & dosificación , Anciano , Cadmio , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Dosis de Radiación , Reproducibilidad de los Resultados , Telurio , ZincRESUMEN
PURPOSE OF THE REPORT: Cadmium zinc telluride (CZT) solid-state detectors have been recently introduced in myocardial perfusion imaging. However, they had not been yet validated with thallium-201. This study compares the clinical performances of the CZT ultrafast camera GE DNM 530c with a conventional SPECT camera (CC) using thallium-201. MATERIALS AND METHODS: We prospectively studied with thallium-201 a total of 153 consecutive patients referred for myocardial perfusion imaging at exercise (3-4 mCi) then redistribution (with 1 mCi reinjection). Sequential acquisitions were performed first with a conventional dual-head tomographic Anger camera (CC) in 10 to 15 minutes and then with a CZT camera (CZT) in 5 minutes, in prone position. RESULTS: In all, 9 patients were excluded: 1 for mispositioning, 3 for camera failure, 3 for delayed acquisition after exercise, 1 for nonacceptance of redistribution, 1 for motion. Acquisition was more comfortable with CZT for all patients. Global counts rate was higher with CZT than with CC (3.6±0.57 KCts/s vs. 1.14±0.16). CZT has a 5-fold increased myocardial counts rate compared with CC (448±69 Kcts in 5 minutes vs. 209±40 Kcts in 12.5±1.8 minutes). Quality of CZT images was considered as better in 40%, equal in 56%, and worse in 4% of cases; we found less artifacts with CZT; diagnostic conclusions were the same in 140 of 144 cases (97%); discordances were 2 artifacts with CC and 2 small ischemia (less than 2 segments) missed by CZT. CONCLUSIONS: This new dedicated cardiac CZT camera allows with thallium-201 five minutes acquisitions with an increased image quality and a reliable diagnosis quality.