Search Results (143)

Background: Cardiac-respiratory dual gating in SPECT (DG-SPECT) is an emergent technique for alleviating motion blurring artifacts in myocardial perfusion imaging (MPI) due to both cardiac and respiratory motions. Moreover, the attenuation artifact may arise from the spatial mismatch between the sequential SPECT and CT attenuation scans due to the dual gating of SPECT data and non-gating CT images. Objectives: This study adapts a four-dimensional (4D) cardiac SPECT reconstruction with post-reconstruction respiratory motion correction (4D-RMC) for dual-gated SPECT. In theory, a respiratory motion-matched attenuation correction (MAC) method is expected to yield more accurate reconstruction results than the conventional motion-averaged attenuation correction (AAC) method. However, its potential benefit is not clear in the presence of practical imaging artifacts in DG-SPECT. In this study, we aim to quantitatively investigate these two attenuation methods for SPECT MPI: 4D-RMC (MAC) and 4D-RMC (AAC). Methods: DG-SPECT imaging (eight cardiac gates and eight respiratory gates) of the NCAT phantom was simulated using SIMIND Monte Carlo simulation, with a lesion (20% reduction in uptake) introduced at four different locations of the left ventricular wall: anterior, lateral, septal, and inferior. For each respiratory gate, a joint cardiac motion-compensated 4D reconstruction was used. Then, the respiratory motion was estimated for post-reconstruction respiratory motion-compensated smoothing for all respiratory gates. The attenuation map averaged over eight respiratory gates was used for each respiratory gate in 4D-RMC (AAC) and the matched attenuation map was used for each respiratory gate in 4D-RMC (MAC). The relative root mean squared error (RMSE), structural similarity index measurement (SSIM), and a Channelized Hotelling Observer (CHO) study were employed to quantitatively evaluate different reconstruction and attenuation correction strategies. Results: Our results show that the 4D-RMC (MAC) method improves the average relative RMSE by as high as 5.42% and the average SSIM value by as high as 1.28% compared to the 4D-RMC (AAC) method. Compared to traditional 4D reconstruction without RMC (“4D (MAC)”), these metrics were improved by as high as 11.23% and 27.96%, respectively. The 4D-RMC methods outperformed 4D (without RMC) on the CHO study with the largest improvement for the anterior lesion. However, the image intensity profiles, the CHO assessment, and reconstruction images are very similar between 4D-RMC (MAC) and 4D-RMC (AAC). Conclusions: Our results indicate that the improvement of 4D-RMC (MAC) over 4D-RMC (AAC) is marginal in terms of lesion detectability and visual quality, which may be attributed to the simple NCAT phantom simulation, but otherwise suggest that AAC may be sufficient for clinical use. However, further evaluation of the MAC technique using more physiologically realistic digital phantoms that incorporate diverse patient anatomies and irregular respiratory motion is warranted to determine its potential clinical advantages for specific patient populations undergoing dual-gated SPECT myocardial perfusion imaging. Full article

Takotsubo Cardiomyopathy (TTC), often referred to as stress-induced or “broken heart” syndrome, is characterized by transient left ventricular dysfunction predominantly involving apical hypokinesia and basal hyperkinesia in the absence of obstructive coronary artery disease. Traditionally viewed as an acute and reversible phenomenon, accumulating evidence suggests that TTC may emerge from a preexisting myocardial substrate shaped by chronic stress and hemodynamic loading. Basal Septal Hypertrophy (BSH), a morphological finding commonly observed in elderly, hypertensive, or emotionally stressed individuals, has been increasingly recognized in patients with TTC. This hypertrophic pattern, often accompanied by dynamic contractile gradients and regional perfusion mismatch, reflects a broader adaptive remodeling process conceptualized as Stressed Heart Morphology (SHM). SHM encompasses the structural and functional myocardial responses to cumulative neurohormonal and mechanical stress, with BSH representing a key imaging marker within this spectrum. Advanced echocardiographic techniques, such as tissue Doppler imaging, speckle-tracking strain analysis, and stress echocardiography, consistently reveal overlapping features between SHM and TTC, including basal hyperkinesis, septal thickening, and inducible left ventricular outflow tract obstruction. These findings support a continuum in which SHM serves as a predisposing substrate for TTC, representing a stress-provoked clinical expression within a unified myocardial stress–response framework. Full article

Attenuation correction (AC) is an essential process in Single Photon Emission Computed Tomography (SPECT) myocardial perfusion imaging (MPI), an established imaging method for assessing coronary artery disease. Conventional AC approaches typically require CT scans, supplementary hardware, intricate reconstruction, or segmentation processes, which can hinder their clinical applicability. Recently, deep learning (DL) techniques have emerged as alternatives, allowing for the direct learning of attenuation patterns from non-AC (NAC) imaging data. This review explores the existing literature on DL-based AC methods for SPECT MPI. We highlight high-performing models, including attention-gated U-Net conditional Generative Adversarial Networks (GANs), and evaluate their validation methods. Although significant advancements have been achieved, numerous challenges persist, which are thoroughly discussed. Full article

Occupational radiation exposure in nuclear medicine presents complex spatial and temporal patterns due to the use of unsealed radiopharmaceuticals and prolonged proximity to patients. Traditional passive dosimetry provides only cumulative dose values, limiting its usefulness in identifying task-specific exposures or capturing momentary fluctuations. This study applied a real-time dosimetry system capable of second-by-second measurements, combined with time-series analysis, to evaluate staff exposure during myocardial perfusion imaging using technetium-99m. Dosimeters were placed on the left and right sides of the neck and head of two radiological technologists. Dose rates were continuously recorded throughout the injection and imaging phases. The right side of the neck received the highest cumulative and peak dose rates among all sites. Although no significant difference in total dose was observed between the injection and imaging phases, specific high-exposure events were detected. Notably, ECG lead placement and post-injection handling produced dose spikes. A positive correlation was found between administered activity and dose rate at neck-level sites but not at head-level sites. These findings demonstrate the value of real-time dosimetry in identifying procedural actions associated with elevated exposure. Time-series analysis further contextualized these peaks, supporting improved task-specific protective strategies beyond the capabilities of conventional dosimetry. Full article

Purpose: While peak oxygen uptake ($\stackrel{.}{\mathrm{V}}$O_2peak) is the gold standard method for assessing exercise tolerance, there is a tendency for underestimation. Several other cardiopulmonary exercise testing (CPET) variables may provide additive prognostic value beyond $\stackrel{.}{\mathrm{V}}$O_2peak alone. The aim of this study was to examine if alternative CPET indices of exercise tolerance are (a) impaired in people with T2D and (b) independently associated with measures of cardiovascular structure and function measured via echocardiography and cardiac MRI. Methods: Participants with type 2 diabetes (T2D) and healthy controls underwent cardiac magnetic resonance imaging, transthoracic echocardiography, and a CPET. Multiple linear regression was used to determine the relationship between indices of exercise tolerance and markers of cardiovascular structure and function. Results: A total of 84 people with T2D and 36 healthy volunteers were included in the analysis. All CPET outcomes were worse in those with T2D vs. the controls. Three CPET outcomes were associated with markers of cardiovascular structure and function: $\stackrel{.}{\mathrm{V}}$O₂ recovery with mean aortic distensibility (β = 0.218, p = 0.049); heart rate recovery with early filling velocity on transmitral Doppler/early relaxation velocity (β = −0.270, p = 0.024), left ventricular mass/volume ratio (β = −0.248, p = 0.030) and mean aortic distensibility (β = 0.222, p = 0.029); and $\stackrel{.}{\mathrm{V}}$O₂ at the ventilatory threshold with myocardial perfusion reserve (β = 0.273, p = 0.018). Perspective: These lesser-used CPET indices could be used to identify which people with T2D are at elevated risk of progression to symptomatic heart failure. However, larger longitudinal studies are required to confirm these findings and their potential clinical application. Full article

Myocardial bridging (MB) is a congenital coronary anomaly whose clinical impact remains controversial. Coronary computed tomography angiography (CCTA) combined with CT myocardial perfusion imaging (CT-MPI) enables a comprehensive anatomical and functional assessment of MB. This study aimed to investigate whether specific high-risk anatomical features of MB are independently associated with myocardial hypoperfusion, using combined CCTA and CT-MPI. We retrospectively analyzed 81 patients with MB showing high-risk anatomical features (depth ≥ 2.0 mm and length ≥ 25 mm) identified by CCTA, all of whom underwent stress dynamic CT-MPI between May 2022 and December 2025. Patients were classified according to the presence or absence of hypoperfusion in MB-related myocardial segments. Clinical and anatomical variables were compared between two groups using non-parametric tests, and multivariable logistic regression was performed to identify independent predictors of hypoperfusion. Among the 81 patients (mean age, 59.3 ± 11.7 years; 54 males), 26 (32.1%) demonstrated perfusion defects. All MBs were located in the left anterior descending artery (LAD). No significant differences were observed in clinical variables between groups. Bridges associated with hypoperfusion were significantly deeper (p < 0.001) and were more frequently located in the mid-LAD (73.1% vs. 38.2%, p = 0.01). In multivariable analysis, bridge depth and mid-LAD location remained independent predictors of hypoperfusion. In patients with MB, greater depth and mid-LAD location are independently associated with myocardial hypoperfusion. The combined use of CCTA and CT-MPI may enhance risk stratification and help guide clinical decision-making in this patient population. Full article

Ultrasound enhancing agents (UEAs, formerly called contrast agents) have enhanced echocardiographic diagnostics of myocardial disease and masses as well as myocardial perfusion abnormalities. This review provides up-to-date guidance on the procedures and interpretations according to current recommendations of imaging societies and considering the results of recent major studies. For the different indications, a standardized approach has been created including technical aspects, pre-assessment and primary scan planes, contrast-enhanced ultrasound (CEUS) procedure, interpretation and reporting. In a previous publication (part 1) the UEAs, imaging methods, preparation of the patients and assessment of global and regional LV function with UEAs were included. The two parts represent a comprehensive state-of-the-art compendium on how to perform CEUS examinations in clinical echocardiography and provide advice on education, qualification and quality control. Full article

Background/Objectives: To validate an artificial intelligence-based arterial input function (AI-AIF) deep learning model for myocardial blood flow (MBF) quantification during stress perfusion and assess its extension to rest perfusion, enabling myocardial perfusion reserve (MPR) calculation. Methods: Sixty patients with or at risk for vascular cognitive impairment, prospectively enrolled in the CRUCIAL consortium, underwent quantitative stress and rest myocardial perfusion imaging using a 3 T MRI system. Perfusion imaging was performed using a dual-sequence (DS) protocol after intravenous administration of 0.05 mmol/kg gadobutrol. Retrospectively, the AI-AIF was estimated from standard perfusion images using a 1-D U-Net model trained to predict an unsaturated AIF from a saturated input. MBF was quantified using Fermi function-constrained deconvolution with motion compensation. MPR was calculated as the stress-to-rest MBF ratio. MBF and MPR estimates from both AIF methods were compared using Bland–Altman analyses. Results: Complete stress and rest perfusion datasets were available for 31 patients. A bias of −0.07 mL/g/min was observed between AI-AIF and DS-AIF for stress MBF (median 2.19 vs. 2.30 mL/g/min), with concordant coronary artery disease classification based on the optimal MBF threshold in over 92% of myocardial segments and coronary arteries. Larger biases of 0.12 mL/g/min and −0.30 were observed for rest MBF (1.12 vs. 1.02 mL/g/min) and MPR (2.31 vs. 1.84), respectively, with lower concordance using the optimal MPR threshold (85% of segments, 72% of arteries). Conclusions: The AI-AIF model showed comparable performance to DS-AIF for stress MBF quantification but requires further training for accurate rest MBF and MPR assessment. Full article

Background/Objectives: Artificial Intelligence (AI) is becoming increasingly important in Medicine. The aim of this review is to summarize its use in the field of Nuclear Cardiology. Methods: First, we provide a short description of how AI works. Then we performed a review of the literature focusing on the articles in which AI is used for image interpretation for diagnostic or prognostic purposes. Results: AI has been applied according to various approaches for both diagnosis and prognosis. The achieved gains have been so far relatively limited as compared to traditional methodologies. However, promising results have been reported, including interesting perspectives for the explainability of AI results and their potential integration in clinical routine. Conclusions: AI is soon going to play an important role in Nuclear Cardiology, but further improvements are needed to reach significant gains in terms of diagnostic accuracy, and prospective studies on its prognostic capabilities are still lacking. Furthermore, several important issues must be solved, such as availability and feasibility within the processing workflow, explainability, liability, and ethics of its application in clinical decision-making. Full article

Imaging techniques such as positron emission tomography/computed tomography (PET/CT) and positron emission tomography/magnetic resonance imaging (PET/MR) have emerged as powerful and versatile tools for the comprehensive assessment of coronary artery disease (CAD). By combining anatomical and functional information in a single examination, these modalities offer complementary insights that significantly enhance diagnostic accuracy and support clinical decision-making. This is particularly relevant in complex clinical scenarios, such as multivessel disease, balanced ischemia, or suspected microvascular dysfunction, where conventional imaging may be inconclusive. This review aims to provide clinicians with an up-to-date summary of the principles, technical considerations, and clinical applications of hybrid PET/CT and PET/MR in CAD. Here, we describe how these techniques can improve the evaluation of myocardial perfusion, coronary plaque characteristics, and ischemic burden. Advantages such as improved sensitivity, spatial resolution, and quantification capabilities are discussed alongside limitations including cost, radiation exposure, availability, and workflow challenges. A dedicated focus is given to the emerging role of artificial intelligence (AI), which is increasingly being integrated to optimize image acquisition, fusion processes, and interpretation. AI has the potential to streamline hybrid imaging and promote a more personalized and efficient management of CAD. Finally, we outline future directions in the field, including novel radiotracers, automated quantitative tools, and the expanding use of hybrid imaging to guide patient selection and therapeutic decisions, particularly in revascularization strategies. Full article

The “Movahed sign” refers to the presence of a D-shaped left ventricle on cross-sectional cardiac imaging due to interventricular septal flattening seen during cardiac gated single-photon emission computed tomography (SPECT) This phenomenon arises from significant right ventricular (RV) pressure or volume overload, which pushes the septum toward the left ventricle (LV) and distorts the LV’s normally circular profile into a “D” shape. However, the prevalence and incidence of similar findings during cardiac Magnetic Resonance Imaging (MRI) or computed tomography (CT) are not known. The goal of this study was to perform a literature search focusing on the “Movahed sign” or D-shaped left ventricle in the context of cardiac MRI and CT. Databases searched included PubMed and Google Scholar, and reference lists of relevant articles were reviewed. The echocardiography literature was also consulted for foundational concepts of septal flattening. Key data on pathophysiology, imaging features, clinical correlations, and prognostic significance were extracted. Full article

Background/Objectives: Cardiac involvement in systemic sclerosis (SSc) ranges from subclinical to severe. While pulmonary artery hypertension (PAH) is well-documented, the mechanism of left ventricular (LV) ischemia remains unclear. Oxygen-sensitive cardiovascular magnetic resonance (OS-CMR) imaging offers a novel approach to assessing myocardial oxygenation and ischemia. This study evaluated the changes in myocardial deoxygenation in response to stress using LV OS-CMR in SSc patients without known cardiac disease. Methods: We prospectively recruited SSc patients without prior cardiac disease or risk factors, and age- and sex-matched healthy volunteers (HVs). All participants underwent transthoracic echocardiography (TTE) and 3T CMR, including native T1 mapping, rest/stress OS-CMR, stress perfusion, and late gadolinium enhancement (LGE). The primary outcome was a change in the LV OS-CMR signal intensity (SI) after adenosine stress. Results: Thirty-three participants (23 SSc, 10 HV) were enrolled. SSc patients had significantly lower global LV OS-CMR SI compared to HV (13.4 ± 6.5 vs. 19.5 ± 3.6, p = 0.011). OS-CMR SI change ≤ 10% was observed in at least one segment in 20 (87%) SSc patients and globally in 12 (52%). LGE was present in 5 (22%) patients, and 18 (78%) had ≥1 abnormal T1 mapping segment. LV global longitudinal strain (GLS) was reduced in SSc patients compared to the HVs (−19.04 ± 3.86 vs. −21.92 ± 3.72, p = 0.045). All HVs had normal CMR and TTE findings. Conclusions: SSc patients without known cardiovascular disease or PAH demonstrated subclinical LV ischemia with an impaired myocardial oxygenation response to stress. They further demonstrated LV myocardial deformation abnormalities and LV diffuse fibrosis when compared to an age-matched control group. Our findings support the presence of early coronary microvascular dysfunction and LV myocardial fibrosis in this population, which may explain the adverse cardiovascular risk seen in this population, independent of the presence of PAH. Full article

Anomalies of coronary artery origins are rare but significant conditions that can range from benign to life-threatening. Early detection through imaging is crucial in preventing adverse outcomes. The treatment strategy varies depending on the type and severity of the anomaly, ranging from pharmacological treatment to surgery. A 22-year-old male patient, after syncope, after excluding other causes, had an exercise drill test, which was clinically negative and ECG-positive. Angio-CT revealed an undeveloped left main coronary artery (LMCA), and the circulation was supplied through the right coronary artery (RCA). The RCA provides the left anterior descending artery (LAD), and the LAD retrogradely supplies the left circumflex artery (LCX). The myocardial perfusion scintigraphy showed a slight lack of perfusion in the anterior wall (6% of total perfusion). The patient was qualified for further observation. A 77-year-old female underwent cardiac CT due to stenocardia. CT showed a lack of LMCA. The initial segment of the RCA gave rise to the left coronary artery (LCA), which encircled the aortic bulb posteriorly and bifurcated into branches resembling the LCX and LAD. After the Heart Team consultation, the patient was deemed eligible for conservative treatment. Angio-CT is a valuable tool for detecting coronary artery anomalies. Full article

Myocardial viability assessment plays a critical role in the clinical management of patients with ischemic heart disease, particularly in guiding revascularization decisions. Various non-invasive imaging modalities have been developed and refined to evaluate viable myocardium, each offering unique insights into myocardial perfusion, metabolism, and contractile function. This review examines the comparative strengths and limitations of key imaging techniques. Understanding the pathophysiological basis and diagnostic capabilities of these modalities enables clinicians to tailor viability assessments to individual patient profiles, ultimately enhancing decision-making and optimizing outcomes in ischemic cardiomyopathy. Full article

Coronary microvascular obstruction and dysfunction (CMVO) frequently arise following primary percutaneous coronary intervention (PCI), particularly in individuals with myocardial infarction. Despite the restoration of epicardial blood flow, microvascular perfusion might still be compromised, resulting in negative clinical outcomes. CMVO is a complex condition resulting from a combination of ischemia, distal thrombotic embolization, reperfusion injury, and individual susceptibilities such as inflammation and endothelial dysfunction. The pathophysiological features of this condition include microvascular spasm, endothelial swelling, capillary plugging by leukocytes and platelets, and oxidative stress. Traditional angiographic assessments, such as Thrombolysis in Myocardial Infarction (TIMI) flow grade and myocardial blush grade, have limited sensitivity. Cardiac magnetic resonance imaging (CMR) stands as the gold standard for identifying CMVO, while the index of microvascular resistance (IMR) is a promising invasive option. Treatment approaches involve powerful antiplatelet drugs, anticoagulants, and supersaturated oxygen, yet no treatment has been definitively shown to reverse established CMVO. CMVO remains a significant therapeutic challenge in coronary artery disease management. Enhancing the comprehension of its core mechanisms is vital for the development of more effective and personalized treatment strategies. Full article