Interpretation of SPECT wall motion with deep learning.

OBJECTIVES: We sought to develop a novel deep learning (DL) workflow to interpret single-photon emission computed tomography (SPECT) wall motion. BACKGROUND: Wall motion assessment with SPECT is limited by image temporal and spatial resolution. Visual interpretation of wall motion can be subjective and prone to error. Artificial intelligence (AI) may improve accuracy of wall motion assessment. METHODS: A total of 1038 patients undergoing rest electrocardiogram (ECG)-gated SPECT and echocardiography were included. Using echocardiography as truth, a DL-model (DL-model 1) was trained to predict the probability of abnormal wall motion. Of the 1038 patients, 317 were used to train a DL-model (DL-model 2) to assess regional wall motion. A 10-fold cross-validation was adopted. Diagnostic performance of DL was compared with human readers and quantitative parameters. RESULTS: The area under the receiver operating characteristic curve (AUC) and accuracy (ACC) of DL model (AUC: .82 [95% CI: .79-.85]; ACC: .88) were higher than human (AUC: .77 [95% CI: .73-.81]; ACC: .82; P < .001) and quantitative parameter (AUC: .74 [95% CI: .66-.81]; ACC: .78; P < .05). The net reclassification index (NRI) was 7.7%. The AUC and accuracy of DL model for per-segment and per-vessel territory diagnosis were also higher than human reader. The DL model generated results within 30 seconds with operable guided user interface (GUI) and therefore could provide preliminary interpretation. CONCLUSIONS: DL can be used to improve interpretation of rest SPECT wall motion as compared with current human readers and quantitative parameter diagnosis.

Myocardial flow reserve recovery in patients with Takotsubo syndrome: Insights from positron emission tomography.

BACKGROUND: Coronary microvascular dysfunction (CMD) has been implicated in the pathogenesis of Takotsubo syndrome (TTS). Positron emission tomography (PET) plays a key role in the assessment of CMD through myocardial flow reserve (MFR). However, there is limited information on the temporal progression of MFR and its relationship to coronary artery disease (CAD) in TTS patients. METHODS: This study evaluated patients with TTS who underwent cardiac catheterization and PET within one year of hospitalization. Patients were categorized into acute (≤10 days), subacute (11-30 days), and chronic (≥31 days) stages based on post-onset time of PET assessment. MFR values and prevalence of abnormal MFR (<2.0) were compared between stages. Temporal MFR changes in patients with obstructive CAD (≥70% stenosis by coronary angiography), non-obstructive CAD, and normal coronaries were compared. RESULTS: Of the 88 patients studied (mean age 70; 96% female), 52 (59%) were in the acute, 17 (19%) in the subacute, and 19 (22%) in the chronic stage. Median MFR in the acute stage was 2.0 (1.5-2.3), with 58% of patients showing abnormal MFR. A significant time-dependent improvement in MFR was observed (P = 0.002), accompanied by a decreased prevalence of abnormal MFR (P = 0.016). While patients with normal coronaries showed significant MFR improvement over time (P = 0.045), patients with obstructive or non-obstructive CAD demonstrated no improvement across three stages (P = 0.346 and 0.174, respectively). CONCLUSION: PET-derived MFR was impaired in TTS patients during the acute phase, with improvement suggesting potential recovery from CMD over time. The concurrent presence of obstructive CAD might impede this recovery process.

Cardiac CT: Competition, complimentary or confounder.

Coronary CT angiography (CCTA) has been gradually adopted into clinical practice over the last two decades. CCTA has high diagnostic accuracy, prognostic value, and unique features such as assessment of plaque composition. CCTA-derived functional assessment techniques such as fractional flow reserve and CT perfusion are also available and can increase the diagnostic specificity of the modality. These properties propound CCTA as a competitor of functional testing in diagnosis of obstructive CAD, however, utilizing CCTA in a concomitant fashion to potentiate the performance of the latter can lead to better patient care and may provide more accurate prognostic information. Although multiple diagnostic challenges such as evaluation of calcified segments, stents, and small distal vessels still exist, the technologic developments in hardware as well as growing incorporation of artificial intelligence to daily practice are all set to augment the diagnostic and prognostic role of CCTA in cardiovascular disorders.

Myocardial blood flow quantification with SPECT.

INTRODUCTION: The addition of absolute myocardial blood flow (MBF) data improves the diagnostic and prognostic accuracy of relative perfusion imaging with nuclear medicine. Cardiac-specific gamma cameras allow measurement of MBF with SPECT. METHODS: This paper reviews the evidence supporting the use of SPECT to measure myocardial blood flow (MBF). Studies have evaluated SPECT MBF in large animal models and compared it in humans with invasive angiographic measurements and against the clinical standard of PET MBF. The repeatability of SPECT MBF has been determined in both single-site and multi-center trials. RESULTS: SPECT MBF has excellent correlation with microspheres in an animal model, with the number of stenoses and fractional flow reserve, and with PET-derived MBF. The inter-user coefficient of variability is ∼20% while the COV of test-retest MBF is ∼30%. SPECT MBF improves the sensitivity and specificity of the detection of multi-vessel disease over relative perfusion imaging and provides incremental value in predicting adverse cardiac events. CONCLUSION: SPECT MBF is a promising technique for providing clinically valuable information in the assessment of coronary artery disease.

Neural Networks Based on Synthesized Training Data for the Automated Detection of Chemical Plumes in Passive Infrared Multispectral Images.

Automated detection of volatile organic compounds in the atmosphere can be achieved by applying pattern recognition analysis to passive infrared (IR) multispectral remote sensing data. However, obtaining analyte-active training data through field experiments is time-consuming and expensive. To address this issue, methodology has been developed for simulating radiance profiles acquired using a multispectral IR line-scanner mounted in a downward-looking position on a fixed-wing aircraft. The simulation strategy used Planck's radiation law and a radiometric model along with the laboratory spectrum of the target compound to compute the upwelling IR background radiance with the presence of the analyte within the instrumental field-of-view. By combining the simulated analyte-active radiances and field-collected analyte-inactive radiances, a synthetic training dataset was constructed. A backpropagation neural network was employed to build classifiers with the synthetic training dataset. Employing methanol as the target compound, the performance of the classifiers was evaluated with field-collected data from airborne surveys at two test fields.

Competency based medical education in nuclear cardiology: A tale of two axes.

BACKGROUND: Across medical specialties, including nuclear cardiology, competency based medical education (CBME) changes the emphasis of learning from a time or experiential emphasis to a proficiency focused approached. Plotted on a learning-curve graph the emphasis on learning has shifted from the duration/ volume-based x-axis to the performance-based y-axis. CURRENT STATUS: It has proven difficult to establish y-axis-based standards within nuclear cardiology to assess learning. As such there is a paucity of data to verify current experiential training targets and only recently is data emerging that seeks to find CBME targets by which proficiency (y-axis units) can be evaluated. Initial reports from such CBME-oriented studies indicate that in current nuclear cardiology practice, the number of studies required to achieve competency is dependent upon the chosen measure of competency that is assessed (summed stress score versus % LV ischemia), the case mix, and the modality being learnt (PET versus SPECT). Recent findings have also suggested that prior levels of experiential training may be an underestimation of the number of supervised studies learners need to interpret before they achieve competency. SUMMARY: Nuclear cardiology training has adopted the concept of CBME and is progressing toward a more modern approach to trainee assessment. This brief review provides the background, current requirements and insights into new developments in nuclear cardiology training.

Identifying left ventricular dysfunction using prospective electrocardiogram-triggered coronary computed tomography angiography.

PURPOSE: Coronary computed tomography angiography (CCTA) is an important non-invasive tool for the assessment of coronary artery disease and the delivery of information incremental to coronary anatomy. CCTA measured left ventricular (LV) mid-diastolic volume (LVMDV) and LV mass (LVMass) have important prognostic information but the utility of prospectively ECG-triggered CCTA to predict reduced left ventricular ejection fraction (LVEF) is unknown. The objective of this study was to determine if indexed LVMDV (LVMDVi) and the LVMDV:LVMass ratio on CCTA can identify patients with reduced LVEF. MATERIALS/METHODS: 8179 patients with prospectively ECG-triggered CCTA between November 2014 and December 2019 were reviewed. A subset derivation cohort of 4352 healthy patients was used to define normal LVMDVi and LVMDV:LVMass. Sex-specific thresholds were tested in a validation cohort of 1783 patients, excluded from the derivation cohort, with cardiac disease and known LVEF. The operating characteristics for 1 SD above the mean were tested for the identification of abnormal LVEF, LVEF≤35 â€‹% and ≤30 â€‹%. RESULTS: The derivation cohort had a mean LVMDVi of 61.0 â€‹± â€‹13.7 â€‹mL/m2 and LVMDV:LVMass of 1.11 â€‹± â€‹0.24 â€‹mL/g. LVMDVi and LVMDV:LVMass were both higher in patients with reduced LVEF than those with normal LVEF (98.8 â€‹± â€‹40.8 â€‹mL/m2 vs. 63.3 â€‹± â€‹19.7 â€‹mL/m2, p â€‹< â€‹0.001, and 1.32 â€‹± â€‹0.44 â€‹mL/g vs. 1.05 â€‹± â€‹0.28 â€‹mL/g, p â€‹< â€‹0.001). Both mean LVMDVi and LVMDV:LVMass increased with the severity of LVEF reduction. Sex-specific LVMDVi thresholds were 79 â€‹% and 80 â€‹% specific for identifying abnormal LVEF in females (LVMDVi â€‹≥ â€‹69.9 â€‹mL/m2) and males (LVMDVi â€‹≥ â€‹78.8 â€‹mL/m2), respectively. LVMDV:LVMass thresholds had high specificity (87 â€‹%) in both females (LVMDVi:LVMass â€‹≥ â€‹1.39 â€‹mL/g) and males (LVMDVi:LVMass â€‹≥ â€‹1.30 â€‹mL/g). CONCLUSION: Our study provides reference thresholds for LVMDVi and LVMDV:LVMass on prospectively ECG-triggered CCTA, which may identify patients who require further LV function assessment.

Understanding barriers to and facilitators of clinician-patient conversations about brain health and cognitive concerns in primary care: a systematic review and practical considerations for the clinician.

BACKGROUND: Primary care clinicians (PCCs) are typically the first practitioners to detect cognitive impairment in their patients, including those with Alzheimer's disease or related dementias (ADRD). However, conversations around cognitive changes can be challenging for patients, family members, and clinicians to initiate, with all groups reporting barriers to open dialogue. With the expanding array of evidence-based interventions for ADRD, from multidomain care management to novel biotherapeutics for early-stage AD, incorporating conversations about brain health into routine healthcare should become a standard of care. We conducted a systematic review to identify barriers to and facilitators of brain health conversations in primary care settings. METHODS: We systematically searched PubMed, Scopus, Web of Science, and the Cochrane Library for qualitative or quantitative studies conducted in the US between January 2000 and October 2022 that evaluated perceptions of cognition and provider-patient brain health conversations prior to formal screening for, or diagnosis of, mild cognitive impairment or ADRD. We assessed the quality of the included studies using the Mixed Methods Appraisal Tool. RESULTS: In total, 5547 unique abstracts were screened and 22 articles describing 19 studies were included. The studies explored perceptions of cognition among laypersons or clinicians, or provider-patient interactions in the context of a patient's cognitive concerns. We identified 4 main themes: (1) PCCs are hesitant to discuss brain health and cognitive concerns; (2) patients are hesitant to raise cognitive concerns; (3) evidence to guide clinicians in developing treatment plans that address cognitive decline is often poorly communicated; and (4) social and cultural context influence perceptions of brain health and cognition, and therefore affect clinical engagement. CONCLUSIONS: Early conversations about brain health between PCCs and their patients are rare, and effective tools, processes, and strategies are needed to make these vital conversations routine.

Application of Cardiovascular Computed Tomography to the Assessment of Patients With Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy is a common inherited cardiac condition in which regional myocardial thickening and scarring can lead to a range of symptoms including breathlessness, dizziness, chest pain, and collapse with loss of consciousness. It is vital to be able to understand the mechanisms behind these epiphenomena and to be able to distinguish, for example, between syncope because of arrhythmia versus syncope because of mechanical outflow tract obstruction. Therefore, we require a technique that can characterize anatomy, physiology, and myocardial substrate. Traditionally, this role has been the preserve of cardiac magnetic resonance (CMR) imaging. This review makes the case for cardiac computed tomography (CT) as an alternative imaging method. We review the use of functional CT to identify the components of outflow tract obstruction (and obstruction at other levels, which may be simultaneous), and as an aid to interventional and surgical planning. We demonstrate the added value of multiplanar isotropic reformats in this condition, particularly in cases where the diagnosis may be more challenging or where complications (such as early apical aneurysm) may be difficult to recognize with 2-dimensional techniques. In conclusion, our aim is to convince readers that cardiac CT is a highly valuable and versatile tool, which deserves wider usage and greater recognition in those caring for patients with hypertrophic cardiomyopathy.

The estimation of left ventricular function using prospective ECG-triggered coronary CT angiography.

BACKGROUND: Coronary computed tomography angiography (CCTA) is vital for diagnosing coronary artery disease; however, prospective ECG-triggered acquisition, minimizing radiation exposure, limits left ventricular (LV) ejection fraction (EF) evaluation. We aimed to assess the feasibility and utility of LVEF100msec, a new index for estimating LV function using volumetric changes during 100 msec within systole. METHODS: This retrospective study analyzed patients who underwent prospective ECG-triggered CCTA with systolic acquisition between January 2015 and June 2022. The LVEF100msec was calculated using the maximum and minimum LV volumes among the three phases (300, 350, and 400 msec post-QRS) and expressed as a percentage. Patients were classified into normal, mild-moderately reduced, or severely reduced LV function categories based on the reference test. The LVEF100msec was compared among groups, and the optimal cutoff value of LVEF100msec for predicting severe LV dysfunction was investigated. RESULTS: The study included 271 patients (median age â€‹= â€‹58 years, 52% male). LVEF was normal in 188 (69.4%), mild-moderately reduced in 57 (21.0%), and severely reduced in 26 (9.6%) patients. Median LVEF100msec value was 9.0 (6.7-12.6) for normal LV function, 4.7 (3.1-8.8) for mild-moderately reduced, and 2.9 (1.5-3.8) for severely reduced LV function. LVEF100msec values significantly differed among categories (p â€‹< â€‹0.001). The optimal LVEF100msec cutoff for severe LV dysfunction was 4.3%, with an AUC of 0.924, sensitivity of 88%, and specificity of 89%. CONCLUSION: The LVEF100msec may serve as a valuable indicator of severe LV dysfunction.

Deep learning model to predict exercise stress test results: Optimizing the diagnostic test selection strategy and reduce wastage in suspected coronary artery disease patients.

BACKGROUND: Cardiac exercise stress testing (EST) offers a non-invasive way in the management of patients with suspected coronary artery disease (CAD). However, up to 30% EST results are either inconclusive or non-diagnostic, which results in significant resource wastage. Our aim was to build machine learning (ML) based models, using patients demographic (age, sex) and pre-test clinical information (reason for performing test, medications, blood pressure, heart rate, and resting electrocardiogram), capable of predicting EST results beforehand including those with inconclusive or non-diagnostic results. METHODS: A total of 30,710 patients (mean age 54.0 years, 69% male) were included in the study with 25% randomly sampled in the test set, and the remaining samples were split into a train and validation set with a ratio of 9:1. We constructed different ML models from pre-test variables and compared their discriminant power using the area under the receiver operating characteristic curve (AUC). RESULTS: A network of Oblivious Decision Trees provided the best discriminant power (AUC=0.83, sensitivity=69%, specificity=0.78%) for predicting inconclusive EST results. A total of 2010 inconclusive ESTs were correctly identified in the testing set. CONCLUSIONS: Our ML model, developed using demographic and pre-test clinical information, can accurately predict EST results and could be used to identify patients with inconclusive or non-diagnostic results beforehand. Our system could thus be used as a personalised decision support tool by clinicians for optimizing the diagnostic test selection strategy for CAD patients and to reduce healthcare expenditure by reducing nondiagnostic or inconclusive ESTs.

Prognostic Value of Coronary Computed Tomography Angiography in Coronary Artery Bypass Graft Patients Systematic Review and Meta-Analysis.

We sought to assess the prognostic value of coronary computed tomographic angiography (CCTA) in patients with coronary artery bypass graft (CABG) by meta-analysis. MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and Scopus were searched for relevant original articles published up to July 2021. CCTA prognostic studies enrolling patients with CABG were screened and included if outcomes included all-cause mortality or major adverse cardiac events. Maximally adjusted hazard ratios (HRs) were extracted for CCTA-derived prognostic factors. HRs were log-transformed and pooled across studies using the DerSimonian-Laird random-effects model and statistical heterogeneity was assessed using the I2 statistic. Of 1,576 screened articles, 4 retrospective studies fulfilled all inclusion criteria. Collectively, a total of 1,809 patients with CABG underwent CCTA (mean [SD] age 67.0 [8.5] years across 3 studies, 81.5% male across 4 studies). Coronary artery disease severity and revascularization were categorized using 2 models: unprotected coronary territories and coronary artery protection score. The pooled HRs from the random-effects models using the most highly adjusted study estimate were 3.64 (95% confidence interval 2.48 to 5.34, I2 = 57.8%, p <0.001; 4 studies) and 4.85 (95% confidence interval 3.17 to 7.43, I2 = 39.9%, p <0.001; 2 studies) for unprotected coronary territories and coronary artery protection score, respectively. In conclusion, in a limited number of studies, CCTA is an independent predictor of adverse events in patients with CABG. Larger studies using uniform models and endpoints are needed.

Utility of FFRCT in Patients with Chest Pain.

PURPOSE OF REVIEW: The goal of this article is to review the data supporting the use of fractional flow reserve derived from coronary computed tomography angiography (FFRCT) in patients with chest pain. REVIEW FINDINGS: Numerous clinical trials have demonstrated that the diagnostic accuracy of coronary computed tomography angiography (CCTA) can be improved with the use of FFRCT, primarily due to its superior specificity when compared to CCTA alone. This promising development may help reduce the need for invasive angiography in patients presenting with chest pain. Furthermore, some studies have indicated that incorporating FFRCT into decision-making is safe, with an FFRCT value of ≥ 0.8 being associated with favorable outcomes. While FFRCT has been shown to be feasible in patients with acute chest pain, further large-scale studies are warranted to confirm its utility. The emergence of FFRCT as a tool for the management of patients with chest pain is promising. However, potential limitations require the interpretation of FFRCT in conjunction with clinical context.

Advances in Single-Photon Emission Computed Tomography: Hardware, Software, and Myocardial Flow Reserve.

The clinical presentation of coronary artery disease (CAD) has changed during the last 20 years with less ischemia on stress testing and more nonobstructive CAD on coronary angiography. Single-photon emission computed tomography (SPECT) myocardial perfusion imaging should include the measurement of myocardial flow reserve and assessment of coronary calcium for the diagnosis of nonobstructive CAD and coronary microvascular disease. SPECT/CT systems provide reliable attenuation correction for better specificity and low-dose CT for coronary calcium evaluation. SPECT MFR measurement is accurate, well validated, and repeatable.