Imaging and Modeling of Myocardial Metabolism

Current imaging methods have focused on evaluation of myocardial anatomy and function. However, since myocardial metabolism and function are interrelated, metabolic myocardial imaging techniques, such as positron emission tomography, single photon emission tomography, and magnetic resonance spectroscopy present novel opportunities for probing myocardial pathology and developing new therapeutic approaches. Potential clinical applications of metabolic imaging include hypertensive and ischemic heart disease, heart failure, cardiac transplantation, as well as cardiomyopathies. Furthermore, response to therapeutic intervention can be monitored using metabolic imaging. Analysis of metabolic data in the past has been limited, focusing primarily on isolated metabolites. Models of myocardial metabolism, however, such as the oxygen transport and cellular energetics model and constraint-based metabolic network modeling, offer opportunities for evaluation interactions between greater numbers of metabolites in the heart. In this review, the roles of metabolic myocardial imaging and analysis of metabolic data using modeling methods for expanding our understanding of cardiac pathology are discussed

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Optimization of the uptake method for estimating renal clearance of 99mTc mercaptoacetyltriglycine

This is a non-final version of an article published in final form in Zhao, Chunlei ; Shuke, Noriyuki ; Okizaki, Atsutaka ; Yamamoto, Wakako ; Usui, Koki ; Kikuchi, Kenjiro ; Kaneko, Shigeo ; Yachiku, Sunao ; Sasajima, Tadahiro ; Aburano, Tamio, Optimization of the uptake method for estimating renal clearance of 99mTc mercaptoacetyltriglycine, Nuclear Medicine Communications 25(2), FEB 2004, pp. 159-166OBJECTIVE: To improve the estimation of 99mTc mercaptoacetyltriglycine clearance in the renal uptake method by optimizing the conditions of renal depth, background, threshold for renal boundary determination, and time interval for integrating renal counts. METHODS: Dynamic renal imaging was performed in 232 patients with dual energy window acquisition (main, 140 +/- 14keV; sub, 122.5 3.5keV). For drawing renal regions of interest (ROIs), cut-off methods with 50% and 70% of the highest renal pixel counts were used. For drawing the backgrounds, circumferential and lateral-inferior quadrant peri-renal ROIs were used. For setting the time interval, periods of 1-2, 1-2.5, 1.5-2.5, 1.5-3 and 2-3 min post-injection were used. For determining renal depth, three methods of a theoretical exponential function using scatter fraction, Tonnesen's formula, and linear combination of scatter fraction and Tonnesen's formula were used. The scatter fraction was calculated using the counts in renal ROIs in the two energy windows. Using every combination of these conditions, renal uptake was calculated. As a reference, one-sample clearance was calculated from a blood sample taken at 30 min post-injection following Bubeck's formula. According to the methods for estimating renal depth, three non-linear regression models were derived to convert renal uptake to clearance. Using one-sample clearance and integrated renal counts as dependent and independent variables, data were fitted to the models to determine the necessary constants. The correlations between the model estimated clearances and one-sample clearance were investigated. RESULTS: One-sample clearance ranged from 11 to 404 ml x min(-1) per 1.73 m2. More than half of the regression using renal depth determined by the scatter fraction alone failed to converge. Among the successfully converged regressions, all model estimated clearances showed significant correlations (P<0.01) with one-sample clearance. The best correlation was observed in the model using renal depth determined by the combination of scatter fraction and Tonnesen's formulas, renal ROIs by 50% cut-off, lateral-inferior background and time interval of 2-3 min (r=0.898, P<0.001). CONCLUSION: The renal uptake method for estimating the clearance of mercaptoacetyltriglycine can be improved by the processing conditions proposed here

Estimation of fractional liver uptake and blood retention of 99mTc-DTPA-galactosyl human serum albumin: an application of a simple graphical method to dynamic SPECT.

This is a non-final version of an article published in final form in Shuke, Noriyuki ; Aburano, Tamio ; Okizaki, Atsutaka ; Zhao, Chunlei ; Nakajima, Kenichi ; Yokoyama, Kunihiko ; Kinuya, Seigo ; Watanabe, Naoto ; Michigishi, Takatoshi ; Tonami, Norihisa, Estimation of fractional liver uptake and blood retention of 99mTc-DTPA-galactosyl human serum albumin: an application of a simple graphical method to dynamic SPECT, Nuclear Medicine Communications 24(5), MAY 2003, pp. 503-511 authorThe objective of this study was to investigate clinical utility of a graphical method for estimating liver uptake and blood retention of 99mTc-DTPA-galactosyl human serum albumin (99mTc-GSA; DTPA is diethylenetriaminepentaacetic acid) using dynamic single photon emission computed tomography (SPECT) data. When considering the kinetics of 99mTc-GSA, if it is assumed that (1) 99mTc-GSA distributes only between blood and liver, and (2) no metabolism of 99mTc-GSA occurs during the observation period, a plot of liver counts versus cardiac blood pool counts should, theoretically, be a straight line. From the slope and y intercept of a regression line, coefficients for converting count based liver and blood pool data to the per cent injected dose (%ID) can be calculated. The applicability of this method was tested on dynamic SPECT data from 30 patients with liver dysfunction. To validate this method, plasma concentrations (%ID/ml plasma) at 6, 15 and 30 min after the injection were estimated by this method and compared with the measured ones. To investigate the clinical significance of the per cent liver uptake, the value obtained by this method was compared with the results of conventional liver function tests, including serum albumin, the hepaplastin test, prothrombin time and indocyanine green clearance. In every data set, a plot of liver counts to cardiac blood pool counts was fitted well by a straight line (P<0.00001). Estimated plasma concentrations by this method showed good correlation with the measured ones at 6, 15 and 30 min after the injection (r = 0.748, 0.838, 0.875, respectively; P<0.0001). The liver uptake determined by this method showed good correlation with the results of conventional hepatic function tests (P<0.002). The graphical method could provide an accurate estimate of %ID of 99mTc-GSA in blood without the need for blood sampling. The liver uptake determined by this method could be a simple but useful quantitative indicator of hepatic function

Impaired cardiac sympathetic nerve function in patients with Kawasaki disease: comparison with myocardial perfusion

http://journals.lww.com/pedresearch/Fulltext/2005/05010/Impaired_Cardiac_Sympathetic_Nerve_Function_in.23.aspx | http://journals.lww.com/pedresearch/Fulltext/2005/05010/Impaired_Cardiac_Sympathetic_Nerve_Function_in.23.asp

Optimization of the uptake method for estimating renal clearance of 99mTc mercaptoacetyltriglycine

http://journals.lww.com/nuclearmedicinecomm/Abstract/2004/02000/Optimization_of_the_uptake_method_for_estimating.12.aspx | http://journals.lww.com/nuclearmedicinecomm/Abstract/2004/02000/Optimization_of_the_uptake_method_for_estimating.12.asp

Estimation of fractional liver uptake and blood retention of 99mTc-DTPA-galactosyl human serum albumin: an application of a simple graphical method to dynamic SPECT.

http://journals.lww.com/nuclearmedicinecomm/Pages/default.aspx | http://journals.lww.com/nuclearmedicinecomm/Pages/default.asp