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ObjectivesTo determine predictors of tissue that would benefit from improved blood flow in subjects with advanced heart disease.BackgroundAdvanced regeneration and percutaneous revascularization strategies including revascularization of chronic total occlusions (CTO) are being used to potentially restore myocardial function in the growing population of patients with advanced heart disease. Predictors of myocardial recovery in this population have not been established.MethodsCardiac tissue was collected from 27 subjects undergoing LVAD or cardiac transplantation who had nuclear perfusion imaging prior to procedure. Histologic analysis for fibrosis, vascular density and inflammation was performed and correlated with nuclear perfusion images from the same areas. In a subset of subjects, correlations of nuclear perfusion with TIMI flow by coronary arteriography was also performed.ResultsAreas of both normal and abnormal epicardial coronary blood flow had a large variation in radiotracer uptake. There were no statistically significant correlations between uptake of radiotracer at rest and degree of cardiac fibrosis, vascular density or inflammation and the matched area of myocardium. Fibrosis varied from 5-50% in areas with severe defects and areas of normal radiotracer uptake. Endothelial density correlated with inflammation in end-stage heart disease.ConclusionsRadiotracer uptake poorly predicted both areas of severe fibrosis that will not benefit from increased blood flow and areas of minimal fibrosis that may recover. Correlation of inflammation and endothelial density support a hypothesis that inflammatory cytokines augment vascularity in myocardium. Novel strategies to improve function in advanced heart disease are in need of better markers of recovery.

Background: The accuracy of absolute myocardial blood flow (MBF) from dynamic contrast-enhanced cardiac computed tomography acquisitions has not been fully characterized. We evaluate computed tomography (CT) compared with rubidium-82 positron emission tomography (PET) MBF estimates in a high-risk population. Methods: In a prospective trial, patients receiving clinically indicated rubidium-82 PET exams were recruited to receive a dynamic contrast-enhanced cardiac computed tomography exam. The CT protocol included a rest and stress dynamic portion each acquiring 12 to 18 cardiac-gated frames. The global MBF was estimated from the PET and CT exam. Results: Thirty-four patients referred for cardiac rest-stress PET were recruited. Of the 68 dynamic contrast-enhanced cardiac computed tomography scans, 5 were excluded because of injection errors or mismatched hemodynamics. The CT-derived global MBF was highly correlated with the PET MBF (r=0.92; P P Conclusions: In a high-risk clinical population, a clinically practical dynamic contrast-enhanced cardiac computed tomography provided unbiased MBF estimates within 20% of rubidium-82 PET. Although unbiased, the CT estimates contain substantial variance with an standard error of the estimate of 0.44 mL/min per gram. Myocardial flow reserve estimation was not as accurate as individual MBF estimates.

Background Cardiac PET can provide quantitative myocardial blood flow (MBF) estimates. The frequency and clinical significance of discordant ischemia information between quantitative and qualitative parameters is unclear. Methods This retrospective, cohort study analyzed 256 Rb-82 stress-rest PET/CT studies. Global MBF and myocardial flow reserve (MFR) were estimated in absolute units for quantitative results and sum-stress and difference scores were used for qualitative results. Four groups of patients were evaluated based on a specific definition of concordant and discordant quantitative and qualitative results. Results 31% of cases demonstrated discordance. Factors associated with microvascular disease were more common in the groups with abnormal quantitative results, regardless of the qualitative findings. Patients with concordant abnormal results had a significantly increased risk of myocardial infarction, heart failure, percutaneous intervention, and all-cause-mortality at 1 year compared to patients with concordant normal results. In patients with discordant results of abnormal quantitative and normal qualitative findings, there was a higher prevalence of heart failure than in controls (12.5% vs 0%, p = 0.01). Conclusions Discordance in qualitative and quantitative ischemia measures from PET is common, and further study is needed to clarify its prognostic implications. Moreover, quantitative estimation of MBF and MFR appears to add value to qualitative visual interpretation by supporting qualitative findings when results are concordant. Abnormal quantitative findings, regardless of concordance or discordance with qualitative findings, occurred in patients with risk factors associated with diffuse disease and with increased risk of heart failure admission.

BACKGROUND Using positron emission tomography (PET) imaging, we sought to determine whether normal age or exercise training cause changes in the cardiac sympathetic nervous system function in male or female healthy volunteers. METHODS Healthy sedentary participants underwent PET studies before and after 6 months of supervised exercise training. Presynaptic uptake by the norepinephrine transporter-1 function was measured using PET imaging of [(11)C]-meta-hydroxyephedrine, a norepinephrine analog, and expressed as a permeability-surface area product (PSnt in mL/min/mL). Postsynaptic function was measured as β-adrenergic receptor density (β'max in pmol/mL tissue) by imaging the β-receptor antagonist [(11)C]-CGP12177. Myocardial blood flow (MBF in mL/min/mL tissue) was measured by imaging [(15)O]-water. RESULTS At baseline, there was no age difference in β'max or MBF but PSnt declined with age (1.12±0.11 young vs 0.87±0.06 old, p = .036). Before training, women had significantly greater MBF (0.87±0.03 vs 0.69±0.03, p < .0001) and PSnt (1.14±0.08 vs 0.75±0.07, p < .001) than men. Training increased VO2 max by 13% (p < .0001), but there were no training effects on β'max, PSnt, or MBF. Greater MBF in females and a trend to increased PSnt post-training persisted. CONCLUSION With age, presynaptic uptake as measured by PSnt declines, but there were no differences in β'max. Endurance training significantly increased VO2 max but did not cause any changes in the measures of cardiac sympathetic nervous system function. These findings suggest that significant changes do not occur or that current PET imaging methods may be inadequate to measure small serial differences in a highly reproducible manner.

Background Prior studies have shown that late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) and fluorodeoxyglucose (FDG) positron emission tomography (PET) confer incremental risk assessment in patients with cardiac sarcoidosis (CS). However, the incremental prognostic value of the combined use of LGE and FDG compared to either test alone has not been investigated, and this is the aim of the present study. Methods Retrospective observational study of 56 symptomatic patients with high clinical suspicion for CS who underwent LGE-CMR and FDG-PET and were followed for the occurrence of death and/or malignant ventricular arrhythmias (VA). Results The combination of PET and CMR yielded the following groups: 1) LGE-negative/normal-PET (n=20), 2) LGE-positive/abnormal-FDG (n=20), and 3) LGE-positive/normal FDG (n=16). After a median follow-up of 2.6years (IQR 1.2–4.1), 16 patients had events (7 deaths, 10 VA). All, but 1, events occurred in patients with LGE. LGE-positive/abnormal-FDG (7 events, HR 10.1 [95% CI 1.2–84]; P =0.03) and LGE-positive/normal-FDG (8 events, HR 13.3 [1.7–107]; P =0.015) patients had comparable risk of events compared to the reference LGE-negative/normal-PET group. In adjusted Cox-regression analysis, presence of LGE (HR 18.1 [1.8–178]; P =0.013) was the only independent predictor of events. Conclusion CS patients with LGE alone or in association with FDG were at similar risk of future events, which suggests that outcomes may be driven by the presence of LGE (myocardial fibrosis) and not FDG (inflammation).

Resting heart rate (RHR) declines with exercise training. Possible mechanisms include: 1) increased parasympathetic tone, 2) decreased responsiveness to beta-adrenergic stimulation, 3) decreased intrinsic heart rate or 4) combination of these factors.To determine whether an increase in resting parasympathetic tone or decrease in response to beta-adrenergic stimulation contributes to the decrease in RHR with training.51 screened healthy subjects aged 18-32 (n=20, mean age 26, 11 female) or 65-80 (n=31, mean age 69, 16 female) were tested before and after 6months of supervised exercise training. Heart rate response to parasympathetic withdrawal was assessed using atropine and beta-adrenergic responsiveness during parasympathetic withdrawal using isoproterenol.Training increased VO2 max by 17% (28.7±7.7 to 33.6±9.20ml/kg/min, P0.001). RHR decreased from 62.8±6.6 to 57.6±7.2 beats per minute (P0.0001). The increase in heart rate in response to parasympathetic withdrawal was unchanged after training (+37.3±12.8 pre vs. +36.4±12.2 beats per min post, P=0.41). There was no change in the heart rate response to isoproterenol after parasympathetic blockade with training (+31.9±10.9 pre vs. +31.0±12.0 post beats per min, P=0.56). The findings were similar in all four subgroups.We did not find evidence that an increase in parasympathetic tone or a decrease in responsiveness to beta-adrenergic activity accounts for the reduction in resting heart rate with exercise training. We suggest that a decline in heart rate with training is most likely due to decrease in the intrinsic heart rate.

Background Estimation of myocardial blood flow (MBF) with cardiac PET is often performed with conventional compartmental models. In this study, we developed and evaluated a physiologically and anatomically realistic axially distributed model. Unlike compartmental models, this axially distributed approach models both the temporal and the spatial gradients in uptake and retention along the capillary.

The Seattle Heart Failure Model (SHFM) is a multivariable model that uses demographic and clinical markers to predict survival in patients with heart failure. Inappropriate activation of the sympathetic nervous system, which contributes to the progression of heart failure and increased mortality, can be assessed using iodine-123 meta-iodobenzylguanidine (MIBG) cardiac imaging. This study investigated the incremental value of MIBG cardiac imaging when added to the SHFM for prediction of all-cause mortality.Survival data from 961 NYHA II-III subjects in the ADMIRE-HFX trial were included in this analysis. The predictive value of the SHFM alone and in combination with MIBG heart-to-mediastinum ratio (H/M) was compared for all-cause mortality (101 deaths during a median follow-up of 2 years).The addition of H/M to the SHFM in a Cox model significantly improved risk prediction (P.0001), with a greater utility in higher risk SHFM patients. The observed 2-year mortality in the highest-risk SHFM subjects (rounded SHFM score of 1) was 24%, but varied from 46% with H/M1.2 to 0% with H/M1.8. Net reclassification improvement was 22.7% (P.001), with 14.9% of subjects who died reclassified into a higher risk category than suggested by SHFM score alone (P = .01) and 7.9% of subjects who survived reclassified into a lower risk category (P.0001). The 2-year integrated discrimination improvement (+4.14%, P.0001) and the 1-year area under the receiver-operator characteristic curve (+0.04, P = .026) both showed significant improvement for the combined model with H/M compared to the SHFM alone.The addition of MIBG imaging to the SHFM improves risk stratification, especially in higher risk patients. MIBG may have clinical utility in higher risk patients who are being considered for devices such as ICD, CRT-D, LVAD, and cardiac transplantation.

Rationale and Objectives Cardiac computed tomography (CCT) in the emergency department may be cost saving for suspected acute coronary syndrome (ACS), but economic outcome data are limited. The objective of this study was to compare the cost of CCT-based evaluation versus standard of care (SOC) using the results of a clinical trial. Materials and Methods We developed a decision analytic cost-minimization model to compare CCT-based and SOC evaluation costs to obtain a correct diagnosis. Model inputs, including Medicare-adjusted patient costs, were primarily obtained from a cohort study of 102 patients at low to intermediate risk for ACS who underwent an emergency department SOC clinical evaluation and a 64-channel CCT. SOC costs included stress testing in 77% of patients. Data from published literature completed the model inputs and expanded data ranges for sensitivity analyses. Results Modeled mean patient costs for CCT-based evaluation were $750 (24%) lower than the SOC ($2384 and $3134, respectively). Sensitivity analyses indicated that CCT was less expensive over a wide range of estimates and was only more expensive with a CCT specificity below 67% or if more than 44% of very low risk patients had CCT. Probabilistic sensitivity analysis suggested that CCT-based evaluation had a 98.9% probability of being less expensive compared to SOC. Conclusion Using a decision analytic model, CCT-based evaluation resulted in overall lower cost than the SOC for possible ACS patients over a wide range of cost and outcome assumptions, including computed tomography–related complications and downstream costs.

Objectives This study examined short-term cardiac catheterization rates and medication changes after cardiac imaging. Background Noninvasive cardiac imaging is widely used in coronary artery disease, but its effects on subsequent patient management are unclear. Methods We assessed the 90-day post-test rates of catheterization and medication changes in a prospective registry of 1,703 patients without a documented history of coronary artery disease and an intermediate to high likelihood of coronary artery disease undergoing cardiac single-photon emission computed tomography, positron emission tomography, or 64-slice coronary computed tomography angiography. Results Baseline medication use was relatively infrequent. At 90 days, 9.6% of patients underwent catheterization. The rates of catheterization and medication changes increased in proportion to test abnormality findings. Among patients with the most severe test result findings, 38% to 61% were not referred to catheterization, 20% to 30% were not receiving aspirin, 35% to 44% were not receiving a beta-blocker, and 20% to 25% were not receiving a lipid-lowering agent at 90 days after the index test. Risk-adjusted analyses revealed that compared with stress single-photon emission computed tomography or positron emission tomography, changes in aspirin and lipid-lowering agent use was greater after computed tomography angiography, as was the 90-day catheterization referral rate in the setting of normal/nonobstructive and mildly abnormal test results. Conclusions Overall, noninvasive testing had only a modest impact on clinical management of patients referred for clinical testing. Although post-imaging use of cardiac catheterization and medical therapy increased in proportion to the degree of abnormality findings, the frequency of catheterization and medication change suggests possible undertreatment of higher risk patients. Patients were more likely to undergo cardiac catheterization after computed tomography angiography than after single-photon emission computed tomography or positron emission tomography after normal/nonobstructive and mildly abnormal study findings. (Study of Perfusion and Anatomy9s Role in Coronary Artery [CAD] [SPARC]; NCT00321399)

Purpose: Explore the extent to which stress myocardial perfusion imaging (MPI) studies for coronary heart disease detection met published appropriate use criteria (AUC), and the association between AUC classification and image findings. Data sources: Retrospective, descriptive review of stress studies performed at the University of Washington Medical Center (UWMC n= 1377) and the Veterans Health Administration of Puget Sound (VA n= 1445) in the 31 months following AUC publication. Conclusions: At UWMC and VA, 69% and 89% of MPI studies, respectively, were classified as appropriate, 16% and 3% as inappropriate, and 15% and 8% as uncertain. All differences were significant, p < .001. At UWMC, 11% of appropriate studies and 10% of inappropriate or uncertain studies were abnormal (demonstrating myocardial ischemia or myocardial infarction), p= .93; these analyses were not performed on VA studies. Implications for practice: Most studies at both sites were classified as appropriate. At UWMC, the likelihood of a study classified as appropriate demonstrating an abnormality was not significantly different from a study classified as uncertain or inappropriate. AUC are imperfect tools but are increasingly created and referenced; as such, it is vital that practicing nurse practitioners are knowledgeable about their creation, application, and evaluation.

Multiple-gated blood pool angiography (MUGA) using 99mTc-UltraTag (Mallinckrodt Inc., Maryland Heights, MO) labeled RBCs was performed in a patient with B-cell lymphoma for evaluation of the left ventricular ejection fraction before starting chemotherapy. Quantitative measurements from MUGA demonstrated normal left ventricular ejection fraction. However, cine images revealed delayed contraction of the left ventricle compared with that of the right, and phase contrast images demonstrated offset of the ventricles' phases. Evaluation with ECG showed delayed depolarization of the left ventricle consistent with LBBB. Phase imaging abnormalities detected on MUGA may be overlooked. Specific patterns of phase abnormalities may direct the physicians' attention toward yet unrecognized diagnoses.

Screening for coronary artery disease is common practice in the evaluation of liver transplantation candidates. However, it is unclear whether coronary screening influences transplantation eligibility. We sought to determine the association between screening stress myocardial perfusion imaging (MPI) results and the eligibility for liver transplantation. Within a retrospective cohort of liver transplantation candidates referred for screening stress MPI at a single institution from April 1998 to February 2004, we obtained the baseline characteristics, stress MPI results, transplantation eligibility, and transplantation denial criteria by chart review. Of 294 patients (39%) denied transplantation, the denial criteria were multifactorial for 91 (31%) of the candidates. Compared to candidates with low-risk stress MPI results, the odds of being denied transplantation were the same for candidates with intermediate-risk MPI results (odds ratio 0.93, 95% confidence interval 0.45 to 1.82) or high-risk MPI results (odds ratio 1.42, 95% confidence interval 0.54 to 3.73). This lack of association persisted in our analysis with additional stratification of stress MPI results into negative, positive-low-risk, positive-intermediate-risk, and positive-high-risk. In conclusion, the screening stress MPI results were not associated with liver transplantation eligibility. The large number of competing factors considered before transplantation listing and the low proportion of positive stress MPI results suggests that targeting screening to patients deemed otherwise acceptable for transplantation might increase the influence of stress MPI findings on transplantation eligibility.

Purpose: In cardiac PET and PET/CT imaging, misaligned transmission and emission images are a common problem due to respiratory and cardiac motion. This misalignment leads to erroneous attenuation correction and can cause errors in perfusion mapping and quantification. This study develops and tests a method for automated alignment of attenuation and emission data. Methods: The CT-based attenuation map is iteratively transformed until the attenuation corrected emission data minimize an objective function based on the Radon consistency conditions. The alignment process is derived from previous work by Welch et al. [“Attenuation correction in PET using consistency information,” IEEE Trans. Nucl. Sci. 45, 3134–3141 (1998)] for stand-alone PET imaging. The process was evaluated with the simulated data and measured patient data from multiple cardiac ammonia PET/CT exams. The alignment procedure was applied to simulations of five different noise levels with three different initial attenuation maps. For the measured patient data, the alignment procedure was applied to eight attenuation-emission combinations with initially acceptable alignment and eight combinations with unacceptable alignment. The initially acceptable alignment studies were forced out of alignment a known amount and quantitatively evaluated for alignment and perfusion accuracy. The initially unacceptable studies were compared to the proposed aligned images in a blinded side-by-side review. Results: The proposed automatic alignment procedure reduced errors in the simulated data and iteratively approaches global minimum solutions with the patient data. In simulations, the alignment procedure reduced the root mean square error to less than 5 mm and reduces the axial translation error to less than 1 mm. In patient studies, the procedure reduced the translation error by >50% and resolved perfusion artifacts after a known misalignment for the eight initially acceptable patient combinations. The side-by-side review of the proposed aligned attenuation-emission maps and initially misaligned attenuation-emission maps revealed that reviewers preferred the proposed aligned maps in all cases, except one inconclusive case. Conclusions: The proposed alignment procedure offers an automatic method to reduce attenuation correction artifacts in cardiac PET/CT and provides a viable supplement to subjective manual realignment tools.

The current standard-of-care workup of low-risk patients with chest pain in an emergency department takes 12-36 hours and is expensive. We hypothesized that negative 64-MDCT coronary angiography early in the workup of such patients may enable a shorter length of stay and reduce charges.The standard-of-care evaluation consisted of serial cardiac enzyme tests, ECGs, and stress testing. After informed consent, we added cardiac CT early in the standard-of-care workup of 53 consecutive patients. Fifty patients had negative CT findings and were included in this series. The length of stay and charges were analyzed using actual patient data for all patients in the standard-of-care workup and for two earlier discharge scenarios based on negative cardiac CT results: First, CT plus serial enzyme tests and ECGs during an observation period followed by discharge if all were negative; and second, CT plus one set of enzyme tests and one ECG followed by discharge if all were negative. Comparisons were made using paired Student's t tests.For standard of care and the two CT-based earlier discharge analyses, the mean lengths of stay were 25.4, 14.3, and 5.0 hours; mean charges were $7,597, $6,153, and $4,251. Length of stay and charges were both significantly less (p0.001) for the two CT-based analyses.In low-risk patients with chest pain, discharge from the emergency department based on negative cardiac CT, enzyme tests, and ECG may significantly decrease both length of stay and hospital charges compared with the standard of care.

Background— Better insight into the psychosocial factors associated with prehospital delays in seeking care for acute coronary syndromes is needed to inform the design of future interventions. Delay in presenting for care after the onset of symptoms is common, limits the potential benefit of acute reperfusion, and has not been reduced by interventions tested thus far. Methods and Results— Seven hundred ninety-six patients with suspected ischemic heart disease scheduled for clinically indicated imaging stress tests completed questionnaires concerning psychological distress and attachment styles (worthiness to receive care, trustworthiness of others to provide care). The primary dependent variable for this study was response to a question from the rapid early action for coronary treatment trial concerning intention to “wait until very sure” before seeking care for a possible “heart attack.” Responses to this question were strongly associated with actual emergency department-reported and self-reported care delay in the rapid early action for coronary treatment trial. In multivariable ordinal regression models, a more negative view of the trustworthiness of others, greater physical limitations from angina, and no previous revascularization were independently associated with increased intention to wait to seek care for a myocardial infarction. Intention to wait was not associated with inducible ischemia or self-perceived risk of myocardial infarction. Conclusions— Intention to delay seeking care for acute coronary syndromes is associated with a patient’s view of the trustworthiness of others, previous experience with revascularization, and functional limitations, even after adjustment for objective and perceived acute coronary syndromes risk. These findings provide insight into novel factors contributing to longer delay times and may inform future interventions to reduce delay time.

Physicians often consider angina pectoris to be synonymous with myocardial ischemia. However, the relationship between angina and myocardial ischemia is highly variable and we have little insight into the sources of this variability. We investigated the relationship of inducible myocardial ischemia on SPECT stress perfusion imaging to angina reported with routine daily activities during the previous four weeks (N=788) and to angina reported during an exercise stress test (N=371) in individuals with confirmed or suspected coronary disease referred for clinical testing. We found that angina experienced during daily life is more strongly and consistently associated with psychological distress and the personal threat associated with angina than with inducible myocardial ischemia. In multivariable models, the presence of any angina during routine activities over the prior month was significantly associated with age, perceived risk of myocardial infarction, and anxiety when compared to those with no reported angina in the past month. Angina during daily life was not significantly associated with inducible myocardial ischemia on stress perfusion imaging in bivariate or multivariable models. In contrast, angina experienced during exercise stress testing was significantly related to image and ECG ischemia, though it was also significantly associated with anxiety. These results suggest that angina frequency over the previous four weeks is more strongly associated with personal threat and psychosocial distress than with inducible myocardial ischemia. These results lend support to angina treatment strategies that aim to reduce threat and distress as well as to reduce myocardial ischemia.

Individuals with systolic dysfunction congestive heart failure may have decreased neuronal density, decreased neuronal function (reuptake or retention of norepinephrine), or a combination of these, plus reduction in postsynaptic beta-receptor density. Cardiac neuronal distribution and function can be imaged with standard gamma cameras and PET using radiolabeled analogs of norepinephrine. Postsynaptic beta-adrenergic receptor distribution and density can be determined using PET. Multiple imaging studies of the presynaptic component have reported that those individuals with the lowest retention or fastest washout of the radiolabeled analogs have a much greater annual mortality than do those with greater retention or slower washout rate. The results of some studies have suggested that the image abnormalities are better predictors of death than are more common predictors of outcome such as ejection fraction, heart rate variability, and microvolt T-wave alternans. The variability between these studies makes it unclear which measure of presynaptic dysfunction is the most predictive. beta-Receptor imaging has not been evaluated as extensively as a prognostic tool as has presynaptic imaging. Preliminary data suggest that regional mismatch between beta-receptors and presynaptic norepinephrine transporter function may serve as a marker for adverse outcome.

In a registry analysis of 8,004 consecutive patients presenting for diagnostic catheterization at a single institution from 1990 to 2000, chronic total occlusion (CTO) was found in 52% of patients with significant (or = 70% diameter stenosis) coronary artery disease. Peripheral vascular disease was the strongest clinical predictor of the presence of a CTO. In a multivariate analysis, CTO was the strongest predictor against the selection of percutaneous coronary intervention (PCI) as a treatment strategy, indicating that efforts to improve the success rate of PCI in CTO may have a significant impact on management of coronary disease.

There are no evidence-based studies of the treatment of patients with eosinophilic gastroenteritis. Treatment decisions depend on experience gained from observations linking causative entities, principal clinical manifestations, and anticipated natural history of the disease. Because clinical symptoms and organ involvement probably vary with etiology, classification as to the likely cause (eg, food allergy or other dietary intolerance, idiosyncratic drug reaction, occult infection, idiopathic) determines the decisions made about dietary, pharmacologic, and surgical treatment. Elimination of foods and the use of elemental diets, corticosteroids, and mast cell inhibitors (eg, cromolyn sodium, ketotifen), alone or in combination, all have their place, depending on the age of the patient, organ involved, clinical presentation, and clinical urgency. Isolated cases are diagnosed only at surgical exploration for acute abdominal catastrophes; in these instances, further therapy depends on whether resection is done, but most patients remain in remission after surgery. Occult parasitism remains an elusive and unrecognized cause of an unknown number of cases, suggesting that empiric antihelminthic therapy should be tried in some patients. Individual reports of success with nonsystemic steroids and leukotriene inhibitors have been published.

Although hypertrophic cardiomyopathy (HCM) is classically considered a disease of the left ventricle, right ventricular (RV) abnormalities have also been reported. However, involvement of the right ventricle in HCM has not been extensively characterized. The literature regarding prevalence, genetics, patterns of involvement, histologic findings, symptoms, diagnosis, and treatment of RV abnormalities in HCM is reviewed. To highlight the salient points, a case is presented of apical HCM with significant RV involvement, with an RV outflow tract gradient and near obliteration of the RV cavity, in the absence of a left intraventricular gradient. Right ventricular involvement in HCM appears to be as heterogeneous as that of the left ventricle. The spectrum extends from mild concentric hypertrophy to more unusual severe, obstructive disease. While in some cases the extent of RV involvement correlates with left ventricular (LV) involvement, predominant RV disease can be seen as well. While the genetics of RV involvement have not been well characterized, histologic findings appear to be similar to those in the left ventricle, suggesting similar pathogenesis. Significant RV involvement may result in RV outflow obstruction and/or reduced RV diastolic filling, with potentially increased incidence of severe dyspnea, supraventricular arrhythmias, and pulmonary thromboembolism. The optimal treatment for patients with significant RV disease is unknown. Medical and surgical therapies have been attempted with variable success; experience with newer techniques such as percutaneous catheter ablation has not been reported. Further characterization of RV involvement in HCM is necessary to elucidate more clearly the clinical features and optimal treatments of this manifestation of HCM.

A method is developed and described for analysis of [ 11 C]- meta -hydroxyephedrine, [ 11 C]MHED, a tracer of cardiac function, and its metabolites in plasma samples. The method combines on-column solid-phase extraction and separation on a single weak cation-exchange column. Phenylethanolamines were used to develop the separation method that concentrates the analytes on-column from physiological saline and then elutes them by changing to an acidic mobile phase. Hydrophobic interactions determine the selectivity, and elution order is the same as for reversed-phase liquid chromatography on a C 18 stationary phase. The mechanism of separation is mixed mode, with ion-exchange coupled with a reversed-phase liquid chromatography mechanism. Each sample analysis requires only 10 min and does not require deproteinization or the use of organic solvents. In human samples, a single plasma metabolite of [ 11 C]MHED along with the parent compound were observed using this method. The method was sufficiently rapid so that in 70 min seven samples were assayed, providing a well-defined time course for MHED and its metabolites in blood. The metabolite concentration increased with time to ≈85% of the plasma activity 50 min after administration. The results with the developed method are comparable to those described for reversed-phase separations, with the advantage that our method does not require deproteinization, reducing sample analysis time by a factor of two.

Coronary CT angiography has high sensitivity, but modest specificity, to detect acute coronary syndrome. We studied whether adding resting CT myocardial perfusion imaging improved the detection of acute coronary syndrome.Patients with low-to-intermediate cardiac risk presenting with possible acute coronary syndrome received both the standard of care evaluation and a research thoracic 64-MDCT examination. Patients with an obstructive (50%) stenosis or a nonevaluable coronary segment on CT were diagnosed with possible acute coronary syndrome. CT perfusion was determined by applying gray and color Hounsfield unit maps to resting CT angiography images. Adjudicated patient diagnoses were based on the standard of care and 3-month follow-up. Patient-level diagnostic performance for acute coronary syndrome was calculated for coronary CT, CT perfusion, and combined techniques.A total of 105 patients were enrolled. Of the nine (9%) patients with acute coronary syndrome, all had obstructive CT stenoses but only three had abnormal CT perfusion. CT perfusion was normal in all other patients. To detect acute coronary syndrome, CT angiography had 100% sensitivity, 89% specificity, and a positive predictive value of 45%. For CT perfusion, specificity and positive predictive value were each 100%, and sensitivity was 33%. Combined cardiac CT and CT perfusion had similar specificity but a higher positive predictive value (100%) than did CT angiography.Resting CT perfusion using CT angiographic images may have high specificity and may improve CT positive predictive value for acute coronary syndrome without added radiation and contrast. However, normal resting CT perfusion cannot exclude acute coronary syndrome.

Purpose The purpose of this study was to assess the diagnostic accuracy and one year prognosis of whole chest, “multiple rule out” CT for coronary artery disease (CAD) in Emergency Department patients. Methods and Findings One hundred and two Emergency Department patients at low to intermediate risk of acute coronary syndrome (ACS), pulmonary embolism and/or acute aortic syndrome underwent a research 64 channel ECG-gated, whole chest CT and a standard of care evaluation. Patients were classified with obstructive CAD with either a coronary CT stenosis greater than 50% or a non-evaluable coronary segment. SOC and 3 month follow up data were used to determine an adjudicated clinical diagnosis. The diagnostic ability of obstructive CAD on CT to identify clinical diagnoses was determined. Patients were followed up for 1 year for cardiac events. Seven (7%) patients were diagnosed with ACS. CT sensitivity to detect obstructive CAD in ACS patients was 100% (95% CI 65%, 100%), negative predictive value 100% (96%, 100%), specificity 88% (80%, 94%), and positive predictive value 39% (17%, 64%). Pulmonary embolism and acute aortic syndrome were not identified in any patients. No cardiac events occurred in patients without obstructive CAD over 1 year. Conclusions Whole chest CT has high sensitivity and negative predictive value for ACS with excellent one year prognosis in patients without obstructive CAD on CT. The frequency of pulmonary embolism or acute aortic syndrome and the higher radiation dose suggest whole chest CT should be limited to select patients. ClinicalTrials.org #: NCT00855231

Explore the extent to which stress myocardial perfusion imaging (MPI) studies for coronary heart disease detection met published appropriate use criteria (AUC), and the association between AUC classification and image findings.Retrospective, descriptive review of stress studies performed at the University of Washington Medical Center (UWMC n= 1377) and the Veterans Health Administration of Puget Sound (VA n= 1445) in the 31 months following AUC publication.At UWMC and VA, 69% and 89% of MPI studies, respectively, were classified as appropriate, 16% and 3% as inappropriate, and 15% and 8% as uncertain. All differences were significant, p.001. At UWMC, 11% of appropriate studies and 10% of inappropriate or uncertain studies were abnormal (demonstrating myocardial ischemia or myocardial infarction), p= .93; these analyses were not performed on VA studies.Most studies at both sites were classified as appropriate. At UWMC, the likelihood of a study classified as appropriate demonstrating an abnormality was not significantly different from a study classified as uncertain or inappropriate. AUC are imperfect tools but are increasingly created and referenced; as such, it is vital that practicing nurse practitioners are knowledgeable about their creation, application, and evaluation.

Estimation of myocardial blood flow (MBF) with cardiac PET is often performed with conventional compartmental models. In this study, we developed and evaluated a physiologically and anatomically realistic axially distributed model. Unlike compartmental models, this axially distributed approach models both the temporal and the spatial gradients in uptake and retention along the capillary.We validated PET-derived flow estimates with microsphere studies in 19 (9 rest, 10 stress) studies in five dogs. The radiotracer, (13)N-ammonia, was injected intravenously while microspheres were administered into the left atrium. A regional reduction in hyperemic flow was forced by an external occluder in five of the stress studies. The flow estimates from the axially distributed model were compared with estimates from conventional compartmental models.The mean difference between microspheres and the axially distributed blood flow estimates in each of the 17 segments was 0.03 mL/g/minute (95% CI [-0.05, 0.11]). The blood flow estimates were highly correlated with each regional microsphere value for the axially distributed model (y = 0.98x + 0.06 mL/g/minute; r = 0.74; P.001), for the two-compartment (y = 0.64x + 0.34; r = 0.74; P.001), and for three-compartment model (y = 0.69x + 0.54; r = 0.74; P.001). The variance of the error of the estimates is higher with the axially distributed model than the compartmental models (1.7 [1.3, 2.1] times higher).The proposed axially distributed model provided accurate regional estimates of MBF. The axially distributed model estimated blood flow with more accuracy, but less precision, than the evaluated compartmental models.

Analyses of data on the transcapillary exchange and cellular uptake in the normal heart have generally been based on the assumption that local membrane conductances and volumes of distribution are everywhere the same. The question is whether such an assumption is justified in view of the marked (sixfold) heterogeneity of local blood flows per gram tissue. The method was to estimate both flow and capillary membrane permeability-surface area products (PS) locally in the heart. For each of five dogs running on a sloped treadmill, the deposition of tracer microspheres and of [131I]iodophenylpentadecanoic acid (IPPA), after left atrial injection, was determined in 256 pieces of left ventricular myocardium by killing the animals at approximately 100 s after radiotracer injection. A hydraulic occluder stopped the flow to a portion of the myocardium supplied by the left circumflex coronary artery 30 s before tracer injection. Regional flows ranged from 0.1 to 7.0 ml.g-1.min-1. IPPA extractions ranged from 20 to 49%. Using the known flows, we assumed the applicability of an axially distributed blood-tissue exchange model to estimate the PS for the capillary (PSc) and the parenchymal cell. It was impossible to explain the data if the PSc values for membrane transport were uniform throughout the organ. Rather, the only reasonable descriptors of the data required that local PSc values increase with local flow, almost in proportion. Current methods of analysis using data based on deposition methods need to be revised to take into account the near proportionality of PS to flow for at least some substrates.

I. INTRODUCTION No form of "alternative" or renewable energy has received more attention than photovoltaics. Literally billions of dollars have been spent researching materials and processes that directly convert sunlight to electricity. The first "solar cell" was made in the Bell Laboratories in the early days of the semiconductor revolution--about the same time as the first transistor. Clearly, the transistor already has revolutionized modern life. Yet people still talk about the future "photovoltaic revolution." Early commercial applications of photovoltaics still are operating some 25 years after installation, and hundreds of thousands of installations have been made. However, the sun's major promise as an energy source is yet to be felt. Nevertheless, public policy interest, government funding, and, most importantly, private risk capital continue pouring into this promising technology. The rationale for public support has its roots in the oil crisis of the early 1970s. Since that time, the motivation for public support, which began as a fear of imminent shortage of fossil fuels, has been broadened to include affordable rural electrification in the third world, environmental protection, and industrial policy for high technology exports. This money and effort have created a relatively small but worldwide business poised on the brink of a commercial breakthrough. This paper explores the current state of the market and technology for photovoltaics and draws inferences for those who are attempting to push the industry over the brink into greatness. II. PHOTOVOLTAIC OVERVIEW Energy reaching the Earth's surface from the sun is measured in units of kilowatt hours per day per square meter (kwh/d/|m.sup.2^). The average amount of sunlight at any location depends on latitude, cloud cover, and atmospheric conditions such as humidity. The distribution of this energy is more uniform than commonly believed. The Olympic rain forest in Washington receives about 3 kwh/d/|m.sup.2^ while southern Arizona, New Mexico, and parts of Utah receive about 7 kwh/d/|m.sup.2^. A more common way to express this measurement is to give the equivalent hours per day of "full sunlight." "Full sunlight" is defined as 1,000 watts per square meter of global radiation. Therefore, Arizona at 7 kwh/square meter gets seven hours of full sun while the Olympic rain forest at 3 kwh/square meter gets three hours of full sun. Reasonable historical insolation data are available for almost any location on Earth. Most photovoltaic companies predict their products' output using computer models that include these insolation data. The rule of thumb for predicting an unknown site is plus or minus 10 percent on an annual average based only on latitude and closest weather data. Well studied sites can be predicted within about 3 percent of annual output. Photovoltaic installations do not have much economy of scale. The cost per kilowatt drops very little above a site size of about 25 kw. Construction costs are related to the rate of installation, not the size of each segment. A construction site resembles a "factory in the field." Construction can be very quick. The ARCO Solar Carrisa Plains 6.5 MW site was built in five months, and techniques used on that site could reach 25 MW per month. Additionally, power can be turned on in increments as each segment of about 1 MW is completed. Therefore, there is almost no interest during construction and no start up period for a purchaser. Even large sites are unmanned, and there are no consumables. Published estimates of 0.8 cents per kwh grossly overestimate operation and maintenance costs. These estimates invariably come from small demonstration sites where maintenance of the data acquisition system and plant tours comprise the bulk of technician time. In summary, the resource is free and ubiquitous. Plant siting is easy, construction is quick, and performance is reliable and predictable. …

Cardiac computed tomography (CCT) in the emergency department may be cost saving for suspected acute coronary syndrome (ACS), but economic outcome data are limited. The objective of this study was to compare the cost of CCT-based evaluation versus standard of care (SOC) using the results of a clinical trial.We developed a decision analytic cost-minimization model to compare CCT-based and SOC evaluation costs to obtain a correct diagnosis. Model inputs, including Medicare-adjusted patient costs, were primarily obtained from a cohort study of 102 patients at low to intermediate risk for ACS who underwent an emergency department SOC clinical evaluation and a 64-channel CCT. SOC costs included stress testing in 77% of patients. Data from published literature completed the model inputs and expanded data ranges for sensitivity analyses.Modeled mean patient costs for CCT-based evaluation were $750 (24%) lower than the SOC ($2384 and $3134, respectively). Sensitivity analyses indicated that CCT was less expensive over a wide range of estimates and was only more expensive with a CCT specificity below 67% or if more than 44% of very low risk patients had CCT. Probabilistic sensitivity analysis suggested that CCT-based evaluation had a 98.9% probability of being less expensive compared to SOC.Using a decision analytic model, CCT-based evaluation resulted in overall lower cost than the SOC for possible ACS patients over a wide range of cost and outcome assumptions, including computed tomography-related complications and downstream costs.

Dynamic contrast enhanced CT has been successfully applied in cardiac imaging for the estimation of myocardial blood flow (MBF). In general, these acquisitions impart a relatively high radiation dose because they require continuous or gated imaging of the heart for 15-40 seconds. At present, there is no consensus on the appropriate estimation method to derive MBF and on the appropriate acquisition technique to minimize dose while maintaining MBF estimation accuracy and precision. This work explores the tradeoff of accuracy and precision of MBF estimates with several estimation methods and acquisition techniques in support of the fundamental goal of optimizing dynamic cardiac CT in terms of radiation dose and MBF estimation fidelity. We simulated time attenuation curves (TACs) for a range of flow states (Flow = [0.8, 1.6, 2.4, 3.2] ml/g/min) and several acquisition techniques. We estimated MBF with 5 different methods for each simulated TAC. From multiple independent realizations, we assessed the accuracy and precision of each method. Results show that acquisition techniques with 1/3 tube current or 1/3 temporal sampling permits accurate MBF estimates with most methods with reduction in MBF estimate precision by on average 30%. Furthermore, reduction in model complexity can be beneficial for improving the precision of MBF estimates.

Background— Patients with diabetes mellitus have accelerated progression of heart failure and often have impaired cardiac sympathetic innervation. The present study examines the implications for heart failure progression of cardiac sympathetic denervation, assessed by I-123 metaiodobenzylguanidine imaging, in diabetic compared with nondiabetic subjects. Methods and Results— We evaluated 343 diabetic and 618 nondiabetic subjects with New York Heart Association class II or III heart failure and a left ventricular ejection fraction ≤35% over a median follow-up of 17 months. A multivariable Cox proportional hazards model was used to examine the influence of clinical variables, b-type natriuretic peptide, plasma norepinephrine, left ventricular ejection fraction, and I-123 metaiodobenzylguanidine imaging parameters on time to a heart failure event. The late heart-to-mediastinum (H/M) ratio and the interaction term of diabetes mellitus with the prospectively selected late H/M ratio Conclusions— The combination of diabetes mellitus and I-123 metaiodobenzylguanidine H/M ratio is an independent predictor of heart failure progression, confirming the high risk of diabetic subjects with impaired cardiac sympathetic nerve function. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00126438 and NCT00126425.

A retrospective review was performed of 13 patients with the diagnosis of idiopathic eosinophilic esophagitis (IEE) occurring alone or in conjunction with idiopathic eosinophilic gastroenteritis (IEG) to identify clinical, radiographic, endoscopic, manometric, and therapeutic similarities. All patients presented with esophageal symptoms, predominantly dysphagia. An allergic disorder was present in 10 (77%) patients, and peripheral eosinophilia was present in 12 (92%) patients. Clinical investigation disclosed esophageal strictures in 10 patients, motility disorders in three, ulcerations in two, a cervical web in one, and a mucosal ring in one as the cause of esophageal symptoms. A proximal esophageal stricture was the single most common esophageal abnormality demonstrated. IEE should be included in the differential diagnosis of dysphagia and should be suggested in a patient with an allergic disorder, peripheral eosinophilia, and concurrent abdominal symptoms, especially in conjunction with IEG. Prompt diagnosis is extremely important since treatment with steroids produces rapid clinical remission in most patients.

The purpose of this article is to determine the frequency of adverse cardiac events during the year following a negative cardiac CT angiogram in a population of patients presenting to the emergency department with low-to-moderate risk chest pain.Eighty-one consecutive patients who had standard of care evaluation for low-to-moderate risk chest pain in the emergency department were enrolled and consented to have a cardiac CT angiogram added to their workup and to have follow-up for 1 year. Eleven patients were excluded, six because their cardiac CT examinations were unsuccessful, four because of a positive cardiac CT angiogram result, and one was lost to follow-up. Seventy patients with negative cardiac CT angiographic results (50% stenosis) were included and were interviewed in detail at 3, 6, and 12 months about intervening cardiac events, diagnostic testing, and therapy. Electronic medical records were also reviewed at each time point.None of the 70 patients reported an adverse cardiac event over the 12-month follow-up period. At 1 year, the cause of chest pain was unknown in 49 patients, gastrointestinal in nine patients, anxiety in seven patients, musculoskeletal in three patients, and other in two patients. Three of four patients with 50% or greater stenosis on their cardiac CT had subsequent cardiac catheterization and stent placement.In patients with low-to-moderate risk chest pain evaluated in the emergency department, adverse cardiac events may be rare during the 12 months following a negative cardiac CT angiogram.

In cardiac PET and PET/CT imaging, misaligned transmission and emission images are a common problem due to respiratory and cardiac motion. This misalignment leads to erroneous attenuation correction and can cause errors in perfusion mapping and quantification. This study develops and tests a method for automated alignment of attenuation and emission data.The CT-based attenuation map is iteratively transformed until the attenuation corrected emission data minimize an objective function based on the Radon consistency conditions. The alignment process is derived from previous work by Welch et al. ["Attenuation correction in PET using consistency information," IEEE Trans. Nucl. Sci. 45, 3134-3141 (1998)] for stand-alone PET imaging. The process was evaluated with the simulated data and measured patient data from multiple cardiac ammonia PET/CT exams. The alignment procedure was applied to simulations of five different noise levels with three different initial attenuation maps. For the measured patient data, the alignment procedure was applied to eight attenuation-emission combinations with initially acceptable alignment and eight combinations with unacceptable alignment. The initially acceptable alignment studies were forced out of alignment a known amount and quantitatively evaluated for alignment and perfusion accuracy. The initially unacceptable studies were compared to the proposed aligned images in a blinded side-by-side review.The proposed automatic alignment procedure reduced errors in the simulated data and iteratively approaches global minimum solutions with the patient data. In simulations, the alignment procedure reduced the root mean square error to less than 5 mm and reduces the axial translation error to less than 1 mm. In patient studies, the procedure reduced the translation error by50% and resolved perfusion artifacts after a known misalignment for the eight initially acceptable patient combinations. The side-by-side review of the proposed aligned attenuation-emission maps and initially misaligned attenuation-emission maps revealed that reviewers preferred the proposed aligned maps in all cases, except one inconclusive case.The proposed alignment procedure offers an automatic method to reduce attenuation correction artifacts in cardiac PET/CT and provides a viable supplement to subjective manual realignment tools.

Large-scale models accounting for the processes supporting metabolism and function in an organ or tissue with a marked heterogeneity of flows and metabolic rates are computationally complex and tedious to compute. Their use in the analysis of data from positron emission tomography (PET) and magnetic resonance imaging (MRI) requires model reduction since the data are composed of concentration–time curves from hundreds of regions of interest (ROI) within the organ. Within each ROI, one must account for blood flow, intracapillary gradients in concentrations, transmembrane transport, and intracellular reactions. Using modular design, we configured a whole organ model, GENTEX, to allow adaptive usage for multiple reacting molecular species while omitting computation of unused components. The temporal and spatial resolution and the number of species are adaptable and the numerical accuracy and computational speed is adjustable during optimization runs, which increases accuracy and spatial resolution as convergence approaches. An application to the interpretation of PET image sequences after intravenous injection of 13NH3 provides functional image maps of regional myocardial blood flows.

Background— Although angina is often caused by atherosclerotic obstruction of the coronary arteries, patients with similar amounts of myocardial ischemia may vary widely in their symptoms. We sought to compare clinical and psychosocial characteristics associated with more frequent angina after adjusting for the amount of inducible ischemia. Methods and Results— From 2004 to 2006, 788 consecutive patients undergoing single-photon emission computed tomography stress perfusion imaging at 2 Seattle hospitals were assessed for their frequency of angina over the previous 4 weeks with the Seattle Angina Questionnaire and for a broad range of psychosocial characteristics. Among patients with demonstrable ischemia on single-photon emission computed tomography (summed difference score ≥2; n=191), angina frequency was categorized as none (Seattle Angina Questionnaire score=100; n=68), monthly (score=61 to 99; n=66), and weekly or daily (score=0 to 60; n=57). Using multivariable ordinal logistic regression, increasing angina was significantly associated with a history of coronary revascularization (odds ratio 2.24, 95% confidence interval 1.19 to 4.19), anxiety (odds ratio 4.72, 95% confidence interval 1.91 to 11.66), and depression (odds ratio 3.12, 95% confidence interval 1.45 to 6.69) after adjustment for the amount of inducible ischemia. Conclusions— Among patients with a similar burden of inducible ischemia, a history of coronary revascularization and current anxiety and depressive symptoms were associated with more frequent angina. These results support the study of angina treatment strategies that aim to reduce psychosocial distress in conjunction with efforts to lessen myocardial ischemia.

The purpose of this study was to compare the patient radiation dose and coronary artery image quality of long-z-axis whole-chest 64-MDCT performed with retrospective ECG gating with those of CT performed with prospective ECG triggering in the evaluation of emergency department patients with nonspecific chest pain.Consecutively registered emergency department patients with nonspecific low-to-moderate-risk chest pain underwent whole-chest CT with retrospective gating (n = 41) or prospective triggering (n = 31). Effective patient radiation doses were estimated and compared by use of unpaired Student's t tests. Two reviewers independently scored the quality of images of the coronary arteries, and the scores were compared by use of ordinal logistic regression.Age, heart rate, body mass index, and z-axis coverage were not statistically different between the two groups. For retrospective gating, the mean effective radiation dose was 31.8 +/- 5.1 mSv; for prospective triggering, the mean effective radiation dose was 9.2 +/- 2.2 mSv (prospective triggering 71% lower, p0.001). Two of 512 segments imaged with retrospective gating were nonevaluable (0.4%), and two of 394 segments imaged with prospective triggering were nonevaluable (0.5%). Prospectively triggered images were 2.2 (95% CI, 1.1-4.5) times as likely as retrospectively gated images to receive a high image quality score for each segment after adjustment for segment differences (p0.05).For long-z-axis whole-chest 64-MDCT of emergency department patients with nonspecific chest pain, use of prospective ECG triggering may result in substantially lower patient radiation doses and better coronary artery image quality than is achieved with retrospective ECG gating.

Congestive heart failure increasingly contributes to the overall morbidity and mortality associated with cardiovascular disease. Although significant advances in therapies allow patients to feel better and have improved functional status and survival, not all patients respond equally to these therapies. Moreover, for any given level of left ventricular systolic dysfunction, it is difficult to predict who will have progressive heart failure leading to death or transplantation or who will die suddenly. It has long been recognized that the sympathetic nervous system plays a major role in the morbidity and mortality associated with congestive heart failure from systolic left ventricular dysfunction. Although some of the sympathetic effect occurs at the systemic level, malfunction at the ventricular myocyte-sympathetic nerve terminal interface is likely a major contributor to sudden death and progressive heart failure. Imaging the cardiac sympathetic nervous system can be used to evaluate this myoneural interface and to predict outcome.

To compare image quality and patient radiation dose in a group of patients who underwent 64-detector computed tomography (CT) coronary angiography performed with prospective electrocardiographic (ECG) gating with image quality and radiation dose in a group of patients matched for clinical features who underwent 64-detector CT coronary angiography performed with retrospective ECG gating.Institutional review board approval was obtained for this HIPAA-compliant study, and the informed consent requirement was waived due to the retrospective study design. Two independent reviewers separately scored coronary artery segment image quality and overall image quality for 100 cardiac CT studies (50 in each group). Interobserver variability was calculated. Patient radiation dose for the actual examination z-axis length was recorded, and a normalized dose was calculated for a 12-cm z-axis length of a typical heart.The two groups matched well for clinical characteristics and CT parameters. There was good agreement for coronary artery segment image quality scores between the independent reviewers (kappa = 0.72). Of the 1253 coronary artery segments scored, the number of coronary artery segments that could not be evaluated in each group was similar (1.1% [seven of 614] in the prospective group vs 1.5% [10 of 647] in the retrospective group, P = .53). Image quality scores were not significantly different when matched for chest cross-sectional area (P.05). Mean patient radiation dose was 77% lower for prospective gating (4.2 mSv) than for retrospective gating (18.1 mSv) (P.01).Use of 64-detector CT coronary angiography performed with prospective ECG gating has similar subjective image quality scores but 77% lower patient radiation dose when compared with use of retrospective ECG gating.

Pre- and postsynaptic cardiac sympathetic function is altered in ischemic congestive heart failure (CHF). Whether there is a presynaptic-to-postsynaptic mismatch or whether mismatch is related to adverse cardiac events is unknown.In 13 patients with ischemic CHF and 25 aged-matched healthy volunteers, presynaptic function was measured by PET of (11)C-meta-hydroxyephedrine ((11)C-mHED), a norepinephrine (NE) analog. Postsynaptic function, beta-adrenergic receptor (BAR) density (B'(max)), was measured by imaging (11)C-CGP12177. Myocardial blood flow (MBF) was measured by imaging (15)O-water. Each heart was analyzed both globally and regionally, excluding infarcted regions, and a mismatch score, defined as the ratio of B'(max) to NE uptake (PS(nt))(,) was used to indicate mismatch of post- and presynaptic function.Global and regional MBF was not different between CHF and healthy subjects. The global measure of PS(nt) was lower in CHF (0.32 +/- 0.34) than that in healthy subjects (0.81 +/- 0.33, P0.0001) and in all 12 regions. Global B'(max) tended to be lower in CHF than that in healthy subjects (10.0 +/- 6.4 pmol/mL vs. 13.4 +/- 4.2, P = 0.056) and in all 12 regions. The global mismatch score (B'(max):PS(nt)) in CHF patients was significantly greater than that in healthy subjects (50.3 +/- 50.7 vs. 19.3 +/- 9.7, P = 0.005) and also greater in 11 of 12 regions. After 1.5 y of follow-up, 4 individuals had an adverse outcome (CHF death, new or recurrent sudden death, or progressive CHF leading to transplantation). Three of the 4 had mismatch scores3 times that of the healthy subjects or the CHF patients without an adverse outcome.Mismatch between pre- and postsynaptic left ventricular sympathetic function is present in patients with severe CHF and may be more marked in those with adverse outcomes.

In dual-modality PET/CT systems, the CT scan provides the attenuation map for PET attenuation correction. The current clinical practice of obtaining a single helical CT scan provides only a snapshot of the respiratory cycle, whereas PET occurs over multiple respiratory cycles. Misalignment of the attenuation map and emission image because of respiratory motion causes errors in the attenuation correction factors and artifacts in the attenuation-corrected PET image. To rectify this problem, we evaluated the use of cine CT, which acquires multiple low-dose CT images during a respiratory cycle. We evaluated the average and the intensity-maximum image of cine CT for cardiac PET attenuation correction. Methods: Cine CT data and cardiac PET data were acquired from a cardiac phantom and from multiple patient studies. The conventional helical CT, cine CT, and PET data of an axially translating phantom were evaluated with and without respiratory motion. For the patient studies, we acquired 2 cine CT studies for each PET acquisition in a rest–stress 13N-ammonia protocol. Three readers visually evaluated the alignment of 74 attenuation image sets versus the corresponding emission image and determined whether the alignment provided acceptable or unacceptable attenuation-corrected PET images. Results: In the phantom study, the attenuation correction from helical CT caused a major artifactual defect in the lateral wall on the PET image. The attenuation correction from the average and from the intensity-maximum cine CT images reduced the defect by 20% and 60%, respectively. In the patient studies, 77% of the cases using the average of the cine CT images had acceptable alignment and 88% of the cases using the intensity maximum of the cine CT images had acceptable alignment. Conclusion: Cine CT offers an alternative to helical CT for compensating for respiratory motion in the attenuation correction of cardiac PET studies. Phantom studies suggest that the average and the intensity maximum of the cine CT images can reduce potential respiration-induced misalignment errors in attenuation correction. Patient studies reveal that cine CT provides acceptable alignment in most cases and suggest that the intensity-maximum cine image offers a more robust alternative to the average cine image.

Objective: We investigated the agreement of multislice computed tomography angiography (CTA) and magnetic resonance angiography (MRA) in the quantitative measurement of carotid artery stenosis. The dependency of the agreement of the chosen post-processing procedures was also investigated. Methods: Fifty consecutive symptomatic patients were included in this study. In all patients, a CTA was performed with a 16-slice CT scanner. Within 30 days, the extracranial vessels were examined using a combined time-of-flight and contrast-enhanced MRA. The CT data sets were used to calculate the degree of stenosis according to the North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial, and Common Carotid methods by means of the 1-mm thick, transverse raw data (RD), a sagittal maximum-intensity projection reconstruction, and sagittal multiplanar reconstruction. In addition, a semiautomated analysis was done using a specialized postprocessing software. For all combinations of postprocessing procedures and methods of calculating the degree of stenosis, the correlation coefficient and the agreement based on Bland/Altman plots were calculated. Results: Eleven of the 100 primarily included carotid arteries could not be evaluated. The correlation coefficients for all combinations were comparable and lied in the interval between 0.932 and 0.787. The best correlation was found for the combination of RD/sagittal multiplanar reconstruction and ECST method. The evaluation of the agreement gave a systematic overestimation of CTA between 1.9% and 10.7% with a 95% confidence interval between ±26.7% and ±43.3%. With the semiautomated postprocessing software, additional 33 vessels could not be evaluated. The agreement of the calculated degrees of stenoses was worse than that of the planar procedures. Conclusions: CTA and MRA had a feasible agreement in measuring the degree of stenosis of the carotid arteries. The best result could be obtained for the evaluation of the RD and the NASCET method. In this case one has to take into account a systematic overestimation of CTA of 1.9%. The combination with an additional reconstructive post-processing procedure did not improve the result but might be useful for the radiologist to identify the location of the closest narrowing.

Misaligned attenuation correction factors lead to artifacts and quantitative errors in cardiac PET images, potentially resulting in inaccurate interpretation and/or incorrect clinical decisions. Artifacts from misaligned attenuation-emission scans are common with conventional PET imaging. The potential for misalignment/artifacts is further increased in dual modality PET/CT systems since CT images a snapshot of the respiratory cycle and PET images multiple respiratory cycles. In this work, we developed and tested a method for automated alignment of attenuation and emission data. The alignment process enforces the Radon consistency conditions on the emission data and is derived from previous work by Welch et al. The attenuation image volume is aligned through simple rigid body transformations with the emission data. We test the process with simulated data and measured patient data from two ammonia cardiac PET/CT exams.

Understanding cardiac receptor physiology is crucial to the study of cardiovascular diseases. The availability of noninvasive imaging technology in studying cardiac receptors has greatly expanded our knowledge of their roles in the pathogenesis of several cardiac disorders such as ischemia and heart failure. The dynamic nature of imaging “physiology” rather than anatomy often requires precise imaging protocols and complex mathematical modeling. The use of radiolabeled ligands adds the additional complications of radiation safety and radiopharmaceutical synthesis. Successful utilization of this technology must involve collaborative efforts of cardiologists, radiologists, radiochemists, physicists, mathematicians, technologists, and of course, referring physicians. Cardiac receptor imaging offers, in return, not only tremendous opportunities for scientific discovery in physiology and pathophysiology, but also opportunities for clinical decision making. Imaging is a powerful tool for following the patients’ responses to therapy and for predicting prognosis and dictating treatment. Much more effort is still needed to develop radiopharmaceutical agents for the various receptors and parts of the receptor systems that cannot be imaged currently. More research needs to be done to expand this technology for wider clinical application.

Vascular, or humoral, rejection (VR) of cardiac allografts is a distinct form of rejection diagnosed with immunofixation staining of endomyocardial biopsy tissue. To our knowledge, VR has not been identified previously with a noninvasive test. We present a symptomatic patient with VR and stress perfusion imaging evidence of impaired coronary flow reserve that normalized after treatment and resolution of VR.