The number of unrecognized myocardial infarction scars detected at DE-MRI increases during a 5-year follow-up.

OBJECTIVES: In an elderly population, the prevalence of unrecognized myocardial infarction (UMI) scars found via late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) imaging was more frequent than expected. This study investigated whether UMI scars detected with LGE-CMR at age 70 would be detectable at age 75 and whether the scar size changed over time. METHODS: From 248 participants that underwent LGE-CMR at age 70, 185 subjects underwent a follow-up scan at age 75. A myocardial infarction (MI) scar was defined as late enhancement involving the subendocardium. RESULTS: In the 185 subjects that underwent follow-up, 42 subjects had a UMI scar at age 70 and 61 subjects had a UMI scar at age 75. Thirty-seven (88 %) of the 42 UMI scars seen at age 70 were seen in the same myocardial segment at age 75. The size of UMI scars did not differ between age 70 and 75. CONCLUSIONS: The prevalence of UMI scars detected at LGE-CMR increases with age. During a 5-year follow-up, 88 % (37/42) of the UMI scars were visible in the same myocardial segment, reassuring that UMI scars are a consistent finding. The size of UMI scars detected during LGE-CMR did not change over time. KEY POINTS: • UMI scars detected by LGE-CMR are frequent in elderly. • The prevalence of UMI scars detected with LGE-CMR increases with age. • UMI scar size does not change over time.

Long-term prognosis of unrecognized myocardial infarction detected with cardiovascular magnetic resonance in an elderly population.

BACKGROUND: Individuals with unrecognized myocardial infarctions (UMIs) detected with cardiovascular magnetic resonance (CMR) constitute a recently defined group whose prognosis has not been fully evaluated. However, increasing evidence indicate that these individuals may be at considerable cardiovascular risk. The aim of the present study was to investigate the prognostic impact of CMR detected UMIs for major adverse cardiac events (MACE) in community living elderly individuals. METHODS: Late gadolinium enhancement CMR was performed in 248 randomly chosen 70-year-olds. Individuals with myocardial infarction (MI) scars, with or without a hospital diagnosis of MI were classified as recognized MI (RMI) or UMI, respectively. Medical records and death certificates were scrutinized. MACE was defined as cardiac death, non-fatal MI, a new diagnosis of angina pectoris, or symptom-driven coronary artery revascularization. RESULTS: During follow-up (mean 11 years) MACE occurred in 10 % (n = 18/182) of the individuals without MI scars, in 20 % (n = 11/55) of the individuals with UMI, and in 45 % (n = 5/11) of the individuals with RMI, with a significant difference between the UMI group and the group without MI scars (p = 0.045), and between the RMI group and the group without MI scars (p = 0.0004). Cardiac death and/or non-fatal MI occurred in 15, 5, and 3 of the individuals in the NoMI, UMI, and RMI group respectively. Hazards ratios for MACE adjusted for risk factors and sex were 2.55 (95 % CI 1.20-5.42; p = 0.015) for UMI and 3.28 (95 % CI1.16-9.22; p = 0.025) for RMI. CONCLUSIONS: The presence of a CMR detected UMI entailed a more than double risk for MACE in community living 70-year-old individuals.

Unrecognized myocardial infarctions assessed by cardiovascular magnetic resonance are associated with the severity of the stenosis in the supplying coronary artery.

BACKGROUND: A previous study has shown an increased prevalence of late gadolinium enhancement cardiovascular magnetic resonance (LGE CMR) detected unrecognized myocardial infarction (UMI) with increasing extent and severity of coronary artery disease. However, the coronary artery disease was evaluated on a patient level assuming normal coronary anatomy. Therefore, the aims of the present study were to investigate the prevalence of UMI identified by LGE CMR imaging in patients with stable angina pectoris and no known previous myocardial infarction; and to investigate whether presence of UMI is associated with stenotic lesions in the coronary artery supplying the segment of the myocardium in which the UMI is located, using coronary angiography to determine the individual coronary anatomy in each patient. METHODS: In this prospective multicenter study, we included patients with stable angina pectoris and without prior myocardial infarction, scheduled for coronary angiography. A LGE CMR examination was performed prior to the coronary angiography. The study cohort consisted of 235 patients (80 women, 155 men) with a mean age of 64.8 years. RESULTS: UMIs were found in 25% of patients. There was a strong association between stenotic lesions (≥70% stenosis) in a coronary artery and the presence of an UMI in the myocardial segments supplied by the stenotic artery; it was significantly more likely to have an UMI downstream a stenosis ≥ 70% as compared to < 70% (OR 5.1, CI 3.1-8.3, p < 0.0001). 56% of the UMIs were located in the inferior and infero-lateral myocardial segments, despite predominance for stenotic lesions in the left anterior descending artery. CONCLUSION: UMI is common in patients with stable angina and the results indicate that the majority of the UMIs are of ischemic origin due to severe coronary atherosclerosis. In contrast to what is seen in recognized myocardial infarctions, UMIs are predominately located in the inferior and infero-lateral myocardial segments. TRIAL REGISTRATION: The PUMI study is registered at ClinicalTrials.gov (NCT01257282).

Cardiac troponin I associated with the development of unrecognized myocardial infarctions detected with MRI.

BACKGROUND: Late enhancement MRI (LE-MRI) and cardiac troponin I (cTnI) are sensitive methods to detect subclinical myocardial injury. We sought to investigate the relation between plasma concentrations of cTnI measured with a high-sensitivity assay (hs-cTnI) and the development of unrecognized myocardial infarctions (UMIs) detected with LE-MRI. METHODS: After approval from the ethics committee and written informed consent were obtained, LE-MRI was performed on 248 randomly selected community-living 70-year-old volunteers and hs-cTnI was determined with a highly sensitive premarket assay. Five years later these individuals were invited to a second LE-MRI, and 176 of them (82 women, 94 men), who did not have a hospital diagnosis of MI, constitute the present study population. LE-MR images were analyzed by 2 radiologists independently and in a consensus reading, blinded to any information on previous disease or assessments. RESULTS: New or larger UMIs were detected in 37 participants during follow-up. Plasma concentrations of hs-cTnI at 70 years of age, which were mainly within what is considered to be the reference interval, were related to new or larger UMIs at 75 years of age with an odds ratio of 1.98 per 1 unit increase in ln-transformed cTnI (95% CI, 1.17-3.35; P = 0.010). Plasma concentrations of hs-cTnI at 70 years of age were associated with the volumes of the UMIs detected at 75 years of age (P = 0.028). CONCLUSIONS: hs-cTnI in 70-year-old community-living women and men was associated with the development of MRI-detected UMIs within 5 years.

Intravoxel incoherent motion MR imaging of the kidney: pilot study.

MR examinations (Achieva 3 T, Philips, Best, The Netherlands) were performed at five different occasions in a healthy volunteer (male 60 years) and in one renal cancer patient (male 78 years) with normal renal function (creatinine 88 µmol/L). Intravoxel incoherent motion (IVIM) coefficients D + D* were measured using respiratory-triggered diffusion-weighted spin-echo echo-planar imaging. Perfusion data of the patient were acquired using a saturation-recovery gradient-echo sequence and with the bolus of Gd-BOPTA (Multihance). D + D* were computed by monoexponential fitting of MR signal intensity attenuation versus b for b = 0, 50, 100, 150 s/mm(2). Perfusion parameters were evaluated with "NordicICE" software. The map of D + D* was compared qualitatively with the perfusion map computed from the Gd scan. D + D* values of the cortex and medulla were in the range 2.3-2.7 and 1.1-1.6 × 10(-3) mm(2)/s, respectively. In conclusion, in this pilot study a good qualitative relation between IVIM variables D + D* and renal perfusion has been found.

Magnetic resonance imaging flowmetry demonstrates portal vein dilatation subsequent to oxaliplatin therapy in patients with colorectal liver metastasis.

OBJECTIVES: Sinusoidal injury (SI) after oxaliplatin-based therapies for colorectal liver metastasis (CRLM) can increase postoperative morbidity. Preoperative methods to estimate SI are lacking. The aim of this study was to identify SI by evaluating portal vein haemodynamics. METHODS: Magnetic resonance imaging flowmetry (MRIF) was used to estimate portal vein haemodynamics in 29 patients with CRLM before liver surgery. Sinusoidal injury was evaluated from resected non-tumorous liver parenchyma according to the combined vascular injury (CVI) score of ≥3. RESULTS: All patients with SI (six of 29) received oxaliplatin; however, a significant association could not be proven (P= 0.148). Oxaliplatin-treated patients showed portal vein dilatation in both the SI and non-SI groups compared with patients who had not received oxaliplatin (Bonferroni corrected P= 0.003 and P= 0.039, respectively). Mean portal velocity tended to be lower in patients with SI compared with oxaliplatin-treated patients without SI (Bonferroni corrected P= 0.087). A mean portal velocity of ≤14.35 cm/s together with a cross-section area of ≥1.55 cm(2) was found to predict SI with sensitivity of 100% and specificity of 78%. CONCLUSIONS: Oxaliplatin treatment was associated with portal vein dilatation. Patients with SI showed a tendency towards decreased mean portal flow velocity. This may indicate that SI is associated with an increased resistance to blood flow in the liver parenchyma. Portal vein haemodynamic variables estimated by MRIF can identify patients without SI non-invasively.

Myocardial External Efficiency in Asymptomatic Severe Primary Mitral Regurgitation Using 11C-Acetate PET.

Subjects with asymptomatic moderate-to-severe or severe primary mitral regurgitation are closely observed for signs of progression or symptoms requiring surgical intervention. The role of myocardial metabolic function in progression of mitral regurgitation is poorly understood. We used 11C-acetate PET to noninvasively measure myocardial mechanical external efficiency (MEE), which is the energetic ratio of external cardiac work and left ventricular (LV) oxygen consumption. Methods: Forty-seven patients in surveillance with mitral regurgitation and no or minimal symptoms prospectively underwent PET, echocardiography, and cardiac MRI on the same day. PET was used to simultaneously measure cardiac output, LV mass, and oxygen consumption to establish MEE. PET findings were compared between patients and healthy volunteers (n = 9). MEE and standard imaging indicators of regurgitation severity, LV volumes, and function were studied as predictors of time to surgical intervention. Patients were followed a median of 3.0 y (interquartile range, 2.0-3.8 y), and the endpoint was reached in 22 subjects (47%). Results: MEE in patients reaching the endpoint (23.8% ± 5.0%) was lower than in censored patients (28.5% ± 4.5%, P = 0.002) or healthy volunteers (30.1% ± 4.9%, P = 0.001). MEE with a cutoff lower than 25.7% was significantly associated with the outcome (hazard ratio, 7.5; 95% CI, 2.7-20.6; P < 0.0001) and retained independent significance when compared with standard imaging parameters. Conclusion: MEE independently predicted time to progression requiring valve surgery in patients with asymptomatic moderate-to-severe or severe primary mitral regurgitation. The study suggests that inefficient myocardial oxidative metabolism precedes clinically observed progression in mitral regurgitation.

The value of pre-operative magnetic resonance spectroscopy in the assessment of steatohepatitis in patients with colorectal liver metastasis.

BACKGROUND & AIMS: Neoadjuvant chemotherapy prior to liver surgery for colorectal metastases can cause marked steatosis (≥ 33%) and steatohepatitis defined by non-alcoholic fatty liver disease activity score (NAS) as adverse effects on liver parenchyma. The aim of this study was to evaluate the steatosis level prior to liver resection using proton magnetic resonance spectroscopy ((1)H MRS) and to compare it with digital quantification of steatosis (DQS) and "classical" histopathology. METHODS: (1)H MRS at 3T evaluated steatosis in 35 patients with colorectal liver metastasis, planned for liver resection. Non-tumorous liver parenchyma samples were obtained after surgery for classical histopathology and DQS utilising automated software for quantification of histopathological slides using image processing. RESULTS: Classical histopathology defined marked steatosis in nine patients. Histopathology was less reliable than DQS (interclass correlation coefficient - ICC 0.771) or (1)H MRS (ICC 0.722) in steatosis estimation. (1)H MRS showed very similar steatosis levels and high reliability compared to DQS (ICC 0.955). Steatohepatitis was observed in seven patients (NAS ≥ 4) and (1)H MRS was able to predict it with 100% sensitivity and 89% specificity at threshold 10.9%, without knowing lobular inflammation or hepatocyte ballooning. BMI was significantly higher in the groups with marked steatosis and steatohepatitis. Standard blood tests or chemotherapy had no predictive value. CONCLUSIONS: (1)H MRS is a reliable non-invasive tool for steatosis assessment, and interestingly, it was able to predict steatohepatitis defined by NAS ≥ 4 in patients planned for liver resection of colorectal metastases after neoadjuvant chemotherapy.

Quantitative comparison of data-driven gating and external hardware gating for 18F-FDG PET-MRI in patients with esophageal tumors.

BACKGROUND: Respiratory motion during PET imaging reduces image quality. Data-driven gating (DDG) based on principal component analysis (PCA) can be used to identify respiratory signals. The use of DDG, without need for external devices, would greatly increase the feasibility of using respiratory gating in a routine clinical setting. The objective of this study was to evaluate data-driven gating in relation to external hardware gating and regular static image acquisition on PET-MRI data with respect to SUVmax and lesion volumes. METHODS: Sixteen patients with esophageal or gastroesophageal cancer (Siewert I and II) underwent a 6-min PET scan on a Signa PET-MRI system (GE Healthcare) 1.5-2 h after injection of 4 MBq/kg 18F-FDG. External hardware gating was done using a respiratory bellow device, and DDG was performed using MotionFree (GE Healthcare). The DDG raw data files and the external hardware-gating raw files were created on a Matlab-based toolbox from the whole 6-min scan LIST-file. For comparison, two 3-min static raw files were created for each patient. Images were reconstructed using TF-OSEM with resolution recovery with 2 iterations, 28 subsets, and 3-mm post filter. SUVmax and lesion volume were measured in all visible lesions, and noise level was measured in the liver. Paired t-test, linear regression, Pearson correlation, and Bland-Altman analysis were used to investigate difference, correlation, and agreement between the methods. RESULTS: A total number of 30 lesions were included in the study. No significant differences between DDG and external hardware-gating SUVmax or lesion volumes were found, but the noise level was significantly reduced in the DDG images. Both DDG and external hardware gating demonstrated significantly higher SUVmax (9.4% for DDG, 10.3% for external hardware gating) and smaller lesion volume (- 5.4% for DDG, - 6.6% for external gating) in comparison with non-gated static images. CONCLUSIONS: Data-driven gating with MotionFree for PET-MRI performed similar to external device gating for esophageal lesions with respect to SUVmax and lesion volume. Both gating methods significantly increased the SUVmax and reduced the lesion volume in comparison with non-gated static acquisition. DDG resulted in reduced image noise compared to external device gating and static images.

Identifying Morphological Indicators of Aging With Neural Networks on Large-Scale Whole-Body MRI.

A wealth of information is contained in images obtained by whole-body magnetic resonance imaging (MRI). Studying the link between the imaged anatomy and properties known from outside sources has the potential to give new insights into the underlying factors that manifest themselves in individual human morphology. In this work we investigate the expression of age-related changes in the whole-body image. A large dataset of about 32,000 subjects scanned from neck to knee and aged 44-82 years from the UK Biobank study was used for a machine-based analysis. We trained a convolutional neural network based on the VGG16 architecture to predict the age of a given subject based on image data from these scans. In 10-fold cross-validation on 23,000 of these images the network reached a mean absolute error (MAE) of 2.49 years (R2 = 0.83) and showed consistent performance on a separate test set of another 8,000 images. On a second test set of 100 images the network outperformed the averaged estimates given by three experienced radiologists, which reached an MAE of 5.58 years (R2 = 0.08), by more than three years on average. In an attempt to explain these findings, we employ saliency analysis that opens up the image-based criteria used by the automated method to human interpretation. We aggregate the saliency into a single anatomical visualization which clearly highlights structures in the aortic arch and knee as primary indicators of age.

Signal intensity of myocardial scars at delayed-enhanced MRI.

BACKGROUND: Traditionally, unrecognized myocardial infarction (UMI) is defined as the appearance, in a non-acute setting, of a new diagnostic Q wave. In the recent past, delayed-enhanced magnetic resonance imaging (DE-MRI) has provided a new imaging method for evaluating myocardial viability and to detect myocardial scars. PURPOSE: To investigate differences in tissue characteristics between UMI and recognized myocardial infarction (RMI) scars, by assessing the signal intensity (SI) detected by DE-MRI. MATERIAL AND METHODS: A randomized subgroup of 259 subjects from the Prospective Investigation of the Vasculature of Uppsala Seniors (PIVUS) study was submitted to cardiac magnetic resonance imaging (MRI). DE-MRI-detected myocardial scars were divided in two groups, UMI and RMI, according to the hospital medical records. The scars detected by DE-MRI were analyzed by measuring SI ratio of scar tissue to normal myocardium. RESULTS: The mean SI ratio in the UMI group (4.5+/-3.0, mean+/-SD) was lower than in the RMI group 8.9+/-5.1 (P-value = 0.001). This difference was still significant (P<0.0001) after adjustment for gender, body mass index, time of image acquisition after gadolinium administration, scar transmurality, or total myocardial infarction mass. CONCLUSION: The difference in the SI ratio of the scars between the two groups most likely reflects a different contrast distribution volume of the tissues, which might indicate that UMI and RMI tissues diverge in tissue composition.

Prevalence and pathophysiological mechanisms of elevated cardiac troponin I levels in a population-based sample of elderly subjects.

AIMS: To evaluate the prevalence of cardiac troponin I (cTnI) elevation in an elderly community population and the association of cTnI levels with cardiovascular risk factors, vascular inflammation, atherosclerosis, cardiac performance, and areas indicative of infarcted myocardium identified by cardiac magnetic resonance imaging. METHODS AND RESULTS: cTnI elevation defined as cTnI levels >0.01 microg/L (Access AccuTnI, Beckman Coulter) was found in 21.8% of the study participants (n = 1005). cTnI > 0.01 microg/L was associated with cardiovascular high-risk features, the burden of atherosclerosis in the carotid arteries, left-ventricular mass, and impaired left-ventricular systolic function. No associations were found between cTnI and inflammatory activity, diastolic dysfunction, or myocardial scars. Male gender (OR 1.6; 95% CI 1.1-2.4), ischaemic ECG changes (OR 1.7; 95% CI 1.1-2.7), and NT-pro-brain natriuretic peptide levels (OR 1.4; 95% CI 1.1-1.7) independently predicted cTnI > 0.01 microg/L. cTnI > 0.01 microg/L correlated also to an increased cardiovascular risk according to the Framingham risk score. CONCLUSION: cTnI > 0.01 microg/L is relatively common in elderly subjects and is associated with cardiovascular high-risk features and impaired cardiac performance. Cardiac troponin determined by a highly sensitive assay might thus serve as an instrument for the identification of subjects at high cardiovascular risk in general populations.

Unrecognized myocardial infarction assessed by cardiac magnetic resonance imaging is associated with adverse long-term prognosis.

BACKGROUND: Unrecognized myocardial infarctions (UMIs) are common. The study is an extension of a previous study, aiming to investigate the long-term (>5 year) prognostic implication of late gadolinium enhancement cardiovascular magnetic resonance (LGE-CMR) detected UMI in patients with suspected stable coronary artery disease (CAD) without previously diagnosed myocardial infarction (MI). METHODS: In 235 patients with suspected stable CAD without previous MI, LGE-CMR imaging and coronary angiography were performed. LGE with a subendocardial component detectable in more than one imaging plane was required to indicate UMI. The stenosis grade of the coronary arteries was determined, including in the artery supplying an infarcted area. Stenosis ≥70% stenosis was considered significant. Patients were followed for 5.4 years in mean regarding a composite endpoint of cardiovascular death, MI, hospitalization due to heart failure, stable or unstable angina. RESULTS: UMI were present in 58 of 235 patients (25%). Thirty-nine of the UMIs were located downstream of a significant coronary stenosis. During the follow-up 40 patients (17.0%) reached the composite endpoint. Of patients with UMI, 34.5% (20/58) reached the primary endpoint compared to 11.3% (20/177) of patients with no UMI (HR 3.7, 95% CI 2.0-6.9, p<0.001). The association between UMI and outcome remained (HR 2.3, 95% CI 1.2-4.4, p = 0.012) after adjustments for age, gender, extent of CAD and all other variables univariate associated with outcome. Sixteen (41%) of the patients with an UMI downstream of a significant stenosis reached the endpoint compared to four (21%) patients with UMI and no relation to a significant stenosis (HR 2.4, 95% CI 0.8-7.2, p = 0.12). CONCLUSION: The presence of UMI was independently associated with an increased risk of cardiovascular events during long-term follow up.

Unrecognized Myocardial Infarction Assessed by Cardiac Magnetic Resonance Imaging--Prognostic Implications.

BACKGROUND: Clinically unrecognized myocardial infarctions (UMI) are not uncommon and may be associated with adverse outcome. The aims of this study were to determine the prognostic implication of UMI in patients with stable suspected coronary artery disease (CAD) and to investigate the associations of UMI with the presence of CAD. METHODS AND FINDINGS: In total 235 patients late gadolinium enhancement cardiovascular magnetic resonance (LGE-CMR) imaging and coronary angiography were performed. For each patient with UMI, the stenosis grade of the coronary branch supplying the infarcted area was determined. UMIs were present in 25% of the patients and 67% of the UMIs were located in an area supplied by a coronary artery with a stenosis grade ≥70%. In an age- and gender-adjusted model, UMI independently predicted the primary endpoint (composite of death, myocardial infarction, resuscitated cardiac arrest, hospitalization for unstable angina pectoris or heart failure within 2 years of follow-up) with an odds ratio of 2.9; 95% confidence interval 1.1-7.9. However, this association was abrogated after adjustment for age and presence of significant coronary disease. There was no difference in the primary endpoint rates between UMI patients with or without a significant stenosis in the corresponding coronary artery. CONCLUSIONS: The presence of UMI was associated with a threefold increased risk of adverse events during follow up. However, the difference was no longer statistically significant after adjustments for age and severity of CAD. Thus, the results do not support that patients with suspicion of CAD should be routinely investigated by LGE-CMR for UMI. However, coronary angiography should be considered in patients with UMI detected by LGE-CMR. TRIAL REGISTRATION: ClinicalTrials.gov NTC01257282.

Unrecognized myocardial infarctions detected by cardiac magnetic resonance imaging are associated with cardiac troponin I levels.

BACKGROUND: Both unrecognized myocardial infarction (UMI) and elevated levels of biomarkers are common in patients with stable coronary artery disease (CAD). The objective of this study was to determine the association between levels of cardiac biomarkers, UMI and extent of CAD in patients with stable CAD. METHODS: A total of 235 patients (median age: 65years; 34% women) with stable CAD without previously known myocardial infarction were examined with late gadolinium enhancement cardiovascular magnetic resonance imaging and coronary angiography. Blood samples were drawn at enrolment and high sensitivity cardiac troponin I (cTnI), NT-proBNP and Galectin-3 were analyzed. RESULTS: UMI was detected in 58 patients (25%). The median levels of cTnI, NT-proBNP and Galectin-3 were significantly higher in patients with UMI compared to those without, (p<0.001, p=0.006 and p=0.033, respectively). After adjustment for cardiovascular risk factors, left ventricular ejection fraction and renal function, cTnI remained independently associated with the presence of UMI (p=0.031) and the extent of CAD (p=0.047). Neither NT-proBNP, nor Galectin-3, was independently associated with UMI or extent of CAD. CONCLUSIONS: The independent association between levels of cTnI and UMI indicates a common pathophysiological pathway for the cTnI elevation and development of UMI. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov (NCT01257282).

Cardiac Imaging to Evaluate Left Ventricular Diastolic Function.

Left ventricular diastolic dysfunction in clinical practice is generally diagnosed by imaging. Recognition of heart failure with preserved ejection fraction has increased interest in the detection and evaluation of this condition and prompted an improved understanding of the strengths and weaknesses of different imaging modalities for evaluating diastolic dysfunction. This review briefly provides the pathophysiological background for current clinical and experimental imaging parameters of diastolic dysfunction, discusses the merits of echocardiography relative to other imaging modalities in diagnosing and grading diastolic dysfunction, summarizes lessons from clinical trials that used parameters of diastolic function as an inclusion criterion or endpoint, and indicates current areas of research.

Automatic extraction of forward stroke volume using dynamic PET/CT: a dual-tracer and dual-scanner validation in patients with heart valve disease.

BACKGROUND: The aim of this study was to develop and validate an automated method for extracting forward stroke volume (FSV) using indicator dilution theory directly from dynamic positron emission tomography (PET) studies for two different tracers and scanners. METHODS: 35 subjects underwent a dynamic (11)C-acetate PET scan on a Siemens Biograph TruePoint-64 PET/CT (scanner I). In addition, 10 subjects underwent both dynamic (15)O-water PET and (11)C-acetate PET scans on a GE Discovery-ST PET/CT (scanner II). The left ventricular (LV)-aortic time-activity curve (TAC) was extracted automatically from PET data using cluster analysis. The first-pass peak was isolated by automatic extrapolation of the downslope of the TAC. FSV was calculated as the injected dose divided by the product of heart rate and the area under the curve of the first-pass peak. Gold standard FSV was measured using phase-contrast cardiovascular magnetic resonance (CMR). RESULTS: FSVPET correlated highly with FSVCMR (r = 0.87, slope = 0.90 for scanner I, r = 0.87, slope = 1.65, and r = 0.85, slope = 1.69 for scanner II for (15)O-water and (11)C-acetate, respectively) although a systematic bias was observed for both scanners (p < 0.001 for all). FSV based on (11)C-acetate and (15)O-water correlated highly (r = 0.99, slope = 1.03) with no significant difference between FSV estimates (p = 0.14). CONCLUSIONS: FSV can be obtained automatically using dynamic PET/CT and cluster analysis. Results are almost identical for (11)C-acetate and (15)O-water. A scanner-dependent bias was observed, and a scanner calibration factor is required for multi-scanner studies. Generalization of the method to other tracers and scanners requires further validation.

High in-plane resolution T2-weighted magnetic resonance imaging of acute myocardial ischemia in pigs using the intravascular contrast agent NC100150 injection.

RATIONALE AND OBJECTIVES: The intravascular contrast agent NC100150 injection was tested for its ability to demarcate nonperfused myocardium in a porcine model of coronary occlusion. MATERIALS AND METHODS: A T2-weighted fast spin echo sequence was acquired ex vivo and in vivo during first pass and steady-state circulation of the contrast agent in 2 dosages (2 and 5 mg Fe/kg bw) or saline. RESULTS: Ex vivo, in the high-dose group, the volume of nonperfused myocardium determined from T2-weighted images was 99% of that determined from photographs where perfused myocardium stained with fluorescein. A significantly higher contrast to noise ratio between perfused and nonperfused myocardium was found (both ex and in vivo in steady state) compared with the control group. During first pass, a significant reduction in signal intensity (74 +/- 18%) was found in perfused myocardium after contrast injection. CONCLUSION: NC100150 injection, combined with T2-weighted turbo spin echo imaging, allowed detailed visualization of non-perfused myocardium in the steady state, which corresponded to the area at risk as determined by fluorescein.

In and ex vivo MR evaluation of acute myocardial ischemia in pigs by determining R1 in steady state after the administration of the intravascular contrast agent NC100150 injection.

RATIONALE AND OBJECTIVES: To study the dose response in perfused and nonperfused myocardium by measuring relaxation rate (R1) in a steady-state situation after injection of the intravascular contrast agent NC100150 Injection in pigs and whether the dose response differs in vivo and ex vivo. MATERIALS AND METHODS: The left anterior descending artery was occluded. R1 was measured using a Look-Locker sequence for 2 dose groups (2 mg Fe/kg bw, n = 4, and 5 mg Fe/kg bw, n = 5) and a control group (n = 3). RESULTS: A significant increase in R1 was found in perfused myocardium after contrast agent injection, in contrast to nonperfused myocardium. There was a significantly larger difference in R1 between perfused and nonperfused myocardium in the 5 mg Fe/kg bw dose group compared with the other 2 groups. The difference in R1 between perfused and nonperfused myocardium was significantly higher in vivo than ex vivo. CONCLUSION: A nearly linear R1 dose response was found in perfused myocardium in vivo. The dose response ex vivo was less steep possibly due to larger water exchange limitations.