ECV Measurements Research Articles

A comparison of myocardial magnetic resonance extracellular volume mapping at 3 T against histology of tissue collagen in severe aortic valve stenosis and obstructive hypertrophic cardiomyopathy

ObjectiveQuantitative extracellular volume fraction (ECV) mapping with MRI is commonly used to investigate in vivo diffuse myocardial fibrosis. This study aimed to validate ECV measurements against ex vivo histology of myocardial tissue samples from patients with aortic valve stenosis or hypertrophic cardiomyopathy.Materials and methodsSixteen patients underwent MRI examination at 3 T to acquire native T1 maps and post-contrast T1 maps after gadobutrol administration, from which hematocrit-corrected ECV maps were estimated. Intra-operatively obtained myocardial tissue samples from the same patients were stained with picrosirius red for quantitative histology of myocardial interstitial fibrosis. Correlations between in vivo ECV and ex vivo myocardial collagen content were evaluated with regression analyses.ResultsSeptal ECV was 30.3% ± 4.6% and correlated strongly (n = 16, r = 0.70; p = 0.003) with myocardial collagen content. Myocardial native T1 values (1206 ± 36 ms) did not correlate with septal ECV (r = 0.41; p = 0.111) or with myocardial collagen content (r = 0.32; p = 0.227).DiscussionWe compared myocardial ECV mapping at 3 T against ex vivo histology of myocardial collagen content, adding evidence to the notion that ECV mapping is a surrogate marker for in vivo diffuse myocardial fibrosis.

Impact of Sex and Cardiovascular Risk Factors on Myocardial T1, Extracellular Volume Fraction, and T2 at 3 Tesla: Results From the Population-Based, Hamburg City Health Study.

Reliable reference intervals are crucial for clinical application of myocardial T1 and T2 mapping cardiovascular magnetic resonance imaging. This study evaluated the impact of sex and cardiovascular risk factors on myocardial T1, extracellular volume fraction (ECV), and T2 at 3T in the population-based HCHS (Hamburg City Health Study). The final study sample consisted of 1576 consecutive HCHS participants between 46 and 78 years without prevalent heart disease, including 1020 (67.3%) participants with hypertension and 110 (7.5%) with diabetes. T1 and T2 mapping were performed on a 3T scanner using 5b(3b)3b modified Look-Locker inversion recovery and T2 prepared, fast-low-angle shot sequence, respectively. Stepwise regression analyses were performed to identify variables with an independent impact on T1, ECV, and T2. Reference intervals were defined as the interval between the 2.5% and 97.5% quantiles. Sex was the major independent influencing factor of myocardial native T1, ECV, and T2. Female patients had significantly higher upper limits of reference intervals for native T1 (1112-1261 versus 1079-1241 ms), ECV (23%-33% versus 22%-32%), and T2 (36-46 versus 35-45 ms) compared with male patients (all P<0.001). Cardiovascular risk factors, such as diabetes and hypertension, did not systematically affect native T1. There was an independent association of T2 by hypertension and, to a lesser degree, by left ventricular mass, heart rate (all P<0.001), and body mass index (P=0.001). Sex needs to be considered as the major, independent influencing factor for clinical application of myocardial T1, ECV, and T2 measurements. Consequently, sex-specific reference intervals should be used in clinical routine. Our findings suggest that there is no need for specific reference intervals for myocardial T1 and ECV measurements in individuals with cardiovascular risk factors. However, hypertension should be considered as an additional factor for clinical application of T2 measurements. URL: https://www. gov; Unique identifier: NCT03934957.

484 Importance Of Imaging Acquisition Protocol And Post-processing Analysis Methods For Extracellular Volume Fraction Assessment By Computed Tomography

Introduction: Myocardial extracellular volume fraction (ECV) assessment by contrast computed tomography angiography (CTA) is possible, although the acquisition protocol and post-processing methodology is controversial. We aimed to assess the image quality for ECV assessment according to patient characteristics, scan acquisition modes (high-pitch vs. prospective gated), and compare focal, regional vs. global ECV measurements.

In This Issue of the Journal

In This Issue of the Journal

Improved cardiac T1 mapping accuracy and precision with a new hybrid MOLLI and SASHA technique: MOSHA

PurposeTo develop and validate a new myocardial T1 mapping sequence (MOSHA) which is based on a combination of the modified Look-Locker inversion recovery (MOLLI) and the saturation recovery single-shot acquisition (SASHA) sequences. MethodsPrior studies have shown that myocardial T1 mapping by SASHA is more accurate but less precise than MOLLI. A new myocardial T1 mapping technique (MOSHA) based on single-shot acquisitions is developed by combining the MOLLI and SASHA sequences. Phantom and patient studies on 15 patients (9 males, median age 21 years) were performed to validate and compare MOSHA with the MOLLI and SASHA sequences in terms of accuracy and precision. ResultsIn the phantom study, MOSHA was as accurate as SASHA (P-value = 0.88) and as precise as MOLLI (P-value = 0.59). Similar trends were observed in the patient study. Compared to SASHA, MOSHA accuracy was comparable for blood pre-contrast (P-value≥0.10) and post-contrast (P-value≥0.70), and for myocardium pre-contrast (P-value = 0.70) and post-contrast (P-value = 0.09). Compared to MOLLI, MOSHA precision was lower for blood pre-contrast (P-value<0.01) and higher for blood post-contrast (P-value≤0.01), and comparable for myocardium pre-contrast (P-value = 0.24) and post-contrast (P-value = 0.07). Synthetic Extracellular volume fraction (ECV) calculated by MOSHA was more precise than those of SASHA and MOLLI (P-value≤0.01). ConclusionIn phantom studies and patients, MOSHA has comparable accuracy as SASHA and nearly similar precision as MOLLI for T1 mapping. Precision of MOSHA was better than MOLLI and SASHA in synthetic ECV measurements. Therefore, it may be a superior choice in clinical practice for a precise and accurate calculation of T1 and ECV.

Prognostic Impact of Myocardial Extracellular Volume Fraction Assessment Using Dual-Energy Computed Tomography in Patients Treated With Aortic Valve Replacement for Severe Aortic Stenosis.

BackgroundMyocardial extracellular volume fraction (ECV), measured by cardiac magnetic resonance imaging, is a useful prognostic marker for patients who have undergone aortic valve replacement (AVR) for aortic stenosis. However, the prognostic significance of ECV measurements based on computed tomography (CT) is unclear. This study evaluated the association between ECV measured with dual‐energy CT and clinical outcomes in patients with aortic stenosis who underwent transcatheter or surgical AVR.Methods and ResultsWe retrospectively enrolled 95 consecutive patients (age, 84.0±5.0 years; 75% women) with severe aortic stenosis who underwent preprocedural CT for transcatheter AVR planning. ECV was measured using iodine density images obtained by delayed enhancement dual‐energy CT. The primary end point was a composite outcome of all‐cause death and hospitalization for heart failure after AVR. The mean ECV measured with CT was 28.1±3.8%. During a median follow‐up of 2.6 years, 22 composite outcomes were observed, including 15 all‐cause deaths and 11 hospitalizations for heart failure. In Kaplan‐Meier analysis, the high ECV group (≥27.8% [median value]) had significantly higher rates of composite outcomes than the low ECV group (<27.8%) (log‐rank test, P=0.012). ECV was the only independent predictor of adverse outcomes on multivariable Cox regression analysis (hazards ratio, 1.25; 95% CI, 1.10‒1.41; P<0.001).ConclusionsMyocardial ECV measured with dual‐energy CT in patients who underwent aortic valve intervention was an independent predictor of adverse outcomes after AVR.

CMR-based T1-mapping offers superior diagnostic value compared to longitudinal strain-based assessment of relative apical sparing in cardiac amyloidosis

Cardiac amyloidosis (CA) is an infiltrative disease. In the present study, we compared the diagnostic accuracy of cardiovascular magnetic resonance (CMR)-based T1-mapping and subsequent extracellular volume fraction (ECV) measurement and longitudinal strain analysis in the same patients with (a) biopsy-proven cardiac amyloidosis (CA) and (b) hypertrophic cardiomyopathy (HCM). N = 30 patients with CA, N = 20 patients with HCM and N = 15 healthy control patients without relevant cardiac disease underwent dedicated CMR studies. The CMR protocol included standard sequences for cine-imaging, native and post-contrast T1-mapping and late-gadolinium-enhancement. ECV measurements were based on pre- and post-contrast T1-mapping images. Feature-tracking analysis was used to calculate 3D left ventricular longitudinal strain (LV-LS) in basal, mid and apical short-axis cine-images and to assess the presence of relative apical sparing. Receiver-operating-characteristic analysis revealed an area-under-the-curve regarding the differentiation of CA from HCM of 0.984 for native T1-mapping (p < 0.001), of 0.985 for ECV (p < 0.001) and only 0.740 for the “apical-to-(basal + midventricular)”-ratio of LV-LS (p = 0.012). A multivariable logistical regression analysis showed that ECV was the only statistically significant predictor of CA when compared to the parameter LV-LS or to the parameter “apical-to-(basal + midventricular)” LV-RLS-ratio. Native T1-mapping and ECV measurement are both superior to longitudinal strain measurement (with assessment of relative apical sparing) regarding the appropriate diagnosis of CA.

Measuring myocardial extracellular volume of the right ventricle in patients with congenital heart disease

The right ventricle´s (RV) characteristics—thin walls and trabeculation—make it challenging to evaluate extracellular volume (ECV). We aimed to assess the feasibility of RV ECV measurements in congenital heart disease (CHD), and to introduce a novel ECV analysis tool. Patients (n = 39) and healthy controls (n = 17) underwent cardiovascular magnetic resonance T1 mapping in midventricular short axis (SAX) and transverse orientation (TRANS). Regions of interest (ROIs) were evaluated with regard to image quality and maximum RV wall thickness per ROI in pixels. ECV from plane ROIs was compared with values obtained with a custom-made tool that derives the mean T1 values from a “line of interest” (LOI) centered in the RV wall. In CHD, average image quality was good (no artifacts in the RV, good contrast between blood/myocardium), and RV wall thickness was 1–2 pixels. RV ECV was not quantifiable in 4/39 patients due to insufficient contrast or wall thickness < 1 pixel. RV myocardium tended to be more clearly delineated in SAX than TRANS. ECV from ROIs and corresponding LOIs correlated strongly in both directions (SAX/TRANS: r = 0.97/0.87, p < 0.001, respectively). In conclusion, RV ECV can be assessed if image quality allows sufficient distinction between myocardium and blood, and RV wall thickness per ROI is ≥ 1 pixel. T1 maps in SAX are recommended for RV ECV analysis. LOI application simplifies RV ECV measurements.

CMR-derived ECVs vary with myocardial region and associate with the regional wall thickness

This study was designed to identify whether the position and size of the region of interest (ROI) influence extracellular volume fraction (ECV) measurements. Patients with localized (n = 203) or infiltrative (n = 215) cardiomyopathies and 36 normal controls were enrolled in this study. ECV measurements at 4 different regions, including the anterior, septal, posterior and lateral wall regions, were measured, and all groups were compared. Regional ECV was correlated with the corresponding regional wall thickness. The diagnostic power to differentiate the myocardial abnormalities was evaluated for each myocardial region. ECVs measured using five different ROI sizes within each myocardial region were compared. Our results showed that ECVs varied among the myocardial regions, and this variation was significantly associated with regional wall thicknesses. For the detection of myocardial abnormalities, regional ECV revealed similar results as ECV derived from the whole region except for the anterior region. No significant difference was found in the ECVs measured using the five different ROI sizes. In conclusion, CMR-derived ECVs vary with myocardial region, and this variation is significantly associated with the regional wall thickness. In contrast, the measured size of the ROI has less of an effect on the ECV.

Ruling in or out the presence of cardiac amyloidosis based on cut-off values using T1-mapping – caution is required regarding the control group

Abstract Background Cardiac amyloidosis (CA) is an infiltrative disease that is characterized by accumulation of amyloid deposits in the interstitium of the myocardium. In contrast, hypertrophic cardiomyopathy (HCM) is caused by a disorganized arrangement of myocyte hypertrophy as well as expanded extracellular matrix, composed of interstitial and replacement fibrosis. Purpose A diagnostic algorithm based on (native) T1-mapping using cardiovascular magnetic resonance (CMR) was suggested in a recent study for the diagnosis of CA: A native T1 &amp;lt;1,036ms was mentioned to have a 98% negative predictive value (NPV) for ruling out CA whereas a native T1 &amp;gt;1,164ms showed a 98% positive predictive value (PPV) for the presence of CA. In the present study, we critically addressed the calculation of such cut-off values considering possible differences in the composition of the control group. Methods N=30 patients with CA, N=20 patients with HCM and N=15 healthy controls without relevant cardiac disease underwent dedicated CMR studies on a 1.5-T MR scanner. The CMR protocol comprised standard sequences for cine-imaging, native and post-contrast MOLLI-based T1-mapping and late-gadolinium-enhancement (LGE). ECV measurements were based on pre- and post-contrast T1-mapping images. Results Native T1 and ECV were significantly increased in CA compared to HCM and receiver operating characteristic (ROC) analyses revealed an area-under-the-curve (AUC) = 0.984 for native T1 (p&amp;lt;0.001) and AUC = 0.985 for ECV (p&amp;lt;0.001) regarding the diagnosis of CA). When CA patients were compared to HCM patients (excluding healthy controls), a native T1 &amp;lt;1,036ms or an ECV &amp;lt;33% were associated with a 99% NPV for ruling out CA whereas a native T1 ≥1,082ms or an ECV ≥41% were associated with a 99% PPV for diagnosis of CA. However, when CA patients were compared to healthy controls (excluding HCM patients), a native T1 &amp;lt;1,025ms or an ECV &amp;lt;34% were associated with a 99% NPV for ruling out CA whereas a native T1 ≥1,025ms or an ECV ≥34% were associated with a 99% PPV for diagnosis of CA since there was no overlap in native T1 and ECV values between CA patients and healthy controls. Conclusion Cut-off values for native T1 or ECV derived from ROC analyses (in a specific group of study patients) for ruling in or out the presence of CA are – amongst others - determined by the native T1 and ECV values of the respective “control group”. A different composition of the control group (e.g. HCM patients vs. healthy volunteers) will result in different cut-off values. Hence, previously suggested cut-off values obtained in single center studies need to be considered carefully – with a special attention to the control group of the underlying study – and should not be transferred to other centers carelessly. Funding Acknowledgement Type of funding source: None

Cardiovascular Magnetic Resonance Imaging Tissue Characterization in Non-ischemic Cardiomyopathies

In this review, we will focus the role of CMR in dilated cardiomyopathy and genetic cardiomyopathy. Non-invasive imaging plays a crucial rule in the diagnostic workup of cardiomyopathies. In these entities, echocardiography is the first-line imaging tool for diagnostic assessment, but CMR has the unique capability to identify and differentiate the underlying pathology, mainly through tissue characterization, even if the EF is preserved. Myocardial tissue characterization is crucial for adequate prognostication and guiding of therapy. Visual, semi-quantitative, and quantitative methods allow the accurate description of myocardial pathologies such as edema, hyperemia, hypoperfusion, and fibrosis. Basic CMR protocols and standardized post-processing methods are well established and routinely performed. CMR has the ability to characterize concomitantly the myocardial tissue characteristics using techniques such as LGE, T1 mapping with ECV measurements, and T2 mapping, and also deformation functional parameters (i.e., strain) and thus provides important insights into the underlying etiology of cardiomyopathy and prognosis. The results of several studies show that CMR findings are associated with clinical outcomes and can inform the management of these patients, including longitudinal assessment of treatment response. CMR should be routinely used in the workup of patients with non-ischemic cardiomyopathy for both diagnostic and prognostic applications. The presence of LV dilatation and systolic dysfunction in the absence of significant coronary artery disease together with valvular diseases represents a significant etiology to cause cardiomyopathy in cardiology practices. Additionally, other etiologies as infiltrative heart diseases, channelopathy/genetic cardiomyopathy and cardiac involvement in systemic diseases and oncologic process complete the spectrum that may range from isolated LV involvement or biventricular failure. Non-invasive imaging plays a crucial rule in the diagnostic workup of cardiomyopathies. In these entities, echocardiography is the first-line imaging tool for diagnostic assessment, but CMR has the unique capability to identify and differentiate the underlying pathology, mainly through tissue characterization, even if the EF is preserved. Myocardial tissue characterization is crucial for adequate prognostication and guiding of therapy. Visual, semi-quantitative, and quantitative methods allow the accurate description of myocardial pathologies such as edema, hyperaemia, hypoperfusion, and fibrosis. Basic CMR protocols and standardized post-processing methods are well established and routinely performed.

Measuring extracellular volume fraction by MRI: First verification of values given by clinical sequences.

PurposeTo verify MR measurements of myocardial extracellular volume fraction (ECV) based on clinically applicable T1‐mapping sequences against ECV measurements by radioisotope tracer in pigs and to relate the results to those obtained in volunteers.MethodsBetween May 2016 and March 2017, 8 volunteers (25 ± 4 years, 3 female) and 8 pigs (4 female) underwent ECV assessment with SASHA, MOLLI5(3b)3, MOLLI5(3s)3, and MOLLI5s(3s)3s. Myocardial ECV was measured independently in pigs using a radioisotope tracer method.ResultsIn pigs, ECV in normal myocardium was not different between radioisotope (average ± standard deviation; 19 ± 2%) and SASHA (21 ± 2%; P = 0.086). ECV was higher by MOLLI5(3b)3 (26 ± 2%), MOLLI5(3s)3 (25 ± 2%), and MOLLI5s(3s)3s (25 ± 2%) compared with SASHA or radioisotope (P ≤ 0.001 for all). ECV in volunteers was higher by MOLLI5(3b)3 (26 ± 3%) and MOLLI5(3s)3 (26 ± 3%) than by SASHA (22 ± 3%; P = 0.022 and P = 0.033). No difference was found between MOLLI5s(3s)3s (25 ± 3%) and SASHA (P = 0.225). Native T1 of blood and myocardium as well as postcontrast T1 of myocardium was consistently lower using MOLLI compared with SASHA. ECV increased over time as measured by MOLLI5(3b)3 and MOLLI5(3s)3 for pigs (0.08% and 0.07%/min; P = 0.004 and P = 0.013) and by MOLLI5s(3s)3s for volunteers (0.07%/min; P = 0.032) but did not increase as measured by SASHA.ConclusionClinically available MOLLI and SASHA techniques can be used to accurately estimate ECV in normal myocardium where MOLLI‐sequences show minor overestimation driven by underestimation of postcontrast T1 when compared with SASHA. The timing of imaging after contrast administration affected the measurement of ECV using some variants of the MOLLI sequence.

Cardiac magnetic resonance T1 and extracellular volume mapping with motion correction and co-registration based on fast elastic image registration

ObjectiveOur aim was to investigate the technical feasibility of a novel motion compensation method for cardiac magntic resonance (MR) T1 and extracellular volume fraction (ECV) mapping.Materials and methodsNative and post-contrast T1 maps were obtained using modified look-locker inversion recovery (MOLLI) pulse sequences with acquisition scheme defined in seconds. A nonrigid, nonparametric, fast elastic registration method was applied to generate motion-corrected T1 maps and subsequently ECV maps. Qualitative rating was performed based on T1 fitting-error maps and overlay images. Local deformation vector fields were produced for quantitative assessment. Intra- and inter-observer reproducibility were compared with and without motion compensation.ResultsEighty-two T1 and 39 ECV maps were obtained in 21 patients with diverse myocardial diseases. Approximately 60% demonstrated clear quality improvement after motion correction for T1 mapping, particularly for the poor-rating cases (23% before vs 2% after). Approximately 67% showed further improvement with co-registration in ECV mapping. Although T1 and ECV values were not clinically significantly different before and after motion compensation, there was improved intra- and inter-observer reproducibility after motion compensation.ConclusionsAutomated motion correction and co-registration improved the qualitative assessment and reproducibility of cardiac MR T1 and ECV measurements, allowing for more reliable ECV mapping.

P3330Cardiac magnetic resonance including T1 mapping in patients with Duchenne and Becker muscular dystrophy

Background and purpose: Cardiac involvement leading to progressive heart failure is a major cause of death in Duchenne and Becker muscular dystrophy (DMD/BMD) patients. T1 mapping and extracellular volume fraction (ECV) calculation are unique techniques for assessing the very early phases of cardiac involvement. The aim of the study was to compare native T1 and ECV measurements between visually non-fibrotic myocardium of DMD/BMD patients and controls. Methods: In total, 50 male individuals – 39 DMD/BMD patients (14±5 years) and 11 matched controls (17±3 years, p = NS) without history predisposing to cardiac dysfunction or fibrosis, but with a clinical indication for cardiovascular magnetic resonance (CMR) evaluation underwent CMR examination. Native and post contrast T1 mapping using Modified Look-Locker Inversion-recovery (MOLLI) sequence was included. Data points collected include left ventricular (LV) ejection fraction (EF), indexed end-diastolic LV volume (iEDV), indexed left ventricular mass, mitral annular plane systolic excursion (MAPSE), presence of late gadolinium enhancement (LGE), native T1, and ECV. Results: DMD/BMD subjects had LVEF of 59±13%, iEDV 56±22, iSV 31±8, MAPSE 11±1; 15/35 (43%) had LGE, all confined to the lateral wall. Five (13%) of them had LVEF <50%. Controls had LVEF 65±8% (p = NS), iEDV 59±9 (p = NS), iSV 38±8 (p<0.05), MAPSE 14±3 (p<0.05) and no LGE (p<0.05). While native T1 values were significantly higher in the DMD/BMD group compared to controls - 1028±44 versus 985±10 (p<0.05), ECV didn't differ statistically between groups – 0,24±0,03 versus 0,23±0,01 (p = NS). Conclusion: DMD/BMD patients had worse longitudinal and global LV systolic function, and had higher incidence of regional myocardial fibrosis. Native T1 values of LGE-free myocardium were significantly higher in muscular dystrophy patients. Acknowledgement/Funding: LQ1605 from the National Program of Sustainability II (MEYS CR)

008 Demonstration of cardiac AL amyloidosis regression after succesful chemotherapy. a CMR study

Background Cardiac involvement in immunoglobulin light chain (AL) amyloidosis is the major determinant of survival; Cardiac response to chemotherapy is conventionally assessed by serum brain natriuretic peptide (NT-proBNP) and echocardiography, but neither quantify amyloid burden. The aim of this study was to evaluate cardiac AL amyloid serially using cardiovascular MR (CMR) including extracellular volume measurement (ECV), which is the site of the amyloid deposits. Methods 31 patients with cardiac AL amyloidosis who had chemotherapy were studied serially using ECG, echocardiography, 123I-labelled serum amyloid P component (SAP) scintigraphy, NT-proBNP measurements and CMR with T1 mapping and ECV measurements (mean interval 20±11 months). Nineteen patients achieved a complete or very good partial haematological response (CR n=10; VGPR n=9). Twelve patients attained a partial response (PR) or no response (NR). Results At follow-up (mean 20±11 months), the amyloid burden had decreased substantially in 6 of the 10 (60%) attaining a CR, 6 of the 9 (67%) in VGPR and 1 of the 8 (13%) in PR. Changes in the ECV consistent with regression of amyloid were concordant with the changes in native T1, reduction in amyloid volume and in 5 patients with changes in late gadolinium enhancement pattern (figure 1). Overall there was significant reduction in NT-proBNP concentration, LV mass, left atrial area and improvement in diastolic function in patients whose amyloid burden decreased. Regression of cardiac amyloid by CMR correlated with regression of amyloid in other organs measured by SAP scintigraphy.

Comparison of ECV measurements during equilibrium between IR- and SR-based Cardiac T1Mapping

Background Cardiac T1 and extracellular volume fraction (ECV), derived from preand post-contrast cardiac and blood T1 measurements, are emerging imaging biomarkers of diffuse cardiac fibrosis. The most frequently used cardiac T1 mapping pulse sequence is MOLLI [1]. However, MOLLI is known to be sensitive to rapid heart rate and irregular rhythm, because it is based on inversion-recovery (IR) of magnetization preparation. In response, we developed an arrhythmia-insensitive-rapid (AIR) cardiac T1 mapping pulse sequence based on B1insensitive saturation-recovery (SR) of magnetization preparation [2]. Our prior study [2] showed that AIR (scan time = 2-3 heart beats) is faster and yields more accurate cardiac T1 measurements than MOLLI (scan time = 17 heart beats). We sought to compare ECV measurements between SR-based AIR and IR-based MOLLI cardiac T1 mapping at 3T.

Native T1 values in discrimination of subclinical profibrotic phenotype in relatives of patients with hypertrophic cardiomyopathy

Background Hypertrophic cardiomyopathy (HCM) is associated with significant associated morbidity and mortality. Increased maximal left ventricular wall thickness (LVWT) has been postulated as major risk factor of sudden death; however, relatives with normal LVWT are also at risk. Genetically driven interstitial collagenesis has been proposed as a possible mechanism of diffuse myocardial fibrosis and increased extracellular volume fractions (ECV) has been demonstrated in genotype positive subjects. We investigated whether native T1 can also separate genotype positive subjects in the absence of increase in LVWT and how does it relate to ECV measurements.

T1 Mapping for Myocardial Extracellular Volume Measurement by CMR: Bolus Only Versus Primed Infusion Technique

The aim of this study was to determine the accuracy of the contrast "bolus only" T1 mapping cardiac magnetic resonance (CMR) technique for measuring myocardial extracellular volume fraction (ECV).Myocardial ECV can be measured with T1 mapping before and after contrast agent if the contrast agent distribution between blood/myocardium is at equilibrium. Equilibrium distribution can be achieved with a primed contrast infusion (equilibrium contrast-CMR [EQ-CMR]) or might be approximated by the dynamic equilibration achieved by delayed post-bolus measurement. This bolus only approach is highly attractive, but currently limited data support its use. We compared the bolus only technique with 2 independent standards: collagen volume fraction (CVF) from myocardial biopsy in aortic stenosis (AS); and the infusion technique in 5 representative conditions.One hundred forty-seven subjects were studied: healthy volunteers (n = 50); hypertrophic cardiomyopathy (n = 25); severe AS (n = 22); amyloid (n = 20); and chronic myocardial infarction (n = 30). Bolus only (at 15 min) and infusion ECV measurements were performed and compared. In 18 subjects with severe AS the results were compared with histological CVF.The ECV by both techniques correlated with histological CVF (n = 18, r² = 0.69, p < 0.01 vs. r² = 0.71, p < 0.01, p = 0.42 for comparison). Across health and disease, there was strong correlation between the techniques (r² = 0.97). However, in diseases of high ECV (amyloid, hypertrophic cardiomyopathy late gadolinium enhancement, and infarction), Bland-Altman analysis indicates the bolus only technique has a consistent and increasing offset, giving a higher value for ECVs above 0.4 (mean difference ± limit of agreement for ECV <0.4 = -0.004 ± 0.037 vs. ECV >0.4 = 0.040 ± 0.075, p < 0.001).Bolus only, T1 mapping-derived ECV measurement is sufficient for ECV measurement across a range of cardiac diseases, and this approach is histologically validated in AS. However, when ECV is >0.4, the bolus only technique consistently measures ECV higher compared with infusion.

Comparison of OMVPE and MBE grown AlGaAs/InGaAs PHEMT structures

δ-doped PHEMT structures commercially grown by OMVPE and MBE on 3 inch wafers were examined using contactless resistance, magneto-Hall, PR, PL, DXRD, RBS, SIMS, and electrochemical capacitance-voltage measurements, and 0.1 μm gate length devices were fabricated from them and then characterized. The electron mobilities in the OMVPE 2DEG were a little smaller than those in the MBE 2DEG, but were still excellent, and the carrier concentrations, which were > 2.5 × 1012cm−2 at 77 K, were similar. The interface quality as measured by PR spectra was a little better in the MBE sample. Variation in the In areal density as determined by RBS was a little larger in the OMVPE wafer, but it was still less than 1 at%. The sheet resistance and the doping concentration as determined by SIMS and EC-V measurements showed the variation in the OMVPE wafers was slightly larger, but it was still considered to be small. PHEMTs fabricated from the most promising OMVPE wafer had gm's (753 mS/mm) that approached those for the MBE wafer (796 mS/mm) as did their fT's (115 versus 117 Ghz). The variations in these parameters were also found to be slightly larger in the OMVPE wafers.