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Jan D'hooge

Publications and source records attributed to Jan D'hooge.

15 recordsLinked to original sources
PubMed2003

Identification of acutely ischemic myocardium using ultrasonic strain measurements. A clinical study in patients undergoing coronary angioplasty.

OBJECTIVES: The goal of this study was to investigate whether the changes in myocardial deformation measured with ultrasonic strain could accurately identify acutely ischemic myocardium during coronary angioplasty. BACKGROUND: Early identification of acute myocardial ischemia has important clinical implications. The accuracy of ultrasonic strain for the detection of acute myocardial ischemia has been validated in animal experiments but has not been investigated in the clinical setting. METHODS: In 73 patients (64 +/- 12 years), either radial or longitudinal strain values were monitored in the "at-risk" segments before, during, and early after right, circumflex, and left anterior descending coronary angioplasty. Based on the visual wall motion assessed before the angioplasty, segments were divided into normokinetic (group I) and hypo/akinetic (group II). Strain data in the "at-risk " segments were compared with values derived from the adjacent nonischemic segments and normal values in 20 controls. RESULTS: Coronary occlusion induced a marked reduction in the systolic strain both in the radial (from 49 +/- 6.9% to 23 +/- 4.6% in group I and from 21.9 +/- 11% to 11.3 +/- 8.4% in group II, p < 0.001) and longitudinal directions. Concomitantly, postsystolic strain increased (from 3.8 +/- 3.1% to 14.6 +/- 9.5% in group I, and from 4.4 +/- 3.7% to 11.3 +/- 7.8% in group II in radial direction, p < 0.001). Upon reperfusion, all deformation parameters returned to near preocclusion values. In comparison with control, baseline, and reperfusion data, the systolic and postsystolic strain parameters measured during total coronary occlusion identified acutely ischemic myocardium with a sensitivity of 86% to 95% and a specificity of 83% to 89%. CONCLUSIONS: In this model of acute ischemia, ultrasonic strain indexes differentiate acutely ischemic segments from both normal and dysfunctional myocardium. This should be a promising new approach to the bedside monitoring of acute ischemic changes in regional myocardial function.

Acute Disease↗
PubMed2003

Defining the transmurality of a chronic myocardial infarction by ultrasonic strain-rate imaging: implications for identifying intramural viability: an experimental study.

BACKGROUND: In a correlative functional/histopathologic study, we investigated the regional deformation characteristics of both chronic nontransmural and transmural infarctions before and after a dobutamine challenge. METHODS AND RESULTS: After stenosing copper-coated stent implantation to produce circumflex artery endothelial proliferation, 18 pigs were followed up for 5 weeks. Posteuthanasia histology showed 10 to have a nontransmural and 8 a transmural infarction. Eight nonstented animals served as controls. Regional radial function was monitored by measuring ultrasound-derived peak systolic strain rates (SR(SYS)) and systolic strains (epsilon(SYS)) (1) before stent implantation and (2) at 5 weeks, at baseline (bs) and during an incremental dobutamine infusion. In controls, dobutamine induced a linear increase in SR(SYS) (dobutamine: bs, 4.8+/-0.4 s(-1); 20 microg x kg(-1) x min(-1), 9.9+/-0.7 s(-1); P<0.0001) and an initial increase of epsilon(SYS) at low dose (bs, 58+/-5%; at 5 microg x kg(-1) x min(-1), 78+/-6%; P<0.05) but a subsequent decrease during higher infusion rates. In the nontransmural group, bs SR(SYS) and epsilon(SYS) were significantly lower than prestent values (SR(SYS), 2.9+/-0.5 s(-1) and epsilon(SYS), 32+/-6%, P<0.05 versus prestent). During dobutamine infusion, SR(SYS) increased slightly at 5 microg x kg(-1) x min(-1) (4.7+/-0.6 s(-1), P<0.05) but fell during higher infusion rates, whereas epsilon(SYS) showed no change. For nontransmural infarctions, transmural scar extension correlated closely with epsilon(SYS) at bs (r=0.88). For transmural infarctions, SR(SYS) at bs was significantly reduced and epsilon(SYS) was almost not measurable (SR(SYS), 1.8+/-0.3 s(-1); epsilon(SYS), 3+/-4%). Both deformation parameters showed no further change during the incremental dobutamine infusion. CONCLUSIONS: Ultrasonic deformation values could clearly differentiate chronic nontransmural from transmural myocardial infarction. The transmural extension of the scar could be defined by the regional deformation response.

Animals↗
PubMed2003

One-dimensional ultrasonic strain and strain rate imaging: a new approach to the quantitation of regional myocardial function in patients with aortic stenosis.

Abnormalities in regional left ventricular (LV) function in aortic stenosis (AS) have yet to be appropriately characterized. One-dimensional strain (epsilon) and strain rate imaging (SRI), new ultrasound (US) indices for quantifying regional wall deformation, might allow this. The aims of this study were 1. to define regional radial and longitudinal epsilon /SR in AS; 2. to establish if they are related to the severity of the disease; and 3. to determine if regional deformation is further altered by coexistent coronary artery disease (CAD). A total of 40 patients were studied: Group I with isolated AS (10 women, 10 men; mean age 66 years) and group II with AS and concomitant CAD (CAD/AS) (13 women, 7 men, mean age 68 years). Data were compared to 20 age-matched healthy people (N). Regional systolic maximal velocity/SR and end-systolic and maximal epsilon were measured. The maximal systolic velocity/SR in AS and CAD/AS patients were significantly reduced compared to N. The two patient groups could be further differentiated by end-systolic and maximal epsilon, which demonstrated a further reduction in both epsilon indices in CAD/AS (i.e., maximal radial epsilon 29.3%, AS; 23.7%, CAD/AS; 40.4%, N; AS and CAD/AS vs. N, AS vs. CAD/AS, p < 0.05). Indices of radial and longitudinal deformation correlated both with aortic valve area (AVA) and stroke volume (SV) (i.e., radial maximal epsilon and AVA, r = 0.77, p < 0.05). A significant correlation was also found between epsilon indices and the severity of left anterior descending (LAD) or circumflex artery (CX) coronary artery. Regional myocardial deformation in AS is abnormal. In the absence of CAD, the degree of abnormality correlates with aortic valve area (AVA). The severity of the disease was best expressed by changes in regional epsilon. In CAD/AS patients, there was a significant further reduction in end-systolic and maximal epsilon. These changes correlated with the severity of coronary narrowing in the subtending vessel.

Adult↗
PubMed2003

Can regional strain and strain rate measurement be performed during both dobutamine and exercise echocardiography, and do regional deformation responses differ with different forms of stress testing?

BACKGROUND: Regional strain (epsilon) and strain rate (SR) measurement could be the optimal approach to quantifying stress echocardiography images. However, signal noise could preclude their use. Study aims Our aim was to compare the feasibility of regional peak systolic (p) velocity (Vel), pSR/epsilon measurement, and their normal responses during upright (group 1, n = 10) and supine (group 2, n = 10) bicycle exercise and (group 3, n = 10) dobutamine stress. METHODS: For each type of stress study, pVel/pSR/epsilon data were acquired at baseline, low (100-120 bpm), and peak (140-160 bpm) heart rate (HR); and during recovery. RESULTS: During dobutamine pVel/pSR/epsilon were interpretable in >95% of segments at every stress stage, whereas in groups 1 and 2 pSR/epsilon responses were noninterpretable in >36% of segments (P <.0002). The highest proportions of data exclusions were from the lateral and anterior walls. In all groups, regional systolic pVel and SR values increased linearly and reached maximal value at peak HR (P <.0006 vs baseline). Pepsilon showed a biphasic response, initially increasing at low HR, and then remaining constant or falling at peak HR. CONCLUSION: PSR/pepsilon quantification of stress echocardiography may currently be restricted to dobutamine as increased signal noise precludes adequate data acquisition during exercise. For all forms of stress both pSR and pVel increased linearly, whereas pepsilon response was biphasic as a result of the reduced filling at higher HRs.

Adult↗
PubMed2003

Towards ultrasound cardiac image segmentation based on the radiofrequency signal.

In echocardiography, the radio-frequency (RF) image is a rich source of information about the investigated tissues. Nevertheless, very few works are dedicated to boundary detection based on the RF image, as opposed to envelope image. In this paper, we investigate the feasibility and limitations of boundary detection in echocardiographic images based on the RF signal. We introduce two types of RF-derived parameters: spectral autoregressive parameters and velocity-based parameters, and we propose a discontinuity adaptive framework to perform the detection task. In classical echographic cardiac acquisitions, we show that it is possible to use the spectral contents for boundary detection, and that improvement can be expected with respect to traditional methods. Using the system approach, we study on simulations how the spectral contents can be used for boundary detection. We subsequently perform boundary detection in high frame rate simulated and in vivo cardiac sequences using the variance of velocity, obtaining very promising results. Our work opens the perspective of a RF-based framework for ultrasound cardiac image segmentation and tracking.

Algorithms↗
PubMed2002

Myocardial elastography--a feasibility study in vivo.

Early detection of cardiovascular diseases has been a very active research area in the medical imaging field. Assessment of the local and global mechanical functions is one of the major goals of accurate diagnosis. In this study, we investigated the feasibility of elastography for estimation and imaging of the local cardiac muscle displacement and strain in a human heart in vivo. In its noninvasive applications, elastography has been typically used to determine local tissue strain through the use of externally applied compression. For our study, we utilized the cardiac muscle motion during a cardiac cycle as the mechanical stimulus, and acquired successive radiofrequency (RF) data frames of the septal and posterior walls over a few cardiac cycles in parasternal and apical views, respectively. High-quality ciné-loop elastograms were obtained due to high frame rates and the resulting low decorrelation noise. Furthermore, the strain contrast was higher in the parasternal case, when only the posterior wall was imaged, and strain estimation was more robust in the apical view. High repeatability of the results was observed through elastographic measurements over several cardiac cycles. Finally, an M-mode version of elastography was used to follow part of the interventricular septum or the posterior wall over the course of two cardiac cycles. Not only do these preliminary results show that elastography is feasible in cardiac applications in vivo, but also that it can provide new information regarding cardiac motion and mechanical function. Future prospects include assessment of the role of elastography in detection of ischemia and infarction.

Adult↗
PubMed2002

Can changes in systolic longitudinal deformation quantify regional myocardial function after an acute infarction? An ultrasonic strain rate and strain study.

OBJECTIVES: The aim of this study was to evaluate the additional value of ultrasonic strain rate and strain to myocardial velocity in the identification and quantification of regional asynergy after an acute myocardial infarction (MI). METHODS: Forty patients (59 +/- 13 years) were investigated 3 +/- 2 days after a first infarction and compared with 14 age-matched controls with normally contracting segments (group A, n = 146). Longitudinal myocardial velocities, strain rate (SR) and strain (epsilon) were postprocessed from basal, mid, and apical segments interrogated using apical views. In a subset of patients with coronary angiograms (n = 24), myocardial segments were divided into 3 groups: normally contracting segments supplied by a normal coronary artery (group B1), normally contracting segments supplied by a diseased coronary artery (group B2), and segments with abnormal motion (group B3). Velocities were decreased in patients with myocardial infarction (MI) (P <.05 vs controls) but failed to accurately differentiate normally from abnormally contracting segments. At the opposite end, systolic SR and epsilon decreased significantly with segmental asynergy severity and could identify infarct-involved segments (group B3) with a sensitivity/specificity of 85% (systolic SR and epsilon cutoff values of -0.8 s(-1) and -13%, respectively). CONCLUSION: Strain rate and strain can better assess segmental dysfunction severity than myocardial velocities alone after an acute MI.

Aged↗
PubMed2002

Doppler tissue velocity, strain, and strain rate imaging with transesophageal echocardiography in the operating room: a feasibility study.

OBJECTIVE: Transesophageal echocardiography (TEE) is increasingly used to monitor regional myocardial function during cardiac operation. Doppler myocardial imaging (DMI) indices can potentially provide new information on regional radial and longitudinal myocardial motion and local deformation. This study examined the feasibility of TEE acquisition of regional radial and longitudinal velocity, displacement (D), strain, and strain rate data during cardiac operation and evaluated the effects of sternotomy and pericardial opening on these indices. METHODS: After a baseline transthoracic echocardiographic study, TEE was performed in 22 patients (age 64 +/- 7 years) before sternotomy, after sternotomy with intact pericardium, and after pericardial opening. Regional DMI velocity analysis was performed for the transgastric anterior and inferior walls midpapillary segment (radial function) and the 4-chamber septum and 2-chamber inferior walls basal, mid, and apical segments (longitudinal function). For each segment, systolic and diastolic velocity were derived and D, strain, and strain rate calculated. RESULTS: Transthoracic echocardiographic study and TEE provided similar data from an equivalent number of interpretable segments. In the basal and mid septum, maximum longitudinal systolic D decreased with pericardial opening (basal septum pericardium closed: 6.6 +/- 1.5 mm, open: 4.6 +/- 1.8 mm, P =.007; midseptum pericardium closed: 4.7 +/- 2.5 mm, open: 2.7 +/- 1.5 mm, P =.028). No changes were evident in systolic or diastolic DMI indices in all other segments. CONCLUSION: DMI with TEE is feasible during cardiac operation. During pericardial opening, longitudinal D decreases in the septum, but not in the inferior wall. DMI requires further evaluation in the assessment of ventricular function and the detection of ischemia in the operating room.

Aged↗
PubMed2002

Two-dimensional ultrasonic strain rate measurement of the human heart in vivo.

A study is presented in which the feasibility of two-dimensional strain rate estimation of the human heart in vivo has been demonstrated. To do this, ultrasonic B-mode data were captured at a high temporal resolution of 3.8 ms and processed off-line. The motion of the RF signal patterns within the two-dimensional sector image was tracked and used as the basis for strain rate estimation. Both axial and lateral motion and strain rate estimates showed a good agreement with the results obtained by more established, one-dimensional techniques.

Adult↗
PubMed2002

Echocardiographic strain and strain-rate imaging: a new tool to study regional myocardial function.

Ultrasonic imaging is the noninvasive clinical imaging modality of choice for diagnosing heart disease. At present, two-dimensional ultrasonic grayscale images provide a relatively cheap, fast, bedside method to study the morphology of the heart. Several methods have been proposed to assess myocardial function. These have been based on either grayscale or motion (velocity) information measured in real-time. However, the quantitative assessment of regional myocardial function remains an important goal in clinical cardiology. To do this, ultrasonic strain and strain-rate imaging have been introduced. In the clinical setting, these techniques currently only allow one component of the true three-dimensional deformation to be measured. Clinical, multidimensional strain (rate) information can currently thus only be obtained by combining data acquired using different transducer positions. Nevertheless, given the appropriate postprocessing, the clinical value of these techniques has already been shown. Moreover, multidimensional strain and strain-rate estimation of the heart in vivo by means of a single ultrasound acquisition has been shown to be feasible. In this paper, the new techniques of ultrasonic strain rate and strain imaging of the heart are reviewed in terms of definitions, data acquisition, strain-rate estimation, postprocessing, and parameter extraction. Their clinical validation and relevance will be discussed using clinical examples on relevant cardiac pathology. Based on these examples, suggestions are made for future developments of these techniques.

Echocardiography↗
PubMed2002

Processing radio frequency ultrasound images: a robust method for local spectral features estimation by a spatially constrained parametric approach.

Spectral estimation is a major component in studies aiming at characterizing biological tissues through the analysis of backscattered radio frequency (RF) ultrasonic signals and images. However, conventional spectral estimation techniques yield a well-known trade-off between spatial resolution and variance. The backscattered signals are stochastic by nature, so short-term local analysis results in a high variance of the estimates, which cannot efficiently be reduced through conventional spatial averaging. We address this issue by describing a spectral estimation technique that reduces the variance of the estimates (by smoothing the local estimates in spectrally homogeneous regions) while preserving spectral discontinuities (i.e., the smoothing is not performed across regions with different spectral contents). The proposed approach is set in a Bayesian framework and is based on local autoregressive (AR) estimation, constrained by smoothness priors. These smoothness priors are introduced through a Markov random field in which the associated potential functions are nonquadratic, allowing thereby to preserve discontinuity. The method is validated on simulated RF images and tested on echocardiographic images acquired in vivo. The results are compared to the estimates provided by the conventional Burg technique. These results clearly demonstrate the ability of the proposed approach to improve spectral estimation in terms of variance reduction and discontinuity detection.

Algorithms↗
PubMed1999

Tissue Doppler Echocardiography: Future Developments.

The use of color-coded tissue Doppler echocardiography has resulted in rapid technological advances in the evaluation of cardiac function. This article describes some of these exciting new advances, including curved M-mode analysis and strain rate imaging. Data from studies in animals and humans are presented to demonstrate the potential clinical use of this new echocardiographic diagnostic tool.

Journal Article↗