Image‐based coronary tracking and beat‐to‐beat motion compensation: Feasibility for improving coronary MR angiography

A method to reduce the effect of motion variability in MRI of the coronary arteries is proposed. It involves acquiring real‐time low‐resolution images in specific orthogonal orientations, extracting coronary motion from these images, and then using this motion information to guide high‐resolution MR image acquisition on a beat‐to‐beat basis. The present study establishes the feasibility and efficacy of the proposed approach using human motion data in an offline implementation, prior to future online implementation on an MRI scanner. To track the coronary arteries in low‐resolution real‐time MR images in an accurate manner, a tracking approach is presented and validated. The tracking algorithm was run on real‐time images acquired at 15–20 frames per second in four‐chamber, short‐axis, and coronal views in five volunteers. The systolic and diastolic periods in the cardiac cycles, computed from the extracted motion information, had significant variability during the short time periods typical of cardiac MRI. It is also demonstrated through simulation analysis using human tracked coronary motion data that accounting for this cardiac variability by adaptively changing the trigger delay for acquisition on a beat‐to‐beat basis improves overall motion compensation and hence MR image quality evaluated in terms of SNR and CNR values. Magn Reson Med 60:604–615, 2008. © 2008 Wiley‐Liss, Inc.     

Effects of diltiazem on recurrent myocardial infarction in patients with non-Q wave myocardial infarction.

Diltiazem has been reported to reduce the short-term in-hospital reinfarction rate in patients with a non-Q wave myocardial infarction. In the long-term Multicenter Diltiazem Postinfarction Trial, there were 514 patients with non-Q wave myocardial infarction; 279 patients were randomized to the placebo group and 235 to the treatment group. The average follow-up period was 25 months. There was no difference in baseline clinical characteristics between the two groups. Early reinfarction (less than or equal to 6 months) occurred in 17 patients in the placebo group and in 2 patients in the diltiazem group (p less than 0.001). Late reinfarction (greater than 6 months) occurred in 13 patients in the placebo group and in 14 patients in the diltiazem group (p = NS). Initial and reinfarction electrocardiograms (ECGs) were analyzed by using a coding system that permitted identification of standard anatomic areas involved in the infarction process. Thirty-one of the 46 patients had a localized infarction on index and reinfarction ECGs. In the early reinfarction group, 10 (77%) of 13 infarctions occurred in the same ECG region in which the initial infarction had occurred; all 10 were in patients in the placebo group. Among the 18 patients with late reinfarction, the site of the second infarction was the same as that of the first in 9 patients and differed in 9. There was no difference between the placebo and diltiazem groups with respect to location of the infarction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aerobic fitness, blood lipids, and body fat in children.

This study examined the association between aerobic fitness and serum cholesterol and the effects of controlling for gender, body composition, abdominal fat, and dietary saturated fat in 262 children. The 1-mile run was used to estimate fitness. Skinfolds were used in assessing body fat. Fit children had lower total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels and higher high-density lipoprotein cholesterol levels than unfit children, except after adjustment for body fat and/or abdominal fat. Unfit children appear to be at an increased risk of unhealthy levels of serum cholesterol due primarily to increased levels of body fat.     

The effects of an intensive lifestyle modification program on carotid artery intima-media thickness: a randomized trial

PURPOSE: This study evaluated the effect of the Dr. Dean Ornish Program for Reversing Heart Disease on cardiovascular disease as measured by the intima-media thickness of the common carotid artery and compared this effect to outcomes from patients participating in traditional cardiac rehabilitation. DESIGN: Randomized clinical trial. SETTING: Swedish American Health System. SUBJECTS: Ninety three patients with clinically confirmed coronary artery disease were randomly assigned to the intervention (n = 46) or traditional cardiac rehabilitation (n = 47). INTERVENTION: Dr. Dean Ornish Program for Reversing Heart Disease. MEASURES: Ultrasound of the carotid artery and other cardiovascular risk factors were measured at baseline, 6, and 12 months. ANALYSIS: Intent-to-treat analysis. RESULTS: There was no significant reduction in the carotid intima-media thickness of the carotid artery in the Ornish group or the cardiac rehabilitation group. Ornish Program participants had significantly improved dietary habits (p < .001), weight (p < .001), and body mass index (p < .001) as compared with the rehabilitation group. The decrease in the number of patients with angina from baseline to 12 months was 44% in Ornish and 12% in cardiac rehabilitation. CONCLUSIONS: The Ornish Program appears to causes improvements in cardiovascular risk factors but does not appear to change the atherosclerotic process as it affects the carotid artery.     

Query-by-example surgical activity detection

Purpose

Easy acquisition of surgical data opens many opportunities to automate skill evaluation and teaching. Current technology to search tool motion data for surgical activity segments of interest is limited by the need for manual pre-processing, which can be prohibitive at scale. We developed a content-based information retrieval method, query-by-example (QBE), to automatically detect activity segments within surgical data recordings of long duration that match a query.

Methods

The example segment of interest (query) and the surgical data recording (target trial) are time series of kinematics. Our approach includes an unsupervised feature learning module using a stacked denoising autoencoder (SDAE), two scoring modules based on asymmetric subsequence dynamic time warping (AS-DTW) and template matching, respectively, and a detection module. A distance matrix of the query against the trial is computed using the SDAE features, followed by AS-DTW combined with template scoring, to generate a ranked list of candidate subsequences (substrings). To evaluate the quality of the ranked list against the ground-truth, thresholding conventional DTW distances and bipartite matching are applied. We computed the recall, precision, F1-score, and a Jaccard index-based score on three experimental setups. We evaluated our QBE method using a suture throw maneuver as the query, on two tool motion datasets (JIGSAWS and MISTIC-SL) captured in a training laboratory.

Results

We observed a recall of 93, 90 and 87 % and a precision of 93, 91, and 88 % with same surgeon same trial (SSST), same surgeon different trial (SSDT) and different surgeon (DS) experiment setups on JIGSAWS, and a recall of 87, 81 and 75 % and a precision of 72, 61, and 53 % with SSST, SSDT and DS experiment setups on MISTIC-SL, respectively.

Conclusion

We developed a novel, content-based information retrieval method to automatically detect multiple instances of an activity within long surgical recordings. Our method demonstrated adequate recall across different complexity datasets and experimental conditions.

     

Effect of the ouabain-quinidine interaction on left ventricular and left atrial function in conscious dogs

The effect of the ouabain-quinidine interaction was examined in 10 conscious dogs. Left ventricular (LV) pressure, LV dP/dt, LV diameter and left atrial (LA) diameter were measured with high-fidelity micromanometers and sonomicrometer crystals. Ouabain, 0.025 mg/kg, significantly (p less than 0.05) increased LV dP/dt, LV and LA fractional shortening and LV and LA velocity of circumferential fiber shortening (Vcf). In a separate experiment, quinidine was administered as a bolus dose, 3.85 mg/kg, followed by an infusion, 0.28 mg/kg/min. This resulted in steady-state quinidine concentrations that produced no change in wall motion or hemodynamics. When ouabain was given 1 hour into the quinidine infusion, only LV dP/dt increased significantly (p less than 0.05). Ouabain alone increased LV dP/dt 26.4 +/- 3.5%, whereas ouabain during the quinidine infusion increased it by 9.5 +/- 2.3%. Similar differences were seen in the responses to ouabain in the absence and presence of quinidine: LV Vcf, 22.4 +/- 4.9% vs 6.0 +/- 2.1%, LV fractional shortening, 23.1 +/- 4.6% vs 5.8 +/- 2.1%, LA Vcf, 22.7 +/- 5.9 vs 4.6 +/- 2.0% and LA fractional shortening, 21.8 +/- 7% vs 7.8 +/- 3.3%. Thus, in the presence of quinidine the increase in intropy usually seen with ouabain was markedly attenuated. These data suggest that the quinidine-induced increase in digoxin serum concentrations is accompanied by a decrease in the contractile response of the heart to digoxin.