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The variation of integrated backscatter in human hearts in differing ultrasonic transthoracic views
1Department of Cardiology, Western General Hospital, Edinburgh, Scotland, UK.
Insights
Integrated backscatter (IB) shows cyclic variation in all myocardial walls across parasternal and apical views. This finding expands the clinical utility of IB imaging systems for assessing cardiac function.
Area of Science:
- Cardiology
- Medical Imaging
- Biomedical Engineering
Background:
- Previous studies demonstrated cyclic variation of integrated backscatter (IB) in specific myocardial regions (interventricular septum, left ventricular posterior wall) using standard ultrasonic views (long-axis and short-axis).
- Limited views restricted the clinical application of IB imaging systems for assessing myocardial mechanics.
Purpose of the Study:
- To investigate the presence and characteristics of end-diastole (ED) to end-systole (ES) variation of IB in various myocardial regions using both parasternal and apical ultrasonic views.
- To determine if IB variation provides clinically useful information beyond standard views.
Main Methods:
- Utilized a radiofrequency acquisition technique to measure ED to ES variation of IB in 14 normal volunteers.
- Analyzed two-dimensional ultrasonic images from parasternal (long-axis, short-axis) and apical (two-chamber, four-chamber) views.
- Measured IB variation from manually traced regions of interest (ROIs) in multiple myocardial walls.
Main Results:
- ED to ES variation of IB was consistently found in all analyzed ROIs across both parasternal and apical views.
- Maximum IB values occurred at ES in the midseptum and anteroseptum (SAX views), midanterior wall (2C views), and midlateral wall (4C views) in a majority of volunteers.
- The remaining ROIs exhibited maximum IB cyclic variation at ED, confirming widespread presence of this phenomenon.
Conclusions:
- ED to ES variation of IB is present in all analyzed myocardial walls when imaged from both parasternal and apical views.
- This study confirms the presence of IB cyclic variation beyond standard views, enhancing its potential clinical utility.
- The timing of maximum and minimum IB values is not always coincident with end-diastole and end-systole, respectively, suggesting complex myocardial dynamics.
Abstract:
It has been shown previously that in normal subjects the interventricular septum imaged in the long-axis view (LAX) and the left ventricular posterior wall imaged in both the LAX and the short-axis view (SAX) exhibit cyclic variation of integrated backscatter (IB) throughout the cardiac cycle, with maximum values occurring at end diastole (ED) and minimum at end systole (ES). The ability to demonstrate this cyclic variation within these myocardial regions in only two ultrasonic views has limited the potential clinical utility of an IB imaging system. To determine whether clinically useful information on the variation of IB is available from different myocardial regions in different ultrasonic views, we measured ED to ES variation of IB from the parasternal and apical views in normal subjects with a radiofrequency acquisition technique. Two independent clinical observers analyzed ED to ES variation of IB from 14 normal volunteers (mean age 32 +/- 6 years; range 21 to 45 years) in reconstructed two-dimensional ultrasonic images obtained from the parasternal LAX and SAX and apical two-chamber (2C) and four-chamber (4C) views. ED to ES variation of IB was measured from manually traced regions of interest (ROI) within the myocardium. These ROIs were chosen interactively and were located within the midposterior wall and the midanteroseptum in LAX views; within the midposterior wall, midanteroseptum, midseptum, and midlateral wall in SAX views; within the midseptum and the midlateral wall in 4C views; and within the midinferior wall and the midanterior wall 2C views. In all analyzed ROIs within the parasternal and apical views, ED to ES variation of IB was found. We have shown that the maximum magnitude of IB was at ES within the midseptum and in 10 out of 14 volunteers in the midanteroseptum measured from SAX views, the midanterior wall from 2C views, and the midlateral wall from 4C views. The rest of the ROIs analyzed exhibited the maximum value of IB cyclic variation at ED. We have confirmed that the ED to ES variation of IB is present not only when measured from the two standard parasternal views but also from the two apical views in all analyzed myocardial walls, and the minimum of this cyclic variation was not always coincident with ES nor the maximum with ED.