The current work investigates the performance of a real-time scan conversion algorithm for generating a 2-D ultrasound image from a laterally scanned single-element ultrasound transducer, which has applications in point-of-care devices such as for skin imaging. The algorithm employs a fixed calibration curve to update a predefined image grid in real time. Simulations showed that the calibration curve (with a maximum of 1) is robust to changes in scatterer concentration (8.3×10-3 mean absolute error), signal to noise ratio (1.0×10-3 mean absolute error for -5 dB SNR), and can be accurately predicted from a small number (31) of point scatterers (6.9×10-3 mean absolute error). Good agreement was also found between the calibration curves obtained from simulated and experimental data (1.19×10-2 mean absolute error). The scan conversion algorithm was validated by evaluation of the position estimation errors on both simulations and experiments. Clinical images of skin lesions (N = 20) demonstrate the feasibility of the algorithm for real, non-homogeneous tissue. Use of a fixed calibration curve compared to an adaptive calibration curve gave similar accuracies in the scanning step size range of 150-350 μm (with an average overlap of the accuracy ranges of 92.94% for simulations and 42.83% for experiments), and a 350-fold improvement in computation time.
Keywords: Correlation; Freehand scanning; Image formation; Scan conversion; Single-element transducer.
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