“…The development of this transducer and guidewire has been described previously. 30 The center frequency of the transducer was 16 MHz with a −6 dB fractional bandwidth of 49%. The fabricated device was held by a motion stage (Newport XPS, Irvine, CA, USA), allowing rapid and precise mechanical steering of the transducer.…”
Section: Imaging Systemmentioning
confidence: 99%
“…By forming images using a synthetic aperture approach, the size of the effective aperture is increased, which can increase SNR and lateral resolution. 74 Correlated signals are included in the beamsum based on a previously developed approach in which scanlines located within a specified distance of the focal point in the region of interest (ROI) are summed 30 (Figure 1). Each pixel value is computed (1) according to focal delays (τ) according to (2):…”
Section: Imaging Systemmentioning
confidence: 99%
“…However, including decorrelated scanlines in the beamsum reduces contrast and SNR. 30 The effect of aperture size on classifier performance was studied in simulations.…”
“…[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] We have recently developed a 0.89 mm (0.035′′) robotically-steerable guidewire with a single forward-viewing ultrasound transducer to allow direct visualization of occlusions and tortuous anatomy during minimally-invasive revascularization. 30,31 The developed system forms images while mechanically translating the aperture via a synthetic aperture approach, which allows extension of the aperture beyond the 0.89 mm diameter of the guidewire. 32,33 This approach can improve spatial resolution for visualizing the remaining path through occlusions, which can be < 1 mm.…”
Section: Introductionmentioning
confidence: 99%
“…Recently, several research groups have proposed to improve interventional guidance across a variety of procedures by integrating imaging into catheters and guidewires to provide direct visualization from inside the artery 14–29 . We have recently developed a 0.89 mm (0.035′′) robotically‐steerable guidewire with a single forward‐viewing ultrasound transducer to allow direct visualization of occlusions and tortuous anatomy during minimally‐invasive revascularization 30,31 . The developed system forms images while mechanically translating the aperture via a synthetic aperture approach, which allows extension of the aperture beyond the 0.89 mm diameter of the guidewire 32,33 .…”
Background
Approximately 500 000 patients present with critical limb ischemia (CLI) each year in the U.S., requiring revascularization to avoid amputation. While peripheral arteries can be revascularized via minimally invasive procedures, 25% of cases with chronic total occlusions are unsuccessful due to inability to route the guidewire beyond the proximal occlusion. Improvements to guidewire navigation would lead to limb salvage in a greater number of patients.
Purpose
Integrating ultrasound imaging into the guidewire could enable direct visualization of routes for guidewire advancement. In order to navigate a robotically‐steerable guidewire with integrated imaging beyond a chronic occlusion proximal to the symptomatic lesion for revascularization, acquired ultrasound images must be segmented to visualize the path for guidewire advancement.
Methods
The first approach for automated segmentation of viable paths through occlusions in peripheral arteries is demonstrated in simulations and experimentally‐acquired data with a forward‐viewing, robotically‐steered guidewire imaging system. B‐mode ultrasound images formed via synthetic aperture focusing (SAF) were segmented using a supervised approach (U‐net architecture). A total of 2500 simulated images were used to train the classifier to distinguish the vessel wall and occlusion from viable paths for guidewire advancement. First, the size of the synthetic aperture resulting in the highest classification performance was determined in simulations (90 test images) and compared with traditional classifiers (global thresholding, local adaptive thresholding, and hierarchical classification). Next, classification performance as a function of the diameter of the remaining lumen (0.5 to 1.5 mm) in the partially‐occluded artery was tested using both simulated (60 test images at each of 7 diameters) and experimental data sets. Experimental test data sets were acquired in four 3D‐printed phantoms from human anatomy and six ex vivo porcine arteries. Accuracy of classifying the path through the artery was evaluated using microcomputed tomography of phantoms and ex vivo arteries as a ground truth for comparison.
Results
An aperture size of 3.8 mm resulted in the best‐performing classification based on sensitivity and Jaccard index, with a significant increase in Jaccard index (p < 0.05) as aperture diameter increased. In comparing the performance of the supervised classifier and traditional classification strategies with simulated test data, sensitivity and F1 score for U‐net were 0.95 ± 0.02 and 0.96 ± 0.01, respectively, compared to 0.83 ± 0.03 and 0.41 ± 0.13 for the best‐performing conventional approach, hierarchical classification. In simulated test images, sensitivity (p < 0.05) and Jaccard index both increased with increasing artery diameter (p < 0.05). Classification of images acquired in artery phantoms with remaining lumen diameters ≥ 0.75 mm resulted in accuracies > 90%, while mean accuracy decreased to 82% when artery diameter decreased to 0.5 mm. For testing i...
“…The development of this transducer and guidewire has been described previously. 30 The center frequency of the transducer was 16 MHz with a −6 dB fractional bandwidth of 49%. The fabricated device was held by a motion stage (Newport XPS, Irvine, CA, USA), allowing rapid and precise mechanical steering of the transducer.…”
Section: Imaging Systemmentioning
confidence: 99%
“…By forming images using a synthetic aperture approach, the size of the effective aperture is increased, which can increase SNR and lateral resolution. 74 Correlated signals are included in the beamsum based on a previously developed approach in which scanlines located within a specified distance of the focal point in the region of interest (ROI) are summed 30 (Figure 1). Each pixel value is computed (1) according to focal delays (τ) according to (2):…”
Section: Imaging Systemmentioning
confidence: 99%
“…However, including decorrelated scanlines in the beamsum reduces contrast and SNR. 30 The effect of aperture size on classifier performance was studied in simulations.…”
“…[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] We have recently developed a 0.89 mm (0.035′′) robotically-steerable guidewire with a single forward-viewing ultrasound transducer to allow direct visualization of occlusions and tortuous anatomy during minimally-invasive revascularization. 30,31 The developed system forms images while mechanically translating the aperture via a synthetic aperture approach, which allows extension of the aperture beyond the 0.89 mm diameter of the guidewire. 32,33 This approach can improve spatial resolution for visualizing the remaining path through occlusions, which can be < 1 mm.…”
Section: Introductionmentioning
confidence: 99%
“…Recently, several research groups have proposed to improve interventional guidance across a variety of procedures by integrating imaging into catheters and guidewires to provide direct visualization from inside the artery 14–29 . We have recently developed a 0.89 mm (0.035′′) robotically‐steerable guidewire with a single forward‐viewing ultrasound transducer to allow direct visualization of occlusions and tortuous anatomy during minimally‐invasive revascularization 30,31 . The developed system forms images while mechanically translating the aperture via a synthetic aperture approach, which allows extension of the aperture beyond the 0.89 mm diameter of the guidewire 32,33 .…”
Background
Approximately 500 000 patients present with critical limb ischemia (CLI) each year in the U.S., requiring revascularization to avoid amputation. While peripheral arteries can be revascularized via minimally invasive procedures, 25% of cases with chronic total occlusions are unsuccessful due to inability to route the guidewire beyond the proximal occlusion. Improvements to guidewire navigation would lead to limb salvage in a greater number of patients.
Purpose
Integrating ultrasound imaging into the guidewire could enable direct visualization of routes for guidewire advancement. In order to navigate a robotically‐steerable guidewire with integrated imaging beyond a chronic occlusion proximal to the symptomatic lesion for revascularization, acquired ultrasound images must be segmented to visualize the path for guidewire advancement.
Methods
The first approach for automated segmentation of viable paths through occlusions in peripheral arteries is demonstrated in simulations and experimentally‐acquired data with a forward‐viewing, robotically‐steered guidewire imaging system. B‐mode ultrasound images formed via synthetic aperture focusing (SAF) were segmented using a supervised approach (U‐net architecture). A total of 2500 simulated images were used to train the classifier to distinguish the vessel wall and occlusion from viable paths for guidewire advancement. First, the size of the synthetic aperture resulting in the highest classification performance was determined in simulations (90 test images) and compared with traditional classifiers (global thresholding, local adaptive thresholding, and hierarchical classification). Next, classification performance as a function of the diameter of the remaining lumen (0.5 to 1.5 mm) in the partially‐occluded artery was tested using both simulated (60 test images at each of 7 diameters) and experimental data sets. Experimental test data sets were acquired in four 3D‐printed phantoms from human anatomy and six ex vivo porcine arteries. Accuracy of classifying the path through the artery was evaluated using microcomputed tomography of phantoms and ex vivo arteries as a ground truth for comparison.
Results
An aperture size of 3.8 mm resulted in the best‐performing classification based on sensitivity and Jaccard index, with a significant increase in Jaccard index (p < 0.05) as aperture diameter increased. In comparing the performance of the supervised classifier and traditional classification strategies with simulated test data, sensitivity and F1 score for U‐net were 0.95 ± 0.02 and 0.96 ± 0.01, respectively, compared to 0.83 ± 0.03 and 0.41 ± 0.13 for the best‐performing conventional approach, hierarchical classification. In simulated test images, sensitivity (p < 0.05) and Jaccard index both increased with increasing artery diameter (p < 0.05). Classification of images acquired in artery phantoms with remaining lumen diameters ≥ 0.75 mm resulted in accuracies > 90%, while mean accuracy decreased to 82% when artery diameter decreased to 0.5 mm. For testing i...
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