Multilateration-based needle tracking with 3D ultrasound imaging for guiding minimally invasive procedures

Image-guided focal ablation procedures are first-line therapy options in the treatment of liver cancer tumors that provide advantageous reductions in patient recovery times and complication rates relative to open surgery. However, extensive physician training is required and image guidance variabilities during freehand therapy applicator placement limit the sufficiency of ablation volumes and the overall potential of these procedures. We propose the use of three-dimensional ultrasound (3D US) to provide guidance and localization of therapy applicators, augmenting current ablation therapies without the need for specialized procedure suites. We have developed a novel scanning mechanism for geometrically variable 3D US images, a mechanical tracking system, and a needle applicator insertion workflow using a custom needle applicator guide for targeted image-guided procedures. A three-motor scanner was designed to use any commercially available US probe to generate accurate, consistent, and geometrically variable 3D US images. The designed scanner was mounted on a counterbalanced stabilizing and mechanical tracking system for determining the US probe orientation, which was assessed using optical tracking. Further exploiting the utility of the motorized scanner, an image-guidance workflow was developed that moved the probe to any identified target within an acquired 3D US image. The complete 3D US guidance system was used to perform mock targeted interventional procedures on a phantom by selecting a target in a 3D US image, navigating to the target, and performing needle insertion using a custom 3D-printed needle applicator guide. Registered postinsertion 3D US images and cone-beam computed tomography (CBCT) images were used to evaluate tip targeting errors when using the motors, tracking system, or mixed navigation approaches. Two 3D US image geometries were investigated to assess the accuracy of a small-footprint tilt approach and a large field-of-view hybrid approach for a total of 48 targeted needle insertions. 3D US image quality was evaluated in a healthy volunteer and compared to a commercially available matrix array US probe. A mean positioning error of 1.85±1.33mm was observed when performing compound joint manipulations with the mechanical tracking system. A combined approach for navigation that incorporated the motorized movement and the in-plane tracking system corrections performed the best with a mean tip error of 3.77±2.27mm and 4.27±2.47mm based on 3D US and CBCT images, respectively. No significant differences were observed between hybrid and tilt image acquisition geometries with all mean registration errors ≤1.2mm. 3D US volunteer images resulted in clear reconstruction of clinically relevant anatomy. A mechanically tracked system with geometrically variable 3D US provides a utility that enables enhanced applicator guidance, placement verification, and improved clinical workflow during focal liver tumor ablation procedures. Evaluations of the tracking accuracy, targeting capabilities, and clinical imaging feasibility of the proposed 3D US system, provided evidence for clinical translation. This system could provide a workflow for improving applicator placement and reducing local cancer recurrence during interventional procedures treating liver cancer and has the potential to be expanded to other abdominal interventions and procedures.

To determine the additional information and clinical impact provided by three-dimensional ultrasound (3D US) imaging of fetal anomalies compared to conventional 2-dimensional ultrasound (2D US). Sixty-three patients with 103 anomalies were scanned prospectively with both 2D and 3D US. Each anomaly was reviewed by one or more fetal imaging specialists to determine whether the 3D US data were advantageous, equivalent, or disadvantageous when compared with 2D US images. Clinical impact and pathologic or clinical outcome were determined in all cases. The 3D US images provided additional information in 53 anomalies (51%), were equivalent to 2D US images in 46 anomalies (45%), and were disadvantageous in four anomalies (4%). The 3D US was most helpful in evaluating fetuses with facial anomalies, hand and foot abnormalities and axial spine and neural tube defects. Planar images derived from 3D US volume data sets generally were more helpful for diagnostic purposes, whereas rendered 3D US images were more useful as a point of reference and were better appreciated by patients in understanding fetal abnormalities. Additional information provided by 3D US images impacted clinical management in 5% of patients. The 3D US images were disadvantageous in two fetuses with multiple anomalies and two with cardiac anomalies. The 3D US offered diagnostic advantages in about one-half of the selected cases studied and had effect on patient management in 5% of cases. This modality can be a powerful adjunctive tool to 2D US in providing a more comprehensible, 3D US impression of congenital anomalies. Thus, 3D US is currently most helpful as a targeted study complementing 2D US.

Cesarean scar pregnancy (CSP) refers to the phenomenon in which a fertilized egg implants and develops in the scar of the uterus in a woman with a history of cesarean section. The study aimed to explore the differential diagnostic value of two-dimensional ultrasound (2D US) combined with three-dimensional ultrasound (3D US) for CSP. Clinical data of 89 patients with CSP admitted to our hospital from January 2022 to January 2023 were retrospectively analyzed. Of them, 65 patients met the inclusion criteria. Patients underwent 2D US, 3D US, and combined 2D and 3D US imaging. Using the clinical pathological diagnosis as the "gold standard", the differential diagnostic value of 2D US, 3D US, and 2D US combined with 3D US for CSP was compared. The detection rate of CSP using a combined 2D US and 3D US was 98.46%, which was higher than 84.62% and 89.23% achieved with 2D US and 3D US alone, respectively (P<0.05). The pathological results showed that among 65 patients, CSP type I accounted for 24.62%, type II accounted for 55.38%, and type III accounted for 20.00%. The coincidence rate of 2D US combined with 3D US was 98.46%, which was higher than that of 2D US (83.08%) and 3D US 89.23%) alone (P<0.05). The accuracy, specificity, and sensitivity of 2D US combined with 3D US in diagnosing CSP were higher compared to the two methods alone (P<0.05). The combination of 2D US and 3D US can accurately detect and classify CSP, further improving diagnostic efficiency.

Transesophageal high-intensity focused ultrasound (HIFU) energy can be used to treat cardiac arrhythmia efficiently non-invasively. Since the esophagus is located just behind the heart, it offers a perfect acoustic window. Hence, HIFU can be directed toward the heart to perform ablation. In a previous study a HIFU probe with one 2D US image perpendicular to the esophagus axis for guidance purpose has been proposed. A new dual-mode HIFU probe with two perpendicular 2D US imaging plane is now under development. In this paper we propose a therapy guidance system, based on an intensity-based registration of the two perpendicular 2D US to preoperative 3D CT. As a proof of concept we developed the following evaluation framework on a numerical phantom: 1) we define a ground truth (GT) initial pose inside a CT volume and simulated two perpendicular US images from the CT data; 2) we run the registration framework from 55 randomly defined pose initializations around the initial GT pose; and 3) we estimated the accuracy of the registration by (a) the transformation parameter estimation errors and (b) Target Registration Error (TRE). The accuracy of the registration using two 2D US plane has been compared to the previous work performed on only one US plane. An improvement was observed when using two 2D US planes with regards to the previous one US plane.

Precise 3D modeling of the mitral valve has the potential to improve our understanding of valve morphology, particularly in the setting of mitral regurgitation (MR). Toward this goal, the authors have developed a user-initialized algorithm for reconstructing valve geometry from transesophageal 3D ultrasound (3D US) image data. Semi-automated image analysis was performed on transesophageal 3D US images obtained from 14 subjects with MR ranging from trace to severe. Image analysis of the mitral valve at midsystole had two stages: user-initialized segmentation and 3D deformable modeling with continuous medial representation (cm-rep). Semi-automated segmentation began with user-identification of valve location in 2D projection images generated from 3D US data. The mitral leaflets were then automatically segmented in 3D using the level set method. Second, a bileaflet deformable medial model was fitted to the binary valve segmentation by Bayesian optimization. The resulting cm-rep provided a visual reconstruction of the mitral valve, from which localized measurements of valve morphology were automatically derived. The features extracted from the fitted cm-rep included annular area, annular circumference, annular height, intercommissural width, septolateral length, total tenting volume, and percent anterior tenting volume. These measurements were compared to those obtained by expert manual tracing. Regurgitant orifice area (ROA) measurements were compared to qualitative assessments of MR severity. The accuracy of valve shape representation with cm-rep was evaluated in terms of the Dice overlap between the fitted cm-rep and its target segmentation. The morphological features and anatomic ROA derived from semi-automated image analysis were consistent with manual tracing of 3D US image data and with qualitative assessments of MR severity made on clinical radiology. The fitted cm-reps accurately captured valve shape and demonstrated patient-specific differences in valve morphology among subjects with varying degrees of MR severity. Minimal variation in the Dice overlap and morphological measurements was observed when different cm-rep templates were used to initialize model fitting. This study demonstrates the use of deformable medial modeling for semi-automated 3D reconstruction of mitral valve geometry using transesophageal 3D US. The proposed algorithm provides a parametric geometrical representation of the mitral leaflets, which can be used to evaluate valve morphology in clinical ultrasound images.

Three-dimensional ultrasound (3D US) of the carotid artery provides measurements of arterial wall and plaque [vessel wall volume (VWV)] that are complementary to the one-dimensional measurement of the carotid artery intima-media thickness. 3D US VWV requires an observer to delineate the media-adventitia boundary (MAB) and lumen-intima boundary (LIB) of the carotid artery. The main purpose of this work was to develop and evaluate a semiautomated segmentation algorithm for delineating the MAB and LIB of the carotid artery from 3D US images. To segment the MAB and LIB, the authors used a level set method and combined several low-level image cues with high-level domain knowledge and limited user interaction. First, the operator initialized the algorithm by choosing anchor points on the boundaries, identified in the images. The MAB was segmented using local region- and edge-based energies and an energy that encourages the boundary to pass through anchor points from the preprocessed images. For the LIB segmentation, the authors used local and global region-based energies, the anchor point-based energy, as well as a constraint promoting a boundary separation between the MAB and LIB. The data set consisted of 231 2D images (11 2D images per each of 21 subjects) extracted from 3D US images. The image slices were segmented five times each by a single observer using the algorithm and the manual method. Volume-based, region-based, and boundary distance-based metrics were used to evaluate accuracy. Moreover, repeated measures analysis was used to evaluate precision. The algorithm yielded an absolute VWV difference of 5.0% +/- 4.3% with a segmentation bias of -0.9% +/- 6.6%. For the MAB and LIB segmentations, the method gave absolute volume differences of 2.5% +/- 1.8% and 5.6% +/- 3.0%, Dice coefficients of 95.4% +/- 1.6% and 93.1% +/- 3.1%, mean absolute distances of 0.2 +/- 0.1 and 0.2 +/- 0.1 mm, and maximum absolute distances of 0.6 +/- 0.3 and 0.7 +/- 0.6 mm, respectively. The coefficients of variation of the algorithm (5.1%) and manual methods (3.9%) were not significantly different, but the average time saved using the algorithm (2.8 min versus 8.3 min) was substantial. The authors generated and tested a semiautomated carotid artery VWV measurement tool to provide measurements with reduced operator time and interaction, with high Dice coefficients, and with necessary required precision.

This study aimed to determine whether there are differences in the lateral ventricular volumes, measured by three-dimensional ultrasound (3D US) depending on the posture of the neonate (right and left lateral decubitus). This was a prospective analysis of the lateral ventricular volumes of preterm neonates recruited from Victoria Hospital, London, Ontario (June 2018-November 2019). A total of 24 premature neonates were recruited. The first cohort of 18 unstable premature neonates were imaged with 3D US in their current sides providing 15 right-sided and 16 left-sided 3D US images. The neonates in the second cohort of six relatively stable infants were imaged after positioning in each lateral decubitus position for 30 minutes, resulting in 40 3D US images obtained from 20 posture change sessions. The images were segmented and the ventricle volumes in each lateral posture were compared with determine whether the posture of the head influenced the volume of the upper and lower ventricle. For the first cohort who did not have their posture changed, the mean of the right and left ventricle volumes were 23.81 ± 15.51 and 21.61 ± 16.19 cm3, respectively, for the 15 images obtained in a right lateral posture and 13.96 ± 8.69 and 14.92 ± 8.77 cm3, respectively, for the 16 images obtained in the left lateral posture. Similarly, for the second cohort who had their posture changed, the mean of right and left ventricle volumes were 20.92 ± 17.3 and 32.74 ± 32.33 cm3, respectively, after 30 minutes in the right lateral posture, and 21.25 ± 18.4 and 32.65 ± 31.58 cm3, respectively, after 30 minutes in the left lateral posture. Our results failed to show a statistically significant difference in ventricular volumes dependence on posture. Head positioned to any lateral side for 30 minutes does not have any effect on the lateral ventricular volumes of neonates. · Three-dimensional cranial ultrasound can measure neonatal ventricle volume.. · Ventricle volume in each lateral ventricle may be affected by posture of the neonate.. · The 30 minutes in any lateral posture is not sufficient to create volume difference in lateral ventricles..

Freehand three-dimensional ultrasound (3D US) imaging is commonly used for various diagnostic and therapeutic procedures. In this technique, accurate tracking of the US transducer is a crucial requirement to develop high-quality 3D US volumes. However, current methods for transducer tracking are generally expensive and inconvenient. This paper presents a low-cost camera-based system for tracking the US transducer with six degrees of freedom (DoF). In this system, two orthogonal cameras with non-overlapped views are mounted on the US transducer. During US scanning, the two cameras are employed to track artificial features attached to the skin of the patient. A 3D surface map is constructed based on the tracked features and the 3D poses of each camera with respect to the skin are extracted separately. The estimated poses of the two cameras are spatially combined to provide accurate and robust pose estimation of the US transducer. The camera-based tracking of the US transducer has been applied to synthesize freehand 3D US volumes. The performance of the proposed system is evaluated by performing in-vitro 3D US imaging experiments and quantifying the synthesized US volumes. The results demonstrate that two points in the 3D US volume separated by a distance of 10 mm can be reconstructed with an average error of 0.7 mm.

Carotid atherosclerosis is a major reason of stroke, a leading cause of death and disability. In this paper, a segmentation method based on Active Shape Model (ASM) is developed and evaluated to outline common carotid artery (CCA) for carotid atherosclerosis computer-aided evaluation and diagnosis. The proposed method is used to segment both media-adventitia-boundary (MAB) and lumen-intima-boundary (LIB) on transverse views slices from three-dimensional ultrasound (3D US) images. The data set consists of sixty-eight, 17 × 2 × 2, 3D US volume data acquired from the left and right carotid arteries of seventeen patients (eight treated with 80 mg atorvastatin and nine with placebo), who had carotid stenosis of 60% or more, at baseline and after three months of treatment. Manually outlined boundaries by expert are adopted as the ground truth for evaluation. For the MAB and LIB segmentations, respectively, the algorithm yielded Dice Similarity Coefficient (DSC) of 94.4% ± 3.2% and 92.8% ± 3.3%, mean absolute distances (MAD) of 0.26 ± 0.18 mm and 0.33 ± 0.21 mm, and maximum absolute distances (MAXD) of 0.75 ± 0.46 mm and 0.84 ± 0.39 mm. It took 4.3 ± 0.5 mins to segment single 3D US images, while it took 11.7 ± 1.2 mins for manual segmentation. The method would promote the translation of carotid 3D US to clinical care for the monitoring of the atherosclerotic disease progression and regression.

The aim of this study was to describe the potential of three-dimensional ultrasound (3D US) in paediatric and neonatal neurosonography. The potential applications are illustrated based on our experience in 150 patients using three different 3D US techniques at two different sites. Various disease entities throughout the paediatric age have been evaluated. The potential of 3D US, including 3D US of the cerebral vessels based on colour Doppler data, is discussed based on comparison with conventional 2D US or other imaging (as available), and with regard to the literature. In our experience, 3D US is feasible in neonatal and paediatric neurosonography. It reduces imaging time, improves demonstration of complex anatomy and vasculature, and allows for evaluation of anatomy/pathology in any plane. The 3D US furthermore improves volume assessment (e.g. in hydrocephalus), and comparison with CT, MRI and during follow-up, with a potentially improved standardisation and documentation. The 3D US additionally offers an ideal modality for training and education, as the brain and the neonatal spine can be virtually rescanned at the workstation. Yet, limitations such as areas inaccessible to 2D US, limited resolution and motion artefacts have to be acknowledged. Three-dimensional US has the potential to become a valuable additional imaging tool in paediatric neurosonography.

We investigated the utility of three manual planimetric methods to quantify carotid plaque volume. A single observer measured 15 individual plaques from 15 three-dimensional (3D) ultrasound (3D US) images of patients ten times each using three different planimetric approaches. Individual plaque volumes were measured (range: 32.6-597.1 mm3) using a standard planimetric approach (M1) whereby a plaque end was identified and sequential contours were measured. The same plaques were measured using a second approach (M2), whereby plaque ends were first identified and the 3D US image of the plaque was then subdivided into equal intervals. A third method (M3) was used to measure total plaque burden (range: 165.1-1080.0 mm3) in a region (+/- 1.5 cm) relative to the carotid bifurcation. M1 systematically underestimated individual plaque volume compared to M2 (V2 = V1 + 14.0 mm3, r = 0.99, p = 0.006) due to a difference in the mean plaque length measured. Coefficients of variance (CV) for M1 and M2 decrease with increasing plaque volume, with M2 results less than M1. Root mean square difference between experimental and theoretical CV for M2 was 3.2%. The standard deviation in the identification of the transverse location of the carotid bifurcation was 0.56 mm. CVs for plaque burden measured using M3 ranged from 1.2% to 7.6% and were less than CVs determined for individual plaque volumes of the same volume. The utility of M3 was demonstrated by measuring carotid plaque burden and volume change over a period of 3 months in three patients. In conclusion, M2 was determined to be a more superior measurement technique than M1 to measure individual plaque volume. Furthermore, we demonstrated the utility of M3 to quantify regional plaque burden and to quantify change in plaque volume.

We propose a radiation-free three dimensional (3D) navigation and vasculature reconstruction method to reduce aortic stent graft deployment time and repeated exposures to high doses of X-ray radiation. 2D intraoperative US images are fused with 3D preoperative magnetic resonance (MR) image to provide intuitive 3D navigation for deployment of the stent-graft in the proposed system. On the other hand, calibrated 2D US images track catheter’s tip and construct intraoperative 3D aortic model by combining segmented intravascular ultrasound (IVUS) images. The constructed 3D aortic models can quantitatively assess morphological characteristics of aortic to assist deployment of stent graft. This system was validated by using in vitro cardiac and aorta phantom. The mean target registration error of 2D US-3D MR registration was 2.70 mm and the average tracking error of position of IVUS catheter’s tip was 1.12 mm. Accurate contours detection results in IVUS images were acquired. Meanwhile, Hausdorff distances are 0.78 mm and 0.59 mm for outer and inner contours, respectively; Dice coefficients are 90.21 % and 89.96 %. Experiment results demonstrate that our radiation-free navigation and 3D vasculature reconstruction method is promising for deployment of stent graft in vivo studies.

This paper presents a visual-servoing method for compensating motion of soft tissue structures using 4D ultra-sound. The motion of soft tissue structures caused by physiological and external motion makes it difficult to investigate them for diagnostic and therapeutic purposes. The main goal is to track non-rigidly moving soft tissue structures and compensate the motion in order to keep a lesion on its target position during a treatment. We define a 3D non-rigid motion model by extending the Thin-Plate Spline (TPS) algorithm. The motion parameters are estimated with intensity-value changes of a points set in a tracking soft tissue structure. Finally, the global rigid motion is compensated with a 6-DOF robot according to the motion parameters of the tracking structure. Simulation experiments are performed with recorded 3D US images of in-vivo soft tissue structures and validate the effectiveness of the non-rigid motion tracking method. Robotic experiments demonstrated the success of our method with a deformable phantom.

Accurate dose delivery in stereotactic partial breast irradiation (S-PBI) is challenging because of the target position uncertainty caused by breast deformation, the target volume changes caused by lumpectomy cavity shrinkage, and the target delineation uncertainty on simulation computed tomography (CT) images caused by poor soft tissue contrast. We have developed a volumetric ultrasound tomography (UST) image guidance system for prone position S-PBI. The system is composed of a novel 3D printed rotation water tank, a patient-specific resin breast immobilization cup, and a 1D array ultrasound transducer. Coronal 2D US images were acquired in 5° increments over a 360° range, and planes were acquired every 2 mm in elevation. A super-compounding technique was used to reconstruct the image volume. The image quality of UST was evaluated with a BB-1 breast phantom and BioZorb surgical marker, and the results revealed that UST offered better soft tissue contrast than CT and similar image quality to MR. In the evaluated plane, the size and location of five embedded objects were measured and compared to MR, which is considered as the ground truth. Objects’ diameters and the distances between objects in UST differ by approximately 1 to 2 mm from those in MR, which showed that UST offers the image quality required for S-PBI. In future work we will develop a robotic system that will be ultimately implemented in the clinic.

Ultrasound imaging is one of the image modalities that can be used for radiation dose guidance during radiotherapy workflows of prostate cancer patients. To allow for image acquisition during the treatment, the ultrasound probe needs to be positioned on the body of the patient before the radiation delivery starts using e.g. a mechanical arm. This is an essential step, as the operator cannot be present in the room when the radiation beam is turned on. Changes in anatomical structures or small motions of the patient during the dose delivery can compromise ultrasound image quality, due to e.g. loss of acoustic coupling or sudden appearance of shadowing artifacts. Currently, an operator is still needed to identify this quality loss. We introduce a prototype deep learning algorithm that can automatically assign a quality score to 2D US images of the male pelvic region based on their usability during an ultrasound guided radiotherapy workflow. It has been shown that the performance of this algorithm is comparable with a medical accredited sonographer and two radiation oncologists.