3D Ultrasound Imaging System Research Articles

Development of Automatic Assessment Framework for Spine Deformity Using Freehand 3-D Ultrasound Imaging System.

A 3-D ultrasound (US) imaging technique has been studied to facilitate the diagnosis of spinal deformity without radiation. The objective of this article is to propose an assessment framework to automatically estimate spinal deformity in US spine images. The proposed framework comprises four major components, a US spine image generator, a novel transformer-based lightweight spine detector network, an angle evaluator, and a 3-D modeler. The principal component analysis (PCA) and discriminative scale space tracking (DSST) method are first adopted to generate the US spine images. The proposed detector is equipped with a redundancy queries removal (RQR) module and a regularization item to realize accurate and unique detection of spine images. Two clinical datasets, a total of 273 images from adolescents with idiopathic scoliosis, are used for the investigation of the proposed framework. The curvature is estimated by the angle evaluator, and the 3-D mesh model is established by the parametric modeling technique. The accuracy rate (AR) of the proposed detector can be achieved at 99.5%, with a minimal redundancy rate (RR) of 1.5%. The correlations between automatic curve measurements on US spine images from two datasets and manual measurements on radiographs are 0.91 and 0.88, respectively. The mean absolute difference (MAD) and standard deviation (SD) are 2.72° ± 2.14° and 2.91° ± 2.36° , respectively. The results demonstrate the effectiveness of the proposed framework to advance the application of the 3-D US imaging technique in clinical practice for scoliosis mass screening and monitoring.

Development of an integrated dual-modality 3D bioluminescence tomography and ultrasound imaging system for small animal tumor imaging.

Ultrasound (US) is a valuable tool for imaging soft tissue and visualizing tumor contours. Taking the benefits of US, we presented an integrated dual-modality imaging system in this paper that achieves three-dimensional (3D) bioluminescence tomography (BLT) with multi-view bioluminescence images and 3D US imaging. The purpose of this system is to perform non-invasive, long-term monitoring of tumor growth in 3D images. US images can enhance the accuracy of the 3D BLT reconstruction and the bioluminescence dose within an object. Furthermore, an integrated co-registered scanning geometry was used to capture the fused BLT and US images. We validated the system with an in vivo experiment involving tumor-bearing mice. The results demonstrated the feasibility of reconstructing 3D BLT images in the tumor region using 3D US images. We used the dice coefficient and locational error to evaluate the similarity between the reconstructed source region and the actual source region. The dice coefficient was 88.5%, and the locational error was 0.4 mm when comparing the BLT and 3D US images. The hybrid BLT/US system could provide significant benefits for reconstructing the source of tumor location and conducting quantitative analysis of tumor size.

Automatic Diagnosis of Carotid Atherosclerosis Using a Portable Freehand 3-D Ultrasound Imaging System.

The objective of this study is to develop a deep-learning-based detection and diagnosis technique for carotid atherosclerosis (CA) using a portable freehand 3-D ultrasound (US) imaging system. A total of 127 3-D carotid artery scans were acquired using a portable 3-D US system, which consisted of a handheld US scanner and an electromagnetic (EM) tracking system. A U-Net segmentation network was first applied to extract the carotid artery on 2-D transverse frame, and then, a novel 3-D reconstruction algorithm using fast dot projection (FDP) method with position regularization was proposed to reconstruct the carotid artery volume. Furthermore, a convolutional neural network (CNN) was used to classify healthy and diseased cases qualitatively. Three-dimensional volume analysis methods, including longitudinal image acquisition and stenosis grade measurement, were developed to obtain the clinical metrics quantitatively. The proposed system achieved a sensitivity of 0.71, a specificity of 0.85, and an accuracy of 0.80 for diagnosis of CA. The automatically measured stenosis grade illustrated a good correlation ( r = 0.76) with the experienced expert measurement. The developed technique based on 3-D US imaging can be applied to the automatic diagnosis of CA. The proposed deep-learning-based technique was specially designed for a portable 3-D freehand US system, which can provide a more convenient CA examination and decrease the dependence on the clinician's experience.

A High-Resolution 3D Ultrasound Imaging System Oriented towards a Specific Application in Breast Cancer Detection Based on a 1 × 256 Ring Array.

This paper presents the design and development of a high-resolution 3D ultrasound imaging system based on a 1 × 256 piezoelectric ring array, achieving an accuracy of 0.1 mm in both ascending and descending modes. The system achieves an imaging spatial resolution of approximately 0.78 mm. A 256 × 32 cylindrical sensor array and a digital phantom of breast tissue were constructed using the k-Wave toolbox. The signal is acquired layer by layer using 3D acoustic time-domain simulation, resulting in the collection of data from each of the 32 layers. The 1 × 256 ring array moves on a vertical trajectory from the chest wall to the nipple at a constant speed. A data set was collected at intervals of 1.5 mm, resulting in a total of 32 data sets. Surface rendering and volume rendering algorithms were used to reconstruct 3D ultrasound images from the volume data obtained via simulation so that the smallest simulated reconstructed lesion had a diameter of 0.3 mm. The reconstructed three-dimensional image derived from the experimental data exhibits the contour of the breast model along with its internal mass. Reconstructable dimensions can be achieved up to approximately 0.78 mm. The feasibility of applying the system to 3D breast ultrasound imaging has been demonstrated, demonstrating its attributes of resolution, precision, and exceptional efficiency.

Monitoring of Curve Progression in Patients with Adolescent Idiopathic Scoliosis Using 3-D Ultrasound

ObjectiveTo investigate whether 3D ultrasound can provide comparable results to conventional X-ray examination in assessing curve progression in AIS patients. Methods136 AIS subjects (42 males and 94 females; 10-18 years of age, mean of 14.1 ± 1.9 years) with different severities of scoliosis (Cobb angle ranged from 10-85 degrees, mean of 24.3 ± 14.4 degrees) were included. Each subject underwent bi-planar low-dose X-ray EOS® and 3D ultrasound system scanning with the same posture on the same date. Subjects underwent the second assessment at routine clinical follow-up. Manual measurement of scoliotic curvature on ultrasound coronal projection images and posterior-anterior radiographs were presented as ultrasound curve angle (UCA) and radiographic Cobb angle (RCA), respectively. RCA and UCA increments of five degrees or more represented a scoliosis progression detected by X-ray assessment and 3D ultrasound assessment, respectively. ResultsThe sensitivity and specificity for UCA measurement for detecting scoliosis progression were 0.93 and 0.90, respectively. The negative likelihood ratio of the diagnostic test for scoliosis progression by the 3D ultrasound imaging system was 0.08. ConclusionThe 3D ultrasound imaging method is a valid technique to detect coronal curve progression as compared to conventional radiography in follow-up of AIS. Substituting conventional radiography by 3D ultrasound is effective in reducing the radiation dose to be suffered by AIS patients during their follow-up examinations.

Investigation of 3D Reconstruction Algorithms For Wireless Freehand Ultrasound Imaging System.

The handheld 3D ultrasound imaging technique based on position tracking systems has been rapidly developed and widely applied in recent decades. The objectives of this study are to investigate the performance and accuracy of different 3D reconstruction algorithms including Voxel Nearest Neighbor (VNN), Pose Optimization Based (POB), and Implicit Representation (IR) methods. The high-precision phantom was used as the validation model to measure 2D/3D distance on the reconstructed image volume, and the measurements were evaluated with the true values obtained by caliber. The results indicated that the IR method presented the best reconstruction visualization and the smallest reconstruction errors for different motion cases. It demonstrated that the neural network-based reconstruction method can improve image quality and reduce reconstruction errors for the wireless freehand 3D ultrasound imaging systems.Clinical Relevance- This study validates the accuracy and precision of the different reconstruction algorithms for freehand 3D ultrasound imaging systems.

Liver Tumors Segmentation Using 3D SegNet Deep Learning Approach

An ultrasonic filter detects signs of malignant tumors by analysing the image’s pixel quality fluctuations caused by a liver ailment. Signs of malignant growth proximity are identified in an ultrasound filter through image pixel quality variations from a liver’s condition. Those changes are more common in alcoholic liver conditions than in other etiologies of cirrhosis, suggesting that the cause may be alcohol instead of liver disease. Existing Two-Dimensional (2D) ultrasound data sets contain an accuracy rate of 85.9% and a 2D Computed Tomography (CT) data set of 91.02%. The most recent work on designing a Three-Dimensional (3D) ultrasound imaging system in or close to real-time is examined. In this article, a Deep Learning (DL) model is implemented and modified to fit liver CT segmentation, and a semantic pixel classification of road scenes is recommended. The architecture is called semantic pixel-wise segmentation and comprises a hierarchical link of encoder-decoder layers. A standard data set was used to test the proposed model for liver CT scans and the tumor accuracy in the training phase. For the normal class, we obtained 100% precision for chronic cirrhosis hepatitis (73%), offset cirrhosis (59.26%), and offensive cirrhosis (91.67%) for chronic hepatitis or cirrhosis (73,0%). The aim is to develop a Computer-Aided Detection (CAD) screening tool to detect steatosis. The results proved 98.33% exactness, 94.59% sensitivity, and 92.11% case with Convolutional Neural Networks (CNN) classification. Although the classifier’s performance did not differentiate so clearly at this level, it was recommended that CNN generally perform better due to the good relationship between Area under the Receiver Operating Characteristics Curve (AUC) and accuracy.

A theranostic 3D ultrasound imaging system for high resolution image-guided therapy.

Microbubble contrast agents are a diagnostic tool with broad clinical impact and an increasing number of indications. Many therapeutic applications have also been identified. Yet, technologies for ultrasound guidance of microbubble-mediated therapy are limited. In particular, arrays that are capable of implementing and imaging microbubble-based therapy in three dimensions in real-time are lacking. We propose a system to perform and monitor microbubble-based therapy, capable of volumetric imaging over a large field-of-view. To propel the promise of the theranostic treatment strategies forward, we have designed and tested a unique array and system for 3D ultrasound guidance of microbubble-based therapeutic protocols based on the frequency, temporal and spatial requirements.Methods: Four 256-channel plane wave scanners (Verasonics, Inc, WA, USA) were combined to control a 1024-element planar array with 1.3 and 2.5 MHz therapeutic and imaging transmissions, respectively. A transducer aperture of ~40×15 mm was selected and Field II was applied to evaluate the point spread function. In vitro experiments were performed on commercial and custom phantoms to assess the spatial resolution, image contrast and microbubble-enhanced imaging capabilities.Results: We found that a 2D array configuration with 64 elements separated by λ-pitch in azimuth and 16 elements separated by 1.5λ-pitch in elevation ensured the required flexibility. This design, of 41.6 mm × 16 mm, thus provided both an extended field-of-view, up to 11 cm x 6 cm at 10 cm depth and steering of ±18° in azimuth and ±12° in elevation. At a depth of 16 cm in B-mode, we achieved a volume acquisition rate of 60 Hz and an imaging display rate of 30 Hz. Lateral resolution was 0.8 mm at 5 cm depth and 2.1 mm at 12.5 cm depth.Conclusion: A single 2D array for both imaging and therapeutics, integrated with a 1024 channel scanner can guide microbubble-based therapy in volumetric regions of interest.

In Situ Visualization for 3D Ultrasound-Guided Interventions with Augmented Reality Headset.

Augmented Reality (AR) headsets have become the most ergonomic and efficient visualization devices to support complex manual tasks performed under direct vision. Their ability to provide hands-free interaction with the augmented scene makes them perfect for manual procedures such as surgery. This study demonstrates the reliability of an AR head-mounted display (HMD), conceived for surgical guidance, in navigating in-depth high-precision manual tasks guided by a 3D ultrasound imaging system. The integration between the AR visualization system and the ultrasound imaging system provides the surgeon with real-time intra-operative information on unexposed soft tissues that are spatially registered with the surrounding anatomic structures. The efficacy of the AR guiding system was quantitatively assessed with an in vitro study simulating a biopsy intervention aimed at determining the level of accuracy achievable. In the experiments, 10 subjects were asked to perform the biopsy on four spherical lesions of decreasing sizes (10, 7, 5, and 3 mm). The experimental results showed that 80% of the subjects were able to successfully perform the biopsy on the 5 mm lesion, with a 2.5 mm system accuracy. The results confirmed that the proposed integrated system can be used for navigation during in-depth high-precision manual tasks.

Establishment of a 3D ultrasound imaging system based on pulse-triggered image acquisition

To establish a 3D ultrasound imaging system based on pulse-triggered image acquisition using the linear probe on the VerasonicsTM vantage 128 platform and evaluate its performance in scanning standard phantom and human carotid artery. The 3D ultrasound imaging system included 3 modules for probe motion control, image acquisition and storage, and 3D image reconstruction and display. To improve the precision of image acquisition, we used fixed frequency pulses to control the external trigger function combined with mechanical scanning. Voxel-based 3D reconstruction was used for image reconstruction and display. The user interface was designed to allow direct operations of the platform. We carried out scanning tests of standard ultrasound phantom and human carotid artery to evaluate the performance of this imaging system. We successfully constructed a 3D ultrasound imaging system based on pulse-triggered image acquisition. The results of standard phantom and human carotid scanning tests showed that each module of the system was fully functional. The self-designed user interface of this ultrasound imaging system allowed full control of the system functions for original image acquisition, 3D image reconstruction, and display of cross-sections in 3 different views. This 3D ultrasound imaging system achieves high-quality 3D ultrasound imaging and provides the basis for further study and clinical application of 3D ultrasound imaging.

3D ultrasound imaging provides reliable angle measurement with validity comparable to X-ray in patients with adolescent idiopathic scoliosis.

Background & ObjectiveThe application of ultrasound imaging for spine evaluation could minimize radiation exposure for patients with adolescence idiopathic scoliosis (AIS). A customized three-dimensional (3D) ultrasound imaging system has been demonstrated to provide reliable and valid coronal curvature measurements. However, these measurements were using the spinous processes as anatomical reference, leading to a predictable underestimation of the traditionally used Cobb angles. An alternative 3D ultrasound image reconstruction method was applied to create coronal images with more lateral features for angle measurement. The objective of this study was to test the reliability and the validity of this angle, the ultrasound curve angle (UCA), and compare the UCA with the Cobb angles on X-ray images of patients with AIS.Materials and methodsThis study was divided into: 1) Investigation of intra- and inter-reliability between two raters for measuring the UCA and two operators for acquiring ultrasound images; 2) Investigation of the validity between the radiographic Cobb angle and the UCA. Fifty patients and 164 patients with AIS, were included in the two stages, respectively. Patients underwent bi-planar X-ray and 3D ultrasound scanning on the same day. The proposed UCA was used to measure the coronal curvature from the ultrasound coronal images, which were formed using a newly customized volume projection imaging (VPI) method. The intra-rater/operator and inter-rater and operator reliability of the UCA were tested by intra-class correlation coefficient (ICC) (3,1) and (2,1), respectively. The validity of UCA measurements as compared to radiographic Cobb angles was tested by inter-method ICC (2,1), mean absolute difference (MAD), standard error of measurement (SEM), Pearson correlation coefficient and Bland–Altman statistics. The level of significance was set as 0.05.ResultsExcellent intra-rater and intra-operator (ICC (3,1)≥0.973) and excellent inter-rater and inter-operator reliability (ICC (2,1)≥0.925) for UCA measurement, with overall MAD and SEM no more than 3.5° and 1.7° were demonstrated for both main thoracic and (thoraco)lumbar curvatures. Very good correlations were observed between UCA and Cobb angle for main thoracic (=0.893) and (thoraco)lumbar (=0.884) curves. The mean (SD) measurements in terms of radiographic Cobb and UCA were 27.2 ​± ​11.6° and 26.3 ​± ​11.4° for main thoracic curves; and 26.2 ​± ​11.4° and 24.8 ​± ​9.7° for (thoraco)lumbar curve respectively. One hundred sixty-four subjects (33 male and 131 female subjects; 11–18 years of age, mean of 15.1 ​± ​1.9 years) were included for the validity session. Excellent inter-method variations (ICC (2,K) ≥0.933) with overall MAD and SEM no more than 3.0° and 1.5° were demonstrated for both main thoracic and (thoraco)lumbar curvatures. In addition, Bland–Altman plots demonstrated an acceptable agreement between ultrasound and radiographic Cobb measurements.ConclusionIn this study, very good correlations and agreement were demonstrated between the ultrasound and X-ray measurements of the scoliotic curvature. Judging from the promising results of this study, patients with AIS with different severity of curves can be evaluated and monitored by ultrasound imaging, reducing the usage of radiation during follow-ups. This method could also be used for scoliosis screening.The Translational potential of this article: Ultrasound curve angle (UCA) obtained from 3D ultrasound imaging system can provide reliable and valid evaluation on coronal curvature for patients with AIS, without the need of radiation.

Validation of Scolioscan Air-Portable Radiation-Free Three-Dimensional Ultrasound Imaging Assessment System for Scoliosis.

To diagnose scoliosis, the standing radiograph with Cobb’s method is the gold standard for clinical practice. Recently, three-dimensional (3D) ultrasound imaging, which is radiation-free and inexpensive, has been demonstrated to be reliable for the assessment of scoliosis and validated by several groups. A portable 3D ultrasound system for scoliosis assessment is very much demanded, as it can further extend its potential applications for scoliosis screening, diagnosis, monitoring, treatment outcome measurement, and progress prediction. The aim of this study was to investigate the reliability of a newly developed portable 3D ultrasound imaging system, Scolioscan Air, for scoliosis assessment using coronal images it generated. The system was comprised of a handheld probe and tablet PC linking with a USB cable, and the probe further included a palm-sized ultrasound module together with a low-profile optical spatial sensor. A plastic phantom with three different angle structures built-in was used to evaluate the accuracy of measurement by positioning in 10 different orientations. Then, 19 volunteers with scoliosis (13F and 6M; Age: 13.6 ± 3.2 years) with different severity of scoliosis were assessed. Each subject underwent scanning by a commercially available 3D ultrasound imaging system, Scolioscan, and the portable 3D ultrasound imaging system, with the same posture on the same date. The spinal process angles (SPA) were measured in the coronal images formed by both systems and compared with each other. The angle phantom measurement showed the measured angles well agreed with the designed values, 59.7 ± 2.9 vs. 60 degrees, 40.8 ± 1.9 vs. 40 degrees, and 20.9 ± 2.1 vs. 20 degrees. For the subject tests, results demonstrated that there was a very good agreement between the angles obtained by the two systems, with a strong correlation (R2 = 0.78) for the 29 curves measured. The absolute difference between the two data sets was 2.9 ± 1.8 degrees. In addition, there was a small mean difference of 1.2 degrees, and the differences were symmetrically distributed around the mean difference according to the Bland–Altman test. Scolioscan Air was sufficiently comparable to Scolioscan in scoliosis assessment, overcoming the space limitation of Scolioscan and thus providing wider applications. Further studies involving a larger number of subjects are worthwhile to demonstrate its potential clinical values for the management of scoliosis.

Validation of a three dimensional musculoskeletal ultrasound system for use in hands and wrists

Purpose: The effect of chronic synovitis on the progression of osteoarthritis pathology is a relatively new but supported concept in the fields of rheumatology and hand surgery that has been linked to pain and disability in patients. Currently, the gold standard for diagnosing synovitis in the wrists and hands is a clinical examination and the use of 2 dimensional (2D) musculoskeletal ultrasound imaging (US). Major limitations associated with this method are the lack of quantitative measurement tools available and the fact that physicians have to be able to mentally reconstruct the patient’s 3-dimensional anatomy from the 2-dimensional images provided. These limitations can be overcome by using a 3-dimensional ultrasound (3DUS) system to quantitatively measure the size of synovial hypertrophy, effusions, ganglions and osteophytes as well as having a 3D reconstruction of the patient’s hand. The aim of this work is to develop a 3D ultrasound system for imaging the hand and wrist. This paper reports on the development, geometric, and volumetric validation for wrist/hand 3D ultrasound imaging. Methods: A mechatronic wrist/hand imaging system was designed and created to operate with a conventional 2D US imaging system. The scanning system features a motor which contains a single integrated electromagnetic encoder that records the rotational position of the motor. This motor drives a lead screw which in turn moves the transducer, which is submerged in a water bath, along the linear axis to acquire a series of 2D images. The encoder information provides the software with the position of each 2D ultrasound frame. These conventional diagnostic 2D US images are then reconstructed into a 3D US images from a licensed ultrasound machine. The geometric validation of the system was done using a multi-layered monofilament grid phantom with spacings of 10 mm and the Euclidean distances between the wires were measured. The volumetric validation was conducted using a simulated synovial tissue phantom and the images were analyzed using 3D-Slicer to manually segment individual slices in the 3D image. These slices were then interpolated to construct a 3D segmentation of the phantom. This process was repeated over four days to test the intra-rater reliability of the system. The 3D volumes were compared to those found using magnetic resonance imaging (MRI) and the known volume of the agar phantom. Results: The largest error and variance recorded from the geometric validation measurements was 0.0856± 0.0087mm and was acquired from the reconstruction plane. The remaining linear measurement errors were all < 1%. The error between the mean phantom volume measurements and the known synovium phantom volume was 5.99% and 2.43% for the 3D US device and MRI respectively. Linear regression for volumetric measures revealed an R2 value of 0.4736 with a p-value of 0.20, revealing no significant correlation between the measurements made over the course of 4 days for the 3D US device. The percent difference in the volume measurements from the 3D US device and MRI was 0.814%. Conclusions: A mechatronic 3D ultrasound imaging system was developed for the wrist and hand. Successful geometric and volumetric validation demonstrates feasibility for implementation in a clinical setting. Current work evaluates system ability to accurately and quantitatively classify synovitis in first carpometacarpal joint and distal radial injury patients to investigate the relationship between chronic inflammation and the progression of osteoarthritis in patients.

Wearable AR and 3D Ultrasound: Towards a Novel Way to Guide Surgical Dissections

Nowadays, ultrasound (US) is increasingly being chosen as imaging modality for both diagnostic and interventional applications, owing to its positive characteristics in terms of safety, low footprint, and low cost. The combination of this imaging modality with wearable augmented reality (AR) systems, such as the head-mounted displays (HMD), comes forward as a breakthrough technological solution, as it allows for hands-free interaction with the augmented scene, which is an essential requirement for the execution of high-precision manual tasks, such as in surgery. What we propose in this study is the integration of an AR navigation system (HMD plus dedicated platform) with a 3D US imaging system to guide a dissection task that requires maintaining safety margins with respect to unexposed anatomical or pathological structures. For this purpose, a standard scalpel was sensorized to provide real-time feedback on the position of the instrument during the execution of the task. The accuracy of the system was quantitatively assessed with two different experimental studies: a targeting experiment, which revealed a median error of 2.53 mm in estimating the scalpel to target distance, and a preliminary user study simulating a dissection task that requires reaching a predefined distance to an occult lesion. The second experiment results showed that the system can be used to guide a dissection task with a mean accuracy of 0.65 mm, with a mean angular error between the ideal and actual cutting plane of 2.07°. The results encourage further studies to fully exploit the potential of wearable AR and intraoperative US imaging to accurately guide deep surgical tasks, such as to guide the excision of non-palpable breast tumors ensuring optimal margin clearance.

Fabrication of 2D Capacitive Micromachined Ultrasonic Transducer (CMUT) Arrays on Insulating Substrates With Through-Wafer Interconnects Using Sacrificial Release Process

A critical component in a three-dimensional (3D) ultrasound imaging system is a two-dimensional (2D) transducer array. A 2D transducer array is also essential for the implementation of a compact form factor focused ultrasound system for therapeutic applications. Considering the difficulty associated with developing 2D transducer arrays using piezoelectric technology, capacitive micromachined ultrasonic transducer (CMUT) technology with the inherent advantages has emerged as a candidate to develop these devices. Previously, we demonstrated that 2D CMUT arrays can be fabricated with through-glass-via interconnects on borosilicate substrates using anodic bonding. In this paper, we present a fabrication process for implementing $16\times 16$ -element 2D CMUT arrays on an alkali-free glass substrate using the sacrificial release method. The vacuum-sealed $16\times 16$ -element 2D CMUT array is built on an SGW3 glass substrate with copper through-glass interconnects. The fabrication process developed for the 2D CMUT array is described in detail. Across the 256 elements of the 2D CMUT array, the mean resonant frequency is measured as 4.76 MHz with a standard deviation of 46.6 kHz. Also, the mean device capacitance across the array is measured as 1.17 pF with a standard deviation of 0.12 pF, and these results agree with the finite-element analysis. This study shows an alternative method to fabricate 2D CMUT arrays on glass substrates with metal interconnects, especially when the substrate is not suitable for anodic bonding. In addition to improved reliability and reduction in parasitic interconnect capacitance and resistance, this fabrication method benefits from the flexibility of developing 2D CMUT arrays on any type of insulating substrate, and still attain optimum uniformity in both yield and functionality of the fabricated devices. [2019-0246]

Compact and Wireless Freehand 3D Ultrasound Real-time Spine Imaging System: A pilot study.

The 3D ultrasound reconstruction technology has led to a rapid development of ultrasound spine imaging in recent decades. However, the current imaging apparatus is bulky and not portable. The objective of this study is to develop a new compact and wireless system to offer the real-time visualized spine images during data acquisition. A portable and WI-FI based ultrasound scanner and a compact EM tracking system were assembled to acquire ultrasound transverse frames with location information which could be reconstructed into 3D spine image volume in real-time. The validation was implemented on the 2D coronal images of vertebra phantoms, and the in vivo data acquisition and reconstruction were demonstrated on volunteers. The result showed that the new system could provide reconstructed spine images in real time and the average errors of the reconstructed images were about 1mm (approximate to image pixel size).

Weight-bearing Imaging in Adolescent Idiopathic Scoliosis.

This article reviews the weight-bearing imaging methods in the diagnosis and monitoring of patients with adolescent idiopathic scoliosis (AIS), a three-dimensional (3D) deformity of the spine with unknown etiology. The apical vertebrae in AIS rotate away from the midline in a complex 3D pattern that formerly could only be appreciated by computed tomography (CT). Despite its superb anatomical delineation, CT is not ideal due to high radiation and scanning in either the supine or prone position; hence the full effect of gravity on the spinal curvature cannot be assessed. The introduction of low-dose stereoradiography with the capacity of 3D reconstruction has recently opened up a new era of assessment of the scoliotic spine in the upright position at multiple time points during the preoperative and postoperative period. The handheld 3D ultrasound imaging system also provides a radiation-free alternative for close monitoring for disease progression and treatment outcomes for AIS. Upright magnetic resonance imaging is radiation free and superb for the assessment of spinal cord and intervertebral disks; however, its utilization in scoliosis is limited by high cost and limited availability.

Evaluation of Scoliosis With a Commercially Available Ultrasound System.

Currently, radiography with measurement of the Cobb angle is still considered the reference standard for diagnosing scoliosis. However, the ionizing radiation hazard is drawing wide attention. Can 3-dimensional (3D) ultrasound (US) be an alternative modality for diagnosing and monitoring patients with scoliosis? The aim of our study was to assess the reliability and validity of 3D US imaging in the evaluation of scoliosis. A commercially available ultrasound system with a magnetic tracking system was selected for long-distance 3D US imaging. Straight phantoms and curved phantoms were scanned with the imaging system to evaluate the stability of the system for curvature measurements. Eight healthy adult volunteers and 28 patients with scoliosis were recruited for long-distance 3D US imaging. The intraclass correlation coefficient was used to test the reproducibility of the interobserver and intraobserver measurements for both the healthy adults and patients with scoliosis. A linear regression analysis and Bland-Altman plot were used to analyze the correlation and to determine the extent of agreement between the angles measured on US images and the Cobb angles measured on conventional radiographs. The 28 patients with scoliosis included 10 male and 18 female patients aged 8 to 37 years (mean age ± SD, 17.7 ± 1.4 years; body mass index, <25 kg/m2 ). In the phantom study, there was no statistically significant difference between the angles measured by the 3D US imaging system and those measured by an angle gauge (P > 0.05). In the clinical study, there was very good interobserver and intraobserver reliability (intraclass correlation coefficients, >0.90) for the US imaging system, with a high correlation (r2 = 0.92) and agreement between the US and radiographic methods. The long-distance 3D US imaging system offers a viable modality for diagnosing and monitoring scoliosis without radiation.

The Application of an Ultrasound Tomography Algorithm in a Novel Ring 3D Ultrasound Imaging System.

Currently, breast cancer is one of the most common cancers in women all over the world. A novel 3D breast ultrasound imaging ring system using the linear array transducer is proposed to decrease costs, reduce processing difficulties, and improve patient comfort as compared to modern day breast screening systems. The 1 × 128 Piezoelectric Micromachined Ultrasonic Transducer (PMUT) linear array is placed 90 degrees cross-vertically. The transducer surrounds the mammary gland, which allows for non-contact detection. Once the experimental platform is built, the breast model is placed through the electric rotary table opening and into a water tank that is at a constant temperature of 32 °C. The electric rotary table performs a 360° scan either automatically or mechanically. Pulse echo signals are captured through a circular scanning method at discrete angles. Subsequently, an ultrasonic tomography algorithm is designed, and a horizontal slice imaging is realized. The experimental results indicate that the preliminary detection of mass is realized by using this ring system. Circular scanning imaging is obtained by using a rotatable linear array instead of a cylindrical array, which allows the size and location of the mass to be recognized. The resolution of breast imaging is improved through the adjustment of the angle interval (>0.05°) and multiple slices are gained through different transducer array elements (1 × 128). These results validate the feasibility of the system design as well as the algorithm, and encourage us to implement our concept with a clinical study in the future.

An in-probe low-noise low-power variable-gain receive amplifier for medical ultrasound imaging using CMUT transducers

In this paper a low-power, low-noise receiver amplifier is designed for interface with capacitive micro-machined ultrasonic transducers (CMUT). In 3D in-probe ultrasound imaging systems, the interface circuit area constraint due to the specified area per CMUT element, and the circuit power constraint for each channel are the main design challenges. A fully-differential variable-gain transimpedance amplifier (VGTIA) is designed for the CMUT signal read-out. Due to the small area and low power consumption, the circuit is suitable for in-probe imaging. The VGTIA is designed for the interface with an ADC block that does the digital conversion inside the probe. The circuit is able to produce a differential output from a Zero-Bias CMUT, where the requirement for an external high voltage dc bias is eliminated. The amplifier is designed and fabricated using a 65 nm CMOS process technology. The measurement results show that the transimpedance amplifier has a gain range of 79---97 dB$$\Omega $$Ω. A noise figure (NF) of 3 dB at a 5 MHz center frequency with an only 180 $$\upmu $$μW power consumption is measured. A total area of 76$$\,\upmu $$μm$$\times $$×50$$\,\upmu $$μm is achieved which relaxes the area requirement for the following ADC block.