Versatile Low-Cost Volumetric 3-D Ultrasound Platform for Existing Clinical 2-D Systems

Current and future utility of ultrasound imaging in upper extremity musculoskeletal rehabilitation: A scoping review

STUDY DESIGN

This study was a scoping review.

BACKGROUND

Continued advances in musculoskeletal sonography technology and access have increased the feasibility of point-of-care use to support day-to-day clinical care and decision-making. Sonography can help improve therapeutic outcomes in upper extremity (UE) rehabilitation by enabling clinicians to visualize underlying structures during treatment.

PURPOSE OF THE STUDY

This study aimed to (1) evaluate the growth, range, extent, and composition of sonography literature supporting UE rehabilitation; (2) identify trends, gaps, and opportunities with regard to anatomic areas and diagnoses examined and ultrasound techniques used; and (3) evaluate potential research and practice utility.

METHODS

Searches were completed in PubMed, CINAHL, SPORTDiscus, PsycINFO, and BIOSIS. We included data-driven articles using ultrasound imaging for upper extremity structures in rehabilitation-related conditions. Articles directly applicable to UE rehabilitation were labeled direct articles, while those requiring translation were labeled indirect articles. Articles were further categorized by ultrasound imaging purpose. Article content between the two groups was descriptively compared, and direct articles underwent an evaluation of evidence levels and narrative synthesis to explore potential clinical utility.

RESULTS

Average publication rates for the final included articles (n = 337) steadily increased. Indirect articles (n = 288) used sonography to explore condition etiology, assess measurement properties, inform medical procedure choice, and grade condition severity. Direct articles (n = 49) used sonography to assess outcomes, inform clinical reasoning, and aid intervention delivery. Acute UE conditions and emerging sonography technology were rarely examined, while tendon, muscle, and soft tissue conditions and grayscale imaging were common. Rheumatic and peripheral nerve conditions and Doppler imaging were more prevalent in indirect than direct articles. Among reported sonography service providers, there was a high proportion of nonradiologist clinicians.

CONCLUSION

Sonography literature for UE rehabilitation demonstrates potential utility in evaluating outcomes, informing clinical reasoning, and assisting intervention delivery. A large peripheral knowledge base provides opportunities for clinical applications; however, further research is needed to determine clinical efficacy and impact for specific applications.

IMU-Assisted Manual 3D-Ultrasound Imaging Using Motion-Constrained Swept-Fan Scans

Three-dimensional (3D) ultrasonic imaging can enable post-facto plane of interest selection. It can be performed with devices such as wobbler probes, matrix probes, and sensor-based probes. Ultrasound systems that support 3D-imaging are expensive with added hardware complexity compared to 2D-imaging systems. An inertial measurement unit (IMU) can potentially be used for 3D-imaging by using it to track the motion of a one-dimensional array probe and constraining its motion in one degree of freedom (1-DoF) rotation (swept-fan). This work demonstrates the feasibility of an affordable IMU-assisted manual 3D-ultrasound scanner (IAM3US). A consumer-grade IMU-assisted 3D scanner prototype is designed with two support structures for swept-fan. After proper IMU calibration, an appropriate KF-based algorithm estimates the probe orientation during the swept-fan. An improved scanline-based reconstruction method is used for volume reconstruction. The evaluation of the IAM3US system is done by imaging a tennis ball filled with water and the head region of a fetal phantom. From fetal phantom reconstructed volumes, suitable 2D planes are extracted for biparietal diameter (BPD) manual measurements. Later, in-vivo data is collected. The novel contributions of this paper are (1) the application of a recently proposed algorithm for orientation estimation of swept-fan for 3D imaging, chosen based on the noise characteristics of selected consumer grade IMU (2) assessment of the quality of the 1-DoF swept-fan scan with a deflection detector along with monitoring of maximum angular rate during the scan and (3) two probe holder designs to aid the operator in performing the 1-DoF rotational motion and (4) end-to-end 3D-imaging system-integration. Phantom studies and preliminary in-vivo obstetric scans performed on two patients illustrate the usability of the system for diagnosis purposes.

Accuracy and Feasibility of Three-Dimensional Ultrasound Testing in Eye Clinic and Emergency Department Patients with Vision Complaints

BACKGROUND

Ocular emergencies comprise 2-3% of emergency department (ED) visits, with retinal detachment requiring emergency surgery. Two-dimensional ultrasound is a rapid bedside tool but is highly operator dependent.

OBJECTIVE

We determined three-dimensional ultrasound (3DUS) feasibility, acceptability, and usability in eye pathology detection using the ophthalmologist examination as reference standard.

METHODS

We performed a prospective, blinded cohort study of a 3DUS-enabling device in 30 eye clinic and ED patients with visual symptoms and calculated 3DUS performance characteristics. Two expert readers interpreted the 3DUS images for pathology. All participants completed surveys.

RESULTS

3DUS sensitivity was 0.81, specificity 0.73, positive predictive value 0.54, negative predictive value 0.91, and likelihood ratio (LR)+/LR- 3.03 and 0.26, respectively. Novice and expert sonographers had "substantial" agreement in correct diagnosis of abnormal vs. normal (κ = 0.68, 95% confidence interval 0.48-0.88). Most patients indicated that 3DUS is fast, comfortable, helps them understand their problem, and improves provider interaction/care, and all sonographers agreed; 4/5 sonographers felt confident performing ultrasound. Expert readers correctly identified an abnormal eye in 83/120 scans (76%) and correct diagnosis in 72/120 scans (65%), with no statistical difference between novice (79%; 69%) and expert (72%; 61%) sonographers (p = 0.39, p = 0.55), suggesting reduced operator dependence. Reader diagnosis confidence and image quality varied widely. Image acquisition times were fast for novice (mean 225 ± 83 s) and expert (201 ± 51) sonographers, with fast expert reader interpretation times (225 ± 136).

CONCLUSIONS

A 3DUS-enabling device demonstrates a sensitivity of 0.81 and specificity of 0.73 for disease detection, fast image acquisition, and may reduce operator dependence for detecting emergent retinal pathologies. Further technological development is needed to improve diagnostic accuracy in identifying and characterizing retinal pathology.

Fast fetal head compounding from multi-view 3D ultrasound

The diagnostic value of ultrasound images may be limited by the presence of artefacts, notably acoustic shadows, lack of contrast and localised signal dropout. Some of these artefacts are dependent on probe orientation and scan technique, with each image giving a distinct, partial view of the imaged anatomy. In this work, we propose a novel method to fuse the partially imaged fetal head anatomy, acquired from numerous views, into a single coherent 3D volume of the full anatomy. Firstly, a stream of freehand 3D US images is acquired using a single probe, capturing as many different views of the head as possible. The imaged anatomy at each time-point is then independently aligned to a canonical pose using a recurrent spatial transformer network, making our approach robust to fast fetal and probe motion. Secondly, images are fused by averaging only the most consistent and salient features from all images, producing a more detailed compounding, while minimising artefacts. We evaluated our method quantitatively and qualitatively, using image quality metrics and expert ratings, yielding state of the art performance in terms of image quality and robustness to misalignments. Being online, fast and fully automated, our method shows promise for clinical use and deployment as a real-time tool in the fetal screening clinic, where it may enable unparallelled insight into the shape and structure of the face, skull and brain.

Three-dimensional ultrasound image reconstruction based on 3D-ResNet in the musculoskeletal system using a 1D probe:ex vivoandin vivofeasibility studies

Objective. Three-dimensional (3D) ultrasound (US) is needed to provide sonographers with a more intuitive panoramic view of the complex anatomical structure, especially the musculoskeletal system. In actual scanning, sonographers may perform fast scanning using a one-dimensional (1D) array probe .at random angles to gain rapid feedback, which leads to a large US image interval and missing regions in the reconstructed volume.Approach.In this study, a 3D residual network (3D-ResNet) modified by a 3D global residual branch (3D-GRB) and two 3D local residual branches (3D-LRBs) was proposed to retain detail and reconstruct high-quality 3D US volumes with high efficiency using only sparse two-dimensional (2D) US images. The feasibility and performance of the proposed algorithm were evaluated onex vivoandin vivosets.Main results. High-quality 3D US volumes in the fingers, radial and ulnar bones, and metacarpophalangeal joints were obtained by the 3D-ResNet, respectively. Their axial, coronal, and sagittal slices exhibited rich texture and speckle details. Compared with kernel regression, voxel nearest-neighborhood, squared distance weighted methods, and a 3D convolution neural network in the ablation study, the mean peak-signal-to-noise ratio and mean structure similarity of the 3D-ResNet were up to 28.53 ± 1.29 dB and 0.98 ± 0.01, respectively, and the corresponding mean absolute error dropped to 0.023 ± 0.003 with a better resolution gain of 1.22 ± 0.19 and shorter reconstruction time.Significance.These results illustrate that the proposed algorithm can rapidly reconstruct high-quality 3D US volumes in the musculoskeletal system in cases of a large amount of data loss. This suggests that the proposed algorithm has the potential to provide rapid feedback and precise analysis of stereoscopic details in complex and meticulous musculoskeletal system scanning with a less limited scanning speed and pose variations for the 1D array probe.

Development of an ultrasound guided focused ultrasound system for 3D volumetric low energy nanodroplet-mediated histotripsy

Low pressure histotripsy is likely to facilitate current treatments that require extremely high pressures. An ultrasound guided focused ultrasound system was designed to accommodate a rotating imaging transducer within a low frequency therapeutic transducer that operates at a center frequency of 105 kHz. The implementation of this integrated system provides real-time therapeutic and volumetric imaging functions, that are used here for low-cost, low-energy 3D volumetric ultrasound histotripsy using nanodroplets. A two-step approach for low pressure histotripsy is implemented with this dual-array. Vaporization of nanodroplets into gaseous microbubbles was performed via the 1D rotating imaging probe. The therapeutic transducer is then used to detonate the vaporized nanodroplets and trigger potent mechanical effects in the surrounding tissue. Rotating the imaging transducer creates a circular vaporized nanodroplet shape which generates a round lesion upon detonation. This contrasts with the elongated lesion formed when using a standard 1D imaging transducer for nanodroplet activation. Optimization experiments show that maximal nanodroplet activation can be achieved with a 2-cycle excitation pulse at a center frequency of 3.5 MHz, and a peak negative pressure of 3.4 MPa (a mechanical index of 1.84). Vaporized nanodroplet detonation was achieved by applying a low frequency treatment at a center frequency of 105 kHz and mechanical index of 0.9. In ex-vivo samples, the rotated nanodroplet activation method yielded the largest lesion area, with a mean of 4.7 ± 0.5 mm², and a rounded shape. In comparison, standard fixed transducer nanodroplet activation resulted in an average lesion area of 2.6 ± 0.4 mm², and an elongated shape. This hybrid system enables to achieve volumetric low energy histotripsy, and thus facilitates the creation of precise, large-volume mechanical lesions in tissues, while reducing the pressure threshold required for standard histotripsy by over an order of magnitude.

Recent Advances in Tracking Devices for Biomedical Ultrasound Imaging Applications

With the rapid advancement of tracking technologies, the applications of tracking systems in ultrasound imaging have expanded across a wide range of fields. In this review article, we discuss the basic tracking principles, system components, performance analyses, as well as the main sources of error for popular tracking technologies that are utilized in ultrasound imaging. In light of the growing demand for object tracking, this article explores both the potential and challenges associated with different tracking technologies applied to various ultrasound imaging applications, including freehand 3D ultrasound imaging, ultrasound image fusion, ultrasound-guided intervention and treatment. Recent development in tracking technology has led to increased accuracy and intuitiveness of ultrasound imaging and navigation with less reliance on operator skills, thereby benefiting the medical diagnosis and treatment. Although commercially available tracking systems are capable of achieving sub-millimeter resolution for positional tracking and sub-degree resolution for orientational tracking, such systems are subject to a number of disadvantages, including high costs and time-consuming calibration procedures. While some emerging tracking technologies are still in the research stage, their potentials have been demonstrated in terms of the compactness, light weight, and easy integration with existing standard or portable ultrasound machines.

Validity of Freehand 3-D Ultrasound System in Measurement of the 3-D Surface Shape of Shoulder Muscles

Freehand 3-D ultrasound (3DUS) system is a promising technique for accurately assessing muscle morphology. However, its accuracy has been validated mainly in terms of volume by examining lower limb muscles. This study was aimed at validating 3DUS in the measurements of 3-D surface shape and volume by comparing them with magnetic resonance imaging (MRI) measurements while ensuring the reproducibility of participant posture by focusing on the shoulder muscles. The supraspinatus, infraspinatus and posterior deltoid muscles of 10 healthy men were scanned using 3DUS and MRI while secured by an immobilization support customized for each participant. A 3-D surface model of each muscle was created from the 3DUS and MRI methods, and the agreement between them was assessed. For the muscle volume, the mean difference between the two models was within -0.51 cm³. For the 3-D surface shape, the distances between the closest points of the two models and the Dice similarity coefficient were calculated. The results indicated that the median surface distance was less than 1.12 mm and the Dice similarity coefficient was larger than 0.85. These results suggest that, given the aforementioned error is permitted, 3DUS can be used as an alternative to MRI in measuring volume and surface shape, even for the shoulder muscles.

Improving plane wave ultrasound imaging through real-time beamformation across multiple arrays

Ultrasound imaging is a widely used diagnostic tool but has limitations in the imaging of deep lesions or obese patients where the large depth to aperture size ratio (f-number) reduces image quality. Reducing the f-number can improve image quality, and in this work, we combined three commercial arrays to create a large imaging aperture of 100 mm and 384 elements. To maintain the frame rate given the large number of elements, plane wave imaging was implemented with all three arrays transmitting a coherent wavefront. On wire targets at a depth of 100 mm, the lateral resolution is significantly improved; the lateral resolution was 1.27 mm with one array (1/3 of the aperture) and 0.37 mm with the full aperture. After creating virtual receiving elements to fill the inter-array gaps, an autoregressive filter reduced the grating lobes originating from the inter-array gaps by - 5.2 dB. On a calibrated commercial phantom, the extended field-of-view and improved spatial resolution were verified. The large aperture facilitates aberration correction using a singular value decomposition-based beamformer. Finally, after approval of the Stanford Institutional Review Board, the three-array configuration was applied in imaging the liver of a volunteer, validating the potential for enhanced resolution.

Versatile Low-Cost Volumetric 3D Ultrasound Imaging Using Gimbal-Assisted Distance Sensors and an Inertial Measurement Unit

This study aims at creating low-cost, three-dimensional (3D), freehand ultrasound image reconstructions from commercial two-dimensional (2D) probes. The low-cost system that can be attached to a commercial 2D ultrasound probe consists of commercial ultrasonic distance sensors, a gimbal, and an inertial measurement unit (IMU). To calibrate irregular movements of the probe during scanning, relative position data were collected from the ultrasonic sensors that were attached to a gimbal. The directional information was provided from the IMU. All the data and 2D ultrasound images were combined using a personal computer to reconstruct 3D ultrasound image. The relative position error of the proposed system was less than 0.5%. The overall shape of the cystic mass in the breast phantom was similar to those from 2D and sections of 3D ultrasound images. Additionally, the pressure and deformations of lesions could be obtained and compensated by contacting the probe to the surface of the soft tissue using the acquired position data. The proposed method did not require any initial marks or receivers for the reconstruction of a 3D ultrasound image using a 2D ultrasound probe. Even though our system is less than $500, a valuable volumetric ultrasound image could be provided to the users.

Versatile Single-Element Ultrasound Imaging Platform using a Water-Proofed MEMS Scanner for Animals and Humans

Single-element transducer based ultrasound (US) imaging offers a compact and affordable solution for high-frequency preclinical and clinical imaging because of its low cost, low complexity, and high spatial resolution compared to array-based US imaging. To achieve B-mode imaging, conventional approaches adapt mechanical linear or sector scanning methods. However, due to its low scanning speed, mechanical linear scanning cannot achieve acceptable temporal resolution for real-time imaging, and the sector scanning method requires specialized low-load transducers that are small and lightweight. Here, we present a novel single-element US imaging system based on an acoustic mirror scanning method. Instead of physically moving the US transducer, the acoustic path is quickly steered by a water-proofed microelectromechanical (MEMS) scanner, achieving real-time imaging. Taking advantage of the low-cost and compact MEMS scanner, we implemented both a tabletop system for in vivo small animal imaging and a handheld system for in vivo human imaging. Notably, in combination with mechanical raster scanning, we could acquire the volumetric US images in live animals. This versatile US imaging system can be potentially used for various preclinical and clinical applications, including echocardiography, ophthalmic imaging, and ultrasound-guided catheterization.

Image Guided Mitral Valve Replacement: Registration of 3D Ultrasound and 2D X-ray Images

Mitral valve repair or replacement is important in the treatment of mitral regurgitation. For valve replacement, a transcatheter approach had the possibility of decrease the invasiveness of the procedure while retaining the benefit of replacement over repair. However, fluoroscopy images acquired during the procedure provide no anatomical information regarding the placement of the probe tip once the catheter has entered a cardiac chamber. By using 3D ultrasound and registering the 3D ultrasound images to the fluoroscopy images, a physician can gain a greater understanding of the mitral valve region during transcatheter mitral valve replacement surgery. In this work, we present a graphical user interface which allows the registration of two co-planar X-ray images with 3D ultrasound during mitral valve replacement surgery.

Experimental Validation of a Reliable Palmprint Recognition System Based on 2D Ultrasound Images

Ultrasound has been trialed in biometric recognition systems for many years, and at present different types of ultrasound fingerprint readers are being produced and integrated in portable devices. An important merit of the ultrasound is its ability to image the internal structure of the hand, which can guarantee improved recognition rates and resistance to spoofing attacks. In addition, ambient noise like changes of illumination, humidity, or temperature, as well as oil or ink stains on the skin do not affect the ultrasound image. In this work, a palmprint recognition system based on ultrasound images is proposed and experimentally validated. The system uses a gel pad to obtain acoustic coupling between the ultrasound probe and the user’s hand. The collected volumetric image is processed to extract 2D palmprints at various under-skin depths. Features are extracted from one of these 2D palmprints using a line-based procedure. Recognition performances of the proposed system were evaluated by performing both verification and identification experiments on a home-made database containing 281 samples collected from 32 different volunteers. An equal error rate of 0.38% and an identification rate of 100% were achieved. These results are very satisfactory, even if obtained with a relatively small database. A discussion on the causes of bad acquisitions is also presented, and a possible solution to further optimize the acquisition system is suggested.

A prospective blinded comparison of second trimester fetal measurements by expert and novice readers using low-cost novice-acquired 3D volumetric ultrasound

RATIONALE AND OBJECTIVES

Two-dimensional (2D) ultrasound (US) is operator dependent, requiring operator skill and experience to selectively identify and record planes of interest for subsequent interpretation. This limits the utility of US in settings in which expert sonographers are unavailable. Three-dimensional (3D) US acquisition of an anatomic target, which enables reconstruction of any plane through the acquired volume, might reduce operator dependence by providing any desired image plane for interpretation, without identification of target planes of interest at the time of acquisition. We applied a low-cost 3DUS technology because of the wider potential application compared with dedicated 3DUS systems. We chose second trimester fetal biometric parameters for study because of their importance in maternal-fetal health globally. We hypothesized that expert and novice interpretations of novice-acquired 3D volumes would not differ from each other nor from expert measurements of expert-acquired 2D images, the clinical reference standard.

MATERIALS AND METHODS

This was a prospective, blinded, observational study. Expert sonographers blinded to 3DUS volumes acquired 2DUS images of second trimester fetuses from 32 subjects, and expert readers performed interpretation, during usual care. A novice sonographer blinded to other clinical data acquired oriented 3DUS image volumes of the same subjects on the same date. Expert readers blinded to other data assessed placental location (PL), fetal presentation (FP), and amniotic fluid volume (AFV) in novice-acquired 3D volumes. Novice and expert raters blinded to other data independently measured biparietal diameter (BPD), humerus length (HL), and femur length (FL) for each fetus from novice-acquired 3D volumes. Corresponding gestational age (GA) estimates were calculated. Inter-rater reliability of measurements and GAs (expert 3D versus expert 2D, novice 3D versus expert 2D, and expert 3D versus novice 3D) were assessed by intraclass correlation coefficient (ICC). Mean inter-rater measurement differences were analyzed using one-way ANOVA.

RESULTS

3D volume acquisition and reconstruction required mean 30.4 s (±5.7) and 70.0 s (±24.0), respectively. PL, FP, and AFV were evaluated from volumes for all subjects; mean time for evaluation was 16 s (±0.0). PL, FP, and AFV could be evaluated for all subjects. At least one biometric measurement was possible for 31 subjects (97%). Agreement between rater pairs for a composite of all measures was excellent (ICCs ≥ 0.95), and for individual measures was good to excellent (ICCs ≥ 0.75). Inter-rater differences were not significant (p > .05).

CONCLUSIONS

Expert and novice interpretations of novice-acquired 3DUS volumes of second trimester fetuses provided reliable biometric measures compared with expert interpretation of expert-acquired 2DUS images. 3DUS volume acquisition with a low-cost system may reduce operator dependence of ultrasound.

Ultrasound Systems for Biometric Recognition

Biometric recognition systems are finding applications in more and more civilian fields because they proved to be reliable and accurate. Among the other technologies, ultrasound has the main merit of acquiring 3D images, which allows it to provide more distinctive features and gives it a high resistance to spoof attacks. This work reviews main research activities devoted to the study and development of ultrasound sensors and systems for biometric recognition purposes. Several transducer technologies and different ultrasound techniques have been experimented on for imaging biometric characteristics like fingerprints, hand vein pattern, palmprint, and hand geometry. In the paper, basic concepts on ultrasound imaging techniques and technologies are briefly recalled and, subsequently, research studies are classified according to the kind of technique used for collecting the ultrasound image. Overall, the overview demonstrates that ultrasound may compete with other technologies in the expanding market of biometrics, as the different commercial fingerprint sensors integrated in portable electronic devices like smartphones or tablets demonstrate.