A clinical system for three-dimensional extended-field-of-view ultrasound

Abstract

Objective: This work is concerned with the creation of three-dimensional (3D) extended-field-of-view ultrasound from a set of volumes acquired using a mechanically swept 3D probe. 3D volumes of ultrasound data can be registered by attaching a position sensor to the probe; this can be an inconvenience in a clinical setting. A position sensor can also cause some misalignment due to patient movement and respiratory motion. We propose a combination of three-degrees-of-freedom image registration and an unobtrusively integrated inertial sensor for measuring orientation. The aim of this research is to produce a reliable and portable ultrasound system that is able to register 3D volumes quickly, making it suitable for clinical use. Method: As part of a feasibility study we recruited 28 pregnant females attending for routine obstetric scans to undergo 3D extended-field-of-view ultrasound. A total of 49 data sets were recorded. Each registered data set was assessed for correct alignment of each volume by two independent observers. Results: In 77-83% of the data sets more than four consecutive volumes registered. The successful registration relies on good overlap between volumes and is adversely affected by advancing gestational age and foetal movement. Conclusion: The development of reliable 3D extended-field-of-view ultrasound may help ultrasound practitioners to demonstrate the anatomical relation of pathology and provide a convenient way to store data. Three-dimensional (3D) ultrasound has become increasingly popular in recent years, providing an efficient framework for safe, low-cost volumetric imaging. The main clinical applications are at present in obstetrics, in areas such as assessment of cleft lip [1,2]. Other research groups have explored 3D ultrasound in areas such as cardiac assessment [3,4] and evaluation of the foetal brain [2, 5] using a single 3D volume. In our experience at a tertiary referral centre, 3D ultrasound is not routinely used despite it being readily available. The combination of 3D ultrasound and extended field of view may facilitate a wider use of 3D ultrasound by allowing ultrasound practitioners to image larger structures. It is well recognised that ultrasound image acquisition and interpretation is more operator-dependent than other imaging modalities such as CT or MRI. Providing 3D extended-field-of-view ultrasound may aid the interpretation of ultrasound images by demonstrating the anatomical relations of pathology pictorially to clinicians.There are three ways to acquire 3D data [6]. The most obvious one is to have a 2D array of transducer elements in contact with the patient. This can record 3D data directly by using different combinations of elements to scan the volume of interest. Because dense arrays of 2D transducers are difficult to build, alternative approaches have been developed using 1D transducer arrays to produce 2D B-scan images at known locations in 3D space. The second group of techniques, called freehand 3D ultrasound, involves letting the clinician sweep the 1D transdu...

Stitching of sensor-navigated 3D ultrasound datasets for the determination of large thyroid volumes – a phantom study

“…In 3D-US, the resulting 3D datasets can be reconstructed in the three standard dimensions and evaluated post hoc, in accordance with computed tomography (CT) and magnetic resonance imaging (MRI) [12]. Indeed, the interpretation of 3D-US images may be less prone to inter-observer variability, given the clearer and more objective images [13]. However, 3D-US presents some limitations [12].…”

“…Another approach used in 3D-US is the enlargement of the detectable anatomical context through the assembly (stitching) of two or more 3D datasets. This strategy has been investigated in different fields (gynecology, urology, gastrointestinal, cardiology, and orthopedics) [7,12,13,[15][16][17][18], but not yet in thyroid studies. Additionally, the above studies did not focus on volumetric analysis but rather on distance measurements or comparisons between 3D-US EFOV and CT data.…”

“…Orientation of 3D-US datasets before stitching can be performed automatically or semi-automatically [12,13,16,17,[19][20][21]; however, in this study, we opted for a manual approach based on the phantom landmarks, with a time span of not more than 2 min. The results show Rho*: correlation coefficient according to Bravais-Pearson analyses; 95% CI: 95% confidence interval of the mean; LOA: Limit of agreement; em: ellipsoid mode; mt: manual tracing that the manual adjustment and the stitching of separately obtained 3D-US datasets acquired via sensor-navigated probe was possible and in fact accurate.…”

Stitching of 3D ultrasound datasets for the determination of large thyroid volumes – phantom study part II: mechanically-swept probes

“…This restricts the interpretation of anatomical contexts and particularly limits the measurement of large thyroid volumes. Therefore, several EFOV approaches have been investigated [21,[30][31][32][33]. One strategy, stitching of two or more separately acquired 3D-US datasets, has been published in different fields, e.g.…”

Dual-Enhanced Registration for Field of View Ultrasound Sonography

“…In the traditional ultrasonic extended field of view imaging technology, it is an effective method to obtain wide range images by image stitching using feature point matching [8]. The feature points in image stitching come from the processed image obtained by certain processing of the original image, and the matching of the original ultrasonic image is realized by matching the feature points and their matching relationship [9].…”