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

Abstract

Aims: Thyroid volume has to be measured in goiters prior to radioiodine treatment to calculate the needed amount of radioactivity. Modern clinical equipment for ultrasonography shows the trend to smaller probes, so that larger goiters do not fit any longer into the probe’s field of view. This study evaluated the feasibility and accuracy of stitching procedures applied to thyroid volumetric analysis performed using three-dimensional ultrasound (3D-US).Material and methods: Ad hoc thyroid phantoms of different shapes (regular, nodular, thickened isthmus) and volumes (ranging between 50 and 400 mL) were developed. In 15 such phantoms the left and right lobes were separately scanned, and the 3D-US datasets were then assembled (stitched) using predefined landmarks and dedicated software. Volumetric analysis was then assessed via a conventional ellipsoid model (em) and manual tracing (mt). The correlation of measured and reference volumes was determined using Pearson’s correlation coefficients and Bland and Altman limits of agreement.Results: The results showed a high level of agreement (with correlation coefficients ranging from 0.974 to 0.999) for all shapes and volumes tested, including the largest volume of 400 mL. The mt method, although more time consuming, proved superior to the em.Conclusions: Stitching-mediated thyroid volumetric analysis is accurate, and its clinical performance should be investigated in future studies

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

“…Stitching allows the generation of a jointed volume dataset out of several single US scans, leading to an EFOV. The introduced phantom study, using sensor-navigated (sn) US probes, confirmed the feasibility of the method even in large thyroid phantoms (up to 400 mL) [22].…”

“…Therefore, the first purpose of the current study is to investigate whether stitching of two separately acquired 3D-US datasets of large volume thyroid phantoms (with several volume and shape variants) is feasible with ms US probes, too. The previous sn 3D-US study showed very high correlation coefficients between the measured and the reference volumes, revealing superior data for the mt method in comparison to the em approach [22]. Thus, the second aim of this study is to investigate whether similar results for volumetric analyses can be achieved with ms US probes.…”

“…All scans were performed with the Logiq E9 US device (General Electric Medical Systems, Milwaukee, WI, USA). In contrast to the previously published data based on the use of sn US probes [22], ms US probes were applied in the present study. Two different volume probes with incorporated motorized arrays, specifically the convex RAB4-8 probe (C-probe) (fig 2b, 2c, 3a, and 3b) and the linear RSP6-16 probe (L-probe) (fig 2d), were utilized.…”

“…Fifteen water-filled, heart-shaped balloons were created based on previously introduced methods [12,22]. The phantoms were produced with several shape variations in 15 predefined volumes (50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, and 400 mL) ( fig 1).…”

“…by creating extended FOV (EFOV) 3D-US images using optical tracking of a calibrated 3D-US probe which has a 2D transducer array [21]. Another possible solution to overcome the spatial limitations, the post hoc assembly of two or more 3D-US datasets by means of the stitching method, has been recently published [22]. Stitching allows the generation of a jointed volume dataset out of several single US scans, leading to an EFOV.…”