Accuracy of Ultrasound Measurements for Skull Bone Thickness Using Coded Signals

Abstract

The knowledge of skull bone thickness would be helpful for a great variety of surgical interventions of the head. Ultrasound (US) can offer this information intraoperatively in real time. A-mode US measurements of skull bone thickness were performed with different pulse characteristics: 1) in water and 2) by directly coupling a 2.25-MHz US transducer integrated in a handpiece with a soft delay line using coded excitation (CE) (SonoPointer). Mechanical measurements by calipers served as controls. The specimen were 16 nonselected human cadaveric skull bones preserved with formaldehyde. The average difference between the bone thickness measured by the SonoPointer and the mechanical control measurements was 0.04 +/- 0.62 mm. The 95% limits of agreement between the two methods were -1.18 and 1.25 mm. However, even the gold standard of two repeated caliper measurements had limits of agreement of -0.4 and 0.42 mm. Using a standard US pulse in water, only 62.5% sample points were measurable, whereas the SonoPointer produced the thickness measurement in 97.9% of points. CE proved to be superior to single burst or needle US pulses. A-mode US measurements of skull bone thickness using the SonoPointer are feasible. It may provide valuable information on skull bone thickness, e.g., for osteosynthesis, calvarial split bone harvesting, implantation of hearing devices, osseointegrated titanium fixtures, and skull base surgery.

Analyse der Regelungsstrategien eines Osteotomie-Instruments auf Basis multimodaler Informationen / Analysis of the Control Strategies of an Instrument for Osteotomy on the Basis of Multimodal Information

“…Einen wesentlich größeren Einfluss auf die Ultraschallmessung hat dagegen die Genauigkeit, mit der die Schallgeschwindigkeit des Knochens bestimmt wurde. Tretbar et al [23] …”

System architecture of ultrasound-based real-time bone thickness determination for synergistically operated cutting tools

“…However, this option decreases the pulse repetition rate and limits the real-time abilities of the entire system. Another option for SNR improvement is the use of coded excitation ultrasound [6,10]. However, the commonly used long signal sequences (e.g.…”

“…with Speed of sound inside of the probe For this calculation, the exact determination of the speed of sound is important to avoid thickness measurement errors, which could cause unwanted injuries of the patient [6]. The recording time for each echo signal was 51 µs, which should be sufficient to obtain bone echoes in a depth of approximately 11mm.…”

“…Whereas the cutting depth of this tool can be adjusted in real-time on the basis of optical position tracking and pre-operative a-priori data (computed tomography, magnet resonance tomography) [5], additional redundant or stand-alone online information in terms of intra-operatively performed bone thickness measurements is still not available. Coded excitation ultrasound (CE) for bone thickness measurement has been in principle discussed in the literature [6,7]. However, the real-time aspect as well as the synergistic interaction of the ultrasound components in the context of such a hand-guided cutting tool has not yet been investigated.…”

Measurement of Skull Bone Thickness for Bone-Anchored Hearing Aids

“…1). By using coded signals and a matched filter technique, this system is able to easily measure skull bone thickness of up to approximately 10 mm (22,23).…”