Keywords:
Image verification, Comparative studies, Ultrasound, Neuroradiology peripheral nerve
Authors:
S. Vitali, P. Rossi, G. Aringhieri, T. Bocci, D. Barloscio, M. Santin, F. Sartucci, D. Caramella; Pisa/IT
DOI:
10.1594/ecr2018/C-1508
Methods and materials
To validate this new equipment,
we compared MN images of 10 healthy subjects obtained with VHRUS and HRUS.
We excluded from our sample subjects with bifid median nerve,
with CTS symptoms and diabetes.
The VHRUS equipment used in our study was Vevo MD (Visualsonics,
Toronto,
Canada) with a 70 MHz and 48 MHz linear array transducers.
The HRUS equipment used in our study was MyLab Gamma (Esote,
Genova,
Italia) with a 19 MHz linear array transducer.
In all our 10 healthy volunteers we obtained images of left MN at wrist level with 19 MHz and 70 MHz probes (fig.
2) and at the distal third of the forearm with 19 MHz and 48 MHz probes (fig.
3).
These two specific sites were chosen because they are fundamental in the diagnosis of CTS.
The axial scan of the MN at the inlet of the carpal tunnel is essential because it allows evaluating the inlet cross-sectional area (CSA-I) of the nerve: this parameter is widely used because the swelling of the MN at the inlet of the carpal tunnel is consistently seen in CTS [4].
Furthermore,
the CSA-I measurement also reflects the severity of CTS [4].
Evaluation of the MN at the distal third of the forearm (about 12 cm proximally to the wrist) allows calculating the wrist-to-forearm ratio,
a parameter that has higher specificity in the diagnosis of CTS compared to CSA-I [5] (fig.
4).
The MN area was calculated by continuous tracing of the nerve circumference,
excluding the hyperechoic epineural rim (fig.
5).
We measured nerves' CSA and perimeter obtained from the images acquired with both types of equipment by using a dedicated offline post-processing tool,
Horos [6].
Finally,
we compared the respective values using the Wilcoxon rank sum test performed using R version 1.70 (The R Foundation for Statistical Computing).
As only one Radiologist performed all ultrasound evaluations,
inter-observer reliability was not addressed by this study.