Original contributionReliability of 3-D ultrasound measurements of cervical lymph node volume
Introduction
Assessment of cervical lymph nodes is important to patients with head and neck cancers because it aids treatment planning and prediction of prognosis (van den Brekel et al. 1990; Ishii et al. 1991; Vassallo et al. 1993). Evaluation of posttreatment lymph nodes also helps assessment and monitoring of the treatment responses (Ahuja et al. 1996; van den Brekel et al. 1999). The size of lymph nodes is an important parameter in the assessment of lymph nodes. It is because pathologic lymph nodes tend to be enlarged. In patients with head and neck cancer, increase of nodal size in serial examinations indicates metastases of lymph nodes, whereas decrease in size of lymph nodes after treatment indicates positive response to the treatment (Ahuja et al. 1996; Ahuja and Ying 2003).
High-resolution ultrasound is a common imaging tool for the evaluation of cervical lymphadenopathy (Chang et al. 1990; van den Brekel et al. 1990; Baatenburg de Jong et al. 1991; Bruneton et al. 1994; Baatenburg de Jong et al. 1998). In routine ultrasound evaluation of cervical lymph nodes, nodal size is usually assessed by measuring the transverse diameters of the lymph nodes (Yuasa et al. 2000; Yusa et al. 2000; Ahuja and Ying 2002). However, it has been reported that the evaluation of nodal size by measuring the volume of lymph nodes is more accurate (Dietrich et al. 1997; Dietrich et al. 1999a; Dietrich et al. 1999b; Choi et al. 2001; Lewis et al. 2002). Nevertheless, previous studies assumed lymph nodes to be elliptical in shape and used the ellipsoid formula to calculate the nodal volume (Dietrich et al. 1997; Dietrich et al. 1999a; Dietrich et al. 1999b; Choi et al. 2001; Lewis et al. 2002). Three-dimensional (3-D) ultrasound has been reported to have a high accuracy in volumetric measurement of different structures both in vitro and in vivo (Riccabona et al. 1996; Chang et al. 1997; Chou et al. 1997; Kurjak et al. 2003; Ng et al. 2004; Pang et al. 2005). However, there is scant information about 3-D ultrasound volumetric measurements of cervical lymph nodes (Kim et al. 2002).
Before 3-D ultrasound is routinely used to measure the volume of cervical nodes, it is necessary to understand its reliability of measurements in cervical lymph nodes. Moreover, since 3-D ultrasound requires smooth sweep of scans for accurate measurements, lymph nodes in different regions of the neck have different adjacent structures, which may cause variation of the reliability of measurements. Therefore, this study was undertaken to investigate the reliability of sonographic volumetric measurements of cervical nodes in different regions of the neck.
Compound ultrasound imaging can provide images with a higher resolution when compared with conventional ultrasound (Entrekin et al. 2001; Kern et al. 2004). As high resolution images may allow more accurate outline of the nodal boundaries in 3-D ultrasound and provide more accurate results, the reliability of volumetric measurements of cervical nodes with and without using compound imaging was also compared in the present study.
Section snippets
Materials and methods
A total of fifteen healthy subjects (eight men and seven women), with no history of head and neck surgery, malignancy, tuberculosis, lymphoma, chronic tonsillitis, glandular fever or cardiovascular disease, were recruited in the study. All subjects were Chinese, and the age range of the subjects was 19 to 22 y (mean = 20.6 y). It has been reported that younger healthy subjects have more sonographically detectable cervical lymph nodes than older subjects (Ying et al. 2002). The selection of
Results
In the fifteen subjects, a total of 132 lymph nodes were examined by both operators and were included in the study. In the 132 lymph nodes, there were 10 submental, 29 submandibular, 25 parotid, 28 upper cervical, 7 middle cervical, one lower cervical and 32 posterior triangle nodes. Lymph node was not found in the supraclavicular fossa. Since the number of lymph nodes in the middle and lower cervical regions was low, the statistical calculation may not be reliable in these areas. Therefore,
Discussion
In the present study, results showed that ultrasound images taken with SonoCT® and XRES™ imaging have a higher reproducibility and repeatability than those without using these imaging modes. The finding was similar to that of a previous study which reported that compound ultrasound imaging has a higher reproducibility than conventional ultrasound in carotid plaque surface characterization and plaque echogenicity determination (Kern et al. 2004). With the use of SonoCT® and XRES™ imaging, the
Acknowledgements
This study was supported by a research grant from the Hong Kong Polytechnic University (G-T862).
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