Elsevier

Manual Therapy

Volume 17, Issue 2, April 2012, Pages 187-191
Manual Therapy

Technical and measurement report
Ultrasound transducer shape has no effect on measurements of lumbar multifidus muscle size

https://doi.org/10.1016/j.math.2011.07.001Get rights and content

Abstract

Objective

Evidence is currently lacking for guidance on ultrasound transducer configuration (shape) when imaging muscle to measure its size. This study compared measurements made of lumbar multifidus on images obtained using curvilinear and linear transducers.

Method

Fifteen asymptomatic males (aged 21–32 years) had their right lumbar multifidus imaged at L3. Two transverse images were taken with two transducers (5 MHz curvilinear and 6 MHz linear), and linear and cross-sectional area (CSA) measurements were made off-line. Reliability of image interpretation was shown using intra-class correlation coefficients (0.78–0.99). Muscle measurements were compared between transducers using Bland and Altman plots and paired t-tests. Relationships between CSA and linear measurements were examined using Pearson's Correlation Coefficients.

Results

There were no significant differences (p > 0.05) in the measurements of the two transducers. Thickness and CSA measurements had small differences between transducers, with mean differences of 0.01 cm (SDdiff = 0.21 cm) and 0.03 cm2 (SDdiff = 0.58 cm2) respectively. Width measures had a mean difference of 0.14 cm, with the linear transducer giving larger measures. Significant correlations (p < 0.001) were found between all linear measures and CSA, with both transducers (r = 0.78–0.89).

Conclusion

Measurements of multifidus at L3 were not influenced by the configuration of transducers of similar frequency. For the purposes of image interpretation, the curvilinear transducer produced better definition of the lateral muscle border, suggesting it as the preferable transducer for imaging lumbar multifidus.

Introduction

In recent years ultrasound technology has found widespread application, both in diagnostic use and rehabilitation (Whittaker et al., 2007). Rehabilitative ultrasound imaging (RUSI) can offer a safe, objective and relatively inexpensive means of evaluating muscle and related soft tissue morphology, and can provide visual feedback to aid interventions in research and clinical practice (Whittaker et al., 2007). The RUSI technique has undergone extensive reliability studies, showing high reliability for both taking and interpreting images (Kiesel et al., 2007, Wallwork et al., 2007, Koppenhaver et al., 2009). The validity of RUSI against the gold standard of magnetic resonance imaging (MRI) has also been established for several muscles (Hides et al., 1995, Hides et al., 1996, Lee et al., 2006, O’Sullivan et al., 2009). An area that has received relatively little attention is determining appropriate scanner specifications for imaging muscles and the present study addresses the topic of transducer shape (or configuration).

A curvilinear transducer with an approximate frequency of 5 MHz is commonly used to image lumbar multifidus (Hides et al., 1992, Stokes et al., 2005, Lee et al., 2006, Kiesel et al., 2007), with no justification of transducer choice given. Some guidance based on anecdotal evidence suggested that more sound waves would reach the lateral border of multifidus with a curvilinear transducer (Stokes et al., 2007). It is unknown, however, if the shape of the transducer affects measurements of muscle dimensions. In a recent study, phantom objects were imaged using both curvilinear and linear transducers (Warner et al., 2008). Small differences were found between the two transducer configurations when measuring simulated muscle cross-sectional dimensions using a semi-solid phantom, although these differences were not clinically significant (Warner et al., 2008).

The present study aimed to determine whether there was a difference between measurements made from images of lumbar multifidus muscle obtained using linear and curvilinear transducers. The null hypothesis was that there would be no difference between measurements from images using the two transducers.

Section snippets

Participants

Fifteen males (aged 21–32 years; mean height 180 cm, weight 81.7 kg and body mass index, BMI, 25.5) were recruited from staff and students at the University of Southampton. Exclusion criteria were: extended history of severe lower back pain, any wound or skin condition in the region to be scanned, any previous spinal or pelvic fractures that may interfere with positioning or any known spinal abnormality (such as scoliosis). Ethical approval for the project was obtained from the School of Health

Comparison of measurements from the linear and curvilinear transducers

The t-test analysis showed no significant differences between transducers (Table 2).

The Bland and Altman plots (Fig. 3) showed minimal between-transducer differences. Confidence intervals for the mean difference (d) between transducers were close to zero (Table 2). For thickness (Fig. 3a), d of 0.01cm showed a clear similarity between transducers. The width measurement (Fig. 3b) showed the largest mean difference (0.14 ± 0.3 cm), indicating a bias towards a larger measurement with the linear

Discussion

The main finding indicates that measurements of all three dimensions of multifidus muscle size (thickness, width and CSA) at L3 were not influenced by whether a linear or curvilinear transducer was used, therefore confirming the null hypothesis that measurements would not differ. Intra-rater reliability of measurements on the same images on different days were good to excellent. Linear measures were highly correlated with CSA but thickness, which is most commonly used in the literature, had the

Conclusions

Measurements of multifidus width, thickness and CSA made from images using linear and curvilinear transducers were not significantly different. However, the curvilinear transducer gave better clarity of the lateral muscle border and is therefore recommended as the transducer of choice for ease of interpreting images of the lumbar multifidus. This study highlights the need for research to determine appropriate scanner specifications for RUSI in different muscles and study populations.

Acknowledgements

The authors thank the participants for giving up their time to take part in the study. There were no conflicts of interest within the present study.

References (18)

There are more references available in the full text version of this article.

Cited by (16)

  • Swiss ball enhances lumbar multifidus activity in chronic low back pain

    2015, Physical Therapy in Sport
    Citation Excerpt :

    Ultrasound images (Fig. 1) were obtained by an experienced sonography trained doctor and to establish intra-rater reliability all ultrasound measures were repeated 3 times, within-session, as recommended for optimal reliability by Larivière, Gagnon De Oliveira, Henry Mecheri & Dumas (2013). A Terason t3000 portable ultrasound imaging unit was used, equipped with a 5C2 curvilinear probe, as recommended by previous studies (O'Sullivan, 2000; Richardson & Jull, 1995) and by Worsley, Smith, Warner, and Stoke (2012) as the preferable transducer configuration for producing better defined imaging for lumbar multifidus. Beam width was a standard setting for the ultrasound unit and the frequency was set on ‘high’.

  • Lumbar multifidus muscle thickness does not predict patients with low back pain who improve with trunk stabilization exercises

    2013, Archives of Physical Medicine and Rehabilitation
    Citation Excerpt :

    All subjects performed a contralateral arm-lifting task to activate the LM muscle while this muscle was imaged with RUSI as outlined by Kiesel et al.18 During this task, images of the LM muscle during the relaxed and contracted states were collected, before and after STB treatment, using 1 of 2 ultrasound machines, depending on the availability of the machines: SonoSite 180 portable ultrasound machine with a 5- to 10-MHz linear arraya (n=9) or SonoSite MTurbo ultrasound machine (n=16) with a 2- to 5-MHz curvilinear array.a The type of ultrasound transducer (linear or curvilinear) does not affect measurements of LM-muscle thickness.30 Subjects performed the contralateral arm-lifting task 4 times with the right arm and 4 times with the left arm, for a total of 8 trials.

View all citing articles on Scopus
View full text