Figure 4: B-mode (left) and Superb Micro-vascular Imaging (SMI) (right) images of the same low echogenicity intratesticular lesion as in figure 3. The SMI demonstrates low level intratumoural flow (arrows) that was difficult to appreciate on conventional colour Doppler
.
necrosis; and also one case of non-enhancement within a histologically proven malignant embryonal carcinoma. A new Doppler technique has recently been introduced called Superb Micro-vascular ImagingTM
(Toshiba
Medical Systems Ltd, Crawley, UK), which permits visualisation of very low flow velocity within small vessels, where flow is not detectable with conventional Doppler techniques. This technique does not require the use of ultrasound contrast media (although it can be used in combination) and we have found it valuable to demonstrate the presence of vascularity within lesions, where flow is not readily identified with colour Doppler interrogation (figure 4); however there is currently limited literature available and further research is required to define its role in characterisation of scrotal masses and whether it is able to replace the need for CEUS.
Figure 5 A&B: Colour Doppler image (A) showing a rounded focal abnormality (green arrows) in the anterior aspect of the testis with no blood flow demonstrated within this small lesion. The shear wave image (B) demonstrates the focal lesion (yellow arrow) has similar shear wave velocities to adjacent normal testis parenchyma (red arrow) and is therefore more likely to be benign. This lesion was managed with serial ultrasound surveillance instead of orchidectomy and has been stable on imaging over an 11 month period so far
. -61-
Sonoelastography Elastography is an ultrasound technique which has shown potential for discriminating between benign and malignant lesions in other organs with the assumption that malignant lesions are stiffer than benign. Elastography is established in evaluating liver parenchyma in diffuse liver disease and focal lesions within the breast, thyroid and prostate, but there are few published data regarding its use in assessing testicular lesions. Elastography is a non-invasive technique based on intrinsic tissue elasticity (and how this is altered by the presence of a pathological process) by measuring the amount of deformation caused by a mechanical stress – essentially measuring the 'stiffness' (figure 5). Strain elastography (SE) uses external tissue compression (usually applied by the operator via the ultrasound transducer) to induce the deformation; the resulting image is usually displayed as a colour map showing regions of different stiffness. Shear wave elastography (SWE) does not require the use of manual compression, but instead relies on a measurement of the speed of propagation of a shear wave which travels laterally through the tissue of interest; SWE is therefore able to produce a quantitative measurement of tissue stiffness. Until recently, neither technique was widely used in assessing testicular lesions, with most current literature based around the use of SE. Both teams conclude that the addition of SE to B-mode ultrasound, in the context of an equivocal lesion, offers a further imaging parameter in characterisation. A recent study by Aigner et al9
evaluated 50 intratesticular lesions with a combination of B-mode, colour
Doppler and SE, and quoted a sensitivity of 100%, specificity of 81% and negative predictive value of 100% in diagnosing testicular tumours. Aigner also found 3/50 patients with hard lesions on SE subsequently had benign histology; in particular scarring, infarction or simple cysts may demonstrate increased stiffness (although the diagnosis of cysts should be straightforward on B-mode imaging and therefore not cause diagnostic uncertainty). Goddi et al10
evaluated 144 lesions in 88 testes and quoted an overall sensitivity of
87.5% and specificity of 98.2%, with an overall accuracy of 95.8% in differentiating benign from malignant lesions, performing best in lesions >11mm in size. Grasso et al11
and Pastore et al12 were small studies
evaluating 41 and 27 testicular lesions respectively and, whilst both studies state elastography can provide additional information for small (<10mm) solid intratesticular lesions, both authors conclude further larger studies are required to establish its role.
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