Shear wave elastography with VTIQ: A new tool to diagnose parathyroid adenomas
Sheer wave elastography (SWE) using Virtual Touch Imaging Quantification (VTIQ) shows promise as a new tool for diagnosing parathyroid adenomas, according to research published in the European Journal of Radiology. Diagnostic imaging is used to localize these noncancerous tumors of the parathyroid gland prior to minimally invasive surgery.
Ultrasound is increasingly being used in lieu of Technetium 99m Sestamibi Scintigraphy (MIBI) scans due to improved image quality. VTIQ, a recently available 2D-shear wave technology generated by acoustic radiation force impulse, is capable of creating shear wave image and subsequent tissue quantification in one display. Using image-based localization and acoustic radiation force impulse technology, the sheer wave speed may be quantified in a precise anatomical region focused on a region of interest (ROI) with a predefined 1.5 mm size provided by the system. The VTIQ image is a color-coded display of relative shear wave velocities within the user defined ROI superimposed on a conventional B-mode ultrasound image. VTIQ is capable for four discrete shear wave display maps that show velocity, quality, travel time, and displacement.
Lead author Ghobad Azizi, MD, an endocrinologist at Wilmington Endocrinology in Wilmington, NC, and co-authors conducted a study to prospectively determine SWE characteristics of parathyroid adenomas using the VTIQ technology. The study cohort of 57 patients had biologically confirmed primary hypoparathyroidism and a possible solitary parathyroid adenoma seen on an initial ultrasound scan. Adenomas were confirmed by MIBI, fine needle aspiration, or surgical resection.
For the study, each patient had a subsequent exam that included conventional ultrasound and SWE performed using a single ultrasound system (Acuson 3000, Siemens Medical Systems, Mountain View, CA). Both sets of images were analyzed and compared. The median shear wave velocity for all parathyroid adenomas was 2.02 m/s and was 2.77 m/s for thyroid tissue. The shear wave velocity of the adenomas was independent of adenoma size, serum parathyroid hormone concentration, or plasma parathyroid hormone concentration. Details are reported in the article, which also includes a list of shear wave velocity comparisons. The authors believe that knowledge of shear wave velocity for a specific tissue can help in the identification of the tissue.
In addition to determining that tissue elasticity of parathyroid adenoma is significantly lower than thyroid tissue, the authors reported that parathyroid adenomas appear to have a more homogenous texture and lower tissue stiffness when compared with thyroid gland. Adenomas have a distinct location, frequently in the posterior/inferior aspect of thyroid gland and an elongated form with very hypoechoic texture on ultrasound. The authors also stated that a distinct vascularity pattern suggestive of polar vessel sign could help identify candidates for parathyroid adenoma when combined with other B-mode features, but they cautioned that the ability to visualize polar vessel sign depends on the quality of the ultrasound machine and the experience of the sonographer.
REFERENCE
- Azizi G, Piper K, Keller JM, et al. Shear wave elastography and parathyroid adenoma: A new tool for diagnosing parathyroid adenomas. Eur J Radiol. 2016 85;9: 1586-1593