Analysis Of Influential Factors In Virtual Touch Tissue Quantification And Its Value In Evaluating Chronic Kidney Disease

Chronic kidney disease (CKD) is a global public health problem. It is crucial to conduct early diagnosis and treatment for CKD because end-stage renal disease may lead to metabolic disorder of multiple systems and needs renal replacement therapy. There is a lack of a noninvasive and sensitive method to evaluate the early change of renal function. Pathologic diagnosis could be got after percutaneous renal biopsy; however, it is not able to reflect the progression of CKD because of its invasive characteristics and the fact that the patients are hard to torrent repeated biopsy. Therefore, we urgently need a noninvasive, safe and convenient method to evaluate the degree of CKD.Virtual touch tissue quantification (VTQ) is a new technology to quantitatively assess tissue stiffness. The fundamental principles are as follows:VTQ technology involves the mechanical excitation of tissue using short-duration acoustic pulses, producing local displacement in the tissue and generating shear-wave propagation away from the region of excitation. The shear wave velocity (SWV, m/s) can be quantified to reflect the tissue elasticity.In the study, we investigated the effect of depth and median to the VTQ imaging by using in vitro porcine tissue, and then analyzed the clinical value of VTQ in assessing chronic kidney disease.Part one:The influential factors of virtual touch tissue quantification in evaluating tissue stiffness:an experimental researchObjective To investigate the influence of different depths and mediums on tissue stiffness measurement by virtual touch tissue quantification technology.Methods Four kinds of in vitro porcine tissue were recruited, three (fat, muscle and liver) were assigned as medium group and three (kidney, liver and muscle) as sample group. The shear wave velocity (SWV) of the samples was measured under different mediums and at different depths (2cm,3cm,4cm and5cm), respectively.Results According to the depth of measurement, two groups of SWV were defined with one group at the depth of2cm and3cm while the other at 4cm and5cm. The difference of SWV between the two groups was of statistical significance and with the increase of the depth SWV values decreased. Even at the same depth, the differences of SWV under different mediums were statistically significant. The tissue SWV measurement decreased with the increase of medium’s acoustic velocity and acoustic impedance.Conclusion Depths and mediums have great influence on evaluating elasticity measurements by virtual touch tissue quantification technology.Part two:The value of virtual touch tissue quantification technology in evaluating chronic kidney diseaseObjective To study the clinical value of virtual touch tissue quantification in evaluating renal cortex stiffness of chronic kidney disease in different staging.Methods There were192patients with chronic kidney disease and112volunteers with normal renal function. The depth of ROI was set from2cm to6.5cm, which was divided into three groups:2.0～3.5cm,3.6-5.0cm and5.1-6.5cm. Shear wave velocities were measured in the lower pole of the right kidney and the differences of SWV among different CKD stages were analyzed. Serum creatinine (SCr) was tested in all patients and the correlation test was conducted between SCr and SWV. Percutaneous needle renal biopsy was performed in130CKD patients and we analyzed the difference of SWV in different pathologic patterns.Results The median of SWV of normal renal cortex in three different depths was2.91m/s,2.82m/s and2.48m/s, respectively. There was statistical difference of SWV not only between depth1and3but also between depth2and3(P=0.003,0.000). There was no statistical difference of SWV between normal group and early stage of CKD, however, there was significantly statistical difference of SWV between normal group and middle to advanced stages, and the median of SWV decreased with the exacerbation of CKD. Slightly negative correlation was measured between SCr and SWV of renal cortex in CKD patients. There was no statistical difference of SWV among different pathologic patterns.Conclusion Virtual touch tissue quantification technology can be used to evaluate the degree of CKD and quantitatively assess the compliance of renal tissue.