Application of Ultrasound Elastography for Chronic Allograft Dysfunction in Kidney Transplantation

Intensive Surveillance of Porcine-Rhesus Kidney Xenotransplant Using Different Ultrasound Techniques

BACKGROUND

Significant progress has been made in kidney xenotransplantation in the past few years, and this field is accelerating towards clinical translation. Therefore, surveillance of the xenograft with appropriate tools is of great importance. Ultrasonography has been widely used in kidney allotransplantation and served as an economical and non-invasive method to monitor the allograft. However, questions remain whether the ultrasonographic criteria established for human kidney allograft could also be applied in xenotransplantation.

METHODS

In the current study, we established a porcine-rhesus life sustaining kidney xenotransplantation model. The xenograft underwent intensive surveillance using gray-scale, colorful Doppler ultrasound as well as 2D shear wave elastography. The kidney growth, blood perfusion, and cortical stiffness were measured twice a day. These parameters were compared with the clinical data including urine output, chemistry, and pathological findings.

RESULTS

The observation continued for 16 days after transplantation. Decline of urine output and elevated serum creatinine were observed on POD9 and biopsy proven antibody-mediated rejection was seen on the same day. The xenograft underwent substantial growth, with the long axis length increased by 32% and the volume increased by threefold at the end of observation. The resistive index of the xenograft arteries elevated in response to rejection, together with impaired cortical perfusion, while the peak systolic velocity (PSV) was not compromised. The cortical stiffness also increased along with rejection.

CONCLUSION

In summary, the ultrasound findings of kidney xenograft shared similarities with those in allograft but possessed some unique features. A modified criteria needs to be established for further application of ultrasound in kidney xenotransplantation.

Relationship of hemoglobin levels with outcomes in deceased donor kidney transplant: a retrospective cohort study

INTRODUCTION

Anemia is frequent in patients undergoing replacement therapy for kidney failure. Anemia in the pre- and post-transplantation period might be related to kidney transplant outcomes. The current study therefore sought to assess the relationship between anemia, delayed allograft function (DGF), chronic kidney allograft dysfunction (CAD), and death from any cause following kidney transplantation from a deceased donor.

METHODS

This was a retrospective study with 206 kidney transplant patients of deceased donors. We analyzed deceased donors' and kidney transplant patients' demographic data. Moreover, we compared biochemical parameters, anemia status, and medicines between DGF and non-DGF groups. Afterward, we performed a multivariate analysis. We also evaluated outcomes, such as CAD within one year and death in ten years.

RESULTS

We observed a lower frequency of pre-transplant hemoglobin concentration (Hb) but higher frequency of donor-serum creatinine and red blood transfusion within one week after transplantation in the group with DGF. In addition, there was an independent association between Hb concentration before transplantation and DGF [OR 0.252, 95%CI: 0.159-0.401; p < 0.001]. There was also an association between Hb concentration after six months of kidney transplantation and both CAD [OR 0.798, 95% CI: 0.687-0.926; p = 0.003] and death from any cause.

CONCLUSION

An association was found between pre-transplantation anemia and DGF and between anemia six months after transplantation and both CAD and death by any cause. Thus, anemia before or after transplantation affects the outcomes for patients who have undergone kidney transplantation from a deceased donor.

Comparison of resistive index and shear-wave elastography in the evaluation of chronic kidney allograft dysfunction

BACKGROUND

Detection of early chronic changes in the kidney allograft is important for timely intervention and long-term survival. Conventional and novel ultrasound-based investigations are being increasingly used for this purpose with variable results.

AIM

To compare the diagnostic performance of resistive index (RI) and shear wave elastography (SWE) in the diagnosis of chronic fibrosing changes of kidney allograft with histopathological results.

METHODS

This is a cross-sectional and comparative study. A total of 154 kidney transplant recipients were included in this study, which was conducted at the Departments of Transplantation and Radiology, Sindh Institute of Urology and Transplan tation, Karachi, Pakistan, from August 2022 to February 2023. All consecutive patients with increased serum creatinine levels and reduced glomerular filtration rate (GFR) after three months of transplantation were enrolled in this study. SWE and RI were performed and the findings of these were evaluated against the kidney allograft biopsy results to determine their diagnostic utility.

RESULTS

The mean age of all patients was 35.32 ± 11.08 years. Among these, 126 (81.8%) were males and 28 (18.2%) were females. The mean serum creatinine in all patients was 2.86 ± 1.68 mg/dL and the mean estimated GFR was 35.38 ± 17.27 mL/min/1.73 m2. Kidney allograft biopsy results showed chronic changes in 55 (37.66%) biopsies. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of SWE for the detection of chronic allograft damage were 93.10%, 96.87%%, 94.73%, and 95.87%, respectively, and the diagnostic accuracy was 95.45%. For RI, the sensitivity, specificity, PPV, and NPV were 76.92%, 83.33%, 70.17%, and 87.62%, respectively, and the diagnostic accuracy was 81.16%.

CONCLUSION

The results from this study show that SWE is more sensitive and specific as compared to RI in the evaluation of chronic allograft damage. It can be of great help during the routine follow-up of kidney transplant recipients for screening and early detection of chronic changes and selecting patients for allograft biopsy.

Ultrasound elastography in chronic kidney disease: a systematic review and meta-analysis

Ultrasound elastography (USE) is a noninvasive technique for assessing tissue elasticity, and its application in nephrology has aroused growing interest in recent years. The purpose of this article is to systematically review the clinical application of USE in patients with chronic kidney disease (CKD), including native and transplanted kidneys, and quantitatively investigate differences in elasticity values between healthy individuals and CKD patients. Furthermore, we provide a qualitative analysis of the studies included, discussing the potential interplay between renal stiffness, estimated glomerular filtration rate, and fibrosis. In January 2022, a systematic search was carried out on the MEDLINE (PubMed) database, concerning studies on the application of USE in patients with CKD, including patients with transplanted kidneys. The results of the included studies were extracted by two independent researchers and presented mainly through a formal narrative summary. A meta-analysis of nine study parts from six studies was performed. A total of 647 studies were screened for eligibility and, after applying the exclusion and inclusion criteria, 69 studies were included, for a total of 6728 patients. The studies proved very heterogeneous in terms of design and results. The shear wave velocity difference of - 0.82 m/s (95% CI: - 1.72-0.07) between CKD patients and controls was not significant. This result agrees with the qualitative evaluation of included studies that found controversial results for the relationship between renal stiffness and glomerular filtration rate. On the contrary, a clear relationship seems to emerge between USE values and the degree of fibrosis. At present, due to the heterogeneity of results and technical challenges, large-scale application in the monitoring of CKD patients remains controversial.

Machine Learning-Based Ultrasound Radiomics for Evaluating the Function of Transplanted Kidneys

The aim of the study described here was to investigate the value of different machine learning models based on the clinical and radiomic features of 2-D ultrasound images to evaluate post-transplant renal function (pTRF). We included 233 patients who underwent ultrasound examination after renal transplantation and divided them into the normal pTRF group (group 1) and the abnormal pTRF group (group 2) based on their estimated glomerular filtration rates. The patients with abnormal pTRF were further subdivided into the non-severe renal function impairment group (group 2A) and the severe impairment group (group 2B). The radiomic features were extracted from the 2-D ultrasound images of each case. The clinical and ultrasound image features as well as radiomic features from the training set were selected, and then five machine learning algorithms were used to construct models for evaluating pTRF. Receiver operating characteristic curves were used to evaluate the discriminatory ability of each model. A total of 19 radiomic features and one clinical feature (age) were retained for discriminating group 1 from group 2. The area under the receiver operating characteristic curve (AUC) values of the models ranged from 0.788 to 0.839 in the test set, and no significant differences were found between the models (all p values >0.05). A total of 17 radiomic features and 1 ultrasound image feature (thickness) were retained for discriminating group 2A from group 2B. The AUC values of the models ranged from 0.689 to 0.772, and no significant differences were found between the models (all p values >0.05). Machine learning models based on clinical and ultrasound image features, as well as radiomics features, from 2-D ultrasound images can be used to evaluate pTRF.

Shear wave elastography and Doppler ultrasound in kidney transplant recipients

Objective

To evaluate the association between shear wave elastography parameters and arterial resistance in kidney transplant recipients.

Materials and Methods

This was a prospective cross-sectional study involving consecutive adult kidney transplant recipients. All patients underwent color Doppler to evaluate the resistive index (RI) and ultrasound shear wave elastography for the quantification of renal allograft stiffness.

Results

We evaluated 55 patients, of whom 9 (16.4%) had an RI defined as abnormal (≥ 0.79) and 46 (83.6%) had an RI defined as normal (< 0.79). The mean age was higher in the abnormal RI group than in the normal RI group (68.0 ± 8.6 years vs. 42.6 ± 14.1 years; p < 0.001), as was the mean shear wave velocity (2.6 ± 0.4 m/s vs. 2.2 ± 0.4 m/s; p = 0.013). Multivariate analysis identified two independent predictors of arterial resistance: age (OR = 1.169; 95% CI: 1.056 to 1.294; p = 0.003) and shear wave velocity (OR = 17.1; 95% CI: 1.137 to 257.83; p = 0.040).

Conclusion

We observed an association between rigidity in the cortex of the transplanted kidney, as evaluated by shear wave elastography, and arterial resistance, as evaluated by color Doppler, in kidney transplant recipients.

Artificial Intelligence Assessment of Renal Scarring (AIRS Study)

Background

The goal of the Artificial Intelligence in Renal Scarring (AIRS) study is to develop machine learning tools for noninvasive quantification of kidney fibrosis from imaging scans.

Methods

We conducted a retrospective analysis of patients who had one or more abdominal computed tomography (CT) scans within 6 months of a kidney biopsy. The final cohort encompassed 152 CT scans from 92 patients, which included images of 300 native kidneys and 76 transplant kidneys. Two different convolutional neural networks (slice-level and voxel-level classifiers) were tested to differentiate severe versus mild/moderate kidney fibrosis (≥50% versus <50%). Interstitial fibrosis and tubular atrophy scores from kidney biopsy reports were used as ground-truth.

Results

The two machine learning models demonstrated similar positive predictive value (0.886 versus 0.935) and accuracy (0.831 versus 0.879).

Conclusions

In summary, machine learning algorithms are a promising noninvasive diagnostic tool to quantify kidney fibrosis from CT scans. The clinical utility of these prediction tools, in terms of avoiding renal biopsy and associated bleeding risks in patients with severe fibrosis, remains to be validated in prospective clinical trials.

Renal elastography measurements in children with acute glomerulonephritis

PURPOSE

The aim of this study was to compare the acoustic radiation force impulse elastography (ARFI-e) values of the renal cortical parenchyma in children with acute glomerulonephritis (AGN) and healthy children, and to determine a cut-off point for the diagnosis of AGN.

METHODS

This prospective study included 30 children with biopsy-proven AGN and 30 healthy children. All the children underwent renal ARFI-e measurements. Values were obtained from the upper, middle, and lower zones of the right kidney parenchyma. A total of nine ARFI-e measurements (three from each zone) were made. Statistical analyses were conducted of the mean elastography values (MEVs) of the children in both groups.

RESULTS

In the patient group, the MEVs measured from the upper, middle and lower zones of the right kidney were 3.42±0.42 m/s, 3.45±0.45 m/s, and 3.39±0.39 m/s (average, 3.42±0.34 m/s), respectively. In the healthy control group, the MEVs measured from the upper, middle, and lower zones of the right kidney were 2.85±0.63 m/s, 2.85±0.68 m/s, and 2.86±0.66 m/s (average, 2.85±0.57 m/s), respectively. The MEVs in all zones were significantly higher in the patient group than in the healthy group (P<0.001). The cut-off values determined to predict AGN in the upper, middle, and lower zones of the kidney were 2.74 m/s (sensitivity, 96.67%; specificity, 46.67%), 2.71 m/s (sensitivity, 96.67%; specificity, 53.33%), and 2.81 m/s (sensitivity, 93.33%; specificity, 56.67%), respectively.

CONCLUSION

The ARFI-e technique can be considered as a non-invasive, easily applicable, auxiliary method for the early diagnosis of AGN.

Novel Uses of Ultrasound to Assess Kidney Mechanical Properties

Ultrasound is a key imaging tool for evaluating the kidney. Over the last two decades, methods to measure the mechanical properties of soft tissues have been developed and used in clinical practice, although use in the kidney has not been as widespread as for other applications. The mechanical properties of the kidney are determined by the structure and composition of the renal parenchyma and perfusion characteristics. Because pathologic processes change these factors, the mechanical properties change and can be used for diagnostic purposes and for monitoring treatment or disease progression. Ultrasound-based elastography methods for evaluating the mechanical properties of the kidney use focused ultrasound beams to perturb the kidney and then high frame-rate ultrasound methods are used to measure the resulting motion. The motion is analyzed to estimate the mechanical properties. This review will describe the principles of these methods and discuss several seminal studies related to characterizing the kidney. Additionally, an overview of the clinical use of elastography methods in native and kidney allografts will be provided. Perspectives on future developments and uses of elastography technology along with other complementary ultrasound imaging modalities will be provided.

Feasibility of Harmonic Motion Imaging Using a Single Transducer: In Vivo Imaging of Breast Cancer in a Mouse Model and Human Subjects

Harmonic motion imaging (HMI) interrogates the mechanical properties of tissues by simultaneously generating and tracking harmonic oscillation using focused ultrasound and imaging transducers, respectively. Instead of using two transducers, the objective of this work is to develop a single transducer HMI (ST-HMI) to both generate and track harmonic motion at "on-axis" to the force for facilitating data acquisition. In ST-HMI, the amplitude-modulated force was generated by modulating excitation pulse duration and tracking of motion was performed by transmitting tracking pulses interleaved between excitation pulses. The feasibility of ST-HMI was performed by imaging two elastic phantoms with three inclusions (N = 6) and comparing it with acoustic radiation force impulse (ARFI) imaging, in vivo longitudinal monitoring of 4T1, orthotropic breast cancer mice (N = 4), and patients (N = 3) with breast masses in vivo. Six inclusions with Young's moduli of 8, 10, 15, 20, 40, and 60 kPa were embedded in a 5 kPa background. The ST-HMI-derived peak-to-peak displacement (P2PD) successfully detected all inclusions with [Formula: see text] of the linear regression between the P2PD ratio of background to inclusion versus Young's moduli ratio of inclusion to background. The contrasts of 10 and 15 kPa inclusions were higher in ST-HMI than ARFI-derived images. In the mouse study, the median P2PD ratio of tumor to non-cancerous tissues was 3.0, 5.1, 6.1, and 7.7 at 1, 2, 3, and 4 weeks post-injection of the tumor cells, respectively. In the clinical study, ST-HMI detected breast masses including fibroadenoma, pseudo angiomatous stromal hyperplasia, and invasive ductal carcinoma with a P2PD ratio of 1.37, 1.61, and 1.78, respectively. These results indicate that ST-HMI can assess the mechanical properties of tissues via generation and tracking of harmonic motion "on-axis" to the ARF. This study is the first step towards translating ST-HMI in clinics.

Klotho Regulates Epithelial-to-Mesenchymal Transition In Vitro via Wnt/β-Catenin Pathway and Attenuates Chronic Allograft Dysfunction in a Rat Renal Transplant Model

Background

Klotho deficiency has been implicated in various kidney diseases and has been associated with renal fibrosis. However, the role of Klotho in renal allograft fibrosis still remains undetermined.

Material/Methods

A 24-week-old rat renal transplant model with chronic allograft dysfunction (CAD) was carried out by orthotopic kidney transplantation using F344 donor rats to Lewis recipient rats. Successful establishment of the model was verified by HE and Masson staining and renal allograft function assessment. HK-2 cells were cultured and treated with TGF-β1 and/or siRNA-Klotho at various time points. Total proteins and RNA were extracted from the cultured cells and kidney tissues. Western blot assay and quantitative RT-PCR were used to analyze the expression of Klotho, fibronectin, and β-catenin pathways.

Results

We successfully established and identified a 24-week-old rat renal transplant model with CAD. Loss of Klotho was identified to be associated with epithelial-to-mesenchymal transition (EMT), renal allograft fibrosis, and CAD. In HK-2 cells, a significant decrease of Klotho protein was observed in the renal fibrosis induced by TGF-β1 in a time-dependent manner. Moreover, intervention of siRNA-Klotho remarkably promoted the progression of renal fibrosis and activation of the Wnt/β-catenin signaling pathway.

Conclusions

Our results show that Klotho has a significant protective role against EMT, renal allograft fibrosis, and CAD following kidney transplantation, which is mediated by inhibition of the Wnt/β-catenin signaling pathway.

Electronic Point Spread Function Rotation Using a Three-Row Transducer for ARFI-Based Elastic Anisotropy Assessment: In Silico and Experimental Demonstration

Degree of anisotropy (DoA) of mechanical properties has been assessed as the ratio of acoustic radiation force impulse (ARFI)-induced peak displacements (PDs) achieved using spatially asymmetric point spread functions (PSFs) that are rotated 90° to each other. Such PSF rotation has been achieved by manually rotating a linear array transducer, but manual rotation is cumbersome and prone to misalignment errors and higher variability in measurements. The purpose of this work is to evaluate the feasibility of electronic PSF rotation using a three-row transducer, which will reduce variability in DoA assessment. A Siemens 9L4, with 3×192 elements, was simulated in Field II to generate spatially asymmetric ARFI PSFs that were electronically rotated 63° from each other. Then, using the finite element method (FEM), PD due to the ARFI excitation PSFs in 42 elastic, incompressible, transversely isotropic (TI) materials with shear moduli ratios of 1.0-6.0 were modeled. Finally, the ratio of PDs achieved using the two rotated PSFs was evaluated to assess elastic DoA. DoA increased with increasing shear moduli ratios and distinguished materials with 17% or greater difference in shear moduli ratios (Wilcoxon, ). Experimentally, the ratio of PDs achieved using ARFI PSF rotated 63° from each other distinguished the biceps femoris muscle from two pigs, which had median shear moduli ratios of 4.25 and 3.15 as assessed by shear wave elasticity imaging (SWEI). These results suggest that ARFI-based DoA assessment can be achieved without manual transducer rotation using a three-row transducer capable of electronically rotating PSFs by 63°. It is expected that electronic PSF rotation will facilitate data acquisitions and improve the reproducibility of elastic anisotropy assessments.

Advances of Contrast-Enhanced Ultrasonography and Elastography in Kidney Transplantation: From Microscopic to Microcosmic

Kidney transplantation is the best choice for patients with end-stage renal disease. To date, allograft biopsy remains the gold standard for revealing pathologic changes and predicting long-term outcomes. However, the invasive nature of transplant biopsy greatly limits its application. Ultrasound has been a first-line examination for evaluating kidney allografts for a long time. Advances in ultrasound in recent years, especially the growing number of studies in elastography and contrast-enhanced ultrasonography (CEUS), have shed new light on its application in kidney transplantation. Elastography, including strain elastography and shear wave elastography, is used mainly to assess allograft stiffness and, thus, predict renal fibrosis. CEUS has been used extensively in evaluating blood microperfusion, assessing acute kidney injury and detecting different complications after transplantation. Requiring the use of microbubbles also makes CEUS a novel method of gene transfer and drug delivery, enabling promising targeted diagnosis and therapy. In this review, we summarize the advances of elastography and CEUS in kidney transplantation and evaluate their potential efficiency in becoming a better complement to or even substitute for transplant biopsy in the future.

Comparison of placental elasticity in normal and intrauterine growth retardation pregnancies by ex vivo strain elastography

OBJECTIVE

To compare the placental elasticity in fetuses with or without intrauterine growth restriction (IUGR).

MATERIALS AND METHODS

One hundred pregnant women (50 IUGR and 50 healthy) with anteriorly located placenta were evaluated during the third trimester of pregnancy. Measurements were carried out by a machine that has a real-time elastographic ultrasonography feature. After obtaining the optimum image, three areas (subcutaneous tissue, center, and the edge of the placenta) were provided to identify the placental strain values. Then, the placental strain ratio (PSR) value was calculated automatically. Two groups compared in terms of their PSR values.

RESULTS

There was a significant difference in placental elasticity between the groups (P < 0.001). PSR value was 2.8 ± 1.2 in the IUGR group and 1.3 ± 0.6 in the control group. A PSR value of 1.78 had an 86% sensitivity (OR 4.3) and 80% specificity (OR 0.17) in IUGR cases. The positive predictive value was 81.1% and the negative predictive value was 85.1% for this cut-off value.

CONCLUSIONS

We have shown that placental strain ratio is increased during the third trimester of pregnancy in fetuses with IUGR. Increased stiffness and elasticity may be responsible for the onset of IUGR in some cases.

The effect of placental elasticity on intraoperative bleeding in pregnant women with previous cesarean section

Background We aimed to evaluate the efficiency of placental elasticity in predicting the amount of intraoperative bleeding via real-time tissue elastography technique. Methods Pregnant women in the third trimester of pregnancy who had planned delivery via cesarean section due to the recurrent cesareans were enrolled in the research (n = 78). Elastographic measurements of placental tissues of all cases were carried out by real-time elastographic ultrasonography. It is a tissue elastography software (Esaote MyLabSeven) that uses a 8-1-MHz multifrequency AC2541 Probe. Results A significant relationship was found between placental elasticity and intraoperative bleeding. There was a significant correlation between alterations in the preoperative and postoperative hemoglobin (Hb) and hematocrit (Hct) levels and placental strain ratio (SR) (P < 0.001, r: 0.831; P < 0.001, r: 0.733, respectively). Conclusion These findings may reflect an alteration at the tissue elasticity level. We hope that the use of real-time elastographic ultrasonography technique may give an idea about the amount of bleeding during the cesarean section.

Shear-Wave Elastography Variability Analysis and Relation with Kidney Allograft Dysfunction: A Single-Center Study

Shear-wave elastography (SWE) showed the absence or presence of significant differences among stable kidney allograft function and allograft dysfunction. We evaluated the variability of kidney allograft stiffness in relation to allograft dysfunction, respectively, in terms of a correlation of stiffness with patients' characteristics. A single-center prospective study on patients who had undergone renal transplantation was conducted between October 2017 and November 2018. Patients were clinically classified as having a stable allograft function or allograft dysfunction. SWE examinations performed by the same radiologist with a LOGIQ E9 were evaluated. Ten measurements were done for Young's modulus (kPa) at the level of allograft cortex and another ten at the level of medulla. Eighty-three SWE examinations from 63 patients, 69 stable allografts, and 14 allografts with dysfunction were included in the analysis. The intra-examinations stiffness showed high variability, with the quantile covariation coefficient ranging from 2.21% to 45.04%. The inter-examinations stiffness showed heterogeneity (from 28.66% to 42.38%). The kidney allograft cortex stiffness showed significantly higher values in cases with dysfunction (median = 28.70 kPa, interquartile range (IQR) = (25.68-31.98) kPa) as compared to those with stable function (median = 20.99 kPa, interquartile range = (16.08-27.68) kPa; p-value = 0.0142). Allograft tissue stiffness (both cortex and medulla) was significantly negatively correlated with body mass index (-0.44, p-value < 0.0001 for allograft cortex and -0.42, p-value = 0.0001 for allograft medulla), and positively correlated with Proteinuria/Creatinuria ratio (0.33, p-value = 0.0021 for allograft cortex and 0.28, p-value = 0.0105 for allograft medulla) but remained statistically significant only in cases with stable function. The cortical tissue stiffness proved significantly higher values for patients with allograft dysfunction as compared to patients with stable function, but to evolve as an additional tool for the evaluation of patients with a kidney transplant and to change the clinical practice, more extensive studies are needed.

Biomarkers of Chronic Renal Tubulointerstitial Injury

Progression of renal parenchyma injury is characterized by increasing interstitial fibrosis and tubular atrophy, irrespective of the cause. Histopathologic assessment of renal tissue obtained by biopsy remains the gold standard for determining the presence and extent of tubulointerstitial scarring. Discovery of robust non-invasive means for capturing a snapshot and for longitudinal monitoring of parenchymal deterioration has been the focus of intense multimodal effort by investigators within the renal community and beyond. Research in this field has included the use of in vitro and in vivo experimental models and has fostered the development and evaluation of tissue and biofluid assays for novel analytes with potential translation to the diagnosis and prognosis of kidney disease. Here, we examine recent advances in the search of "biomarkers" for detection of renal tubulointerstitial scarring and prediction of renal outcome in human renal disease.

Strain wave elastography in response assessment to neo-adjuvant chemotherapy in patients with locally advanced breast cancer

OBJECTIVE

The study was conducted to study the role of strain wave elastography in evaluating the response to neo-adjuvant chemotherapy (NACT) in patients with locally advanced breast cancer (LABC).

METHODS

In this Institutional review board approved study, 86 patients of LABC were investigated with strain wave elastography. Females receiving NACT had the affected breast scanned by strain wave elastography before each cycle of chemotherapy and immediately before surgery by two independent observers. Changes in elastographic parameters (size ratio, strain ratio) were documented and then compared to clinical and pathologic tumor response as evaluated after mastectomy.

RESULTS

Elastographic strain ratio parameters demonstrated high sensitivity and moderate specificity for determining response even after the first cycle of neo-adjuvant chemotherapy [97.7% sensitivity (Sn), 68.7% specificity (Sp)]. Elastographic size ratio parameters showed moderate sensitivity and specificity for response detection after second and third cycle of neo-adjuvant chemotherapy (Sn, Sp: after second cycle of NACT Sn 83.3% Sp 80%; after third cycle of NACT Sn 77.8% Sp 100%).

CONCLUSION

Strain ratio is the earliest predictor of treatment response in patients of LABC. Serial imaging with elastography has the potential to predict treatment response early during the course of NACT, which may prove vital in management of patients with breast cancer.

ADVANCES IN KNOWLEDGE

Strain wave elastography is a powerful tool to predict chemoresponse early during the course of management, thereby providing an optimal window to change treatment protocols.

Ultrasound Elastography Evaluations in Patient Populations With Various Kidney Diseases

Renal elastography is an ultrasonographic method that has been recently found to provide information on renal functions and fibrosis. In this study, we aimed to investigate the relationship between elastography scores and renal functions and proteinuria levels in patient populations with various kidney diseases. Seventy-five diabetic nephropathy patients, 66 kidney transplant patients, and 45 glomerulonephritis patients were included in the study. The amount of proteinuria was measured according to the protein-to-creatinine ratio in spot urine samples. The estimated glomerular filtration rate (eGFR) was calculated according to the Modification of Diet in Renal Disease formula. Ultrasound elastography scores were measured in each patient group by a radiologist. The mean age of diabetic nephropathy patients was 61 ± 10 years. The mean elastography score was 0.96 ± 0.30. Elastography score was positively correlated with serum blood urea nitrogen and creatinine levels and was negatively correlated with eGFR value. The mean age of kidney transplant patients was 42 ± 12 years. The mean elastography score was 1.10 ± 0.38. There was a significant relationship between elastography score and proteinuria level. The mean age of glomerulonephritis patients was 37 ± 13 years. The mean elastography score was 0.91 ± 0.41. Elastography score was positively correlated with serum blood urea nitrogen and creatinine levels. However, there was no relationship between elastography score and eGFR value and proteinuria level. Although renal elastography provides information on renal functions and proteinuria in patients with diabetic nephropathy, renal transplant, and glomerulonephritis, there is a need for studies with a larger number of patients on this subject.

Advanced ultrasound applications in the assessment of renal transplants: contrast-enhanced ultrasound, elastography, and B-flow

Ultrasound is routinely used as the first imaging exam for evaluation of renal transplants and can identify most major surgical complications and evaluate vascularity with color Doppler. Ultrasound is limited, however, in the detection of parenchymal disease processes and Doppler evaluation is also prone to technical errors. Multiple new ultrasound applications have been developed and are under ongoing investigation which could add additional diagnostic capability to the routine ultrasound exam with minimal additional time, cost, and patient risk. Contrast-enhanced ultrasound (CEUS) can be used off-label in the transplant kidney, and can assist in detection of infection, trauma, and vascular complications. CEUS also can demonstrate perfusion of the transplant assessed quantitatively with generation of time-intensity curves. Future directions of CEUS include monitoring treatment response and microbubble targeted medication delivery. Elastography is an ultrasound application that can detect changes in tissue elasticity, which is useful to diagnose diffuse parenchymal disease, such as fibrosis, otherwise unrecognizable with ultrasound. Elastography has been successfully applied in other organs including the liver, thyroid, and breast; however, it is still under development for use in the transplant kidney. Unique properties of the transplant kidney including its heterogeneity, anatomic location, and other technical factors present challenges in the development of reference standard measurements. Lastly, B-flow imaging is a flow application derived from B-mode. This application can show the true lumen size of a vessel which is useful to depict vascular anatomy and bypasses some of the pitfalls of color Doppler such as demonstration of slow flow.