Tissue Pulsatility Index: A New Parameter to Evaluate Renal Transplant Perfusion

Limited Accuracy of Colour Doppler Ultrasound Dynamic Tissue Perfusion Measurement in Diabetic Adults

Dynamic tissue perfusion measurement (DTPM) is a pre-described and available method in pediatric ultrasound to quantify tissue perfusion in renal Doppler ultrasound by particular video analysis software. This study evaluates DTPM during single and between repeated visits after 6 months, calibrates repeated DTPM within different region of interest (ROI) and compares DTPM with kidney function markers in adult patients with early diabetic nephropathy (n = 17). During repeated measurements, no association of readings at the same patients in the same (n = 3 readings) as well as repeated visit (n = 2 visits) could be retrieved. No association between DTPM, MDRD-GFR, albuminuria, age and duration of diabetes was observed. These negative results are presumably related to inconsistency of DTPM due to non-fixed ROI position as could be shown in calibrating series. Further development of the method should be performed to enable reproducible DTPM readings in adults.

Utility of maximum perfusion intensity as an ultrasonographic marker of intraneural blood flow

We quantified intraneural blood flow (INBF) using perfusion measurement software (PixelFlux), and compared it with the qualitative method of counting blood vessels (vessel score) in a cohort of carpal tunnel syndrome (CTS) patients.

METHODS

Forty-seven patients (67 wrists) with a clinical and electrophysiological diagnosis of CTS, and 20 healthy controls (40 wrists) were enrolled. Median nerve ultrasound (US) was performed at the carpal tunnel inlet to measure the cross-sectional area (CSA) and vessel score. Power Doppler sonograms from nerves with detectable INBF were processed with PixelFlux to obtain the maximum perfusion intensity (MPI).

RESULTS

Forty-nine percent of CTS patients had detectable INBF compared with none in the control group (P < 0.0001). MPI correlated significantly with vessel score (r = 0.945, P < 0.0001), CSA (r = 0.613, P < 0.0001), and electrophysiological severity (r = 0.440, P < 0.0001). MPI had higher intra- or interobserver reliability compared with vessel score (0.95 vs. 0.47).

CONCLUSION

MPI is a better method for quantification of INBF. Muscle Nerve, 2016 Muscle Nerve 55: 77-83, 2017.

Color Doppler dynamic tissue perfusion measurement: a novel tool in the assessment of renal parenchymal perfusion in children with vesicoureteral reflux

INTRODUCTION

Vesicoureteral reflux (VUR) occurs in 20-50% of children suffering from recurrent urinary tract infections (UTIs) and is associated with an increased risk of renal scarring and impaired renal function. Early detection of renal perfusion deterioration would allow for the implementation of more aggressive treatment and potentially prevent further damage to the renal parenchyma. The aim of the study was to assess renal parenchymal perfusions in children with recurrent UTIs with and without coexisting VUR, and compare the findings with the results of healthy patients.

MATERIAL AND METHODS

Color Doppler sonographic dynamic renal parenchymal perfusion measurements were performed with PixelFlux (Chameleon-Software, Germany) software in 77 children with recurrent UTIs and coexisting VUR and in 30 children with UTIs without VUR. The findings were compared with the results of 53 healthy children.

RESULTS

Cortical parenchymal perfusion of children suffering from UTIs and VUR was significantly reduced when compared to the control group. Statistically significant differences (p < 0.05) were found in all perfusion parameters (i.e. mean velocity (v mix ), mean perfused area (A mix ), mean perfusion intensity (I mix ), tissue pulsatility index (TPI), and tissue resistance index (TRI)) between the control group and children suffering from UTIs and VUR, particularly VUR grades III and IV. There were no significant differences between the UTI group and the control group. No differences were found between the controls and VUR grade II.

CONCLUSIONS

Renal parenchymal perfusion decreases significantly with higher grades of VUR.

Umbilical vein vasomotion detected in vivo by serial three-dimensional pixelwise spatially angle-corrected volume flow measurements

OBJECTIVE

To explore changes in volume flow in the umbilical vein in healthy second-trimester fetuses.

METHODS

This was a prospective observational pilot study performed at Stavanger University Hospital, Norway, between May and October 2013. Serial three-dimensional ultrasound recordings from the umbilical vein were acquired every 30 s in a 5-min period in 43 fetuses at 17-20 weeks' gestation. The recordings were analyzed with pixelwise spatially angle-corrected volume flow measurements.

RESULTS

We observed variation in the umbilical vein volume flow in all fetuses, ranging from a mean minimum of 1.01 mL/s to a mean maximum of 2.60 mL/s. The minimum of all measurements was 57% compared with the mean value and the maximum was 148% of the mean value. The individual flow volume measurements ranged between 0.11 and 4.14 mL/s (mean, 1.76 mL/s). Within this range, an undulating course of all perfusion parameters was observed, with a full period of 4-5 min duration.

CONCLUSION

Healthy second-trimester fetuses show cyclical variation in blood flow in the umbilical vein. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Color-Doppler sonographic tissue perfusion measurements reveal significantly diminished renal cortical perfusion in kidneys with vesicoureteral reflux

Vesicoureteral reflux (VUR) and its sequelae may lead to reduced renal perfusion and loss of renal function. Methods to describe and monitor tissue perfusion are needed. We investigated dynamic tissue perfusion measurement (DTPM) with the PixelFlux-software to measure microvascular changes in the renal cortex in 35 children with VUR and 28 healthy children. DTPM of defined horizontal slices of the renal cortex was carried out. A kidney was assigned to the “low grade reflux”-group if the reflux grade of the voiding cystourethrogram was 1 to 3 and to the “high grade reflux”-group if the reflux grade was 4 to 5. Kidneys with VUR showed a significantly reduced cortical perfusion. Compared to healthy kidneys, this decline reached in low and high grade refluxes within the proximal 50% of the cortex: 3% and 12 %, in the distal 50% of the cortex: 21% and 44 % and in the most distal 20 % of the cortex 41% and 44%. DTPM reveals a perfusion loss in kidneys depending on the degree of VUR, which is most pronounced in the peripheral cortex. Thus, DTPM offers the tool to evaluate microvascular perfusion, to help planning treatment decisions in children with VUR.

Vascularity of the urethra in continent women using colour doppler high-frequency endovaginal ultrasonography

Objectives

To assess the urethral vascularity in continent women using colour doppler high frequency endovaginal ultrasonography (EVUS).

Methods

We recruited 61 continent women attending gynaecology clinics between July and October 2009. Exclusion criteria included symptoms of urinary incontinence, voiding dysfunction, pelvic organ prolapse or urinary tract infection. The participants underwent EVUS using high frequency (9-12 MHz) biplane transducer (type 8848 BK Medical), according to a standardised protocol. Colour Doppler US was performed in sagittal plane and in transverse plane at the level of the mid-urethra. Ten seconds video files were recorded and following vascular parameters: flow velocity (V_mix), area of the vessels (A_mix), intensity of vascularity (I_mix), pulsatility index (PI_mix) and resistance index (RI_mix) was evaluated.

Results

There were 30 nulliparous (49.2%) women and 31 multiparous women (50.8%) with a mean (±SD) age of 32 (±4) and 46 (±6) years respectively. Significant impairment of vascularity was observed in multiparous patients as compared to nulliparous and was reflected by increased values of RI_mix (p < 0.001) and PI_mix (p < 0.001), and decreased values of V_mix (p < 0.001), A_mix (p < 0.001), I_mix (p < 0.001) in axial and midsagittal sections of the midurethra. A significant decrease of mean value ± SD of I_mix- from 0.02 ± 0.02 in nulliparous to 0.005 ± 0.01 in multiparous was observed.

Cronbach alpha, used to assess vascular correlations and parity demonstrated a reduction when expressed only for vascular parameters, indicating that number of deliveries is an important factor while assessing urethral vascularity.

Conclusions

Compared to continent nulliparous women, continent multiparous women demonstrated a significant reduction in the vascularity parameters in all measured variables when parity was accounted for.

Advances in knowledge

This study provides the basis for further research in assessing urethral vascularity in women.

Renal transplantation parenchymal complications: what Doppler ultrasound can and cannot do

Kidney transplantation is the treatment of choice in end-stage renal disease, given the better quality of life of transplanted patients when compared with patients on maintenance dialysis. In spite of surgical improvements and new immunosuppressive regimens, parts of transplanted grafts still develop chronic dysfunction. Ultrasonography, both in B-mode and with Doppler ultrasound, is an important diagnostic tool in case of clinical conditions which might impair kidney function. Even though ultrasonography is considered fundamental in the diagnosis of vascular and surgical complications of the transplanted kidney, its role is not fully understood in case of parenchymal complications of the graft. The specificity of Doppler is low both in case of acute complications, such as acute tubular necrosis, drugs toxicity and acute rejection, and in case of chronic conditions, such as chronic allograft nephropathy. Single determinations of resistance indices present low diagnostic accuracy, which is higher in case of successive measurements performed during the follow-up of the graft. Modern techniques such as tissue pulsatility index, maximal fractional area and contrast-enhanced ultrasound increase ultrasonography diagnostic power in case of parenchymal complications of the transplanted kidney.

Correlation of histopathologic and dynamic tissue perfusion measurement findings in transplanted kidneys

Background

Cortical perfusion of the renal transplant can be non-invasively assessed by color Doppler ultrasonography. We performed the Dynamic Tissue Perfusion Measurement (DTPM) of the transplant’s renal cortex using color Doppler ultrasonography (PixelFlux technique), and compared the results with the histopathological findings of transplant biopsies.

Methods

Ninety-six DTPM studies of the renal transplant’s cortex followed by transplant biopsies were performed in 78 patients. The cortical perfusion data were compared with the parameter of peritubular inflammatory cell accumulation (PTC 0 to 3) based on Banff-classification system.

Results

A significant decrease of cortical perfusion could be demonstrated as the inflammatory cells accumulation in peritubular capillaries increased. Increasing peritubulitis caused a perfusion loss from central to distal layers of 79% in PTC 0, of 85% in PTC 1, of 94% in PTC 2, and of 94% in PTC 3. Furthermore, the perfusion loss due to peritubular inflammation was more prominent in the distal cortical layer. The extent of perfusion decline with increasing peritubulitis (from PTC 0 to PTC 3) was 64% in proximal 20% cortical layer (p20), 63% in proximal 50% cortical layer (p50), increased to 76% in distal 50% cortical layer (d50), and peaked at 90% in the distal 20% cortical layer (d20). For those without peritubulitis (PTC 0), the increase in the the Interstitial Fibrosis/Tubular Atrophy (IF/TA) score was accompanied by a significantly increased cortical perfusion. A Polyomavirus infection was associated with an increased cortical perfusion.

Conclusions

Our study demonstrated that the perfusion of the renal transplant is associated with certain pathological changes within the graft. DTPM showed a significant reduction of cortical perfusion in the transplant renal cortex related to peritubular capillary inflammation.

Neonatal hypoxic-ischemic injury: sonography and dynamic color Doppler sonography perfusion of the brain and abdomen with pathologic correlation

OBJECTIVE

The purpose of this article is to describe the role of cerebral and abdominal sonography with color Doppler sonography, including assessment of multiorgan tissue perfusion, in neonates with hypoxic-ischemic injury.

CONCLUSION

Bedside sonography and color Doppler sonography of the brain and abdominal organs can provide reliable and comprehensive information in asphyxiated neonates with hypoxic-ischemic injury. This article, which includes pathologic correlation, illustrates the major sonographic findings in this critical population.

Non-invasive assessment of renal allograft fibrosis by dynamic sonographic tissue perfusion measurement

BACKGROUND

Chronic allograft nephropathy (CAN) characterized by interstitial fibrosis and tubular atrophy is a major cause of renal transplant failure. The diagnosis can currently only be verified by a graft biopsy.

PURPOSE

To evaluate whether non-invasive dynamic color Doppler sonographic parenchymal perfusion measurements are different in grafts with various degrees of biopsy proven renal transplant fibrosis.

MATERIAL AND METHODS

Forty-nine adult patients were prospectively included. Four patients were excluded. Color Doppler videos from the renal cortex were recorded. Perfusion in the renal cortex was evaluated using a software package which calculates color pixel area and flow velocity, encoded by each pixel inside a region of interest of a video sequence. The software calculates parameters that describe tissue perfusion numerically. Two of these, the perfusion intensity and tissue pulsatility index, were compared to grade of interstitial fibrosis (0-3) in biopsies. Observer agreement was evaluated in a subset of 12 patients.

RESULTS

Of the 45 patients analyzed, 18 patients had grade 0, 18 had grade 1, seven had grade 2 and two had grade 3 fibrosis. The mean perfusion intensity of grade 0 was significantly higher than that of grade 2 and 3 fibrosis in the proximal cortical layer (1.65 m/s vs. 0.84 m/s, P = 0.008). No significant difference was found between grade 0 and grade 1 fibrosis. Perfusion intensity was correlated to estimated glomerular filtration rate (Pearson r 0.51, P = 0.001, R(2) = 0.26 and 0.46, P = 0.001, R(2) = 0.22 in the distal and proximal cortex, respectively). Inter-observer agreement of the perfusion intensity, expressed as intraclass correlation coefficient was 0.69 in the proximal part of the cortex. Intra-observer agreement was 0.85 for observer 1 and 0.82 for observer 2.

CONCLUSION

Perfusion intensity assessed by dynamic color Doppler measurements is significantly reduced in allografts with grade 2 and 3 fibrosis compared to allografts without fibrosis. Further studies involving longitudinal assessment of allografts undergoing protocol biopsies would be of interest.

Quantitative assessment of urethral vascularity in nulliparous females using high-frequency endovaginal ultrasonography

PURPOSE

To assess the vascular parameters in the urethra of nulliparous females and to compare the vascularity among various parts of the urethra, using high-frequency endovaginal ultrasonography (EVUS).

METHODS

Twenty-two nulliparous women, mean age 27 years, underwent EVUS using a biplane transducer at 12 MHz frequency. Color Doppler examinations of the urethra were recorded and further evaluated off-line using special software (Pixel Flux) for quantitative assessment of the vascularity. The urethra was divided into four regions of interest (ROIs) in the midsagittal plane and three ROIs in the axial plane. The following parameters were measured: velocity (V), perfused area (A), perfusion intensity (I), pulsatility index (PI), and resistance index (RI). Interobserver and intraobserver reproducibility analysis was also performed.

RESULTS

In midsagittal plane, the midurethra presented the highest value of V and lowest value of A. The intramural part showed the lowest value of I and the highest values of RI and PI. In the distal urethra, the highest value of I and the lowest value of RI was seen. In the axial plane, the values of V, A, and I were statistically significantly higher in the external part of the midurethra compared with the internal part. Excellent interobserver and intraobserver reproducibility was shown in the majority of parameters for the entire urethra.

CONCLUSIONS

Vascularity differs in different parts of the urethra. Pixel Flux is a valuable tool for providing reproducible quantitative analysis of vascular parameters for the entire urethra.

Pulsatile perfusion of kidney allografts

PURPOSE OF REVIEW

The purpose of this article is to describe the current use of pulsatile kidney perfusion during organ preservation and the effects on kidney allograft outcomes and utilization.

RECENT FINDINGS

As of spring 2008, there were 75 629 candidates on the kidney waiting list in the USA according to United Network for Organ Sharing data. In 2006, a total of 1815 deceased donor expanded criteria donors kidneys were transplanted, and approximately 80% of those kidneys had cold ischemic time of over 12 h. The utilization of kidney pulsatile perfusion varies extensively throughout the USA with rates of 7-12% in our institution.

SUMMARY

Data on the use of pulsatile hypothermic perfusion for kidneys during organ preservation are limited and mostly retrospective. Most authors agree that pulsatile perfusion is safe and leads to a decrease in delayed graft function, especially for marginal kidneys from extended criteria or deceased donors. The long-term effects of delayed graft function on graft survival remain to be seen. With the recent large-sampled international prospective randomized trial recently completed, we may see more kidneys pulsatile perfused. This may lead to an increase in the utilization of otherwise discarded kidneys, though these data are difficult to extrapolate.

Nanorod-based flow estimation using a high-frame-rate photoacoustic imaging system

A quantitative flow measurement method that utilizes a sequence of photoacoustic images is described. The method is based on the use of gold nanorods as a contrast agent for photoacoustic imaging. The peak optical absorption wavelength of a gold nanorod depends on its aspect ratio, which can be altered by laser irradiation (we establish a wash-in flow estimation method of this process). The concentration of nanorods with a particular aspect ratio inside a region of interest is affected by both laser-induced shape changes and replenishment of nanorods at a rate determined by the flow velocity. In this study, the concentration is monitored using a custom-designed, high-frame-rate photoacoustic imaging system. This imaging system consists of fiber bundles for wide area laser irradiation, a laser ultrasonic transducer array, and an ultrasound front-end subsystem that allows acoustic data to be acquired simultaneously from 64 transducer elements. Currently, the frame rate of this system is limited by the pulse-repetition frequency of the laser (i.e., 15 Hz). With this system, experimental results from a chicken breast tissue show that flow velocities from 0.125 to 2 mms can be measured with an average error of 31.3%.