Measurement of glomerular filtration rate by dynamic contrast-enhanced magnetic resonance imaging using a subject-specific two-compartment model

Clinical Comparison of the Glomerular Filtration Rate Calculated from Different Renal Depths and Formulae

A camera-based method using Technetium-99m diethylenetriaminepentaacetic acid (Tc-99m DTPA) is commonly used to calculate glomerular filtration rate (GFR), especially, as it can easily calculate split renal function. Renal depth is the main factor affecting the measurement of GFR accuracy. This study aimed to compare the difference of renal depths between three formulae and a CT scan, and, additionally, to calculate the GFRs by four methods. We retrospectively reviewed the medical records of patients receiving a renal dynamic scan. All patients underwent a laboratory test within one month, and a computed tomography (CT) scan within two months, before or after the renal dynamic scan. The GFRs were calculated by employing a renal dynamic scan using renal depth measured in three formulae (Tonnesen’s, Itoh K’s, and Taylor’s), and a CT scan. The renal depths measured by the above four methods were compared, and the GFRs were compared to the modified estimated GFR (eGFR). Fifty-one patients were enrolled in the study. The mean modified eGFR was 60.5 ± 42.7 mL/min. The mean GFRs calculated by three formulae and CT were 45.3 ± 23.3, 54.7 ± 27.5, 56.5 ± 26.3, and 63.7 ± 30.0, respectively. All of them correlated well with the modified eGFR (r = 0.87, 0.87, 0.87, and 0.84, respectively). The Bland–Altman plot revealed good consistency between the calculated GFR by Tonnesen’s and the modified eGFR. The renal depths measured using the three formulae were smaller than those measured using the CT scan, and the right renal depth was always larger than the left. In patients with modified eGFR > 60 mL/min, the GFR calculated by CT was the closest to the modified eGFR. The Renal depth measured by CT scan is deeper than that using formula, and it influences the GFR calculated by Gate’s method. The GFR calculated by CT is more closely related to modified eGFR when modified eGFR > 60 mL/min.

A Multi-Layer Perceptron Network for Perfusion Parameter Estimation in DCE-MRI Studies of the Healthy Kidney

Background: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is an imaging technique which helps in visualizing and quantifying perfusion—one of the most important indicators of an organ’s state. This paper focuses on perfusion and filtration in the kidney, whose performance directly influences versatile functions of the body. In clinical practice, kidney function is assessed by measuring glomerular filtration rate (GFR). Estimating GFR based on DCE-MRI data requires the application of an organ-specific pharmacokinetic (PK) model. However, determination of the model parameters, and thus the characterization of GFR, is sensitive to determination of the arterial input function (AIF) and the initial choice of parameter values. Methods: This paper proposes a multi-layer perceptron network for PK model parameter determination, in order to overcome the limitations of the traditional model’s optimization techniques based on non-linear least-squares curve-fitting. As a reference method, we applied the trust-region reflective algorithm to numerically optimize the model. The effectiveness of the proposed approach was tested for 20 data sets, collected for 10 healthy volunteers whose image-derived GFR scores were compared with ground-truth blood test values. Results: The achieved mean difference between the image-derived and ground-truth GFR values was 2.35 mL/min/1.73 m2, which is comparable to the result obtained for the reference estimation method (−5.80 mL/min/1.73 m2). Conclusions: Neural networks are a feasible alternative to the least-squares curve-fitting algorithm, ensuring agreement with ground-truth measurements at a comparable level. The advantages of using a neural network are twofold. Firstly, it can estimate a GFR value without the need to determine the AIF for each individual patient. Secondly, a reliable estimate can be obtained, without the need to manually set up either the initial parameter values or the constraints thereof.

Prospective pediatric study comparing glomerular filtration rate estimates based on motion-robust dynamic contrast-enhanced magnetic resonance imaging and serum creatinine (eGFR) to 99mTc DTPA

BACKGROUND

Current methods to estimate glomerular filtration rate (GFR) have shortcomings. Estimates based on serum creatinine are known to be inaccurate in the chronically ill and during acute changes in renal function. Gold standard methods such as inulin and ^99mTc diethylenetriamine pentaacetic acid (DTPA) require blood or urine sampling and thus can be difficult to perform in children. Motion-robust radial volumetric interpolated breath-hold examination (VIBE) dynamic contrast-enhanced MRI represents a novel tool for estimating GFR that has not been validated in children.

OBJECTIVE

The purpose of our study was to determine the feasibility and accuracy of GFR measured by motion-robust radial VIBE dynamic contrast-enhanced MRI compared to estimates by serum creatinine (eGFR) and ^99mTc DTPA in children.

MATERIALS AND METHODS

We enrolled children, 0-18 years of age, who were undergoing both a contrast-enhanced MRI and nuclear medicine ^99mTc DTPA glomerular filtration rate (NM-GFR) within 2 weeks of each other. Enrolled children consented to an additional 6-min dynamic contrast-enhanced MRI scan using the motion-robust high spatiotemporal resolution prototype dynamic radial VIBE sequence (Siemens, Erlangen, Germany) at 3 tesla (T). The images were reconstructed offline with high temporal resolution (~3 s/volume) using compressed sensing image reconstruction including regularization in temporal dimension to improve image quality and reduce streaking artifacts. Images were then automatically post-processed using in-house-developed software. Post-processing steps included automatic segmentation of kidney parenchyma and aorta using convolutional neural network techniques and tracer kinetic model fitting using the Sourbron two-compartment model to calculate the MR-based GFR (MR-GFR). The NM-GFR was compared to MR-GFR and estimated GFR based on serum creatinine (eGFR) using Pearson correlation coefficient and Bland-Altman analysis.

RESULTS

Twenty-one children (7 female, 14 male) were enrolled between February 2017 and May 2018. Data from six of these children were not further analyzed because of deviations from the MRI protocol. Fifteen patients were analyzed (5 female, 10 male; average age 5.9 years); the method was technically feasible in all children. The results showed that the MR-GFR correlated with NM-GFR with a Pearson correlation coefficient (r-value) of 0.98. Bland-Altman analysis (i.e. difference of MR-GFR and NM-GFR versus mean of NM-GFR and MR-GFR) showed a mean difference of -0.32 and reproducibility coefficient of 18 with 95% confidence interval, and the coefficient of variation of 6.7% with values between -19 (-1.96 standard deviation) and 18 (+1.96 standard deviation). In contrast, serum creatinine compared with NM-GFR yielded an r-value of 0.73. Bland-Altman analysis (i.e. difference of eGFR and NM-GFR versus mean of NM-GFR and eGFR) showed a mean difference of 2.9 and reproducibility coefficient of 70 with 95% confidence interval, and the coefficient of variation of 25% with values between -67 (-1.96 standard deviation) and 73 (+1.96 standard deviation).

CONCLUSION

MR-GFR is a technically feasible and reliable method of measuring GFR when compared to the reference standard, NM-GFR by serum ^99mTc DTPA, and MR-GFR is more reliable than estimates based on serum creatinine.

Feasibility of gamma camera-based GFR measurement using renal depth evaluated by lateral scan of 99mTc-DTPA renography

OBJECTIVE

Gamma camera-based measurement of glomerular filtration rate (GFR) with ^99mTc-diethylenetriaminepentaacetic acid (DTPA) is an established non-invasive measurement of split renal function; however, it is not as accurate as the plasma sample method. Therefore, study into improving the accuracy of such method is clinically relevant. The aim of this study was to elucidate the feasibility of gamma camera-based GFR measurement using renal depth evaluated by lateral scan of ^99mTc-DTPA renography and comparing the results with those of GFR using renal depth measured by CT, and three representative formulas.

METHODS

The study population comprised 38 patients (median, 69 years; male 28, female 10; median estimated GFR, 67.4 ml/min) with renourinary disorders. Scintigraphy was performed after intravenous injection of 370 MBq ^99mTc-DTPA by dynamic data acquisition for 20 min, followed by a bilateral static scan of the abdomen for 3 min. All patients underwent computed tomography (CT) within 2 months from renography. GFR was calculated by renography using renal depth determined in five ways; lateral scan of ^99mTc-DTPA, CT, and three formulas previously created with using weight, height and age. GFRs were compared with estimated GFR (eGFR). The depth of both kidneys measured as described above was compared and evaluated the laterality of the renal depth.

RESULTS

The median values of GFR calculated with renal depth determined by ^99mTc-DTPA renography, CT, and the three formulas were 87.3, 83.9, 67.8, 68.3, and 71.5 ml/min, respectively. All of them correlated significantly with eGFR (r = 0.734, r = 0.687, r = 0.728, r = 0.726, and r = 0.686, respectively), however, no significant difference was observed among five correlation coefficients. Bland-Altman plot revealed that eGFR had error and fixed bias when compared with GFRs calculated using renal depth determined by renography, CT, and Taylor's formula. The depth of both kidneys measured by ^99mTc-DTPA renography was equivalent to that measured by CT, however, those measured by the three formulas were significantly smaller than that measured by ^99mTc-DTPA renography. The depth of the right kidney was larger than that of the left kidney using all three formulas in all patients. However, CT detected only 66% of patients to have a deeper right kidney than left kidney.

CONCLUSION

Lateral scanning is a feasible procedure to measure renal depth for accurate and reasonable split GFR measurements using ^99mTc-DTPA renography.

Accumulation and toxicity of thiamethoxam and its metabolite clothianidin to the gonads of Eremias argus

The endocrine disrupting effect of pesticides is considered to be an important factor in the decline of reptile populations. The large-scale application of neonicotinoids in the environment poses a potential threat to small farmland lizards Eremias argus. In this study, we evaluated the disruption effects of thiamethoxam and its metabolite clothianidin on the endocrine disruption of Eremias argus during 28 d exposure. Thiamethoxam and clothianidin could accumulate in the testis and ovary. Adequate blood exchange was the main cause of thiamethoxam and clothianidin accumulation in the gonads. The production of clothianidin aggravated the effect of endocrine disruption to lizards. Thiamethoxam/clothianidin exhibited two distinct ways of interfering with the endocrine disruption of the male and female lizards. Thiamethoxam/clothianidin significantly up-regulated the expression of cyp17 and cyp19 genes in the testis, which ultimately led to a significant decrease in testosterone levels and a significant increase in the 17-estradiol concentrations in plasma. The expression of the estrogen receptor gene in the liver was also significantly increased in male lizards. The significant declines in testosterone and prostaglandin D2 levels in the plasma indicated that thiamethoxam and clothianidin could cause androgen deficiency in male lizards. Meanwhile, in female lizards, thiamethoxam/clothianidin increased the expression of hsd17β gene in the ovary, causing an increase in testosterone levels in the plasma and an up-regulation of androgen receptor expression in the liver. The effects of thiamethoxam and clothianidin on male lizards were more pronounced. This study verified the possible endocrine disrupting effects of neonicotinoids and provided a new perspective for the study of global recession of reptiles.

Prospective comparison between DCE-MRR and 99m Tc-DTPA-based SPECT for determination of allograft renal function

BACKGROUND

Glomerular filtration rate (GFR) is a preferred indicator of allograft renal function, but direct measurement of GFR remains complicated.

PURPOSE

To prospectively compare dynamic contrast-enhanced MR renography (DCE-MRR) with ^99m Tc-DTPA-based single-photon emission computed tomography (SPECT) for determination of allograft renal function.

STUDY TYPE

Prospective.

POPULATION

Seventy kidney-transplant recipients FIELD STRENGTH: A low-dose DCE-MRR with a 3.0T scanner and a ^99m Tc-DTPA-based SPECT after renal transplantation were performed.

ASSESSMENT

A Baumann-Rudin (BR) and a modified two-compartment model (JZ2C) were used for DCE-MRR analysis. Standard Gate's method was used for SPECT analysis. An endogenous creatinine clearance rate (CCr) constituted the reference standard.

STATISTICAL TESTS

Pearson correlation test and Bland-Altman agreement analysis.

RESULTS

The reference CCr-GFR was 59.58 ± 23.72 mL/min/1.73 m² . GFR determined by eGFR, BR, JZ2C, and SPECT was 90.22 ± 34.38, 36.78 ± 14.46, 48.99 ± 23.88, and 67.32 ± 18.44 mL/min/1.73 m² , respectively. DCE-MRR using JZ2C had the best overall performance, with a Pearson correlation coefficient of 0.81, a bias of -10.58 mL/min/1.73 m² , and a precision of 14.61 mL/min/1.73 m² , as well as high accuracy (30-50% intervals: 74.3-90.0%). Although SPECT had a small bias (7.74 mL/min/1.73 m² ), it had a poor correlation coefficient (0.38), poor precision (23.93 mL/min/1.73 m² ), and low accuracy (64.3-72.3%) as compared with DCE-MRR using JZ2C.

DATA CONCLUSION

DCE-MRR using JZ2C is superior to ^99m Tc-DTPA-based SPECT to determine allograft renal function.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:262-269.

Modified dixon-based renal dynamic contrast-enhanced MRI facilitates automated registration and perfusion analysis

Purpose

Renal dynamic contrast‐enhanced (DCE) MRI provides information on renal perfusion and filtration. However, clinical implementation is hampered by challenges in postprocessing as a result of misalignment of the kidneys due to respiration. We propose to perform automated image registration using the fat‐only images derived from a modified Dixon reconstruction of a dual‐echo acquisition because these provide consistent contrast over the dynamic series.

Methods

DCE data of 10 hypertensive patients was used. Dual‐echo images were acquired at 1.5 T with temporal resolution of 3.9 s during contrast agent injection. Dixon fat, water, and in‐phase and opposed‐phase (OP) images were reconstructed. Postprocessing was automated. Registration was performed both to fat images and OP images for comparison. Perfusion and filtration values were extracted from a two‐compartment model fit.

Results

Automatic registration to fat images performed better than automatic registration to OP images with visible contrast enhancement. Median vertical misalignment of the kidneys was 14 mm prior to registration, compared to 3 mm and 5 mm with registration to fat images and OP images, respectively (P = 0.03). Mean perfusion values and MR‐based glomerular filtration rates (GFR) were 233 ± 64 mL/100 mL/min and 60 ± 36 mL/minute, respectively, based on fat‐registered images. MR‐based GFR correlated with creatinine‐based GFR (P = 0.04) for fat‐registered images. For unregistered and OP‐registered images, this correlation was not significant.

Conclusion

Absence of contrast changes on Dixon fat images improves registration in renal DCE MRI and enables automated postprocessing, resulting in a more accurate estimation of GFR. Magn Reson Med 80:66–76, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Measurement of glomerular filtration rate by dynamic contrast-enhanced magnetic resonance imaging using a subject-specific two-compartment model

Measuring glomerular filtration rate (GFR) by dynamic contrast‐enhanced (DCE) magnetic resonance imaging (MRI) as part of standard of care clinical MRI exams (e.g., in pediatric solid tumor patients) has the potential to reduce diagnostic burden. However, enthusiasm for this relatively new GFR test may be curbed by the limited amount of cross‐calibration studies with reference GFR techniques and the vast variety of MR tracer model algorithms causing confusion on the choice of model. To advance MRI‐based GFR quantification via improved GFR modeling and comparison with associated ^99mTc‐DTPA‐GFR, 29 long‐term Wilms' tumor survivors (19.0–43.3 years, [median 32.0 ± 6.0 years]) treated with nephrectomy, nonnephrotoxic chemotherapy ± radiotherapy underwent MRI with Gd‐DTPA administration and a ^99mTc‐DTPA GFR test. For DCE‐MRI‐based GFR estimation, a subject‐specific two‐compartment (SS‐2C) model was developed that uses individual hematocrit values, automatically defines subject‐specific uptake intervals, and fits tracer‐uptake curves by incorporating these measures. The association between reference ^99mTc‐DTPA GFR and MR‐GFRs obtained by SS‐2C, three published 2C uptake, and inflow–outflow models was investigated via linear regression analysis. Uptake intervals varied from 64 sec to 141 sec [96 sec ± 21 sec] and hematocrit values ranged from 30% to 49% [41% ± 4%]; these parameters can therefore not be assumed as constants in 2C modeling. Our MR‐GFR estimates using the SS‐2C model showed accordingly the highest correlation with ^99mTc‐DTPA‐GFRs (R² = 0.76, P < 0.001) compared with other models (R²‐range: 0.36–0.66). In conclusion, SS‐2C modeling of DCE‐MRI data improved the association between GFR obtained by ^99mTc‐DTPA and Gd‐DTPA DCE‐MRI to such a degree that this approach could turn into a viable, diagnostic GFR assay without radiation exposure to the patient.