Renal Adiposity Confounds Quantitative Assessment of Markers of Renal Diffusion With MRI: A Proposed Correction Method

Behzad Ebrahimi, Ahmed Saad, Kai Jiang, Christopher M. Ferguson, Hui Tang, John R. Woollard, James Glockner, Stephen C Textor, Lilach O Lerman

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

OBJECTIVES: Recent studies have indicated that excessive fat may confound assessment of diffusion in organs with high fat content, such as the liver and breast. However, the extent of this effect in the kidney, which is not considered a major fat deposition site, remains unclear. This study tested the hypothesis that renal fat may impact diffusion-weighted imaging (DWI) parameters, and proposes a 3-compartment model (TCM) to circumvent this effect. METHODS: Using computer simulations, we investigated the effect of fat on assessment of apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM), and TCM-derived pure-diffusivity. We also investigated the influence of magnetic resonance repetition (TR) and echo time (TE) on DWI parameters as a result of variation in the relative contribution of the fat signal. Apparent diffusion coefficient, IVIM and TCM DWI parameters were calculated in domestic pigs fed a high-cholesterol (obese group) or normal diet (lean group), and correlated to renal histology. Intravoxel incoherent motion–derived pure-diffusivity was also compared among 15 essential hypertension patients classified by body mass index (BMI) (high vs normal). Finally, pure-diffusivity was calculated and compared in 8 patients with atherosclerotic renal artery stenosis (ARAS) and 5 healthy subjects using IVIM and TCM. RESULTS: Simulations showed that unaccounted fat results in the underestimation of IVIM-derived pure diffusivity. The underestimation increases as the fat fraction increases, with higher pace at lower fat contents. The underestimation was larger for shorter TR and longer TE values due to the enhancement of the relative contribution of the fat signal. Moreover, TCM, which incorporates highly diffusion-weighted images (b > 2500 s/mm), could correct for fat-dependent underestimation. Animal studies in the lean and obese groups confirmed lower ADC and IVIM pure-diffusivity in obese versus lean pigs with otherwise healthy kidneys, whereas pure-diffusivity calculated using TCM were not different between the 2 groups. Similarly, essential hypertension patients with high BMI had lower ADC (1.9 vs 2.1 × 10 mm/s) and pure-diffusivity (1.7 vs 1.9 × 10 mm/s) than those with normal BMI. Pure-diffusivity calculated using IVIM was not different between the ARAS and healthy subjects, but TCM revealed significantly lower diffusivity in ARAS. CONCLUSIONS: Excessive renal fat may cause underestimation of renal ADC and IVIM-derived pure-diffusivity, which may hinder detection of renal pathology. Models accounting for fat contribution may help reduce the variability of diffusivity calculated using DWI.

Original languageEnglish (US)
JournalInvestigative Radiology
DOIs
StateAccepted/In press - May 29 2017

Fingerprint

Diffusion Magnetic Resonance Imaging
Adiposity
Fats
Kidney
Renal Artery Obstruction
Body Mass Index
Healthy Volunteers
Sus scrofa
Computer Simulation
Histology
Breast
Magnetic Resonance Spectroscopy
Swine

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

Cite this

Renal Adiposity Confounds Quantitative Assessment of Markers of Renal Diffusion With MRI : A Proposed Correction Method. / Ebrahimi, Behzad; Saad, Ahmed; Jiang, Kai; Ferguson, Christopher M.; Tang, Hui; Woollard, John R.; Glockner, James; Textor, Stephen C; Lerman, Lilach O.

In: Investigative Radiology, 29.05.2017.

Research output: Contribution to journalArticle

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title = "Renal Adiposity Confounds Quantitative Assessment of Markers of Renal Diffusion With MRI: A Proposed Correction Method",
abstract = "OBJECTIVES: Recent studies have indicated that excessive fat may confound assessment of diffusion in organs with high fat content, such as the liver and breast. However, the extent of this effect in the kidney, which is not considered a major fat deposition site, remains unclear. This study tested the hypothesis that renal fat may impact diffusion-weighted imaging (DWI) parameters, and proposes a 3-compartment model (TCM) to circumvent this effect. METHODS: Using computer simulations, we investigated the effect of fat on assessment of apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM), and TCM-derived pure-diffusivity. We also investigated the influence of magnetic resonance repetition (TR) and echo time (TE) on DWI parameters as a result of variation in the relative contribution of the fat signal. Apparent diffusion coefficient, IVIM and TCM DWI parameters were calculated in domestic pigs fed a high-cholesterol (obese group) or normal diet (lean group), and correlated to renal histology. Intravoxel incoherent motion–derived pure-diffusivity was also compared among 15 essential hypertension patients classified by body mass index (BMI) (high vs normal). Finally, pure-diffusivity was calculated and compared in 8 patients with atherosclerotic renal artery stenosis (ARAS) and 5 healthy subjects using IVIM and TCM. RESULTS: Simulations showed that unaccounted fat results in the underestimation of IVIM-derived pure diffusivity. The underestimation increases as the fat fraction increases, with higher pace at lower fat contents. The underestimation was larger for shorter TR and longer TE values due to the enhancement of the relative contribution of the fat signal. Moreover, TCM, which incorporates highly diffusion-weighted images (b > 2500 s/mm), could correct for fat-dependent underestimation. Animal studies in the lean and obese groups confirmed lower ADC and IVIM pure-diffusivity in obese versus lean pigs with otherwise healthy kidneys, whereas pure-diffusivity calculated using TCM were not different between the 2 groups. Similarly, essential hypertension patients with high BMI had lower ADC (1.9 vs 2.1 × 10 mm/s) and pure-diffusivity (1.7 vs 1.9 × 10 mm/s) than those with normal BMI. Pure-diffusivity calculated using IVIM was not different between the ARAS and healthy subjects, but TCM revealed significantly lower diffusivity in ARAS. CONCLUSIONS: Excessive renal fat may cause underestimation of renal ADC and IVIM-derived pure-diffusivity, which may hinder detection of renal pathology. Models accounting for fat contribution may help reduce the variability of diffusivity calculated using DWI.",
author = "Behzad Ebrahimi and Ahmed Saad and Kai Jiang and Ferguson, {Christopher M.} and Hui Tang and Woollard, {John R.} and James Glockner and Textor, {Stephen C} and Lerman, {Lilach O}",
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T1 - Renal Adiposity Confounds Quantitative Assessment of Markers of Renal Diffusion With MRI

T2 - A Proposed Correction Method

AU - Ebrahimi, Behzad

AU - Saad, Ahmed

AU - Jiang, Kai

AU - Ferguson, Christopher M.

AU - Tang, Hui

AU - Woollard, John R.

AU - Glockner, James

AU - Textor, Stephen C

AU - Lerman, Lilach O

PY - 2017/5/29

Y1 - 2017/5/29

N2 - OBJECTIVES: Recent studies have indicated that excessive fat may confound assessment of diffusion in organs with high fat content, such as the liver and breast. However, the extent of this effect in the kidney, which is not considered a major fat deposition site, remains unclear. This study tested the hypothesis that renal fat may impact diffusion-weighted imaging (DWI) parameters, and proposes a 3-compartment model (TCM) to circumvent this effect. METHODS: Using computer simulations, we investigated the effect of fat on assessment of apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM), and TCM-derived pure-diffusivity. We also investigated the influence of magnetic resonance repetition (TR) and echo time (TE) on DWI parameters as a result of variation in the relative contribution of the fat signal. Apparent diffusion coefficient, IVIM and TCM DWI parameters were calculated in domestic pigs fed a high-cholesterol (obese group) or normal diet (lean group), and correlated to renal histology. Intravoxel incoherent motion–derived pure-diffusivity was also compared among 15 essential hypertension patients classified by body mass index (BMI) (high vs normal). Finally, pure-diffusivity was calculated and compared in 8 patients with atherosclerotic renal artery stenosis (ARAS) and 5 healthy subjects using IVIM and TCM. RESULTS: Simulations showed that unaccounted fat results in the underestimation of IVIM-derived pure diffusivity. The underestimation increases as the fat fraction increases, with higher pace at lower fat contents. The underestimation was larger for shorter TR and longer TE values due to the enhancement of the relative contribution of the fat signal. Moreover, TCM, which incorporates highly diffusion-weighted images (b > 2500 s/mm), could correct for fat-dependent underestimation. Animal studies in the lean and obese groups confirmed lower ADC and IVIM pure-diffusivity in obese versus lean pigs with otherwise healthy kidneys, whereas pure-diffusivity calculated using TCM were not different between the 2 groups. Similarly, essential hypertension patients with high BMI had lower ADC (1.9 vs 2.1 × 10 mm/s) and pure-diffusivity (1.7 vs 1.9 × 10 mm/s) than those with normal BMI. Pure-diffusivity calculated using IVIM was not different between the ARAS and healthy subjects, but TCM revealed significantly lower diffusivity in ARAS. CONCLUSIONS: Excessive renal fat may cause underestimation of renal ADC and IVIM-derived pure-diffusivity, which may hinder detection of renal pathology. Models accounting for fat contribution may help reduce the variability of diffusivity calculated using DWI.

AB - OBJECTIVES: Recent studies have indicated that excessive fat may confound assessment of diffusion in organs with high fat content, such as the liver and breast. However, the extent of this effect in the kidney, which is not considered a major fat deposition site, remains unclear. This study tested the hypothesis that renal fat may impact diffusion-weighted imaging (DWI) parameters, and proposes a 3-compartment model (TCM) to circumvent this effect. METHODS: Using computer simulations, we investigated the effect of fat on assessment of apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM), and TCM-derived pure-diffusivity. We also investigated the influence of magnetic resonance repetition (TR) and echo time (TE) on DWI parameters as a result of variation in the relative contribution of the fat signal. Apparent diffusion coefficient, IVIM and TCM DWI parameters were calculated in domestic pigs fed a high-cholesterol (obese group) or normal diet (lean group), and correlated to renal histology. Intravoxel incoherent motion–derived pure-diffusivity was also compared among 15 essential hypertension patients classified by body mass index (BMI) (high vs normal). Finally, pure-diffusivity was calculated and compared in 8 patients with atherosclerotic renal artery stenosis (ARAS) and 5 healthy subjects using IVIM and TCM. RESULTS: Simulations showed that unaccounted fat results in the underestimation of IVIM-derived pure diffusivity. The underestimation increases as the fat fraction increases, with higher pace at lower fat contents. The underestimation was larger for shorter TR and longer TE values due to the enhancement of the relative contribution of the fat signal. Moreover, TCM, which incorporates highly diffusion-weighted images (b > 2500 s/mm), could correct for fat-dependent underestimation. Animal studies in the lean and obese groups confirmed lower ADC and IVIM pure-diffusivity in obese versus lean pigs with otherwise healthy kidneys, whereas pure-diffusivity calculated using TCM were not different between the 2 groups. Similarly, essential hypertension patients with high BMI had lower ADC (1.9 vs 2.1 × 10 mm/s) and pure-diffusivity (1.7 vs 1.9 × 10 mm/s) than those with normal BMI. Pure-diffusivity calculated using IVIM was not different between the ARAS and healthy subjects, but TCM revealed significantly lower diffusivity in ARAS. CONCLUSIONS: Excessive renal fat may cause underestimation of renal ADC and IVIM-derived pure-diffusivity, which may hinder detection of renal pathology. Models accounting for fat contribution may help reduce the variability of diffusivity calculated using DWI.

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