First name
Steven
Last name
Warner

Title

A Dynamic Graph Cuts Method with Integrated Multiple Feature Maps for Segmenting Kidneys in 2D Ultrasound Images.

Year of Publication

2018

Date Published

2018 Feb 12

ISSN Number

1878-4046

Abstract

<p><strong>RATIONALE AND OBJECTIVES: </strong>Automatic segmentation of kidneys in ultrasound (US) images remains a challenging task because of high speckle noise, low contrast, and large appearance variations of kidneys in US images. Because texture features may improve the US image segmentation performance, we propose a novel graph cuts method to segment kidney in US images by integrating image intensity information and texture feature maps.</p>

<p><strong>MATERIALS AND METHODS: </strong>We develop a new graph cuts-based method to segment kidney US images by integrating original image intensity information and texture feature maps extracted using Gabor filters. To handle large appearance variation within kidney images and improve computational efficiency, we build a graph of image pixels close to kidney boundary instead of building a graph of the whole image. To make the kidney segmentation robust to weak boundaries, we adopt localized regional information to measure similarity between image pixels for computing edge weights to build the graph of image pixels. The localized graph is dynamically updated and the graph cuts-based segmentation iteratively progresses until convergence. Our method has been evaluated based on kidney US images of 85 subjects. The imaging data of 20 randomly selected subjects were used as training data to tune parameters of the image segmentation method, and the remaining data were used as testing data for validation.</p>

<p><strong>RESULTS: </strong>Experiment results demonstrated that the proposed method obtained promising segmentation results for bilateral kidneys (average Dice index = 0.9446, average mean distance = 2.2551, average specificity = 0.9971, average accuracy = 0.9919), better than other methods under comparison (P &lt; .05, paired Wilcoxon rank sum tests).</p>

<p><strong>CONCLUSIONS: </strong>The proposed method achieved promising performance for segmenting kidneys in two-dimensional US images, better than segmentation methods built on any single channel of image information. This method will facilitate extraction of kidney characteristics that may predict important clinical outcomes such as progression of chronic kidney disease.</p>

DOI

10.1016/j.acra.2018.01.004

Alternate Title

Acad Radiol

PMID

29449144

Title

Assessment of the combination of temperature and relative humidity on kidney stone presentations.

Year of Publication

2018

Number of Pages

97-105

Date Published

2018 Apr

ISSN Number

1096-0953

Abstract

<p>Temperature and relative humidity have opposing effects on evaporative water loss, the likely mediator of the temperature-dependence of nephrolithiasis. However, prior studies considered only dry-bulb temperatures when estimating the temperature-dependence of nephrolithiasis. We used distributed lag non-linear models and repeated 10-fold cross-validation to determine the daily temperature metric and corresponding adjustment for relative humidity that most accurately predicted kidney stone presentations during hot and cold periods in South Carolina from 1997 to 2015. We examined three metrics for wet-bulb temperatures and heat index, both of which measure the combination of temperature and humidity, and for dry-bulb temperatures: (1) daytime mean temperature; (2) 24-h mean temperature; and (3) most extreme 24-h temperature. For models using dry-bulb temperatures, we considered four treatments of relative humidity. Among 188,531 patients who presented with kidney stones, 24-h wet bulb temperature best predicted kidney stone presentation during summer. Mean cross-validated residuals were generally lower in summer for wet-bulb temperatures and heat index than the corresponding dry-bulb temperature metric, regardless of type of adjustment for relative humidity. Those dry-bulb models that additionally adjusted for relative humidity had higher mean residuals than other temperature metrics. The relative risk of kidney stone presentations at the 99th percentile of each temperature metric compared to the respective median temperature in summer months differed by temperature metric and relative humidity adjustment, and ranged from an excess risk of 8-14%. All metrics performed similarly in winter. The combination of temperature and relative humidity determine the risk of kidney stone presentations, particularly during periods of high heat and humidity. These results suggest that metrics that measure moist heat stress should be used to estimate the temperature-dependence of kidney stone presentations, but that the particular metric is relatively unimportant.</p>

DOI

10.1016/j.envres.2017.12.020

PMID

29289860

Title

Dietary Zinc and Incident Calcium Kidney Stones in Adolescence.

Year of Publication

2016

Date Published

2016 Nov 23

ISSN Number

1527-3792

Abstract

<p><strong>PURPOSE: </strong>To determine the association between dietary zinc intake and incident calcium kidney stones and examine the relationship between dietary zinc intake and urinary zinc excretion among adolescents.</p>

<p><strong>MATERIAL AND METHODS: </strong>This study was a nested case-control study conducted within a large pediatric healthcare system. Three 24-hour dietary recalls and spot urine chemistries were obtained for 30 participants aged 12-18 years with a first idiopathic calcium-based kidney stone and 30 healthy controls, matched on age, sex, race, and month of enrollment. Conditional logistic regression models were used to estimate the odds ratio (OR) between daily zinc intake and incident calcium kidney stones, adjusting for dietary phytate, protein, calcium, sodium, and oxalate. Multivariable linear regression was used to estimate the association between dietary and urine zinc, adjusting for urine creatinine and dietary phytate and calcium.</p>

<p><strong>RESULTS: </strong>Cases had lower daily zinc intake (8.1mg) than controls (10mg; p=0.029). Daily zinc intake of boys and girls with calcium stones was 2mg and 1.2mg lower, respectively, than the daily intake of zinc recommended by the Institute of Medicine. There was a 13% lower odds of incident stones for every 1mg higher daily zinc intake (OR, 0.87; 95% CI, 0.75-0.99). There was an estimated 4.5μg/dL increase in urine zinc per 1mg increase in dietary zinc (p=0.009), with weak evidence of a smaller increase in urine zinc in cases than in controls (interaction p=0.08).</p>

<p><strong>CONCLUSIONS: </strong>Lower dietary zinc intake was independently associated with incident calcium nephrolithiasis in this population of adolescents.</p>

DOI

10.1016/j.juro.2016.11.096

Alternate Title

J. Urol.

PMID

27889417

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