Boesch, Christoph Hans

Lu, Huanxiang

Reyes, Mauricio

Seif, Maryam

Vermathen, Peter

Bern Open Repository and Information System (BORIS)

    ADC [10-5mm2/sec] FP [%] FA     mean SD mean SD mean SD  medulla original 194 16 0.15 0.06 0.38 0.09 co-reg 198 12 0.13 0.05 0.35 0.07 p-value >0.1 <0.001 <0.001 <0.001 <0.001 <0.001  cortex original 203 12 0.17 0.05 0.23 0.06 co-reg 208 9 0.14 0.04 0.20 0.05 p-value <0.01 <0.001 <0.002 <0.002 <0.001 <0.001 Table 1: Comparison of ADC, FP and FA in kidneys derived from original and co-registered images (triggered scans). SD denotes the mean standard deviation of parameters in ROIs, not between subjects. 0.00.40.81.2RMSElow RMSEhigh RMSEtotmedulla origmedulla co-regcortex origcortex co-regFig. 2: Comparison of RMSEs in medulla and cortex between signals from original and co-registered images as a measure for signal variability (triggered scans)   Image co-registration for triggered and non-triggered DTI of the human kidney: Reduced variability of diffusion parameter estimation   Maryam Seif1, Huanxiang Lu2, Chris Boesch1, Mauricio Reyes2, Peter Vermathen1 1Depts Clinical Research and Radiology, University Bern, Bern, Switzerland  2Institute for Surgical Technology and Biomechanics, University Bern, Bern, Switzerland  Introduction: Generally abdominal DTI-scans are performed employing respiratory-triggering to reduce severe physiological motion artifacts caused by respiration. However, even in triggered scans residual motion remains, possibly increasing the variability of diffusion-parameters. This study aimed therefore at investigating the benefit of non-rigid image co-registration of individual echo planar (EP-) DTI-images of human kidneys in respiratory-triggered and also in non-triggered scans. Methods: Twenty healthy volunteers were examined on a 3T MR scanner (Siemens, Erlangen Germany). A DW single-shot-echo-planar imaging sequence was applied with ten different b-values (0-700s/mm2) in 6 non-collinear directions. The first group of 12 subjects was investigated employing respiratory-triggering only, in the second group of 8 subjects DTI was performed in addition without triggering. Co-registration of individual images was performed using an in-house developed multimodal non-rigid registration software, based on point-wise mutual information [1]. Further data processing included biexponential fitting, yielding ADC and the perfusion fraction FP (representing microcirculation contributions), and calculation of the fractional anisotropy (FA).  The co-registered and original images were compared in two ways: 1) For each analyzed ROI the standard deviation (SD) was calculated from all pixels within the ROIs; 2) The deviation from diffusion-model fitting was determined comparing the root mean squared error (RMSE). RMSE was determined for fitting the signal only for b-values b<100 sec/mm2 (RMSElow), for b-values b>100sec/mm2 (RMSEhigh), and for fitting all b-values (RMSEtot). Results: Visually the co-registered diffusion maps demonstrated less distortions (Fig. 1).  Quantitative analysis of the triggered scans demonstrated: 1) The SDs were significantly lower in co-registered images (Table 1). The mean values of FP, ADC and FA were also slightly but significantly different, possibly due to lower spurious inclusion of signals from other tissue; 2) All RMSEs were significantly lower in co-registered images (Fig.2).  Analysis of the non-triggered scans also demonstrated lower signal variations after co-registration compared to the original images. However the benefit was less pronounced and the variability compared to the triggered scans (with and without co-registration) was significantly higher. Discussion:  The results clearly demonstrate the benefit of co-registration of individual EP-images in renal DTI. Although currently the co-registration method does not allow for omitting the respiration-triggering in DTI scans of native kidneys, the lower variation also in non-triggered scans suggests that other organs or transplanted kidneys, where respiration motion is less severe, may be measured without triggering.  References:  1. Lu H, et al. Conf. Proc. IEEE Eng Med. Biol. Soc. 2010;2010:5951.   Acknowledgment: Supported by SNF-320030-138150   (b) ADC map of co-registration image (a) ADC map of original image (c) S0 map of original image (d) S0 map of co-registration imageFig. 1: Comparison of ADC and S0 maps from non-triggered DTI scans demonstrated less distortions in Co-registered images.source: http://boris.unibe.ch/61022/ | downloaded: 29.12.2014source: https://doi.org/10.7892/boris.11479 | downloaded: 8.5.2016

Image co-registration for triggered and non-triggered DTI of the human kidney: Reduced variability of diffusion parameter estimation

http://boris.unibe.ch/11479/1/SeifESMRMB2012.pdf

Image co-registration for triggered and non-triggered DTI of the human kidney: Reduced variability of diffusion parameter estimation

Abstract

Similar works

Full text

Available Versions

Bern Open Repository and Information System (BORIS)