Yong-Lan He1, Philipp Riffel2, Daniel Hausmann2, Stefan Schönberg2, and Ulrike Attenberger2
1Radiology, Peking Union Medical College Hospital, Beijing, China, People's Republic of, 2Department of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany
Synopsis
This is the first MR study to evaluate the use of
zoomed EPI technology for diffusion-weighted imaging in the kidney. Zoomed diffusion-weighted EPI leads to substantial
image quality improvements with reduction of susceptibility artifacts in renal
DWI.
The combination of the two sequences for renal imaging
might be recommended: a c-EPI scan to cover and screen the whole upper abdomen
and a z-EPI scan focused on the targeted anatomical structure and suspected
lesions. TARGET
AUDIENCE
Radiologists engaged in genitourinary imaging.
PURPOSE
To assess the feasibility and clinical robustness of a
zoomed diffusion-weighted EPI (z-EPI) sequence in MR imaging of the kidney
compared to conventional single-shot EPI (c-EPI).
METHODS
This retrospective study was approved by institutional
research ethics board. From 11/2012 to 9/2015, 75 patients (median age 58.2
years±13.5, range 23-83 years, 52 men, 23 women) who underwent renal MR
examination at our institution were enrolled in this study. Examinations were
performed on a 3T whole-body MR system (Magnetom Skyra, Siemens) equipped with
a two-channel fully dynamic parallel transmit array (TimTX TrueShape, Siemens).
The acquired sequences consisted of a conventional EPI DWI and a zoomed EPI DWI
of the kidney. For z-EPI, the standard sinc excitation was replaced with a
two-dimensional spatially-selective RF pulse using an echo-planar transmit
trajectory. Images were blinded evaluated by two radiologists with regard to
image blur, delineation of the kidney, distortion artifacts, overall image
quality, diagnostic confidence and overall scan preference. Sequences were
compared using paired Wilcoxon tests. ADC values of the upper pole, mid-zone,
lower pole of the bilateral kidneys as well as renal lesions were calculated
and compared between sequences using paired t test.
RESULTS
Readers preferred z-EPI overall to c-EPI in 94.7% cases
(71/75). The median image quality scores of z-EPI were significant higher than
that of c-EPI (p<0.05). Diagnostic confidence was statistically
significantly better with z-EPI (p=0.046). No statistically significant
differences in calculated ADC values were observed between the two sequences.
DISCUSSION
New developments in technology such as dual-source
transmit array functionality for B1 shimming, has reduced the degree of
artifact related to B1 inhomogeneity, thus improving image quality and
reproducibility of DWI.1,2 The combination of 2-dimensional spatially selective
radiofrequency (RF) excitation pulses and reduced field of view (FOV) imaging
(ie, zoomed) leads to a further reduction of susceptibility and distortion
artifacts by shortening the length of the echo planar imaging (EPI) echo train.3,4
To our knowledge, this is the first MR study to evaluate the use of zoomed EPI
technology for diffusion-weighted imaging in the kidney. The superior imaging
quality of zoomed EPI could potentially help the differential diagnosis for renal
lesions, especially the tiny tumors.
CONCLUSION
Zoomed diffusion-weighted EPI leads to substantial
image quality improvements with reduction of susceptibility artifacts in renal
DWI. The combination of
the two sequences for renal imaging might be recommended: a c-EPI scan to cover
and screen the whole upper abdomen and a z-EPI scan focused on the targeted
anatomical structure and suspected lesions.
Acknowledgements
noneReferences
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