| Purpose:To compare the breathhold, respiratory-triggered, and free-breathing techniques in diffusion-weighted magnetic resonance imaging (MRI) for the evaluation of focal liver lesions on a3.0T system.Materials and Methods:One hundred and fifty-two patients with focal liver lesions underwent routine MR and breathhold, respiratory-triggered, and free-breathing diffusion-weighted imaging (DWI) of the liver on a3.0Tesla (T) system,75of them were examined by the DWI scheme (1):All sequences were performed with b values of100and800s/mm2and identical parameters except for signal averages (two for respiratory-triggered, one for breathhold, and four for free-breathing), the slice number is24, including the whole liver. Each DWI’s scanning time is20s for breathhold,2min for respiratory-triggered, and1min for free-breathing. Another77patients were examined by the DWI scheme (2):The scanning parameters of the three techniques are consistent, excitation number are changed to2, scanning layer fixed to10, only the local lesion were examed. Overall scan time were controlled in20s for breathhold,25s for free breathing,1min for respiratory-triggered DWI. B value were still100and800s/mm2.2doctors assessed and measured the data respectively.Results:In the DWI scheme (1), the three kinds of DWI did not match the ADC values of normal liver parenchyma in b=800(P<0.0167), the consistency of performance is moderate (ICC=0.425), but the ADC values had no statistical difference when b=100(P>0.0167), and they showed a strong consistency (ICC=0.646), For all three types of breathing acquisitions, the focal liver lesions’ detection and accuracy rates have no statistical differences(P>0.05). The three groups focal lesions’ADC values showed high correlation (when b=800and100, the ICC were0.970and0.887, respectively), But the CNR, SNR of breathhold is lower than the respiratory-trigger and free-breathing DWI (P<0.0167). In the DWI scheme (2), the three breathing acquisitions’lesion detection (90.1～95.6%) and accuracy rate (85.4～89.7%) had no statistical difference (P>0.05), and the three groups normal liver’s (b=800and100, the ICC was0.701and0.701, respectively) and lesions’(b=800and100, the ICC was0.947and0.947, respectively) ADC values showed high correlation, but the free-breathing DWI’s CNR, SNR was significantly lower than the respiratory-triggered and breathhold DWI (P<0.0167).Conclusion:Respiratory-triggered DWI of the3T MRI system has the hig her SNR and contrast to noise ratio, and is the best DWI imaging acquisition technique. But for the patients with focal liver lesions who want to do the wh ole liver DWI scan, the free-breathing DWI is best, as it can achieve better i mage quality in a short time; for the patients who only need to do the local DWI scan to evaluate the lesion and the responds of drug treatment, the breat hhold DWI is optimal. Purpose: To compare and determine the reproducibility of apparent diffusion coefficient (ADC) measurements of the normal liver parenchyma in breathhold, respiratory triggered, and free-breathing diffusion-weighted magnetic resonance imaging (DWI).Materials and Methods:11volunteers did three and for a total of nine ti mes of breathhold (excitation number is1, at the end of the expiration, thickn ess/gapping=5/1mm), respiratory-triggered (excitation number is2, at the en d of the expiration, thickness/gapping=5/1mm), and the free-breathing (excit ation number is4, thickness/gapping=5/1mm) axial liver DWI, and then the y were all coronally reconstructed (thickness/gapping=8/1mm). Of them, the diffusion sensitivity value was800s/mm. Two high qualification doctor evalua ted the data, the ADC values were mainly measured on100×10mm2rectangula r area (ROI) of breathhold, respiratory-trigger and free-breathing DWI’s coronal ly reconstructed images. We used nonparametric test to compare axial and coro nally reconstructed images’ADC values of the liver parenchyma; and used Bla nd-Altman method to evaluate the ADC values’repeatability of coronally rec onstructed images.Results:The respiratory-triggered, breathhold, and free-breathing DWI’s coronally reconstructed liver parenchyma are isotropic, breathhold DWI’s mean ADC values was (1.09±0.07×10-3mm2/s) significantly lower than the respiratory-triggered DWI (1.16±0.09×10-3mm2/s) and the breathhold DWI (1.19±0.10×10-3mm2/s)(P<0.005), the axial measured results were similar. The result of comparing two of the three coronal ADC values’average difference and scope of consistency were (-0.09～-0.01±0.09～0.48) for breathhold DWI,(-0.04～0.01±0.11～0.17) for respiratory-triggered DWI,(-0.07～-0.02±0.11～0.18) for free-breathing DWI, respectively. Breathhold DWI’s mean absolute deviation and consistency limit range is maximum among the three techniques.Conclusion:The normal liver parenchyma’s ADC value of breathhold DW I is lower than the respiratory-triggered and free-breathing DWI, and it showed more poorer repeatability. It is suggested that the measurement of ADC value s of the liver parenchyma should be done within the respiratory-triggered or fr ee-breathing DWI. Purpose:This study aimed to perform comparisons between diffusion weighted imaging (DWI) sequences at3T with1.5T.Materials and Methods:21volunteers were examed in GE Signa HDx1.5T and3.0T MR with body surface and phased-array coil for regular MR and breathhold, respiratory-triggered and free-breathing DWI examinations. Each DWI sequence’s b values was100and800s/mm2, respectively. And the acceleration factor of parallel imaging technique (PI) was2.2high qualification image doctors recorded image artifacts, subjective image quality scores, signal-to-noise ratio, signal intensity and apparent diffusion coefficient (ADC) value on GE AW442Workstation. This study use SPSS17.0statistical software (LEAD Technologies, New York, NY) for the data analysis, P value less than0.05was considered statistically significant. If the three kinds of DWI require multiple comparison, on the basis of Bonferroni correction, P<0.05/3=0.0167was considered statistically significant.Results:Respiratory triggered DWI’s image quality in3T is better than1.5T (P <0.05), free-breathing DWI’s artifact score and image quality in1.5T are better than3T (P<0.05); Free-breathing DWI’s signal-to-noise ratio was higher than respiratory triggered and breathhold DWI. The signal-to-noise ratio of the gallbladder, right kidney, spleen and pancreas of3T were higher than1.5T, but the SNR of the liver was less than1.5T (P<0.05); Normal liver, gallbladder, kidney and pancreas’ADC values were not statistically different between1.5and3T (P>0.05), the ADC value of the spleen is the lowest one among these organs; The repeatability of most signal intensity’s measurement between two observers was very good, when b=100and800.Conclusion:3T respiratory triggered technology can obtain better DWI quality; And free-breathing DWI has the highest SNR; The ADC values of normal liver parenchyma, gallbladder, kidney, spleen and pancreas have no difference between 1.5T and3T. |
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