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A potential risk of overestimating apparent diffusion coefficient in parotid glands.

Liu YJ, Lee YH, Chang HC, Huang TY, Chiu HC, Wang CW, Chiou TW, Hsu K, Juan CJ, Huang GS, Hsu HH - PLoS ONE (2015)

Bottom Line: A P value less than 0.05 was considered statistically significant.The mean error percentage decreased as the number of excitations increased on all images, and, it was smallest on T2WI, followed by DWI and ADC in an increasing order.Transient signal loss on DWI was successfully detected by dynamic EPDWI.

View Article: PubMed Central - PubMed

Affiliation: Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan, Republic of China.

ABSTRACT

Objectives: To investigate transient signal loss on diffusion weighted images (DWI) and overestimation of apparent diffusion coefficient (ADC) in parotid glands using single shot echoplanar DWI (EPDWI).

Materials and methods: This study enrolled 6 healthy subjects and 7 patients receiving radiotherapy. All participants received dynamic EPDWI with a total of 8 repetitions. Imaging quality of DWI was evaluated. Probability of severe overestimation of ADC (soADC), defined by an ADC ratio more than 1.2, was calculated. Error on T2WI, DWI, and ADC was computed. Statistical analysis included paired Student t testing and Mann-Whitney U test. A P value less than 0.05 was considered statistically significant.

Results: Transient signal loss was visually detected on some excitations of DWI but not on T2WI or mean DWI. soADC occurred randomly among 8 excitations and 3 directions of diffusion encoding gradients. Probability of soADC was significantly higher in radiotherapy group (42.86%) than in healthy group (24.39%). The mean error percentage decreased as the number of excitations increased on all images, and, it was smallest on T2WI, followed by DWI and ADC in an increasing order.

Conclusions: Transient signal loss on DWI was successfully detected by dynamic EPDWI. The signal loss on DWI and overestimation of ADC could be partially remedied by increasing the number of excitations.

No MeSH data available.


Error percentage (mean and standard deviation) of T2WI, DWI(x, y and z), ADC(x, y and z) with different NEX numbers in healthy group (6A) and radiotherapy (RT) group (6B).
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pone.0124118.g006: Error percentage (mean and standard deviation) of T2WI, DWI(x, y and z), ADC(x, y and z) with different NEX numbers in healthy group (6A) and radiotherapy (RT) group (6B).

Mentions: Fig 6 demonstrated error percentages of T2WI, DWIx, DWIy, DWIz, ADCx, ADCy and ADCz in healthy and radiotherapy groups with NEX varying from 3 to 8. It showed that the larger the NEX the lower the error percentage in all images and along all directions of diffusion encoding gradients. In the healthy group, the mean error percentage was 6.32% and 4.37% on T2WI, 13.03% and 9.74% on DWIx, 12.24% and 9.38% on DWIy, 12.52% and 9.00% on DWIz, 19.05% and 15.29% on ADCx, 19.80% and 16.27% on ADCy, 20.45% and 15.17% on ADCz with a NEX of 4 and 8, respectively, (all P < 0.001). In the radiotherapy group, the mean error percentage was 8.76% and 6.06% on T2WI, 14.97% and 11.28% on DWIx, 14.37% and 10.76% on DWIy, 15.14% and 10.87% on DWIz, 23.41% and 19.03% on ADCx, 28.95% and 21.68% on ADCy, and 26.17% and 20.58%on ADCz with a NEX number of 4 and 8, respectively, (all P < 0.001). The error percentage was smallest on T2WI, followed by DWI and ADC in an increasing order regarding all directions of diffusion encoding gradients and all NEXs. The trends of error percentage regarding the NEX and among T2WI, DWI and ADC remained similar between healthy and radiotherapy groups. Nevertheless, the error percentage was higher in the radiotherapy group than in the healthy group at all numbers of excitations and on all kinds of images (all P < 0.001).


A potential risk of overestimating apparent diffusion coefficient in parotid glands.

Liu YJ, Lee YH, Chang HC, Huang TY, Chiu HC, Wang CW, Chiou TW, Hsu K, Juan CJ, Huang GS, Hsu HH - PLoS ONE (2015)

Error percentage (mean and standard deviation) of T2WI, DWI(x, y and z), ADC(x, y and z) with different NEX numbers in healthy group (6A) and radiotherapy (RT) group (6B).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4414616&req=5

pone.0124118.g006: Error percentage (mean and standard deviation) of T2WI, DWI(x, y and z), ADC(x, y and z) with different NEX numbers in healthy group (6A) and radiotherapy (RT) group (6B).
Mentions: Fig 6 demonstrated error percentages of T2WI, DWIx, DWIy, DWIz, ADCx, ADCy and ADCz in healthy and radiotherapy groups with NEX varying from 3 to 8. It showed that the larger the NEX the lower the error percentage in all images and along all directions of diffusion encoding gradients. In the healthy group, the mean error percentage was 6.32% and 4.37% on T2WI, 13.03% and 9.74% on DWIx, 12.24% and 9.38% on DWIy, 12.52% and 9.00% on DWIz, 19.05% and 15.29% on ADCx, 19.80% and 16.27% on ADCy, 20.45% and 15.17% on ADCz with a NEX of 4 and 8, respectively, (all P < 0.001). In the radiotherapy group, the mean error percentage was 8.76% and 6.06% on T2WI, 14.97% and 11.28% on DWIx, 14.37% and 10.76% on DWIy, 15.14% and 10.87% on DWIz, 23.41% and 19.03% on ADCx, 28.95% and 21.68% on ADCy, and 26.17% and 20.58%on ADCz with a NEX number of 4 and 8, respectively, (all P < 0.001). The error percentage was smallest on T2WI, followed by DWI and ADC in an increasing order regarding all directions of diffusion encoding gradients and all NEXs. The trends of error percentage regarding the NEX and among T2WI, DWI and ADC remained similar between healthy and radiotherapy groups. Nevertheless, the error percentage was higher in the radiotherapy group than in the healthy group at all numbers of excitations and on all kinds of images (all P < 0.001).

Bottom Line: A P value less than 0.05 was considered statistically significant.The mean error percentage decreased as the number of excitations increased on all images, and, it was smallest on T2WI, followed by DWI and ADC in an increasing order.Transient signal loss on DWI was successfully detected by dynamic EPDWI.

View Article: PubMed Central - PubMed

Affiliation: Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan, Republic of China.

ABSTRACT

Objectives: To investigate transient signal loss on diffusion weighted images (DWI) and overestimation of apparent diffusion coefficient (ADC) in parotid glands using single shot echoplanar DWI (EPDWI).

Materials and methods: This study enrolled 6 healthy subjects and 7 patients receiving radiotherapy. All participants received dynamic EPDWI with a total of 8 repetitions. Imaging quality of DWI was evaluated. Probability of severe overestimation of ADC (soADC), defined by an ADC ratio more than 1.2, was calculated. Error on T2WI, DWI, and ADC was computed. Statistical analysis included paired Student t testing and Mann-Whitney U test. A P value less than 0.05 was considered statistically significant.

Results: Transient signal loss was visually detected on some excitations of DWI but not on T2WI or mean DWI. soADC occurred randomly among 8 excitations and 3 directions of diffusion encoding gradients. Probability of soADC was significantly higher in radiotherapy group (42.86%) than in healthy group (24.39%). The mean error percentage decreased as the number of excitations increased on all images, and, it was smallest on T2WI, followed by DWI and ADC in an increasing order.

Conclusions: Transient signal loss on DWI was successfully detected by dynamic EPDWI. The signal loss on DWI and overestimation of ADC could be partially remedied by increasing the number of excitations.

No MeSH data available.