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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.


Related in: MedlinePlus

Illustration of transient signal loss on DWI.(A) Mean T2WI and mean DWI show apparent imaging distortion and signal loss (*) on the posterior border of the bilateral parotid glands. (B) Magnified mean DWI and 1st to 8th excitations of DWI of the rectangular ROI encompassing the left parotid gland show patchy areas of signal loss (arrows) in 3rd, 6th and 8th excitations.
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pone.0124118.g002: Illustration of transient signal loss on DWI.(A) Mean T2WI and mean DWI show apparent imaging distortion and signal loss (*) on the posterior border of the bilateral parotid glands. (B) Magnified mean DWI and 1st to 8th excitations of DWI of the rectangular ROI encompassing the left parotid gland show patchy areas of signal loss (arrows) in 3rd, 6th and 8th excitations.

Mentions: EPDWI was successfully acquired in all subjects. An example of EPDWI containing parotid glands was displayed in Fig 2. Geometric distortion and concurrent signal loss involving the posterior portion of bilateral parotid glands were obviously seen on both T2WI and mean DWI (Fig 2A). Prominent signal loss involving the left parotid gland was also demonstrated on several excitations of DWI (Fig 2B). Such transient signal loss was neither detected on T2WI, nor on mean DWI. Accordingly, it was necessary to perform an excitation-by-excitation analysis of DWI to catch such transient signal loss. In our study, a total of 464 ROIs (2 ROIs per slice, 5 slices and 8 excitations per subject in 5 subjects plus 2 ROIs per slice, 4 slices and 8 excitations in 1 subject, who had smaller parotid glands) in healthy subjects and 448 ROIs (2 ROIs per slice, 4 slices and 8 excitations per patient in 7 patients) in radiotherapy patients, respectively, were employed for further analysis.


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)

Illustration of transient signal loss on DWI.(A) Mean T2WI and mean DWI show apparent imaging distortion and signal loss (*) on the posterior border of the bilateral parotid glands. (B) Magnified mean DWI and 1st to 8th excitations of DWI of the rectangular ROI encompassing the left parotid gland show patchy areas of signal loss (arrows) in 3rd, 6th and 8th excitations.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0124118.g002: Illustration of transient signal loss on DWI.(A) Mean T2WI and mean DWI show apparent imaging distortion and signal loss (*) on the posterior border of the bilateral parotid glands. (B) Magnified mean DWI and 1st to 8th excitations of DWI of the rectangular ROI encompassing the left parotid gland show patchy areas of signal loss (arrows) in 3rd, 6th and 8th excitations.
Mentions: EPDWI was successfully acquired in all subjects. An example of EPDWI containing parotid glands was displayed in Fig 2. Geometric distortion and concurrent signal loss involving the posterior portion of bilateral parotid glands were obviously seen on both T2WI and mean DWI (Fig 2A). Prominent signal loss involving the left parotid gland was also demonstrated on several excitations of DWI (Fig 2B). Such transient signal loss was neither detected on T2WI, nor on mean DWI. Accordingly, it was necessary to perform an excitation-by-excitation analysis of DWI to catch such transient signal loss. In our study, a total of 464 ROIs (2 ROIs per slice, 5 slices and 8 excitations per subject in 5 subjects plus 2 ROIs per slice, 4 slices and 8 excitations in 1 subject, who had smaller parotid glands) in healthy subjects and 448 ROIs (2 ROIs per slice, 4 slices and 8 excitations per patient in 7 patients) in radiotherapy patients, respectively, were employed for further analysis.

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.


Related in: MedlinePlus