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. 2025 Apr 1;15(4):3771-3778.
doi: 10.21037/qims-2025-270. Epub 2025 Mar 13.

The impacts of time of echo (TE) and time of repetition (TR) on diffusion-derived 'vessel density' (DDVD) measurement: examples of liver, spleen, and hepatocellular carcinoma

Yì Xiáng J Wáng  1 , Cai-Ying Li  1 , Dian-Qi Yao  1 , Sheng-Nan Tang  1 , Ben-Heng Xiao  1
Affiliations

The impacts of time of echo (TE) and time of repetition (TR) on diffusion-derived 'vessel density' (DDVD) measurement: examples of liver, spleen, and hepatocellular carcinoma

Yì Xiáng J Wáng et al. Quant Imaging Med Surg. .
No abstract available

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-270/coif). Y.X.J.W. serves as the Editor-in-Chief of Quantitative Imaging in Medicine and Surgery. Y.X.J.W. is the founder of Yingran Medicals Ltd., which develops medical image-based diagnostics software. B.H.X. contributed to the development of Yingran Medicals Ltd. The other authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Liver DDVD and spleen DDVD comparison with healthy volunteer studies. (A) 1.5 T scan had 26 subjects and 3.0 T scan had 19 subjects. 1.5 T scan had TR of 1,600 ms (acquired with respiratory gating) and TE of 63 ms, and 3.0 T scan had TR of 1,600 ms and TE of 59 ms (acquired with free breathing). For liver and spleen DDVD measurement, when the 2nd b-value is 1 or 2 mm2/s, DDVDliver is approximately similar to DDVDspleen (arrows in A). (B) While spleen shows a higher signal on DWI b=0 mm2/s image (B1), on the maps of DDVDb0b1 (B2) and DDVDb0b2 (B3), liver signal and spleen signal appear similiar (1.5 T data). (C) An increasing 2nd b-value is associated with a slowly increasing DDVDliver/DDVDspleen ratio, and this is slightly more apparent with 3.0 T data. Since when 2nd b-value is >2 s/mm2, DDVD mainly reflects blood volume, results in (C) is consistent with the fact that liver has a slightly higher blood volume as shown with perfusion CT and nuclear medicine studies (13). Data of this graph is based on (13). DDVD, diffusion-derived ‘vessel density’; TE, time of echo; TR, time of repetition.
Figure 2
Figure 2
HCC measure to surround liver parenchyma measure ratios of perfusion CT measured blood volume (A), blood flow speed (B), and DDVD (C). The DDVDHCC/DDVDliver ratio agrees well with the HCC/liver ratio of perfusion CT measured blood volume. (A) and (B) are the based on a random selection of the reports of Pahwa et al. (22), Ippolito et al. (23), Sahani et al. (24), Lewin et al. (25), Mulé et al. (26), Ganga et al. (27), Sacco et al. (28), Wang et al. (29), Li JP et al. (30), Li XR et al. (31). (C) is based on the authors’ own data of 26 cases of HCC. DDVDr was measured at 3.0 T, with a TE of 59 ms (TR: 1,600 ms, acquired with free breathing) and b=0, 2 s/mm2. CT, computed tomography; DDVD, diffusion-derived ‘vessel density’; DDVDr, DDVD ratio; HCC, hepatocellular carcinoma; SD, standard deviation; TE, time of echo; TR, time of repetition.
Figure 3
Figure 3
DDVDspleen/DDVDliver ratio for data acquired with TE being 84 ms (TR =2,500 ms, acquired with respiratory gating) and 2nd b-value being 10 s/mm2. (A) Non-tumor regions of the liver were measured. (B,C) Two cases’ DDVD maps calculated with b=0 and b=10 s/mm2 DWI images, with spleen (S) showing higher signal than liver (L). T denotes the tumor regions. Unit for TR and TE is millisecond. CI, confidence interval; DDVD, diffusion-derived ‘vessel density’; DWI, diffusion-weighted imaging; FNH, focal nodular hyperplasia; HCC, hepatocellular carcinoma; Mets, metastasis; TE, time of echo; TR, time of repetition.
Figure 4
Figure 4
Impact of TR on DDVDspleen/DDVDliver ratio. (A) The measures of (only) three heathy volunteers (mean and SD). When TR is 2,000 ms and TE is 46 ms (acquired with free breathing), DDVDspleen/DDVDliver ratio is 1.13 thus being approximately consistent with results in Figure 1 and also showing shortening of TE has no substantial impact on DDVDspleen/DDVDliver ratio. Shortening of TR to 1,000, to 500, to 300, and to 200 ms is associated with an increase of DDVDspleen/DDVDliver ratio. (B) DDVDspleen/DDVDliver ratio of seven HCC cases (acquired with breathhold). Non-tumor regions of the liver were measured. Three cases did not have liver fibrosis, and four cases had grade-1 liver fibrosis. DDVDspleen/DDVDliver ratio is presented with scatter plot and mean/SD. It is noted that for all seven cases, DDVDspleen is measured higher than DDVDliver. DDVDspleen/DDVDliver ratio is higher when the 2nd b-value is 2 s/mm2 than the 2nd b-value is 10 s/mm2. (C) An example DDVD map calculated with b=0 and b=2 s/mm2 DWI images [case from (B)], with spleen (S) showing higher signal than liver (L). Unit for TR and TE is millisecond. DDVD, diffusion-derived ‘vessel density’; G, gastric fluid; HCC, hepatocellular carcinoma; SD, standard deviation; TE, time of echo; TR, time of repetition.
Figure 5
Figure 5
Compared with the cases of a long TR and a short/moderate TE (see Figures 2,4 results), both the applications of a long TE of 84 or a short TR of 313 lead to a higher DDVDHCC/DDVDliver ratio. Data A had 56 cases of HCC, and image data acquisition at 3.0 T had TR of 2,500 ms (acquired with respiratory gating) and TE of 84 ms. Data B had 70 cases of HCC, and image data acquisition at 3.0 T had TR of 313 ms (acquired with breathhold) and TE of 38 ms. The 2nd b-value for DDVD is both 10 s/mm2 for the data in this graph. Unit for TR and TE is millisecond. DDVD, diffusion-derived ‘vessel density’; HCC, hepatocellular carcinoma; SD, standard deviation; TE, time of echo; TR, time of repetition.
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