Comparison of free breathing and respiratory triggered diffusion-weighted imaging sequences for liver imaging

Table 1 Imaging parameters used for the study on a 1.5-T magnetic resonance imaging scanner

Sequence	TE (ms)	TR (ms)	Slice Thickness/0-mm gap (mm)	Time	Matrix size
T1-gradient dual echo	2.1 and 4.2	170	5	2 s × 19 s BH	320 × 219
T2 fast-spin echo	93	5331	5	5 min	256 × 135
Dynamic pre-Gd and post-Gd VIBE	2.65	2.65	3	16 s BH	288 × 192
FB-DWI	67	7900	5	4 min 44 s	128 × 104
SMS-DWI	56	5000	5	3 min 4 s	128 × 104
PACE-DWI	56	2600	5	5 min 58 s	128 × 104

VIBE: Volumetric interpolated breath-hold examination; FB-DWI: Free-breathing diffusion-weighted imaging; SMS-DWI: Simultaneous multislice diffusion-weighted imaging; PACE-DWI: Prospective acquisition correction diffusion-weighted imaging; BH: Breath hold; TE: Echo time; TR: Repetition time.

Table 2 Lesion type and distribution of the study patients

Lesion type	No. of patients	No. of lesions
Liver cyst	1	1
Treated metastasis	1	1
Desmoid tumor	2	2
Hemangioma	1	2
Metastatic thyroid cancer	1	3
Metastatic pancreatic cancer	1	4
Metastatic colon cancer	2	9
Hepatocellular carcinoma	5	11
Metastatic neuroendocrine tumor	6	23
Total	20	56

Table 3 Mean image quality scores by sequence for all readers

Sequence	Mean Score1	95% LCL	95% UCL
FB-DWI	3.15	2.79	3.51
PACE-DWI	4.48	4.12	4.85
SMS-DWI	4.22	3.85	4.58

¹The Likert scale ratings for image quality were: 5 = superior, 4 = somewhat superior, 3 = same, 2 = somewhat inferior, and 1 = inferior. Higher scores reflect higher image quality. DWI: Diffusion-weighted imaging; FB: Free breathing; PACE: Prospective acquisition correction; SMS: Simultaneous multislice; LCL: Lower confidence level; UCL: Upper confidence level.

Table 4 Summary of the mean apparent diffusion coefficient and standard deviation by sequence

Sequence1	N	Mean (mm2/s)	SD (mm2/s)	Min (mm2/s)	Median (mm2/s)	Max (mm2/s)
FB	56	1313.51	387.44	654.00	1290.38	2506.33
PACE	56	1273.28	403.30	453.71	1216.42	2401.55
SMS	56	1269.14	442.84	425.12	1155.53	2457.30
All	168	1285.31	409.87	425.12	1211.17	2506.33

¹There were no significant differences among the mean apparent diffusion coefficient values of the 3 sequences (P = 0.51 by likelihood ratio test of the linear mixed model). N: Number of lesions; ADC: Apparent diffusion coefficient; SD: Standard deviation; FB: Free breathing; PACE: Prospective acquisition correction; SMS: Simultaneous multislice.