Abstract
Purpose :
To determine the diagnositic value of multi-shot echoplanar MR imaging (EPI) in focal hepatic lesions by quantitatively comparing this with other standard MR sequences such as FSE (fast spin echo) T2WI, SE (spin echo) T1WI with and without Gd enhancement, FMPSPGR (fast multiplanar spoiled GRASS) with and without Gd enhancement.
Materials and Methods :
Seventeen patients with 18 focal hepatic lesions were retrospectively reviewed by two abdominal radiologists. The pathological or clinical results of hepatic lesions were nine cases of hemangioma, four or hepatocellular carcinoma, one of peripheral cholangiocarcinoma, one of simple cyst, and of hemangioma. By dividing the data acquisition period into eight interleaved segments, multi-shot EPI images were obtained. This T2W spin echo eight-shot EPIs of the liver in one 18 second breath hold was compared with other pulse sequences. The foci of review were lesion detectablity and characterization. For the former, SNR (signal to noise ratio) of the liver and CNR (contrast to noise ratio) of the lesion to the liver were calculated å to evaluate the latter, a separate calculation of lesion to liver CNR for each solid and nonsolid lesion group was performed.
Results :
Among six pulse sequences, multi-shot EPI provided the poorest liver SNR(p < .01). With regard to lesion to liver CNR, EPI was superior to FMPSPGR, SE, and Gd SE, but inferior to FSE, Gd FMPSPGR(p < .01)· For nonsolid lesions (hemangioma, cyst), EPI provided higher liver CNR than FMPSPGR, SE, or Gd-SE, but one that was poorer than that provided by FSE and Gd-FMPSPGR(p〈 .05). Among six pulse sequences, there was no statistically significant difference in lesion to liver CNR in solid lesions. In the evaluation of liver to lesion CNR, multi-shot EPI was always inferior to FSE.
Conclusion :
We concluded that with regard to sensitivity and suseptibility, multi-shot EPI is inferior to T2W FSE. For SNR, EPI was the least satisfactory, though with the exception of FSE, EPI provided a higher or comparable CNR than other pulse sequences, and this made lesion depiction easy, especially in nonsolid lesions. It was, however, difficult to characterize lesions by using EPI alone to determine whether a lesion was solid or nonsolid.
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![]() | Fig. 1.Comparison of (A) eight-shot spin echo EPI (Β) T2 weighted FSE (C) FMPSPGR (D) SE (E) Gd-FMPSPGR (F) Gd-SE images obtained in a 47-year-old male with a hepatocelluar carcinoma (arrow in FMPSPGR) in liver dome. EPI provide the most grainy images due to low SNR. But the contrast between the tumor and liver is very striking in comparison with other pulse sequences. We could not determine the lesion solid or nonsolid with EPI alone. |
![]() | Fig. 2.Comparison of (A) eight-shot spin echo EPI, (Β) T2 weighted FSE, (C) FMPSPGR, (D) SE, (E) Gd-FMPSPGR, (F) Gd-SE images obtained in a 36-year-old male with a small hemangioma (arrow in FMPSPGR) in segment 5 near the gall bladder. This nonsolid lesion is depicted better with EPI than FMPSPGR, SE, and Gd SE. As liver signal nulls in FSE, the CNR of FSE is higher than that of EPI. |
Tabel 1.
Quantitive Assessment of Liver SNR, Spleen-to-Liver CNR, and Lesion-to-Liver CNR in 18 Lesions
Table 2.
Quantitative Assessment in Solid and Non-solid Lesions