The Value of Multi-Shot Echoplanar MR Imaging in the Diagnosis of Focal Hepatic Lesions: Comparison with OtherStandard MR Imagings

ABSTRACT

PURPOSE: To determine the diagnositic value of multi-shot echo-planar MR imaging (EPI) in focal hepaticlesions 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 Gdenhancement. MATERIALS AND METHODS: Seventeen patients with 18 focal hepatic lesions were retrospectivelyreviewed by two abdominal radiologists. The pathological or clinical results of hepatic lesions were nine cases ofhemangioma, four of hepatocellular carcinoma, one of peripheral cholangiocarcinoma, one of simple cyst, and ofhemangioma. By dividing the data acquisition period into eight interleaved segments, multi-shot EPI images wereobtained. This T2W spin echo eight-shot EPIs of the liver in one 18 second breath hold was compared with otherpulse sequences. The foci of review were lesion detectablity and characterization. For the former, SNR(signal tonoise ratio) of the liver and CNR(contrast to noise ratio) of the lesion to the liver were calculated ;to evaluatethe 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 lesionto liver CNR, EPI was superior to FMPSPGR, SE, and Gd SE, but inferior to FSE, Gd FMPSPGR(p<.01). For nonsolidlesions(hemangioma, cyst), EPI provided higher liver CNR than FMPSPGR, SE, or Gd-SE, but one that was poorer thanthat provided by FSE and Gd-FMPSPGR(p<.05). Among six pulse sequences, there was no statistically significantdifference in lesion to liver CNR in solid lesions. In the evaluation of liver to lesion CNR, multi-shot EPI wasalways inferior to FSE. CONCLUSION: We concluded that with regard to sensitivity and suseptibility, multi-shotEPI is inferior to T2W FSE. For SNR, EPI was the least satisfactory, though with the exception of FSE, EPIprovided a higher or comparable CNR than other pulse sequences, and this made lesion depiction easy, especially innonsolid lesions. It was, however, difficult to characterize lesions by using EPI alone to determine whether alesion was solid or nonsolid.