Objective To measure the sensitivity and specificity of gradient echo T*_2(GRE-T*_2) to subarachnoid haemorrhage (SAH). Methods 12 patients with SAH underwent MRI using T_1WI, T_2WI, FLAIR, GRE-T*_2 sequences and CT as well. Results (1)In the acute-stage of the patients, SAH was seen as an area of high signal intensity as compared with the surrounding cerebrospinal fluid in 66.6% of the cases on T_1-weighted images, and in 100% on FLAIR images; low signal intensities were seen in 50.0% of the cases on T_2-weighted images, and in 100% on GRE-T*_2-weighted images; (2) In the subacute of the patients, SAH was detected on T_1-weighted images (25.0% of cases), FLAIR (25.0%), T_2-weighted images (0), GRE-T*_2-weighted images (100.0%); (3) In the patients with atypical SAH, both CT and FLAIR sequence in MRI were negative for SAH, while lumber acupuncture and GRE-T*_2 had positive findings. Conclusion GRE-T*_2 is the most sensitive sequence of MRI for detecting acute and subacute SAH and has significant advantages over CT in the detection of subacute and atypical SAH.

Objective To investigate the imaging manifestations and pathological basis of hepatic angiosarcoma(HAS).Methods The CT and MRI findings of 12 patients with HAS confirmed by pathology were analyzed retrospectively and compared with pathological findings.Results Based on morphological classification,the 12 cases of HAS were categorized into three types:massive patterns(n=3),mixed patterns of mass with nodules(n=2),and diffuse infiltration patterns(n=7).Hemorrhage was observed in 9 cases,and necrosis was present in all 12 cases.The massive patterns exhibited peripheral or nodular,patchy,annular,and cord-like enhancement patterns during the arterial phase,with increasing enhancement during the portal and delayed phases.The mixed patterns of mass with nodules demonstrated mild enhancement around the margin or in patchy and spotty structures during the arterial phase,progressing to expansive enhancement during the portal and delayed phases.Four of the seven diffuse infiltration patterns presented with mesh enhancement during the arterial phase,which expanded and became diffuse during the portal phase,accompanied by progressively enlarged enhancing nodules.In the delayed phase,the lesions were fused.The other three cases showed diffuse nodular enhancement during the arterial phase followed by increased enhancement during both portal phase and delayed phase.Regardless of subtype,focal fusion occurred during the delayed phase when multiple intrahepatic lesions were present,and the hemorrhagic and necrotic parts did not enhance.Conclusion The imaging characteristics of HAS include heterogeneous and progressive enhancement,often accompanied by hemorrhage,cystic change,and necrosis.