Objective To investigate the value of prone-position MRI of lumbar spine for diagnosing pediatric occult tethered cord syndrome(OTCS).Methods A total of 67 children with suspected tethered cord syndrome(TCS)and confirmed OTCS by surgery were prospectively enrolled as OTCS group,while 73 healthy subjects were recruited as control group.Supine-and prone-position lumbar MR examinations were performed in both groups.The position of filum terminale on prone axial T2WI and the presence or absence of"sunset sign"(i.e.filum terminale located within the dorsal 1/2 of spinal canal on prone axial T2WI)were observed,spinal cord conus mobility was calculated.The efficacy of"sunset sign"for diagnosing OTCS in children was calculated through comparison between groups.Receiver operating characteristic curve was drawn,the area under the curve(AUC)was calculated to evaluate the diagnostic efficacy of spinal cord conus mobility.Results On prone-position axial T2WI,"sunset sign"was found in 58 cases(58/67,86.57％)but not in 9 cases(9/67,13.43％)in OTCS group,which was not even observed in control group.The sensitivity of"sunset sign"for diagnosing pediatric OTCS was 86.57％(58/67),with specificity of 100％(73/73),positive predictive value of 100％(58/58)and negative predictive value of 89.02％(73/82).The spinal cord conus mobility was(19.30±5.89)％in OTCS group and(31.71±6.58)％in control group,being statistically different between groups(t=-11.722,P＜0.001).The sensitivity,specificity and AUC of spinal cord conus mobility for diagnosing pediatric OTCS was 80.60％,90.41％and 0.920,respectively.Conclusion Prone-position MRI of lumbar spine could be used in diagnosing pediatric OTCS.

Objective To investigate the value of prone-position MRI of lumbar spine for diagnosing pediatric occult tethered cord syndrome(OTCS).Methods A total of 67 children with suspected tethered cord syndrome(TCS)and confirmed OTCS by surgery were prospectively enrolled as OTCS group,while 73 healthy subjects were recruited as control group.Supine-and prone-position lumbar MR examinations were performed in both groups.The position of filum terminale on prone axial T2WI and the presence or absence of"sunset sign"(i.e.filum terminale located within the dorsal 1/2 of spinal canal on prone axial T2WI)were observed,spinal cord conus mobility was calculated.The efficacy of"sunset sign"for diagnosing OTCS in children was calculated through comparison between groups.Receiver operating characteristic curve was drawn,the area under the curve(AUC)was calculated to evaluate the diagnostic efficacy of spinal cord conus mobility.Results On prone-position axial T2WI,"sunset sign"was found in 58 cases(58/67,86.57％)but not in 9 cases(9/67,13.43％)in OTCS group,which was not even observed in control group.The sensitivity of"sunset sign"for diagnosing pediatric OTCS was 86.57％(58/67),with specificity of 100％(73/73),positive predictive value of 100％(58/58)and negative predictive value of 89.02％(73/82).The spinal cord conus mobility was(19.30±5.89)％in OTCS group and(31.71±6.58)％in control group,being statistically different between groups(t=-11.722,P＜0.001).The sensitivity,specificity and AUC of spinal cord conus mobility for diagnosing pediatric OTCS was 80.60％,90.41％and 0.920,respectively.Conclusion Prone-position MRI of lumbar spine could be used in diagnosing pediatric OTCS.

Purpose To explore the CT features of renal cell carcinoma with cystic change and to compare them with pathological ifndings, so as to improve its diagnostic accuracy. Materials and Methods A retrospective study was carried out in 44 cases of renal cell carcinoma with cystic change conifrmed surgically and pathologically, among which 10 were multilocular cystic renal cell carcinoma, 21 were renal clear cell carcinoma and 13 were papillary renal cell carcinoma. The CT features of these 3 kinds of diseases were analyzed comparatively. Results All of 10 cases of multilocular cystic renal cell carcinoma appeared to have multilocular cysts with thin cystic walls and septa. The mean CT value of cyst was (15.8±5.6) HU. The diameter of wall nodule was larger than 5 mm in 4 cases. The contrast-enhanced CT scan showed that the cystic walls and septa had early moderate enhancement in 8 cases. Among 21 cases of renal clear cell carcinoma, 9 presented to have multilocular cysts with thick cystic walls and septa. The mean CT value of cyst was (32.5±6.7) HU. The diameter of wall nodule was larger than 5 mm in 19 cases. The cystic walls and septa had obvious early enhancement in 20 cases. As to the 13 cases of papillary renal cell carcinoma, 4 appeared to have multilocular cysts with thick cystic walls and septa. The mean CT value of cyst was (26.1±5.6) HU. The diameter of wall nodule was larger than 5mm in 12 cases, and 12 cases appeared to have slight to moderate delayed enhancement. Conclusion The CT features of renal cell carcinoma with cystic change could be used in differential diagnosis, such as with or without pseudocapsule, mean CT value of cyst, thickness of cystic wall and septum, size, boundary, and enhancement of nodule.