【摘要】 目的探讨64层螺旋 CT 颞骨低剂量扫描的可行性和合理性。方法应用 SomatomSensation 64层螺旋 CT,采用临床常用的颞骨螺旋扫描模式,分别以380、300、200、160、120、80 mA 的剂量对尸体头颅标本2具(4只耳)进行扫描,并对扫描所得图像进行多平面重组处理,然后用剂量头模和 CT 长杆电离室分别测试各 mA 下螺旋 CT 的 CT 剂量加权指数(CTDI_W)。横断面选取弓形下窝、前庭导水管、鼓膜张肌腱、面神经隐窝4个解剖结构,冠状面选取盾板、横嵴、面神经蛇眼征蜗窗4个解剖结构,双斜面重组图像选取锤骨、砧骨、镫骨、上骨半规管、耳蜗、面神经管6个解剖结构,分别对各 mA 组下重组图像进行统计评分处理,并筛选出能满足诊断的最低 mA 值。对5例(10只耳)患者进一步验证其可行性。结果当 mA 值由380降低至160时,CTDI_W由(47.8±2.7)mGy 降至(20.1±2.0)mGy。2组剂量差异有统计学意义(P<0.01),而解剖结构的显示无统计学意义(P>0.05)。结论适当降低管电流是一种切实可行的降低辐射剂量的颞骨扫描方法。更多还原

【Abstract】 Objective To study the rationality and possibility of 64 slice spiral CT in the examination of the temporal bone at low dose.Methods The same CT technique and temporal bone mode as those for clinical CT were used,two cranium specimens(four ears)were scanned with Somatom Sensation 64-slice spiral CT at different mA(380,300,200,160,120,80),and muhi-planar reformation was performed.The CT dose index at different mA groups were measured by 10 cm pencil ionization chamber and head dose phantom.Four anatomic structures on axial images(subarcuate fossa,tendon of tensor tympani, facial recess,etc),four anatomic structures on coronal images(scute,crista transversa,fenestra cochleae, etc)and six anatomic structures on double oblique images(malleus,incus,stirrup bone,upper bony semicircular,etc)were chosen to evaluate and grade the reformation images among different mA groups,and to determine the minimum mA value.Ten ears of five patients were used to test the validity of the minimum mA value.Results CT radiation dose was significantly reduced from(47.8±2.7)to(20.1±2.0)raCy (P<0.01)when mA decreased from 380 mA to 160 mA.No significant difference in displaying anatomic structures between the two mA protocols.Conclusion It is a feasible borne temporal scanning method to decrease the radiation dose by decreasing mA appropriately.更多还原