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