Research On Reducing The Radiation Of Lumber CT Scan Using Axial Protocol

Objective：Conduct basic research, to design new axial scan that can be used for lumbarspine scan.Then，explore low-dose axial scan protocol of the lumbar spine to get thelow-dose scan parameters.Methods:1.Scan the phantom using different scan protocols: helical scan protocol:120KV,300mAs, collimation128×0.625, pitch0.993, the standard reconstruction algorithms,1mm reconstruction thickness and0.5mm increment, FOV180mm. Axial scan protocol:120KV,300mAs collimation128×0.625, the standard reconstruction algorithms,1mmreconstruction thickness and0.5mm increment,FOV180mm. Then scan the phantomwith120KV,200mAs,150mAs,100mAs, try to discuss low dose scanning parameter.2Compare the data and images, combined with clinical and literature to determine axialprocedures apply to the lumbar low-dose scan.Results: The spatial resolution of the image of axial protocol and spiral protocol with thesame parameter are the same.The Density resolution and noise of the axial protocol arebetter than the spiral protocol.Conclusion: Lumber CT scan using is practicable,the parameters:120KV,200mAscollimation128×0.625, the standard reconstruction algorithms,1mm reconstructionthickness and0.5mm increment,FOV180mm. with the same image quality axial protocolcan reduce the radiation dose for33%.The second partObjective：To discuss the clinical the possibilities and the ability of reducing the radiationdose of low dose lumber CT scan using axial protocol.Methods and Material: Two hundreds of patients underwent lumber CT scan were randomly divided into the axial protocol group（experimental group A,B）and the Spiral CTgroup（control group C,D）,each of50cases.The new protocol of axial scan wereperformed in the experimental group， group A were routine-dose group and theparameter:120kV,300mAs,collimation128×0.625,1mm slice thickness and0.5mmincrement，FOV180mm. Group B were low-dose group and the scanning parameter:120kV,200mAs,the other parameters were the same to group A.The control group werescanned with the conventional spiral protocol.Group C were routine-dose group and thescanning parameter：120kV,300mAs, collimation128×0.625,1mm reconstruction slicethickness and0.5mm increment, pitch0.993,FOV180mm.Group D were low-dose groupand the scanning parameter:120kV,200mAs, other parameters were the same to groupC. The original image and the MPR were transferred to the PACS to be evaluated byexperienced doctors.Results：The two scanning protocol have the same image spatial resolution under thesame scanning parameters.The density resolution and noise of step scanning protocol arebetter than the conventional helical scan protocol Patients of the experimental groupreceiving radiation dose was lower than that of the control group, the dose (7.16mSv)of group A was lower than that of group C(8.44±0.23mSv)15%, the dose (4.77mSv)of group B was lower than that of group D (5.55±0.1mSv)14%(P <0.05), the dose ofgroup B lower than that of group C43%; the image quality of group A have no differencewith group C, the image quality of group B was significantly better than group D (P <0.05), the group B and group C have no significant difference (P>0.05) in image quality.Conclusion: Clinical experiment shows that: in the patient lumbar scan, with the samescanning parameters,the density resolution and noise of axial protocol are better than thehelical protocol scan. with the same image quality, axial protocol can reduce radiation dosefor43%, are the same with the basic experimental results.Low dose lumber CT scan usingstep-shoot CT is practicable, can greatly reduce the radiation dose.The third partObjective: Do the further low dose axial protocol adjustment test for the lumber CT scan.Methods: Select50cases patients that BMI≤22, as group E, use axial protocol, scan parameters:120KV,150mAs,collimationd128×0.625,standard alorithm,1mm reconstructionthickness and0.5mm increment,FOV180mm.. Recording radiation dose index(Computed Tomography Dose Index, CTDI)and the effective dose (Effective Dose, ED),the original image and the reconstructed images were transferred to the PACS system tobe evaluated by experienced doctors.Results: The index is238.6mGy·cm, the effective dose3.58mSv, image quality score3.96±0.79.Conclusion: Clinical application shows that, lumber scan using axial protocol can reducethe radiation dose about57%with the proper image quality, is a feasible method and havebroad application prospects.