PATIENT DOSE REDUCTION IN COMPUTED TOMOGRAPHY AT MEDSTAR GEORGETOWN UNIVERSITY HOSPITAL: OPTIMIZATION OF ABDOMINAL ADULT PROTOCOL AND TRAINING OF REFERRING PHYSICIANS
Smith, David A
Dose reduction in computed tomography (CT) has two components, elimination of unnecessary scans and optimization of justified exams. Several scientific articles have been published addressing issues and techniques for optimizing CT protocols. The use of iterative reconstruction (IR) algorithms predominates as it results in a better image quality by cutting out noise from the image, which allows for significant dose reduction. Contrast to noise ratio (CNR) is widely used for image evaluation. The aim of the study is to propose and apply a phantom-based method for optimization in CT with CNR calculations using different IR levels. The CT CatPhan 504 and PET/CT Biograph Siemens model (IR:SAFIRE) were employed for all image acquisitions. Abdominal adult protocol was chosen as the phantom simulates better this area. Region of interest analysis (ROI) included ROIs of about 0.3 cm2 for teflon and 2 cm2 for background. The analysis was performed based on two methods. In the first method, the volume computed tomography dose index (CTDIv) was kept constant and the SAFIRE levels were changed to determine if a better image quality could be achieved. The second method included comparison of CTDIv and CNR with respect to the baseline CNR. Measurements of CTDIw were determined using the 32 cm acrylic phantom for protocol evaluation. Local diagnostic reference levels (LDRLs) were lower than the national (NDRLs): 17 mGy compared to 25 mGy, respectively. However, both LDRL and NDRL are higher than the respective European DRL (15 mGy). The CNR baseline was found to be 78.40. A total of 6 out of 174 images analyzed passed the CNR and dose criteria. A 15% dose reduction and 10% CNR improvement were observed. For the same dose, a CNR increase of about 25% was found. Therefore, the use of higher SAFIRE levels (4, 5) is recommended. Comparison with NO SAFIRE indicated a CNR improvement of 55% for the same protocol parameters. While for approximately equal CNR, a dose reduction of 75% was achieved. In conclusion, the present study proposes an efficient phantom-based method as a first step of CT protocol optimization. Besides optimization, population dose reduction can be achieved by reducing or eliminating unnesccessary scans. Efficient and continuous training of the health providers is mandated to increase the efficacy and implementation of dose reduction strategies.
MetadataShow full item record
Showing items related by title, author, creator and subject.
Medical Decision Making Regarding Computed Tomographic Radiation Dose and Associated Risk: The Patient's Perspective Caoili, Elaine M.; Cohan, Richard H.; Ellis, James H.; Dillman, Jonathan; Schipper, Matthew J.; Francis, Isaac R. (2009-06-08)