Program Information
Minimization of Resolution Loss for CT Scans of the Elbow at Lateral Position
Y Zhou*, A Scott , Cedars-Sinai Medical Center, Irvine, CA
Presentations
SU-F-I-30 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:Resolution is vital in elbow CT in order to examine the details of fractures. However, it is significantly compromised when the elbow is at the lateral position due to the body attenuation and off-center position. We attempted to find the parameters to minimize the resolution loss while keeping the dose ALARA.
Methods:To simulate the medium and large patient respectively, an abdomen phantom (CIRS TE07) was used and then a fat-ring was added. A small tissue-equivalent phantom (CIRS TE02) simulating the elbow was connected to another smaller phantom (CIRS TE01). A resolution insert (CIRS QA) was placed inside the elbow phantom. The two-phantom set was first placed in the superior position and helical scans were performed using a GE VCT with 120 kVp, 0.531 pitch, 0.625 mm thickness and CTDI_vol of 21 mGy. Similar scans were performed after the set was moved to the body side with varied CTDI_vol (39- 90 mGy). Different choices were utilized including scan modes of "plus" (thicker slice profile) and "full", kernels of "edge", "bone" and "detail", and different ASIR fractions.
Results:Resolution deterioration was significant when the elbow phantom was at the body side. The scans with the "plus" mode improved the resolution as compared with the “full” mode. For the medium sized phantom, the CTDI_vol increase from 40 mGy to 67 mGy did not improve the resolution. For the large phantom, the CTDI_vol increase from 67 mGy to 80 mGy and 90 mGy did not improve the resolution either. Furthermore, ASIR blending bigger than 50% deteriorated the resolution.
Conclusion:Resolution loss can be minimized using scans with the "Plus" mode, bone kernel, and ASIR blending of 0%- 30%. CTDI_vol values larger than 40 mGy and larger than 67 mGy, for the medium sized and large sized phantoms, respectively, do not improve the resolution.
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