Program Information
The Impact of the Lesion Size and Dose On the Low Contrast Enhancement Using Adaptive Statistical Iterative Reconstruction for Variable Pediatric Patient Sizes in Abdominal CT
Y Zhou*, J Nute , A Scott , C Lee , C Kim , Cedars-Sinai Medical Center, Los Angeles, CA
Presentations
TH-EF-601-12 (Thursday, August 3, 2017) 1:00 PM - 3:00 PM Room: 601
Purpose: Adaptive statistical iterative reconstruction (ASIR) is used to enhance the low contrast in CT. However, the degree of the enhancement over the filtered backprojected reconstruction (FBP) may be often understood as only dependent on the ASIR blending fraction. We devised the experiment to study the dependency on other important factors, such as the lesion size, patient size, and dose.
Methods: Four pediatric abdomen phantoms (lateral size: 10-20 cm) were utilized. Helical scans were performed on a GE 64-slice VCT at five dose levels (0.8- 30 mGy). The images were reconstructed with variable ASIR fractions (0 - 100%). The noise images, obtained using subtraction from nearest neighbor slices, were partitioned into matrices of square cells scaled 1.8 mm – 10 mm to match the lesion sizes of interest. The noise at each cell size was quantified by the standard deviation (sd) of the cell mean pixel values distribution. Upon verifying that the distributions follow Gaussian, the statistically defined minimum detectable contrast (MDC) was applied to ASIR reconstructed images. The normalized MDC (N_MDC) was defined as the ratio of the MDC with ASIR to the MDC with FBP. N_MDC was obtained at each cell size from different ASIR blending fractions at variable dose levels.
Results: N_MDC was found to linearly decrease as the ASIR blending fraction increases. The slope of the N_MDC, however, depends on the lesion size, patient size and dose. The slope was fitted against the lesion size by a power law with more contrast enhancement at smaller lesion size. The enhancement was also found to be more pronounced as the phantom size increases or as the dose decreases.
Conclusion: The low contrast enhancement using ASIR in pediatric abdomen CT not only depends on the ASIR blending fraction, but also depends on the lesion size, patient size and dose.
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