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Applying Approaches in AAPM TG Reports 204 and 220 for Measuring Patient Size Surrogates On 884 Patients Including Characterization of Anomalies
C Burton*, T Szczykutowicz , University Wisconsin-Madison, Madison, WI
Presentations
SU-H4-GePD-I-2 (Sunday, July 30, 2017) 4:30 PM - 5:00 PM Room: Imaging ePoster Lounge
Purpose: The purpose of our study is to use clinical data to confirm the results in AAPM TG report 204 and 220. We compare patient size surrogates: effective diameter (DE) and water-equivalent diameter (DW) with each other and lateral (LAT), anterior-posterior (AP), and (AP+LAT)/2 measurements.
Methods: A total of 884 routine scans were analyzed: 297 adult abdomen and pelvis, 300 adult chest, 87 pediatric abdomen pelvis, and 200 adult head. We calculated AP, LAT, DE, and DW using formulas from AAPM TG 204 and 220. We plotted D¬E and DW against (AP + LAT)/2, AP, LAT, and to each other. For data analysis we applied a linear fit, linear regression (R2) and 95% confidence intervals. Adult chest was separated into shoulder, thorax, and abdomen to analyze how each sub-region influenced the overall size surrogate metrics. We considered points outside the 95% confidence interval to be outliers and we analyzed each of them to characterize deviations from the excellent correlation shown in the AAPM reports that may be present in the clinic.
Results: Excellent correlation between (AP+LAT)/2 with DE (R2=0.997) and DW (R2=0.94) for all data points and DE (R2=0.997) and DW (R2=0.81) for head only. There is also excellent correlation between DE and DW with LAT and AP. Patient outliers were caused by patient conditions like excess gas in the GI tract, exceptionally low BMI, and cranial metaphyseal dysplasia.
Conclusion: We confirmed results in AAPM 204 and 220 using CT axial images where we show excellent correlation between patient surrogates DE and DW to LAT, AP and (AP+LAT)/2 with (AP+LAT)/2 being the best estimate. We show that methodologies of the size surrogates from AAPM 204 and 220 can be applied to different body regions and identified some patient conditions which cause TG 204 to fail.
Funding Support, Disclosures, and Conflict of Interest: CB received research funding GE Healthcare. TPS Equipment Grant and Consultant GE HealthCare; supplies CT protocols to GE HealthCare under a licensing agreement; the founder of protocolshare.org
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