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MO‐D‐I‐609‐05: Uncertainties in Measuring Activity Concetrations of a Moving Phantom Aquired with Standard Clinical PET/CT Protocol
Author(s) -
Pevsner A,
Mageras G,
Nehmeh S,
Humm J,
Erdi Y
Publication year - 2005
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1998241
Subject(s) - imaging phantom , nuclear medicine , physics , medical imaging , biomedical engineering , optics , computer science , medicine , artificial intelligence
Purpose: We have evaluated the magnitude of errors associated with measuring activities in moving objects in PET/CT images acquired using standard helical/clinical CT data. Method and Materials: In this study we used 2001 NEMA IEC Body phantom which has six fillable spheres with diameters of 37, 28, 22, 17, 13 and 10 mm. The target‐to‐background 18 FDG activity in a phantom was 8:1. A motorized platform moved the phantom with motion amplitude and period set to 2 cm and 5 s. All data was acquired using standard helical/clinical protocol: helical CT follow by PET emission scan. To determine uncertainties in activity measurements in stationary phantom we have acquired PET/CT scans of a phantom at 5 different positions. To evaluated the magnitude of errors in moving phantom we have reconstructed a PET image using emission data for the moving phantom and data for 30 different helical/clinical CT scans of the moving phantom acquired at random. Results: The uncertainties in measuring activities in the stationary phantom ranged from 9% for the largest sphere to 47% for the sphere with smallest diameter. The errors in measuring activity in the sphere in the moving phantom from 30 PET/CT image ranged from 10% to 33 % depending on the sphere's size. We have estimated the maximum possible observable error between the activity in stationary and moving phantom to be 21% for the largest and 75% for the smaller size sphere. Conclusion: The CT acquisition is on an order seconds and is fast enough that it will not acquire a motion‐average CT scan. PET emission scan on the other had is a motion‐average data. As a result, activity measured from PET/CT data acquired with standard helical/clinical protocol will vary depending on a start‐time of the CT acquisition with respect to the phase of the motion cycle.