PURPOSE: To determine the distribution of inhalation to exhalation @entity1353 amplitudes as measured using a commercial 4DCT and a proposed 4DCT protocol for irregular @entity1353 @entity1 . METHODS: External @entity1353 surrogate signals correlating with lung tidal volume were collected using an abdominal bellows for a set of 50 @entity1 . Breathing traces over 5-minute durations were evaluated and the peak inhalation and exhalation peaks identified. An arbitrary time point was identified and the nearest exhalation peak located within a   180   gantry rotation period. The times at which the follow-up inhalation scans occurred were correlated with the couch velocity to determine whether the @entity5 would be within 180   of that specific peak inhalation given the CT scanner coverage, pitch, rotation period, @entity5 size, and @entity5 motion amplitude (defined in units of centimeters per bellows signal). The imaged @entity5 motion amplitude was based on which inhalation peak would be imaged and the couch location at that time relative to the exhalation peak. This analysis provided a series of measured @entity1353 motion amplitudes, which were compared against the 85th percentile motion, consistent with the proposed 4DCT protocol. Because the 4DCT scans would yield a single amplitude determination for each @entity1 , errors in the amplitude measurement were considered systematic. Therefore, the largest 5% and smallest 5% of the measured amplitudes were selected to identify over-and under-determined motion amplitudes. RESULTS: 30% of the @entity1 exhibited @entity1353 amplitude overestimations of at least 27%, while 30% showed underestimations of at least 34%. CONCLUSION: For the majority of @entity1 , the current system provided a high probability of correct @entity1353 motion amplitude measurements. 30% had a significant chance of a systematic over- or under-estimation of @entity5 motion. The proposed protocol will be immune to such irregularities because the entire @entity1353 trace is used for @entity1353 motion amplitude assessments.

SU-E-J-25: Analysis of Commercial 4DCT Flaws and the Potential Benefits of a New Technique for Irregular Breathing XXXX .

@entity1 :: ('9606', 'Species') :: ['patients', 'patient'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor'] @entity1353 :: ('MESH:D004417', 'Disease') :: ['breathing']
@entity1 :: (9606,Species) :: ['Patients']
