Abstract:
:We propose a retrospective respiratory gating algorithm to generate dynamic CT studies. To this end, we compared three different methods of extracting the respiratory signal from the projections of small-animal cone-beam computed tomography (CBCT) scanners. Given a set of frames acquired from a certain axial angle, subtraction of their average image from each individual frame produces a set of difference images. Pixels in these images have positive or negative values (according to the respiratory phase) in those areas where there is lung movement. The respiratory signals were extracted by analysing the shape of the histogram of these difference images: we calculated the first four central and non-central moments. However, only odd-order moments produced the desired breathing signal, as the even-order moments lacked information about the phase. Each of these curves was compared to a reference signal recorded by means of a pneumatic pillow. Given the similar correlation coefficients yielded by all of them, we selected the mean to implement our retrospective protocol. Respiratory phase bins were separated, reconstructed independently and included in a dynamic sequence, suitable for cine playback. We validated our method in five adult rat studies by comparing profiles drawn across the diaphragm dome, with and without retrospective respiratory gating. Results showed a sharper transition in the gated reconstruction, with an average slope improvement of 60.7%.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Chavarrías C,Vaquero JJ,Sisniega A,Rodríguez-Ruano A,Soto-Montenegro ML,García-Barreno P,Desco Mdoi
10.1088/0031-9155/53/17/015subject
Has Abstractpub_date
2008-09-07 00:00:00pages
4683-95issue
17eissn
0031-9155issn
1361-6560pii
S0031-9155(08)76372-3journal_volume
53pub_type
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