Document Detail

Evaluation of z-axis resolution and image noise for nonconstant velocity spiral CT data reconstructed using a weighted 3D filtered backprojection (WFBP) reconstruction algorithm.
MedLine Citation:
PMID:  20229899     Owner:  NLM     Status:  MEDLINE    
PURPOSE: To determine the constancy of z-axis spatial resolution, CT number, image noise, and the potential for image artifacts for nonconstant velocity spiral CT data reconstructed using a flexibly weighted 3D filtered backprojection (WFBP) reconstruction algorithm. METHODS: A WFBP reconstruction algorithm was used to reconstruct stationary (axial, pitch=0), constant velocity spiral (pitch = 0.35-1.5) and nonconstant velocity spiral CT data acquired using a 128 x 0.6 mm acquisition mode (38.4 mm total detector length, z-flying focal spot technique), and a gantry rotation time of 0.30 s. Nonconstant velocity scans used the system's periodic spiral mode, where the table moved in and out of the gantry in a cyclical manner. For all scan types, the volume CTDI was 10 mGy. Measurements of CT number, image noise, and the slice sensitivity profile were made for all scan types as a function of the nominal slice width, table velocity, and position within the scan field of view. A thorax phantom was scanned using all modes and reconstructed transverse and coronal plane images were compared. RESULTS: Negligible differences in slice thickness, CT number, noise, or artifacts were found between scan modes for data taken at two positions within the scan field of view. For nominal slices of 1.0-3.0 mm, FWHM values of the slice sensitivity profiles were essentially independent of the scan type. For periodic spiral scans, FWHM values measured at the center of the scan range were indistinguishable from those taken 5 mm from one end of the scan range. All CT numbers were within +/- 5 HU, and CT number and noise values were similar for all scan modes assessed. A slight increase in noise and artifact level was observed 5 mm from the start of the scan on the first pass of the periodic spiral. On subsequent passes, noise and artifact level in the transverse and coronal plane images were the same for all scan modes. CONCLUSIONS: Nonconstant velocity periodic spiral scans can achieve z-axis spatial resolution, CT number accuracy, image noise and artifact level equivalent to those for stationary (axial), and constant velocity spiral scans. Thus, periodic spiral scans are expected to allow assessment of four-dimensional CT data for scan lengths greater than the detector width without sacrificing image quality.
Jodie A Christner; Karl Stierstorfer; Andrew N Primak; Christian D Eusemann; Thomas G Flohr; Cynthia H McCollough
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medical physics     Volume:  37     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:  2010 Feb 
Date Detail:
Created Date:  2010-03-16     Completed Date:  2010-04-09     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  897-906     Citation Subset:  IM    
Mayo Clinic Rochester, 200 First Street SW, Rochester, Minnesota 55905, USA.
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MeSH Terms
Imaging, Three-Dimensional / methods*
Phantoms, Imaging
Radiographic Image Enhancement / methods
Radiographic Image Interpretation, Computer-Assisted / methods*
Reproducibility of Results
Sensitivity and Specificity
Tomography, Spiral Computed / methods*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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