Reconstructed helical CT scans: Improvement in z-axis resolution compared with overlapped and nonoverlapped conventional CT scans

C. J. Kasales, K. D. Hopper, D. N. Ariola, T. R. TenHave, J. W. Meilstrup, R. P M Mahraj, D. Van Hook, S. Westacott, R. J. Sefczek, J. D. Barr

Research output: Contribution to journalArticle

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Abstract

OBJECTIVE. This in vitro study was designed to assess the z-axis resolving capabilities of reconstructed helical CT scans obtained with various imaging parameters versus those of conventional CT scans and the effect of decreasing slice index on the z-axis resolution of helical CT. MATERIALS AND METHODS. A z-axis line-pair phantom was imaged using conventional nonoverlapped CT scans, conventional CT scans that overlapped by 50%, and helical CT scans with pitches of 1.0 and 1.5. All helical images were reconstructed at comparable slice indexes (image indexes of 2.0, 1.0, and 0.5 mm for pitch = 1.0, and image indexes of 3.0, 1.5, and 0.75 mm for pitch = 1.5). Midline coronal and sagittal reconstructed images were obtained to allow standardized visualization of line pairs. The reconstructed images were reviewed separately by 10 radiologists. RESULTS. The overall z-axis resolution of reconstructed helical CT scans equaled or exceeded that of nonoverlapped conventional CT scans in all cases and equaled that of 50% overlapped conventional CT scans in 75% of cases. The 1.0-pitch helical sequences showed improved z-axis resolution with decreasing slice index. No statistically significant improvement in z-axis resolution could be determined by the observers for 1.5-pitch sequences with decreasing slice index. CONCLUSION. The use of helical CT with a pitch of 1.0 or 1.5 and an increased slice index can improve the z-axis resolution of reconstructed images when compared with nonoverlapped conventional CT and frequently equals the resolution of 50% overlapped conventional CT. This improvement in z-axis resolution should improve the appearance of reconstructed images (as used in CT angiography and three-dimensional imaging) by reducing partial volume artifacts while affording faster scanning at a reduced skin-surface radiation dose.

Original languageEnglish (US)
Pages (from-to)1281-1284
Number of pages4
JournalAmerican Journal of Roentgenology
Volume164
Issue number5
DOIs
StatePublished - Jan 1 1995

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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    Kasales, C. J., Hopper, K. D., Ariola, D. N., TenHave, T. R., Meilstrup, J. W., Mahraj, R. P. M., Van Hook, D., Westacott, S., Sefczek, R. J., & Barr, J. D. (1995). Reconstructed helical CT scans: Improvement in z-axis resolution compared with overlapped and nonoverlapped conventional CT scans. American Journal of Roentgenology, 164(5), 1281-1284. https://doi.org/10.2214/ajr.164.5.7717248