Are TrueFISP images T2/T1‐weighted? |
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Authors: | Teng-Yi Huang Ing-Jye Huang Cheng-Yu Chen Klaus Scheffler Hsiao-Wen Chung Hui-Cheng Cheng |
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Affiliation: | Department of Electrical Engineering, National Taiwan University, Taipei, ROC. |
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Abstract: | Images acquired using the TrueFISP technique (true fast imaging with steady-state precession) are generally believed to exhibit T(2)/T(1)-weighting. In this study, it is demonstrated that with the widely used half-flip-angle preparation scheme, approaching the steady state requires a time length comparable to the scan time such that the transient-state response may dominate the TrueFISP image contrast. Two-dimensional images of the human brain were obtained using various phase-encoding matrices to investigate the transient-state signal behavior. Contrast between gray and white matter was found to change significantly from proton-density- to T(2)/T(1)-weighted as the phase-encoding matrix size increased, which was in good agreement with theoretical predictions. It is concluded that TrueFISP images in general exhibit T(2)/T(1)-contrast, but should be more appropriately regarded as exhibiting a transient-state combination of proton-density and T(2)/T(1) contrast under particular imaging conditions. Interpretation of tissue characteristics from TrueFISP images in clinical practice thus needs to be exercised with caution. |
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Keywords: | TrueFISP steady‐state free precession transient state gray/white matter contrast |
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