Fast spin-echo studies of contrast and small-lesion definition in a liver-metastasis phantom.

A liver-metastasis model was used to study the ability of fast spin-echo (FSE) imaging to show small lesions (1 pixel in diameter) relative to conventional spin-echo imaging. FSE images of the liver-metastasis phantom were acquired with various phase-encode reordering schemes to manipulate T2 contrast. The imaging time for multisection acquisitions was 27 seconds for FSE imaging and 6 minutes 48 seconds for conventional spin-echo imaging. Computer simulations were performed to determine how the point spread function varies with the different phase-encoding orders in FSE imaging. Contrast-to-noise ratios and signal profiles of the lesions were measured as a function of the effective TE and lesion size. Experimental results and theoretical simulations showed that T2-weighted FSE imaging provides high contrast and good edge definition even for small lesions. The results indicate that FSE imaging may become a powerful method for the early detection of liver metastases.