How to Improve the Conspicuity of Breast Tumors on Computed High b-value Diffusion-weighted Imaging
Magnetic Resonance in Medical Sciences
Purpose: The aim of this study was to compare the tumor conspicuity on actual measured diffusion-weighted images (aDWIs) and computed DWI (cDWI) of human breast tumors and to examine, by use of a phantom, whether cDWI improves their conspicuity. Materials and Methods: We acquired DWIs (b-value 0, 700, 1400, 2100, 2800, and 3500 s/mm 2 ) of 148 women with breast tumors. cDWIs with b-values of 1400, 2100, 2800, and 3500 s/mm 2 were calculated from aDWI scans where b = 0 and 700 s/mm 2 ; the tumor
... signal-to-noise ratio (SNR) was compared at each b-value. We also subjected a phantom harboring a breast tumor and mammary glands to DWI. For reference we used two models. The model with b = 0, 1000, 1500, 2000, 2500, and 3000 s/mm 2 was our multiple b-value model. In the single b-value model, we applied b = 0 and 1000 s/mm 2 and changed the number of excitations (NEX). cDWIs were generated at b = 0 and 1000 and used to compare the SNR, the contrast ratio (CR), and the contrast-to-noise ratio (CNR). Results: In the phantom study, the CNR of cDWI generated from high SNR images obtained at lower b-values and a high NEX was outperformed aDWI. However, the CR and CNR on cDWI obtained using the same scanning parameters were inferior to aDWI scans. Similarly, in the clinical study, breast tumor conspicuity was worse on high b-value cDWIs than aDWIs. Conclusion: To improve tumor conspicuity on cDWI, the quality of the source images must be improved. It may easily cause inferior conspicuity to aDWIs if high b-value cDWIs were generated from insufficient SNR images.