Early GBM Detection by Active-Feedback MRI
Zhao Li, Chao-Hsiung Hsu, Yung-Ya Lin; Department of Chemistry & Biochemistry, UCLA
Early detection of high-grade malignancy, such as glioblastoma multiforme (GBM), using enhanced MR Molecular Imaging techniques significantly increases not only the treatment options available, but also the patients’ survival rate. For this purpose, we have developed a new method, termed “Active-Feedback MR”, to enhance the contrast originated from local magnetic-field gradient variations due to irregular water contents and deoxyhemoglobin concentration in early GBM .
The general principles of the “Active-Feedback Controlled MR” can be found in our publications [2-5]. Here, its specific applications to image deoxyhemoglobin in early GBM were developed and demonstrated. (i) First, an active-feedback electronic device was home-built to generate feedback fields from the received FID current. The device is to filter, phase shift, and amplify the signal from the receiver coils and then retransmit the modified signal into the RF transmission coil, with adjustable and programmable feedback phases and gains. The MR console computer can execute the active-feedback pulse sequences to control the trigger signal, feedback phase/gain, and the duration of the feedback fields, allowing us to utilize the active feedback fields in novel ways. (ii) Next, an active-feedback pulse sequence was developed for early GBM detection and was statistically tested on in vivo orthotopic GBM mice models to enhance the contrast originated from local magnetic-field gradient variations due to irregular water contents and deoxyhemoglobin concentration in early GBM .
Stage-1 orthotopic GBM mouse models infected with human U87MG cell line were imaged. Representative results from 5 mice were shown in Fig. 2. While T2 parameter images (3rd column), T2-weighted images (4th column), and T1-Gd-weighted images (5th column) could not successfully locate the early GBM tumor, our active-feedback fixed-point images (2nd column) and decay constant mapping (1st column) successfully highlight the early GBM tumor with a close correlation with histopathology (6th column). Statistical results (N>10) show that this new approach provides 5-6 times of improvements in GBM tumor contrast, as measured by “contrast-to-noise ratio” (CNR) or “Visibility”.
In vivo orthotopic xenografts GBM mouse models validated the superior contrast/sensitivity and robustness of this approach towards early GBM detection. Statistical results (N>10) for GBM mouse models at various cancer stages, alternative active feedback pulse sequences with further improved performance will also be presented.
 Magn. Reson. Med. (in press)  Science 290, 118 (2001)  Magn. Reson. Med. 56, 776 (2006)  Magn. Reson. Med. 61, 925 (2009)  J. Phys. Chem. B 110, 22071 (2006)
Format: Oral communication