| Abstrakt: |
Purpose: Deuterium metabolic imaging (DMI) maps the uptake of deuterated precursors and their conversion into lactate and other markers of tumor metabolism. Even after leveraging 2H's short T1s, DMI's signal‐to‐noise ratio (SNR) is limited. We hypothesize that a multi‐echo balanced steady‐state free precession (ME‐bSSFP) approach would increase SNR compared to chemical shift imaging (CSI), while achieving spectral isolation of the metabolic precursors and products. Methods: Suitably tuned 2H ME‐bSSFP (five echo times [TEs], ΔTE = 2.2 ms, repetition time [TR]/flip‐angle = 12 ms/60°) was implemented at 15.2T and compared to CSI (TR/flip‐angle = 95 ms/90°) regarding SNR and spectral isolation, in simulations, in deuterated phantoms and for the in vivo diagnosis of a mouse tumor model of pancreatic adenocarcinoma (N = 10). Results: Simulations predicted an SNR increase vs. CSI of 3‐5, and that the peaks of 2H‐water, 2H6,6'‐glucose, and 2H3,3'‐lactate can be well isolated by ME‐bSSFP; phantoms confirmed this. In vivo, at equal spatial resolution (1.25 × 1.25 mm2) and scan time (10 min), 2H6,6'‐glucose's and 2H3,3'‐lactate's SNR were indeed higher for bSSFP than for CSI, three‐fold for glucose (57 ± 30 vs. 19 ± 11, P <.001), doubled for water (13 ± 5 vs. 7 ± 3, P =.005). The time courses and overall localization of all metabolites agreed well, comparing CSI against ME‐bSSFP. However, a clearer localization of glucose in kidneys and bladder, the detection of glucose‐avid rims in certain tumors, and a heterogeneous pattern of intra‐tumor lactate production could only be observed using ME‐bSSFP's higher resolution. Conclusions: ME‐bSSFP provides greater SNR per unit time than CSI, providing for higher spatial resolution mapping of glucose uptake and lactate production in tumors. [ABSTRACT FROM AUTHOR] |
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