Phosphorus liver MRSI at 3 T using a novel dual‐tuned eight‐channel ³¹P/¹H coil

Abstract

Although phosphorus-31 (³¹P) magnetic resonance spectroscopy holds potential as noninvasive tool to monitor treatment response of liver malignancies, the lack of appropriate coils has so far restricted its use to liver lesions close to the surface. A novel eight-channel phased-array dual-tuned ³¹P/¹H coil that can assess ³¹P metabolism in deeper liver tissue as well is presented in this article. Analysis of its performance demonstrates that this coil can provide good sensitivity across a width of 20 cm, thereby enabling magnetic resonance spectroscopic imaging (MRSI) scans that can fully cover axial views of the abdomen in lean subjects. In vivo results and reproducibility of ³¹P MRSI at 3 T of axial slices covering the full depth of the liver are shown in healthy volunteers. To minimize intrasubject and intersubject data variability, spectra are corrected for coil sensitivities. Methods to maximize the reproducibility of coil placement and spectroscopic planning are discussed. The phosphomonoesters/phosphodiesters ratio calculated in healthy volunteers has an average intrasubject variation of 23% averaged over voxels selected from the entire liver. Finally, the feasibility of using the coil in the clinic is shown by preliminary ³¹P liver MRSI data obtained from a patient with hepatocellular carcinoma.

Phosphatidylcholine contributes to in vivo 31P MRS signal from the human liver

“…A coil with optimized geometry [41] in a dedicated experimental set-up should enable coverage of both the larger part of the liver and the gallbladder. The assessment of the absolute concentrations of the PtdC signal at 2.06 ppm PCr=0ppm in our study was hampered by a lack of knowledge of the T 1 relaxation time of PtdC at both field strengths, resulting in unpredictable partial saturation effects.…”

In-vivo 31P-MRS of skeletal muscle and liver: A way for non-invasive assessment of their metabolism

“…To this end, a variety of different strategies (Fig. 6) has been proposed and implemented [22], [37], [218], [219], [220]. These localization techniques are discussed in more detail in the next chapter.…”

“…31 P-MRS is commonly, but not exclusively [22], [124], [246], employed with the use of highly sensitive surface coils. Nevertheless, signal localization by restricted sensitivity volume of these RF-probes does not allow a distinction between the signals that originate from different anatomic and/or morphologic compartments.…”

“…To compensate for the low sensitivity of MR systems to 31 P, surface coils that offer very high sensitivity in their close vicinity are often applied for organ-specific 31 P-MR investigations [17], [18], [19], [20]. These are commonly constructed as simple single loops; however, several complex coil-arrays that provide higher sensitivity and better volume coverage have been introduced recently [21], [22], [23], [24]. While the receive sensitivity of such RF-probes is undoubtedly superior, their transmit efficiency, particularly at ultra-high fields, may be insufficient [23], [25].…”

In vivo sodium MR imaging of the abdomen at 3T

“…Each coil consisted of matching, blocking, and detuning circuits to ensure that the appropriate coils are active and tuned for the specific acquisition. Plugging in this coil disabled the scanner’s body coil so that only the 1 H channel of the dual-tuned coil was used to acquire 1 H images [6]. The inbuilt scanner body coil was not used for transmission purposes.…”