Inherently decoupled1H antennas and31P loops for metabolic imaging of liver metastasis at 7 T. (10th January 2020)

• Record Type: Journal Article
• Authors: Rivera, Debra; Kalleveen, Irene; de Castro, Catalina Arteaga; van Laarhoven, Hanneke; Klomp, Dennis; van der Kemp, Wybe; Stoker, Jaap; Nederveen, Aart
• Is Part Of: NMR in biomedicine. Volume 33:Number 4(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-01-10
• Subjects: cancer, liver, metastatic, phosphorus, 7 T, spectroscopy, ultra high field; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.4221
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract: High field 31 P spectroscopy has thus far been limited to diffuse liver disease. Unlike lower field‐strength scanners, there is no body coil in the bore of the 7 T and despite inadequate penetration depth (<10 cm), surface coils are the current state‐of‐the‐art for acquiring anatomical images to support multinuclear studies. We present a system of proton antennas and phosphorus loops for 31 P spectroscopy and provide the first ultrahigh‐field phosphorus metabolic imaging of a tumor in the abdomen. Herein we characterize the degree to which antennas are isolated from underlying loops. Next, we evaluate the penetration depth of the two antennas available during multinuclear examinations. Finally, we combine phosphorus spectroscopy (two loops) with parallel transmit imaging (eight antennas) in a patient. The loops and antennas are inherently decoupled (no added circuitry, <0.1% power coupling). The penetration depth of two antennas gives twice that of conventional loops. The liver and full axial slice of the abdomen were imaged with eight transmit/receive antennas using parallel transmit B1‐shimming to overcome image voids. Phosphorus spectroscopy from a liver metastasis resolved individual peaks for phosphocholine and phosphoethenalomine. Proton antennas are inherently decoupled from phosphorus loops. By using two proton antennas it is possible to perform region‐of‐interest image‐based shimming in over 80% of the liver volume, thereby enabling phosphorus spectroscopy of localized disease. Shimming of the full extent of the abdominal cross‐section is feasible using a parallel transmit array of eight antennas. A system architecture capable of supporting eight‐channel parallel transmit and multinuclear spectroscopy is optimal for supporting multiparametric body imaging, including metabolic imaging, for monitoring the response of patients with liver metastases to cancer treatments and for patient risk stratification. In the meantime, the existing infrastructure using two antennas is sufficient for preliminary studies in metabolic imaging of tumors in the liver. Abstract : Due to the difficulty of obtaining sufficient coverage of liverin localizer images, ultra‐high‐field phosphorus spectroscopy of liver has beenlimited to diffuse disease. To overcome the challenge for abdomen and thoraxcancers, we combine antennas and parallel transmit for proton imaging withinherently decoupled loops below the antennas for phosphorus spectroscopy. Toour knowledge, we present the first phosphorus spectra of a patient with ametastatic tumor in the liver, differentiating phosphoethanolamine (PE) andphosphocholine (PC) in vivo.