Optimized 1H MRS and MRSI methods for the in vivo detection of boronophenylalanine.

Boronophenylalanine (BPA) is used as Boron-10 carrier in boron neutron capture therapy, an experimental cancer radiotherapy. Results of quantitative, noninvasive in vivo detection and imaging of BPA in laboratory animals using (1)H NMR are presented for the first time. The purpose of this study was to implement and validate optimized techniques for the efficient detection of BPA. The (1)H NMR signals through which BPA is most readily detected in vivo are those from the aromatic ring of the molecule, which are part of a scalar-coupled spin system. The preferred detection method should therefore be based on a pulse sequence in which the effective TE is as short as possible. Modified versions of LASER (tau(CP) = 4.6 ms, TE = 27.6 ms) and double-echo slice-selective 2D MRSI (TE = 12 ms) were implemented for single-voxel spectroscopy and spectroscopic imaging of BPA, respectively. Chemical shift selective excitation was used for both sequences, based on a pulse that enabled narrow-band excitation without concomitant delay in TE. SI data without water suppression was used for absolute quantitation and for correction of B(0) variations. Experiments were conducted at 4.7 T in phantoms and in mice where the infused BPA was detected in the kidney.