A custom-built small-animal transceiver was used for in vivo imaging of normal rat brain at 0.35 T, with the objective of identifying anatomic components by comparison of images with corresponding histologic sections. The cerebrum, cerebellum, brain stem, ventricles, hippocampus, and subarachnoid space were identified and cerebrospinal fluid (CSF) was differentiated from gray matter and white matter on coronal and transaxial magnetic resonance (MR) images. These images compare favorably with those obtained by others at higher field strengths in regard to delineating major neuroanatomic structures. It is concluded that this technique will be useful for investigating small-animal models of human neurologic disease involving morphologic and morphometric changes in gray matter, white matter, and CSF-filled spaces.

Animals↗

PubMedDate not supplied

Boronated metalloporphyrins: a novel approach to the diagnosis and treatment of cancer using contrast-enhanced MR imaging and neutron capture therapy.

Porphyrins are a unique class of metal chelating agents that have shown specific affinity for neoplasms. The water-soluble free-base derivative, tetrakiscarborane carboxylate ester of 2,4-(alpha,beta-dihydroxyethyl) deuteroporphyrin IX (BOPP), an agent designed for neutron capture therapy, has previously demonstrated selective localization and retention in a C6 murine glioma. In the present work, the authors demonstrate that the manganese chelate of BOPP also selectively localizes in a rat 9L gliosarcoma and preferentially enhances the tumor-normal brain contrast of T1-weighted images for at least 92 hours. The data indicate a maximal enhancement of contrast between tumor and normal brain at 24 hours after injection, compared with 5 minutes for manganese (III) tetraphenylporphine sulfonate (TPPS4). The results also indicate that Mn-BOPP may have a slower uptake in the 9L glioma than Mn-TPPS4 but a longer retention in the tumor. Mn-BOPP is unique in that it represents, to the authors' knowledge, the first example of a single agent that can enhance contrast between tumor and normal tissue and be potentially effective as an agent for boron neutron capture therapy.

Animals↗

PubMedDate not supplied

Isointense model for the evaluation of tumor-specific MRI contrast agents.

An isointense model has been developed to evaluate the applicability of putative tumor-specific MRI contrast agents. Data for tissue relaxation measurements in the presence of Mn(III)TPPS4 are used to illustrate the model. The concentration of contrast agent in tumor tissue required for a tumor/normal tissue signal difference-to-noise ratio of 5 (delta SNR = 5) is determined for a T1 weighted pulse sequence and several hypothetical tumor/normal tissue pairs. The impact of various contrast agent characteristics including initial tumor/normal tissue relaxation values, differential uptake of contrast agent, and in vivo relaxivity are considered. Isointense tumor/normal tissue with longer initial relaxation times are shown to be more affected by the presence of contrast agent. In addition those with initially longer relaxation times have less rigorous requirements for tumor specificity. Typically, a normal tissue/tumor uptake ratio of 1:2 increases the concentration required for delta SNR = 5 by a factor of two compared to that of exclusive uptake in tumor. For the T1 weighted pulse sequence employed, the concentration required for delta SNR = 5 is shown to be linear with the inverse of in vivo relaxivity for the hypothetical tissues considered. The isointense model is also extended to predict the field dependence of tumor-specific contrast enhancement by Mn(III)TPPS4.

Contrast Media↗