manganese(iii)tetraphenylporphine-sulfonate and Brain-Edema

The in vivo relaxation times T1 and T2 were quantitatively determined in rat brain. Animals with implanted experimental brain tumors were investigated for discrimination of pathological regions from normal brain structures based on relaxation time differences. The different cerebral tumors (glioma, schwannoma, neuroblastoma) showed no difference in relaxation times, but all tumors had T1(1301 +/- 167 ms) and T2(91 +/- 9 ms) times distinctly longer than normal brain (T1: 1057 +/- 77 ms; T2: 77 +/- 6 ms). T1 can be used for distinction of tumor and edema from normal brain, while T2 is the better parameter for discrimination between tumor and edema. Furthermore, the effect of MRI contrast agents (GdDTPA, MnTPPS, GdTPPS) on the relaxation times of these experimental brain tumors was measured. The enhancement of tumors produced by GdDTPA disappeared within ten minutes after i.p. application. At later times, central cysts and peritumoral edema became the most enhanced structures. The enhancement of tumor following MnTPPS application remained unchanged in T1-weighted images during the whole observation period of four days. A significant reduction of enhancement was not observed during this time. The effect of MnTPPS on T2 was weak. Replacement of manganese with gadolinium as the central ion of the porphyrin TPPS led to a contrast agent with enhancement effects on both, T1- and T2-weighted images.

Topics: Analysis of Variance; Animals; Brain Edema; Brain Neoplasms; Contrast Media; Diagnosis, Differential; Gadolinium; Gadolinium DTPA; Glioma; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Manganese; Metalloporphyrins; Neurilemmoma; Neuroblastoma; Organometallic Compounds; Pentetic Acid; Rats; Rats, Inbred F344; Tumor Cells, Cultured

The ultrafast inversion recovery snapshot FLASH technique was used to determine the kinetics of the contrast agent manganese (III) tetraphenylporphine sulfonate (MnTPPS) in experimental brain tumors in rats. In the first part of the investigation this technique was validated with the conventional inversion recovery spin-echo method by comparing in vivo T1 data of a normal rat brain. Agreement between T1 values obtained from both techniques was complete, as tested for a large number of pixels in identical coronal slices. In the second part the fast IR snapshot FLASH method was applied to study the effect of the NMR contrast agent MnTPPS on the T1 relaxation time of experimental gliomas in rat brains. T1 of normal brain tissue (1024-1035 ms), tumor (1217 ms), and edema (1199 ms) was determined with the inversion recovery version of the snapshot FLASH imaging technique. After intraperitoneal injection of MnTPPS (0.25 mmol/kg body wt) T1 decreased exponentially to 56% of control in tumor and to 62% in muscle. In normal and edematous brain tissue no significant changes in T1 were observed up to 5 h after injection of the contrast agent. Once the T1 contrast between tumor and peritumoral brain tissue had reached a saturation, the enhancement persisted for several hours to days. Therefore application of this contrast agent resulted in a sharp demarcation between glioma and peri-tumoral edema.

Topics: Animals; Brain; Brain Edema; Brain Neoplasms; Contrast Media; Glioma; Half-Life; Injections, Intraperitoneal; Magnetic Resonance Imaging; Male; Manganese; Metalloporphyrins; Models, Structural; Neck Muscles; Rats; Rats, Inbred F344; Temporal Muscle; Time Factors