DIFFERENTIATION OF SPONTANEOUS CANINE BREAST-TUMORS USING DYNAMIC MAGNETIC-RESONANCE-IMAGING WITH 24-GADOLINIUM-DTPA-CASCADE-POLYMER, A NEWBLOOD-POOL AGENT - PRELIMINARY EXPERIENCE

RATIONALE AND OBJECTIVES. The authors assess the enhancement character istics over time of spontaneous breast tumors in dogs comparing gadope ntetate dimeglumine with a new blood-pool agent (24-gadolinium [Gd]-DT PA-cascade-polymer). METHODS. Eighteen dogs with spontaneous breast tu mors (5 carcinomas, 4 adenomas, and 9 benign mixed-tissue tumors) unde rwent dynamic magnetic resonance imaging after intravenous injection o f gadopentetate dimeglumine and the blood-pool agent. Signal intensity time curves were followed up to 30 minutes after injection of both ag ents in the same animal. A nonlinear fitting routine enabled calculati on of the delivery and clearance half lives of the contrast agent kine tics in each tumor. RESULTS. For gadopentetate dimeglumine, a fast sig nal increase was found immediately after intravenous injection, with a subsequent signal decay in all tumors. No difference was observed bet ween the enhancement kinetics of different tumor types after gadopente tate dimeglumine application. Similar kinetics were found in benign le sions after injection of the blood-pool agent. However, in carcinomas the blood-pool agent displayed a slower delivery, delayed peak enhance ment, and slower tumor tissue clearance or even a signal plateau of mo re than 30 minutes. CONCLUSIONS. Dynamic magnetic resonance imaging of breast neoplasms using a blood-pool agent may help to better differen tiate between benign and malignant lesions because it demonstrates the enlarged interstitial space and increased capillary permeability in c arcinomas.