Dynamic contrast-enhanced MR imaging of VX2 carcinomas after X-irradiation in rabbits: comparison of gadopentetate dimeglumine and a macromolecular contrast agent.

Rationale and Objectives: To compare enhancement patterns of gadomer-17 with those of gadopentetate dimeglumine in VX2 carcinomas after irradiation on rabbits.
Methods: Twelve rabbits with VX2 carcinoma in the thigh underwent dynamic contrast-enhanced magnetic resonance (MR) imaging with gadopentetate dimeglumine and gadomer-17 at 24-hour intervals before (n = 12), 3 days (group 1, n = 12), 1 month (group 2, n = 8) and 2 months (group 3, n = 4) after 30 Gy irradiation. After taking postirradiation MR images, 4 rabbits were killed for histopathologic examination at each time interval. The enhancement characteristics in MR imaging and morphology of tumor vessels in histopathologic specimen were assessed.
Results: After gadopentetate dimeglumine injection, the enhancement characteristics were not different among tumors before and after irradiation (P > 0.05). For gadomer-17, the enhancement ratios decreased after irradiation. The shape of the curves for tumor enhancement before irradiation was significantly different from curves of group 1(P < 0.05). The specimens from group 3 showed sclerosis and wall thickening in arterioles.
Conclusions: Dynamic contrast-enhanced MR imaging with a gadomer-17 reveals increased capillary permeability at an early phase after irradiation and chronic obliterating vasculopathy at delayed phase.