Effect of gadobutrol on VX2 magnetic resonance diffusion-weighted imaging.

The aim of this study was to evaluate the effect of contrast agent gadobutrol on the magnetic resonance diffusion-weighted imaging (MR DWI). Gadobutrol has higher relaxivity than Gd-DTPA and it also has higher formulation 1.0 M than Gd-DTPA 0.5 M. VX2 tumor implanted on the left thigh of each New Zealand rabbit was used as the animal model. The MR scanning was performed using a 1.5 T clinical whole-body MR scanner with an 8-channel knee coil. The results showed that there were significant differences in the signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) values between tumor and muscle both before and after gadobutrol injection (0.1 mmol/kg). However, there were no significant differences in the SNR and ADC values of tumor or muscle before and after gadobutol administration. There were also no significant difference in the contrast-to-noise ratio (CNR) values of tumor and muscle before and after gadobutrol injection.

The Quantitative Assessment of Gd-DTPA in Contrast Enhanced Magnetic Resonance Angiography.

Recently, the use of MRI contrast agents has been proven to be substantially improved sensitivity and specificity in many clinical applications. CE-MRA has higher blood signal based on the T1 and T2-shortening property of contrast agents, so that even the small vessels can be visualized. The use of contrast agents can improve lesion detection and characterization. The routinely used dose of contrast agents in the routine MRI examinations only relies on the weight of the subject. The purpose of this study is to obtain the clinically optimal dose for 3D-TOF (time-of-flight) pulse sequences for CE-MRA examinations. In the phantom study, ten test tubes were filled with saline mixed with different dose of Gd-DTPA. It is found that the optimal dose of Gd-DTPA for saline phantom by using 3D-TOF pulse sequences is 20 mM. Also, there has no differences of optimal doses between Omniscan and Magnivist contrast agents Gd-DTPA. The results show that consistent high quality CE-MRA images might be obtained by using 0.25M Gd-DTPA (half of the routine dose) with 3~4 cc/sec injection rate for all clinical cases. The benefits of this study might be to minimize dose and potential toxicity. Additionally, the decrease of the cost of contrast agents might be achieved. It is expected to provide the recommended dose of Gd-DTPA for contrast enhanced MRA in clinical routine diagnosis.

Measurement of vascular volume fraction and blood-tissue permeability constants with a pharmacokinetic model: studies in rat muscle tumors with dynamic Gd-DTPA enhanced MRI.

We propose a compartmental model to explain the signal enhancement curves following the bolus injection of Gd-DTPA. The model incorporates vascular volume fraction contribution, and the possibility of having different transport constants between the plasma and extravascular components. A Walker 256 carcinoma grown in rat muscle was used to demonstrate the capability of this model. Several different types of tissues were included in the measurements: normal, quickly enhanced, slowly enhanced, and necrotic tissues. Blood volume and blood-tissue permeability information can be derived from the dynamic contrast-enhanced MRI study employing the proposed model. In the tissue contrast enhancement curve, the initial rising slope after injection is related to the blood volume (or, vascular volume fraction), the maximum enhancement ratio is related to the uptake of tissue, and the decay rate is related to the clearance of tracer from tissue. The measured permeability constant is not the conventional permeability; instead they are contrast agents uptake and clearance rates, which are limited by the blood perfusion. These parameters can be used to characterize different enhancement patterns.