Establishment of a swine model for validation of perfusion measurement by dynamic contrast-enhanced magnetic resonance imaging

Abstract

The aim of the study was to develop a suitable animal model for validating dynamic contrast-enhanced magnetic resonance imaging perfusion measurements. A total of 8 pigs were investigated by DCE-MRI. Perfusion was determined on the hind leg musculature. An ultrasound flow probe placed around the femoral artery provided flow measurements independent of MRI and served as the standard of reference. Images were acquired on a 1.5 T MRI scanner using a 3D T1-weighted gradient-echo sequence. An arterial catheter for local injection was implanted in the femoral artery. Continuous injection of adenosine for vasodilation resulted in steady blood flow levels up to four times the baseline level. In this way, three different stable perfusion levels were induced and measured. A central venous catheter was used for injection of two different types of contrast media. A low-molecular weight contrast medium and a blood pool contrast medium were used. A total of 6 perfusion measurements were performed with a time interval of about 20-25 min without significant differences in the arterial input functions. In conclusion the accuracy of DCE-MRI-based perfusion measurement can be validated by comparison of the integrated perfusion signal of the hind leg musculature with the blood flow values measured with the ultrasound flow probe around the femoral artery.

Figure 1

Positions of the ultrasound flow probe and catheter at the femoral artery. The arrows indicate the direction of blood flow.

Figure 2

Difference image. T1-weighted images before and after local injection of contrast agent into the right femoral artery were acquired. There is significant brightening of the supply area.

Figure 3

Photograph showing the supply area of the femoral artery after administration of Evans blue via the Seldinger catheter.

Figure 4

Representative example of workflow and timing in a single swine experiment.

Figure 5

Increase in blood flow (mL/min) after local administration of adenosine in experiment number 5 (a). Distribution of adenosine doses (μg/kg/min) with the corresponding blood flow levels (mL/min) in the first 7 experiments. The adenosine dose was set individually for each pig to achieve certain blood flows (b). Distribution of adenosine doses (μg/kg/min) with the corresponding changes in blood flow [%] in the first 7 experiments. The increase in blood flow is given relativly to the baseline blood flow of each pig (c).

Figure 6

Signal curves of arterial input functions (AIF) of the aorta. The figure shows curves of three measurements after administration of the BPCM. The curves of the second and third measurements have a higher baseline signal than the first curve because of persisting effects of CM administered for the preceding measurement (a). Relaxation rate change versus time of the arterial blood measured in the aorta. The relaxation rate change curves were calculated with the method of Li et al. using the same data as for (a). The CM preload has no evident effect on the curves (b). Signal tissue curves of semitendinosus muscle using LMCM. As far as possible, no bones, skin, or great vessels were included (c). Corresponding to the method used in (c), relaxation rate change versus time curves were generated (d). Relaxation rate change versus time of the AIF of a 17-year-old female sarcoma patient measured in a vessel in the lower extremity using a BPCM (e). Relaxation rate change versus time of a tissue curve measured in a muscle of the lower extremity of the sarcoma patient using an LMCM (f).