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Multimodality vascular imaging phantom for calibration purpose

The objective of the project was to design a vascular phantom compatible with X-ray, ultrasound and MRI. Fiducial markers were implanted at precise known locations in the phantom to facilitate identification and orientation of plane views from the 3D reconstructed images. They also allowed optimizing image fusion and calibration. A vascular conduit connected to tubing at the extremities of the phantom ran through an agar-based gel filling it. A vessel wall in latex was included to avoid diffusion of contrast agents. Using a lost-material casting technique based on a low melting point metal, complex realistic geometries of normal and pathological vessels were modeled. The fiducial markers were detectable in all modalities without distortion. No leak of gadolinium through the vascular wall was observed on MRI for 5h of scan. The potential use of the phantom for calibration, rescaling, and fusion of 3D images obtained from the different modalities as well as its use for the evaluation of intra and inter-modality comparative studies of imaging systems were recently demonstrated by our group (results published in SPIE-2003). Endovascular prostheses were also implanted into the lumen of the phantom to evaluate the extent of metallic imaging artifacts (results submitted elsewhere). In conclusion, the phantom can allow accurate calibration of radiological imaging devices and quantitative comparisons of the geometric accuracy of each radiological imaging method tested.