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[MR-based volumetric analysis of small tumor volumes: accuracy of phantom examinations of simulated eye tumors].

PURPOSE
The determination of tumor volume in ocular tumors is very important for the planning and success of radiation therapy. This study uses an animal model to evaluate the accuracy of MR-based volumetry of ocular tumors.


MATERIALS AND METHODS
In a total of 25 porcine eyes obtained from the slaughterhouse, ocular tumors were produced by injecting a mixture of hand creme and Gd-DTPA under ophthalmoscopic guidance. The injected volume varied between 0.05 ml and 2.7 ml. The eyes were examined with a 1.5 Tesla scanner and a 4 cm circular surface coil especially developed for ocular MRI. After data transfer to a separate workstation, volumetric analysis was carried out by three independent radiologists using semiautomated software. The determined volume was compared with the injected volume.


RESULTS
Of the 25 prepared porcine eyes, 23 were suitable for volumetric analysis. The injection of the mixture of hand creme and Gd-DTPA produced two different types of tumors. Ophthalmoscopically, 14 ellipsoid and 9 lobulated to mushroom-shaped tumors were found and confirmed by MRI. Minor deviation was found between injected volume and volume calculated by MRI, with a correlation coefficient of 0.96.


CONCLUSION
Using appropriate technique, MRI is capable of determining small tumor volumes with high accuracy in an animal model. Minor differences can be expected when transferring the results to clinical studies.