[67Ga SPECT in the evaluation of orbital and ocular mass-like lesions]

We evaluated 67Ga SPECT in the differentiation of mass-like lesions in the orbital and ocular areas. A two-headed SPECT system equipped with parallel-hole collimator was used. 67Ga SPECT demonstrated three dimensionally the extent of tumors found by CT and MRI. 67Ga SPECT was especially useful in the assessment of localized lesions in and around the lacrimal gland. In a total of 43 patients studied, the overall accuracy of 67Ga SPECT in diagnosing orbital and ocular lesions was 72%. Sixteen of 21 malignant lesions (76%) showed true positive findings and 15 of 22 benign lesions (68%) showed true negative findings. All seven malignant lymphoma lesions showed true positive findings. One of four cases of malignant melanoma was not visualized. This lesion was less than 15 mm in diameter. None of the three cases of retinoblastoma was visualized, regardless of tumor size. Four of seven cases of pseudotumor or pseudolymphoma showed false positive findings. The differentiation of pseudotumor and pseudolymphoma from malignant lymphoma seemed to be difficult. We conclude that 67Ga SPECT is useful in the differentiation of lesions in the orbital and ocular areas and that evaluation of the extent of malignant lesions can be improved by comparing the findings obtained by morphological diagnostic modalities.