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Evaluation of ocular tumors with technetium-99m-MIBI: planar pinhole technique or SPECT?
1Nuclear Medicine Center of the Clinical Hospital and School of Medical Technology, University of Uruguay, Montevideo. oalonso@hc.edu.uy
Objective:
This study compares 2 imaging protocols, planar pinhole technique (PPHT) and SPECT, for evaluating ocular masses with 99mTc-MIBI.
Methods:
Sixteen patients with ocular lesions were studied. Planar images were acquired 10 min after the injection of 740 MBq 99mTc-MIBI with an LFOV camera fitted with a pinhole collimator (5.0 mm). A SPECT study was performed immediately after the planar study, using a 360 degrees orbit, 64 steps, 20 s/stop, a 128 x 128 matrix, and a low-energy high-resolution (LEHR) collimator. Twelve lesions (9.5-18.0 mm) proved to be malignant: 8 primary tumors (ocular melanoma); 3 local relapses of different tumors of the conjunctiva; and 1 ocular metastasis from breast cancer. The remaining 4 lesions (10.0-16.0 mm) were benign: 1 inflammatory lesion; 1 benign intraocular calcification; and 2 naevi.
Results:
SPECT images showed 11 of 12 malignant lesions (91.6%), whereas the planar technique demonstrated only 4 of the 12 lesions (33.3%). One false-positive result, the inflammatory lesion, was visualized by both techniques. The remaining benign lesions were not detected with either method.
Conclusion:
Technetium-99m-MIBI SPECT is a sensitive technique for detecting malignant ocular tumors. SPECT imaging is a better alternative to planar imaging for ocular tumors.