RT Journal Article SR Electronic T1 In Vivo Assay of Folate Receptors in Nonfunctional Pituitary Adenomas with 99mTc-Folate SPECT/CT JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1716 OP 1723 DO 10.2967/jnumed.108.061689 VO 51 IS 11 A1 James R. Galt A1 Raghuveer K. Halkar A1 Chheng-Orn Evans A1 Naema A. Osman A1 David LaBorde A1 Timothy H. Fox A1 Bajat A. Faraj A1 Kush Kumar A1 Houping Wang A1 Nelson M. Oyesiku YR 2010 UL http://jnm.snmjournals.org/content/51/11/1716.abstract AB The objective of this study was to evaluate the in vivo assay of folate receptors in nonfunctional pituitary adenomas using preoperative 99mTc-folate SPECT/CT and Western blot analysis (WBA) of surgical specimens as the standard. Methods: Fifty-six patients (29 men, 27 women; age range, 29–82 y) with clinically nonfunctional pituitary adenomas on MRI underwent preoperative imaging using 666 MBq (18 mCi) of 99mTc-folate. SPECT/CT images and whole-body and lateral head planar images were acquired approximately 2 h after injection. Surgical resection took place within a week. WBA on a portion of the excised specimens assessed folate receptor expression in 49 patients. Attenuation-corrected 99mTc-folate SPECT/CT images were assessed qualitatively and quantitatively (maximal adenoma counts to background), with WBA as a standard. Results: Integrated CT was useful for uptake localization and assisted region-of-interest placement. Qualitative interpretation of planar imaging yielded a sensitivity of 81% and specificity of 72%. Qualitative SPECT/CT yielded a sensitivity of 94% and specificity of 61%. Receiver-operating-characteristic curve analysis of quantitative uptake yielded a tumor-to-background cutoff ratio of 3.5, with a sensitivity of 81% and specificity of 83%. Scalp uptake yielded consistent results (over the brain, neck, and choroid plexus) for background when SPECT/CT misalignment artifacts were avoided. Detection of pituitary uptake on anterior–posterior and lateral images was hampered by facial uptake, which varied between patients. Conclusion: SPECT/CT of 99mTc-folate is an accurate method of assaying folate receptors in vivo and may provide a quantitative marker for identifying folate receptor–positive tumors. This method may also prove beneficial in selecting patients for folate-targeted therapy of clinically nonfunctional pituitary adenomas, for which there is currently no medical therapy.