A modified protocol using half-dose gadolinium in dynamic 3-Tesla magnetic resonance imaging for detection of ACTH-secreting pituitary tumors Lesly Portocarrero-Ortiz • Dulce Bonifacio-Delgadillo • Arturo Sotomayor-Gonza ´lez • Arturo Garcia-Marquez • Raul Lopez-Serna Published online: 25 February 2010 Ó Springer Science+Business Media, LLC 2010 Abstract ACTH-secreting tumors represent 10% of functioning pituitary adenomas, and most of them are microadenomas. It is generally accepted that only half of these tumors are correctly identified with current magnetic resonance imaging (MRI) techniques. The objective of the paper is to report a method for detecting suspected ACTH- secreting pituitary tumors undetectable by conventional dynamic MRI using dynamic 3-Tesla MRI (3T MRI) and half-dose gadopentetate dimeglumine (0.05 mmol/Kg). Eight patients were included (5 men and 3 women) with a mean age of 29.12 years. Each of them had a confirmed diagnosis of Cushing disease and a negative dynamic MRI for microadenoma using full-dose gadopentetate dimeglu- mine. A second MRI was then performed using only half the usual dose of contrast material. Images from the second MRI where compared with the first study. Microadenomas were detected in 100% of the patients using a half dose of the contrast. All were recognized on the basis of the presence of a hypointense nodular lesion surrounded by normal contrast-enhanced tissue. Six patients were sub- mitted to surgery, and the results were confirmed by immunohistochemistry in all of them. The remaining sub- ject had a sinus sample catheterization coincident with the MRI results. Conclusion: A half dose of dynamic reso- nance imaging contrast material increases the sensitivity of MRI detection of ACTH-secreting pituitary tumors. Keywords ACTH pituitary tumors Á Half-dose gadolinium Á Dynamic MRI Introduction ACTH-secreting tumors constitute 10% of functioning pituitary adenomas [1, 2], and most of them are microad- enomas that are only clinically evident by their abnormal hormonal production [3]. The sensitivity of magnetic res- onance imaging (MRI) for microadenoma detection is over 85% with conventional techniques [4–6]. Dynamic MRI improves the sensitivity by 5–10% [7]. However, micro- adenoma detection is not always possible by this method due to strong generalized glandular enhancement after contrast material administration, which makes it difficult to differentiate microadenomas from normal glandular tissue [8]. ACTH-secreting tumor identification is even more difficult due to their localization and size (frequently ventrally located, and almost 50% of ACTH-secreting tumors measure less than 5 mm) [9]. Although the sensi- tivity of MRI for ACTH-secreting tumors varies widely among different authors, it is generally accepted that these tumors are correctly identified only half of the time [9, 10]. Traditional protocols for dynamic MRI consist of five sets of images obtained after the administration of gadopente- tate dimeglumine at a dose of 0.1 mmol/Kg [11]. We propose using half-dose gadopentetate dimeglumine (0.05 mmol/Kg) for dynamic 3-Tesla MRI (3T MRI) when L. Portocarrero-Ortiz (&) Department of Endocrinology, Instituto Nacional de Neurologia y Neurocirugia ‘‘Manuel Velasco Suarez’’, Insurgentes Sur 3877 Col. La Fama, Mexico City 14269, Mexico e-mail: lesly.portocarrero@gmail.com D. Bonifacio-Delgadillo Á A. Garcia-Marquez Department of Neuroradiology, Instituto Nacional de Neurologia y Neurocirugia ‘‘Manuel Velasco Suarez’’, Insurgentes Sur 3877 Col. La Fama, Mexico City 14269, Mexico A. Sotomayor-Gonza ´lez Á R. Lopez-Serna Department of Neurosurgery, Instituto Nacional de Neurologia y Neurocirugia ‘‘Manuel Velasco Suarez’’, Insurgentes Sur 3877 Col. La Fama, Mexico City 14269, Mexico 123 Pituitary (2010) 13:230–235 DOI 10.1007/s11102-010-0222-y