BackTrack: Dynamic MR Imaging of the Pituitary: Same tools, different technique (but wow, what a difference!)

(This article was first posted on July 29, 2008. It's worth repeating.)

Those of us who have suffered or still suffer with pituitary adenomas have heard way too many times "your MRI is normal". I did, for years. Yet, I ultimately did have a proven adenoma which caused my Cushing's disease. If the MRI had shown even an inkling of the tumor to the trained eye, perhaps a doctor would have taken my symptoms more seriously.

So, what makes a difference, then?

Two things made a huge difference for me. First, my current endocrinologist insisted on a dynamic MRI. Secondly, I sent the films and/or CDs to neurosurgeons who remove a lot of pituitary adenomas. What my local radiologist called a "normal" MR image of my pituitary was actually deemed NOT NORMAL by three world-renowned neurosurgeons.

(My local hospital is excellent, but they had never done a dynamic protocol with MR imaging. However, the Taper Imaging Center at Cedars-Sinaii Hospital in Los Angeles bent over backwards to prepare them through phone calls, emails, and reading materials. What a good group of folks! I've met several of them.)

What is a dynamic MRI?

In order to understand that, you need to first understand what an MRI is. Typically, pituitary MRI's are done "without contrast" and "with contrast". The Magnetic Resonance Imaging is done with no radioactivity (aka x-rays). It uses a strong magnetic field produced by a large magnet to send radio waves through the body which "jiggle" the body's atoms. When these atoms move back into place, they send out radio waves of their own which are picked up by the scanner and fed into a computer. This computer then uses programmed algorithms to turn them into pictures. To learn more about it, visit How Stuff Works.

A contrast is often used with MR imaging, especially of the head, to enhance the images. Solutions of gadolinium compounds are typically used as contrast agents. Tumors enhance after gadolinium is given because they tend to absorb the contrast agent either more quickly or less quickly than "normal" tissue. This leads to a "contrast" between the two types of tissue.

What makes a dynamic MRI different from any MRI using contrast?

Typically, a series of images are taken prior to contrast and then the MR imaging is stopped while contrast is injected. Once that is finished, the MRI proceeds with another series of images. With the dynamic protocol, the contrast is infused over a period of time while the MR imaging is taking place. In one study the gadolinium solution was injected via IV over a period of 180 seconds. In another study the gadolinium was dripped via IV between 2 and 3 minutes.

Why does that make a difference?

Pituitary tumors and normal gland tissue absorb the gadolinium at different speeds. The contrast between the normal tissue and tumor may be easier to see in the earlier images when compared to the later ones. Usually the pituitary adenoma enhances slower than the gland. (However, there have been documented cases of just the reverse if the tumor encases a blood supply.) When the tumor enhances slower, a "dark spot", in layman terms, shows up on the pituitary. These are called areas of "hypointensity". This is transitory and if not imaged as it happens, the tumor will enhance to match the gland. (In the picture, the upper image does not clearly show a tumor. The lower image shows the tumor well including its contact with the right internal carotid artery.)

Although I did not mention the strength of the MRI scanners being used, it's probably obvious that the stronger they are (measured in Tesla), the better they work. A 3T scanner is preferable if available, but the authors of the studies used scanners as low as 0.5T in their studies. A scanner is only as good as those operating it, those reading the scans, and the protocols used not matter how strong it is.

Pretty dynamic, huh?

---

For more information in prior threads, see:

Recent Advances in Neuroendocrine Imaging Lead to Improved Diagnosis

Testing 101: Imaging

CT imaging in the hunt for ectopic ACTH tumors

Once the biochemical evidence of excess ACTH production leads to the diagnosis of Cushing's Syndrome for a patient, the next step is determining the source of excess ACTH production. Usually the source for the excess ACTH is a tumor on the pituitary gland. However, ectopic sources may also be ACTH secreting tumors.

Eighty to 85% of Cushing’s syndrome is ACTH-dependent, of which 80–90% will be due to a pituitary adenoma—Cushing’s disease (CD) [1]. Ten to 15% will have a nonpituitary source, referred to as ectopic ACTH secretion (EAS) [2], of which 80% have an identified source within the chest and abdomen whilst 20% have no detected source and are referred to as occult [1].

This article talks about the use of computed tomography (CT) to locate the source of the EAS. According to the authors, a bilateral inferior petrosal venous sampling (BIPPS) is the first step in determining whether the source of excess ACTH is ectopic, with a 95% sensitivity. They say "false positives are extremely rare (<1%)> and there is a false negative rate of 2–4%".

The authors include information about imaging multiple tumors including the following:

Bronchial carcinoids

Thymic carcinoids

Gastrointestinal carcinoids

Pancreatic neuroendocrine tumours

Medullary thyroid carcinomas

Phaeochromocytomas

They also mention other tumors briefly:

Many tumours have been reported in the literature to result in EAS such asovarian carcinoid, ovarian adenocarcinoma, ovarian androblastoma, ovarian teratoma, ovarian Sertoli cell carcinoma, ovarian dermoid cyst, prostatic adenocarcinoma, prostatic small cell carcinoma, small cell carcinoma of the uterine cervix and olfactory neuroblastoma [6].

The authors recommend the use of ¹¹¹In-octreotide in some cases and mention the enlargement of the adrenals, as well as shape and hyperplasia depending on the type of EAS. They conclude that CT imaging can lead to earlier diagnosis and treatment of these excess ACTH sources.

(Picture is from the article)

Paul A. Sookur, Anju Sahdev, Andrea G. Rockall, Andrea M. Isidori, John P. Monson, Ashley B. Grossman, Rodney H. Reznek (2009). Imaging in covert ectopic ACTH secretion: a CT pictorial review European Radiology DOI: 10.1007/s00330-008-1274-5

Dynamic MR Imaging of the Pituitary: Same tools, different technique (but wow, what a difference!)

Those of us who have suffered or still suffer with pituitary adenomas have heard way too many times "your MRI is normal". I did, for years. Yet, I ultimately did have a proven adenoma which caused my Cushing's disease. If the MRI had shown even an inkling of the tumor to the trained eye, perhaps a doctor would have taken my symptoms more seriously.

So, what makes a difference, then?

Two things made a huge difference for me. First, my current endocrinologist insisted on a dynamic MRI. Secondly, I sent the films and/or CDs to neurosurgeons who remove a lot of pituitary adenomas. What my local radiologist called a "normal" MR image of my pituitary was actually deemed NOT NORMAL by three world-renowned neurosurgeons.

(My local hospital is excellent, but they had never done a dynamic protocol with MR imaging. However, the Taper Imaging Center at Cedars-Sinaii Hospital in Los Angeles bent over backwards to prepare them through phone calls, emails, and reading materials. What a good group of folks! I've met several of them.)

What is a dynamic MRI?

In order to understand that, you need to first understand what an MRI is. Typically, pituitary MRI's are done "without contrast" and "with contrast". The Magnetic Resonance Imaging is done with no radioactivity (aka x-rays). It uses a strong magnetic field produced by a large magnet to send radio waves through the body which "jiggle" the body's atoms. When these atoms move back into place, they send out radio waves of their own which are picked up by the scanner and fed into a computer. This computer then uses programmed algorithms to turn them into pictures. To learn more about it, visit How Stuff Works.

A contrast is often used with MR imaging, especially of the head, to enhance the images. Solutions of gadolinium compounds are typically used as contrast agents. Tumors enhance after gadolinium is given because they tend to absorb the contrast agent either more quickly or less quickly than "normal" tissue. This leads to a "contrast" between the two types of tissue.

What makes a dynamic MRI different from any MRI using contrast?

Typically, a series of images are taken prior to contrast and then the MR imaging is stopped while contrast is injected. Once that is finished, the MRI proceeds with another series of images. With the dynamic protocol, the contrast is infused over a period of time while the MR imaging is taking place. In one study the gadolinium solution was injected via IV over a period of 180 seconds. In another study the gadolinium was dripped via IV between 2 and 3 minutes.

Why does that make a difference?

Pituitary tumors and normal gland tissue absorb the gadolinium at different speeds. The contrast between the normal tissue and tumor may be easier to see in the earlier images when compared to the later ones. Usually the pituitary adenoma enhances slower than the gland. (However, there have been documented cases of just the reverse if the tumor encases a blood supply.) When the tumor enhances slower, a "dark spot", in layman terms, shows up on the pituitary. These are called areas of "hypointensity". This is transitory and if not imaged as it happens, the tumor will enhance to match the gland. (In the picture, the upper image does not clearly show a tumor. The lower image shows the tumor well including its contact with the right internal carotid artery.)

Although I did not mention the strength of the MRI scanners being used, it's probably obvious that the stronger they are (measured in Tesla), the better they work. A 3T scanner is preferable if available, but the authors of the studies used scanners as low as 0.5T in their studies. A scanner is only as good as those operating it, those reading the scans, and the protocols used not matter how strong it is.

Pretty dynamic, huh?

---

For more information in prior threads, see:

Recent Advances in Neuroendocrine Imaging Lead to Improved Diagnosis

Testing 101: Imaging

Recent Advances in Neuroendocrine Imaging Lead to Improved Diagnosis

Imaging is critical in the diagnosis and care of neuroendocrine disorders. The exponential growth of technology has improved techniques and engineering with medical imaging. In turn, this has affected the effectiveness of these tools.

Neuroendocrine tumors and lesions are found on multiple endocrine organs. Imaging of the pituitary, adrenal, thyroid and parathyroid glands are discussed in this article with perfusion metrics as a basis for evaluation. The MRI is touted as the most recent advance in imaging due to the comparison of sequences (pulse versus standard).

Pituitary imaging using 3 T-based MRI with three-dimensional anisotropy contrast is a relatively new approach to determining cavernous sinus invasion with a pituitary tumor. Dynamic MRI imaging is valuable when imaging microadenomas of the pituitary. 3T imaging with MRI increased the localization of small lesions/tumors, and both approaches are more accurate for patients with mild/episodic hypercortisolism. The value of CSS and IPSS are also discussed.

The addition of perfusion MRI aids in the evaluation of prolactinomas and the effectiveness of the treatment with dopamine antagonists. This, in turn, allows more informed decisions with respect to surgical intervention.

A similar protocol is used for patients with acromegaly caused by growth hormone-secreting tumors and who are treated with octreotide.

The newest addition to the evaluation of the adrenal glands is the the use of "MIBG, Octreotide or PET". This is key to avoidance of a bilateral adrenalectomy due to the lack of localization of an ectopic source of ACTH.

Chemical shift imaging is also being used to determine adrenal hyperplasia and tumors. This technique is based upon the "slightly differing resonant frequencies of protons in water and fat in an external magnet field." Hyperaldosteronism, a cause of hypertension, is one diagnosis that has been improved by this. Perfusion metrics are used with these techniques to improve accuracy in diagnosis.

In addition to the normal use of MRI, CT and ultrasound in the evaluation of the thyroid and parathyroid glands, the author talks about the increased use of PET-CT in the treatment of differentiated thyroid carcinomas with patients where conventional whole body scanning did not work. Perfusion imaging of the thyroid using (FAIR)-true fast imaging with steady precession (FISP) sequence is noted as a possible alternative for evaluating thyroid nodules. The same techniques are suggested for parathyroidism.

The author suggests the use of MRI with neuroendocrine disorders is still young, and there will be improvements over time.


Keogh, B.P. (2008). Recent advances in neuroendocrine imaging. Current Opinion in Endocrinology, Diabetes & Obesity, 15(4), 371-375.