Feasibility of Endosphenoidal Coil Placement for Imaging of the Sella During Transsphenoidal Surgery

Tumors of the pituitary gland comprise up to 20% of all brain tumors. The central location
and the small size of the pituitary gland make the management of tumors particularly
challenging. Transsphenoidal surgery (TSS) to resect pituitary tumors is highly successful at
achieving complete cure for functional pituitary adenomas. It is most successful when such
adenomas can be localized by preoperative MRI of the pituitary. However, in some instances,
small functional tumors cannot be visualized. In the case of Cushing s disease (CD), such
non-visualization may be as high as 50%. The success of transsphenoidal surgery is
substantially reduced in patients with negative MRI, as some of the adenomas that cause CD
are so small that they are difficult to find during surgical exploration of the pituitary.
Surgical success is also diminished when tumors invade the walls of the cavernous sinus. MRI
of the pituitary lacks imaging resolution to detect such invasion and so the surgeon cannot
perform a complete resection with surgery based on the preoperative MRI.

Signal to noise ratio (SNR) is the primary constraint on achieving high quality high
resolution MRI images. SNR can be improved by longer scan times or by increasing the field
strength of the MRI magnet. SNR is proportional to the square of imaging time, however, long
imaging times are not clinically feasible. SNR is linearly proportional to field strength,
however, replacing MRI magnets is cost prohibitive.

Another strong determinant of SNR is the proximity of the MRI receiver coil to the tissue
being imaged. Placement of a coil in close proximity to the structure of interest
dramatically increases SNR, often as much as 10-fold. Clinically this is routinely put into
practice for superficial body parts, such as the temporomandibular joints, in which small
coils are placed directly over the joints to achieve rapid high-resolution imaging. For deep
structures, the use of superficial coils is of no benefit. This has led to the development of
endocavitary coils, such as the endorectal coil used to image the prostate gland. Such coils
are now in routine clinical use here at the NIH and elsewhere.

During routine TSS, the surgical approach to the pituitary provides a route for placement of
imaging tools, such as handheld ultrasound and Doppler probes in close proximity to the
gland. Extending this model to MRI imaging, we realized that an endocavitary surface coil
within the sphenoid sinus will allow for a marked improvement in SNR for imaging the sella.
To this end, we have developed an endosphenoidal coil (ESC), demonstrated its MRI safety, and
performed preliminary studies in cadaver heads to determine that the ESC can be placed
through the transsphenoidal approach. Placement of ESC needs no modification in the surgical
TSS approach to the pituitary gland. The goal of this protocol is to examine the safety and
feasibility of ESC placement and imaging during TSS.

Objective

To evaluate the feasibility and safety of using ESC during TSS.

Study Population

The study population will be up to 20 adult subjects with pituitary tumors that require TSS.
Enrollment will be completed once 10 subjects have received the study procedure. The
requested accrual ceiling of 20 subjects accounts for screening failures and drop-outs who do
not receive the study procedure.

Design

This is a feasibility study of 10 subjects requiring TSS for pituitary lesions. The subjects
will undergo standard TSS resection of a pituitary adenoma in the intra-operative MR suite.
Following standard surgical approach, the ESC will be placed into the sphenoid sinus, while
the bone of the sellar floor is still intact. Routine clinical pituitary imaging with and
without intravenous contrast will be performed for comparison with standard pituitary
imaging. Additional higher resolution sequences will be performed as time allows. Following
imaging, standard surgical resection will be performed. Surgeon will not view scans arising
from the research procedure and therefore intraoperative clinical decisions making will not
be influenced by the results of the research imaging.

Outcome Measures

Primary Outcome Measure

The primary outcome of this study is the feasibility of using ESC as a clinical tool during
transsphenoidal surgery. Feasibility will be assessed by the time added to a standard TSS
procedure (measured from the time the TSS exposure is completed to the time to return to the
operating position for completion of surgery).

Safety Outcome Measure

We will evaluate the safety of the ESC as a surgical adjunct tool. We will evaluate whether
the use of ESC causes local trauma, bleeding, burns or other unanticipated safety issues
during TSS.

Exploratory Outcome Measures

Clinical utility of these images will be evaluated by comparing SNR and contrast to noise
ratio (CNR) measurements obtained with the ESC to preoperative standard of care images.

1. Pituitary SNR with ESC MRI versus pre-operative standard of care images.

2. Pituitary to tumor Contrast to Noise Ratio (CNR) with ESC MRI versus pre-operative
standard of care images.

- INCLUSION CRITIERIA:

Adult subjects (more than 18 years of age) will be included in this study if they:

1. Have a known or suspected tumor of the pituitary gland that requires surgical
resection through a transsphenoidal approach. There is no size restriction. Invasion
of surrounding anatomical structures by the pituitary tumor will not be ground for
screen failure/withdrawal from study.

2. Are enrolled in 03-N-0164, Evaluation and Treatment of Neurosurgical Disorders. If not
enrolled, subjects will not be able to be included in the study as clinical and
research procedures are done under the 03-N-0164 protocol.

3. Are able to provide written consent

4. NIH employees are included in the study

EXCLUSION CRITIERIA:

Subjects will be excluded from this study if they:

1. Are unable to fit the intra-operative MRI table due to size or weight restrictions i.e
morbid obesity. Patients will be anaesthetized and therefore claustrophobia will not
be ground for screen failure/withdrawal from study.

2. Have an absolute contraindication to MRI imaging or MRI contrast agent according to
Rad&IS screening including devices or conditions.

3. Have a variant anatomy which may, in the judgment of the operating neurosurgeon, add
unacceptable risk to the placement of the endosphenoidal coil (e.g. small size of
facial bones and nasal passages, unaerated sphenoid sinus etc.).

4. Are pregnant or nursing.

5. Patients older than 65 years of age. Cushing disease is rare in the older population.

The Eligibility Checklist is included as an attachment. This checklist is used by the
investigator at the time of screening for admission to the protocol.