Trimodal CT/Endoscopic Visualization of Cadaveric Nasal Vasculature
Adrian E. House, Anand K. Devaiah, MD, FACS
Department of Otolaryngology, Department of Anatomy & Neurobiology
Boston University School of Medicine
Medical Student Summer Research Program (MSSRP)
Summer 2013
Abstract
Abstract
Results
Results
Knowledge of a patient’s vasculature is critical for any surgery.
The vascular tree of the nasal cavity, in particular, is used to
determine the most viable mucosal sections for flap
reconstruction in skull based procedures. In such procedures, a
hole is created in the skull base to provide access to the cranial
fossae for tumor removal. Once the neoplasm is removed, the
aperture must be sealed to prevent cerebral spinal fluid (CSF)
leakage. This can be achieved through the use of a vascularized
nasoseptal flap as an autologous sealant. This minimizes CSF
leakage and immunological rejection, while maximizing the
longevity of the graft.
However, to complete this, the surgeon is faced with the task of
determining which sections of the nasal cavity have the highest
probability of surviving after being repositioned. This probability
strongly correlates with the mucosal flap’s blood supply.
Knowledge of both the location and supply field of this vasculature
would, therefore, be of great value in selecting the most reliable
mucosal flaps. This project has been designed to determine the
best methodology for visualizing the vasculature of the nasal
cavity and conveying that in a clear, informative manner.
Fig. 4 – Left image: 3D CT reconstruction of bone and vasculature, postlatex-barium-fluorescein injection. Bottom right arrow identifies nasal
branches of the left facial artery, while the two left arrows identify
branches of the maxillary artery, entering the nasal cavity from the
pterygopalatine fossa.
Right image: Coronal section 2D CT reconstruction. Bone window. Arrow
labels the ophthalmic branch of the left internal carotid artery, post-latexbarium-fluorescein injection. This shows extent of vessel filling, giving a
demonstrated perfusion of vessels roughly 0.5-1.0 mm in diameter.
Several latex-barium-fluorescein mixtures were designed and
tested. One was selected, injected into a cadaver and visualized
with CT imaging. The lateral side of the head was later dissected
to reveal branches of the external carotid and maxillary arteries.
Methods
For experimental purposes, human
cadavers were used, which
Background
were graciously donated through the BUSM Anatomical Gifts
program. These bodies were preserved with a traditional
formaldehyde-based solution. The carotid triangle was then
dissected to reveal the left common carotid artery. In order to
provide data about the blood supply to the nasal cavity, three
visualization techniques were combined: dissection, endoscopy,
and radioscopy.
To highlight the vessels for dissection and identification, 100 mL of
red latex was used as a solution base. To this, 7.5 mL a synthetic
fluorescent tracer, fluorescein, was added. This organic compound
has a peak excitation at 494 nm (blue visible light), allowing
maximum visualization with a simple endoscopic light filter. Finally,
25 g of barium sulfate solid was vortexed into 20 mL of tap water
and slowly stirred into the latex-fluorescein solution at a
temperature of 40ºC, thus creating a radiopaque suspension that
is both visibly and fluorescently active. This was confirmed by xray and digitally photography of injected vessels illuminated with
494 nm visible light.
After extensively mixing the solution to ensure uniform suspension
of the barium, the solution was injected into the left common
carotid artery under low PSI with an infusion pump. A 1.5 cm
incision was made in the terminal area of the left superficial
temporal artery to confirm perfusion. Once solution began to leak
from this site, an additional 10 mL was added to ensure complete
carotid filling -- about 60 mL total. The carotid artery was then tied
off and the body was moved to a dark room, in an effort to prevent
photobleaching of the fluorescein. Later this week, 54 hours post
injection, the cadaver was imaged with a CT scanner at Boston
Medical Center.
Fig. 1 – Left side, 3D CT reconstruction, post-latex-barium-fluorescein injection.
Arrows highlight branch vessels of the nasal cavity off the maxillary artery. All solid
white vessels on the image represent radio-opacity of the latex-barium-fluorescein
mixture.
The most significant challenges I encountered working on this project
were finding optimal blending methods for incorporating insoluble barium
sulfate into the solution, as well as planning around the delays inherent
in latex coagulation. Since barium sulfate only dissolves readily in
sulfuric acid, a suspension of the radiopaque compound was necessary
for injection. In hindsight, I would have ordered more latex earlier and
dissected out several vessels to inject at differing concentrations so that I
would not have to wait for the latex to solidify before altering the dose of
barium. Additionally, I ideally would have obtained liquid barium -- a
stabilized suspension that I could have simply added to the latex, rather
than dealing with a technique for suspending solid barium in solution.
Summary
Summary
Fig. 2 – Left side, 2D CT reconstruction, bone window, post-latex-barium-fluorescein
injection. Arrows highlight septal vessels of the nasal cavity. Note extensive
meningeal and cerebral artery enhancement.
•
A solution of 25g Barium/100mL red latex was made for injection
purposes
•
7.5 mL of fluorescein was added to give future fluorescent
endoscopic imaging opportunities
•
CT Scans of the cadaver were taken, with varying imaging windows
•
Cadaver was superficially dissected to measure extent of vessel
filling and to correlate imaging results with cadaveric anatomy.
•
Fluorescent endoscopic images in the near future with also be
compare to the dissection and scan images, giving potential for
additional injections and clinical research.
Future Directions
As a future direction, CT and endoscopic images will be obtained from the
injection and a potential alternative, clear, gelatin-based solution to
Future
Studies and barium will be explored
suspend higher concentrations
of fluorescein
if the results are not as desired. It is our hopes that these results will also
simulate future research of the use of fluorescent and radiopaque
compounds in the operating room, which could provide clinicians with
direct, rapid visualization of nasoseptal vasculature if they chose to inject
the already-FDA-approved fluorescein.
Objectives
1. To develop an injectable
solution that can be visualized
Objectives
with CT imaging and fluorescent endoscopy
2. To examine the vascular supply to the mucosa of the
floor of the nose, with the idea that this knowledge would
help us in designing alternate flaps for intranasal/skull
base reconstruction
3. To determine the best methodology for visualizing the
vasculature of the nasal cavity and conveying that in a
clear, informative manner.
Challenges
Acknowledgements
Acknowledgements
Fig. 3 – Trial injections of cadaveric hands (right & bottom left) with varying
techniques and concentrations of latex vs. barium. Top right image is a superficial
dissection of the final cadaver, post-latex-barium-fluorescein injection, identifying the
superficial temporal artery with the two arrows on the left.
This project was funded by Jane R. Clark, M.D. (Julia & Seymour Gross Foundation, Inc.)
Thank you, as well to Dr. Devaiah, the PI on this project. He is truly a gem in the arena of academic medicine.
His demonstrated probity, unsurpassable level of passion for his students’ success, and fascination with the
intricacies of medical research made working with him this summer an absolute pleasure.