Ken Young Lin BS, Presenter: Nothing to Disclose

Christian Pfeffer, Abstract Co-Author: Nothing to Disclose

Marco Andre Maricevich MD, Abstract Co-Author: Nothing to Disclose

Ralph Weissleder MD, PhD, Abstract Co-Author: Board of Directors, VisEn Medical, Inc

Umar Mahmood MD, PhD, Abstract Co-Author: Consultant, VisEn Medical, Inc Stockholder, VisEn Medical, Inc

CARS forms images based on the amount of Raman-active molecular bond vibration within the sample at a given input energy level. When the laser frequencies are set to match the vibrational resonance of specific molecules, a strong optical response occurs. Since cell membranes are rich in C-H bond, we excited this bond to evaluate the system’s ability to perform in vivo cell imaging based on endogenous membrane lipids by 1) imaging pancreatic acini cells in vivo, 2) visualizing intracellular vesicles in acini cells, and 3) determining acini cell polarity based on the location of these vesicles.

Nude mice were anesthetized prior to laparotomy and orotracheal intubation. Mice were ventilated with 5 second suspension to allow imaging of the pancreas without motion artifacts. Tunable picosecond HQ lasers were used for CARS imaging at 2700-2850/cm wave range.

We were able to visualize acinar units in situ using only the C-H bond vibration signal that came from the endogenous lipids. Digestive enzyme-containing vesicles were clearly seen preferentially localized to the apical end of the acinar cells. These vesicles were estimated to have a 400nm diameter. Via 3D reconstruction of individual optical section, we estimated each acinar cell to contain around 700 vesicles all tightly packed at the apical half of the cell. The basolateral part of the acinar cell contained hypo-intensity round area that corresponds to the nucleus. The course of the pancreatic ductules could be clearly seen by the distribution of pancreatic vesicles, which all localized near the apical membrane juxtaposing the ductule lumen. Ductal cells and fibroblasts gave very low signal intensity; however, erythrocytes generated high signal intensity.

We showed that by using CARS in vivo it is possible to image acinar cell membrane and vesicles at subcellular resolution in real time without any fluorophores or contrast agents. We also observed acinar cell polarity based on the location of the acinar vesicles.

CARS’ ability to detect cell polarity may be applied to image polarity defect found in certain types of pancreatitis. CARS can potentially be modified into a fiber-optic system and used in IR.

Lin, K, Pfeffer, C, Maricevich, M, Weissleder, R, Mahmood, U, Coherent Anti-Stokes Raman Scattering (CARS) Imaging Reveals Pancreatic Acini at Subcellular Resolution in Vivo.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5008088.html