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WE‐D‐330A‐03: PO2 Measurements in Animal Tumors Using An Image‐Guided Robotic System
Author(s) -
Chang J,
Wen B,
Kazanzides P,
Zanzonico P,
Finn R,
Ling C
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2241741
Subject(s) - fiducial marker , artificial intelligence , robot , voxel , image registration , nuclear medicine , computer vision , biomedical engineering , computer science , physics , medicine , image (mathematics)
Purpose: To develop and evaluate an image‐guided robotic system for measuring pO 2 in animal tumors. Method and Materials: The robot consists of an X‐Y horizontal platform holding the rodent bed, a dual‐axis vertical arm for positioning the measurement probe and cannula, and fiducial markers for registering the coordinates of the imaging and robotic systems. Anesthesized and immobilized tumor‐bearing rats are injected with the hypoxia tracer 18 F‐FMISO and imaged in the rodent bed using an animal PET scanner. The reconstructed PET images are then uploaded into the robot computer, the rodent bed affixed to the X‐Y platform, and the coordinates of the robot and PET registered. Based on the tumor hypoxia image displayed on the robot computer, motion of the robotic X‐Y platform and vertical arm are coordinated to guide the positioning and percutaneous insertion of a probe (OxyLite‐Optronix) to measure pO 2 at various locations in the tumor. The pO 2 readings (cps/voxel) are then compared to the respective image intensity of the measurement points. Results: The registration accuracy between the robot and image coordinate system was better than 0.2mm. Although the 18 F‐FMISO in the bladder produced characteristic starburst artifacts in the surrounding, low‐intensity regions, we successfully measured the pO 2 for three tracks. The 18 F‐FMISO image voxel values were found to be inversely correlated with the intra‐tumoral pO 2 of the three tracks with (Pearson product moment) correlation coefficients of −0.899, −0.420 and −0.857. The scatter plot of pO 2 vs. image intensity resembled a sigmoidal, rather than a linear relationship. Conclusion: PET‐guided pO 2 measurement is feasible using this prototype image‐guided robot system. To our knowledge, this is the first system of its kind — allowing direct point‐by‐point correlation of physiological probe measurements and image voxel values or, more generally, a physical action at a set of anatomic points identified on a preoperative image.