Assessment of contrast enhanced respiration managed cone-beam CT for image guided radiotherapy of intrahepatic tumors.
OBJECTIVE
Contrast enhancement and respiration management are widely used during image acquisition for radiotherapy treatment planning of liver tumors along with respiration management at the treatment unit. However, neither respiration management nor intravenous contrast is commonly used during cone-beam CT (CBCT) image acquisition for alignment prior to radiotherapy. In this study, the authors investigate the potential gains of injecting an iodinated contrast agent in combination with respiration management during CBCT acquisition for liver tumor radiotherapy.


METHODS
Five rabbits with implanted liver tumors were subjected to CBCT with and without motion management and contrast injection. The acquired CBCT images were registered to the planning CT to determine alignment accuracy and dosimetric impact. The authors developed a simulation tool for simulating contrast-enhanced CBCT images from dynamic contrast enhanced CT imaging (DCE-CT) to determine optimal contrast injection protocols. The tool was validated against contrast-enhanced CBCT of the rabbit subjects and was used for five human patients diagnosed with hepatocellular carcinoma.


RESULTS
In the rabbit experiment, when neither motion management nor contrast was used, tumor centroid misalignment between planning image and CBCT was 9.2 mm. This was reduced to 2.8 mm when both techniques were employed. Tumors were not visualized in clinical CBCT images of human subjects. Simulated contrast-enhanced CBCT was found to improve tumor contrast in all subjects. Different patients were found to require different contrast injections to maximize tumor contrast.


CONCLUSIONS
Based on the authors' animal study, respiration managed contrast enhanced CBCT improves IGRT significantly. Contrast enhanced CBCT benefits from patient specific tracer kinetics determined from DCE-CT.
Physics and Engineering, London Regional Cancer Program, London, Ontario N6A3K7, Canada.
Nikolaj K G
NK
Jensen
Radiology, St. Joseph's Health Care, London, Ontario N6A 4V2, Canada; Imaging Research Lab, Robarts Research Institute, London, Ontario N6A 5B7, Canada; and Imaging Program, Lawson Health Research Institute, London, Ontario N6C 2R5, Canada.
Errol
E
Stewart
Radiation Oncology, London Regional Cancer Program, London, Ontario N6A3K7, Canada and Department of Oncology, University of Western Ontario, London, Ontario N6A 4L6, Canada.
Michael
M
Lock
Radiation Oncology, London Regional Cancer Program, London, Ontario N6A3K7, Canada and Department of Oncology, University of Western Ontario, London, Ontario N6A 4L6, Canada.
Barbara
B
Fisher
Radiology, St. Joseph's Health Care, London, Ontario N6A 4V2, Canada.
Roman
R
Kozak
Physics and Engineering, London Regional Cancer Program, London, Ontario N6A3K7, Canada; Department of Oncology, University of Western Ontario, London, Ontario N6A 4L6, Canada; and Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 5C1, Canada.
Jeff
J
Chen
Radiology, St. Joseph's Health Care, London, Ontario N6A 4V2, Canada; Imaging Research Lab, Robarts Research Institute, London, Ontario N6A 5B7, Canada; Imaging Program, Lawson Health Research Institute, London, Ontario N6C 2R5, Canada; Department of Oncology, University of Western Ontario, London, Ontario N6A 4L6, Canada; and Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 5C1, Canada.
Ting-Yim
TY
Lee
Physics and Engineering, London Regional Cancer Program, London, Ontario N6A3K7, Canada; Department of Oncology, University of Western Ontario, London, Ontario N6A 4L6, Canada; Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 5C1, Canada; and Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada.
Eugene
E
Wong
D000368:Aged; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging / Q000532:radiotherapy; D003198:Computer Simulation; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003287:Contrast Media; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D008297:Male; D009038:Motion; D009368:Neoplasm Transplantation; D011817:Rabbits; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012119:Respiration
D003287:Contrast Media