Emily L Marshall1, David Borrego2, James C Fudge3, Dhanashree Rajderkar4, Wesley E Bolch1. 1. J. Crayton Pruitt Family, Department of Biomedical Engineering, University of Florida, Gainesville, FL, USA. 2. Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA. 3. Div. of Pediatric Cardiology, UF Health Congenital Heart Center, University of Florida, Gainesville, FL, USA. 4. Department of Radiology, Chief of Pediatric Radiology, University of Florida, Gainesville, FL, USA.
Abstract
PURPOSE: To assess various computational phantom alignment techniques within Monte Carlo radiation transport models of pediatric fluoroscopically guided cardiac interventional studies. METHODS: Logfiles, including all procedure radiation and machine data, were extracted from a Toshiba infinix-I unit in the University of Florida Pediatric Catheterization Laboratory for a cohort of 10 patients. Two different alignment methods were then tested against a ground truth standard based upon identification of a unique anatomic reference point within images co-registered to specific irradiation events within each procedure. The first alignment method required measurement of the distance from the edge of the exam table to the top of the patient's head (table alignment method). The second alignment method fixed the anatomic reference point to be the geometric center of the heart muscle, as all 10 studies were cardiac in nature. Monte Carlo radiation transport simulations were performed for each patient and intervention using morphometry-matched hybrid computational phantoms for the reference and two tested alignment methods. For each combination, absorbed doses were computed for 28 organs and root mean square organ doses were assessed and compared across the alignment methods. RESULTS: The percent error in root mean square organ dose ranged from -57% to +41% for the table alignment method, and from -27% to +22% for the heart geometric centroid alignment method. Absorbed doses to specific organs, such as the heart and lungs, demonstrated higher accuracy in the heart geometric centroid alignment method, with average percent errors of 10% and 1.4%, respectively, compared to average percent errors of -32% and 24%, respectively, using the table alignment method. CONCLUSIONS: Of the two phantom alignment methods investigated in this study, the use of an anatomical reference point - in this case the geometric centroid of the heart - provided a reliable method for radiation transport simulations of organ dose in pediatric interventional cardiac studies. This alignment method provides the added benefit of requiring no physician input, making retrospective calculations possible. Moving forward, additional anatomical reference methods can be tested to assess the reliability of anatomical reference points beyond cardiac centered procedures.
PURPOSE: To assess various computational phantom alignment techniques within Monte Carlo radiation transport models of pediatric fluoroscopically guided cardiac interventional studies. METHODS: Logfiles, including all procedure radiation and machine data, were extracted from a Toshiba infinix-I unit in the University of Florida Pediatric Catheterization Laboratory for a cohort of 10 patients. Two different alignment methods were then tested against a ground truth standard based upon identification of a unique anatomic reference point within images co-registered to specific irradiation events within each procedure. The first alignment method required measurement of the distance from the edge of the exam table to the top of the patient's head (table alignment method). The second alignment method fixed the anatomic reference point to be the geometric center of the heart muscle, as all 10 studies were cardiac in nature. Monte Carlo radiation transport simulations were performed for each patient and intervention using morphometry-matched hybrid computational phantoms for the reference and two tested alignment methods. For each combination, absorbed doses were computed for 28 organs and root mean square organ doses were assessed and compared across the alignment methods. RESULTS: The percent error in root mean square organ dose ranged from -57% to +41% for the table alignment method, and from -27% to +22% for the heart geometric centroid alignment method. Absorbed doses to specific organs, such as the heart and lungs, demonstrated higher accuracy in the heart geometric centroid alignment method, with average percent errors of 10% and 1.4%, respectively, compared to average percent errors of -32% and 24%, respectively, using the table alignment method. CONCLUSIONS: Of the two phantom alignment methods investigated in this study, the use of an anatomical reference point - in this case the geometric centroid of the heart - provided a reliable method for radiation transport simulations of organ dose in pediatric interventional cardiac studies. This alignment method provides the added benefit of requiring no physician input, making retrospective calculations possible. Moving forward, additional anatomical reference methods can be tested to assess the reliability of anatomical reference points beyond cardiac centered procedures.
Authors: Perry B Johnson; David Borrego; Stephen Balter; Kevin Johnson; Daniel Siragusa; Wesley E Bolch Journal: Med Phys Date: 2011-10 Impact factor: 4.071
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