TU-EF-304-06: A Comparison of CT Number to Relative Linear Stopping Power Conversion Curves Used by Proton Therapy Centers
- UT MD Anderson Cancer Center, Houston, TX (United States)
Purpose: To compare the CT Number (CTN) to Relative Linear Stopping Power (RLSP) conversion curves used by 14 proton institutions in their dose calculations. Methods: The proton institution’s CTN to RLSP conversion curves were collected by the Imaging and Radiation Oncology Core (IROC) Houston QA Center during its on-site dosimetry review audits. The CTN values were converted to scaled CT Numbers. The scaling assigns a CTN of 0 to air and 1000 to water to allow intercomparison. The conversion curves were compared and the mean curve was calculated based on institutions’ predicted RLSP values for air (CTN 0), lung (CTN 250), fat (CTN 950), water (1000), liver (CTN 1050), and bone (CTN 2000) points. Results: One institution’s curve was found to have a unique curve shape between the scaled CTN of 1025 to 1225. This institution modified its curve based on the findings. Another institution had higher RLSP values than expected for both low and high CTNs. This institution recalibrated their two CT scanners and the new data placed their curve closer to the mean of all institutions. After corrections were made to several conversion curves, four institutions still fall outside 2 standard deviations at very low CTNs (100–200), and two institutions fall outside between CTN 850–900. The largest percent difference in RLSP values between institutions for the specific tissues reviewed was 22% for the lung point. Conclusion: The review and comparison of CTN to RLSP conversion curves allows IROC Houston to identify any outliers and make recommendations for improvement. Several institutions improved their clinical dose calculation accuracy as a Result of this review. There is still area for improvement, particularly in the lung area of the curve. The IROC Houston QA Center is supported by NCI grant CA180803.
- OSTI ID:
- 22565366
- Journal Information:
- Medical Physics, Journal Name: Medical Physics Journal Issue: 6 Vol. 42; ISSN 0094-2405; ISSN MPHYA6
- Country of Publication:
- United States
- Language:
- English
Similar Records
SU-E-T-772: Uncertainties in Treatment Planning for IROC-Houston Proton Phantom QA Program Due to Variable CT Technique and Proton Energy
TU-G-BRD-06: The Imaging and Radiation Oncology Core Houston (IROC Houston) QA Center International Activities Outside North America
SU-F-T-181: Proton Therapy Tissue-Equivalence of 3D Printed Materials
Journal Article
·
Mon Jun 15 00:00:00 EDT 2015
· Medical Physics
·
OSTI ID:22555139
TU-G-BRD-06: The Imaging and Radiation Oncology Core Houston (IROC Houston) QA Center International Activities Outside North America
Journal Article
·
Mon Jun 15 00:00:00 EDT 2015
· Medical Physics
·
OSTI ID:22569990
SU-F-T-181: Proton Therapy Tissue-Equivalence of 3D Printed Materials
Journal Article
·
Wed Jun 15 00:00:00 EDT 2016
· Medical Physics
·
OSTI ID:22642422