Investigation of the Variability in Tissue Composition for Head/Neck, Thorax, and Abdominal Proton Plans
Session Number
2
Advisor(s)
Hazel Wang, Northwestern Medicine Proton Center
Discipline
Medical and Health Sciences
Start Date
15-4-2026 11:10 AM
End Date
15-4-2026 11:55 AM
Abstract
During proton therapy treatment planning, a 2.5-3.5% range uncertainty margin is often applied distal and proximal to the target volume to account for inaccuracies in the conversion to relative stopping power. However, this uncertainty margin is generalized throughout the body. Factors such as treatment region, beam range, gender, and age varies for each individual. Consequently, the use of a general margin may produce inadequate coverage of the target volume or over-ranging into healthy tissue. This study aimed to investigate the variability of tissue composition and its influence on range uncertainty and identify composition-specific range uncertainty margins for proton treatment planning. Beam paths were obtained from the plans of around 120 consenting patients by intersecting beam specific contours and the 5% isodose line of the maximum dose with the patient surface. SECT and DECT tissue type-specific uncertainties were then weighted based on the beam path composition to determine composition-specific uncertainties. Comparisons were drawn across patient factors, where greater mean uncertainty was observed in female lung and head/neck patients for ranges between 10-25 cm and in adult head/neck patients for ranges between 5-20 cm compared to geriatric patients.
Investigation of the Variability in Tissue Composition for Head/Neck, Thorax, and Abdominal Proton Plans
During proton therapy treatment planning, a 2.5-3.5% range uncertainty margin is often applied distal and proximal to the target volume to account for inaccuracies in the conversion to relative stopping power. However, this uncertainty margin is generalized throughout the body. Factors such as treatment region, beam range, gender, and age varies for each individual. Consequently, the use of a general margin may produce inadequate coverage of the target volume or over-ranging into healthy tissue. This study aimed to investigate the variability of tissue composition and its influence on range uncertainty and identify composition-specific range uncertainty margins for proton treatment planning. Beam paths were obtained from the plans of around 120 consenting patients by intersecting beam specific contours and the 5% isodose line of the maximum dose with the patient surface. SECT and DECT tissue type-specific uncertainties were then weighted based on the beam path composition to determine composition-specific uncertainties. Comparisons were drawn across patient factors, where greater mean uncertainty was observed in female lung and head/neck patients for ranges between 10-25 cm and in adult head/neck patients for ranges between 5-20 cm compared to geriatric patients.