Event Title

Improving In Vitro PTV Approximations for Proton Therapy

Session Number

Project ID: MEDH 03

Advisor(s)

Steve Laub (Physicist); Northwestern Proton Center

Mark Pankuch (Head Physicist); Northwestern Proton Center

Discipline

Medical and Health Sciences

Start Date

22-4-2020 8:30 AM

End Date

22-4-2020 8:45 AM

Abstract

When designing therapeutic proton plans, it is important that the amount of healthy cells affected is minimal. The target area, which includes the tumor and the “error margin” around it, is called the planned target volume (PTV). The PTV is used to ensure the tumor receives the appropriate amount of dose, even if there are clinically reasonable set up errors. The trade-off is that surrounding healthy structures may also receive treatment-level doses. This may cause damage to healthy tissue, which presents as clinical toxicities. Using an estimate of the PTV from the patients’ treatment data, the Northwestern Medicine Proton Center plans to find a correlation between the PTV area and the presence of clinical toxicities. It is difficult, however, to find a correlation with approximations, so we created a computer application that approximates the PTV more accurately. Previously, treatment areas were estimated using the radius of the tumor and calculating a circle of area around the center. However, due to the irregular shape of tumors, these estimations can be very inaccurate. Our program uses the coordinates from uniform proton therapy treatments, relative to the iso-center, to calculate the area using Heron’s formula and a multitude of triangles extending from the area’s midpoint.

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Apr 22nd, 8:30 AM Apr 22nd, 8:45 AM

Improving In Vitro PTV Approximations for Proton Therapy

When designing therapeutic proton plans, it is important that the amount of healthy cells affected is minimal. The target area, which includes the tumor and the “error margin” around it, is called the planned target volume (PTV). The PTV is used to ensure the tumor receives the appropriate amount of dose, even if there are clinically reasonable set up errors. The trade-off is that surrounding healthy structures may also receive treatment-level doses. This may cause damage to healthy tissue, which presents as clinical toxicities. Using an estimate of the PTV from the patients’ treatment data, the Northwestern Medicine Proton Center plans to find a correlation between the PTV area and the presence of clinical toxicities. It is difficult, however, to find a correlation with approximations, so we created a computer application that approximates the PTV more accurately. Previously, treatment areas were estimated using the radius of the tumor and calculating a circle of area around the center. However, due to the irregular shape of tumors, these estimations can be very inaccurate. Our program uses the coordinates from uniform proton therapy treatments, relative to the iso-center, to calculate the area using Heron’s formula and a multitude of triangles extending from the area’s midpoint.