Main Session
Sep 29
QP 33 - Advances in Planning Algorithm and Optimization

1194 - Develop a Novel Non-Coplanar Trajectory Optimization Algorithm for an Efficient 4pi Spot-Scanning Proton Arc (SPArc-4pi) Treatment Delivery

05:25pm - 05:30pm ET
Room 160

Presenter(s)

Xiaoda Cong, MS Headshot
Xiaoda Cong, MS - Corewell Health William Beaumont University Hospital, Royal Oak, MI

X. Cong1, S. Chen1, P. Liu2, X. Xu2, X. Li2, P. Chen3, P. Chinnaiyan2, R. L. Deraniyagala Jr1, and X. Ding2; 1Corewell Health William Beaumont University Hospital, Royal Oak, MI, 2Department of Radiation Oncology, Corewell Health William Beaumont University Hospital, Royal Oak, MI, 3Beaumont University Hospital Corewell Health System, Royal Oak, MI

Purpose/Objective(s):

This study aims to develop the first 4pi dynamic proton arc optimization algorithm which searches for efficient arc trajectories in 4pi space, explores the potential dosimetric improvements in multiple disease sites. Then we demonstrate its feasibility through simulation using a clinical proton therapy system.

Materials/Methods:

Dynamic Programming was translated into this new concept of the 4p SPArc optimization algorithm (SPArc-4pi) for the trajectory search and route decision-making. It breaks down the complicated and high-computational-demand main problem into a series of small sub-problems and searches for delivery-efficient 4pi arc trajectories through an iterative approach. Three different disease sites, e.g., head & neck, partial brain, and clival brain chordoma, were used for testing purposes. Conventional Intensity Modulated Proton Therapy (IMPT) and 2D co-planar arc (SPArc-2d) plans were generated as a benchmark. Treatment delivery efficiency was evaluated through a published and validated dynamic arc system controller. Plan quality was assessed through target coverage and organ at risk (OAR) sparing.

Results:

The new SPArc-4pi demonstrated superior dosimetric performance across various evaluation metrics for all three disease sites. The simulation result shows that SPArc-4pi is able to be delivered within a reasonable time of around 5 to 11 mins, which is comparable to the SPArc-2d plans.

Conclusion:

The study introduced the first optimization algorithm for SPArc-4pi technique. It not only showed SPArc-4pi ‘s potential to improve the plan quality via a greater degree of freedom compared to the conventional IMPT and state-of-art 2D co-planar SPArc-2d technique but also demonstrated its feasibility for future clinical implementation based on the current proton beam therapy system’s machine characteristics.

Table 1 Dosimetric Comparison among IMPT, SPArc-2d and SPArc-4pi

Structure

 Value

 IMPT

 SPArc-2d

 SPArc-4pi
Clival Chordoma
CTV-7020cGy

 V100(%)

 78.75

 80.37

 82.27
CI

 0.52

 0.61

 0.61
CTV-5040cGy

 D98(Gy)

 52.94

 50.67

 50.68

CI

 0.33

 0.43

 0.52
Brain Stem

 Max(Gy)

 58.65

 55.58

 53.41
Mean(Gy)

 26.08

 15.31

 10.62
Spinal Cord

 Max(Gy)

 19.73

 11.28

 7.45
Optic Chiasm

 Max(Gy)

 52.02

 49.46

 40.33
Left Optic Nerve

 Max(Gy)

 50.45

 48.15

 47.46
Right Optic Nerve

 Max(Gy)

 46.47

 45.34

 42.53
Oral Cavity

 Max(Gy)

 14.21

 4.86

 1.30
Integral Dose

 (Gy*L)

 21.56

 18.84

 15.14
Partial Brain
CTV

 V98(%)

 97.06

 97.46

 98.47
CI

 0.69

 0.86

 0.90
Brain Stem

 Max(Gy)

 6.07

 1.69

 0.30
Left Hippocampus

 Max(Gy)

 16.67

 13.28

 7.98
Right Hippocampus

 Max(Gy)

 35.03

 30.25

 27.17
Optic Chiasm

 Max(Gy)

 31.25

 30.84

 30.18
Left Optic Nerve

 Max(Gy)

 31.88

 31.52

 31.50
Right Optic Nerve

 Max(Gy)

 31.75

 31.70

 30.60
Integral Dose

 (Gy*L)

 39.62

 36.30

 32.30
Bilateral HN
CTV-high

 V98(%)

 99.05

 99.08

 99.04
CI

 0.37

 0.39

 0.40
CTV-low

 V98(%)

 99.03

 99.16

 99.18
CI

 0.32

 0.35

 0.36
Brain Stem

 Max(Gy)

 24.38

 17.89

 14.35
Mean(Gy)

 7.09

 3.58

 1.70
Spinal Cord

 Max(Gy)

 26.84

 2.75

 2.18
Mandible

 Max(Gy)

 53.41

 53.71

 49.20
Integral Dose

 (Gy*L)

 117.94

 114.59

 112.83