Study done to improve quality assurance in Radiation Therapy by expanding dimensions of dose comparisons between measured and calculated dose

1. Augmentation of Quality Assurance in Radiation Therapy
Oluwadamilola Fasina, Dr. Guoqiang Cui, and Dr. Jun Duan
Department of Radiation Oncology, Duke Hospital, Raleigh, North Carolina
INTRODUCTION/AIM
METHODS
BACKGROUND
FUTURE WORK
CONCLUSION
Cancer, a deadly disease where your cells multiply uncontrollably, is the
second leading cause of death in the United States. Treatment options
for cancer are surgery, chemotherapy, and radiation therapy. Radiation
Therapy as a treatment option involves the steps depicted below.
A type of radiotherapy used for brain metastases is stereotactic
radiosurgery (SRS). A high spatial-resolution 2D detector array, the
SRS MapCHECK (Sun Nuclear Corporation, Melbourne, FL) is
routinely used for SRS patient-specific QA, which is performed by
placing the 2D detector array in a domed cylindrical phantom and
measuring a dose distribution to be compared with a calculated 2D
dose distribution from a treatment planning system (TPS). The goal
of the study is to improve the QA by expanding the dose comparison
from 2D dose distributions to 3D dose distributions.
Linear Interpolation of Cylindrical Geometry
Measured vs Quasi Measured: Validation of
Interpolation Method
Calculated Dose from TPS vs Quasi Measured
ACKNOWLEDGEMENTS
𝑦 − 𝑦1
𝑥 − 𝑥1
=
𝑦2 − 𝑦1
𝑥2 − 𝑥1
• Detector spans height, h, of cylinder
• Measurements occur by rotating
detector about center of base and
delivering dose at four angles: 0, 45,
90, 135.
• Interpolation is then performed
between these angles on the plane of
the base and span the entire height, h.
• In standard interpolation equation
above, y represents dose and x
represents degrees in radians.
One Twenty
DegreesSixty DegreesThirty Degrees
RESULTS
Thirty Degrees
One Twenty
DegreesSixty Degrees
Percent
Difference
(%)
30 degrees 60 degrees 120 degrees
Measured vs
Quasi
Measured
1.627 .827 .63
Quasi-
measured vs
Calculated
2.68 1.23 2.34
• Actual and Quasi measured
comparison demonstrate
interpolated coronal planes
are sufficiently close to
calculated plans from TPS.
• Thus, generation of 3D
measured volumetric dose
distribution via linear
interpolation is feasible and
can be compared to 3D
calculated dose distribution
from TPS for better QA
• High dose region (yellow in
picture to the left) has
extremely low percent
difference for both
comparisons.
• Create 3D volumetric dose distribution
• Perform same analysis with Sagittal and
Axial planes
• Perform gamma analysis – standard
verification method used in medical
physics
• Incorporate couch kick to expand quality
assurance
• NC State Women and Minority in Engineering Program
• Duke Radiation Oncology, Raleigh, NC
• Calvo, O., S. Stathakis, A. N. Gutiérrez, C. Esquivel, and N.
Papanikolaou. 2012. “3D Dose Reconstruction of
Pretreatment Verification Plans Using Multiple 2D Planes
from the OCTAVIUS/Seven29 Phantom Array.” Technology in
Cancer Research & Treatment 11 (1): 69–82.
doi:10.7785/tcrt.2012.500236
One Twenty
Degrees