| Title: |
Determination of output factor for CyberKnife using scintillation dosimetry and deep learning |
| Authors: |
Ocampo, Jeremy; Heyes, Geoff; Dehghani, Hamid; Scanlon, Tim; Jolly, Simon; Gibson, Adam P |
| Source: |
Physics in Medicine & Biology , 69 (2) , Article 025024. (2024) |
| Publisher Information: |
IOP Publishing |
| Publication Year: |
2024 |
| Collection: |
University College London: UCL Discovery |
| Subject Terms: |
cyberknife; deep learning; output factor; photography; small field dosimetry; solid plastic scintillator |
| Description: |
OBJECTIVE: Small-field dosimetry is an ongoing challenge in radiotherapy quality assurance especially for radiosurgery systems such as CyberKnifeTM. The objective of this work is to demonstrate the use of a plastic scintillator imaged with a commercial camera to measure the output factor of a CyberKnife system. The output factor describes the dose on the central axis as a function of collimator size, and is a fundamental part of CyberKnife quality assurance and integral to the data used in the treatment planning system. APPROACH: A self-contained device consisting of a solid plastic scintillator and a camera was build in a portable Pelicase. Photographs were analysed using classical methods and with convolutional neural networks to predict beam parameters which were then compared to measurements. MAIN RESULTS: Initial results using classical image processing to determine standard quality assurance parameters such as percentage depth dose were unsuccessful, with 34% of points failing to meet the Gamma criterion (which measures the distance between corresponding points and the relative difference in dose) of 2mm/2%. However, when images were processed using a convolutional neural network trained on simulated data and a green scintillator sheet, 92% of percentage depth dose curves agreed with measurements with a microdiamond detector to within 2mm/2% and 78% to 1%/1mm. The mean difference between the output factors measured using this system and a microdiamond detector was 1.1%. Confidence in the results was enhanced by using the algorithm to predict the known collimator sizes from the photographs which it was able to do with an accuracy of less than 1 mm. SIGNIFICANCE: With refinement, a full output factor curve could be measured in less than an hour, offering a new approach for rapid, convenient small-field dosimetry. |
| Document Type: |
article in journal/newspaper |
| File Description: |
application/pdf |
| Language: |
English |
| Relation: |
https://discovery.ucl.ac.uk/id/eprint/10186168/1/Ocampo_2024_Phys._Med._Biol._69_025024.pdf; https://discovery.ucl.ac.uk/id/eprint/10186168/ |
| Availability: |
https://discovery.ucl.ac.uk/id/eprint/10186168/1/Ocampo_2024_Phys._Med._Biol._69_025024.pdf; https://discovery.ucl.ac.uk/id/eprint/10186168/ |
| Rights: |
open |
| Accession Number: |
edsbas.D9D93590 |
| Database: |
BASE |