A Collapsed cone convolution Dose Engine suitable for Workflows
Secondary Dose check and Patient QA Tasks in online Adaptive
EFOMP NEWSLETTER SPING ISSUE 03/2025 | COMPANY MEMBER ΑRTICLE
ThinkQA Secondary Dose Check (SDC) solution from DOSIsoft re-calculates a dose distribution in a three-dimensional representation of the
patient (or a phantom) and provides dose-volume indicators which compare this dose distribution to the initial dose distribution calculated
by the treatment planning system.
The solution relies on its modern dose calculation engine, an up-to-date point kernel Collapsed Cone Convolution (CCC) algorithm and
implementation, tailored to comply with the specific requirements of online adaptive radiotherapy, including the Elekta Unity MR-linac
specific considerations.
This class of CCC algorithms and specific implementation has been demonstrated appropriate for SDC tasks integrated into an online
adaptive workflow, and provides additional value compared to Monte Carlo class of algorithms in terms of efficiency, practical advantages
and as central architecture component of a wider Patient-QA solution.
The CCC dose engine in the ThinkQA solution is not only used to perform a secondary dose check, it is also a key component of a wider
Patient-specific Quality Assurance solution, which becomes a mandatory element of modern online adaptive treatment workflows, using
either MR- or CT-linacs.
In an online adaptive context, ThinkQA SDC dose engine can be used to compute dose distributions in different contexts throughout the
global treatment course:
Secondary dose check,
EPID-based pre-treatment (phantom-less control) plan delivery check (predicted dose image and dose conversion portal image),
Beam delivery logfiles based verification (fluence reconstruction or 3D dose calculation in patient anatomy), and
EPID-based in-vivo transit dosimetry
In such a context, the same versatile TQA SDC dose engine is to be used to compute 3D dose distributions, or 2D predicted dose at a certain
distance from source. It is key for such a comprehensive Patient-QA solution to use the same dose engine, tailored only once through beam
templates and models. Re-using the same dose engine for several various purposes will simplify the overall commissioning and validation of
the global solution and reduce the risk of biases introduced by different engines and algorithms.
Secondary Dose Calculation systems like TQA SDC play an essential role in ensuring the safety and efficacy of radiotherapy treatments. By
combining an advanced dose engine, robust patient modelling and compatibility with online adaptive systems like Elekta Unity or Elekta
Evo, this tool will help enhance clinical confidence, patient safety and treatment quality for each individual patient.
TQA SDC Collapsed Cone Convolution (CCC) dose engine provides a comprehensive set of differentiating features, which makes it suitable
for efficient Secondary Dose Checks and wider Patient QA tasks, in the context of the new online adaptive radiotherapy workflows.
The deterministic accuracy of the Collapsed Cone Convolution (CCC) dose engine, in contrary to the inherent statistical uncertainty of MC methods and the tradeoff required in these methods between computation time and accuracy.
The computational efficiency of the Collapsed Cone Convolution (CCC) dose engine, by nature of its optimized algorithm, its efficient
implementation inside the ThinkQA software device, and through the use of CPU and GPU parallel computing techniques and
hardware systems.
Its compatibility with the Elekta MR-linac Unity, designed for MRgRT. The enhanced CCC dose engine uses an innovative specific
Unity beam template: a warped poly-energetic point kernel (specifically defined by Monte Code for the Unity beam spectrum)
analytically fitted by an original double fit method, a user-defined cryostat transmission table, a detailed description and
management of support and accessories (coils), and the ability to filter regions with ERE effects.
Its validated clinical performance, demonstrated for various energies and treatment techniques including IMRT and VMAT, always
under strict tolerance (2%/2mm, local, 95% of gamma passing rate).
Its validation and compatibility for verification of plans generated by MC TPS: algorithmic independence, dose-to-water/dose-to
medium conversion configuration.
Its independence of both computational method used and also fast going into service in complete security by providing ready-to
use standard beam templates for quick commissioning.
Its applicability to clinical online adaptive workflows, either “Adapt-To-Position” or “Adapt-To-Shape”, requiring speed of
computation while patient is on treatment couch, full automation, user friendly access to insights if needed, and integration within
the Elekta ONE unified software experience.
Integrated into the online adaptive radiotherapy process, the system is able to import and calculate 3D dose distributions in the
variety of patient anatomical models encountered: original voxelized pCT, synthetic CT (generated by Machine Learning approach)
and simplified density-bulk contours.
Its compliance with AAPM Task Group 219 recommendations on “independent calculation-based dose/MU verification for IMRT”,
in particular algorithm independence, 3D dose calculation and comparison, and 90% (3% – 2mm) action levels and tolerances (user
defined parameters).
Its versatile design and central positioning into the ThinkQA wider architecture for Patient-QA tasks. The CCC engine serves not only
the Secondary Dose Check requirement, but also other key modules/functions of a comprehensive Patient-QA solution used from
pre-treatment stage throughout all treatment fractions, including delivery logfile-based checks and EPID-based in-vivo dose
verification.
About ThinkQA – (Edition 2) is CE marked as a class I medical device in Europe, under the new European Medical Device Regulation (EU)
2017/745. ThinkQA (Edition 2) is FDA 510(k) cleared as class II Medical Charged-Particle Radiation Therapy System. ThinkQA Secondary
Dose Check is seamlessly integrated into Elekta ONE® and exclusively distributed by Elekta.
About DOSIsoft – Founded in 2002, DOSIsoft designs, develops & delivers patient-specific imaging & dosimetry software solutions in
Radiation Oncology & Nuclear Medicine to improve cancer patient safety & treatment quality. More than 20 years of innovation and R&D
investments have led to world leading software used in over 600 hospital centres in 60 countries. Spin-off between Gustave Roussy and
Institut Curie, DOSIsoft constantly innovates in partnership with the major cancer institutes and research centres in the world. It is now
recognized as a key player in the dosimetry market. www.dosisoft.com