Introduction: The Erasmus MC and TU Delft started the ARCHITECT project to develop a personalized applicator design approach for performing brachytherapy in patients with cervical cancer.
Workflow for executing brachytherapy differs a lot between institutions.
An overview of the workflow was created and time analysis of the steps was performed to identify bottlenecks and points of improvement in the current clinical practice of brachytherapy in cervical cancer. This overview could also be used as a reference for future research.
Methods: An overview of the workflow was created, the time needed for the different steps was registered and patients were asked to fill out questionnaires on patient experience. The current clinical practice was observed to create the workflow overview and define the steps of which time should be registered. As some steps occurred in parallel the radiotherapy technicians, radiation oncologists and nurses were asked to assist in reporting of times. Matlab was used to calculate the duration of the steps and SPSS was used to determine the descriptive statistics.
The research protocol written for the patient experience study was approved but the medical ethics committee. Patients were informed on the study so they could provide informed consent.
The EQ-5D questionnaire was used to asses initial pain, anxiety and quality of life. A questionnaire on pain, anxiety and duration of each step during treatment day that was used for evaluating patient experience.
Result: A workflow overview per location was created. Data of forty implantations in fifteen patients were included for time analysis. The general steps and mean time needed for these steps were: operating room (55 minutes), waiting before arrival at imaging (80 minutes), applicator reconstruction (57 minutes), contouring (50 minutes), treatment planning (50 minutes), clinical physicist check (22 minutes) and treatment room (41 minutes). The mean total procedure time from patient entering the operating room until leaving the treatment room was 391 minutes.
The time needed for implantation of subsequent treatment fractions compared to the first treatment fraction decreased in sixteen out of the twenty fractions. The time needed at the operating room in patients receiving spinal anesthesia did not differ from patients receiving general anesthesia.
Four patients provided informed consent and filled out the questionnaires on patient experience. Patient experience differed a lot in these four patients. Overall, highest anxiety scores were found during the first brachytherapy day and highest pain scores were found during the waiting time at the short stay unit.
Discussion: The steps observed in the Erasmus MC did not agree on all steps that were found in literature. Time needed for these steps also differed when comparing to literature. The total waiting time could be decreased when enabling a more smooth transition between the recovery room and imaging step.
Adaptions to the time registration sheet should include the time needed for assembling the applicator at the operating room. The contouring step should be separated in contouring of the OAR and target volume. Time needed for imaging is not that important as the imaging protocol is the same in all patients. The decrease in waiting time for imaging when using the hyperthermia MRI should be evaluated. The influence of the amount of patients treated during one day would also be interesting to evaluate when more data has been collected. Another interesting factor would be differences in duration of the steps and pain experienced in patients treated with the Venezia applicator compared to the Utrecht applicator. More patients need to be included in the questionnaire study to draw conclusions on patient experience.
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Introduction: High Dose Rate (HDR) Brachytherapy is a radiotherapy modality that involves temporarily introducing a highly radioactive source into the target volume with the use of an applicator. With respect to HDR brachytherapy for prostate cancer, an 192Iridium source is driven into the target volume through catheters implanted into the prostate. The dose delivered to a point in the prostate depends on the time the source dwells at a given position. Treatment planning for brachytherapy involve the optimization of dwell times and dwell positions. The aim of the treatment plan is to deliver the prescribed dose to the target volume, the prostate, while minimizing the dose to the organs at risk (OAR), namely the urethra, bladder and rectum. In current clinical practice, the process of treatment planning involves the manual manipulation of the parameters of an optimizer until the desired dose distribution is achieved. This implies that the plan quality depends on the experience of the planner, and there is variation in plan quality between planners. The aim of this project was to develop an automated treatment planning system that would able to generate clinically acceptable plans with minimal human intervention. The brachytherapy treatment planning module is named B-iCycle and may be integrated in the future with the treatment planning software suite, called Erasmus-iCycle, developed at the Erasmus MC.
Materials and methods: At the core of the treatment planning system (TPS) is a precise and fast dose engine that is able to simulate the dose to be delivered. In this project, we employ the TG-43 dose calculation formalism as it is the most widely implemented method in dose engines for brachytherapy treatment planning systems. The dose engine is then verified against the dose engine of the clinical treatment planning system. B-iCycle uses the 2-phase ϵ-constraint (2pϵc) algorithm to optimize the dwell times and positions. The 2pϵc algorithm requires a ‘wish-list’, which encapsulates the treatment protocol as goals and constraints for each critical structure. For this project three treatment protocols were chosen, four fractions of 9.5 Gy, single fraction of 19 Gy and single fraction of 20 Gy, and wish-lists were generated for each protocol. Three patient groups with different catheter geometries were selected. Treatment plans were generated for each patient and compared against the plans that were generated, for the same patients, in the clinic. The treatment plans that were generated in B-iCycle were then exported to the clinical treatment planning system (Oncentra from Elekta) to obtain the dose characteristics. The plans were compared based on the dose characteristics and the Conformity Index (COIN). The plans were also verified by a radiation oncologist.
Results: The TG-43 dose engine was successfully verified against the clinical dose engine. The Gamma analysis showed that only 0.68% of the voxels failed the gamma analysis and these voxels were located within the catheters therefore they can be ignored as no tissue lies at these positions. With regard to plans that were generated, the physician confirmed that the clinically acceptable B-iCycle plans are very comparable to the clinical plans. The B-iCycle plans are better at minimizing the dose to the urethra. When comparing B-iCycle plans to the clinical plans using COIN, B-iCycle was found to be better than the clinical procedure. B-iCycle can generate a treatment plan in approximately 10 seconds, which is much faster than the clinical procedure, which averages at 10 minutes. It is also able to avoid the issue of treatment planner variability and is able to generate consistent, high quality treatment plans.
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