Wilko F A R Verbakel

• PhD, Ir, PDEng
• Amsterdam University Medical Center

Background and purpose Segmentation imperfections (noise) in radiotherapy organ-at-risk segmentation naturally arise from specialist experience and image quality. Using clinical contours can result in sub-optimal convolutional neural network (CNN) training and performance, but manual curation is costly. We address the impact of simulated and clinic...

Purpose In postoperative breast irradiation, changes in the breast contour and arm positioning can result in patient positioning errors and offline replanning. This can lead to increased treatment burden and strain on departmental logistics because of the need for additional cone beam computed tomography (CBCT) images or even a new radiation therap...

Purpose A three-dimensional deep generative adversarial network (GAN) was used to predict dose distributions for locally advanced head and neck cancer radiotherapy. Given the labor- and time-intensive nature of manual planning target volume (PTV) and organ-at-risk (OAR) segmentation, we investigated whether dose distributions could be predicted wit...

Background Radiotherapy (RT) is involved in about 50% of all cancer patients, making it a very important treatment modality. The most common type of RT is external beam RT, which consists of delivering the radiation to the tumor from outside the body. One novel treatment delivery method is volumetric modulated arc therapy (VMAT), where the gantry c...

Simple Summary Ultra-high dose-rate (UHDR) irradiation can lead to a FLASH-effect which reduces the biological effect on healthy tissue without affecting the dose to the tumor. UHDRs can currently be achieved using 250 MeV (transmission) proton beams. Up until now, suggested treatment sites potentially benefiting from a FLASH effect include, e.g.,...

Background Clinical data used to train deep learning models are often not clean data. They can contain imperfections in both the imaging data and the corresponding segmentations. Purpose This study investigates the influence of data imperfections on the performance of deep learning models for parotid gland segmentation. This was done in a controll...

Background and purpose: Standard palliative radiotherapy workflows involve waiting times or multiple clinic visits. We developed and implemented a rapid palliative workflow using diagnostic imaging (dCT) for pre-planning, with subsequent on-couch target and plan adaptation based on a synthetic computed tomography (CT) obtained from cone-beam CT im...

Purpose: Single-visit radiotherapy (RT) is beneficial for patients requiring pain control and can limit interruptions to systemic treatments. However, the requirement for a dedicated planning CT (pCT)-scan can result in treatment delays. We developed a workflow involving preplanning on available diagnostic CT (dCT) imaging, followed by online plan...

Depending on the clinical situation, different combinations of lymph node (LN) levels define the elective LN target volume in head-and-neck cancer (HNC) radiotherapy. The accurate auto-contouring of individual LN levels could reduce the burden and variability of manual segmentation and be used regardless of the primary tumor location. We evaluated...

Purpose/Objective(s) Standard workflows of radiotherapy for metastatic disease palliation often involve multiple clinic visits and (long) waiting times. Fast palliation completed during a single clinic visit can be achieved by omitting a treatment planning CT scan and using available diagnostic imaging for treatment planning. The use of a diagnosti...

Purpose/Objective(s) The sparing effect of ultrahigh dose rate (UHDR; FLASH) radiotherapy (RT) is not only interesting for organs at risk, but also for healthy tissue within the PTV. This makes whole breast irradiation (WBI) an attractive option for FLASH RT, as the entire (mostly healthy) breast is given the prescribed dose. We investigated whethe...

Purpose/Objective(s) SABR may improve survival in patients with oligometastases, but for some lesions, safe delivery of SABR may require a reduction in delivered dose or target coverage. This study assessed the association between target coverage compromise and oncologic and survival outcomes through a secondary analysis of the SABR-COMET Phase II...

The field of treatment planning has changed considerably since 2005. The current publication focusses on a department wide implementation of a TPS. New sections about education, information technology (IT) and updates/upgrades result from this wider focus. The general parts of this report apply to all treatment modalities. The specific parts, such...

Knowledge-based planning solutions have brought significant improvements in treatment planning. However, the performance of a proton-specific knowledge-based planning model in creating knowledge-based plans (KBPs) with beam angles differing from those used to train the model remains unexplored. We used a previously validated RapidPlanPT model and s...

Purpose: Research suggests that in addition to the dose-rate, a dose threshold is also important for the reduction in normal tissue toxicity with similar tumor control after ultrahigh dose-rate radiation therapy (UHDR-RT). In this analysis we aimed to identify factors that might limit the ability to achieve this "FLASH"-effect in a scenario attrac...

Background and purpose Selecting patients benefitting from proton therapy is laborious and subjective. We demonstrate a novel automated solution for creating high-quality knowledge-based plans (KBPs) using proton and photon beams to identify patients for proton treatment based on their normal tissue complication probabilities (NTCP). Methods and M...

Purpose: Stereotactic ablative radiotherapy (SABR) may improve survival in patients with oligometastases, but for some lesions, safe delivery of SABR may require a reduction in delivered dose or target coverage. This study assessed the association between target coverage compromise and oncologic and survival outcomes. Methods and Materials: Patient...

Purpose Lung stereotactic ablative body radiotherapy (SABR) is a radiation therapy success story with level 1 evidence demonstrating its efficacy. To provide real‐time respiratory motion management for lung SABR, several commercial and preclinical markerless lung target tracking (MLTT) approaches have been developed. However, these approaches have...

Concurrent chemoradiotherapy (cCRT) is the preferred treatment for stage III NSCLC because surgery containing multimodality treatment is often not appropriate. Alternatives, often for less fit patients, include sequential CRT and RT alone. Many reports describing the relationship between overall survival (OS), toxicity, and dosimetry are based on c...

Purpose/Objective(s) During stereotactic lung radiotherapy we want to monitor the target position to ensure it remains inside the planning target volume (PTV). This ensures accurate treatment delivery and may allow for margin reduction. Many LINAC systems have a kilo-voltage (kV) imaging system mounted orthogonally to the MV beam. This can acquire...

Background and purpose Positional verification during single fraction lung SBRT could increase confidence and reduce the chance of geographic miss. As planar 2DkV imaging during VMAT irradiation is already available on current linear accelerators, markerless tracking based on these images could offer widely available and low-cost verification. We e...

Background Treatment patterns in stage III non-small cell lung cancer (NSCLC) can vary considerably between countries. The PACIFIC trial reported improvements in progression-free and overall survival with adjuvant durvalumab after concurrent chemoradiotherapy (CCRT). We studied treatment decision-making by 3 Dutch regional thoracic multidisciplinar...

In the Netherlands, the model-based approach is used to identify patients with head and neck cancer who may benefit most from proton therapy in terms of prevention of late radiation-induced side effects in comparison with photon therapy. To this purpose, a National Indication Protocol Proton therapy for Head and Neck Cancer patients (NIPP-HNC) was...

Transmission beam (TB) proton therapy (PT) uses single, high energy beams with Bragg-peak behind the target, sharp penumbras and simplified planning/delivery. TB facilitates ultra-high dose-rates (UHDRs, e.g., ≥40 Gy/s), which is a requirement for the FLASH-effect. We investigated (1) plan quality for conventionally-fractionated head-and-neck cance...

Purpose/objective Accurate verification of tumor position during irradiation could reduce the probability of target miss. We investigated whether a commercial gantry mounted 2D kilo-voltage (kV) imaging system could be used for real-time 3D tumor tracking during volumetric modulated arc therapy (VMAT) stereotactic lung radiotherapy (SBRT). Markerle...

Purpose There is progressing evidence for the anti-cancer potential of the natural compound and dietary spice curcumin. Curcumin has been ascribed to be cytotoxic for various tumour cell types, to inhibit cell proliferation and to interfere with the cellular oxidant status. The compound has been notified as a therapeutic agent with radiosensitizing...

Introduction Contouring OARs remains a largely manual task, which is time-consuming and prone to variation. Deep learning-based delineation (DLD) shows promise both in terms of quality and speed, but it does not yet perform perfectly. Because of that, manual checking of DLD is still recommended. There are currently no commercial tools to focus atte...

Introduction Manual quality assurance (QA) of radiotherapy contours for clinical trials is time and labor intensive and subject to inter-observer variability. Therefore, we investigated whether deep-learning (DL) can provide an automated solution to salivary gland contour QA. Material and methods DL-models were trained to generate contours for par...

Background: Deep learning-based delineation of organs-at-risk for radiotherapy purposes has been investigated to reduce the time-intensiveness and inter-/intra-observer variability associated with manual delineation. We systematically evaluated ways to improve the performance and reliability of deep learning for organ-at-risk segmentation, with th...

OBJECTIVES - Treatment patterns in patients with stage III non-small cell lung cancer (NSCLC) vary considerably between countries, for reasons that are not well understood. We studied factors influencing treatment decision-making at thoracic multidisciplinary tumor boards (MDT’s) and outcome for patients treated between 2015-2017, at a regional ne...

Radiotherapy treatment planning studies significantly contribute to advances and improvements in radiation treatment of cancer patients. They are a pivotal step to support and facilitate the introduction of novel techniques into clinical practice, or as a first step before clinical trials can be carried out. There have been numerous examples publis...

Technical improvements in head and neck cancer radiotherapy over the last decade have resulted in substantial reductions in dose to organs-at-risk. For a mix of tumors, we saw less xerostomia moving from 3D-conformal to more advanced techniques. For oropharynx-only there were additional improvements, including in global quality-of-life and sticky s...

Purpose To present the radiotherapy quality assurance (RTQA) results from a prospective multicenter phase II randomized trial of short vs. protracted urethra-sparing stereotactic body radiotherapy (SBRT) for localized prostate cancer (PCa). Methods Between 2012 and 2015, 165 PCa patients from nine centers were randomized and treated with SBRT deli...

Radiation therapy is an important technique to treat cancer. Due to the high occupational risks involved, the process is subject to severe safety regulations and standards. However, these standards do not mandate the usage of a particular hazard analysis method. The de facto methods currently used are the reliability theory-based Fault Tree Analysi...

Background: Pre-clinical research into ultrahigh dose-rate (e.g. ≥40Gy/s) "FLASH"-radiotherapy suggests a decrease in side-effects compared to conventional irradiation, while maintaining tumor control. When FLASH is delivered using a scanning proton beam, tissue becomes subject to a spatially dependent range of dose-rates. This study systematicall...

Background and purpose: In 2017 the ACROP guideline on SBRT for peripherally located early stage NSCLC was published. Later that year ICRU-91 about prescribing, recording and reporting was published. The purpose of this study is to quantify the current variation in prescription practice in the institutions that contributed to the ACROP guideline a...

Purpose: To benchmark and improve, through means of a targeted intervention, the quality of intensity modulated radiation therapy treatment planning for locally advanced head and neck cancer (HNC) in the Netherlands. The short and long-term impact of this intervention was assessed. Methods and materials: A delineated computed tomography-scan of...

Purpose: Organ-at-risk (OAR) delineation is a key step in treatment planning but can be time consuming, resource intensive, subject to variability, and dependent on anatomical knowledge. We studied deep learning (DL) for automated delineation of multiple OARs; in addition to geometric evaluation, the dosimetric impact of using DL contours for trea...

Purpose Intensity-modulated proton therapy (IMPT) treatments are increasing, however, treatment planning remains complex and prone to variability. RapidPlanTMPT (Varian Medical Systems, Palo Alto, California, USA) is a pre-clinical, proton-specific, automated knowledge-based planning solution which could reduce variability and increase efficiency....

Following publication of the original article [1], the authors reported that one of the authors’ names was processed incorrectly.

Background: Radiotherapy treatment planning as an increasingly automated and knowledge-based planning has been shown to match and sometimes improve upon manual clinical plans, with increased consistency and efficiency. In this study, we benchmarked a novel prototype knowledge-based intensity-modulated proton therapy (IMPT) planning solution, agains...

Introduction: Radiotherapy treatment plan quality can influence clinical trial outcomes and general QA may not identify suboptimal organ-at-risk (OAR) sparing. We retrospectively performed patient-specific quality assurance (QA) of 100 head-and-neck cancer (HNC) plans from the EORTC-1219-DAHANCA-29 study. Materials and methods: A 177-patient Rap...

Background: Automated treatment planning and/or optimization systems (ATPS) are in the process of broad clinical implementation aiming at reducing inter-planner variability, reducing the planning time allocated for the optimization process and improving plan quality. Five different ATPS used clinically were evaluated for advanced head and neck can...

Purpose: Stereotactic ablative body radiotherapy (SABR) for lung tumors ≥5cm, can be associated with more toxicity. We investigated the relationship between dosimetry and toxicity and used a knowledge-based planning solution to retrospectively perform individualized treatment plan quality assurance (QA) with the aim of identifying where planning c...

Background and purpose: Central lung stereotactic body radiotherapy (SBRT) can cause proximal bronchial tree (PBT) toxicity. Information on PBT position relative to the high-dose could aid risk management. We investigated template matching + triangulation for high-frequency markerless 3D PBT position monitoring. Materials and methods: Kilovoltag...

Background: This is a dosimetric comparative study intended to establish appropriate low-to-intermediate dose-constraints for the rectal wall (Rwall) in the context of a randomized phase-II trial on urethra-sparing stereotactic body radiotherapy (SBRT) for prostate cancer. The effect of plan optimization on low-to-intermediate Rwall dose and the p...

Purpose: Four-dimensional (4D) cone-beam computed tomography (CBCT) of the lung is an effective tool for motion management in radiotherapy but presents a challenge because of slow gantry rotation times. Sorting the individual projections by breathing phase and using an established technique such as Feldkamp-Davis-Kress (FDK) to generate correspond...

Lung tumors treated in breath-hold are subject to inter- and intra-breath-hold variations, which makes tumor position monitoring during each breath-hold important. A markerless technique is desirable, but limited tumor visibility on kV images makes this challenging. We evaluated if template matching+triangulation of kV projection images acquired du...

Purpose To report our initial experience with on-line markerless 3D spine position monitoring. We used template matching + triangulation of fluoroscopic kV images acquired with the gantry-mounted imager during flattening filter free volumetric modulated arc spine stereotactic body radiation therapy (SBRT) delivery on a conventional linear accelerat...