M.M. Paulides

Electromagnetic redesign of the HYPERcollar applicator: toward improved deep local head-and-neck hyperthermia

Accumulating evidence shows that hyperthermia improves head-and-neck cancer treatment. Over the last decade, we introduced a radiofrequency applicator, named HYPERcollar, which enables local heating also of deep locations in this region. Based on clinical experience, we redesigned the HYPERcollar for improved comfort, reproducibility and operator handling. In the current study, we analyze the redesign from an electromagnetic point of view. We show that a higher number of antennas and their repositioning allow for a substantially improved treatment quality. Combined with the much better reproducibility of the water bolus, this will substantially minimize the risk of underexposure. All improvements combined enable a reduction of hot-spot prominence (hot-spot to target SAR quotient) by 32% at an average of 981xa0W, which drastically reduces the probability for system power to become a treatment limiting source. Moreover, the power deposited in the target selectively can be increased by more than twofold. Hence, we expect that the HYPERcollar redesign currently under construction allows us to double the clinically applied power to the target while reducing the hot-spots, resulting in higher temperatures and, consequently, better clinical outcome.

OC-0335: Feasibility of deep head and neck hyperthermia

necrosis – 74,5% in 6 months observation time for each: HDRBT and PDR-BT method in h/n. Serious late side-effects were seen in two patients (9%) l/t and PDR-BT group. Conclusions: 1. HDR and PDR both had similar percentages of side effects. 2. Early complications due to the total radiation dose are frequent and needs to be treated by intensive pharmacology. 3. HDR or PDR are effective tools in tumor recurrence radiation treatment, when surgical procedure is impossible and using another EBRT schedule very dangerous for the patient. 4. Future studies should aim to determine the maximum tolerated dose and appropriate patient selection.

Intrasubject multimodal groupwise registration with the conditional template entropy

HIGHLIGHTSA novel similarity metric for multimodal groupwise registration is proposed.The proposed method showed equivalent or improved registration accuracy.Pairwise mutual information is outperformed in terms of transitivity. ABSTRACT Image registration is an important task in medical image analysis. Whereas most methods are designed for the registration of two images (pairwise registration), there is an increasing interest in simultaneously aligning more than two images using groupwise registration. Multimodal registration in a groupwise setting remains difficult, due to the lack of generally applicable similarity metrics. In this work, a novel similarity metric for such groupwise registration problems is proposed. The metric calculates the sum of the conditional entropy between each image in the group and a representative template image constructed iteratively using principal component analysis. The proposed metric is validated in extensive experiments on synthetic and intrasubject clinical image data. These experiments showed equivalent or improved registration accuracy compared to other state‐of‐the‐art (dis)similarity metrics and improved transformation consistency compared to pairwise mutual information.

PD-0524: Visualization tool for Electromagnetic Dosimetry and Optimization (VEDO) during deep hyperthermia

Results: The maximum doses (in EQD2) for different critical organs in the H&N case are presented in Table 1, along with doses calculated without deformable registration or compensation for biological dose effects. For medulla, deformable EQD2 values are approximately 10% less than for the rigid raw sum; for other organs the difference varies from 0 to 8%. Conclusions: Considerations of dose to organs at risk may be a limiting factor for treatment planning of secondary malignancies at the same site. This work has shown a complete framework to examine re-treatment planning accounting for different patient positions, dose sizes and fractionation schemes of new and previous treatments. This accurate summed EQD2 distribution is helpful in seeing which dose tolerances are reached, and where the treatment plan could be modified further.

PO-0647: Target-selective radio-sensitization in head and neck tumors by the novel HYPERcollar3D hyperthermia applicator

Purpose/Objective: Current treatment of advanced cancer of the head and neck is unsatisfactory in terms of outcome and the toxicity of current treatments are severe. Phase III clinical trials have shown that hyperthermia (heating in the range of 40-44°C for one hour) is a potent sensitizing agent of radiotherapy, which is achieved without additional toxicity [1-3]. To enable heat-sensitization also in target regions at deep locations, we developed the HYPERcollar and showed in 45 patients that inducing hyperthermia in tumors located deeply and laterally in the head and neck region is feasible and has potential. Over the years, we further introduced an adaptive hyperthermia strategy based on electromagnetic field simulations. In this study, we analyze the HYPERcollar3D that is a redesigned version of the HYPERcollar aimed at improving heating quality, heating reproducibility and patient comfort. Materials and Methods: In the HYPERcollar3D, patient comfort and treatment accuracy/stability are improved by splitting the waterbolus functions into a stable outer part and a patient conformal inner part. Patient positioning according to the CT resembles that of radiotherapy and is obtained by immobilization and a laser alignment procedure. Based on a mechanical redesign, we performed parameter studies using electromagnetic simulator SEMCAD-X (v. 14.8.6) to investigate further improvement by increasing the number of antennas and their locations.

Benefit of replacing the Sigma-60 by the Sigma-Eye applicator@@@Vorteil des Ersatzes des Sigma-60- durch den Sigma-Eye-Applikator: A Monte Carlo-based uncertainty analysis@@@Eine Monte-Carlo-basierte Unsicherheitsanalyse

Background and purposeTo investigate the clinical benefit of replacing the BSD-2000 Sigma-60 with the Sigma-Eye applicator, taking into account effects of uncertainties in tissue and water bolus parameters.Patients and methodsFor 20 patients, specific absorption rate (SAR) and temperature distributions were calculated and optimized, based on computed tomography (CT) scans in treatment position. The impact of uncertainties on predicted distributions was studied using a Monte Carlo uncertainty assessment.ResultsReplacing the Sigma-60 by the Sigma-Eye applicator resulted in a higher SAR in the tumor [on average a decrease of the hotspot tumor quotient (HTQ) by 24%; pu2009<u20090.001], and higher temperatures (T90: +0.4°C, pu2009<u20090.001; T50: +0.6°C, pu2009<u20090.001) using literature values and SAR optimization. When temperature optimization (T90) was used, a larger average increase was found (T90: +0.7°C, pu2009<u20090.001; T50: +0.8°C, pu2009<u20090.001). When taking into account uncertainties, a decrease of 23% in median HTQ (pu2009<u20090.001) and an increase in T50 and T90 of 0.4°C (pu2009<u20090.001) could be demonstrated.ConclusionBased on this uncertainty analysis, significant and clinically relevant improvements in HTQ and tumor temperature were achieved when replacing the Sigma-60 by the Sigma-Eye applicator.ZusammenfassungZielUntersuchung des Ersatzes des Sigma-60-Applikators des BSD-2000-Hyperthermiesystems durch den Sigma-Eye-Applikator, unter Berücksichtigung der Auswirkungen der Unsicherheiten in den Gewebeparametern.MethodeModelle von 20 Patienten wurden aus den CT-Scans in Behandlungsposition erstellt und für die Berechnung und Optimierung von spezifischen Absorptionsraten(SAR)- und Temperaturverteilungen verwendet. Die klinische Relevanz von Unsicherheiten wurde mithilfe der Monte-Carlo-Methode ausgiebig untersucht.ErgebnisseDer Ersatz des Sigma-60 durch den Sigma-Eye führt zu erhöhten SAR-Werten im Tumor [durchschnittliche Verbesserung der HTQ um 24% (pu2009<u20090,001)] und zu erhöhten Temperaturen (T90: +0,4°C, pu2009<u20090,001; T50: +0,6°C, pu2009<u20090,001). Durch Verwendung der Temperaturoptimierung (T90) wird eine größere Zunahme festgestellt (T90: +u20090,7°C, pu2009<u20090,001; T50: +u20090,8°C, pu2009<u20090,001). Wenn die Unsicherheiten berücksichtigt werden, ergibt sich eine Verbesserung der mittleren HTQ um 23% (pu2009<u20090,001) und eine Erhöhung der mittleren T50 und T90 um 0,4°C (pu2009<u20090,001).SchlussfolgerungAuf Basis einer Unsicherheitsanalyse ergibt sich eine signifikante und klinisch relevante Verbesserung der Tumor-SAR und der Tumortemperatur, wenn der Sigma-60- durch den Sigma-Eye-Applikator ersetzt wird.

EP-1502 CLINICAL INTRODUCTION OF TREATMENT PLANNING GUIDED HYPERTHERMIA: A COMPLAINT ADAPTIVE APPROACH

complication probabilities (NTCP) increasing and probability (TCP) decreasing]. A comparison between ERR optimised new plans was performed in term of indexes. Results: The values for the breast ERR index are graphed in real time at each iteration cycle of t process, as shown in figure # 1. Preliminary resu advantages in terms of plans at lower risk of cancer the real-time OBE tool is introduced into the optimiza minimizing the ERR values. For the five patients analyz ERR values decreased by an average of 25% (σ= significant variations in TCP (<1%) and NTCP (<1% observed.

Latest advances in EM hyperthermia cancer treatments

Investigations have been carried out to determine the limitations of currently used technology in the field of hyperthermia cancer treatment. A novel hyperthermia treatment planning tool and a new head&neck applicator have been developed. The treatment planning tool is optimized for high quality, accurate, realistic simulations of highly detailed models. The applicator offers superior steerability and online control.