| 1. |
- Carrapiço-Seabra, Carolina, et al.
(author)
-
Application of the ESHO-QA guidelines for determining the performance of the LCA superficial hyperthermia heating system
- 2023
-
In: International Journal of Hyperthermia. - 0265-6736 .- 1464-5157. ; 40:1
-
Journal article (peer-reviewed)abstract
- Purpose: This study aimed to assess the quality of the lucite cone applicator (LCA), the standard applicator for superficial hyperthermia at the Erasmus MC Cancer Institute, using the most recent quality assurance guidelines, thus verifying their feasibility. Materials and methods: The assessment was conducted on each of the six LCAs available for clinical treatments. The temperature distribution was evaluated using an infrared camera across different layers of a fat-muscle mimicking phantom. The maximum temperature increase, thermal effective penetration depth (TEPD), and thermal effective field size (TEFS) were used as quality metrics. The experimental results were validated through comparison with simulated results, using a canonical phantom model and a realistic phantom model segmented from CT imaging. Results: A maximum temperature increase above 6 °C at 2 cm depth in the fat-muscle phantom for all the experiments was found. A mean negative difference between simulated and experimental data was of 1.3 °C when using the canonical phantom model. This value decreased to a mean negative difference of 0.4 °C when using the realistic model. Simulated and measured TEPD showed good agreement for both in silico scenarios, while discrepancies were present for TEFS. Conclusions: The LCAs passed all QA guidelines requirements for superficial hyperthermia delivery when used singularly or in an array configuration. A further characterization of parameters such as antenna efficiency and heat transfer coefficients would be beneficial for translating experimental results to simulated values. Implementing the QA guidelines was time-consuming and demanding, requiring careful preparation and correct setup of antenna elements.
|
|
| 2. |
- de Lazzari, Mattia, 1996, et al.
(author)
-
Design and manufacture procedures of phantoms for hyperthermia QA guidelines
- 2023
-
In: 17th European Conference on Antennas and Propagation, EuCAP 2023.
-
Conference paper (peer-reviewed)abstract
- Clinical outcome of hyperthermia therapy (HT) is strongly correlated with the thermal dose delivered into the tumor. Achieving of prescribed temperature distribution within the target area should therefore the primary objective of any HT treatment. The Quality Assurance (QA) guidelines developed in past decennium by ESHO-TC establish the physical characterization and prescribe the safeguards to ensure that the clinically used equipment is capable of achieving adequate temperatures. The direct implementation of these guidelines is however limited by the lack of suitable phantom materials. To address this issue, we propose (i) a novel material to mimic fat tissue and (ii) a standardized phantom verification of phased array applicators for deep HT in Head and Neck (H&N) and extremities. In particular, (i) a fat-phantom composed of an ethylcellulose based oleogel exhibit equivalent dielectric and thermal properties with the required mechanical stability even at elevated temperatures, while (ii) the standardized phantom provides the means to capture the thermal profiles to evaluate the performance indicators in reproducible manner. Both phantoms thus bears a great potential for their extensive use in QA procedures.
|
|
| 3. |
- de Lazzari, Mattia, 1996, et al.
(author)
-
Ethylcellulose-stabilized fat-tissue phantom for quality assurance in clinical hyperthermia
- 2023
-
In: International Journal of Hyperthermia. - 0265-6736 .- 1464-5157. ; 40:1
-
Journal article (peer-reviewed)abstract
- Background: Phantoms accurately mimicking the electromagnetic and thermal properties of human tissues are essential for the development, characterization, and quality assurance (QA) of clinically used equipment for Hyperthermia Treatment (HT). Currently, a viable recipe for a fat equivalent phantom is not available, mainly due to challenges in the fabrication process and fast deterioration. Materials and methods: We propose to employ a glycerol-in-oil emulsion stabilized with ethylcellulose to develop a fat-mimicking material. The dielectric, rheological, and thermal properties of the phantom have been assessed by state-of-the-art measurement techniques. The full-size phantom was then verified in compliance with QA guidelines for superficial HT, both numerically and experimentally, considering the properties variability. Results: Dielectric and thermal properties were proven equivalent to fat tissue, with an acceptable variability, in the 8 MHz to 1 GHz range. The rheology measurements highlighted enhanced mechanical stability over a large temperature range. Both numerical and experimental evaluations proved the suitability of the phantom for QA procedures. The impact of the dielectric property variations on the temperature distribution has been numerically proven to be limited (around 5%), even if higher for capacitive devices (up to 20%). Conclusions: The proposed fat-mimicking phantom is a good candidate for hyperthermia technology assessment processes, adequately representing both dielectric and thermal properties of the human fat tissue while maintaining structural stability even at elevated temperatures. However, further experimental investigations on capacitive heating devices are necessary to better assess the impact of the low electrical conductivity values on the thermal distribution.
|
|
| 4. |
- de Lazzari, Mattia, 1996
(author)
-
Practical Implementation of Quality Assurance Guidelines for Hyperthermia Therapy
- 2023
-
Licentiate thesis (other academic/artistic)abstract
- Hyperthermia therapy (HT) has been proven to be a potent enhancer of chemotherapy and radiotherapy in numerous clinical trials. The effectiveness of HT is strictly dependent on the administered thermal dose, which, in turn, is dependent on the quality of the therapeutic heat applied to the patient. Quality Assurance (QA) protocols in HT exist to ensure that heating devices can consistently deliver controlled, reproducible, and high-quality treatments. The physical characterization of HT devices requires specific procedures and instrumentation as well as adequate tissue-mimicking phantoms to perform QA experimental procedures. However, the implementation of QA guidelines is hampered due to the unavailability of suitable phantom materials and limited equipment for the QA experimental evaluation. This work addresses these gaps by (i) proposing the design of tissue-mimicking materials for routine use in HT QA procedures and (ii) demonstrating the practical implementation of the latest QA guidelines for both superficial and deep HT. A novel fat-mimicking material was developed to mimic superficial fatty tissue. This fat phantom is based on an ethylcellulose stabilized glycerol in oil emulsion and is intended to be used in superficial HT QA procedures. Measured dielectric and thermal properties were consistent with fatty tissue properties, with an acceptable variability in most of the frequency range used in HT. This fat-mimicking material was then used in the experimental implementation of HT guidelines. The physical characterization of a superficial HT device (Lucite Cone Applicator, LCA) was conducted by assessing the quality metrics defined in the HT guidelines, demonstrating acceptable performance. These findings were further validated through computational studies. For deep HT, a comparative study engaged six HT centers across Europe to assess the performance of commonly used deep regional heating devices. Preliminary results in experimental phantoms showed a good performance in terms of device heating capability and steerability. This study provided practical insights into implementing QA guidelines involving phantom properties, experimental setup, temperature acquisition, and time constraints. We are positive this research will benefit the routine implementation of deep HT guidelines in a clinical setting.
|
|
| 5. |
- Visentin, Roberto, et al.
(author)
-
A Novel Method for Generation of in Silico Subjects with Type 2 Diabetes
- 2021
-
In: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. ; , s. 1380-1383
-
Conference paper (peer-reviewed)abstract
- A type 2 diabetes (T2D) simulator has been recently proposed for supporting drug development and treatment optimization. This tool consists of a physiological model of glucose/insulin/C-peptide dynamics and a virtual cohort of T2D subjects (i.e., random extractions of model parameterizations from a joint parameter distribution) well describing both average and variability realistic T2D dynamics. However, the state-of-art procedure to get a reliable virtual population requires some post-processing after subject extraction, in order to discard implausible behaviors. We propose an improved method for virtual subjects' generation to overcome this burdensome task. To do so, we first assessed a refined joint parameter distribution, from which extracting a number of subjects, greater than the target population size. Then, target-size subsets are undersampled from the large cohort. The final virtual population is selected among the subsets as the one maximizing the similarity with T2D data and model parameter distribution, by means of measurement' outcome metrics and Euclidian distance (Δ), respectively. In the final population, almost all the outcome metrics are statistically identical to the clinical counterparts (p-value>0.05) and model parameters' distribution differs by ~5-10% from that derived from data. The methodology described here is flexible, thus resulting suitable for different T2D stages and type 1 diabetes, as well.Clinical Relevance - A straightforward subjects' generation would ease the availability of tailored in silico trials for testing diabetes treatment in a specific population.
|
|
