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Introduction Hyperthermia efficacy depends on the temperatures achieved in the target area. Therefore, hyperthermia systems must deliver both controlled and conformal heating. This study presents a comprehensive multi-institutional quality assurance (QA) evaluation of deep hyperthermia devices.Methods Six European institutions equipped with BSD- Sigma 60 and Sigma Eye deep hyperthermia applicators participated in the study. Up to six measurements per applicator were performed in each institution. The thermal distribution in cylindrical homogeneous phantoms after 10 minutes of heating with a total power delivered of 1000 watts was assessed using the applicator’s integrated mapping thermometry system. Evaluated quality parameters included temperature increase, focus location, and focus symmetry.Results A total of 54 measurements were conducted, with 43 included in the analysis. All applicators, except one, achieved a temperature increase of 6 °C in 10 minutes. Central heating capabilities were demonstrated, with mean deviations from the intended location of −1.4 ± 1.6 cm for Sigma 60 and 1.5 ± 1.4 cm for Sigma Eye. Symmetry evaluations showed differences in radial temperature profiles of 6.2 ± 4.5 % for the Sigma 60 and 5.9 ± 4.4 % for the Sigma Eye. We propose minimum acceptable values for each quality parameter based on these results.Conclusion The measurements were reproducible with acceptable values for the various quality parameters. Potential deviations might be attributed to inaccuracies in the mapping thermometry system rather than the heating system. The presented protocol and practical recommendations should be applied for future QA measurements in deep hyperthermia.

Introduction: The objective of this work is to design a new kind of AHFP phantom to determine if this phantom is a realistic representation of actual cervical cancer patients. This can serve as a stand-in for the dosimetry quality assurance of a real patient. Material and Methods: An anthropomorphic heterogeneous female pelvic phantom was designed which was made of paraffin wax, a female pelvic bone, water, gauze, polyvinyl chloride (PVC) and polymerized siloxanes. The AHFP phantom was scanned using a CT scanner (Toshiba Alexion 16 multi–Slice CT scanner) at 120kVp and 250mAs with a slice thickness of 2mm to assess how accurately the resulting phantom product simulates a real patient. The CT images were transferred to the Eclipse treatment planning system for dosimetry analysis. Results: The AHFP phantom's CT numbers and relative electron densities of the uterus, bladder, rectum, muscles, fat, bones, and cavities were found close to real patients. The mean percentage variations between planned and measured doses of all RapidArc QA plans were of 2.14 % and standard deviation of 0.543 (t=0.135, p= 0.447; p>0.05) for homogeneous phantom¸ and 7.57% & standard deviation 2.358 (t=4.674, p=0.00094; p< .05) for AHFP phantom. Conclusion: It is concluded that the existing algorithms in TPS for dosimetry are working fine for homogeneous phantoms, but it does not work good for heterogeneous (AHFP) phantom. Therefore, patient-specific absolute dosimetry should be performed using a heterogeneous phantom that closely resembles the actual human body in terms of both density and design.

Introduction: Hyperthermia efficacy depends on the temperatures achieved in the target area. Therefore, hyperthermia systems must deliver both controlled and conformal heating. This study presents a comprehensive multi-institutional quality assurance (QA) evaluation of deep hyperthermia devices. Methods: Six European institutions equipped with BSD- Sigma 60 and Sigma Eye deep hyperthermia applicators participated in the study. Up to six measurements per applicator were performed in each institution. The thermal distribution in cylindrical homogeneous phantoms after 10 minutes of heating with a total power delivered of 1000 watts was assessed using the applicator's integrated mapping thermometry system. Evaluated quality parameters included temperature increase, focus location, and focus symmetry. Results: A total of 54 measurements were conducted, with 43 included in the analysis. All applicators, except one, achieved a temperature increase of 6 °C in 10 minutes. Central heating capabilities were demonstrated, with mean deviations from the intended location of −1.4 ± 1.6 cm for Sigma 60 and 1.5 ± 1.4 cm for Sigma Eye. Symmetry evaluations showed differences in radial temperature profiles of 6.2 ± 4.5 % for the Sigma 60 and 5.9 ± 4.4 % for the Sigma Eye. We propose minimum acceptable values for each quality parameter based on these results. Conclusion: The measurements were reproducible with acceptable values for the various quality parameters. Potential deviations might be attributed to inaccuracies in the mapping thermometry system rather than the heating system. The presented protocol and practical recommendations should be applied for future QA measurements in deep hyperthermia. [ABSTRACT FROM AUTHOR]

Introduction: The objective of this work is to design a new kind of AHFP phantom to determine if this phantom is a realistic representation of actual cervical cancer patients. This can serve as a stand-in for the dosimetry quality assurance of a real patient. Material and Methods: An anthropomorphic heterogeneous female pelvic phantom was designed which was made of paraffin wax, a female pelvic bone, water, gauze, polyvinyl chloride (PVC) and polymerized siloxanes. The AHFP phantom was scanned using a CT scanner (Toshiba Alexion 16 multi-Slice CT scanner) at 120kVp and 250mAs with a slice thickness of 2mm to assess how accurately the resulting phantom product simulates a real patient. The CT images were transferred to the Eclipse treatment planning system for dosimetry analysis. Results: The AHFP phantom's CT numbers and relative electron densities of the uterus, bladder, rectum, muscles, fat, bones, and cavities were found close to real patients. The mean percentage variations between planned and measured doses of all RapidArc QA plans were of 2.14 % and standard deviation of 0.543 (t=0.135, p= 0.447; p>0.05) for homogeneous phantom, and 7.57% & standard deviation 2.358 (t=4.674, p=0.00094; p< .05) for AHFP phantom. Conclusion: It is concluded that the existing algorithms in TPS for dosimetry are working fine for homogeneous phantoms, but it does not work good for heterogeneous (AHFP) phantom. Therefore, patientspecific absolute dosimetry should be performed using a heterogeneous phantom that closely resembles the actual human body in terms of both density and design. [ABSTRACT FROM AUTHOR]

Background: Accurate dosimetry is crucial in radiotherapy to ensure optimal radiation dose delivery to the tumor while sparing healthy tissues. Traditional dosimetry techniques using homogeneous phantoms may not accurately represent the complex anatomical variations in cervical cancer patients, highlighting the need to compare dosimetry results obtained from different phantom models. Purpose: The aim of this study is to design and evaluate an anthropomorphic heterogeneous female pelvic (AHFP) phantom for radiotherapy quality assurance in cervical cancer treatment. Materials and method: Thirty RapidArc plans designed for cervical cancer patients were exported to both the RW3 homogeneous phantom and the anthropomorphic heterogeneous pelvic phantom. Dose calculations were performed using the anisotropic analytic algorithm (AAA), and the plans were delivered using a linear accelerator (LA). Dose measurements were obtained using a 0.6 cc ion chamber. The percentage (%) variation between planned and measured doses was calculated and analyzed. Additionally, relative dosimetry was performed for various target locations using RapidArc and IMRT treatment techniques. The AHFP phantom demonstrated excellent agreement between measured and expected dose distributions, making it a reliable quality assurance tool in radiotherapy. Results: The results reveal that the percentage variation between planned and measured doses for all RapidArc quality assurance (QA) plans using the AHFP phantom is 10.67% (maximum value), 2.31% (minimum value), and 6.89% (average value), with a standard deviation (SD) of 2.565 (t = 3.21604, p = 0.001063). Also, for the percentage of variation between homogeneous and AHFP phantoms, the t-value is −11.17016 and the p-value is <0.00001. The result is thus significant at p < 0.05. We can see that the outcomes differ significantly due to the influence of heterogeneous media. Also, the average gamma values in RapidArc plans are 0.29, 0.32, and 0.35 (g ≤ 1) and IMRT plans are 0.45, 0.44, and 0.42 (g ≤ 1) for targets 1, 2, and 3, respectively. Conclusion: The AHFP phantom results show more dose variability than homogenous phantom outcomes. Also, the AHFP phantom was found to be suitable for QA evaluation. [ABSTRACT FROM AUTHOR]

Background: Accurate dosimetry is crucial in radiotherapy to ensure optimal radiation dose delivery to the tumor while sparing healthy tissues. Traditional dosimetry techniques using homogeneous phantoms may not accurately represent the complex anatomical variations in cervical cancer patients, highlighting the need to compare dosimetry results obtained from different phantom models. Purpose: The aim of this study is to design and evaluate an anthropomorphic heterogeneous female pelvic (AHFP) phantom for radiotherapy quality assurance in cervical cancer treatment. Materials and method: Thirty RapidArc plans designed for cervical cancer patients were exported to both the RW3 homogeneous phantom and the anthropomorphic heterogeneous pelvic phantom. Dose calculations were performed using the anisotropic analytic algorithm (AAA), and the plans were delivered using a linear accelerator (LA). Dose measurements were obtained using a 0.6 cc ion chamber. The percentage (%) variation between planned and measured doses was calculated and analyzed. Additionally, relative dosimetry was performed for various target locations using RapidArc and IMRT treatment techniques. The AHFP phantom demonstrated excellent agreement between measured and expected dose distributions, making it a reliable quality assurance tool in radiotherapy. Results: The results reveal that the percentage variation between planned and measured doses for all RapidArc quality assurance (QA) plans using the AHFP phantom is 10.67% (maximum value), 2.31% (minimum value), and 6.89% (average value), with a standard deviation (SD) of 2.565 (t = 3.21604, p = 0.001063). Also, for the percentage of variation between homogeneous and AHFP phantoms, the t-value is −11.17016 and the p-value is p < 0.05. We can see that the outcomes differ significantly due to the influence of heterogeneous media. Also, the average gamma values in RapidArc plans are 0.29, 0.32, and 0.35 (g ≤ 1) and IMRT plans are 0.45, 0.44, and 0.42 (g ≤ 1) for targets 1, 2, and 3, respectively. Conclusion: The AHFP phantom results show more dose variability than homogenous phantom outcomes. Also, the AHFP phantom was found to be suitable for QA evaluation.

BackgroundThe development and clinical adoption of quantitative imaging biomarkers (radiomics) has established the need for the identification of parameters altering radiomics reproducibility. The aim of this study was to assess the impact of magnetic field strength on magnetic resonance imaging (MRI) radiomics features in neuroradiology clinical practice.MethodsT1 3D SPGR sequence was acquired on two phantoms and 10 healthy volunteers with two clinical MR devices from the same manufacturer using two different magnetic fields (1.5 and 3T). Phantoms varied in terms of gadolinium concentrations and textural heterogeneity. 27 regions of interest were segmented (phantom: 21, volunteers: 6) using the LIFEX software. 34 features were analyzed.ResultsIn the phantom dataset, 10 (67%) out of 15 radiomics features were significantly different when measured at 1.5T or 3T (student’s t-test, p < 0.05). Gray levels resampling, and pixel size also influence part of texture features. These findings were validated in healthy volunteers.ConclusionsAccording to daily used protocols for clinical examinations, radiomic features extracted on 1.5T should not be used interchangeably with 3T when evaluating texture features. Such confounding factor should be adjusted when adapting the results of a study to a different platform, or when designing a multicentric trial.

Background: The development and clinical adoption of quantitative imaging biomarkers (radiomics) has established the need for the identification of parameters altering radiomics reproducibility. The aim of this study was to assess the impact of magnetic field strength on magnetic resonance imaging (MRI) radiomics features in neuroradiology clinical practice. Methods: T1 3D SPGR sequence was acquired on two phantoms and 10 healthy volunteers with two clinical MR devices from the same manufacturer using two different magnetic fields (1.5 and 3T). Phantoms varied in terms of gadolinium concentrations and textural heterogeneity. 27 regions of interest were segmented (phantom: 21, volunteers: 6) using the LIFEX software. 34 features were analyzed. Results: In the phantom dataset, 10 (67%) out of 15 radiomics features were significantly different when measured at 1.5T or 3T (student's t-test, p < 0.05). Gray levels resampling, and pixel size also influence part of texture features. These findings were validated in healthy volunteers. Conclusions: According to daily used protocols for clinical examinations, radiomic features extracted on 1.5T should not be used interchangeably with 3T when evaluating texture features. Such confounding factor should be adjusted when adapting the results of a study to a different platform, or when designing a multicentric trial. [ABSTRACT FROM AUTHOR]

Abtract: We present the construction of a homogeneous phantom to be used in simulating the scattering and absorption of X-rays by a standard patient chest and skull when irradiated laterally. This phantom consisted of lucite and aluminium plates with their thickness determined by a tomographic exploratory method applied to the anthropomorphic phantom. Using this phantom, an optimized radiographic technique was established for chest and skull of standard sized patient in lateral view. Images generated with this optimized technique demonstrated improved image quality and reduced radiation doses. [Copyright &y& Elsevier]