Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2022.07.004
Giulio Rossi , Thomas Failing , Mark Gainey , Michael Kollefrath , Frank Hensley , Klemens Zink , Dimos Baltas
Purpose: To employ the microDiamond and the microSilicon detector (mDD and mSD, both PTW-Freiburg, Germany) to determine the dose rate around a HDR 192Ir brachytherapy source (model mHDR-v2r, Elekta AB, Sweden).
Methods: The detectors were calibrated with a 60Co beam at the PTW Calibration Laboratory. Measurements around the 192Ir source were performed inside a PTW MP3 water phantom. The detectors were placed at selected points of measurement at radial distances r, ranging from 0.5 to 10 cm, keeping the polar angle θ = 90°. Additional measurements were performed with the mSD at fixed distances r = 1, 3 and 5 cm, with θ varying from 0 to 150°, 0 to 166°, and 0 to 168°, respectively. The corresponding mDD readings were already available from a previous work (Rossi et al., 2020). The beam quality correction factor of both detectors, as well as a phantom effect correction factor to account for the difference between the experimental geometry and that assumed in the TG-43 formalism, were determined using the Monte Carlo (MC) toolkit EGSnrc. The beam quality correction factor was factorized into energy dependence and volume-averaging correction factors. Using the abovementioned MC-based factors, the dose rate to water at the different points of measurement in TG-43 conditions was obtained from the measured readings, and was compared to the dose rate calculated according to the TG-43 formalism.
Results: The beam quality correction factor was considerably closer to unity for the mDD than for the mSD. The energy dependence of the mDD showed a very weak radial dependence, similar to the previous findings showing a weak angular dependence as well (Rossi et al., 2020). Conversely, the energy dependence of the mSD decreased significantly with increasing distances, and also showed a considerably more pronounced angular dependence, especially for the smallest angles. The volume-averaging showed a similar radial dependence for both detectors: the correction had a maximal impact at 0.5 cm and then approached unity for larger distances, as expected. Concerning the angular dependence, the correction for the mSD was also similar to the one previously determined for the mDD (Rossi et al., 2020): a maximal impact was observed at θ = 0°, with values tending to unity for larger angles. In general, the volume-averaging was less pronounced for the mSD due to the smaller sensitive volume radius. After the application of the MC-based factors, differences between mDD dose rate measurements and TG-43 dose rate calculations ranged from −2.6% to +4.3%, with an absolute average difference of 1.0%. For the mSD, the differences ranged from −3.1% to +5.2%, with an absolute average difference of 1.0%. For both detectors, all differences but one were within the combined uncertainty (k = 2). The differences of the mSD from the mD
{"title":"Determination of the dose rate around a HDR 192Ir brachytherapy source with the microDiamond and the microSilicon detector","authors":"Giulio Rossi , Thomas Failing , Mark Gainey , Michael Kollefrath , Frank Hensley , Klemens Zink , Dimos Baltas","doi":"10.1016/j.zemedi.2022.07.004","DOIUrl":"10.1016/j.zemedi.2022.07.004","url":null,"abstract":"<div><p><strong>Purpose:</strong> To employ the microDiamond and the microSilicon detector (mDD and mSD, both PTW-Freiburg, Germany) to determine the dose rate around a HDR <sup>192</sup>Ir brachytherapy source (model mHDR-v2r, Elekta AB, Sweden).</p><p><strong>Methods:</strong> The detectors were calibrated with a <sup>60</sup>Co beam at the PTW Calibration Laboratory. Measurements around the <sup>192</sup>Ir source were performed inside a PTW MP3 water phantom. The detectors were placed at selected points of measurement at radial distances <em>r</em>, ranging from 0.5 to 10 cm, keeping the polar angle <em>θ</em> = 90°. Additional measurements were performed with the mSD at fixed distances <em>r</em> = 1, 3 and 5 cm, with <em>θ</em> varying from 0 to 150°, 0 to 166°, and 0 to 168°, respectively. The corresponding mDD readings were already available from a previous work (Rossi et al., 2020). The beam quality correction factor of both detectors, as well as a phantom effect correction factor to account for the difference between the experimental geometry and that assumed in the TG-43 formalism, were determined using the Monte Carlo (MC) toolkit EGSnrc. The beam quality correction factor was factorized into energy dependence and volume-averaging correction factors. Using the abovementioned MC-based factors, the dose rate to water at the different points of measurement in TG-43 conditions was obtained from the measured readings, and was compared to the dose rate calculated according to the TG-43 formalism.</p><p><strong>Results:</strong> The beam quality correction factor was considerably closer to unity for the mDD than for the mSD. The energy dependence of the mDD showed a very weak radial dependence, similar to the previous findings showing a weak angular dependence as well (Rossi et al., 2020). Conversely, the energy dependence of the mSD decreased significantly with increasing distances, and also showed a considerably more pronounced angular dependence, especially for the smallest angles. The volume-averaging showed a similar radial dependence for both detectors: the correction had a maximal impact at 0.5 cm and then approached unity for larger distances, as expected. Concerning the angular dependence, the correction for the mSD was also similar to the one previously determined for the mDD (Rossi et al., 2020): a maximal impact was observed at <em>θ</em> = 0°, with values tending to unity for larger angles. In general, the volume-averaging was less pronounced for the mSD due to the smaller sensitive volume radius. After the application of the MC-based factors, differences between mDD dose rate measurements and TG-43 dose rate calculations ranged from −2.6% to +4.3%, with an absolute average difference of 1.0%. For the mSD, the differences ranged from −3.1% to +5.2%, with an absolute average difference of 1.0%. For both detectors, all differences but one were within the combined uncertainty (<em>k</em> = 2). The differences of the mSD from the mD","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000861/pdfft?md5=757a0dfeacd000a7b89d5837c4d2acf5&pid=1-s2.0-S0939388922000861-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33446157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2022.10.002
Monika Clausen , Sirinya Ruangchan , Arame Sotoudegan , Andreas F. Resch , Barbara Knäusl , Hugo Palmans , Dietmar Georg
Purpose
To evaluate the dosimetric accuracy for small field proton irradiation relevant for pre-clinical in vivo studies using clinical infrastructure and technology. In this context additional beam collimation and range reduction was implemented.
Methods and materials
The clinical proton beam line employing pencil beam scanning (PBS) was adapted for the irradiation of small fields at shallow depths. Cylindrical collimators with apertures of 15, 12, 7 and 5 mm as well as two different range shifter types, placed at different distances relative to the target, were tested: a bolus range shifter (BRS) attached to the collimator and a clinical nozzle mounted range shifter (CRS) placed at a distance of 72 cm from the collimator. The Monte Carlo (MC) based dose calculation engine implemented in the clinical treatment planning system (TPS) was commissioned for these two additional hardware components. The study was conducted with a phantom and cylindrical target sizes between 2 and 25 mm in diameter following a dosimetric end-to-end test concept.
Results
The setup with the CRS provided a uniform dose distribution across the target. An agreement of better than 5% between the planned dose and the measurements was obtained for a target with 3 mm diameter (collimator 5 mm). A 2 mm difference between the collimator and the target diameter (target being 2 mm smaller than the collimator) sufficed to cover the whole target with the planned dose in the setup with CRS. Using the BRS setup (target 8 mm, collimator 12 mm) resulted in non-homogeneous dose distributions, with a dose discrepancy of up to 10% between the planned and measured doses.
Conclusion
The clinical proton infrastructure with adequate beam line adaptations and a state-of-the-art TPS based on MC dose calculations enables small animal irradiations with a high dosimetric precision and accuracy for target sizes down to 3 mm.
{"title":"Small field proton irradiation for in vivo studies: Potential and limitations when adapting clinical infrastructure","authors":"Monika Clausen , Sirinya Ruangchan , Arame Sotoudegan , Andreas F. Resch , Barbara Knäusl , Hugo Palmans , Dietmar Georg","doi":"10.1016/j.zemedi.2022.10.002","DOIUrl":"10.1016/j.zemedi.2022.10.002","url":null,"abstract":"<div><h3>Purpose</h3><p>To evaluate the dosimetric accuracy for small field proton irradiation relevant for pre-clinical in vivo studies using clinical infrastructure and technology. In this context additional beam collimation and range reduction was implemented.</p></div><div><h3>Methods and materials</h3><p>The clinical proton beam line employing pencil beam scanning (PBS) was adapted for the irradiation of small fields at shallow depths. Cylindrical collimators with apertures of 15, 12, 7 and 5<!--> <!-->mm as well as two different range shifter types, placed at different distances relative to the target, were tested: a bolus range shifter (BRS) attached to the collimator and a clinical nozzle mounted range shifter (CRS) placed at a distance of 72<!--> <!-->cm from the collimator. The Monte Carlo (MC) based dose calculation engine implemented in the clinical treatment planning system (TPS) was commissioned for these two additional hardware components. The study was conducted with a phantom and cylindrical target sizes between 2 and 25<!--> <!-->mm in diameter following a dosimetric end-to-end test concept.</p></div><div><h3>Results</h3><p>The setup with the CRS provided a uniform dose distribution across the target. An agreement of better than<!--> <!-->5% between the planned dose and the measurements was obtained for a target with 3<!--> <!-->mm diameter (collimator 5<!--> <!-->mm). A 2<!--> <!-->mm difference between the collimator and the target diameter (target being 2 mm smaller than the collimator) sufficed to cover the whole target with the planned dose in the setup with CRS. Using the BRS setup (target 8<!--> <!-->mm, collimator 12<!--> <!-->mm) resulted in non-homogeneous dose distributions, with a dose discrepancy of up to 10% between the planned and measured doses.</p></div><div><h3>Conclusion</h3><p>The clinical proton infrastructure with adequate beam line adaptations and a state-of-the-art TPS based on MC dose calculations enables small animal irradiations with a high dosimetric precision and accuracy for target sizes down to 3<!--> <!-->mm.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000964/pdfft?md5=6a2d36ebbbded4eb6aae93b1b6f13bbe&pid=1-s2.0-S0939388922000964-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40675960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2022.10.008
Ali Asadi , Azadeh Akhavanallaf , Seyed Abolfazl Hosseini , Naser Vosoughi , Habib Zaidi
Objective
To develop and validate a versatile Monte Carlo (MC)-based dose calculation engine to support MC-based dose verification of treatment planning systems (TPSs) and quality assurance (QA) workflows in proton therapy.
Methods
The GATE MC toolkit was used to simulate a fixed horizontal active scan-based proton beam delivery (SIEMENS IONTRIS). Within the nozzle, two primary and secondary dose monitors have been designed to enable the comparison of the accuracy of dose estimation from MC simulations with respect to physical QA measurements. The developed beam model was validated against a series of commissioning measurements using pinpoint chambers and 2D array ionization chambers (IC) in terms of lateral profiles and depth dose distributions. Furthermore, beam delivery module and treatment planning has been validated against the literature deploying various clinical test cases of the AAPM TG‐119 (c-shape phantom) and a prostate patient.
Results
MC simulations showed excellent agreement with measurements in the lateral depth-dose parameters and spread-out Bragg peak (SOBP) characteristics within a maximum relative error of 0.95 mm in range, 1.83% in entrance to peak ratio, 0.27% in mean point-to-point dose difference, and 0.32% in peak location. The mean relative absolute difference between MC simulations and measurements in terms of absorbed dose in the SOBP region was 0.93% ± 0.88%. Clinical phantom studies showed a good agreement compared to research TPS (relative error for TG-119 planning target volume PTV-D95 ∼ 1.8%; and for prostate PTV-D95 ∼ −0.6%).
Conclusion
We successfully developed a MC model for the pencil beam scanning system, which appears reliable for dose verification of the TPS in combination with QA information, prior to patient treatment.
{"title":"Development and validation of an optimal GATE model for proton pencil-beam scanning delivery","authors":"Ali Asadi , Azadeh Akhavanallaf , Seyed Abolfazl Hosseini , Naser Vosoughi , Habib Zaidi","doi":"10.1016/j.zemedi.2022.10.008","DOIUrl":"10.1016/j.zemedi.2022.10.008","url":null,"abstract":"<div><h3>Objective</h3><p>To develop and validate a versatile Monte Carlo (MC)-based dose calculation engine to support MC-based dose verification of treatment planning systems (TPSs) and quality assurance (QA) workflows in proton therapy.</p></div><div><h3>Methods</h3><p>The GATE MC toolkit was used to simulate a fixed horizontal active scan-based proton beam delivery (SIEMENS IONTRIS). Within the nozzle, two primary and secondary dose monitors have been designed to enable the comparison of the accuracy of dose estimation from MC simulations with respect to physical QA measurements. The developed beam model was validated against a series of commissioning measurements using pinpoint chambers and 2D array ionization chambers (IC) in terms of lateral profiles and depth dose distributions. Furthermore, beam delivery module and treatment planning has been validated against the literature deploying various clinical test cases of the AAPM TG‐119 (c-shape phantom) and a prostate patient.</p></div><div><h3>Results</h3><p>MC simulations showed excellent agreement with measurements in the lateral depth-dose parameters and spread-out Bragg peak (SOBP) characteristics within a maximum relative error of 0.95 mm in range, 1.83% in entrance to peak ratio, 0.27% in mean point-to-point dose difference, and 0.32% in peak location. The mean relative absolute difference between MC simulations and measurements in terms of absorbed dose in the SOBP region was 0.93% ± 0.88%. Clinical phantom studies showed a good agreement compared to research TPS (relative error for TG-119 planning target volume PTV-D<sub>95</sub> ∼ 1.8%; and for prostate PTV-D<sub>95</sub> ∼ −0.6%).</p></div><div><h3>Conclusion</h3><p>We successfully developed a MC model for the pencil beam scanning system, which appears reliable for dose verification of the TPS in combination with QA information, prior to patient treatment.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922001027/pdfft?md5=ee47ca179f730456d33ac76196b166f2&pid=1-s2.0-S0939388922001027-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40705419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2023.02.002
Hans Lynggaard Riis , Rasmus Lübeck Christiansen , Nina Tilly , David Tilly
Purpose
The precision of the dose delivery in radiation therapy with high-field MR-linacs is challenging due to the substantial variation in the beam attenuation of the patient positioning system (PPS) (the couch and coils) as a function of the gantry angle. This work aimed to compare the attenuation of two PPSs located at two different MR-linac sites through measurements and calculations in the treatment planning system (TPS).
Methods
Attenuation measurements were performed at every 1° gantry angle at the two sites with a cylindrical water phantom with a Farmer chamber inserted along the rotational axis of the phantom. The phantom was positioned with the chamber reference point (CRP) at the MR-linac isocentre. A compensation strategy was applied to minimise sinusoidal measurement errors due to, e.g. air cavity or setup. A series of tests were performed to assess the sensitivity to measurement uncertainties. The dose to a model of the cylindrical water phantom with the PPS added was calculated in the TPS (Monaco v5.4 as well as in a development version Dev of an upcoming release), for the same gantry angles as for the measurements. The TPS PPS model dependency of the dose calculation voxelisation resolution was also investigated.
Results
A comparison of the measured attenuation of the two PPSs yielded differences of less than 0.5% for most gantry angles. The maximum deviation between the attenuation measurements for the two different PPSs exceeded ±1% at two specific gantry angles 115° and 245°, where the beam traverses the most complex PPS structures. The attenuation increases from 0% to 25% in 15° intervals around these angles. The measured and calculated attenuation, as calculated in v5.4, was generally within 1-2% with a systematic overestimation of the attenuation for gantry angles around 180°, as well as a maximum error of 4-5% for a few discrete angles in 10° gantry angle intervals around the complex PPS structures. The PPS modelling was improved compared to v5.4 in Dev, especially around 180°, and the results of those calculations were within ±1%, but with a similar 4% maximum deviation for the most complex PPS structures.
Conclusions
Generally, the two tested PPS structures exhibit very similar attenuation as a function of the gantry angle, including the angles with a steep change in attenuation. Both TPS versions, v5.4 and Dev delivered clinically acceptable accuracy of the calculated dose, as the differences in the measurements were overall better than ±2%. Additionally, Dev improved the accuracy of the dose calculation to ±1% for gantry angles around 180°.
{"title":"Dosimetric validation of the couch and coil model for high-field MR-linac treatment planning","authors":"Hans Lynggaard Riis , Rasmus Lübeck Christiansen , Nina Tilly , David Tilly","doi":"10.1016/j.zemedi.2023.02.002","DOIUrl":"10.1016/j.zemedi.2023.02.002","url":null,"abstract":"<div><h3>Purpose</h3><p>The precision of the dose delivery in radiation therapy with high-field MR-linacs is challenging due to the substantial variation in the beam attenuation of the patient positioning system (PPS) (the couch and coils) as a function of the gantry angle. This work aimed to compare the attenuation of two PPSs located at two different MR-linac sites through measurements and calculations in the treatment planning system (TPS).</p></div><div><h3>Methods</h3><p>Attenuation measurements were performed at every 1° gantry angle at the two sites with a cylindrical water phantom with a Farmer chamber inserted along the rotational axis of the phantom. The phantom was positioned with the chamber reference point (CRP) at the MR-linac isocentre. A compensation strategy was applied to minimise sinusoidal measurement errors due to, e.g. air cavity or setup. A series of tests were performed to assess the sensitivity to measurement uncertainties. The dose to a model of the cylindrical water phantom with the PPS added was calculated in the TPS (Monaco v5.4 as well as in a development version Dev of an upcoming release), for the same gantry angles as for the measurements. The TPS PPS model dependency of the dose calculation voxelisation resolution was also investigated.</p></div><div><h3>Results</h3><p>A comparison of the measured attenuation of the two PPSs yielded differences of less than 0.5% for most gantry angles. The maximum deviation between the attenuation measurements for the two different PPSs exceeded ±1% at two specific gantry angles 115° and 245°, where the beam traverses the most complex PPS structures. The attenuation increases from 0% to 25% in 15° intervals around these angles. The measured and calculated attenuation, as calculated in v5.4, was generally within 1-2% with a systematic overestimation of the attenuation for gantry angles around 180°, as well as a maximum error of 4-5% for a few discrete angles in 10° gantry angle intervals around the complex PPS structures. The PPS modelling was improved compared to v5.4 in Dev, especially around 180°, and the results of those calculations were within ±1%, but with a similar 4% maximum deviation for the most complex PPS structures.</p></div><div><h3>Conclusions</h3><p>Generally, the two tested PPS structures exhibit very similar attenuation as a function of the gantry angle, including the angles with a steep change in attenuation. Both TPS versions, v5.4 and Dev delivered clinically acceptable accuracy of the calculated dose, as the differences in the measurements were overall better than ±2%. Additionally, Dev improved the accuracy of the dose calculation to ±1% for gantry angles around 180°.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923000107/pdfft?md5=b803cbed8da14be6fd6496a875e50cdc&pid=1-s2.0-S0939388923000107-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9209877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2023.09.002
Mark E. Ladd
{"title":"The Medical Device Regulation and its impact on device development and research in Germany","authors":"Mark E. Ladd","doi":"10.1016/j.zemedi.2023.09.002","DOIUrl":"10.1016/j.zemedi.2023.09.002","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923001149/pdfft?md5=2ec676734624e9c1443edac357f21c0f&pid=1-s2.0-S0939388923001149-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49687314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2022.11.011
Fabian Kugel , Jörg Wulff , Christian Bäumer , Martin Janson , Jana Kretschmer , Leonie Brodbek , Carina Behrends , Nico Verbeek , Hui Khee Looe , Björn Poppe , Beate Timmermann
Purpose
The primary fluence of a proton pencil beam exiting the accelerator is enveloped by a region of secondaries, commonly called “spray”. Although small in magnitude, this spray may affect dose distributions in pencil beam scanning mode e.g., in the calculation of the small field output, if not modelled properly in a treatment planning system (TPS). The purpose of this study was to dosimetrically benchmark the Monte Carlo (MC) dose engine of the RayStation TPS (v.10A) in small proton fields and systematically compare single Gaussian (SG) and double Gaussian (DG) modeling of initial proton fluence providing a more accurate representation of the nozzle spray.
Methods
The initial proton fluence distribution for SG/DG beam modeling was deduced from two-dimensional measurements in air with a scintillation screen with electronic readout. The DG model was either based on direct fits of the two Gaussians to the measured profiles, or by an iterative optimization procedure, which uses the measured profiles to mimic in-air scan-field factor (SF) measurements. To validate the DG beam models SFs, i.e. relative doses to a 10 × 10 cm2 field, were measured in water for three different initial proton energies (, , ) and square field sizes from to using a small field ionization chamber (IBA CC01) and an IBA ProteusPlus system (universal nozzle). Furthermore, the dose to the center of spherical target volumes (diameters: to ) was determined using the same small volume ionization chamber (IC). A comprehensive uncertainty analysis was performed, including estimates of influence factors typical for small field dosimetry deduced from a simple two-dimensional analytical model of the relative fluence distribution. Measurements were compared to the predictions of the RayStation TPS.
Results
SFs deviated by more than from TPS predictions in all fields
{"title":"Validating a double Gaussian source model for small proton fields in a commercial Monte-Carlo dose calculation engine","authors":"Fabian Kugel , Jörg Wulff , Christian Bäumer , Martin Janson , Jana Kretschmer , Leonie Brodbek , Carina Behrends , Nico Verbeek , Hui Khee Looe , Björn Poppe , Beate Timmermann","doi":"10.1016/j.zemedi.2022.11.011","DOIUrl":"10.1016/j.zemedi.2022.11.011","url":null,"abstract":"<div><h3>Purpose</h3><p>The primary fluence of a proton pencil beam exiting the accelerator is enveloped by a region of secondaries, commonly called “spray”. Although small in magnitude, this spray may affect dose distributions in pencil beam scanning mode e.g., in the calculation of the small field output, if not modelled properly in a treatment planning system (TPS). The purpose of this study was to dosimetrically benchmark the Monte Carlo (MC) dose engine of the RayStation TPS (v.10A) in small proton fields and systematically compare single Gaussian (SG) and double Gaussian (DG) modeling of initial proton fluence providing a more accurate representation of the nozzle spray.</p></div><div><h3>Methods</h3><p>The initial proton fluence distribution for SG/DG beam modeling was deduced from two-dimensional measurements in air with a scintillation screen with electronic readout. The DG model was either based on direct fits of the two Gaussians to the measured profiles, or by an iterative optimization procedure, which uses the measured profiles to mimic in-air scan-field factor (SF) measurements. To validate the DG beam models SFs, i.e. relative doses to a 10 × 10 cm<sup>2</sup> field, were measured in water for three different initial proton energies (<span><math><mrow><mn>100</mn><mspace></mspace><mspace></mspace><mi>M</mi><mi>e</mi><mi>V</mi></mrow></math></span>, <span><math><mrow><mn>160</mn><mspace></mspace><mspace></mspace><mi>M</mi><mi>e</mi><mi>V</mi></mrow></math></span>, <span><math><mrow><mn>226.7</mn><mspace></mspace><mspace></mspace><mi>M</mi><mi>e</mi><mi>V</mi></mrow></math></span>) and square field sizes from <span><math><mrow><mn>1</mn><mspace></mspace><mo>×</mo><mn>1</mn><mspace></mspace><mspace></mspace><msup><mrow><mi>c</mi><mi>m</mi></mrow><mn>2</mn></msup></mrow></math></span> to <span><math><mrow><mn>10</mn><mspace></mspace><mo>×</mo><mn>10</mn><mspace></mspace><mspace></mspace><msup><mrow><mi>c</mi><mi>m</mi></mrow><mn>2</mn></msup></mrow></math></span> using a small field ionization chamber (IBA CC01) and an IBA ProteusPlus system (universal nozzle). Furthermore, the dose to the center of spherical target volumes (diameters: <span><math><mrow><mn>1</mn><mspace></mspace><mspace></mspace><mi>c</mi><mi>m</mi></mrow></math></span> to <span><math><mrow><mn>10</mn><mspace></mspace><mspace></mspace><mi>c</mi><mi>m</mi></mrow></math></span>) was determined using the same small volume ionization chamber (IC). A comprehensive uncertainty analysis was performed, including estimates of influence factors typical for small field dosimetry deduced from a simple two-dimensional analytical model of the relative fluence distribution. Measurements were compared to the predictions of the RayStation TPS.</p></div><div><h3>Results</h3><p>SFs deviated by more than <span><math><mrow><mn>2</mn><mspace></mspace><mo>%</mo></mrow></math></span> from TPS predictions in all fields <span><math><mrow><mo><</mo><mn>4</mn><mspace></mspace><mo>×</mo><mn>4<","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922001325/pdfft?md5=acc41f4e71e3b623bcf07aca85ececd9&pid=1-s2.0-S0939388922001325-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10447935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2022.08.001
Xuanyu Zhu, Yang Gao, Feng Liu, Stuart Crozier, Hongfu Sun
Introduction
Background field removal (BFR) is a critical step required for successful quantitative susceptibility mapping (QSM). However, eliminating the background field in brains containing significant susceptibility sources, such as intracranial hemorrhages, is challenging due to the relatively large scale of the field induced by these pathological susceptibility sources.
Method
This study proposes a new deep learning-based method, BFRnet, to remove the background field in healthy and hemorrhagic subjects. The network is built with the dual-frequency octave convolutions on the U-net architecture, trained with synthetic field maps containing significant susceptibility sources. The BFRnet method is compared with three conventional BFR methods and one previous deep learning method using simulated and in vivo brains from 4 healthy and 2 hemorrhagic subjects. Robustness against acquisition field-of-view (FOV) orientation and brain masking are also investigated.
Results
For both simulation and in vivo experiments, BFRnet led to the best visually appealing results in the local field and QSM results with the minimum contrast loss and the most accurate hemorrhage susceptibility measurements among all five methods. In addition, BFRnet produced the most consistent local field and susceptibility maps between different sizes of brain masks, while conventional methods depend drastically on precise brain extraction and further brain edge erosions. It is also observed that BFRnet performed the best among all BFR methods for acquisition FOVs oblique to the main magnetic field.
Conclusion
The proposed BFRnet improved the accuracy of local field reconstruction in the hemorrhagic subjects compared with conventional BFR algorithms. The BFRnet method was effective for acquisitions of tilted orientations and retained whole brains without edge erosion as often required by traditional BFR methods.
{"title":"BFRnet: A deep learning-based MR background field removal method for QSM of the brain containing significant pathological susceptibility sources","authors":"Xuanyu Zhu, Yang Gao, Feng Liu, Stuart Crozier, Hongfu Sun","doi":"10.1016/j.zemedi.2022.08.001","DOIUrl":"10.1016/j.zemedi.2022.08.001","url":null,"abstract":"<div><h3>Introduction</h3><p>Background field removal (BFR) is a critical step required for successful quantitative susceptibility mapping (QSM). However, eliminating the background field in brains containing significant susceptibility sources, such as intracranial hemorrhages, is challenging due to the relatively large scale of the field induced by these pathological susceptibility sources.</p></div><div><h3>Method</h3><p>This study proposes a new deep learning-based method, BFRnet, to remove the background field in healthy and hemorrhagic subjects. The network is built with the dual-frequency octave convolutions on the U-net architecture, trained with synthetic field maps containing significant susceptibility sources. The BFRnet method is compared with three conventional BFR methods and one previous deep learning method using simulated and <em>in vivo</em> brains from 4 healthy and 2 hemorrhagic subjects. Robustness against acquisition field-of-view (FOV) orientation and brain masking are also investigated.</p></div><div><h3>Results</h3><p>For both simulation and <em>in vivo</em> experiments, BFRnet led to the best visually appealing results in the local field and QSM results with the minimum contrast loss and the most accurate hemorrhage susceptibility measurements among all five methods. In addition, BFRnet produced the most consistent local field and susceptibility maps between different sizes of brain masks, while conventional methods depend drastically on precise brain extraction and further brain edge erosions. It is also observed that BFRnet performed the best among all BFR methods for acquisition FOVs oblique to the main magnetic field.</p></div><div><h3>Conclusion</h3><p>The proposed BFRnet improved the accuracy of local field reconstruction in the hemorrhagic subjects compared with conventional BFR algorithms. The BFRnet method was effective for acquisitions of tilted orientations and retained whole brains without edge erosion as often required by traditional BFR methods.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000873/pdfft?md5=a43396a30e379e50097e3a5a3e24b83c&pid=1-s2.0-S0939388922000873-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40351533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2022.11.002
Sandra Oliver , Vicent Giménez-Alventosa , Francisco Berumen , Vicente Gimenez , Luc Beaulieu , Facundo Ballester , Javier Vijande
Purpose
The purpose of this study is to validate the PenRed Monte Carlo framework for clinical applications in brachytherapy. PenRed is a C++ version of Penelope Monte Carlo code with additional tallies and utilities.
Methods and materials
Six benchmarking scenarios are explored to validate the use of PenRed and its improved bachytherapy-oriented capabilities for HDR brachytherapy. A new tally allowing the evaluation of collisional kerma for any material using the track length kerma estimator and the possibility to obtain the seed positions, weights and directions processing directly the DICOM file are now implemented in the PenRed distribution. The four non-clinical test cases developed by the Joint AAPM-ESTRO-ABG-ABS WG-DCAB were evaluated by comparing local and global absorbed dose differences with respect to established reference datasets. A prostate and a palliative lung cases, were also studied. For them, absorbed dose ratios, global absorbed dose differences, and cumulative dose-volume histograms were obtained and discussed.
Results
The air-kerma strength and the dose rate constant corresponding to the two sources agree with the reference datatests within 0.3% () and 0.1% (. With respect to the first three WG-DCAB test cases, more than 99.8% of the voxels present local (global) differences within () of the reference datasets. For test Case 4 reference dataset, more than 94.9%(97.5%) of voxels show an agreement within (), better than similar benchmarking calculations in the literature. The track length kerma estimator scorer implemented increases the numerical efficiency of brachytherapy calculations two orders of magnitude, while the specific brachytherapy source allows the user to avoid the use of error-prone intermediate steps to translate the DICOM information into the simulation. In both clinical cases, only minor absorbed dose differences arise in the low-dose isodoses. 99.8% and 100% of the voxels have a global absorbed dose difference ratio within for the prostate and lung cases, respectively. The role played by the different segmentation and composition material in the bone structures was discussed, obtaining negligible absorbed dose differences. Dose-volume histograms were in agreement with the reference data.
Conclusions
PenRed incorporates new tallies and utilities and has been validated for its use for detailed and precise high-dose-rate b
{"title":"Benchmark of the PenRed Monte Carlo framework for HDR brachytherapy","authors":"Sandra Oliver , Vicent Giménez-Alventosa , Francisco Berumen , Vicente Gimenez , Luc Beaulieu , Facundo Ballester , Javier Vijande","doi":"10.1016/j.zemedi.2022.11.002","DOIUrl":"10.1016/j.zemedi.2022.11.002","url":null,"abstract":"<div><h3>Purpose</h3><p>The purpose of this study is to validate the PenRed Monte Carlo framework for clinical applications in brachytherapy. PenRed is a C++ version of Penelope Monte Carlo code with additional tallies and utilities.</p></div><div><h3>Methods and materials</h3><p>Six benchmarking scenarios are explored to validate the use of PenRed and its improved bachytherapy-oriented capabilities for HDR brachytherapy. A new tally allowing the evaluation of collisional kerma for any material using the track length kerma estimator and the possibility to obtain the seed positions, weights and directions processing directly the DICOM file are now implemented in the PenRed distribution. The four non-clinical test cases developed by the Joint AAPM-ESTRO-ABG-ABS WG-DCAB were evaluated by comparing local and global absorbed dose differences with respect to established reference datasets. A prostate and a palliative lung cases, were also studied. For them, absorbed dose ratios, global absorbed dose differences, and cumulative dose-volume histograms were obtained and discussed.</p></div><div><h3>Results</h3><p>The air-kerma strength and the dose rate constant corresponding to the two sources agree with the reference datatests within 0.3% (<span><math><mrow><msub><mrow><mi>S</mi></mrow><mrow><mi>k</mi></mrow></msub></mrow></math></span>) and 0.1% (<span><math><mrow><mi>Λ</mi><mo>)</mo></mrow></math></span>. With respect to the first three WG-DCAB test cases, more than 99.8% of the voxels present local (global) differences within <span><math><mrow><mo>±</mo><mn>1</mn><mo>%</mo></mrow></math></span>(<span><math><mrow><mo>±</mo><mn>0.1</mn><mo>%</mo></mrow></math></span>) of the reference datasets. For test Case 4 reference dataset, more than 94.9%(97.5%) of voxels show an agreement within <span><math><mrow><mo>±</mo><mn>1</mn><mo>%</mo></mrow></math></span>(<span><math><mrow><mo>±</mo><mn>0.1</mn><mo>%</mo></mrow></math></span>), better than similar benchmarking calculations in the literature. The track length kerma estimator scorer implemented increases the numerical efficiency of brachytherapy calculations two orders of magnitude, while the specific brachytherapy source allows the user to avoid the use of error-prone intermediate steps to translate the DICOM information into the simulation. In both clinical cases, only minor absorbed dose differences arise in the low-dose isodoses. 99.8% and 100% of the voxels have a global absorbed dose difference ratio within <span><math><mrow><mo>±</mo><mn>0.2</mn><mo>%</mo></mrow></math></span> for the prostate and lung cases, respectively. The role played by the different segmentation and composition material in the bone structures was discussed, obtaining negligible absorbed dose differences. Dose-volume histograms were in agreement with the reference data.</p></div><div><h3>Conclusions</h3><p>PenRed incorporates new tallies and utilities and has been validated for its use for detailed and precise high-dose-rate b","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922001040/pdfft?md5=c747742a19f7b02d767f19528d0430ad&pid=1-s2.0-S0939388922001040-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10333707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2022.08.006
Daniel Lohmann, Maya Shariff, Philipp Schubert, Tim Oliver Sauer, Rainer Fietkau, Christoph Bert
Purpose
The increasing complexity of new treatment methods as well as the Information Technology (IT) infrastructure within radiotherapy require new methods for risk analysis. This work presents a methodology on how to model the treatment process of radiotherapy in different levels. This subdivision makes it possible to perform workflow-specific risk analysis and to assess the impact of IT risks on the overall treatment workflow.
Methods
A Unified Modeling Language (UML) activity diagram is used to model the workflows. The subdivision of the workflows into different levels is done with the help of swim lanes. The model created in this way is exported in an xml-compatible format and stored in a database with the help of a Python program.
Results
Based on an existing risk analysis, the workflows CT Appointment, Glioblastoma Multiforme, and Deep Inspiration Breath Hold (DIBH) were modeled in detail. Part of the analysis are automatically generated workflow-specific risk matrices including risks of medical devices incorporated into a specific workflow. In addition, SQL queries allow to quickly retrieve e.g., the details of the medical device network installed in a department.
Conclusion
Activity diagrams of UML can be used to model workflows in radiotherapy. Through this, a connection between the different levels of the entire workflow can be established and workflow-specific risk analysis is possible.
{"title":"Unified risk analysis in radiation therapy","authors":"Daniel Lohmann, Maya Shariff, Philipp Schubert, Tim Oliver Sauer, Rainer Fietkau, Christoph Bert","doi":"10.1016/j.zemedi.2022.08.006","DOIUrl":"10.1016/j.zemedi.2022.08.006","url":null,"abstract":"<div><h3>Purpose</h3><p>The increasing complexity of new treatment methods as well as the Information Technology (IT) infrastructure within radiotherapy require new methods for risk analysis. This work presents a methodology on how to model the treatment process of radiotherapy in different levels. This subdivision makes it possible to perform workflow-specific risk analysis and to assess the impact of IT risks on the overall treatment workflow.</p></div><div><h3>Methods</h3><p>A Unified Modeling Language (UML) activity diagram is used to model the workflows. The subdivision of the workflows into different levels is done with the help of swim lanes. The model created in this way is exported in an xml-compatible format and stored in a database with the help of a Python program.</p></div><div><h3>Results</h3><p>Based on an existing risk analysis, the workflows CT Appointment, Glioblastoma Multiforme, and Deep Inspiration Breath Hold (DIBH) were modeled in detail. Part of the analysis are automatically generated workflow-specific risk matrices including risks of medical devices incorporated into a specific workflow. In addition, SQL queries allow to quickly retrieve e.g., the details of the medical device network installed in a department.</p></div><div><h3>Conclusion</h3><p>Activity diagrams of UML can be used to model workflows in radiotherapy. Through this, a connection between the different levels of the entire workflow can be established and workflow-specific risk analysis is possible.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000927/pdfft?md5=ba80fcde953fca3d36d229a6788bd796&pid=1-s2.0-S0939388922000927-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33494623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1016/j.zemedi.2022.08.005
Stefanie Kaser , Thomas Bergauer , Ander Biguri , Wolfgang Birkfellner , Sepideh Hatamikia , Albert Hirtl , Christian Irmler , Benjamin Kirchmayer , Felix Ulrich-Pur
Proton irradiation is a well-established method to treat deep-seated tumors in radio oncology. Usually, an X-ray computed tomography (CT) scan is used for treatment planning. Since proton therapy is based on the precise knowledge of the stopping power describing the energy loss of protons in the patient tissues, the Hounsfield units of the planning CT have to be converted. This conversion introduces range errors in the treatment plan, which could be reduced, if the stopping power values were extracted directly from an image obtained using protons instead of X-rays. Since protons are affected by multiple Coulomb scattering, reconstruction of the 3D stopping power map results in limited image quality if the curved proton path is not considered. This work presents a substantial code extension of the open-source toolbox TIGRE for proton CT (pCT) image reconstruction based on proton radiographs including a curved proton path estimate. The code extension and the reconstruction algorithms are GPU-based, allowing to achieve reconstruction results within minutes. The performance of the pCT code extension was tested with Monte Carlo simulated data using three phantoms (Catphan® high resolution and sensitometry modules and a CIRS patient phantom). In the simulations, ideal and non-ideal conditions for a pCT setup were assumed. The obtained mean absolute percentage error was found to be below 1% and up to 8 lp/cm could be resolved using an idealized setup. These findings demonstrate that the presented code extension to the TIGRE toolbox offers the possibility for other research groups to use a fast and accurate open-source pCT reconstruction.
{"title":"Extension of the open-source TIGRE toolbox for proton imaging","authors":"Stefanie Kaser , Thomas Bergauer , Ander Biguri , Wolfgang Birkfellner , Sepideh Hatamikia , Albert Hirtl , Christian Irmler , Benjamin Kirchmayer , Felix Ulrich-Pur","doi":"10.1016/j.zemedi.2022.08.005","DOIUrl":"10.1016/j.zemedi.2022.08.005","url":null,"abstract":"<div><p>Proton irradiation is a well-established method to treat deep-seated tumors in radio oncology. Usually, an X-ray computed tomography (CT) scan is used for treatment planning. Since proton therapy is based on the precise knowledge of the stopping power describing the energy loss of protons in the patient tissues, the Hounsfield units of the planning CT have to be converted. This conversion introduces range errors in the treatment plan, which could be reduced, if the stopping power values were extracted directly from an image obtained using protons instead of X-rays. Since protons are affected by multiple Coulomb scattering, reconstruction of the 3D stopping power map results in limited image quality if the curved proton path is not considered. This work presents a substantial code extension of the open-source toolbox TIGRE for proton CT (pCT) image reconstruction based on proton radiographs including a curved proton path estimate. The code extension and the reconstruction algorithms are GPU-based, allowing to achieve reconstruction results within minutes. The performance of the pCT code extension was tested with Monte Carlo simulated data using three phantoms (Catphan® high resolution and sensitometry modules and a CIRS patient phantom). In the simulations, ideal and non-ideal conditions for a pCT setup were assumed. The obtained mean absolute percentage error was found to be below 1% and up to 8 lp/cm could be resolved using an idealized setup. These findings demonstrate that the presented code extension to the TIGRE toolbox offers the possibility for other research groups to use a fast and accurate open-source pCT reconstruction.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000915/pdfft?md5=46269dbaf9848d6120a6ee0827c92f50&pid=1-s2.0-S0939388922000915-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33487328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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