Angular independent silicon detector for dosimetry in external beam radiotherapy

Petasecca, Marco; Alhujaili, S.; Aldosari, A. H.; Fuduli, Iolanda; Newall, Matthew; Porumb, C.; Carolan, Martin G; Nitschke, K; Lerch, Michael L. F; Kalliopuska, J.; Perevertaylo, Vladimir; Rosenfeld, Anatoly B.

doi:10.1118/1.4926778

Cited by 21 publications

(28 citation statements)

References 43 publications

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“…19,43 The Attix IC response shows a large over-response up to + 20% at AE60 degree as confirmed by other studies. 24 Skin dose increases also as a function of the field size and depends on WED of measurement. In this sense, the skin diode and Attix IC's response with field size are different because the WED of the IC is about 0.025 mm, in contrast to the WED of the skin diode, estimated to be approximately 0.075 mm.…”

Section: Discussionmentioning

confidence: 99%

Development of a silicon diode detector for skin dosimetry in radiotherapy

et al. 2017

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Purpose: The aim of in vivo skin dosimetry was to measure the absorbed dose to the skin during radiotherapy, when treatment planning calculations cannot be relied on. It is of particularly importance in hypo-fractionated stereotactic modalities, where excessive dose can lead to severe skin toxicity. Currently, commercial diodes for such applications are with water equivalent depths ranging from 0.5 to 0.8 mm. In this study, we investigate a new detector for skin dosimetry based on a silicon epitaxial diode, referred to as the skin diode. Method: The skin diode is manufactured on a thin epitaxial layer and packaged using the "drop-in" technology. It was characterized in terms of percentage depth dose, dose linearity, and dose rate dependence, and benchmarked against the Attix ionization chamber. The response of the skin diode in the build-up region of the percentage depth dose (PDD) curve of a 6 MV clinical photon beam was investigated. Geant4 radiation transport simulations were used to model the PDD in order to estimate the water equivalent measurement depth (WED) of the skin diode. Measured output factors using the skin diode were compared with the MOSkin detector and EBT3 film at 10 cm depth and at surface at isocenter of a water equivalent phantom. The intrinsic angular response of the skin diode was also quantified in charge particle equilibrium conditions (CPE) and at the surface of a solid water phantom. Finally, the radiation hardness of the skin diode up to an accumulated dose of 80 kGy using photons from a Co-60 gamma source was evaluated. Results: The PDD curve measured with the skin diode was within 0.5% agreement of the equivalent Geant4 simulated curve. When placed at the phantom surface, the WED of the skin diode was estimated to be 0.075 AE 0.005 mm from Geant4 simulations and was confirmed using the response of a corrected Attix ionization chamber placed at water equivalent depth of 0.075 mm, with the measurement agreement to within 0.3%. The output factor measurements at 10 cm depth were within 2% of those measured with film and the MOSkin detector down to a field size of 2 9 2 cm 2 . The dose-response for all detector samples was linear and with a repeatability within 0.2%. The skin diode intrinsic angular response showed a maximum deviation of 8% at 90 degrees and from 0 to 60 degree is less than 5%. The radiation sensitivity reduced by 25% after an accumulated dose of 20 kGy but after was found to stabilize. At 60 kGy total accumulated dose the response was within 2% of that measured at 20 kGy total accumulated dose. Conclusions: This work characterizes an innovative detector for in vivo and real-time skin dose measurements that is based on an epitaxial silicon diode combined with the Centre for Medical Radiation Physics (CMRP) "drop-in" packaging technology. The skin diode proved to have a water equivalent depth of measurement of 0.075 AE 0.005 mm and the ability to measure doses accurately relative to reference detectors.

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Section: Discussionmentioning

confidence: 99%

Development of a silicon diode detector for skin dosimetry in radiotherapy

et al. 2017

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“…Using different techniques can eliminate the angular dependence, such as adding half pipe‐shaped boluses, filling air gaps with sheets of lucite and pieces of copper, or by applying angular correction factors . Recently, edgeless diodes were developed which, combined with a special drop in packaging in kapton tails, avoided high Z overlayers, and demonstrated angular independence in MV photon field …”

Section: Introductionmentioning

confidence: 99%

“Characterization of ELEKTA SRS cone collimator using high spatial resolution monolithic silicon detector array”

shukaili

Corde

Petasecca

et al. 2018

J Applied Clin Med Phys

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PurposeTo investigate the accuracy of the dosimetry of radiation fields produced by small ELEKTA cone collimators used for stereotactic radiosurgery treatments (SRS) using commercially available detectors EBT3 GafchromicTM film, IBA Stereotactic diode (SFD), and the recently developed detector DUO, which is a monolithic silicon orthogonal linear diode array detector.MethodsThese three detectors were used for the measurement of beam profiles, output factors, and percentage depth dose for SRS cone collimators with cone sizes ranging from 5 to 50 mm diameter. The measurements were performed at 10 cm depth and 90 cm SSD.ResultsThe SRS cone beam profiles measured with DUO, EBT3 film, and IBA SFD agreed well, results being in agreement within ±0.5 mm in the FWHM, and ±0.7 mm in the penumbra region. The output factor measured by DUO with 0.5 mm air gap above agrees within ±1% with EBT3. The OF measured by IBA SFD (corrected for the over‐response) agreed with both EBT3 and DUO within ±2%. All three detectors agree within ±2% for PDD measurements for all SRS cones.ConclusionsThe characteristics of the ELEKTA SRS cone collimator have been evaluated by using a monolithic silicon high spatial resolution detector DUO, EBT3, and IBA SFD diode. The DUO detector is suitable for fast real‐time quality assurance dosimetry in small radiation fields typical for SRS/SRT. This has been demonstrated by its good agreement of measured doses with EBT 3 films.

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“…The angular dependence of silicon diodes results from their geometry and construction; directionality depends also on the energy of incident beam, field size, and the back scattering from the packaging material creating variations in sensitivity up to 25% with angle of incidence. 21 There have been several reported solutions to overcome detectors responses anisotropy. One solution has been introduced by Jursinc et al by adding a thin copper disk to the top side of the diode used in the MapCHECK device which has decreased the angular dependence from ±10% to ±1.25%.…”

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confidence: 99%

“…However, this solution increased the perturbation of radiation beam due to the addition of the copper material which makes the correction factors depend on the beam energy. 21,22 Westermark et al proposed another solution by coupling two diodes back-to-back similar to the approach used in MOSFETs. 12,23 The combination of two diodes is found to mitigate the angular dependence to just ±3%, but the double mass of the diodes makes this solution unsuitable for small field dosimetry due to a large beam perturbation.…”

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confidence: 99%

“…This fabrication technology has been developed by the VTT Technical Research Centre of Finland Micro and Nanoelectronics (Finland) within the framework of the international collaboration MEDIPIX, and its application in radiotherapy dosimetry, in combination with the "drop in" packaging technology, is proposed by CMRP. 21 The basic characterization of the edgeless detectors for dosimetry in external beam radiotherapy is described in Petasecca et al 21 The aim of this study was to evaluate the application of the angularly independent "edgeless" detectors as a QA tool for robotic SRS modalities such as Cyberknife ® by testing the diodes for routine dosimetric QA and by delivering three full patient plans to a lung phantom which is stationary or moving with a breathing pattern recorded from four-dimensional CT for the same patients. In this work, absolute and relative measurements including a field size factor, dose off-axis profiles, and tissue-phantom ratio (TPR) have been performed.…”

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confidence: 99%

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Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector

Alhujaili

Biasi

Alzorkany

et al. 2018

J Applied Clin Med Phys

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PurposeThe aim of this work was to evaluate the use of an angularly independent silicon detector (edgeless diodes) developed for dosimetry in megavoltage radiotherapy for Cyberknife in a phantom and for patient quality assurance (QA).MethodThe characterization of the edgeless diodes has been performed on Cyberknife with fixed and IRIS collimators. The edgeless diode probes were tested in terms of basic QA parameters such as measurements of tissue‐phantom ratio (TPR), output factor and off‐axis ratio. The measurements were performed in both water and water‐equivalent phantoms. In addition, three patient‐specific plans have been delivered to a lung phantom with and without motion and dose measurements have been performed to verify the ability of the diodes to work as patient‐specific QA devices. The data obtained by the edgeless diodes have been compared to PTW 60016, SN edge, PinPoint ionization chamber, Gafchromic EBT3 film, and treatment planning system (TPS).ResultsThe TPR measurement performed by the edgeless diodes show agreement within 2.2% with data obtained with PTW 60016 diode for all the field sizes. Output factor agrees within 2.6% with that measured by SN EDGE diodes corrected for their field size dependence. The beam profiles’ measurements of edgeless diodes match SN EDGE diodes with a measured full width half maximum (FWHM) within 2.3% and penumbra widths within 0.148 mm. Patient‐specific QA measurements demonstrate an agreement within 4.72% in comparison with TPS.ConclusionThe edgeless diodes have been proved to be an excellent candidate for machine and patient QA for Cyberknife reproducing commercial dosimetry device measurements without need of angular dependence corrections. However, further investigation is required to evaluate the effect of their dose rate dependence on complex brain cancer dose verification.

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Angular independent silicon detector for dosimetry in external beam radiotherapy

Cited by 21 publications

References 43 publications

Development of a silicon diode detector for skin dosimetry in radiotherapy

Development of a silicon diode detector for skin dosimetry in radiotherapy

“Characterization of ELEKTA SRS cone collimator using high spatial resolution monolithic silicon detector array”

Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector

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