Angular independent silicon detector for dosimetry in external beam radiotherapy

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dc.contributor.authorPetasecca, Men_AU
dc.contributor.authorAlhujaili, Sen_AU
dc.contributor.authorAldosari, AHen_AU
dc.contributor.authorFuduli, Ien_AU
dc.contributor.authorNewal, Men_AU
dc.contributor.authorPorumb, CSen_AU
dc.contributor.authorCarolan, MGen_AU
dc.contributor.authorNitschke, Ken_AU
dc.contributor.authorLerch, MLFen_AU
dc.contributor.authorKalliopuska, Jen_AU
dc.contributor.authorPerevertaylo, VLen_AU
dc.contributor.authorRosenfeld, ABen_AU
dc.date.accessioned2020-03-23T07:20:51Zen_AU
dc.date.available2020-03-23T07:20:51Zen_AU
dc.date.issued2015-07-17en_AU
dc.description.abstractPurpose: In this work, the “edgeless” silicon detector technology is investigated, in combination with an innovative packaging solution, to manufacture silicon detectors with negligible angular response. The new diode is also characterized as a dosimeter for radiotherapy with the aim to verify its suitability as a single detector for in vivo dosimetry as well as large area 2D array that does not require angular correction to their response. Methods: For the characterisation of the “edgeless-drop-in” detector technology, a set of samples have been manufactured with different sensitive areas (1 × 1 and 0.5 × 0.5 mm2) and different thicknesses (0.1 and 0.5 mm) in four different combinations of top and peripheral p–n junction fabricated on p-type and n-type silicon substrates. The diode probes were tested in terms of percentage depth dose (PDD), dose rate, and linearity and compared to ion chambers. Measurements of the output factor have been compared to film. The angular response of the diodes probes has been tested in a cylindrical PMMA phantom, rotated with bidirectional accuracy of 0.25° under 10 × 10 cm2 6 MV Linac photon beam. The radiation hardness has been investigated as well as the effect of radiation damage on the angular and dose rate response of the diode probes when irradiated with photons from a Co-60 gamma source up to dose of 40 kGy. Results: The PDDs measured by the edgeless detectors show an agreement with the data obtained using ion chambers within ±2%. The output factor measured with the smallest area edgeless diodes (0.5 × 0.5 mm2—0.1 and 0.5 mm thick) matches EBT3 film to within 2% for square field size from 10 to 0.5 cm side equivalent distance. The dose rate dependence in a dose per pulse range of 0.9 × 10−5–2.7 × 10−4 Gy/pulse was less than −7% and +300% for diodes fabricated on p-type and n-type substrates, respectively. The edgeless diodes fabricated on the p-type substrate demonstrated degradation of the response as a function of the irradiation dose within 5%–15%, while diodes on the n-type substrate show a variation of approximately 30% after 40 kGy. The angular response of all probes is minimal (within 2%) but the N on N and P on P configurations show the best performances with an angular dependence of ±1.0% between 0° and 180° in the transversal direction. In this configuration, the space charge region of the passive diode extends from the behind and sidewall toward the anode on the top providing beneficial electric field distribution in the peripheral area of the diode. Such performance has also been tested after irradiation by Co-60 up to 40 kGy with no measurable change in angular response. Conclusions: A new edgeless-drop-in silicon diode fabrication and packaging technology has been used to develop detectors that show no significant angular dependence in their response for dosimetry in radiation therapy. From the characterisation of the diodes, proposed in a wide range of different geometries and configurations, the authors recommend the P-on-P detectors in conjunction with “drop in” packaging technology as the candidate for further development as single diode probe or 2D diode array for dosimetry in radiotherapy. © 2015 American Association of Physicists in Medicineen_AU
dc.identifier.citationPetasecca, M., Alhujaili, S., Aldosari, A. H., Fuduli, I., Newall, M., Porumb, C. S., Carolan, M., Nitschke, K., Lerch, M. L. F., Kalliopuska, J., Perevertaylo, V. & Rosenfeld, A. B. (2015). Angular independent silicon detector for dosimetry in external beam radiotherapy. Medical physics, 42(8), 4708-4718. doi:10.1118/1.4926778en_AU
dc.identifier.govdoc8849en_AU
dc.identifier.issn2473-4209en_AU
dc.identifier.issue8en_AU
dc.identifier.journaltitleMedical physicsen_AU
dc.identifier.pagination4708-4718en_AU
dc.identifier.urihttps://doi.org/10.1118/1.4926778en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/9196en_AU
dc.identifier.volume42en_AU
dc.language.isoenen_AU
dc.publisherAmerican Association of Physicists in Medicineen_AU
dc.subjectPhantomsen_AU
dc.subjectDosimetryen_AU
dc.subjectIonization chambersen_AU
dc.subjectLinear acceleratorsen_AU
dc.subjectSiliconen_AU
dc.subjectPhoton beamsen_AU
dc.subjectPMMAen_AU
dc.subjectRadiotherapyen_AU
dc.subjectRadiation detectorsen_AU
dc.subjectCobalt 60en_AU
dc.titleAngular independent silicon detector for dosimetry in external beam radiotherapyen_AU
dc.typeJournal Articleen_AU
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