Publication:
Adapting a practical EPR dosimetry protocol to measure output factors in small fields with alanine.

cris.virtual.author-orcid0000-0002-3911-3403
cris.virtualsource.author-orcidfb089609-c18a-4ab4-bf39-a2d95248a9a9
dc.contributor.authorHöfel, Sebastian
dc.contributor.authorLiebig, Pauline
dc.contributor.authorFix, Michael
dc.contributor.authorDrescher, Malte
dc.contributor.authorZwicker, Felix
dc.date.accessioned2024-10-25T18:27:26Z
dc.date.available2024-10-25T18:27:26Z
dc.date.issued2023-12
dc.description.abstractPURPOSE Modern radiotherapy techniques often deliver small radiation fields. In this work, a practical Electron Paramagnetic Resonance (EPR) dosimetry protocol is adapted and applied to measure output factors (OF) in small fields of a 6 MV radiotherapy system. Correction factors and uncertainties are presented and OFs are compared to the values obtained by following TRS-483 using an ionization chamber (IC). METHODS Irradiations were performed at 10 cm depth inside a water phantom positioned at 90 cm source to surface distance with a 6 MV flattening filter free photon beam of a Halcyon radiotherapy system. OFs for different nominal field sizes (1 × 1, 2 × 2, 3 × 3, 4 × 4, normalized to 10 × 10 cm2 ) were determined with a PinPoint 3D (PTW 31022) IC following TRS-483 as well as with alanine pellets with a diameter of 4 mm and a height of 2.4 mm. EPR readout was performed with a benchtop X-band spectrometer. Correction factors due to volume averaging and due to positional uncertainties were derived from 2D film measurements. RESULTS OFs obtained from both dosimeter types agreed within 0.7% after applying corrections for the volume averaging effect. For the used alanine pellets, volume averaging correction factors of 1.030(2) for the 1 × 1 cm2 field and <1.002 for the larger field sizes were determined. The correction factor for positional uncertainties of 1 mm was in the order of 1.018 for the 1 × 1 cm2 field. Combined relative standard uncertainties uc for the OFs resulting from alanine measurements were estimated to be below 1.5% for all field sizes. For IC measurements, uc was estimated to be below 1.0%. CONCLUSIONS A practical EPR dosimetry protocol is adaptable for precisely measuring OFs in small fields down to 1 × 1 cm2 . It is recommended to consider the effect of positional uncertainties for field sizes <2 × 2 cm2 .
dc.description.sponsorshipUniversitätsklinik für Radio-Onkologie - Medizinische Strahlenphysik
dc.identifier.doi10.48350/188577
dc.identifier.pmid37922380
dc.identifier.publisherDOI10.1002/acm2.14191
dc.identifier.urihttps://boris-portal.unibe.ch/handle/20.500.12422/171131
dc.language.isoen
dc.publisherAmerican Association of Physicists in Medicine
dc.relation.ispartofJournal of applied clinical medical physics
dc.relation.issn1526-9914
dc.relation.organizationDCD5A442BAD6E17DE0405C82790C4DE2
dc.relation.organizationDCD5A442BAE6E17DE0405C82790C4DE2
dc.subjectEPR dosimetry alanine density effect output factor small field volume effect
dc.subject.ddc500 - Science::530 - Physics
dc.subject.ddc600 - Technology::610 - Medicine & health
dc.titleAdapting a practical EPR dosimetry protocol to measure output factors in small fields with alanine.
dc.typearticle
dspace.entity.typePublication
dspace.file.typetext
oaire.citation.issue12
oaire.citation.startPagee14191
oaire.citation.volume24
oairecerif.author.affiliationUniversitätsklinik für Radio-Onkologie - Medizinische Strahlenphysik
unibe.contributor.rolecreator
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unibe.date.licenseChanged2023-11-07 02:58:58
unibe.description.ispublishedpub
unibe.eprints.legacyId188577
unibe.refereedTRUE
unibe.subtype.articlejournal

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