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  • Oxford University Press (OUP)  (7)
  • Mizuno, Hirokazu  (7)
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  • Oxford University Press (OUP)  (7)
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  • 1
    Online-Ressource
    Online-Ressource
    Curtailing patient-specific IMRT QA procedures from 2D dose error distribution
    Oxford University Press (OUP) ; 2016
    In:  Journal of Radiation Research Vol. 57, No. 3 ( 2016-06-01), p. 258-264
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), Vol. 57, No. 3 ( 2016-06-01), p. 258-264
    Kurzfassung: A patient-specific quality assurance (QA) test is conducted to verify the accuracy of dose delivery. It generally consists of three verification processes: the absolute point dose difference, the planar dose differences at each gantry angle, and the planar dose differences by 3D composite irradiation. However, this imposes a substantial workload on medical physicists. The objective of this study was to determine whether our novel method that predicts the 3D delivered dose allows certain patient-specific IMRT QAs to be curtailed. The object was IMRT QA for the pelvic region with regard to point dose and composite planar dose differences. We compared measured doses, doses calculated in the treatment planning system, and doses predicted by in-house software. The 3D predicted dose was reconstructed from the per-field measurement by incorporating the relative dose error distribution into the original dose grid of each beam. All point dose differences between the measured and the calculated dose were within ±3%, whereas 93.3% of them between the predicted and the calculated dose were within ±3%. As for planar dose differences, the gamma passing rates between the calculated and the predicted dose were higher than those between the calculated and the measured dose. Comparison and statistical analysis revealed a correlation between the predicted and the measured dose with regard to both point dose and planar dose differences. We concluded that the prediction-based approach is an accurate substitute for the conventional measurement-based approach in IMRT QA for the pelvic region. Our novel approach will help medical physicists save time on IMRT QA.
    Materialart: Online-Ressource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1093/jrr/rrv084
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2016
    ZDB Id: 2038914-0
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 2
    Online-Ressource
    Online-Ressource
    A robust measurement point for dose verification in delivery quality assurance for a robotic radiosurgery system
    Oxford University Press (OUP) ; 2017
    In:  Journal of Radiation Research Vol. 58, No. 3 ( 2017-05-01), p. 378-385
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), Vol. 58, No. 3 ( 2017-05-01), p. 378-385
    Kurzfassung: In this CyberKnife® dose verification study, we investigated the effectiveness of the novel potential error (PE) concept when applied to the determination of a robust measurement point for targeting errors. PE was calculated by dividing the differences between the maximum increases and decreases in dose distributions by the original distribution after obtaining the former by shifting the source-to-axis and off-axis distances of each beam by ±1.0 mm. Thus, PE values and measurement point dose heterogeneity were analyzed in 48 patients who underwent CyberKnife radiotherapy. Sixteen patients who received isocentric dose delivery were set as the control group, whereas 32 who received non-isocentric dose delivery were divided into two groups of smaller PE (SPE) and larger PE (LPE) by using their median PE value. The mean dose differences (± standard deviations) were 1.0 ± 0.9%, 0.5 ± 1.4% and 4.1 ± 2.8% in the control, SPE and LPE groups, respectively. We observed significant correlations of the dose difference with the PE value (r = 0.582, P  & lt; 0.001) and dose heterogeneity (r = 0.471, P  & lt; 0.001). We concluded that when determining a robust measurement point for CyberKnife point dose verification, PE evaluation was more effective than the conventional dose heterogeneity-based method that introduced optimal measurement point dose heterogeneity of & lt;10% across the detector.
    Materialart: Online-Ressource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1093/jrr/rrw103
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2017
    ZDB Id: 2038914-0
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 3
    Online-Ressource
    Online-Ressource
    Feasibility of synthetic computed tomography generated with an adversarial network for multi-sequence magnetic resonance-based brain radiotherapy
    Oxford University Press (OUP) ; 2020
    In:  Journal of Radiation Research Vol. 61, No. 1 ( 2020-01-23), p. 92-103
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), Vol. 61, No. 1 ( 2020-01-23), p. 92-103
    Kurzfassung: The aim of this work is to generate synthetic computed tomography (sCT) images from multi-sequence magnetic resonance (MR) images using an adversarial network and to assess the feasibility of sCT-based treatment planning for brain radiotherapy. Datasets for 15 patients with glioblastoma were selected and 580 pairs of CT and MR images were used. T1-weighted, T2-weighted and fluid-attenuated inversion recovery MR sequences were combined to create a three-channel image as input data. A conditional generative adversarial network (cGAN) was trained using image patches. The image quality was evaluated using voxel-wise mean absolute errors (MAEs) of the CT number. For the dosimetric evaluation, 3D conformal radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT) plans were generated using the original CT set and recalculated using the sCT images. The isocenter dose and dose–volume parameters were compared for 3D-CRT and VMAT plans, respectively. The equivalent path length was also compared. The mean MAEs for the whole body, soft tissue and bone region were 108.1 ± 24.0, 38.9 ± 10.7 and 366.2 ± 62.0 hounsfield unit, respectively. The dosimetric evaluation revealed no significant difference in the isocenter dose for 3D-CRT plans. The differences in the dose received by 2% of the volume (D2%), D50% and D98% relative to the prescribed dose were  & lt;1.0%. The overall equivalent path length was shorter than that for real CT by 0.6 ± 1.9 mm. A treatment planning study using generated sCT detected only small, clinically negligible differences. These findings demonstrated the feasibility of generating sCT images for MR-only radiotherapy from multi-sequence MR images using cGAN.
    Materialart: Online-Ressource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1093/jrr/rrz063
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2020
    ZDB Id: 2038914-0
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 4
    Online-Ressource
    Online-Ressource
    Dose–volume analysis of predictors for chronic gastrointestinal complications in patients with cervical cancer treated with postoperative concurrent chemotherapy and whole-pelvic radiation therapy
    Oxford University Press (OUP) ; 2016
    In:  Journal of Radiation Research Vol. 57, No. 6 ( 2016-11-01), p. 668-676
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), Vol. 57, No. 6 ( 2016-11-01), p. 668-676
    Kurzfassung: The purpose of this study is to evaluate dose–volume histogram (DVH) predictors for the development of chronic gastrointestinal (GI) complications in patients with cervical cancer who have undergone postoperative concurrent chemotherapy and whole-pelvic radiation therapy (WPRT). The subjects were 135 patients who had undergone postoperative WPRT with concurrent nedaplatin-based chemotherapy between 2000 and 2014. Associations between selected DVH parameters and the incidence of chronic GI complications of G3 or higher were evaluated. Chronic GI complications of severity G3 occurred in 18 (13%) patients. Patients with GI complications had significantly greater V5–V45, mean dose and the generalized equivalent uniform dose (gEUD) of the small bowel loops, compared with those without GI complications. V30–V45, mean dose and gEUD of the bowel bag also showed significant differences between patients with and without GI complications. In contrast, no parameter for the large bowel loop was correlated with GI complications. Receiver operating characteristics curve analysis indicated that V30–V45 of the small bowel loops were better predictors than these respective parameters for the bowel bag. Next, patients were divided into four groups based on the median V15 and V40 of the small bowel loops. The group with both a high V15 and a high V40 showed a significantly higher probability of chronic GI complications. In conclusion, the small bowel loops are better predictors of chronic GI complications compared with the bowel bag, and a relatively high-dose volume (e.g. V40) of the small bowel loops is a useful predictor of chronic GI complications.
    Materialart: Online-Ressource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1093/jrr/rrw037
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2016
    ZDB Id: 2038914-0
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 5
    Online-Ressource
    Online-Ressource
    Characterization of a microSilicon diode detector for small-field photon beam dosimetry
    Oxford University Press (OUP) ; 2020
    In:  Journal of Radiation Research Vol. 61, No. 3 ( 2020-05-22), p. 410-418
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), Vol. 61, No. 3 ( 2020-05-22), p. 410-418
    Kurzfassung: This study characterized a new unshielded diode detector, the microSilicon (model 60023), for small-field photon beam dosimetry by evaluating the photon beams generated by a TrueBeam STx and a CyberKnife. Temperature dependence was evaluated by irradiating photons and increasing the water temperature from 11.5 to 31.3°C. For Diode E, microSilicon, microDiamond and EDGE detectors, dose linearity, dose rate dependence, energy dependence, percent-depth-dose (PDD), beam profiles and detector output factor (OFdet) were evaluated. The OFdet of the microSilicon detector was compared to the field output factors of the other detectors. The microSilicon exhibited small temperature dependence within 0.4%, although the Diode E showed a linear variation with a ratio of 0.26%/°C. The Diode E and EDGE detectors showed positive correlations between the detector reading and dose rate, whereas the microSilicon showed a stable response within 0.11%. The Diode E and microSilicon demonstrated negative correlations with the beam energy. The OFdet of microSilicon was the smallest among all the detectors. The maximum differences between the OFdet of microSilicon and the field output factors of microDiamond were 2.3 and 1.6% for 5 × 5 mm2 TrueBeam and 5 mm φ CyberKnife beams, respectively. The PDD data exhibited small variations in the dose fall-off region. The microSilicon and microDiamond detectors yielded similar penumbra widths, whereas the other detectors showed steeper penumbra profiles. The microSilicon demonstrated favorable characteristics including small temperature and dose rate dependence as well as the small spatial resolution and output factors suitable for small field dosimetry.
    Materialart: Online-Ressource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1093/jrr/rraa010
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2020
    ZDB Id: 2038914-0
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 6
    Online-Ressource
    Online-Ressource
    Correction of lateral response artifacts from flatbed scanners for dual-channel radiochromic film dosimetry
    Oxford University Press (OUP) ; 2021
    In:  Journal of Radiation Research Vol. 62, No. 2 ( 2021-03-10), p. 319-328
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), Vol. 62, No. 2 ( 2021-03-10), p. 319-328
    Kurzfassung: In this study, we evaluated the inter-unit variability of the lateral response artifact for multiple flatbed scanners, focusing on the dual-channel method, and investigated the correction method of the lateral non-uniformity. Four scanners with A3+ paper-size and five scanners with A4 paper-size were evaluated. To generate the dose–response curves, small pieces of the Gafchromic EBT3 and EBT-XD films were irradiated, and five of the pieces were repeatedly scanned by moving them on the scanner to evaluate the lateral non-uniformity. To calculate the dose distribution accounting for the lateral non-uniformity, linear functions of the correction factor, representing the difference between the pixel values at offset position and the scanner midline, were calculated for red and blue color channels at each lateral position. Large variations of the lateral non-uniformity among the scanners were observed, even for the same model of scanner. For high dose, red color showed pixel value profiles similar to symmetric curves, whereas the profiles for low dose were asymmetric. The peak positions changed with dose. With correction of the lateral non-uniformity, the dose profiles of the pyramidal dose distribution measured at various scanner positions and that calculated with a treatment planning system showed almost identical profile shapes at all high-, middle- and low-dose levels. The dual-channel method used in this study showed almost identical dose profiles measured with all A3+ and A4 paper-size scanners at any positions when the corrections were applied for each color channel.
    Materialart: Online-Ressource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1093/jrr/rraa124
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2021
    ZDB Id: 2038914-0
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
  • 7
    Online-Ressource
    Online-Ressource
    Characteristics of microSilicon diode detector for electron beam dosimetry
    Oxford University Press (OUP) ; 2021
    In:  Journal of Radiation Research ( 2021-09-24)
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), ( 2021-09-24)
    Kurzfassung: A microSilicon™ (PTW type 60023), a new unshielded diode detector succeeding Diode E (model 60017, PTW), was characterized for electron beam dosimetry and compared with other detectors. Electron beams generated from a TrueBeam linear accelerator were measured using the microSilicon, Diode E, and microDiamond synthetic single-crystal diamond detector. Positional accuracy of microSilicon was measured by data collected in air and water. The percent depth dose (PDD), off-center ratio (OCR), dose–response linearity, dose rate dependence, and cone factors were evaluated. The PDDs were compared with data measured using a PPC40 plane-parallel ionization chamber. The maximum variations of depth of 50% and 90% of the maximum dose, and practical depth among all detectors and energies were 0.9 mm. The maximum variations of the bremsstrahlung dose among all detectors and energies were within 0.3%. OCR showed good agreement within 1% for the flat and tail regions. The microSilicon detector showed a penumbra width similar to microDiamond, whereas Diode E showed the steepest penumbra shape. All detectors showed good dose–response linearity and stability against the dose rate; only Diode E demonstrated logarithmic dose rate dependency. The cone factor measured with microSilicon was within ±1% for all energies and cone sizes. We demonstrated that the characteristics of microSilicon is suitable for electron beam dosimetry. The microSilicon detector can be a good alternative for electron beam dosimetry in terms of providing an appropriate PDD curve without corrections, high spatial resolution for OCR measurements and cone factors.
    Materialart: Online-Ressource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1093/jrr/rrab085
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2021
    ZDB Id: 2038914-0
    Standort Signatur Einschränkungen Verfügbarkeit
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    Online-Ressource
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