GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Online Resource
    Online Resource
    Depth Scaling of Solid Phantom for Intensity Modulated Radiotherapy Beams
    Oxford University Press (OUP) ; 2010
    In:  Journal of Radiation Research Vol. 51, No. 6 ( 2010), p. 707-713
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), Vol. 51, No. 6 ( 2010), p. 707-713
    Type of Medium: Online Resource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1269/jrr.10058
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2010
    detail.hit.zdb_id: 2038914-0
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    Reference dosimetry condition and beam quality correction factor for CyberKnife beam
    Wiley ; 2008
    In:  Medical Physics Vol. 35, No. 10 ( 2008-10), p. 4591-4598
    Details
    In: Medical Physics, Wiley, Vol. 35, No. 10 ( 2008-10), p. 4591-4598
    Abstract: This article is intended to improve the certainty of the absorbed dose determination for reference dosimetry in CyberKnife beams. The CyberKnife beams do not satisfy some conditions of the standard reference dosimetry protocols because of its unique treatment head structure and beam collimating system. Under the present state of affairs, the reference dosimetry has not been performed under uniform conditions and the beam quality correction factor for an ordinary linear accelerator has been temporally substituted for the of the CyberKnife in many sites. Therefore, the reference conditions and as a function of the beam quality index in a new way are required. The dose flatness and the error of dosimeter reading caused by radiation fields and detector size were analyzed to determine the reference conditions. Owing to the absence of beam flattening filter, the dose flatness of the CyberKnife beam was inferior to that of an ordinary linear accelerator. And if the absorbed dose is measured with an ionization chamber which has cavity length of 2.4, 1.0 and in reference dosimetry, the dose at the beam axis for a field of collimator was underestimated 1.5%, 0.4%, and 0.2% on a calculation. Therefore, the maximum field shaped with a collimator and ionization chamber which has a cavity length of or shorter were recommended as the conditions of reference dosimetry. Furthermore, to determine the for the CyberKnife, the realistic energy spectrum of photons and electrons in water was simulated with the BEAMnrc. The absence of beam flattening filter also caused softer photon energy spectrum than that of an ordinary linear accelerator. Consequently, the for ionization chambers of a suitable size were determined and tabulated as a function of measurable beam quality indexes in the CyberKnife beam.
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Article
    DOI: 10.1118/1.2978228
    Language: English
    Publisher: Wiley
    Publication Date: 2008
    detail.hit.zdb_id: 1466421-5
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Contrast enhancement for portal images by combination of subtraction and reprojection processes for Compton scattering
    Wiley ; 2017
    In:  Journal of Applied Clinical Medical Physics Vol. 18, No. 6 ( 2017-11), p. 71-78
    Details
    In: Journal of Applied Clinical Medical Physics, Wiley, Vol. 18, No. 6 ( 2017-11), p. 71-78
    Abstract: For patient setup of the IGRT technique, various imaging systems are currently available. MV portal imaging is performed in identical geometry with the treatment beam so that the portal image provides accurate geometric information. However, MV imaging suffers from poor image contrast due to larger Compton scatter photons. In this work, an original image processing algorithm is proposed to improve and enhance the image contrast without increasing the imaging dose. Scatter estimation was performed in detail by MC simulation based on patient CT data. In the image processing, scatter photons were eliminated and then they were reprojected as primary photons on the assumption that Compton interaction did not take place. To improve the processing efficiency, the dose spread function within the EPID was investigated and implemented on the developed code. Portal images with and without the proposed image processing were evaluated by the image contrast profile. By the subtraction process, the image contrast was improved but the EPID signal was weakened because 15.2% of the signal was eliminated due to the contribution of scatter photons. Hence, these scatter photons were reprojected in the reprojection process. As a result, the tumor, bronchi, mediastinal space and ribs were observed more clearly than in the original image. It was clarified that image processing with the dose spread functions provides stronger contrast enhancement while maintaining a sufficient signal‐to‐noise ratio. This work shows the feasibility of improving and enhancing the contrast of portal images.
    Type of Medium: Online Resource
    ISSN: 1526-9914 , 1526-9914
    URL: Issue
    URL: Article
    DOI: 10.1002/acm2.2017.18.issue-6
    DOI: 10.1002/acm2.12181
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2010347-5
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Investigations of different kilovoltage x‐ray energy for three‐dimensional converging stereotactic radiotherapy system: Monte Carlo simulations with CT data
    Wiley ; 2006
    In:  Medical Physics Vol. 33, No. 12 ( 2006-12), p. 4635-4642
    Details
    In: Medical Physics, Wiley, Vol. 33, No. 12 ( 2006-12), p. 4635-4642
    Abstract: We are investigating three‐dimensional converging stereotactic radiotherapy (3DCSRT) with suitable medium‐energy x rays as treatment for small lung tumors with better dose homogeneity at the target. A computed tomography (CT) system dedicated for non‐coplanar converging radiotherapy was simulated with BEAMnrc (EGS4) Monte‐Carlo code for x‐ray energy of 147.5, 200, 300, and 500 kilovoltage (kVp). The system was validated by comparing calculated and measured percentage of depth dose in a water phantom for the energy of 120 and . A thorax phantom and CT data from lung tumors were used to compare dose homogeneities of kVp energies with MV energies of 4, 6, and . Three non‐coplanar arcs ( and ) around the center of the target were employed. The Monte Carlo dose data format was converted to the XiO RTP format to compare dose homogeneity, differential, and integral dose volume histograms of kVp and MV energies. In terms of dose homogeneity and DVHs, dose distributions at the target of all kVp energies with the thorax phantom were better than MV energies, with mean dose absorption at the ribs (human data) of 100%, 85%, 50%, 30% for 147.5, 200, 300, and , respectively. Considering dose distributions and reduction of the enhanced dose absorption at the ribs, a minimum of is suitable for the lung kVp 3DCSRT system.
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Article
    DOI: 10.1118/1.2361080
    Language: English
    Publisher: Wiley
    Publication Date: 2006
    detail.hit.zdb_id: 1466421-5
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 5
    Online Resource
    Online Resource
    Direct energy spectrum measurement of X‐ray from a clinical linac
    Wiley ; 2021
    In:  Journal of Applied Clinical Medical Physics Vol. 22, No. 8 ( 2021-08), p. 255-264
    Details
    In: Journal of Applied Clinical Medical Physics, Wiley, Vol. 22, No. 8 ( 2021-08), p. 255-264
    Abstract: A realistic X‐ray energy spectrum is essential for accurate dose calculation using the Monte Carlo (MC) algorithm. An energy spectrum for dose calculation in the radiation treatment planning system is modeled using the MC algorithm and adjusted to obtain acceptable agreement with the measured percent depth dose (PDD) and off‐axis ratio. The simulated energy spectrum may not consistently reproduce a realistic energy spectrum. Therefore, direct measurement of the X‐ray energy spectrum from a linac is necessary to obtain a realistic spectrum. Previous studies have measured low photon fluence directly, but the measurement was performed with a nonclinical linac with a thick target and a long target‐to‐detector distance. In this study, an X‐ray energy spectrum from a clinical linac was directly measured using a NaI(Tl) scintillator at an ultralow dose rate achieved by adjusting the gun grid voltage. The measured energy spectrum was unfolded by the Gold algorithm and compared with a simulated spectrum using statistical tests. Furthermore, the PDD was calculated using an unfolded energy spectrum and a simulated energy spectrum was compared with the measured PDD to evaluate the validity of the unfolded energy spectrum. Consequently, there was no significant difference between the unfolded and simulated energy spectra by nonparametric, Wilcoxon's rank‐sum, chi‐square, and two‐sample Kolmogorov–Smirnov tests with a significance level of 0.05. However, the PDD calculated from the unfolded energy spectrum better agreed with the measured compared to the calculated PDD results from the simulated energy spectrum. The adjustment of the incident electron parameters using MC simulation is sensitive and takes time. Therefore, it is desirable to obtain the energy spectrum by direct measurement. Thus, a method to obtain the realistic energy spectrum by direct measurement was proposed in this study.
    Type of Medium: Online Resource
    ISSN: 1526-9914 , 1526-9914
    URL: Issue
    URL: Article
    DOI: 10.1002/acm2.v22.8
    DOI: 10.1002/acm2.13354
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2010347-5
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 6
    Online Resource
    Online Resource
    A national survey on the medical physics workload of external beam radiotherapy in Japan
    Oxford University Press (OUP) ; 2023
    In:  Journal of Radiation Research ( 2023-10-10)
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), ( 2023-10-10)
    Abstract: Several staffing models are used to determine the required medical physics staffing, including radiotherapy technologists, of radiation oncology departments. However, since Japanese facilities tend to be smaller in scale than foreign ones, those models might not apply to Japan. Therefore, in this study, we surveyed workloads in Japan to estimate the optimal medical physics staffing in external beam radiotherapy. A total of 837 facilities were surveyed to collect information regarding radiotherapy techniques and medical physics specialists (RTMPs). The survey covered facility information, staffing, patient volume, equipment volume, workload and quality assurance (QA) status. Full-time equivalent (FTE) factors were estimated from the workload and compared with several models. Responses were received from 579 facilities (69.2%). The median annual patient volume was 369 at designated cancer care hospitals (DCCHs) and 252 across all facilities. In addition, the median FTE of RTMPs was 4.6 at DCCHs and 3.0 at all sites, and the average QA implementation rate for radiotherapy equipment was 69.4%. Furthermore, advanced treatment technologies have increased workloads, particularly in computed tomography simulations and treatment planning tasks. Compared to published models, larger facilities (over 500 annual patients) had a shortage of medical physics staff. In very small facilities (about 140 annual patients), the medical physics staffing requirement was estimated to be 0.5 FTE, implying that employing a full-time medical physicist would be inefficient. However, ensuring the quality of radiotherapy is an important issue, given the limited number of RTMPs. Our study provides insights into optimizing staffing and resource allocation in radiotherapy departments.
    Type of Medium: Online Resource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1093/jrr/rrad070
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2038914-0
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 7
    Online Resource
    Online Resource
    Bremsstrahlung and Photoneutron Leakage from Steel Shielding Board Impinged by 12-24 MeV Electrons Beams
    Oxford University Press (OUP) ; 2009
    In:  Journal of Radiation Research Vol. 50, No. 4 ( 2009), p. 363-369
    Details
    In: Journal of Radiation Research, Oxford University Press (OUP), Vol. 50, No. 4 ( 2009), p. 363-369
    Type of Medium: Online Resource
    ISSN: 0449-3060 , 1349-9157
    URL: Article
    DOI: 10.1269/jrr.09016
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2009
    detail.hit.zdb_id: 2038914-0
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...