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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Iranian Journal of Medical Physics
- نوع مقاله: Journal Article
- کلمات کلیدی: Adjacent Electron Fields,SSDeff,Isodose Curve,Linear Accelerator
- چکیده:
- چکیده انگلیسی: Introduction: Treatment with megavoltage electron beams is ideal for irradiating superficial tumors because of their limited range in tissues. However, for electron treatment of extended areas, such as the chest wall, two or more adjacent fields can be used. Abutment of these fields may lead to significant dose in homogeneities in the junction region. The aim of this study is to offer a new method for generating a homogeneous dose distribution in the junction region between two adjacent fields in electron beam therapy.
Materials and Methods: Several approaches have been proposed to solve the problem of ‘hot’ and ‘cold’ spots in the junction region between abutting electron fields. These techniques are based on beam-edge modifying devices or penumbra generators which act to broaden the electron beam penumbra, and thus facilitate field matching. But use of these devices is time consuming and design of the modifications to the applicators are generally applicator dependent. An idea which was originally proposed for matching two adjacent photon fields (with dose inhomogeneity of about 2%) is resurrected here. This method is based on the rotation of the gantry such that the adjacent fields have a common edge and the overlap region in treatment volume is eliminated. For this purpose, the effective source to surface distance (SSDeff) for the available electron beam energies (6, 9, 12 and 15 MeV) and applicators (cones) (6 × 6, 10 × 10, 15 ×15, 20 × 20 and 25 × 25 cm2) have been determined for a Varian 2100C linear accelerator.
Result: Using SSDeff, in respect to beam divergence, one can use the photon beam behavior for electron beams and achieve a uniform dose distribution in adjacent electron fields.
Discussion and Conclusion: Compared to beam-edge modifying devices or penumbra generators that are usually time consuming to plan and set up, rotating the gantry to eliminate the overlap region is simple and applicable in the problem of abutting electron fields.- انتشار مقاله: 06-11-1388
- نویسندگان: Mohammad Javad Tahmasebi Birgani,Mohammad Ali Behrooz,Hadi Keivan
- مشاهده
- جایگاه : پژوهشی
- مجله: Asian Pacific Journal of Cancer Prevention
- نوع مقاله: Journal Article
- کلمات کلیدی:
- چکیده:
- چکیده انگلیسی: Background and objectives: To determine the head scatter factor, a formalism presented by Vadash and Bjärngard
has been employed to assess collimator exchange effects. The aim of this study was to determine the best Vadash
correction factor (A) by introducing a new method based on the output factor measured in air for different square and
rectangular fields. Materials and Methods: A new simple mathematical method based on selection of the best dosimetric
data was proposed to obtain the A value for Vadash to predict the equivalent square field size. Measurements were
performed with a Farmer c- انتشار مقاله: 09-09-1378
- نویسندگان: Mohammad Javad Tahmasebi Birgani,Nahid Chegni,Marziyeh Tahmasbi,Raziye Fayazi,Jafar Fatahi Asl,Mohammad Ali Behrouz
- مشاهده
- جایگاه : پژوهشی
- مجله: Asian Pacific Journal of Cancer Prevention
- نوع مقاله: Journal Article
- کلمات کلیدی: Colon cancer,Electroporation,Irradiation,Radiosensitizing
- چکیده:
- چکیده انگلیسی: Background: The efficiency of radiotherapy for tumors can be enhanced with different radiosensitizers. Previous
studies have shown that electroporation (EP) can sensitize some cancer cell lines to ionizing radiation (IR). HT-29
is a radiation resistant colorectal cancer cell line, representative of a cancer type which is the second cause of cancer
mortalities in developed countries. The present study aimed to evaluate radiosensitizing effects of EP on HT-29 cells
in vitro exposed to 6 MV X-ray photon beams. Methods: HT-29 cells were exposed to a 6 MV X-ray photon beam
as the control or to a combination of electroporation and irradiation. The response of cells was evaluated by colony
formation assay and survival curves. Results: The survival fraction of the HT-29 cells was significantly decreased by
electroporation prior to radiotherapy. A single electric pulse increased colorectal HT-29 cancer cell sensitivity to megavoltage
radiation by a factor of 1.36. Conclusion: Our findings showed that EP before radiotherapy can significantly
enhance tumor cell sensitivity. This combined treatment modality should be assessed for its applicability in clinic settings
for employment against radioresistant cancers. However, to facilitate achieving this goal, many different tumors with
a broad range of radiosensitivities should be evaluated.- انتشار مقاله: 14-05-1396
- نویسندگان: Ali Yadollahpour,Zohre Rezaee,Vahid Bayati,Mohammad Javad Tahmasebi Birgani,Fereshteh Negad Dehbashi
- مشاهده