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Showing 7 results for Osei
A. Kazemian, Sh. Kamian, M. S. Hoseini, M.r. Azizi,
Volume 3, Issue 3 (12-2005)
Abstract
ABSTRACT Soft tissue sarcomas of the oral cavity are uncommon malignancies those of smooth-muscle origin are extremely rare. Leiomyosarcomas of the tongue are very rare. Either surgery or radiation therapy with or without chemotherapy are the treatment modalities which improve prognosis. We are presenting a 32-year-old man with leiomyosarcoma of the lateral aspect of the oral tongue with neck metastasis, who was referred to our radio therapeutic oncology department after glossectomy and radical modified neck dissection. The clinical and pathologic features together with his clinical course will be discussed. Six months after chemoradiotherapy, he developed a single metastasis in his right femur, and then by features of lung metastasis he died in a few weeks, unfortunately.
M. Momennezhad, M.t. Bahreyni Toosi, R. Sadeghi, H. Gholamhoseinian, Sh. Nasseri,
Volume 7, Issue 4 (3-2010)
Abstract
Background: The presence of a wedge filter in
the beam trajectory can modify the beam quality and
cause some changes in the dosimetry parameters
which are usually difficult to be measured directly and
accurately. Material and Methods: In this study the
MCNP-4C Monte Carlo code was used to simulate the
9 MV photon beam generated by a linear accelerator.
Upon getting a good agreement between the Monte
Carlo simulated and measured dose distribution in
open fields, the model was used to simulate the
physical wedges. The steel wedges with angles from
15º-60º were modeled and the primary and the
secondary photon beams were calculated. The beam
profiles and wedges factors were calculated for each
wedge. The output factors were determined for 45 wedge. The calculated data were compared with the
measured values of the same parameters. Results:
The results showed that the use of wedges reduced
the fluencies of the primary and scattered photons
and also increased the average energy of the primary
and the scattered photons. The agreement between
the calculated and the measured data was better
than 2% for all wedges. The results also showed that
as the wedge angle increased, the electron contamination
of photon beam decreased. Conclusion: The
presence of a wedge in a 9 MV photon beam alters
the primary and the scattered components generated
by a linear accelerator. The simulated linac machine
and its associated data can be used to predict the
dose distribution in other complex fields. Iran. J.
Radiat. Res., 2010 7 (4): 223-227
A.r. Nikoofar, Dr. Z. Falahatpour, G.h. Hoseinzadeh,
Volume 12, Issue 3 (7-2014)
Abstract
Background: The aim of this study was to evaluate the reduction in excision cavity volume (ECV) during the whole breast radiotherapy (WBRT). The delineating of reduced cavity volume on secondary CT (computed tomography) might decrease the field size of boost plan. Materials and Methods: Twenty patients were treated having breast conservative surgery. At first, primary CT simulation (CT-1) was done prior to WBRT. Treatment planning was performed by a 3D treatment planning system. A CT-2 was performed after WBRT. Then the excision cavity was contoured on CT-1 and CT-2 for each patient. Boost irradiation was planned on both ECV-1 and ECV-2. Results: In Comparison of CT-1 and CT-2: The contoured volumes for ECV-1 and ECV-2 were on average of 42.9 cm3and 23.4 cm3, respectively (p< 0.002). The ECV-2 was reduced in 85% of the patients. Patients with ECV-1 greater than the mean value of ECV-1 (ECV-1> 35.5 cm3) had more reduction in ECV-2 than patient with ECV-1 smaller than the mean value (p < 0.000). The volume of normal breast tissue on CT-2 was decreased from the volume of CT-1 (p< 0.03). Conclusion: A significant reduction in excision cavity volume was shown during WBRT. This volume reduction made smaller sizes of boost field and remaining breast received lower doses. The reduction was more significant in patient with primary large ECV. The Secondary CT for boost planning is suggested for patients with larger cavities after WBRT.
Dr. Gr.n. Grigorov, K. Foster, J.c.l. Chow, E.k. Osei,
Volume 12, Issue 4 (10-2014)
Abstract
Background: In order to improve the evaluation of possible rectal toxicity based on the rectal normal tissue complication probability (NTCP), we consider the fractional dependence of the NTCP on the wall thickness (tW) and rectal displacement (RM). Materials and Methods: The two-dimensional NTCP model (NTCP2D) was developed using radiotherapy plans of ten randomly selected patients with prostate cancer. The clinical rectal structures were substituted with rectal walls of cylindrical shape. To simulate full, partially-full and empty state of the rectum, three tW were generated under the conditions of same length of the rectum and same volume of the rectal wall. A threshold iso-line, NTCPTR, was used to split the NTCP2D field into areas: a lower risk area and a higher risk area for rectal toxicity. Two factors are introduced to help with the estimation of NTCP: a volume factor k1 which is the ratio between the volumes of the rectal wall and the intersection of the rectal wall with the planning target volume and a probability factor k2, which is the ratio between the area of low risk to the entire area of the NTCP2D. Results: A correlation > 0.9 between factors k1 and k2 was found. Conclusion: The NTCP2D field and the ratios k1 and k2 can be used as a patient-specific parameters to evaluate the probability of rectal toxicity.
S.r. Mahdavi, M.r. Ay, Phd M. Zabihzadeh, M. Allahverdi, M. Shahriari, M. Hoseini-Ghahfarokhi,
Volume 17, Issue 1 (1-2019)
Abstract
Background: During intensity modulated radiation therapy (IMRT) technique, theoretically, presence of flattening filter (FF) across the beamline of clinical linear accelerator (linac) is not essential to obtain uniform lateral profiles due to intensity modulation of photon beams by multileaf collimators (MLCs). The aim of this study was to investigate the dosimetrical properties of 18 MV photon beam-Varian linac with and without FF. Materials and Methods: All dose measurements were performed on 18 MV, FF mode-Varian 2100C/D linac. The FF and flattening filter free (FFF) modes of linac were modeled by MCNPX 2.4. code. The photon and contaminant electrons spectra, dose rate, present depth doses (PDD), lateral dose profiles, total and collimator scatter factors and out of field doses were calculated and compared with and without FF. Results: Removing the FF increased the photon and contaminant electron fluences by factors of 5.48 and 3.94 for a 5 × 5 cm2 field size, respectively. The surface dose increased up to 155%. The flatness of dose profile was disturbed and deteriorated with increase of field size. Despite the dependence of the total scattering factor on field size, the variation of collimator scattering factors was neglected. The out-of-field dose decreased about 81.5 % for a 5 × 5 cm2 field size. Conclusion: Removing FF from the linac head increases the dose rate and decreases the out-of-field dose, but the increased skin dose and deteriorated flatness of lateral dose profile are the main disadvantages of the FFF mode.
Ph.d., M. Zabihzadeh, Z. Ghahremani, S.m. Hoseini, H. Shahbazian, M. Hoseini Ghahfarokhi,
Volume 18, Issue 3 (7-2020)
Abstract
Background: Presence of inhomogeneities such as lung tissue with low density can perturbs the dose distribution in the path of therapeutic photon beam and causes undesired cold or hot spots. The aim of this study was to investigate the effect of lung tissue inhomogeneities on dose distribution in thorax irradiation. Materials and Methods: The Monte Carlo simulation (MC) code of EGSnrc-based BEAMnrc was used to calculate dose distribution for 6 MV- Siemens Primus linear accelerator (Linac) in a homogenous phantom. Dose perturbation and inhomogeneity corrected factors (ICFs) were calculated due to implementation of lung tissue depended to the lung density and field size. Results: The maximum increased dose in lung tissue with lung density of 0.5 and 0.25gr/cm3 was 15.9%, 16.2%, 15.6%, 23.8 %, 24.8% and 25.0% for 6 × 6, 10 × 10 and 20 × 20 cm2 field sizes, respectively. The maximum ICF for these field sizes was 1.16 and 1.25 for lung density of 0.5 and 0.25gr/cm3, respectively. The maximum dose reduction in lung tissue with density of 0.25 and 0.5gr/cm3 was 19.5% and 4.2 %, and the related ICF was estimated 0.84 and 0.95, respectively. Conclusion: Involvement of lung tissue in the path of irradiation perturbs the dose distribution which is dependent to the lung density and field size. The ICFs resulted from our MC model could be useful to accurately calculate the dose distribution in radiotherapy of lung abnormalities.
S.m. Hosseini, A. Banaei, Z. Hoseini Motlagh, Dr. R. Abedi-Firouzjah, F. Falahati, H. Zamani, Dr. Y. Moghimi,
Volume 18, Issue 4 (10-2020)
Abstract
Background: The aim of this study was to estimate the cancer risks and mortalities of different types induced by routine examinations of digital radiography for one year in Mazandaran province, Iran. Materials and methods: Radiation parameters and calculated entrance skin dose (ESD) values of 13 digital radiographic examinations were collected from 2340 patients at 18 high-patient-load radiography centers. Organ mean doses were estimated based on the collected parameters applying PCXMC software. The BEIR VII-Phase 2 model was used to calculate the induced cancer risks and mortalities of various cancer types at different ages. Results: The average ± standard deviation (SD) lifetime risks (incidence probability in 100,000 people) induced by radiations from radiography examinations for one year was 51.29±4.73 and 99.62±7.36 for new-born males and females, respectively. The lifetime cancer risk decreased with age and reached 3.77±0.62 and 4.88±0.07 for 80-year men and women, respectively. The average lifetime risks of mortality due to cancers induced by annual radiographies were obtained at 14.18±1.62 and 22.83±2.55 for new-born males and females, respectively. This risk reduced with age and was reached 1.97±0.27 and 2.45±0.38 for men and women at the age of 80 years, respectively. Conclusion: Our results showed that there are low but significant risks of cancer incidence for patients undergoing digital radiography, which included a large percentage of the population in Mazandaran province, especially for children and newborns. Therefore, further efforts like appropriate patient setup and beam geometry should be carried out to decrease patient doses.
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