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ABSTRACT

Background:

Coherent scattering leads to diffraction effects and especially constructive interferences. These

interferences carry some information about the molecular structure of the tissue. As breast cancer is

the most widespread cancer in women, this project evaluated the application of small angle

X-ray scattering (SAXS) for differentiation between normal and cancerous breast tissues.

Small angle X-ray scattering (to angles less than 10°) is predominantly coherent.

Materials and Methods:

primary collimator, sample holder, secondary collimator and HP Ge detector was used. The best

constructive interference was found to be at 6.5

at several angles of 4, 5, 6, 6.5 and 7.3 degrees. The total number of 99 breast tissue samples,

including normal and tumor were studied at the 6.5

transfer was obtained for each sample.

The energy dispersive method with a set up including X-ray tube,° after doing experiments on adipose breast tissue°. The corrected intensity versus momentum

Results:

adipose tissue and mixed tissue (adipose & fibroglandular) from tumor in peak positions (each

coherent scattering spectrum has a peak that its position is determined by momentum transfer).

Furthermore adipose tissue has shown significantly higher peaks than other breast tissues. Benign

and malignant breast tissues were differentiated by both peak positions and peak heights (each

peak has a height in coherent scattering spectrum). Preservation of samples nitrogen tank had no

effects on molecular structure of the breast tissue.

Adipose tissue shows a sharp peak in low momentum transfer region. It is easy to separate

Conclusion:

between normal, benign and malignant breast tissues.

By energy dispersive small angle X-ray scattering, it is possible to differentiateIran. J. Radiat. Res., 2005 2 (4): 205-210

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Background: Recently, it has been indicated that X-ray coherent scatter from biological tissues can be used to access signature of tissue. Some scientists are interested in studying this effect to get early detection of breast cancer. Since experimental methods for optimization are time consuming and expensive, some scientists suggest using simulation. Monte Carlo (MC) codes are the best option for radiation simulation however, one permanent defect with MC codes has been the lack of a sufficient physical model for coherent (Rayleigh) scattering, including molecular interference effects. Materials and Methods: It was decided to obtain molecular interference functions of coherent X-ray scattering for normal breast tissues by combination of modeling and experimental methods. A Monte Carlo simulation program was written to simulate the angular distribution of scattered photons for the normal breast tissue samples. Moreover, experimental diffraction patterns of these tissues were measured by means of energy dispersive X-ray diffraction (EDXRD) method. The simulation and experimental data were used to obtain a tabulation of molecular interference functions for breast tissues. Results: With this study a tabulation of molecular interference functions for normal breast tissues was prepared to facilitate the simulation diffraction patterns of the tissues without any experimental. Conclusion: The method may lead to design new systems for early detection of breast cancer. Iran. J. Radiat. Res., 2009 7 (2): 113-117

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Background: The advantages of proton beam in radiation therapy- like small lateral scattering as well as absence of exit dose tail in the organs which are after the tumor- make it capable of delivering more treatment doses to the target and much lesser to the critical tissues near it. Materials and Methods: In this study, the Monte Carlo MCNPX code has been used to simulate a slab head phantom irradiated by proton pencil beams. The simplified slab has tissue compositions of the ICRU 46, and the necessary data have been taken from adult male phantom of MIRD-ORNL family series. Results: Suitable energy range of incident proton beams has been estimated in order to have the Bragg peaks inside the brain tissue. Energy straggling or, rather, range straggling, and multiple scattering which affect the lateral broadening of incident beams, have been investigated. Conclusion: The results show that the FWHM (Full Wide in Half Maximum) increases more than six times from 1.73 mm to 10.78 mm for the energy range of 50 - 135 MeV. The FWHM values of lateral dose profiles change from 1 mm in 50 MeV to 7.5 mm in 135 MeV, and it has been shown that when a pencil beam is used to irradiate a tissue, the absorbed dose in depth along the central axis does not show a Bragg peak pattern.

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Background: Skyshine describes the radiation scattered by the atmosphere above a LINAC facility to a point on the ground. The aim of this study was to measure the skyshine photon dose rates from two different (9 MV and 18 MV) medical linear accelerators. Materials and Methods: The photon beam was directed upward (180° gantry position), with a maximum photon field size (40 × 40 cm2) at the isocenter. Measurements were obtained around the external points selected outside the room facilities at a horizontal distance from the target by the calibrated RDS-110 survey meter at four points around the isocenter. Results: The measured values of the skyshine photon exposure rates at four points for 9 MV and 18 MV were 0.6, 0.5, 0.5, and 0.4 μSv/h, and 0.6, 0.4, 0.4, and 0.5 μSv/h, respectively. All the measured skyshine photon exposure rates were lower than the values recommended by NCRP 147. Conclusion: There is a poor agreement between the measured and the calculated values; therefore it seems that caution is needed while using the equations available in NCRP 147 or 151.

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