title: Determination of linear x-ray attenuation coefficients of pathological brain tissues and use of filters in tissue contrast enhancement in computed tomography.
abstract: OBJECTIVE
  X-ray attenuation coefficients are used in common radiological, pathological and spectroscopic examinations and in the determination of the radiation dose distribution in biological tissues. In radiology, these coefficients enable diagnosis by differentiating the abnormal tissues from the normal ones using their morphological structure and contrast differences. In this study, our aim is to precisely determine the linear x-ray attenuation coefficients of pathological brain tissues and to use x-ray beam filters to enhance the tissue contrast in computed tomography.
  
  
  METHODS
  To directly measure the relative linear attenuation coefficients, an energy dispersive x-ray spectroscopy system (EDXRS-Canberra, Si(Li) with DSA-1000 spectrum analyzer 1998; CT, USA) was used with collimators and a medical-purpose x-ray tube (Siemens, Siremobil, 1985; Erlangen, Germany) in a linear geometry.
  
  
  RESULTS
  Using a Mo filter with Computed Tomography CT and photon energies from 15 to 25 keV, EDXRS acquisitions were found to significantly distinguish grades of brain tumors (p<0.05). For the data acquired from CT systems with the decreasing filtered photon mean energy, the x-ray attenuation coefficients (i.e., the Hounsfield units) show that the ratio of EDXRS to CT for water's attenuation coefficient are increased. With our suggested x-ray filters, the tissue contrast has been found to be increased in ex vivo brain tumor slices compared with slices scanned in conventional CT scanners.
  
  
  CONCLUSIONS
  X-ray attenuations measured with the EDXRS are found to be statistically more reliable because of the length of acquisition times in this study.
authors.affiliation: Ataturk University, Faculty of Medicine, Radiology Department, Erzurum, Turkey.
authors.forename: M Erdem
authors.initials: ME
authors.lastname: Sagsoz
authors.affiliation: Ataturk University, Faculty of Medicine, Pathology Department, Erzurum, Turkey.
authors.forename: Fazlı
authors.initials: F
authors.lastname: Erdogan
authors.affiliation: Ataturk University Faculty of Science and Arts, Physics Department, Erzurum, Turkey.
authors.forename: Salih Z
authors.initials: SZ
authors.lastname: Erzeneoglu
authors.affiliation: Ataturk University, Faculty of Medicine, Radiology Department, Erzurum, Turkey.
authors.forename: İhsan
authors.initials: İ
authors.lastname: Yuce
keywords: Computed tomography; X-ray attenuation coefficient; X-ray spectral filters; X-ray tube