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Measurement of dose in diagnostic radiology and the effect of dose reduction on image quality

In computed radiography (CR) images, dose reduction up to 0.10 mGy is possible in chest radiography without image manipulation.  A lower dose of 0.06 mGy can be achieved when image manipulation is used for detection of lesions in the mediastinum.  Both clarity and detectability in the mediastinum improved by between 48 to 66% with image manipulation.  Abdominal images showed a significant difference at 2.69 mGy for the soft tissue area, suggesting caution in further dose reduction.  Image quality in the spinal area was improved significantly by 21 – 78.6% (for clarity) and 3 to 77% (for detectability) when image manipulation was employed. Comparatively, the image quality at the low doses studied was better for the film screen radiography than both processed and unprocessed CR images suggesting that low doses achieved in FSR may not be applicable to CR.  This difference may be attributed to the differences in the image receptors’ response to high photon energies, and the reduced number of x-ray quanta which produce lower subject contrast in FSR and reduced signal to noise ratio (SNR) as a result of increased noise in CR. Nigerian clay in its natural and salted forms cannot be used in radiation dosimetry in diagnostic radiology.  Paraffin wax/MgSO<sub>4</sub>.6H<sub>2</sub>0, and rice-gelatine (<i>rigel</i>) combinations as well as rice and gelatine used separately, have shown tissue equivalent x-ray attenuation at tube potentials above 80 kVp.  Paraffin wax/MgSO<sub>4</sub>.6H<sub>2</sub>0 and <i>rigel </i>can therefore be used as tissue substitutes.  Low patient entrance surface doses achieved in FSR may not produce equivalent image quality when applied to imaging with CR systems.  With respect to dose reduction, both modalities show the possibility of further dose reduction below current dose values by about 40% (chest) and 20% (abdomen), respectively, when used alone.
Date January 2008
CreatorsEgbe, Nneoyi Onen
PublisherUniversity of Aberdeen
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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