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Towards optimization in digital chest radiography using Monte Carlo modelling
Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.ORCID-id: 0000-0003-3352-8330
Joint Department of Physics, The Royal Marsden NHS Foundation Trust and Institute of Cancer Research, London, UK.
Joint Department of Physics, The Royal Marsden NHS Foundation Trust and Institute of Cancer Research, London, UK.
Vise andre og tillknytning
2006 (engelsk)Inngår i: Physics in medicine and biology, ISSN 0031-9155, Vol. 51, nr 11, s. 2729-2743Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A Monte Carlo based computer model of the x-ray imaging system was used to investigate how various image quality parameters of interest in chest PA radiography and the effective dose E vary with tube voltage (90–150 kV), additional copper filtration (0–0.5 mm), anti-scatter method (grid ratios 8–16 and air gap lengths 20–40 cm) and patient thickness (20–28 cm) in a computed radiography (CR) system. Calculated quantities were normalized to a fixed value of air kerma (5.0 µGy) at the automatic exposure control chambers. Soft-tissue nodules were positioned at different locations in the anatomy and calcifications in the apical region. The signal-to-noise ratio, SNR, of the nodules and the nodule contrast relative to the contrast of bone (C/CB) as well as relative to the dynamic range in the image (Crel) were used as image quality measures. In all anatomical regions, except in the densest regions in the thickest patients, the air gap technique provides higher SNR and contrast ratios than the grid technique and at a lower effective dose E. Choice of tube voltage depends on whether quantum noise (SNR) or the contrast ratios are most relevant for the diagnostic task. SNR increases with decreasing tube voltage while C/CB increases with increasing tube voltage.

sted, utgiver, år, opplag, sider
2006. Vol. 51, nr 11, s. 2729-2743
HSV kategori
Identifikatorer
URN: urn:nbn:se:liu:diva-13219DOI: 10.1088/0031-9155/51/11/003OAI: oai:DiVA.org:liu-13219DiVA, id: diva2:18072
Tilgjengelig fra: 2008-04-28 Laget: 2008-04-28 Sist oppdatert: 2015-03-20
Inngår i avhandling
1. Quantifying image quality in diagnostic radiology using simulation of the imaging system and model observers
Åpne denne publikasjonen i ny fane eller vindu >>Quantifying image quality in diagnostic radiology using simulation of the imaging system and model observers
2008 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Accurate measures of both clinical image quality and patient radiation risk are needed for successful optimisation of medical imaging with ionising radiation. Optimisation in diagnostic radiology means finding the image acquisition technique that maximises the perceived information content and minimises the radiation risk or keeps it at a reasonably low level. The assessment of image quality depends on the diagnostic task and may in addition to system and quantum noise also be hampered by overlying projected anatomy.

The main objective of this thesis is to develop methods for assessment of image quality in simulations of projection radiography. In this thesis, image quality is quantified by modelling the whole x‐ray imaging system including the x‐ray tube, patient, anti‐scatter device, image detector and the observer. This is accomplished by using Monte Carlo (MC) simulation methods that allow simultaneous estimates of measures of image quality and patient dose. Measures of image quality include the signal‐to‐noise‐ratio, SNR, of pathologic lesions and radiation risk is estimated by using organ doses to calculate the effective dose. Based on high‐resolution anthropomorphic phantoms, synthetic radiographs were calculated and used for assessing image quality with model‐observers (Laguerre‐Gauss (LG) Hotelling observer) that mimic real, human observers. Breast and particularly chest imaging were selected as study cases as these are particularly challenging for the radiologists.

In chest imaging the optimal tube voltage in detecting lung lesions was investigated in terms of their SNR and the contrast of the lesions relative to the ribs. It was found that the choice of tube voltage depends on whether SNR of the lesion or the interfering projected anatomy (i.e. the ribs) is most important for detection. The Laguerre‐Gauss (LG) Hotelling observer is influenced by the projected anatomical background and includes this into its figure‐of‐merit, SNRhot,LG. The LG‐observer was found to be a better model of the radiologist than the ideal observer that only includes the quantum noise in its analysis. The measures of image quality derived from our model are found to correlate relatively well with the radiologist’s assessment of image quality. Therefore MC simulations can be a valuable and an efficient tool in the search for dose‐efficient imaging systems and image acquisition schemes.

sted, utgiver, år, opplag, sider
Institutionen för medicin och hälsa, 2008
Serie
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1050
Emneord
radiology, radiation physics, image quality, optimisation, effective dose, chest radiography
HSV kategori
Identifikatorer
urn:nbn:se:liu:diva-11662 (URN)9789173939522 (ISBN)
Disputas
2008-05-09, Eken, Campus US, Linköpings universitet, Linköping, 09:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2008-04-28 Laget: 2008-04-28 Sist oppdatert: 2017-12-15

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