Contribution of the Department of Medical Physics of the University of Crete
University of Crete (UoC) is responsible for the development of a novel patient-specific and equipment-specific method to accurately estimate patient organ doses from chest CT. The aim was to develop a modular innovative software tool that will provide image quality information, accurate estimation of patient organ doses and estimation of radiogenic risk associated with chest CT examinations performed for several clinical indications.
UoC subtask 2.1.2 developed a method for the accurate estimation of dose to primarily irradiated organ structures (bones, oesophagus, breast (female), heart, lungs, skin in pediatric and adult CT examinations) by considering patient size, automatic tube current modulation and specific CT-scanner characteristics with the use of patient-specific computational models. The developed method for scanner-specific and patient-specific organ-dose estimation and optimization, is based on a procedure that combines Monte Carlo computational techniques and patient CT scans. The method consists of five steps: (a) collection of suitable patient CT scans; (b) determination of scanner parameters; (c) Monte Carlo (MC) dosimetric computations; (d) three-dimensional (3D) patient-specific dose distribution output and (e) correlation between dose and patient characteristics.
Figure 1: Graphical representation of right lung contours overlaid on corresponding dose slices.
The proposed method has several advantages: 1) Patient models were used instead of phantoms and, therefore, results are based on true patient-specific dosimetry, 2) Strong correlations between normalized doses and patient WED ensure that highly accurate organ dose estimations are observed, and 3) the method is applicable to both adult and pediatric patients undergoing chest CT examinations.
The dosimetric data were used to develop and deploy a web-based tool (CTRAD) capable of estimating organ radiation doses quickly and accurately. Personalized Computed Tomography Organ Dose Estimation Tool (Abbrev. CTRAD) will be installed at http://medphys-tools.med.uoc.gr and is available upon free user registration (currently under construction and testing).
Moreover, UoC contributes to the development of a method to determine image quality combining state-of-the-art objective and subjective image analysis in chest CT. The final aim is to develop a modular application that will provide image quality information, accurate estimation of patient organ doses and estimation of radiogenic risk associated with chest CT examinations performed for several clinical indications.
The UoC also collaborates on setting up and populating a repository of absorbed doses with associated image and anonymised patient data for access by any member of the consortium.
These findings will be valuable not only for dose optimization but also for justification of CT examinations (benefit vs. risk analysis). Using data produced we will provide estimates of radiation-induced cancer risk from CT scan exposure in childhood, adolescence and adulthood, of primary importance for risk communication. Accurate organ dose data together with appropriate risk models will be very useful to assess the health impact associated with CT chest examinations. Moreover, a tool for chest CT procedures optimisation will contribute to a more robust system of radiation protection of patients undergoing chest CT examinations.
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