The present paper reports an updated dosimetry of dental radiology since it presents the data relative to 7 radiological techniques. The doses to 9 organs were measured on a Randoman phantom using ...TLD (4 in each chosen cavity) for lenses, tongue, cervical vertebrae (C2), thyroid, ovaries, uterus and testes. The examinations were subsequently repeated after applying X-ray shields to the phantom. The main conclusions follow: a) local doses are never negligible but can be really high, especially for tongue (1.880 mGy), thyroid (1.011 mGy), and C2 (0.699 mGy); b) X-ray shields for lenses, ovaries, uterus and testes have proven to be unnecessary; in a more general context, X-ray shields should be evaluated by the Health Physics Dept., especially relative to radiation leaks from the X-ray tube. As for the thyroid, X-ray shields have proven very useful but can result in repeated acquisitions because of possible interference with the radiological image; c) technicians' risk, in the present experimental conditions, does not exceed the threshold values recommended by Italian laws. At any rate, the use of fixed or mobile shieldings should always be evaluated while keeping in mind the specific working conditions in radiology departments.
A quantitative analysis was performed of the CT images relative to 7 normal human subjects and to 22 patients affected with ARF (Acute Respiratory Failure). The CT scanner image quality was ...investigated, and the unit was checked with quality control procedures, in order to assure reliability and reproducibility. In every patient the lung was scanned at 3 different levels--basis, hilum and apex. The frequency distribution of CT numbers was studied. The lung areas were calculated for the different conditions, and the data correlated with functional lung data. A method was then tested to evaluate lung weight; the data obtained did not differ from literature data. All the patients were treated with different positive and expiratory pressure (PEEP). For different PEEP values, the quantitative data from CT analysis were correlated with morphofunctional indices.
CyberKnife can perform fiducial-free lung tracking, even when the target is visible from only one of the double imaging view, thanks to the Lung-Optimized-Treatment package. However, the uncertainty ...along the blind view (out-of-plane direction) must be taken into account in margin definition. The goal was to determine the accuracy of target localization in 1-view treatments (33% of all lung cases at Centro Diagnostico Italiano).
The actual tumor position, stored in logfiles from 2-view treatments, was projected using a geometric relation onto both image planes for each of 26 patients’ data. In the same plots exhale and inhale planned tumor positions, extracted from TPS and based on breath-hold TC, were novelty represented preserving metric with respect to imaging center. Actual vs. planned positions were compared through a home-made software in Matlab able to calculate also the extra-margin to estimated ITV which would have been necessary to cover the 95% of target positions for the 95% of patient population in case of 1-view treatment. The program was validated using data from 1-view and 2-view lung treatments with XLT Phantom (CIRS).
The validation test confirmed the reliability of the technique. Expansions were equal to 5 mm and 7 mm for lesions in superior and inferior lobe respectively. The method proved to overestimate margins due to imaging sampling algorithm, data dependence on 2-view cases and the small amount of patients. However, results showed clearly that biphasic TC acquired in breath-hold way was rarely a good model for breath amplitude and breath center position in relation to spine alignment center.
This graphic comparison method is a useful tool to check localization accuracy of CyberKnife system for 1-view treatments and identify movement error components. It could be employed in clinical workflow to get patient-related information for customized margin definition.▪
