A simulation-based method for evaluating geometric tests of a linac c-arm in quality control in radiotherapy.

PURPOSE: Assessment of the accuracy of geometric tests of a linac used in external beam therapy is crucial for ensuring precise dose delivery. In this paper, a new simulation-based method for assessing accuracy of such geometric tests is proposed and evaluated on a set of testing procedures. METHODS: Linac geometry testing methods used in this study are based on an established design of a two-module phantom. Electronic portal imaging device (EPID) images of fiducial balls contained in these modules can be used to automatically reconstruct linac geometry. The projection of the phantom modules fiducial balls onto the EPID detector plane is simulated for assumed nominal geometry of a linac. Then, random errors are added to the coordinates of the projections of the centers of the fiducial balls and the linac geometry is reconstructed from these data. RESULTS: Reconstruction is performed for a set of geometric test designs and it is shown how the dispersion of the reconstructed values of geometric parameters depends on the design of a geometric test. Assuming realistic accuracy of EPID image analysis, it is shown that for selected testing plans the reconstruction accuracy of geometric parameters can be significantly better than commonly used action thresholds for these parameters. CONCLUSIONS: Proposed solution has the potential to improve geometric testing design and practice. It is an important part of a fully automated geometric testing solution.

[Quality of life patients with sudden sensorineural hearing loss]. / Jakosc zycia chorych z naglym niedosluchem czuciowo-nerwowym.

AIM: The aim of this study was the assessment of the quality of life of patients suffering from SSNHL and treated in the Otolaryngology Ward of Regional Specialized Hospital in Slupsk between 2001 and 2010, who were interviewed at least one year after the end of treatment. MATERIAL AND METHODS: A test examination was carried out in the period between 1 September 2011 and 31 March 2012 in the group of patients previously treated for SSNHL in the Otolaryngology Ward of Regional Specialized Hospital in Slupsk. Sixty-one patients responded to an invitation in writing. Quality of life was measured using following questionnaires: WHOQOL-Bref and Cantril's ladder (questionnaire). RESULTS: A test carried out using a Cantril's questionnaire showed that the respondents assessed their quality of life as higher before they fell ill, compared to the period directly after they fell ill, in hope of improvement of their well being, although this hope was not as high as it was before they fell ill. These differences were statistically significant. As it was indicated by WHOQOL-Bref questionnaire, the condition did not influence the quality of life of the patients, however the patients reported a higher quality of life, when compared to the patients who did not observe hearing improvement (these differences were noticeable but considered statistically insignificant). CONCLUSIONS: The indicated ambiguous influence of the treatment of patients suffering from SSNHL on their quality of life demonstrates the need to continue such research.