Abstract Book

S1142

ESTRO 37

Different outcomes were assessed with a Mantel-Cox test in SPSS 20 (IBM, USA). Statistical significance was set at p < 0.05. A Cox regression was used for the clinical data evaluation of survival. In addition to (I abs ) minimum , (I abs ) mean , (I abs ) maximum , and (I abs )σ, several dummy variables were included: T2 and T3 vs. T1, N2 and N3 vs. N1 and N0, conventional vs. hypofractionated radiotherapy, and squamous cell carcinoma, metastasis, and small cell lung cancer vs. adenocarcinoma. Results The mean survivorship of the cohort was 780 ± 60 days (95% level of confidence: 663-1371 days)

enables the tissue segmentation. In our work, we created a contrast medium extraction method using rED and CT number from DECT for the automatic delineation of the contrast region. Material and Methods A CT-ED phantom which contains tissue-equivalent inserts and an acrylic phantom which contains inserts with the various concentrations (0-130 mg/mL), of iodinated contrast medium were scanned by DECT. CT scans were performed at tube voltages of 80/135 kV and 100/135 kV. Contrast medium was separated from other tissue materials by using the threshold of CT number and the difference of the gradient in the rED-CT correlation, which was analyzed in an in-house software. The accuracy of the contrast medium extraction was evaluated by measuring the diameter in terms of the full width at half maximum (FWHM), and the ratio of the volume (ROV).

Results The CT number of the bone materials and the contrast medium was obviously greater than 0 HU. CT number of only bone materials and contrast medium obtained by 80 kV and 100 kV is higher than that by 135 kV. The gradient of the bone materials was greater than that of the contrast medium. The ratio of the measurement to the actual diameter in FWHM and the ROV was 0.98-1.00 at more than 2 mg/mL. At tube voltage of 100/135 kV, the ratio of the measurement to the actual diameter in FWHM and the ROV was 0.98-1.00 at more than 3 mg/mL.

(I abs ) mean lung lesion for a threshold set at percentile 25% (I abs ) threshold = 21.68 mg/cm 3 was the only parameter that distinguished significantly (p = 0.012) sub-cohorts according to their global survivorship. (I abs ) mean , (I abs ) maximum and squamous cell carcinoma were significant in the Cox regression model. Table 1 shows the values of β, significance, exp(β), and its 95% confidence level (C.L.) for the Cox regression of these covariables.

Conclusion (I abs

) in the lung lesion quantified by DECT reflects probably a process of angiogenesis and is related to patient survivorship. EP-2081 Contrast medium extraction method using raw-data based electron density with Dual energy-CT D. Kawahara 1 , T. Sodai 2 , O. Shuichi 3 , Y. Kazushi 4 , H. Toru 5 , F. Chikako 4 , S. Akito 3 , N. Takeo 4 , O. Yoshimi 4 , N. Yasushi 3 1 Hiroshima University, Graduate School of Biomedical & Health Sciences, Hiroshima, Japan 2 University of Tokyo, Department of Nuclear Engineering and Management- School of Engineering, Tokyo, Japan 3 Hiroshima University, Department of Radiation Oncology- Institute of Biomedical & Health Sciences, Hiroshima, Japan 4 Hiroshima University Hospital, Division of Clinical Support, Hiroshima, Japan 5 Hiroshima University, Departments of Diagnostic Radiology and Radiology, Hiroshima, Japan Purpose or Objective Dual-energy CT (DECT) obtains various data of scanned materials such as raw-data based electron density (rED) and CT value and effective atomic number, which

Conclusion We created the contrast medium extraction method and it is expected to extract only the region of the contrast medium from patient CT image using it. EP-2082 The effect of zinc in prostatic calculi on the accuracy of the MBIR algorithm DIRA A. Malusek 1 , M. Magnusson 2 , M. Sandborg 1 , G. Alm Carlsson 1 , A. Carlsson Tedgren 1 1 Linköping University, Radiological Sciences, Linköping, Sweden 2 Linköping University, Electrical Engineering, Linköping, Sweden Purpose or Objective Absorbed dose distributions in brachytherapy of prostate with low energy photons are affected by prostate calcifications. The calcifications shield the photon beams and may produce cold spots in spatial distributions of absorbed dose. Unlike breast calcifications, where the high atomic number elements are mainly represented by calcium, prostate calcifications may also contain several percent of zinc and smaller amount of strontium and iron. Some modern radiation treatment planning (RTP) systems can, in principle, take these inhomogeneities