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Showing 2 results for Image-Guided Radiotherapy
M. Zehtabian, R. Faghihi, Dr. M.a. Mosleh-Shirazi, A.r. Shakibafard, M. Mohammadi, M. Baradaran-Ghahfarokhi, Volume 10, Issue 2 (9-2012)
Abstract
Background: The aim of this work was to study the
feasibility of constructing a fast thorax model suitable
for simulating lung motion due to respiration using
only one CT dataset. Materials and Methods: For
each of six patients with different thorax sizes, two
sets of CT images were obtained in single-breath-hold
inhale and exhale stages in the supine position. The
CT images were then analyzed by measurements of
the displacements due to respiration in the thorax
region. Lung and thorax were 3D reconstructed and
then transferred to the ABAQUS software for
biomechanical fast finite element (FFE) modeling. The
FFE model parameters were tuned based on three of
the patients, and then was tested in a predictive
mode for the remaining patients to predict lung and
thorax motion and deformation following respiration.
Results: Starting from end-exhale stage, the model,
tuned for a patient created lung wall motion at
end-inhale stage that matched the measurements for
that patient within 1 mm (its limit of accuracy). In the
predictive mode, the mean discrepancy between the
imaged landmarks and those predicted by the model
(formed from averaged data of two patients) was 4.2
mm. The average computation time in the fast predictive
mode was 89 sec. Conclusion: Fast prediction of
approximate, lung and thorax shapes in the respiratory
cycle has been feasible due to the linear elastic
material approximation, used in the FFE model. Iran.
J. Radiat. Res., 2012 10(2): 73‐81
K. Venkatesan, C.j. Raphael, K.m. Varghese, P. Gopu, S. Sivakumar, M. Boban, N.a.n. Raj, K. Senthilnathan, Ph.d., P. Ramesh Babu, Volume 18, Issue 3 (7-2020)
Abstract
Background: To study and analyze the variations in delivered doses to rectum and bladder of carcinoma prostate patients by using kilo Voltage (kV) ‘Cone Beam Computed Tomography’ (CBCT) images. Materials and Methods: 2-Dimensional kilo Voltage (2D kV) Imaging and CBCT were done for seven prostate cancer patients. The deviations among their shifts were correlated and the volumetric changes of the rectum and bladder were analyzed. Rectum and bladder contours were redrawn on every boost fractions and dose calculation were performed on CBCT images to study the effect on dose volume histograms. Results: A correlation coefficient for set-up variations was within 0.78 for all directions between CBCT soft tissue matching and kV bone match. The mean deviation of bladder and rectum volume over the boost fractions was -12% to +9% (SD 31cc to 70cc) and -10.2% to+12% (SD 3.1cc to14.9cc), respectively. Bladder mean dose variation was <1.5Gy for all three positions whereas it was <3.65Gy for rectum. D1% dose deviation from reference plan for bladder was 1.1Gy (CBCT matched position), 1.4Gy (kV matched position), and 1.7Gy (no correction), and for rectum, the deviations were 1.2Gy, 2.2Gy, 3.6Gy, respectively. No significant deviation was found statistically significant at the low dose region. Conclusion: It is possible to achieve good dose delivery and conformity in target (prostate) with CBCT image guidance rather than kV bone match, but dose contribution to the rectum is dependent on the patient’s anatomy, bladder filling, and rectum filling, pertaining to the day of examination.
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