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Effect of the Small Field of View and Imaging Parameters to Image Quality and Dose Calculation in Adaptive Radiotherapy

Ubaidillah Allam, Fauzia Annisa Rahma, Purnomo Adi Teguh, Nasution Nuruddin, Wibowo Wahyu Edy, Pawiro Supriyanto Ardjo

Polish Journal of Medical Physics and Engineering

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2023

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Vol. 29, Iss. 2

130--142

EN

The use of cone beam computed tomography (CBCT) for dose calculation in adaptive radiotherapy has been investigated in many studies. Proper acquisition and reconstruction of preset parameters could improve the accuracy of dose calculation based on CBCT images. This study evaluated the impact of the modified image acquisition and preset reconstruction parameter available in X-Ray Volumetric Imaging (XVI) to improve CBCT image quality and dose calculation accuracy. Calibration curves were generated by scanning the CIRS phantom using CBCT XVI Elekta 5.0.4 and Computed Tomography (CT) Simulator Somatom, which served as CT image reference. Rando and Catphan 503 phantoms were scanned with various acquisition and reconstruction parameters for dose accuracy and image quality tests. The image quality test is uniformity, low contrast visibility, spatial resolution, and geometrical scale test for each image by following the XVI image quality test module. Acquisition and reconstruction parameters have an impact on the Hounsfield Unit (HU) value that is used as the HU-Relative Electron Density (RED) calibration curve. The dose difference for all the calibration curves was within 1% and passed the gamma passing rate. Images acquired using 120 kVp, F1 (with Bowtie Filter), and 50 mA (F1-120-50-10) scored the highest Gamma Index (GI) of 98.5%. For the image quality test, it scored 1.20% on the uniformity test, 2.14% on the low contrast visibility test, and 11 lp/cm on the spatial resolution test. However, F1-120-50-10 reconstructed with different reconstructions scored 3.83% and 4 lp/cm in contrast and spatial resolution test, respectively. CBCT reconstruction parameters work as a scatter correction. It could improve the dose accuracy and image quality. Nevertheless, without adequate CBCT acquisition protocols, it would produce an image with high uncertainty and cannot be fixed with reconstruction protocols. The F1-120-50-10 protocols generate the highest dose accuracy and image quality.

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Quality control test of cone beam computed tomography - constancy tests

Redutko J., Wrona K., Szarek A., Bańczyk Ł.

Journal of Achievements in Materials and Manufacturing Engineering

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2020

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Vol. 102, nr 2

66--75

EN

Purpose: The paper describes tests of CBCT cone beam scanners carried out to ensure projection quality. Design/methodology/approach: During the studies, phantoms were scanned with a leading brand volumetric CT scanner according to the device manufacturer's recommendations. The water phantom and phantom made of PMMA with materials of different radiological densities were used in the performed tests. The image area during the tests was determined as a cylinder with diameter of 80 mm and height of 90 mm. In turn, exposure parameters were selected on the basis of clinically applied protocols of cranial imaging. Within carried out research, tests of noise level were performed, image homogeneity was analysed and Hounsfield units constancy was determined. To this end, 18 quality control tests were analysed, which were performed at intervals of about 30 days. Images obtained during phantom scans were analysed by determining the Hounsfield value of selected areas and their changes over time. Findings: The analysis of all carried out projection quality control tests showed that they met the criteria set by the manufacturer, falling within the predefined value ranges. One of the performed tests presented results approaching the limit of acceptable values. After notifying this case, it was shown that the CT scanner was serviced during that period. The obtained results of the quality control tests of water phantom as well as of the material phantom imaging were maintained at similar levels after the service activities. No changes were observed in the obtained mean values of Hounsfield units, which would indicate a decrease in diagnostic quality of CBCT projections. Research limitations/implications: The results presented in this publication require further analysis. These should be complemented by incl. analyses of spatial resolution and image geometry. Practical implications: Carried out research has shown that cyclical quality control testing by a qualified operator is an essential activity to ensure high diagnostic quality of the device. In addition, this analysis showed that procedures of in-service tests should not be omitted and delayed. Originality/value: Originality in these tests is the possibility to improve the procedures for performing basic quality control tests.

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A rapid algebraic 3D volume image reconstruction technique for cone beam computed tomography

Al-masni M. A., Al-antari M. A., Metwally M. K., Kadah Y. M., Han S. M., Kim T. S.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 4

619--629

EN

Computed tomography (CT) is a widely used imaging technique in medical diagnosis. Among the latest advances in CT imaging techniques, the use of cone-beam X-ray projections, instead of the usual planar fan beam, promises faster yet safer 3D imaging in comparison to the previous CT imaging methodologies. This technique is called Cone Beam CT (CBCT). However, these advantages come at the expense of a more challenging 3D reconstruction problem that is still an active research area to improve the speed and quality of image reconstruction. In this paper, we propose a rapid parallel Multiplicative Algebraic Reconstruction Technique (rpMART) via a vectorization process for CBCT which gives more accurate and faster reconstruction even with a lower number of projections via parallel computing. We have compared rpMART with the parallel version of Algebraic Reconstruction Technique (pART) and the conventional non-parallel versions of npART, npMART and Feldkamp, Davis, and Kress (npFDK) techniques. The results indicate that the reconstructed volume images from rpMART provide a higher image quality index of 0.99 than the indices of pART and npFDK of 0.80 and 0.39, respectively. Also the proposed implementation of rpMART and pART via parallel computing significantly reduce the reconstruction time from more than 6 h with npART and npMART to 580 and 560 s with the full 360° projections data, respectively. We consider that rpMART could be a better image reconstruction technique for CBCT in clinical applications instead of the widely used FDK method.

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Three-dimensional finite element simulation of intrusion of the maxillary central incisor

Ryniewicz W., Ryniewicz A. M., Bojko Ł., Pełka P., Filipek J., Williams S., Loster B. W.

Biocybernetics and Biomedical Engineering

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2016

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Vol. 36, no. 2

385--390

EN

Purpose: The aim of this study is to generate a global digital model of treatment, analysis of stress distribution and displacements: in a construction of the bracket, in the incisor with bonded bracket, in tissues of the incisor, in a periodontal membrane and in an alveolus. Methods: An orthodontic therapy was provided with a three-dimensional model of a unique Cannon Ultra bracket. The placement of the bracket to the incisor was provided according to clinical standards. Composite material was placed between the rough surface of the bracket's base and labial incisor surface – which, in a digital model, resulted in contact without displacement. The bracket was loaded. An orthodontic arch wire was free to move in a wing slot of the bracket. For simplification, a force vector was parallel to the longitudinal axis of the incisor. A clamper was set on the surface of the cortical bone of the alveolus. The model was divided into a finite number of tetrahedral elements. To calculate the distribution of stress Ansys Workbench software was used. Results: The stress values indicate that there were no tissue overloaded areas. The stress distribution was regular in the periodontal ligament. Slight movements were observed with maximal values in the area of apex. Conclusions: This study simulation proves that tissues surrounding the tooth were influ-enced mechanically by the force loaded on the bracket. [...]