A Monte Carlo study of organ and effective doses of cone beam computed tomography (CBCT) scans in radiotherapy

Cone-beam CT (CBCT) scans utilised for image guided radiation therapy (IGRT) procedures have become an essential part of radiotherapy. The aim of this study was to assess organ and effective doses resulting from new CBCT scan protocols (head, thorax, and pelvis) released with a software upgrade of the kV on-board-imager (OBI) system. Organ and effective doses for protocols of the new software (V2.5) and a previous version (V1.6) were assessed using Monte Carlo (MC) simulations for the International Commission on Radiological Protection (ICRP) adult male and female reference computational phantoms. The number of projections and the mAs values were increased and the size of the scan field was extended in the new protocols. Influence of these changes on organ and effective doses of the scans was investigated. The OBI system was modelled in EGSnrc/BEAMnrc, and organ doses were estimated using EGSnrc/DOSXYZnrc. The MC model was benchmarked against experimental measurements. Organ dos...
Source: Journal of Radiological Protection - Category: Physics Authors: Source Type: research

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Jalil Ur Rehman, Muhammad Isa, Nisar Ahmad, Gulfam Nasar, H M. Noor Ul Huda Khan Asghar, Zaheer Abbas Gilani, James C. L. Chow, Muhammad Afzal, Geoffrey S IbbottJournal of Medical Physics 2018 43(2):129-135This analysis estimated secondary cancer risks after volumetric modulated arc therapy (VMAT) and compared those risks to the risks associated with other modalities of head-and-neck (H&N) radiotherapy. Images of H&N anthropomorphic phantom were acquired with a computed tomography scanner and exported via digital imaging and communications in medicine (DICOM) standards to a treatment planning system. Treatment plan...
Source: Journal of Medical Physics - Category: Physics Authors: Source Type: research
Selective internal radiation therapy using 90Y spheres is a treatment option for patients with primary or secondary liver cancer. To avoid complications, screening using 99mTc macroaggregated albumin is performed to identify lung shunting and extrahepatic depositions. For the latter, deposition after the anterior abdominal wall is frequently attributed to a patent falciform artery, although the vessel itself is rarely visible on SPECT/CT scans. We demonstrate that retrospective SPECT/MRI fusion clearly attributes the nuclide accumulation to a patent falciform artery. During selective internal radiation therapy, ice packs w...
Source: Clinical Nuclear Medicine - Category: Nuclear Medicine Tags: Interesting Images Source Type: research
In this study, the experiments carried out on a multi-layer computational phantom, and a thorax geometry, show that by applying our method on a coarse mesh, we offer a better dose distribution inside the tumor compared to other density mapping methods, in the same level of detail. This is due to the reduction of the water equivalent path length error from 9.65 $mm$ to 0.62 $mm$ in the case the multi-layer phantom, and from 2.42 $mm$ to 0.48 $mm$ for the thorax geometry. Moreover, a similar dose coverage is obtained with refined tetrahedral meshes. As a consequence of the reduction of the number of tetrahedrons, computation...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research
Conclusion: Findings of the present study showed that if the density and homogeneity of the low-density polymer gel dosimeters are equal to those of the normal lung tissue, it may be used to measure the three dimensional dose distributions in lung tissue during radiation therapy.
Source: Journal of Cancer Research and Therapeutics - Category: Cancer & Oncology Authors: Source Type: research
Conclusion: Nonspecific respiratory symptoms should raise concern for PH and diffuse PEMH in patients with advanced-stage MF. Combined Tc-99m SC BM scintigraphy and SPECT/CT is a promising noninvasive imaging tool to diagnose this rare clinical entity. PMID: 29884685 [PubMed - as supplied by publisher]
Source: Journal of Nuclear Medicine Technology - Category: Nuclear Medicine Tags: J Nucl Med Technol Source Type: research
Surgery is the gold standard treatment for operable patients with stage Ⅰ or Ⅱ non-small lung cancer (NSCLC) [1]. Stereotactic Body Radiation Therapy (SBRT) is an alternative treatment option for non-surgical T1-2N0 NSCLC patients [2–4]. Recent studies shows that non-surgical patients with stage Ⅰ NSCLC can be treated by SBRT with reasonable local control [5–7 ]. NSCLC with confirmed nodal metastasis (N1 or N2 disease) is usually an exclusion for SBRT. Nodal statuses are first assessed by radiological examination such as computed tomography (CT) and/or F-fluoro-2-deoxy-d-glucose (FDG)-positron emission tomography (PET).
Source: Lung Cancer - Category: Cancer & Oncology Authors: Source Type: research
si E, Szabó D, Müllner K, Varga Z, Maráz A Abstract The presence of normal tissues in the irradiated volume limits dose escalation during pelvic radiotherapy (RT) for prostate cancer. Supine and prone positions on a belly board were compared by analyzing the exposure of organs at risk (OARs) using intensity modulated RT (IMRT). The prospective trial included 55 high risk, localized or locally advanced prostate cancer patients, receiving definitive image-guided RT. Computed tomography scanning for irradiation planning was carried out in both positions. Gross tumor volume, clinical and planning ta...
Source: Pathology Oncology Research - Category: Pathology Authors: Tags: Pathol Oncol Res Source Type: research
AbstractLinear scaling is used to convert raw computed tomography (CT) pixel values into Hounsfield units corresponding to different tissue values. Analysis of a benchmarking study, presented here, where the same CT scan was imported into and then exported from multiple radiotherapy treatment planning systems, found inconsistencies in HU scaling parameter values exported along with the images, particularly when images were exported using the Radiation Therapy Oncology Group format. Several methods of estimating conversion parameters, based on estimating pixel values corresponding to air and water within the image, for pelv...
Source: Australasian Physical and Engineering Sciences in Medicine - Category: Biomedical Engineering Source Type: research
odin NP Abstract BACKGROUND AND PURPOSE: The purpose of this study was to investigate whether treatment information from medical records can be used to estimate radiation doses to heart and lungs retrospectively in pediatric patients receiving spinal irradiation with conventional posterior fields. MATERIAL AND METHODS: An algorithm for retrospective dosimetry in children treated with spinal irradiation was developed in a cohort of 21 pediatric patients with available CT-scans and treatment plans. We developed a multivariable linear regression model with explanatory variables identifiable in case note review f...
Source: Radiotherapy and Oncology : journal of the European Society for Therapeutic Radiology and Oncology - Category: Radiology Authors: Tags: Radiother Oncol Source Type: research
Abstract Deformable image registration (DIR) is the key process for contour propagation and dose accumulation in adaptive radiation therapy (ART). However, currently, ART suffers from a lack of understanding of "robustness" of the process involving the image contour based on DIR and subsequent dose variations caused by algorithm itself and the presetting parameters. The purpose of this research is to evaluate the DIR caused variations for contour propagation and dose accumulation during ART using the RayStation treatment planning system. Ten head and neck cancer patients were selected for retrospective s...
Source: Journal of Applied Clinical Medical Physics - Category: Physics Authors: Tags: J Appl Clin Med Phys Source Type: research
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