Dersleri yüzünden oldukça stresli bir ruh haline sikiş hikayeleri bürünüp özel matematik dersinden önce rahatlayabilmek için amatör pornolar kendisini yatak odasına kapatan genç adam telefonundan porno resimleri açtığı porno filmini keyifle seyir ederek yatağını mobil porno okşar ruh dinlendirici olduğunu iddia ettikleri özel sex resim bir masaj salonunda çalışan genç masör hem sağlık hem de huzur sikiş için gelip masaj yaptıracak olan kadını gördüğünde porn nutku tutulur tüm gün boyu seksi lezbiyenleri sikiş dikizleyerek onları en savunmasız anlarında fotoğraflayan azılı erkek lavaboya geçerek fotoğraflara bakıp koca yarağını keyifle okşamaya başlar


The Use of Cone Beam Computed Tomography in Image-Guided Radiotherapy | OMICS International
OMICS Journal of Radiology
Make the best use of Scientific Research and information from our 700+ peer reviewed, Open Access Journals that operates with the help of 50,000+ Editorial Board Members and esteemed reviewers and 1000+ Scientific associations in Medical, Clinical, Pharmaceutical, Engineering, Technology and Management Fields.
Meet Inspiring Speakers and Experts at our 3000+ Global Conferenceseries Events with over 600+ Conferences, 1200+ Symposiums and 1200+ Workshops on Medical, Pharma, Engineering, Science, Technology and Business

The Use of Cone Beam Computed Tomography in Image-Guided Radiotherapy

Dandan Zheng*
Department of Radiation Oncology, University of Nebraska Medical Center, 42nd and Emile, Omaha, NE 68198, USA
Corresponding Author : Dandan Zheng
Department of Radiation Oncology
University of Nebraska Medical Center
42nd and Emile, Omaha
NE 68198, USA
Tel: 530-219-0423
Received March 19, 2012; Accepted March 22, 2012; Published March 25, 2012
Citation: Zheng D (2012) The Use of Cone Beam Computed Tomography in Image- Guided Radiotherapy. Radiol Open Access. 1:e104. doi: 10.4172/2167-7964.1000e104
Copyright: © 2012 Zheng D, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Visit for more related articles at OMICS Journal of Radiology



In the past few decades, three-dimensional (3D) virtual simulation with computed tomography enabled more focused radiotherapy delivery such as intensity-modulated radiotherapy (IMRT), which delivers high dose to the target while simultaneously sparing nearby critical tissues. More recently, image guidance at the treatment sessions further promoted these advances in ensuring accurate localization of the target and reducing required setup margins. Cone beam computed tomography (CBCT), especially, has played an increasingly important role in contemporary image-guide radiotherapy (IGRT). With either megavoltage (MV) or kilovoltage (kV) x-rays, CBCT is so named because it utilizes a two-dimensionally collimated rectangular or cone-shaped beam and a flat-panel detector (FPD). It provides softtissue detectability for more precise target localization, and generates 3D images capable of treatment adaptation. New advances in CBCT technology correlate the images with respiration, enable image acquisition during the treatment, further improve the image quality, and reduce the imaging dose. Therefore, this important imaging modality has gained enormous popularity and is quickly replacing 2D based IGRT.
The two main categories of CBCT used in IGRT are MV CBCT, which uses the treatment beam and an opposing FPD, and kV CBCT, which uses a kV source and an FPD mounted perpendicular to the treatment beam on the gantry [1,2]. Although with sub-optimal beam energy for imaging, MV CBCT requires fewer hardware components and has advantages in imaging patients with metal prosthesis. On the other hand, kV CBCT enjoys distinctly better image-quality and better dose tradeoff, therefore finds wider applications in IGRT.
Currently, the most prevalent clinical application is for patient setup. CBCT in-room imaging allows accurate inter- and intrafraction target localization. Studies have demonstrated the feasibility of using CBCT-based patient setup to replace fiducial markers [3], immobilization frames [4], and reduce the setup margins for many anatomical sites including lung, prostate, head-and-neck, etc. [5-7]. A great example is body stereotactic radiotherapy of the lung: CBCT image guidance has substantially improved inter- and intra-fraction target positioning and reduced required treatment margins.
Another advanced utilization of CBCT is for treatment adaptation. During the treatment course, patient may have inter-fractional and intra-fractional anatomy changes, such as tumor shrinkage and patient weight-loss often seen in head-and-neck cancer, target deformation prominent in prostate and uterine cancers, and respiratory-correlated target motion present in lung, liver, and pancreas cancers. There has been a paradigm change from the single plan treatment that is based only on the static planning CT, to adaptive radiotherapy that incorporates the above variables and adapts the treatment accordingly. Treatment fraction CBCT provides the most convenient and “realtime” 3D images for plan adaptation, resulting in the delivered treatments that are truly optimized throughout the treatment course [8-11]. Furthermore, new CBCT acquisition techniques have been devised to incorporate the breathing motion, such as respiratorycorrelated or 4D, gated, and breath-hold acquisitions [12,13]. These advanced images are used for analyzing inter- and intra-fractional motion for thoracic tumors, and for delivering gated, or 4D-adaptive treatments [14].
Thus far, CBCT has mostly been acquired prior to the treatment for IGRT. With increasing utilization of the volumetric modulated arc therapy (VMAT), simultaneous CBCT acquisition during the VMAT delivery has also been investigated [15].
Despite its vast applications and important potentials in IGRT, CBCT is also criticized for the sub-optimal image quality and for the ionization radiation dose. Going hand-in-hand with the intense research efforts to further expand the CBCT applications in IGRT, research on perfecting the technology and reducing/optimizing the imaging dose [16], is therefore important in making the best of this prominent technology.


Post your comment

Share This Article

Recommended Journals

Article Usage

  • Total views: 14522
  • [From(publication date):
    March-2012 - Jul 13, 2024]
  • Breakdown by view type
  • HTML page views : 10097
  • PDF downloads : 4425