Using the flat panel detector on linac for the kV X-ray generator test

On-board imaging (OBI) system have been introduced in the last two decades to assist in patient setup and increase the accuracy of radiation treatment deliveries. The kV OBI system usually consists of an X-ray tube and a flat panel detector. As image-guided radiation therapy (IGRT) has been widely applied and rapidly integrated in the routine clinical workflow of radiation oncology, majority of newly manufactured linacs are equipped with OBI systems. Outstanding performance of this system is required to ensure high accuracy in tumor localization and tracking. Therefore, a comprehensive quality assurance (QA) program for this system is critical. In this study, we propose and evaluate a novel approach utilizing the flat panel detector available on the machine to perform the X-ray generator test via XML-controlled image acquisition and advanced imaging analysis.

  • Bin Cai, Steven Dolly, Gregory Kamal, Sridhar Yaddanapudi, Baozhou Sun, S Murty Goddu, Sasa Mutic, Hua Li*, “A Feasibility Study of Using the Flat Panel Detector on LINAC for the kV X-ray Generator Test”, Medical Physics, 2018, In Press.

iDose4 iterative CT reconstruction for radiation therapy

This study is to evaluate the commercial released Philips iDose4 iterative reconstruction technique from the radiotherapy endpoints, compare it to the traditional filter back-projection (FBP) reconstruction technique, and ultimately provide clinical practice suggestions on its usage in radiation therapy.

Contrast-enhanced CT simulations in radiation therapy

Intravenous (IV) iodine contrast-enhanced CT simulations are commonly used in thoracic radiation therapy, greatly facilitating both tumor and normal tissue segmentation, particularly in the mediastinum 1-3. However, IV contrast agents increase the CT-imaging linear attenuation coefficients and the subsequent electron densities in the contrast-enhanced regions are erroneously assigned. This raises the concern that the erroneous assigned electron density variations may cause the dose distribution calculation to have clinically relevant errors. In this study, we investigated the severity of CT Hounsfield number (HU) variations on the contrast-affected regions (such as heart), and evaluated the effects of using IV contrast-enhanced CT simulation scans on radiation dosimetry through complete PTV and OAR dose difference analysis and γ passing rate comparisons. The magnitude of potential dose errors and their clinical significance for lung cancer radiation therapy treatments were determined as well.

Clinical evaluation of a commercial O-MAR tool in radiation therapy

Severe artifacts in kilovoltage-CT simulation images caused by large metallic implants can significantly degrade the conspicuity and apparent CT Hounsfield number of targets and anatomic structures, jeopardize the confidence of anatomical segmentation, and introduce inaccuracies into the radiation therapy treatment planning process. This study evaluated the performance of the first commercial orthopedic metal artifact reduction function (O-MAR) for radiation therapy, and investigates its clinical applications in treatment planning.

Clinical evaluation of a novel amplitude-based binning algorithm for 4D CT reconstruction

Phase binning algorithms are commonly utilized in 4DCT image reconstruction for characterization of tumor or organ shape and respiration motion but breathing irregularities occurring during 4DCT acquisition can cause considerable image distortions. Recently, amplitude-binning algorithms have been evaluated as a potential improvement to phase binning algorithms for 4DCT image reconstruction. The purpose of this study was to evaluate the performance of the first commercially available on-line retrospective amplitude binning algorithm for comparison to the traditional phase binning algorithm.