Synthesized effective atomic numbers for commercially available dual-energy CT.

Purpose: The objective of this study was to assess synthesized effective atomic number (Z) values with a new developed tissue characteristic phantom and contrast material of varying iodine concentrations using single-source fast kilovoltage switching dual-energy CT (DECT) scanner.

Methods: A newly developed multi energy tissue characterisation CT phantom and an acrylic phantom with various iodine concentrations of were scanned using single-source fast kilovoltage switching DECT (GE-DECT) scanner. The difference between the measured and theoretical values of Z were evaluated.

Risk factors for severe gastrointestinal toxicity in patients receiving palliative radiotherapy for metastatic bone tumors: association with the use of molecular-targeted agents.

This study aimed to investigate whether the use of molecular-targeted agents could affect gastrointestinal (GI) toxicity in palliative radiotherapy (RT) for metastatic bone tumors in the abdominopelvic region. We collected data of patients who received palliative RT for bone metastases in the abdominopelvic region between 2013 and 2014 from six institutions. Data of 395 patients were collected and184 patients received molecularly targeted therapy, of whom 80 received vascular endothelial growth factor (VEGF)-targeted agents.

Long-term outcomes of induction chemotherapy followed by chemoradiotherapy using volumetric-modulated arc therapy as an organ preservation approach in patients with stage IVA-B oropharyngeal or hypopharyngeal cancers.

The present study aimed to analyze treatment outcomes after induction chemotherapy followed by chemoradiotherapy (CRT) using volumetric-modulated arc therapy (VMAT) in patients with stage IVA-B oropharyngeal cancer (OPC) or hypopharyngeal cancer (HPC), with long-term observation, including examination of larynx preservation. A total of 60 patients with stage IVA-B OPC or HPC, who underwent induction TPF chemotherapy (a combination regimen consisting of docetaxel, cisplatin, and 5-fluorouracil) followed by CRT using VMAT were analyzed. Overall survival (OS), progression-free survival (PFS), laryngoesophageal dysfunction-free survival (LEDFS), and locoregional control (LRC) were calculated and compared.

Evaluation of metal artefact techniques with same contrast scale for different commercially available dual-energy computed tomography scanners.

The aim of our study is to evaluate the metal artefact reduction techniques with the same contrast scale for different vendors' dual-energy CT (DECT): kV-CT image with metal artefact reduction method and monoenergetic CT image using Canon's DECT, and monoenergetic CT image with metal artefact reduction method using GE's DECT. The kV-CT image and DECT scans were performed with the water-based polymethyl methacrylate phantom with various metal materials (brass, aluminium, copper, stainless steel, steel, lead, and titanium). Two types of metal artefact reduction (MAR) algorithm with the monoenergetic CT images were used.

Biological dose-enhancement analysis with Monte Carlo simulation for Lipiodol for photon beams.

Background: Previously, the physical dose-enhancement factor (DEF) enhancement was introduced. However, the dose enhancement considering the biological effectiveness was not shown.

Purpose: The aim of the current study was to evaluate the biological dose-enhancement factor (DEF) by the dose rate and to compare the DEF and the DEF in Lipiodol for liver Stereotactic Body Radiation Therapy (SBRT).

Effectiveness of robust optimization in volumetric modulated arc therapy using 6 and 10 MV flattening filter-free beam therapy planning for lung stereotactic body radiation therapy with a breath-hold technique.

We investigated the feasibility of a robust optimization with 6 MV X-ray (6X) and 10 MV X-ray (10X) flattening filter-free (FFF) beams in a volumetric modulated arc therapy (VMAT) plan for lung stereotactic body radiation therapy (SBRT) using a breath-holding technique. Ten lung cancer patients were selected. Four VMAT plans were generated for each patient; namely, an optimized plan based on the planning target volume (PTV) margin and a second plan based on a robust optimization of the internal target volume (ITV) with setup uncertainties, each for the 6X- and 10X-FFF beams.

Dose compensation based on biological effectiveness due to interruption time for photon radiation therapy.

Objective: To evaluate the biological effectiveness of dose associated with interruption time; and propose the dose compensation method based on biological effectiveness when an interruption occurs during photon radiation therapy.

Methods: The lineal energy distribution for human salivary gland tumor was calculated by Monte Carlo simulation using a photon beam. The biological dose (D) was estimated using the microdosimetric kinetic model.

Characterization of robust optimization for VMAT plan for liver cancer.

Purpose: We investigated the feasibility of robust optimization for volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) for liver cancer in comparison with planning target volume (PTV)-based optimized plans. Treatment plan quality, robustness, complexity, and accuracy of dose delivery were assessed.

Methods: Ten liver cancer patients were selected for this study.

[Improvement of Nonuniformity on Flatbed Scanner for Radiochromic Film Dosimetry Using Average Correction Factor with Multi-direction Scan Data].

In order to correct the lateral effect caused by the light source of the flatbed scanner in the Gafchromic film EBT3, the usefulness of the correction method using the average value of the correction coefficient considering the scan directions were evaluated. EBT3 was scanned from four directions to measure the optical density (OD) of the red, blue, and, red/blue components and the correction coefficient were calculated. For the correction coefficients, average values were calculated for the purpose of use, when the scan directions could not be aligned (average lateral effect correction).

An overview of stereotactic body radiation therapy for hepatocellular carcinoma.

: According to several guidelines, stereotactic body radiation therapy (SBRT) for early hepatocellular carcinoma (HCC) can be considered an alternative to other modalities, such as resection, radiofrequency ablation (RFA), and transarterial chemoembolization (TACE), or when these therapies have failed or are contraindicated. This article reviews the current status of SBRT for the treatment of HCC.: From the results of many retrospective reports, SBRT is a promising modality with an excellent local control of almost 90% at 2-3 years and acceptable toxicities.

Assessment of biological dosimetric margin for stereotactic body radiation therapy.

Purpose: To develop a novel biological dosimetric margin (BDM) and to create a biological conversion factor (BCF) that compensates for the difference between physical dosimetric margin (PDM) and BDM, which provides a novel scheme of a direct estimation of the BDM from the physical dose (PD) distribution.

Methods: The offset to isocenter was applied in 1-mm steps along left-right (LR), anterior-posterior (AP), and cranio-caudal (CC) directions for 10 treatment plans of lung stereotactic body radiation therapy (SBRT) with a prescribed dose of 48 Gy. These plans were recalculated to biological equivalent dose (BED) by the linear-quadratic model for the dose per fraction (DPF) of d = 3-20 Gy/fr and .

Imaging Cherenkov emission for quality assurance of high-dose-rate brachytherapy.

With advances in high-dose-rate (HDR) brachytherapy, the importance of quality assurance (QA) is increasing to ensure safe delivery of the treatment by measuring dose distribution and positioning the source with much closer intervals for highly active sources. However, conventional QA is time-consuming, involving the use of several different measurement tools. Here, we developed simple QA method for HDR brachytherapy based on the imaging of Cherenkov emission and evaluated its performance.

Evaluation of interbreath-hold lung tumor position reproducibility with vector volume histogram using the breath-hold technique.

Tumor geometric reproducibility for lung stereotactic body radiotherapy (SBRT) is an important issue in the breath-hold (BH) technique. We investigated the inter-BH reproducibility of the tumor position in expiratory BH using our proposed vector volume histogram (VVH) method. Subjects comprising 14 patients with lung cancer who were treated with lung SBRT under expiratory BH conditions were monitored by the Abches system.

Development of a CT number calibration audit phantom in photon radiation therapy: A pilot study.

Purpose: In photon radiation therapy, computed tomography (CT) numbers are converted into values for mass density (MD) or relative electron density to water (RED). CT-MD or CT-RED calibration tables are relevant for human body dose calculation in an inhomogeneous medium. CT-MD or CT-RED calibration tables are influenced by patient imaging (CT scanner manufacturer, scanning parameters, and patient size), the calibration process (tissue-equivalent phantom manufacturer, and selection of tissue-equivalent material), differences between tissue-equivalent materials and standard tissues, and the dose calculation algorithm applied; however, a CT number calibration audit has not been established.

A single institution experience of the treatment of pancreatic ductal carcinoma: The demand and the role of radiation therapy.

We aimed to demonstrate a single institution experience of treatment of pancreatic ductal carcinoma and to identify the role of radiation therapy. We assessed all patients who were diagnosed with pancreatic ductal carcinoma from January 2011 to December 2017. A total of 342 patients were enrolled.

Predictive gamma passing rate for three-dimensional dose verification with finite detector elements via improved dose uncertainty potential accumulation model.

Purpose: We aim to develop a method to predict the gamma passing rate (GPR) of a three-dimensional (3D) dose distribution measured by the Delta4 detector system using the dose uncertainty potential (DUP) accumulation model.

Methods: Sixty head-and-neck intensity-modulated radiation therapy (IMRT) treatment plans were created in the XiO treatment planning system. All plans were created using nine step-and-shoot beams of the ONCOR linear accelerator.

MRI appearance change during stereotactic radiotherapy for large brain metastases and importance of treatment plan modification during treatment period.

Purpose: We aimed to evaluate the magnetic resonance imaging (MRI) appearance changes during stereotactic radiotherapy (SRT) for large sized brain metastases, and analyze the lesions necessitating treatment plan modification.

Materials And Methods: A total of 23 patients (27 lesions, >2 cm in tumor diameter) underwent SRT and all lesions were evaluated the appearance changes which had the necessity of the treatment plan modification. The appearance change of tumor during SRT was evaluated using gadolinium-enhanced MRI.

Automatic gas detection in prostate cancer patients during image-guided radiation therapy using a deep convolutional neural network.

Purpose: The detection of intestinal/rectal gas is very important during image-guided radiation therapy (IGRT) of prostate cancer patients because intestinal/rectal gas increases the inter- and intra-fractional prostate motion. We propose a deep convolutional neural network (DCNN) to detect intestinal/rectal gas in the pelvic region.

Material And Methods: We selected 300 anterior-posterior kilo-voltage (kV) X-ray images from 30 prostate cancer patients.

Evaluation of raw-data-based and calculated electron density for contrast media with a dual-energy CT technique.

Objectives: The aim of the current study is to evaluate the accuracy and the precision of raw-data-based relative electron density (RED) and the calibration-based RED (RED) at a range of low-RED to high-RED for tissue-equivalent phantom materials by comparing them with reference RED (RED) and to present the difference of RED and RED for the contrast medium using dual-energy CT (DECT).

Methods: The RED images were reconstructed by raw-data-based decomposition using DECT. For evaluation of the accuracy of the RED, RED was calculated for the tissue-equivalent phantom materials based on their specified density and elemental composition.

Improving automatic contrast agent extraction system using monochromatic CT number.

In a previous study, a phantom study of a contrast agent extraction system with computed tomography (CT) number and raw-data-based electron density (ED) was described. The current study improved this system with monochromatic CT (mCT) number and evaluated an anthropomorphic phantom for delineation of the contrast-enhanced region. Dual-energy CT images were scanned with a tissue-equivalent phantom and an anthropomorphic phantom with an iodinated contrast agent (1-130 mg/mL).

Effect of image quality on correlation modeling error using a fiducial marker in a gimbaled linear accelerator.

The purpose of this study was to investigate the effect of image quality under various imaging parameters (60, 70, 80, 90, 100, 110, and 120 kV at 200 mA and 10 ms/63, 80, 100, 160, 200, 250, and 320 mA at 120 kV and 10 ms) and the diameter of the fiducial marker (0.25, 0.50, 0.

A novel risk analysis of clinical reference dosimetry based on failure modes and effects analysis.

Purpose: The output of a linear accelerator (linac) is one of the most important quality assurance (QA) factors in radiotherapy. However, there is no quantitative rationale for frequency and tolerance. The purpose of this study is to develop a novel risk analysis of clinical reference dosimetry based on failure modes and effects analysis (FMEA).

Volumetric modulated arc therapy with robust optimization for larynx cancer.

Purpose: The aim of this study was to perform a comparison between robust optimization and planning target volume (PTV)-based optimization plans using volumetric modulated arc-therapy (VMAT) by evaluating perturbed doses induced by localization offsets for setup uncertainties in larynx cancer radiation therapy.

Methods: Ten patients with early-stage (T1-2N0) glottis carcinoma were selected. The clinical target volume (CTV), carotid arteries, and spinal cord were contoured by a radiation oncologist.

Automatic calibration of an arbitrarily-set near-infrared camera for patient surface respiratory monitoring.

Purpose: A patient's respiratory monitoring is one of the key techniques in radiotherapy for a moving target. Generally, such monitoring systems are permanently set to a fixed geometry during the installation. This study aims to enable a temporary setup of such a monitoring system by developing a fast method to automatically calibrate the geometrical position by a quick measurement of calibration markers.