Publications by authors named "Kentaro Miki"

To establish an open framework for developing plan optimization models for knowledge-based planning (KBP).Our framework includes radiotherapy treatment data (i.e.

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  • The study aimed to develop a more accurate CT number-to-stopping power ratio calibration table for ion therapy using a new three-parameter fit model compared to the traditional method.
  • Researchers tested this by scanning eight tissue-equivalent materials with various CT scanners and evaluating the calibration tables for different tissue types like lung and cartilage.
  • Results showed that the new model provided better agreement with actual measurements, especially improving accuracy for low-density tissues such as lung.
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Background And Purpose: Currently, automatic approaches for radiotherapy planning are widely used, however creation of high quality treatment plans is still challenging. In this study, two independent dose prediction methods were used to personalize the initial settings for the automated planning template for optimizing prostate cancer treatment plans. This study evaluated the dose metrics of these plans comparing both methods with the current clinical automated prostate cancer treatment plans.

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In the preparation of intensity-modulated radiation therapy (IMRT), patient-specific verification is widely employed to optimize the treatment. To accurately estimate the accumulated dose and obtain the field-by-field or segment-by-segment verification, an original IMRT verification tool using scintillator light and an analysis workflow was developed in this study. The raw light distribution was calibrated with respect to the irradiated field size dependency and light diffusion in the water.

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Purpose: Lack of a reference dose distribution is one of the challenges in the treatment planning used in volumetric modulated arc therapy because numerous manual processes result from variations in the location and size of a tumor in different cases. In this study, a predicted dose distribution was generated using two independent methods. Treatment planning using the predicted distribution was compared with the clinical value, and its efficacy was evaluated.

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Purpose: Immune checkpoint proteins programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) are important therapeutic targets for head and neck cancer. This large-scale case study aimed to analyze tongue squamous cell carcinomas (SCCs) and evaluate the correlation between PD-L1 expression and clinical prognosis. So far, this study is the largest case study on PD-L1 expression in tongue SCCs.

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Background/aim: The present study aimed to analyze the treatment outcome after definitive radiotherapy (dRT) using volumetric-modulated arc therapy (VMAT) in patients with hypopharyngeal cancer (HPC), including an examination of late toxicities.

Patients And Methods: A total of 62 patients with HPC, who underwent dRT using VMAT, were analyzed. Overall survival (OS), progression-free survival (PFS), laryngoesophageal dysfunction-free survival (LEDFS), and locoregional control (LRC) were calculated.

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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.

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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.

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Background: Metastasis-associated in colon cancer 1 (MACC1) has been reported to be an independent indicator of poor prognoses in some kinds of cancer due to disease metastasis or recurrence. We investigated the correlation between MACC1 expression and the prognosis of glottic cancer.

Methods: Paraffin-embedded, early-stage (I or II) glottic cancer specimens (n = 52) were immunohistochemically analyzed to explore MACC1 expression.

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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.

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Article Synopsis
  • Computed tomography (CT) data is essential for calculating dose distribution in patients undergoing radiotherapy, with two key calibration methods being CT-RED (relative electron density) and CT-MD (mass density).
  • The previous study established tolerance levels for CT-RED calibration but did not have similar levels for CT-MD calibration, leading to this study that set those levels based on CT-RED data and conversion factors derived from ICRP-110.
  • Validation of the conversion methods showed that the differences in relative dose errors between CT-RED and CT-MD calibrations were minimal (less than 0.3% for each tissue type), and established tolerance levels for various tissue types, aiding in improving treatment accuracy.
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p16 (p16) expression in tongue cancer (TC) is reportedly not associated with human papilloma virus (HPV). Mutations of in cancer cells are most frequently observed within codon 12. However, few reports have investigated the association between mutations and p16 status in TC.

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Purpose: To determine optimal dose distribution in the treatment planning of volumetric modulated arc therapy (VMAT), a virtually ideal dose distribution was developed as a reference by applying filtered back-projection method.

Methods: Delineated structures in patient CT scans were identified using a treatment planning system. The projection of the planning target volume (PTV) was calculated along the X-ray direction for each angle of rotation.

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Background: Long-term smoking and drinking are known to contribute to the onset of tongue cancer (TC). However, the increasing incidence of TC in younger adults has been suggested to be associated with other factors.

Objectives: The present study investigated the relationship between TC and human papillomavirus (HPV) infection.

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Since no diagnostic method has been established to distinguish follicular thyroid carcinoma (FTC) from follicular thyroid adenoma (FTA), surgery has been the only way to reach a diagnosis of follicular neoplasm. Here we investigated the computed tomography (CT) features of follicular neoplasms, toward the goal of being able to identify specific CT features allowing the preoperative differentiation of FTC from FTA. We retrospectively analyzed the cases of 205 patients who underwent preoperative CT of the neck and were histopathologically diagnosed with FTC (n=31) or FTA (n=174) after surgery between January 2002 and June 2016 at several hospitals in Japan.

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This study reports the commissioning methodology and results of a respiratory gating system [AZ - 733 V/733 VI (Anzai Medical Co., Japan)] using a pressure sensor in carbon-ion scanning radiotherapy. Commissioning includes choosing a location and method for pressure sensor installation, delay time measurement of the system, and the final flow test.

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Purpose: In volumetric-modulated arc therapy (VMAT), field configurations such as couch or arc angles are defined manually or using a template. A field configuration is reselected through trial-and-error in the case of undesirable resultant planning. To efficiently plan for desirable quality, configurations should be assessed before dose calculation.

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Objective:: The purpose of the current study is to create a contrast medium extraction method using raw-data-based electron density (rED) and CT number from dual-energy CT (DECT) for automatic delineation of the contrast region.

Methods:: A CT-ED phantom containing tissue-equivalent inserts and an acrylic phantom with an iodinated contrast medium were scanned by DECT. The contrast medium extraction system was created using Python.

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It is a useful method for the adaptive radiotherapy (ART) to calculate absorbed dose accurately on the image set taken by on-board cone beam computed tomography (CBCT) attached to linac for image-guided radiation therapy (IGRT). For this purpose, a simple and accurate calculation method is necessary. Several papers report that it is possible to calculate easily and accurately by using several methods of researches in the neck and prostate, but the lung density varies greatly depending on patient thorax condition.

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Article Synopsis
  • The study investigates the link between adult-onset laryngeal squamous cell papilloma and human papillomavirus (HPV) infection by analyzing clinical records and specimens from 77 patients treated between 1998 and 2014.
  • Findings reveal that 61.8% of laryngeal papilloma cases tested positive for various HPV types, with younger patients showing higher infection rates; however, no malignant transformations were noted during the study.
  • The research identifies koilocytosis as a distinctive pathological feature related to HPV infection in laryngeal cases and marks the first documentation of multiple HPV types in laryngeal papilloma.
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  • The study focuses on how accurate calibration between computed tomography numbers and electron density (CT-ED) is crucial for calculating radiation doses in tissues of varying density.
  • It was found that as tissue thickness increases and photon beam energy decreases, the required accuracy for CT-ED calibration becomes more stringent, particularly for low energy beams like flattening-filter-free (FFF) photon beams.
  • The researchers established specific tolerance levels for electron density corresponding to different tissue types when using a 6 MVFFF beam, with calculated tolerances showing variation among tissue groups, while some tissues lacked sufficient thickness to determine a reliable tolerance.
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Purpose: In this study, we demonstrate the feasibility of using split-arcs in volumetric modulated arc therapy (VMAT), tailored for expiratory breath-hold in stereotactic body radiation therapy (SBRT) for liver tumors. We compare it with three-dimensional conformal radiation therapy (3D-CRT) and continuous-VMAT, for ten randomly selected hepatocellular carcinoma cases.

Methods: Four coplanar and four non-coplanar beams were used for the 3D-CRT plans.

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