[Decomposing a Beam Profile Constancy into Energy and Symmetry Components and Its Evaluation Using an Ionization Chamber Array].

Purpose: We have proposed a new formulation that can decompose the profile constancy defined in the AAPM TG 142 into energy and symmetry constancies by measuring beam profiles using an IC profiler (ICP).

Methods: Measured profiles were laterally inverted to calculate averaged profiles in the lateral direction, thereby cancelling asymmetric components. Validation tests were performed by comparing the proposed calculation and measured results under various experimental conditions.

Practical guidelines of online MR-guided adaptive radiotherapy.

The first magnetic resonance (MR)-guided radiotherapy system in Japan was installed in May 2017. Implementation of online MR-guided adaptive radiotherapy (MRgART) began in February 2018. Online MRgART offers greater treatment accuracy owing to the high soft-tissue contrast in MR-images (MRI), compared to that in X-ray imaging.

Questionnaire survey on treatment planning techniques for lung stereotactic body radiotherapy in Japan.

This study aimed to obtain details regarding treatment planning techniques for lung stereotactic body radiation therapy (SBRT) employed at each institution in Japan by using a questionnaire survey. An Internet questionnaire survey on SBRT procedures performed in 2016 was conducted by the QA/QC committee of the Japan Society of Medical Physics from April to June 2017. The questionnaire assessed two aspects: the environment for SBRT at each institution and the treatment planning techniques with and without respiratory motion management techniques (RMMT).

[Radiofrequency Ablation under Computed Tomography during Arterial Portography for Hypovascular Liver Metastases from Advanced Pancreatic Cancer].

A 70's man had been treated with gemcitabine(GEM)and nab-paclitaxel(nabPTX)combination for advanced pancreatic tail cancer with splenic invasion and liver metastases. However, the primary lesion was not controlled, then intensity-modulat- ed radiation therapy(76.5 Gy/17 Fr)was performed for primary lesion.

Definitive re-irradiation using intensity-modulated radiation therapy in cancers of the head and neck, focusing on rare tumors.

Purpose: To analyze the outcomes following re-irradiation for local recurrence of rare head and neck tumors.

Material And Methods: We retrospectively analyzed 11 patients who had received intensity-modulated radiation therapy (IMRT) for recurrent tumors in the head and neck except for laryngopharynx.

Results: Primary tumor sites included the maxillary sinus, nasal cavity, and external ear canal in six, three, and two patients, respectively.

Clinical Assessment of Micro-residual Tumors during Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma.

Background: This study aimed to assess the need to consider microscopic invasion in terms of treatment planning in stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma and elucidate the appropriate clinical target volume (CTV) margin.

Patients And Methods: A total of 121 patients (with 146 liver tumors) who underwent SBRT between July 2007 and August 2016 were analyzed, regarding overall survival and local control (LC).

Results: The 2- and 5-year LC rates were 91.

Effect of primary tumor location and tumor size on the response to radiotherapy for liver metastases from colorectal cancer.

Metastatic liver tumors (MLTs) from colorectal cancer (CRC) are often treated with stereotactic body radiation therapy (SBRT). The present study aimed to examine the predictive factors for response of MLTs to SBRT. A total of 39 MLTs from 24 patients with CRC were retrospectively analyzed.

Threshold doses and prediction of visually apparent liver dysfunction after stereotactic body radiation therapy in cirrhotic and normal livers using magnetic resonance imaging.

The purpose of the present study was to investigate the threshold dose for focal liver damage after stereotactic body radiation therapy (SBRT) in cirrhotic and normal livers using magnetic resonance imaging (MRI). A total of 64 patients who underwent SBRT for liver tumors, including 54 cirrhotic patients with hepatocellular carcinoma (HCC) and 10 non-cirrhotic patients with liver metastases, were analyzed. MRI was performed 3-6 months after SBRT, using gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced T1-weighted sequences.

A dose-volume intercomparison of volumetric-modulated arc therapy, 3D static conformal, and rotational conformal techniques for portal vein tumor thrombus in hepatocellular carcinoma.

We created volumetric-modulated arc therapy (VMAT) plans for portal vein tumor thrombus (PVTT) in hepatocellular carcinoma, and compared the results with those from three-dimensional conformal radiotherapy (3D-CRT) and rotational conformal radiotherapy (R-CRT) plans. CT scan data from 10 consecutive patients with PVTT treated with 3D-CRT between January 2008 and January 2010 were utilized in the analysis. We analyzed the dosimetric properties of the plans for the 10 patients using the three different techniques with three different isocenter doses of 50, 56 and 60 Gy in 2-Gy fractions.

Delivery parameter variations and early clinical outcomes of volumetric modulated arc therapy for 31 prostate cancer patients: an intercomparison of three treatment planning systems.

We created volumetric modulated arc therapy (VMAT) plans for 31 prostate cancer patients using one of three treatment planning systems (TPSs)--ERGO++, Monaco, or Pinnacle--and then treated those patients. A dose of 74 Gy was prescribed to the planning target volume (PTV). The rectum, bladder, and femur were chosen as organs at risk (OARs) with specified dose-volume constraints.

[Electronic portal image device dosimetry for volumetric modulated arc therapy].

Recently electronic portal image devices (EPIDs) have been widely used for quality assurance and dose verification. However there are no reports describing EPID dosimetry for Elekta volumetric modulated arc therapy (VMAT). We have investigated EPID dosimetry during VMAT delivery using a commercial software EPIDose with an Elekta Synergy linac.

[Positional accuracy and quality assurance of Backup JAWs required for volumetric modulated arc therapy].

The tolerance of the Backup diaphragm (Backup JAW) setting in Elekta linac was specified as 2 mm according to the AAPM TG-142 report. However, the tolerance and the quality assurance procedure for volumetric modulated arc therapy (VMAT) was not provided. This paper describes positional accuracy and quality assurance procedure of the Backup JAWs required for VMAT.

[Quality assurance procedure for assessing mechanical accuracy of a radiation field center in stereotactic radiotherapy].

Stereotactic radiotherapy requires a quality assurance (QA) program that ensures the mechanical accuracy of a radiation field center. We have proposed a QA method for achieving the above requirement by conducting the Winston Lutz test using an electronic portal image device (EPID). An action limit was defined as three times the standard deviation.

Minimum requirements for commissioning and long-term quality assurance of Elekta multi-leaf collimator for volumetric modulated arc therapy.

We have proposed minimum requirements for commissioning and long-term quality assurance (QA) of an Elekta multi-leaf collimator (MLC) for volumetric modulated arc therapy (VMAT). The MLC leaf position accuracy during VMAT delivery was evaluated with the use of three different QA test plans: (1) a leaf gap-width test between opposing leaves by measurement of the isocenter dose during constant-gap sliding-window delivery with varied dose rates, MLC leaf speeds, and gantry angles; (2) a leaf position test by picket-fence delivery with and without gantry rotation; and (3) a leaf-bank symmetry test by measurement of the field geometry with different collimator angles at a fixed gantry position. All the QA test plans were created using an ERGO++ treatment-planning system.

[Optimization of multi-leaf collimator leaf offset table for a treatment planning system].

For accurate dose delivery using a rounded leaf-end multi-leaf collimator (MLC), a consistent understanding of MLC leaf offset is required between a linear accelerator (linac) controller and a treatment planning system (TPS). We have found that the leaf offset tables were inconsistent between an Elekta linac controller and a Pinnacle TPS. An optimum leaf offset table for Pinnacle was determined by operating the TPS and the linac controller.

[A method for removing moiré artifacts from scanned images of radiochromic films: application to transmissive scanning].

Dose verification using radiochromic films may bring about moiré artifacts during the film scanning process using a flatbed scanner. A method for removing the moiré artifacts was already reported for reflective scanning. Recently, transmissive scanning using EBT2 films has played a major role for dose verification in intensity-modulated radiation therapy.

[Mechanical accuracy of a stereotactic irradiation system using a micro multi-leaf collimator].

Mechanical accuracy of a stereotactic irradiation system using a micro multi-leaf collimator (mMLC), Elekta DMLC, has been evaluated. Measurements were made to obtain transmission, leakage, penumbra, and positioning accuracy of the DMLC leaf for a 6 MV photon beam. Mechanical accuracy and long term stability of a linac isocenter was also evaluated.