Association Between Thyroid Radiation Dose and Hypothyroidism in Breast Cancer Patients Undergoing Volumetric Modulated Arc Therapy for Regional Nodal Irradiation.

Background/aim: To investigate the association between the thyroid dysfunction and thyroid radiation dose in regional nodal irradiation (RNI) using volumetric modulated arc therapy (VMAT) for breast cancer.

Patients And Methods: We reviewed medical data of 67 patients with breast cancer who underwent curative surgery followed by adjuvant radiotherapy, including RNI using VMAT, between 2018 and 2021. All patients had normal thyroid functional test results, including thyroid stimulating hormone (TSH), T3, and free-T4.

Mask dependency of the lacrimal gland dose under whole brain radiotherapy when the six-degrees of freedom couch is not available.

Background: Dry eye syndrome has been recently reported in patients who underwent whole brain radiotherapy (WBRT). WBRT based on a couch with three-degrees of freedom (3D) can occasionally be performed in which the rotational head motion is not corrected. This study assessed the dependency of the rotational errors on the mask and the dose variation of the lens and lacrimal gland in WBRT patients.

Effects of Radiation Dose on Liver After Free-breathing Volumetric Modulated Arc Therapy for Breast Cancer.

Background/aim: To evaluate the early effect of radiation dose on liver function in breast cancer patients undergoing free-breathing volumetric modulated arc therapy (FB-VMAT).

Patients And Methods: Medical records of 125 patients with breast cancer who underwent curative surgery followed by postoperative radiotherapy using FB-VMAT during 2018-2021 were reviewed. Results of the liver function test (LFT), performed within 1-week before and 6-months after radiotherapy, were collected and compared.

Combined effect of dose gradient and rotational error on prescribed dose coverage for single isocenter multiple brain metastases in frameless stereotactic radiotherapy.

Background: To evaluate the combined effect of rotational error and dose gradient on target dose coverage in frameless stereotactic radiotherapy.

Methods: Three spherical targets of different diameters (1, 1.5, and 2 cm) were drawn and placed equidistantly on the same axial brain computed tomography (CT) images.

Enhancement of megavoltage electronic portal images for markerless tumor tracking.

Purpose: The poor quality of megavoltage (MV) images from electronic portal imaging device (EPID) hinders visual verification of tumor targeting accuracy particularly during markerless tumor tracking. The aim of this study was to investigate the effect of a few representative image processing treatments on visual verification and detection capability of tumors under auto tracking.

Methods: Images of QC-3 quality phantom, a single patient's setup image, and cine images of two-lung cancer patients were acquired.

Electron dose distributions caused by the contact-type metallic eye shield: Studies using Monte Carlo and pencil beam algorithms.

A metallic contact eye shield has sometimes been used for eyelid treatment, but dose distribution has never been reported for a patient case. This study aimed to show the shield-incorporated CT-based dose distribution using the Pinnacle system and Monte Carlo (MC) calculation for 3 patient cases. For the artifact-free CT scan, an acrylic shield machined as the same size as that of the tungsten shield was used.

Analysis of predictive factors for lung injury after forward-planned intensity-modulated radiotherapy in whole breast irradiation.

Purpose: This study was performed to assess frequency, timings of occurrence, and predictors of radiologic lung damage (RLD) after forward-planned intensity-modulated radiotherapy (FIMRT) for whole breast irradiation.

Methods: We retrospectively reviewed medical records of 157 breast cancer patients and each of their serial chest computed tomography (CT) taken 4, 10, 16, and 22 months after completion of breast radiotherapy (RT). FIMRT was administered to whole breast only (n=152), or whole breast and supraclavicular regions (n=5).

Application of a dummy eye shield for electron treatment planning.

Metallic eye shields have been widely used for near-eye treatments to protect critical regions, but have never been incorporated into treatment plans because of the unwanted appearance of the metal artifacts on CT images. The purpose of this work was to test the use of an acrylic dummy eye shield as a substitute for a metallic eye shield during CT scans. An acrylic dummy shield of the same size as the tungsten eye shield was machined and CT scanned.

Variations in dose distribution and optical properties of Gafchromic(TM) EBT2 film according to scanning mode.

Purpose: The authors aim was to investigate the effects of using transmission and reflection scanning modes, the film orientation during scanning, and ambient room light on a dosimetry system based on the Gafchromic(TM) EBT2 film model.

Methods: For calibration, the films were cut to 3 × 3 cm(2) and irradiated from 20 to 700 cGy at the depth of maximum dose using 6 and 10 MV photon beams in a 10 × 10 cm(2) field size. Absolute dose calibration of the linear accelerator was done according to the TRS398 protocol.

Evaluation of delivered monitor unit accuracy of gated step-and-shoot IMRT using a two-dimensional detector array.

Purpose: To overcome the problem of organ motion in intensity-modulated radiation therapy (IMRT), gated IMRT is often used for the treatment of lung cancer. In this study, the authors investigated the accuracy of the delivered monitor units (MUs) from each segment during gated IMRT using a two-dimensional detector array for user-specific verification purpose.

Methods: The authors planned a 6 MV photon, seven-port step-and-shoot lung IMRT delivery.

Dosimetric characteristics of linear accelerator photon beams with small monitor unit settings.

Several studies on the effect of tumor cell killing by dose rate variation have implied that the use of a shorter treatment time is more favorable for intensity modulated radiation therapy (IMRT). Aiming at step-and-shoot IMRT with higher dose rates, the stabilities of beam output and profiles with small monitor unit (MU) settings were investigated for various dose rates. With the use of a Varian 21EX (Varian Medical Systems Inc.

Monte Carlo-based treatment planning for a spoiler system with experimental validation using plane-parallel ionization chambers.

A beam spoiler is often used to increase the build-up dose near the surface for treatment of superficial treatment areas. Photon-beam spoilers produce a large amount of contaminant electrons, conditions for which standard, commercial treatment-planning system dose-calculation algorithms are inadequate for producing accurate dose calculations. In this study, we implemented a Monte Carlo (MC) dose-calculation algorithm for this spoiler system.

Clinical and experimental investigation of pseudoaneurysm in the anterior communicating artery area on 3-dimensional time-of-flight cerebral magnetic resonance angiography.

Objective: To investigate the hemodynamic mechanism of pseudoaneurysm in the anterior communicating artery (AcoA) area in magnetic resonance (MR) angiography.

Methods: For the clinical study, a total of 62 patients who undertook digital subtraction angiography (DSA) because of the rupture of an aneurysm originating from a location other than the AcoA area were examined with MR angiography. The relation between signal defect at the AcoA in MR angiography and anatomic variation of the anterior cerebral artery (ACA) was evaluated.