Validation of PTV margin for Gamma Knife Icon frameless treatment using a PseudoPatient® Prime anthropomorphic phantom.

The Gamma Knife Icon allows the treatment of brain tumors mask-based single-fraction or fractionated treatment schemes. In clinic, uniform axial expansion of 1 mm around the gross tumor volume (GTV) and a 1.5 mm expansion in the superior and inferior directions are used to generate the planning target volume (PTV).

Dosimetric performance of the Elekta Unity MR-linac system: 2D and 3D dosimetry in anthropomorphic inhomogeneous geometry.

Following the clinical introduction of the Elekta Unity MR-linac, there is an urgent need for development of dosimetry protocols and tools, not affected by the presence of a magnetic field. This work presents a benchmarking methodology comprising 2D/3D passive dosimetry and involving on-couch adaptive treatment planning, a unique step in MR-linac workflows. Two identical commercially available 3D-printed head phantoms (featuring realistic bone anatomy and MR/CT contrast) were employed.

Characterization of a novel 3D printed patient specific phantom for quality assurance in cranial stereotactic radiosurgery applications.

In single-isocenter stereotactic radiosurgery/radiotherapy (SRS/SRT) intracranial applications, multiple targets are being treated concurrently, often involving non-coplanar arcs, small photon beams and steep dose gradients. In search for more rigorous quality assurance protocols, this work presents and evaluates a novel methodology for patient-specific pre-treatment plan verification, utilizing 3D printing technology. In a patient's planning CT scan, the external contour and bone structures were segmented and 3D-printed using high-density bone-mimicking material.

A Holistic Approach to Assessment of Population Exposure to Radiation: Challenges and Initiatives of a Regulatory Authority.

A regulatory authority for radiation safety should continuously evaluate and improve the national safety framework, in line with current requirements and standards. In this context, the Greek Atomic Energy Commission initiated a series of concerted actions. The radiation dose to the population due to public and medical exposures was assessed.

On the total system error of a robotic radiosurgery system: phantom measurements, clinical evaluation and long-term analysis.

The total system error (TSE) of a CyberKnife system was measured using two phantom-based methods and one patient-based method. The standard radiochromic film (RCF) end-to-end (E2E) test using an anthropomorphic head and neck phantom and isocentric treatment delivery was used with the 6Dskull, Fiducial and Xsight spine (XST) tracking methods. More than 200 RCF-based E2E results covering the period from installation in 2006 until 2017 were analyzed with respect to tracking method, system hardware and software versions, secondary collimation system, and years since installation.

A comparative assessment of inhomogeneity and finite patient dimension effects in Co and Ir high-dose-rate brachytherapy.

Purpose: To perform a comparative study of heterogeneities and finite patient dimension effects in Co and Ir high-dose-rate (HDR) brachytherapy.

Material And Methods: Clinically equivalent plans were prepared for 19 cases (8 breast, 5 esophagus, 6 gynecologic) using the Ir2.A85-2 and the Co0.

A generic TG-186 shielded applicator for commissioning model-based dose calculation algorithms for high-dose-rate Ir brachytherapy.

Purpose: A joint working group was created by the American Association of Physicists in Medicine (AAPM), the European Society for Radiotherapy and Oncology (ESTRO), and the Australasian Brachytherapy Group (ABG) with the charge, among others, to develop a set of well-defined test case plans and perform calculations and comparisons with model-based dose calculation algorithms (MBDCAs). Its main goal is to facilitate a smooth transition from the AAPM Task Group No. 43 (TG-43) dose calculation formalism, widely being used in clinical practice for brachytherapy, to the one proposed by Task Group No.

On the experimental validation of model-based dose calculation algorithms for Ir HDR brachytherapy treatment planning.

There is an acknowledged need for the design and implementation of physical phantoms appropriate for the experimental validation of model-based dose calculation algorithms (MBDCA) introduced recently in Ir brachytherapy treatment planning systems (TPS), and this work investigates whether it can be met. A PMMA phantom was prepared to accommodate material inhomogeneities (air and Teflon), four plastic brachytherapy catheters, as well as 84 LiF TLD dosimeters (MTS-100M 1  ×  1  ×  1 mm microcubes), two radiochromic films (Gafchromic EBT3) and a plastic 3D dosimeter (PRESAGE). An irradiation plan consisting of 53 source dwell positions was prepared on phantom CT images using a commercially available TPS and taking into account the calibration dose range of each detector.

On source models for (192)Ir HDR brachytherapy dosimetry using model based algorithms.

A source model is a prerequisite of all model based dose calculation algorithms. Besides direct simulation, the use of pre-calculated phase space files (phsp source models) and parameterized phsp source models has been proposed for Monte Carlo (MC) to promote efficiency and ease of implementation in obtaining photon energy, position and direction. In this work, a phsp file for a generic (192)Ir source design (Ballester et al 2015) is obtained from MC simulation.

A generic high-dose rate (192)Ir brachytherapy source for evaluation of model-based dose calculations beyond the TG-43 formalism.

Purpose: In order to facilitate a smooth transition for brachytherapy dose calculations from the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) formalism to model-based dose calculation algorithms (MBDCAs), treatment planning systems (TPSs) using a MBDCA require a set of well-defined test case plans characterized by Monte Carlo (MC) methods. This also permits direct dose comparison to TG-43 reference data.

A retrospective dosimetric comparison of TG43 and a commercially available MBDCA for an APBI brachytherapy patient cohort.

Purpose: To compare dosimetry using a contemporary model based dose calculation algorithm (MBDCA) following TG186 recommendations, and the conventional TG43 method in an (192)Ir high dose rate (HDR) accelerated partial breast irradiation (APBI) patient cohort.

Methods: Data of 38 APBI patients were studied. Dosimetry for the treatment plans was performed using both the TG43 and TG186 dose calculation methods of the Oncentra Brachy v4.

Brachytherapy structural shielding calculations using Monte Carlo generated, monoenergetic data.

Purpose: To provide a method for calculating the transmission of any broad photon beam with a known energy spectrum in the range of 20-1090 keV, through concrete and lead, based on the superposition of corresponding monoenergetic data obtained from Monte Carlo simulation.

Methods: MCNP5 was used to calculate broad photon beam transmission data through varying thickness of lead and concrete, for monoenergetic point sources of energy in the range pertinent to brachytherapy (20-1090 keV, in 10 keV intervals). The three parameter empirical model introduced by Archer et al.

Dosimetric accuracy of a deterministic radiation transport based (192)Ir brachytherapy treatment planning system. Part III. Comparison to Monte Carlo simulation in voxelized anatomical computational models.

Purpose: To compare TG43-based and Acuros deterministic radiation transport-based calculations of the BrachyVision treatment planning system (TPS) with corresponding Monte Carlo (MC) simulation results in heterogeneous patient geometries, in order to validate Acuros and quantify the accuracy improvement it marks relative to TG43.

Methods: Dosimetric comparisons in the form of isodose lines, percentage dose difference maps, and dose volume histogram results were performed for two voxelized mathematical models resembling an esophageal and a breast brachytherapy patient, as well as an actual breast brachytherapy patient model. The mathematical models were converted to digital imaging and communications in medicine (DICOM) image series for input to the TPS.

On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the k(Q(clin),Q(msr) ) (f(clin),f(msr) ) correction factors for microchamber and diode detectors.

Purpose: To measure the output factors (OFs) of the small fields formed by the variable aperture collimator system (iris) of a CyberKnife (CK) robotic radiosurgery system, and determine the k(Q(clin),Q(msr) ) (f(clin),f(msr) ) correction factors for a microchamber and four diode detectors.

Methods: OF measurements were performed using a PTW PinPoint 31014 microchamber, four diode detectors (PTW-60017, -60012, -60008, and the SunNuclear EDGE detector), TLD-100 microcubes, alanine dosimeters, EBT films, and polymer gels for the 5 mm, 7.5 mm, 10 mm, 12.

Dosimetric accuracy of a deterministic radiation transport based 192Ir brachytherapy treatment planning system. Part II: Monte Carlo and experimental verification of a multiple source dwell position plan employing a shielded applicator.

Purpose: The aim of this work is the dosimetric validation of a deterministic radiation transport based treatment planning system (BRACHYVISION v. 8.8, referred to as TPS in the following) for multiple 192Ir source dwell position brachytherapy applications employing a shielded applicator in homogeneous water geometries.

Accuracy of multislice CT angiography for the assessment of in-stent restenoses in the iliac arteries at reduced dose: a phantom study.

Objective: We investigated the potential of low-dose CT angiography for accurate assessment of in-stent restenoses (ISRs) of the iliac artery.

Method: A Rando anthropomorphic phantom (Alderson Research Labs, Stanford, CA), custom-made wax simulating hyperplastic tissue and a nitinol stent were used to simulate a patient with clinically relevant iliac artery ISRs. The cylindrical lumen was filled with a solution of iodine contrast medium diluted in saline, representing a patient's blood during CT angiography.

On the implementation of a recently proposed dosimetric formalism to a robotic radiosurgery system.

Purpose: The aim of this work is to implement a recently proposed dosimetric formalism for nonstandard fields to the calibration and small field output factor measurement of a robotic stereotactic radiosurgery system.

Methods: Reference dosimetry measurements were performed in the nonstandard, 60 mm diameter machine specific reference (msr) field using a Farmer ion chamber, five other cylindrical chambers with cavity lengths ranging from 16.25 down to 2.

Dosimetric accuracy of a deterministic radiation transport based 192Ir brachytherapy treatment planning system. Part I: single sources and bounded homogeneous geometries.

Purpose: The aim of this work is to validate a deterministic radiation transport based treatment planning system (TPS) for single 192Ir brachytherapy source dosimetry in homogeneous water geometries.

Methods: TPS results were obtained using the deterministic radiation transport option of a BRACHYVISION v. 8.

Conceptus dose from involved-field radiotherapy for Hodgkin's lymphoma on a linear accelerator equipped with MLCs.

Purpose: To estimate the scattered dose to conceptus from involved-field radiotherapy for Hodgkin's lymphoma on a linear accelerator equipped with multileaf collimators.

Material And Methods: Anthropomorphic phantoms were used to simulate an average pregnant woman at the 1st, 2nd and 3rd trimesters of gestation. Conceptus dose was measured using thermoluminescent dosimeters.