Particle Accelerators

The capability of performing functional radiosurgery lesions in the brain using a dedicated linear accelerator (LINAC) have not yet been demonstrated. This study evaluates modern LINAC technology for the creation of a sharp, small and functionally eloquent lesion in the thalamus. Three patients underwent thalamotomy using a dedicated linear accelerator to radiosurgery, 2 females and 1 male, ages were 52, 53, and 73 years. Two patients presented with unilateral poststroke central pain and 1 with unilateral upper extremity pain secondary to metastatic infiltration of the brachial plexus. Maximal doses varied from 150 to 200 Gy, delivered by a 5-mm diameter collimator and 5 to 8 noncoplanar arcs evenly distributed. All patients gained substantial relief of their pain. They were able to reduce their medications and improve their activity levels. The patient with end-stage metastatic disease died of his malignancy 2 weeks after the treatment. One patient presented with recurrence of the pain 4 months after the treatment. No clinical complications were noticed. A dedicated linear accelerator is able to perform a precise and circumscribed lesion in the thalamus for pain control. Moreover, it proved to be safe, because no complications were observed. For patients using chronic anticoagulant therapy or with severe disabilities caused by cardiac, pulmonary or malignant diseases, this technique represents an alternative of treatment to radiofrequency thalamotomy.

Particle radiotherapy such as proton and carbon ion has been producing promising clinical results worldwide. The purpose of this study was to compare metastatic capabilities of malignant tumor cells after irradiation with photon, proton, and carbon ion beams to clarify their ion beam-specific biological effects. We examined the biological properties of highly aggressive HT1080 human fibrosarcoma cells to assess their

To improve the quality of liver stereotactic body radiation therapy (SBRT) treatments, a novel 4π framework was developed with accompanying algorithms to optimize non-coplanar beam orientations and fluences. The dose optimization is performed on a patient-specific deliverable beam geometry solution space, parameterized with patient and linear accelerator gantry orientations. Beams causing collision between the gantry and the couch or patient were eliminated by simulating all beam orientations using a precise computer assisted design model of the linear accelerator and a human subject. Integrated beam orientation and fluence map optimizations were performed on remaining beams using a greedy column generation method. Testing of the new method was performed on 10 liver SBRT cases previously treated with 50 to 60 Gy in 5 fractions using volumetric modulated arc therapy (VMAT). For each patient, both 14 and 22 non-coplanar fields were selected and optimized to meet the objective of ≥95% of the planning target volume (PTV) covered by 100% of the prescription dose. Doses to organs at risk, normal liver volumes receiving <15 Gy, integral dose, and 50% dose spillage volumes were compared against the delivered clinical VMAT plans. Compared with the VMAT plans, the 4π plans yielded reduced 50% dose spillage volume and integral dose by 22% (range 10%-40%) and 19% (range 13%-26%), respectively. The mean normal liver volume receiving <15 Gy was increased by 51 cc (range 21-107 cc) with a 31% reduction of the mean normal liver dose. Mean doses to the left kidney and right kidney and maximum doses to the stomach and spinal cord were on average reduced by 70%, 51%, 67%, and 64% (P≤.05). This novel 4π non-coplanar radiation delivery technique significantly improved dose gradient, reduced high dose spillage, and improved organ at risk sparing compared with state of the art VMAT plans.

Pulsed Modulators required for RF sources, based on
klystrons and magnetrons, for RF electron linacs have
been designed and developed at Electron Beam Centre,
BARC, Mumbai, India. Electron guns in these linacs have
also been powered by pulsed modulators. Line-type
modulators, as well as IGBT-based solid-state modulators
have been developed for these applications. A 150 kV/100
A line-type modulator has been tested on klystron to
generate 7 MW peak RF Power. Magnetron modulator
has undergone testing up to ~40 kV, 165 A on resistive
load. Solid-state modulator, using fractional-turn pulse
transformer has been designed, developed and tested
successfully on magnetron load up to output power of 1.3
MW peak. A transformerless solid-state modulator for
electron gun of 6 MeV cargo-scanning linac, uses the
Marx adder configuration and has been successfully
tested up to 40 kV. In addition, line-type modulators for
electron guns up to 85 kV have been successfully
commissioned and are in operation in the linac systems.
This paper describes the salient design features of these
modulators, development of pulse transformers, details of
test set-up and discusses the test results of these
modulators.

The purpose of this study is to report the dosimetric aspects of commissioning performed on an Elekta Versa HD linear accelerator (linac) with high-dose-rate flattening filter-free (FFF) photon modes and electron modes. Acceptance and com-missioning was performed on the Elekta Versa HD linac with five photon energies (6 MV, 10 MV, 18 MV, 6 MV FFF, 10 MV FFF), four electron energies (6 MeV, 9MeV, 12 MeV, 15 MeV) and 160-leaf (5 mm wide) multileaf collimators (MLCs). Mechanical and dosimetric data were measured and evaluated. The measurements include percent depth doses (PDDs), in-plane and cross-plane profiles, head scat-ter factor (Sc), relative photon output factors (Scp), universal wedge transmission factor, MLC transmission factors, and electron cone factors. Gantry, collimator, and couch isocentricity measurements were within 1 mm, 0.7 mm, and 0.7 mm diameter, respectively. The PDDs of 6 MV FFF and 10 MV FFF beams show deeper dmax and steeper falloff with depth than the correspo...

An experimental project like CBM necessarily comprises a vast number of activities in many different areas:
research on detector technology, development of readout electronics and components for data acquisition,
computing and software tools for data processing and physics analysis, and many more. The series of annual
CBM Progress Reports, started back in 2006, was intended to collect and document these manifold activities.
Browsing through the past volumes unfolds a large spectrum of scientific work in the process of the realization
of the project: fromconceptual studies over thoroughR&Dto the implementation and testing of prototypes.
This CBM Progress Report 2018 continues along these lines. Its contents, however, reflect that some six years
before the planned start of data taking, the CBM project is undergoing a gradual transition. The long period of
planning and R&D is giving way to the large-scale production and integration of detector hardware, a process
to be finished by 2024, when the CBM apparatus is expected to be commissioned in its experimental area. An
important step towards this realisation of the experiment is the full-system test setup mCBM, allowing to study
the joint in-beam operation of several detector systems and the read-out and data processing, following the
ambitious CBM concept of free-running data acquisition. Further important technological experience is gained
by the deployment of CBM detector systems at running experiments: TOF in STAR, RICH in HADES, PSD in
BM@N. These detector operations will contribute important technological expertise for the preparation of the
full CBM experiment.
We hope this reports conveys some of the enthusiasm of the CBM collaboration in the realization of a technologically
very challenging experimental project which promises a rich physics output once taking data. Our
thanks go to all who have contributed to this report: the reviewers, who helped getting it into shape, and all
authors having delivered the actual content.
Darmstadt, October 2019
Volker Friese and Ilya Selyuzhenkov, editors

The purpose of this study was to investigate the feasibility of using a single QA device for comprehensive, efficient daily QA of a linear accelerator (Linac) and three image-guided stereotactic positioning systems (IGSPSs). The Sun Nuclear Daily QA 3 (DQA3) device was used to perform daily dosimetry and mechanical accuracy tests for an Elekta Linac, as well as daily image geometric and isocenter coincidence accuracy tests for three IGSPSs: the AlignRT surface imaging system; the frameless SonArray optical tracking System (FSA) and the Elekta kV CBCT. The DQA3 can also be used for couch positioning, repositioning, and rotational tests during the monthly QA. Based on phantom imaging, the Linac coordinate system determined using AlignRT was within 0.7 mm/0.6° of that of the CBCT system. The difference is attributable to the different calibration methods that are utilized for these two systems. The laser alignment was within 0.5 mm of the isocenter location determined with the three IG...

A Monte Carlo (MC) based QA process to validate the dynamic beam delivery accuracy for Varian RapidArc (Varian Medical Systems, Palo Alto, CA) using Linac delivery log files (DynaLog) is presented. Using DynaLog file analysis and MC simulations, the goal of this article is to (a) confirm that adequate sampling is used in the RapidArc optimization algorithm (177 static gantry angles) and (b) to assess the physical machine performance [gantry angle and monitor unit (MU) delivery accuracy]. Ten clinically acceptable RapidArc treatment plans were generated for various tumor sites and delivered to a water-equivalent cylindrical phantom on the treatment unit. Three Monte Carlo simulations were performed to calculate dose to the CT phantom image set: (a) One using a series of static gantry angles defined by 177 control points with treatment planning system (TPS) MLC control files (planning files), (b) one using continuous gantry rotation with TPS generated MLC control files, and (c) one using continuous gantry rotation with actual Linac delivery log files. Monte Carlo simulated dose distributions are compared to both ionization chamber point measurements and with RapidArc TPS calculated doses. The 3D dose distributions were compared using a 3D gamma-factor analysis, employing a 3%/3 mm distance-to-agreement criterion. The dose difference between MC simulations, TPS, and ionization chamber point measurements was less than 2.1%. For all plans, the MC calculated 3D dose distributions agreed well with the TPS calculated doses (gamma-factor values were less than 1 for more than 95% of the points considered). Machine performance QA was supplemented with an extensive DynaLog file analysis. A DynaLog file analysis showed that leaf position errors were less than 1 mm for 94% of the time and there were no leaf errors greater than 2.5 mm. The mean standard deviation in MU and gantry angle were 0.052 MU and 0.355 degrees, respectively, for the ten cases analyzed. The accuracy and flexibility of the Monte Carlo based RapidArc QA system were demonstrated. Good machine performance and accurate dose distribution delivery of RapidArc plans were observed. The sampling used in the TPS optimization algorithm was found to be adequate.

Estimation of the surface dose is very important for patients undergoing radiation therapy. The purpose of this study is to investigate the dose at the surface of a water phantom at a depth of 0.007 cm as recommended by the International Commission on Radiological Protection and International Commission on Radiation Units and Measurement with radiochromic films (RFs), thermoluminescent dosemeters and an ionisation chamber in a 6-MV photon beam. The results were compared with the theoretical calculation using Monte Carlo (MC) simulation software (MCNP5, BEAMnrc and DOSXYZnrc). The RF was calibrated by placing the films at a depth of maximum dose (dmax) in a solid water phantom and exposing it to doses from 0 to 500 cGy. The films were scanned using a transmission high-resolution HP scanner. The optical density of the film was obtained from the red component of the RGB images using ImageJ software. The per cent surface dose (PSD) and percentage depth dose (PDD) curve were obtained by ...