The LNL accelerator complex is equipped with two stable ion beams injectors, employing respectively negative and positive ion sources. In particular, a sputtering-type negative ion source and an Electron Cyclotron Resonance Ion Source (ECRIS) are installed on high voltage platforms, to provide the optimum injection energy in the downstream accelerators. Recently, the two injectors have been object of upgrades and developments, in order to improve the overall safety and reliability of the two systems, as well as the beams available for the users. This contribution describes the work related to the above-mentioned activities, the technical choices employed and the latest results on ion beams production.

The ADIGE (Acceleratore Di Ioni a Grande carica Esotici) injector consists of an electrostatic 1+ beam line, equipped with ion sources able to produce a wide variety of beams, coupled to a magnetic beam line, where charge multiplication is accomplished by implementing an Electron Cyclotron Resonance (ECR) based charge breeder. The injector is totally integrated in the SPES (Selective Production of Exotic Species) beam line, to allow the post-acceleration of radioactive ions and is now in an advanced phase of installation. The electrostatic 1+beam line has been put into operation and is now producing beams from alkali metals. This contribution concerns the first results of the beam commissioning of this part of the injector, with the description of the initial debug phase and the solutions adopted to ensure a reliable and continuous operation. Preliminary results of the 1+ beam line characterization will be shown, with a comparison between simulated and measured emittances.

Small-field dosimetry used in advance treatment technologies poses challenges due to loss of lateral charged particle equilibrium (LCPE), occlusion of the primary photon source, and the limited choice of suitable radiation detectors. These challenges greatly influence dosimetric accuracy. Many high-profile radiation incidents have demonstrated a poor understanding of appropriate methodology for small-field dosimetry. These incidents are a cause for concern because the use of small fields in various specialized radiation treatment techniques continues to grow rapidly. Reference and relative dosimetry in small and composite fields are the subject of the International Atomic Energy Agency (IAEA) dosimetry code of practice that has been published as TRS-483 and an AAPM summary publication (IAEA TRS 483; Dosimetry of small static fields used in external beam radiotherapy: An IAEA/AAPM International Code of Practice for reference and relative dose determination, Technical Report Series No. 483; Palmans et al., Med Phys 45(11):e1123, 2018). The charge of AAPM task group 155 (TG-155) is to summarize current knowledge on small-field dosimetry and to provide recommendations of best practices for relative dose determination in small megavoltage photon beams. An overview of the issue of LCPE and the changes in photon beam perturbations with decreasing field size is provided. Recommendations are included on appropriate detector systems and measurement methodologies. Existing published data on dosimetric parameters in small photon fields (e.g., percentage depth dose, tissue phantom ratio/tissue maximum ratio, off-axis ratios, and field output factors) together with the necessary perturbation corrections for various detectors are reviewed. A discussion on errors and an uncertainty analysis in measurements is provided. The design of beam models in treatment planning systems to simulate small fields necessitates special attention on the influence of the primary beam source and collimating devices in the computation of energy fluence and dose. The general requirements for fluence and dose calculation engines suitable for modeling dose in small fields are reviewed. Implementations in commercial treatment planning systems vary widely, and the aims of this report are to provide insight for the medical physicist and guidance to developers of beams models for radiotherapy treatment planning systems.

The PTW 60023 microSilicon is a new unshielded diode detector for small-field photon dosimetry. It provides improved water equivalence and a slightly larger sensitive region diameter in comparison to previous diode detectors in this range. In this study we evaluated the correction factors relevant to commissioning a CyberKnife System with this detector by Monte Carlo simulation and verified this data by multi-detector measurement comparison. The correction factors required for output factor determination were substantially closer to unity at small field sizes than for previous diode versions (e.g. [Formula: see text]  =  0.981 at 5 mm field size which compares with corrections of 5%-6% with other stereotactic diodes). Because of these differences we recommend that corrections to small field output factor measurements generated specifically for the microSilicon detector rather than generic data taken from other diode types should be used with this new detector. For depth-dose measurements the microSilicon is consistent with a microDiamond detector to  <1% (global), except at depths  <10 mm where the diode gives a significantly lower measurement, by 6%-8% at the surface. For profile measurements, the microSilicon requires negligible corrections except in the low dose region outside the beam, where it underestimates off-axis-ratio (OAR) for small fields and overestimates for large fields. Where this effect is most noticeable at the largest field size and depth (115 mm  ×  100 mm and 300 mm depth) the microSilicon overestimates OAR by 2.3% (global) in the profile tail. This is consistent with other unshielded diodes.

The IAEA is currently coordinating a multi-year project to update the TRS-398 Code of Practice for the dosimetry of external beam radiotherapy based on standards of absorbed dose to water. One major aspect of the project is the determination of new beam quality correction factors, k Q , for megavoltage photon beams consistent with developments in radiotherapy dosimetry and technology since the publication of TRS-398 in 2000. Specifically, all values must be based on, or consistent with, the key data of ICRU Report 90. Data sets obtained from Monte Carlo (MC) calculations by advanced users and measurements at primary standards laboratories have been compiled for 23 cylindrical ionization chamber types, consisting of 725 MC-calculated and 179 experimental data points. These have been used to derive consensus k Q values as a function of the beam quality index TPR20,10 with a combined standard uncertainty of 0.6%. Mean values of MC-derived chamber-specific [Formula: see text] factors for cylindrical and plane-parallel chamber types in 60Co beams have also been obtained with an estimated uncertainty of 0.4%.

Purpose: The aims of this study were: (i) to validate in a multi-site context the suitability of the IBA Razor silicon diode detector for CyberKnife relative dosimetry. (ii) to fit the multi-center experimental data into a function relating the field output factors to the effective field size (EFS). Methods and materials: Ratio of detector readings in clinical and reference field (OFdet) and beam profiles were acquired on five CyberKnife units for fixed collimator diameters (range 5-60 mm), using both Razor and PTW 60017 diodes. Measured OFdet were corrected using published MonteCarlo correction factors to get field output factors Omega(fclin,fmsr)(Qclin,Qmsr). Profiles were analyzed in terms of penumbra and EFS. Omega(fclin,fmsr)(Qclin,Qmsr)obtained in four centers were fitted as a function of EFS, while the data of the 5th center were used to validate the fitting curve. Results: Differences between Razor and PTW60017 Omega(fclin,fmsr)(Qclin,Qmsr) were within 1.5% over all centers down to 7.5 mm aperture and within 3.5% for the 5 mm diameter. The fit showed a coefficient of determination R2 = 0.997. The mean deviation of measured points from the predictive curve was within 0.5%. Data of the 5th center showed a mean deviation of 0.4% from the curve, with maximum differences within 2.5% for the 7.5 mm aperture. Conclusions: The results confirmed the suitability of Razor detector for CyberKnife dosimetry by comparison to the PTW 60017 diode which has been well characterized and is in widespread use. The proposed mathematical relation between Omega(fclin,fmsr)(Qclin,Qmsr) and EFS is a robust predictive model applicable to different CyberKnife systems and detectors.

Small field dosimetry correction factors are usually determined from calculations or measurements using one specific example of a treatment system. The sensitivity of the corrections to inter-unit variation is therefore not evaluated. We propose two methods for this evaluation that could be applied to any system. We use them to assess the variability in [Formula: see text] for the CyberKnife System caused by design changes between pre-M6 and M6 versions, and to the variability in [Formula: see text] and [Formula: see text] resulting from measured beam-data variations across 139 units. We also perform measurements to investigate the differences in [Formula: see text] reported for microchambers in a CyberKnife-specific study versus TRS-483. The results show that [Formula: see text] is smaller for the M6 version than pre-M6 versions by 0.4% for a Farmer chamber, and 0.1% for shorter chambers. The presence or absence of a lead filter within the treatment head had no significant impact on [Formula: see text]. The beam-data analysis showed inter-unit variations in [Formula: see text] of ±0.8% (2 s.d.) for Farmer chambers and ⩽ ±0.5% for shorter cavities (<10 mm) pre-M6, reducing to 0.4% and 0.2% respectively with M6. Inter-unit [Formula: see text] variations for microDiamond and microchambers were ⩽ ±1% at 5 mm field size, except for microchambers with axis perpendicular to the beam where this was > ±2%. Differences of up to 9% were confirmed between Output Factors measured using a microchamber and corrected using TRS-483 [Formula: see text], and a consensus dataset for the same treatment unit determined using multiple detectors and Monte Carlo simulation. A set of practical recommendations for small field dosimetry with the CyberKnife System is derived from these results.

The ADIGE (Acceleratore Di Ioni a Grande carica Esotici) injector of the SPES (Selective Production of Exotic Species) project is now in an advanced phase of installation. Its main components have been designed following particular needs of the project: first, an Electron Cyclotron Resonance (ECR)-based Charge Breeder (SPES-CB), to boost the charge states of the radioactive ions produced at SPES and allow their post-acceleration. Then, a stable 1+ source and a complete electrostatic beam line to characterize the SPES-CB. Finally, a unique Medium Resolution Mass Spectrometer (MRMS, R=1/1000), mounted on a high voltage platform downstream the SPES-CB, to clean the radioactive beam from the contaminants induced by the breeding stage. This contribution describes the status of the injector, in particular the installation of the platform housing the MRMS, the access and safety system adopted and the first beams to be extracted from the stable 1+ source.

During 2018, the PIAVE superconducting linac injector at INFN-LNL, based on superconducting RFQs and two cryomodules with quarter wave resonators, underwent a renovation plan. This operation was strictly related to the one carried out on ALPI [1], which will become a post-accelerator for both stable and exotic beams in a near future. PIAVE Quarter Wave Resonator (QWR) cryomodules, in operation since 2006, were moved to ALPI to be used for the acceleration of both stable beams and future exotic beams delivered from the cyclotron target-ion-source station, after appropriate purification, charge breeding and pre-acceleration stages. In order to cope with the removal of the two QWR cryomodules in PIAVE, a newly designed 80 MHz room temperature buncher was designed, built and tested: the buncher is required so as to match the longitudinal phase space between PIAVE superconducting RFQs (SRFQ1 and SRFQ2) and ALPI. In the same period, substantial refurbishments on the ECR ion source platform were carried out, in particular on its infrastructure and safety equipment. A problem on an electronic component on SRFQ2, though quickly fixed, delayed beam commissioning of the PIAVE injector, which will start at the end of May 2019.

Medical PhysicsVolume 45, Issue 12 p. 5666-5668 Correspondence Comments on the TRS-483 protocol on small field dosimetry Indra J. Das, Corresponding Author Indrajdas@gmail.com Department of Radiation Oncology, NYU Langone Medical Center, and Laura & Isaac Perlmutter Cancer Center, New York, NY, USAAuthor to whom correspondence should be addressed. Electronic mail: Indrajdas@gmail.com; Telephone: +(215) 385-4523; fax: +(212) 731-5513.Search for more papers by this authorPaolo Francescon, Department of Radiation Oncology, Ospedale Di Vicenza, Viale Rodolfi, Vicenza, 36100 ItalySearch for more papers by this author Indra J. Das, Corresponding Author Indrajdas@gmail.com Department of Radiation Oncology, NYU Langone Medical Center, and Laura & Isaac Perlmutter Cancer Center, New York, NY, USAAuthor to whom correspondence should be addressed. Electronic mail: Indrajdas@gmail.com; Telephone: +(215) 385-4523; fax: +(212) 731-5513.Search for more papers by this authorPaolo Francescon, Department of Radiation Oncology, Ospedale Di Vicenza, Viale Rodolfi, Vicenza, 36100 ItalySearch for more papers by this author First published: 11 December 2018 https://doi.org/10.1002/mp.13236Citations: 7Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume45, Issue12December 2018Pages 5666-5668 RelatedInformation

Since fall 2017, the ADIGE (Acceleratore Di Ioni a Grande carica Esotici) injector of the SPES (Selective Production of Exotic Species) project entered the installation phase. The injector includes an Electron Cyclotron Resonance (ECR)-based Charge Breeder (SPES-CB) and its complete beam line, as well as a newly designed RFQ, to allow the post-acceleration of the radioactive ions produced in the so-called target-ion source-system. The injector has different peculiarities, deriving from particular needs of SPES: a complete electrostatic beam line equipped with a 1+ source for test purposes, and a unique Medium Resolution Mass Spectrometer (MRMS, R similar to 1/1000), mounted downstream the SPES-CB, to clean the radioactive beam from the contaminants induced by the breeding stage. This contribution reports about the status of the installation of the injector, describing the various technical solution adopted, and giving a realistic planning for the commission and following operation of its main parts.

Purpose The new limit established for the eye lens has increased the interest for lens dose monitoring. This work aims to: • Estimate the lens doses for the staff of the Interventional Radiology department at Vicenza Hospital; • Establish relationships between the eye lens dose and the dose measured with personal dosimeters; • Verify the feasibility of using commercial Hp(3) dosimeters; • Investigate a possible relationships between the lens dose and the air Kerma–Area product (KAP). Methods Measurements have been carried out both in vivo (4 radiologists and 5 nurses) during 87 different abdominal procedures performed with a Multistar (Siemens, Germany), and in anthropomorphic-phantom using a single 180° projection at 59 kV and 125 kV. The evaluations included: Hp(10) and Hp(0.07) measurements performed at the chest level over the apron (Hp,chest); Hp(0.07) measurements performed on the external and inferior sides of the left eye using Hp(0.07) detectors specifically modified for this purpose (Hp,eye); Hp(3) performed with dedicated dosimeters positioned over the left arm of the protective glasses (Hp,glasses). Additional Hp(0.07) measurement were performed directly at the phantom eye lens level (Hp,lens). Transmission factors of the lead glasses were also estimated. Results The main results are: • Hp,eye/Hp,chest: 0.6 ± 0.6 (in vivo); 0.4 ± 0.2 (in phantom) • Hp,eye/Hp,glasses: 1.1 ± 1.2 (in vivo); 0.5 ± 0.5 (in phantom) • Hp,chest/KAP: 2.5 ± 3.6 μSv Gy−1 cm−2 (in vivo); 5.8 ± 2.0 μSv Gy−1 cm−2 (in phantom) In vivo and phantom results are consistent within the large uncertainties due to low dose levels and irradiations variability. Therefore phantom measurements allowed estimating Hp,lens/Hp,eye in 0.20 when glasses are used. Using this factor, the projected annual eye lens dose, considering the workload, resulted 4 mSv for the personnel using lead glasses and 15 mSv for the others. The ratio between eye lens dose with and without glasses is higher than expected based on transmission factors. Conclusions According to our results, traditional monitoring methods with proper corrections could be used to estimate lens dose in place of expensive Hp(3) dosimeters. Missing glasses-skin contact could explain eye doses higher than expected.