A new detector for the beam energy measurement in proton therapy: a feasibility study.

The proof of concept of a new device, capable of determining in a few seconds the energy of clinical proton beams by measuring the time of flight (ToF) of protons, is presented. The prototype consists of two thin ultra fast silicon detector (UFSD) pads, aligned along the beam direction in a telescope configuration and readout by a digitizer. The method developed for extracting the energy at the isocenter from the measured ToF, validated by Monte Carlo simulations, and the procedure used to calibrate the system are also presented and discussed in detail. The prototype was tested at the Centro Nazionale di Adroterapia Oncologica (CNAO, Pavia, Italy), at several beam energies, covering the entire clinical range, and using different distances between the sensors. The measured beam energies were benchmarked against the nominal CNAO energy values, obtained during the commissioning of the centre from the measured ranges in water. Deviations of few hundreds of keV have been achieved for all considered proton beam energies for distances between the two sensors larger than 60 cm, indicating a sensitivity to the corresponding beam range in water smaller than the clinical tolerance of 1 mm. Moreover, few seconds of irradiation were necessary to collect the required statistics. These preliminary results indicate that a telescope of UFSDs could achieve in a short time the accuracy required for the clinical application and therefore encourage further investigations towards the improvement and the optimization of the present prototype.

RIDOS: A new system for online computation of the delivered dose distributions in scanning ion beam therapy.

PURPOSE: To describe a new system for scanned ion beam therapy, named RIDOS (Real-time Ion DOse planning and delivery System), which performs real time delivered dose verification integrating the information from a clinical beam monitoring system with a Graphic Processing Unit (GPU) based dose calculation in patient Computed Tomography. METHODS: A benchmarked dose computation algorithm for scanned ion beams has been parallelized and adapted to run on a GPU architecture. A workstation equipped with a NVIDIA GPU has been interfaced through a National Instruments PXI-crate with the dose delivery system of the Italian National Center of Oncological Hadrontherapy (CNAO) to receive in real-time the measured beam parameters. Data from a patient monitoring system are also collected to associate the respiratory phases with each spot during the delivery of the dose. Using both measured and planned spot properties, RIDOS evaluates during the few seconds of inter-spill time the cumulative delivered and prescribed dose distributions and compares them through a fast γ-index algorithm. RESULTS: The accuracy of the GPU-based algorithms was assessed against the CPU-based ones and the differences were found below 1‰. The cumulative planned and delivered doses are computed at the end of each spill in about 300 ms, while the dose comparison takes approximatively 400 ms. The whole operation provides the results before the next spill starts. CONCLUSIONS: RIDOS system is able to provide a fast computation of the delivered dose in the inter-spill time of the CNAO facility and allows to monitor online the dose deposition accuracy all along the treatment.

'Survival': a simulation toolkit introducing a modular approach for radiobiological evaluations in ion beam therapy.

One major rationale for the application of heavy ion beams in tumour therapy is their increased relative biological effectiveness (RBE). The complex dependencies of the RBE on dose, biological endpoint, position in the field etc require the use of biophysical models in treatment planning and clinical analysis. This study aims to introduce a new software, named 'Survival', to facilitate the radiobiological computations needed in ion therapy. The simulation toolkit was written in C++ and it was developed with a modular architecture in order to easily incorporate different radiobiological models. The following models were successfully implemented: the local effect model (LEM, version I, II and III) and variants of the microdosimetric-kinetic model (MKM). Different numerical evaluation approaches were also implemented: Monte Carlo (MC) numerical methods and a set of faster analytical approximations. Among the possible applications, the toolkit was used to reproduce the RBE versus LET for different ions (proton, He, C, O, Ne) and different cell lines (CHO, HSG). Intercomparison between different models (LEM and MKM) and computational approaches (MC and fast approximations) were performed. The developed software could represent an important tool for the evaluation of the biological effectiveness of charged particles in ion beam therapy, in particular when coupled with treatment simulations. Its modular architecture facilitates benchmarking and inter-comparison between different models and evaluation approaches. The code is open source (GPL2 license) and available at https://github.com/batuff/Survival.

Quality assurance of carbon ion and proton beams: A feasibility study for using the 2D MatriXX detector.

PURPOSE: The quality assurance (QA) procedures in particle therapy centers with active beam scanning make extensive use of films, which do not provide immediate results. The purpose of this work is to verify whether the 2D MatriXX detector by IBA Dosimetry has enough sensitivity to replace films in some of the measurements. METHODS: MatriXX is a commercial detector composed of 32×32 parallel plate ionization chambers designed for pre-treatment dose verification in conventional radiation therapy. The detector and GAFCHROMIC® films were exposed simultaneously to a 131.44MeV proton and a 221.45MeV/u carbon-ion therapeutic beam at the CNAO therapy center of Pavia - Italy, and the results were analyzed and compared. RESULTS: The sensitivity MatriXX on the beam position, beam width and field flatness was investigated. For the first two quantities, a method for correcting systematic uncertainties, dependent on the beam size, was developed allowing to achieve a position resolution equal to 230µm for carbon ions and less than 100µm for protons. The beam size and the field flatness measured using MatriXX were compared with the same quantities measured with the irradiated film, showing a good agreement. CONCLUSIONS: The results indicate that a 2D detector such as MatriXX can be used to measure several parameters of a scanned ion beam quickly and precisely and suggest that the QA would benefit from a new protocol where the MatriXX detector is added to the existing systems.

Axis II disorders, body image and childhood abuse in bariatric surgery candidates.

BACKGROUND AND AIMS: Psychiatric disorders are common in obese patients and they are often considered contraindications for bariatric surgery. In this patients Axis I profile has been widely investigated, while only few studies on Axis II profile are reported. Aim of the study was to examine the prevalence of Axis II psychopathology, to describe the typical body image and to evaluate the prevalence of childhood abuse in bariatric surgery candidates. MATERIALS AND METHODS: A total of 102 consecutive obese patients (77 females) were evaluated by the Structured Clinical Interview for DSM IV which assessed Axis I Disorders. After the exclusion of Axis I Disorders, 50 patients (36 females, BMI: 44.68 ± 9.48 Kg/m2, age: 44.5 ± 11.7 years) were enrolled. All 50 patients received a psychiatric assessment including the Structured Clinical Interview for DSM-IV Axis II Disorders (SCID-II); the Body Uneasiness Test, part a (BUT-A), which assesses body image disorders; the Childhood Trauma Questionnaire (CTQ) as a screening test of childhood maltreatment histories. RESULTS: Nineteen patients (38%) were affected by Axis II disorders. Cluster C disorders, including avoidant, dependent and obsessive-compulsive personality disorders, represented the most common diagnosis (24%). Moreover, 34 patients (68%) showed body image disorders (BID), with a GSI score ≥1.2 and 24 (48%) referred an abuse during childhood. Patients with Axis II disorder or a body image uneasiness or a history of maltreatment during childhood, showed higher BMI in adulthood. CONCLUSIONS: Psychiatric comorbidities in obese patients were not only represented by depression or anxiety (Axis I disorders), but also by personality disorders (Axis II), body image disorders and childhood abuse. The identification of these conditions could improve outcomes of bariatric surgery and represent an indication for a most important psychiatric support before, during and after surgery.

The CNAO dose delivery system for modulated scanning ion beam radiotherapy.

PURPOSE: This paper describes the system for the dose delivery currently used at the Centro Nazionale di Adroterapia Oncologica (CNAO) for ion beam modulated scanning radiotherapy. METHODS: CNAO Foundation, Istituto Nazionale di Fisica Nucleare and University of Torino have designed, built, and commissioned a dose delivery system (DDS) to monitor and guide ion beams accelerated by a dedicated synchrotron and to distribute the dose with a full 3D scanning technique. Protons and carbon ions are provided for a wide range of energies in order to cover a sizable span of treatment depths. The target volume, segmented in several layers orthogonally to the beam direction, is irradiated by thousands of pencil beams which must be steered and held to the prescribed positions until the prescribed number of particles has been delivered. For the CNAO beam lines, these operations are performed by the DDS. The main components of this system are two independent beam monitoring detectors, called BOX1 and BOX2, interfaced with two control systems performing the tasks of real-time fast and slow control, and connected to the scanning magnets and the beam chopper. As a reaction to any condition leading to a potential hazard, a DDS interlock signal is sent to the patient interlock system which immediately stops the irradiation. The essential tasks and operations performed by the DDS are described following the data flow from the treatment planning system through the end of the treatment delivery. RESULTS: The ability of the DDS to guarantee a safe and accurate treatment was validated during the commissioning phase by means of checks of the charge collection efficiency, gain uniformity of the chambers, and 2D dose distribution homogeneity and stability. A high level of reliability and robustness has been proven by three years of system activity needing rarely more than regular maintenance and working with 100% uptime. Four identical and independent DDS devices have been tested showing comparable performances and are presently in use on the CNAO beam lines for clinical activity. CONCLUSIONS: The dose delivery system described in this paper is one among the few worldwide existing systems to operate ion beam for modulated scanning radiotherapy. At the time of writing, it has been used to treat more than 350 patients and it has proven to guide and control the therapeutic pencil beams reaching performances well above clinical requirements. In particular, in terms of dose accuracy and stability, daily quality assurance measurements have shown dose deviations always lower than the acceptance threshold of 5% and 2.5%, respectively.

Relevance of orthostatic posturography for clinical evaluation of hip and knee joint arthroplasty patients.

In order to verify whether orthostatic posturography (OP) can support clinical assessment of total hip (THA) and knee arthroplasty (TKA), 81 subjects with THA and 100 with TKA were recruited and compared with 59 healthy volunteers. All patients were tested one or two days prior to surgery; 42 subjects (20 THA and 22 TKA) were tested again after six months, and 34 (14 THA and 20 TKA) yet again after 12 months. OP was performed using a Kistler 9286A piezoelectric force plate and the following postural parameters (PPs) were adopted on account of their functional meaning: mean velocity and the root mean square of the distance of the centre of pressure (CoP), sway area, and 95% of the CoP power frequency. Eye condition and fatigue related to the test duration were also examined. The three most meaningful PPs were identified and a logarithmic transformation was then applied to these, as well as standardization. Almost all the PP values were higher preoperatively in the patients as compared with the healthy subjects and it was possible to detect many statistically significant differences between patients and healthy subjects. However, when examining the 181 subjects at the preoperative stage, the PPs did not show congruence with the clinical scores as well as they did during follow-up. Therefore, the use of the OP is not recommended to monitor patients undergoing THA or TKA.

Online beam monitoring in the treatment of ocular pathologies at the INFN Laboratori Nazionali del Sud-Catania.

A detector (MOPI) has been developed for the online monitoring of the beam at the Centro di AdroTerapia e Applicazioni Nucleari Avanzate (CATANA), where shallow tumours of the ocular region are treated with 62 MeV protons. At CATANA the beam is passively spread to match the tumour shape. The uniformity of the delivered dose depends on beam geometrical quantities which are checked before each treatment. However, beam instabilities might develop during the irradiation affecting the dose distribution. This paper reports on the use of the MOPI detector to measure the stability of the beam profile during the irradiation in the clinical practice. The results obtained in the treatment of 54 patients are also presented.

Heuristic optimization of the scanning path of particle therapy beams.

Quasidiscrete scanning is a delivery strategy for proton and ion beam therapy in which the beam is turned off when a slice is finished and a new energy must be set but not during the scanning between consecutive spots. Different scanning paths lead to different dose distributions due to the contribution of the unintended transit dose between spots. In this work an algorithm to optimize the scanning path for quasidiscrete scanned beams is presented. The classical simulated annealing algorithm is used. It is a heuristic algorithm frequently used in combinatorial optimization problems, which allows us to obtain nearly optimal solutions in acceptable running times. A study focused on the best choice of operational parameters on which the algorithm performance depends is presented. The convergence properties of the algorithm have been further improved by using the next-neighbor algorithm to generate the starting paths. Scanning paths for two clinical treatments have been optimized. The optimized paths are found to be shorter than the back-and-forth, top-to-bottom (zigzag) paths generally provided by the treatment planning systems. The gamma method has been applied to quantify the improvement achieved on the dose distribution. Results show a reduction of the transit dose when the optimized paths are used. The benefit is clear especially when the fluence per spot is low, as in the case of repainting. The minimization of the transit dose can potentially allow the use of higher beam intensities, thus decreasing the treatment time. The algorithm implemented for this work can optimize efficiently the scanning path of quasidiscrete scanned particle beams. Optimized scanning paths decrease the transit dose and lead to better dose distributions.

The effect of the DNA flanking the lesion on formation of the UvrB-DNA preincision complex. Mechanism for the UvrA-mediated loading of UvrB onto a DNA damaged site.

The UvrB-DNA preincision complex plays a key role in nucleotide excision repair in Escherichia coli. To study the formation of this complex, derivatives of a DNA substrate containing a cholesterol adduct were constructed. Introduction of a single strand nick into either the top or the bottom strand at the 3' side of the adduct stabilized the UvrB-DNA complex, most likely by the release of local stress in the DNA. Removal of both DNA strands up to the 3' incision site still allowed formation of the preincision complex. Similar modifications at the 5' side of the damage, however, gave different results. The introduction of a single strand nick at the 5' incision site completely abolished the UvrA-mediated formation of the UvrB-DNA complex. Deletion of both DNA strands up to the 5' incision site also prevented the UvrA-mediated loading of UvrB onto the damaged site, but UvrB by itself could bind very efficiently. This demonstrates that the UvrB protein is capable of recognizing damage without the matchmaker function of the UvrA protein. Our results also indicate that the UvrA-mediated loading of the UvrB protein is an asymmetric process, which starts at the 5' side of the damage.

The role of ATP binding and hydrolysis by UvrB during nucleotide excision repair.

We have isolated UvrB-DNA complexes by capture of biotinylated damaged DNA substrates on streptavidin-coated magnetic beads. With this method the UvrB-DNA preincision complex remains stable even in the absence of ATP. For the binding of UvrC to the UvrB-DNA complex no cofactor is needed. The subsequent induction of 3' incision does require ATP binding by UvrB but not hydrolysis. This ATP binding induces a conformational change in the DNA, resulting in the appearance of the DNase I-hypersensitive site at the 5' side of the damage. In contrast, the 5' incision is not dependent on ATP binding because it occurs with the same efficiency with ADP. We show with competition experiments that both incision reactions are induced by the binding of the same UvrC molecule. A DNA substrate containing damage close to the 5' end of the damaged strand is specifically bound by UvrB in the absence of UvrA and ATP (Moolenaar, G. F., Monaco, V., van der Marel, G. A., van Boom, J. H., Visse, R., and Goosen, N. (2000) J. Biol. Chem. 275, 8038-8043). To initiate the formation of an active UvrBC-DNA incision complex, however, UvrB first needs to hydrolyze ATP, and subsequently a new ATP molecule must be bound. Implications of these findings for the mechanism of the UvrA-mediated formation of the UvrB-DNA preincision complex will be discussed.

The antimicrobial peptide trichogin and its interaction with phospholipid membranes.

The interaction of the antimicrobial peptide trichogin GA IV with phospholipid bilayers has been studied. A series of analogs of trichogin was synthesized in which the nitroxide spin label, 4-amino-4-carboxy-2,2,6,6-tetramethylpiperidino-1-oxyl (TOAC), replaced one of the three alpha-aminoisobutyric acid (Aib) residues in the sequence. These modified peptides were used to assess the location of different residues of the peptide in a phospholipid bilayer composed of egg phosphatidylcholine containing 0.4 mol% of a fluorescently labelled phospholipid. We demonstrate that the substitution of Aib residues with TOAC does not alter the manner in which the peptide affects membrane curvature or induces vesicle leakage. The proximity of the nitroxide group on the peptide to the 4,4-difluoro-4-bora-3a,4a-diaza-S-indacene (BODIPY) fluorophore attached to the phospholipid was estimated from the extent of quenching of the fluorescence. By this criterion it was concluded that the peptide penetrates into the bilayer and that Aib4 is the most deeply inserted of the Aib residues. The results suggest that the helix axis of the peptide is oriented along the plane of the membrane. All of the peptides were shown to raise the bilayer to the hexagonal phase transition temperature of dipalmitoleoylphosphatidylethanolamine, indicating that they promote positive membrane curvature. This is a property observed with peptides that do not penetrate deeply into the bilayer or are oriented along the bilayer normal. We also demonstrate trichogin-promoted leakage of the aqueous contents of liposomes. These results indicate that the peptides cause bilayer destabilization. The extent of leakage induced by trichogin is very sensitive to the peptide to lipid ratio over a narrow range.

Orientation and immersion depth of a helical lipopeptaibol in membranes using TOAC as an ESR probe.

Trichogin GA IV is a lipopeptaibol antibiotic characterized by the sequence nOct-Aib1-Gly-Leu-Aib4-Gly-Gly-Leu-Aib8-Gly-Ile- Lol (nOct: n-octanoyl; Aib: alpha-aminoisobutyric acid; Lol, leucinol), which exhibits membrane-modifying properties. We synthesized step-by-step by solution methods three trichogin analogues, each with a single Aib --> 2,2,6,6-tetramethylpiperidin-1-oxyl-4-amino-4-carboxylic acid (TOAC) substitution. The similarity in the conformational propensities of the Calpha-tetrasubstituted alpha-amino acids Aib and TOAC allowed us to exploit these analogues to investigate the orientation and therefore the mechanism of action of trichogin in the membranes by the electron spin resonance (ESR) technique. A conformational analysis by Fourier transform ir absorption and CD in different organic solvents and in a membrane-mimetic environment indicated that the conformation of the natural lipopeptaibol remains almost unchanged in the three analogues. Moreover, for all of the analogues permeability measurements revealed membrane-modifying properties comparable to those of trichogin. Our ESR investigation demonstrated that, in liposomes based on phosphatidylcholine, trichogin lays parallel to the membrane surface with its hydrophobic face oriented toward the membrane interior. These results suggest that trichogin might modify membrane permeability via a carpet-like mechanism, at least in liposomes and in the absence of a transmembrane potential.

Determining the occurrence of a 3(10)-helix and an alpha-helix in two different segments of a lipopeptaibol antibiotic using TOAC, a nitroxide spin-labeled C(alpha)-tetrasubstituted alpha-aminoacid.

Trichogin GA IV is a 11-residue lipopeptaibol antibiotic exhibiting membrane modifying properties. We synthesized step-by-step by solution methods three trichogin analogues, each with a double Aib (alpha-aminoisobutyric acid)-->TOAC (2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid) replacement. The strict similarity in the conformational propensities of Aib and TOAC allowed us to exploit these analogues in a detailed investigation of the conformation of this lipopeptaibol in different organic solvents and in a membrane-mimetic environment using in particular the double spin labeling ESR technique. We conclude that the secondary structure in solution remains essentially unchanged if compared to that previously found in the crystal state for trichogin. More specifically, the N-terminal region of the peptide folds in a 3(10)-helix, while the central and C-terminal regions are mainly alpha-helical. An additional, significant proof for the modest plasticity of the trichogin structure was obtained by an X-ray diffraction analysis of the nOct-[TOAC4,8, Leu-OMe11] analogue. For the three analogues permeability measurements revealed membrane-modifying properties comparable to those of natural trichogin.

Solution conformational analysis of amphiphilic helical, synthetic analogs of the lipopeptaibol trichogin GA IV.

The step-by-step synthesis by solution methods of the [Ser2,5,6,9, Leu-OMe11] analog of trichogin GA IV is described. The four Ser residues have been incorporated into the sequence as replacements of the naturally occurring Gly residues to increase the amphiphilicity of the 3D-structure of the lipopeptaibol. A detailed solution conformational analysis has been performed on this undecapeptide and its prototypical [Leu-OMe11] trichogin GA IV analog using FTIR absorption and CD spectroscopies, and two-dimensional NMR under a variety of experimental conditions, including a membrane-mimetic environment. Both peptides adopt a mixed 3(10)/alpha-helical structure, which in the micellar system was found to be less flexible for the Ser-containing analog. For both analogs permeability measurements revealed membrane-modifying properties comparable to those of the natural lipopeptaibol.

Conformation and membrane activity of an analogue of the peptaibol antibiotic trichogin GA IV with a lipophilic amino acid at the N-terminus.

We have synthesized by solution-phase methods two analogues of the 11-residue lipopeptaibol antibiotic trichogin GA IV in which the N-terminal n-octanoyl group is replaced either by an N-acetylated 2-amino-2-methyl-L-undecanoic acid or by an N-acetylated alpha-aminoisobutyric acid. CD, FTIR absorption. and NMR analyses unequivocally show that the main structural features of trichogin GA IV are preserved in these analogues. Since only the peptide containing the lipophilic chain exhibits membrane-modifying properties, these results strongly support the view that moving the long acyl moiety from the Nalpha-blocking group to the side chain of the N-terminal extra-residue does not affect the conformational properties or the membrane activity of trichogin GA IV.

Crystallographic structure of a multiple beta-turn containing, glycine-rich heptapeptide: a synthetic precursor of the lipopeptaibol antibiotic trichodecenin I.

In continuation of our studies on the structure and function of peptaibol antibiotics, the conformational properties of a sequence analogous to that of Trichodecenin I (Z-Gly-Gly-D-Leu-Aib-Gly-D-Ile-D-Leu-OMe, where Z = benzyloxycarbonyl, Aib = alpha-aminoisobutyric acid, and OMe = methyl ester) have been investigated crystallographically. This sequence is the mirror image of the naturally occurring molecule and also of the C-terminal heptapeptide of the related lipopeptaibol Trichogin A IV (where, however, the Leu-OMe residue has replaced the original Leuol residue). The molecule crystallized in the monoclinic system, space group P21, Z = 4, and cell parameters a = 11.610(5), b = 33.342(8), c = 11.735(4) A, beta = 110.42(1) degrees, V = 4257(3) A3. The crystallographic refinement converges at residual values of R = 0.047 and wR2 = 0.134 on F2. In the 1-5 segment the molecular conformation is virtually identical to that one reported from solution nmr studies of a similarly protected sequence [Biopolymers (1995), Vol. 35. pp. 21-29)] and is characterized by beta-turns of type I at Gly1-Gly2, II' at Leu3-Aib4, and I at Aib4-Gly5. In the crystal structure, a beta-sheet-like arrangement is seen at the C-terminus.

N alpha-benzyloxycarbonyl-alpha-aminoisobutyryl-glycyl-L-isoleucyl- L-leucine methyl ester monohydrate.

(Z)-Aib-Gly-L-Ile-L-Leu-OMe.H2O, C27H42N4O7.H2O, is a protected analogue of the C-terminal sequence of the membrane-active peptaibol antibiotic trichogin A IV. The peptide backbone is folded. The urethane carbonyl O atom acts as the acceptor of two intramolecular hydrogen bonds which give rise to a beta bend and to an alpha bend. The geometry of the latter is significantly distorted from that observed in alpha helices. This structure represents the first observation of an alpha bend in a protected tetrapeptide sequence.

Catastro serologico para diagnostico de sifilis. / Serological survey for syphilis diagnosis

Se estudiaron 1876 muestras de suero de ciudadanos, con antigenos para VDRL y para Kahn. Los resultados obtenidos se compararon entre si para confirmar las posibles diferencias de valores obtenidos, y tener una idea porcentual de contaminados con Treponema pallidum