Resonant opto-mechanical modulators and switches by femtosecond laser micromachining.

In this work we demonstrate novel integrated-optics modulators and switches, realized in a glass substrate by femtosecond laser pulses. These devices are based on oscillating microcantilevers, machined by water-assisted laser ablation. Single-mode optical waveguides are laser-inscribed inside the cantilever beam and continue in the substrate beyond the cantilever's tip. By exciting the resonant oscillation of the mechanical structure, coupling between the waveguide segments is varied in time. Operation frequencies are in the range of tens of kilohertz, thus they markedly overcome the response-time limitation of other glass-based modulators, which rely on the thermo-optic effect. These components may be integrated in more complex waveguide circuits or optofluidic lab-on-chips, to provide periodic and high-frequency modulation of the optical signals.

Computed Tomography Angiography Combined With Knowledge-Based Iterative Algorithm for Transcatheter Aortic Valve Implantation Planning: Image Quality and Radiation Dose Exposure With Low-kV and Low-Contrast-Medium Protocol.

OBJECTIVE: To evaluate image quality and radiation dose exposure of low-kV setting and low-volume contrast medium (CM) computed tomography angiography (CTA) protocol for transcatheter aortic valve implantation (TAVI) planning in comparison with standard CTA protocol. METHODS: Sixty-patients were examined with 256-row MDCT for TAVI planning: 32 patients (study group) were evaluated using 80-kV electrocardiogram-gated protocol with 60 mL of CM and IMR reconstruction; 28 patients underwent a standard electrocardiogram-gated CTA study (100 kV; 80 mL of CM; iDose4 reconstruction). Subjective and objective image quality was evaluated in each patient at different aortic levels. Finally, we collected radiation dose exposure data (CT dose index and dose-length product) of both groups. RESULTS: In study protocol, significant higher mean attenuation values were achieved in all measurements compared with the standard protocol. There were no significant differences in the subjective image quality evaluation in both groups. Mean dose-length product of study group was 56% lower than in the control one (P < 0.0001). CONCLUSION: Low-kV and low-CM volume CTA, combined with IMR, allows to correctly performing TAVI planning with high-quality images and significant radiation dose reduction compared with standard CTA protocol.

Experimental Investigation of Quantum Decay at Short, Intermediate, and Long Times via Integrated Photonics.

The decay of an unstable system is usually described by an exponential law. Quantum mechanics predicts strong deviations of the survival probability from the exponential: Indeed, the decay is initially quadratic, while at very large times it follows a power law, with superimposed oscillations. The latter regime is particularly elusive and difficult to observe. Here we employ arrays of single-mode optical waveguides, fabricated by femtosecond laser direct inscription, to implement quantum systems where a discrete state is coupled and can decay into a continuum. The optical modes correspond to distinct quantum states of the photon, and the temporal evolution of the quantum system is mapped into the spatial propagation coordinate. By injecting coherent light states in the fabricated photonic structures and by measuring a small scattered fraction of such light with an unprecedented dynamic range, we are able to experimentally observe not only the exponential decay regime, but also the quadratic Zeno region and the power-law decay at long evolution times.

Evaluation of image quality and radiation dose saving comparing knowledge model-based iterative reconstruction on 80-kV CT pulmonary angiography (CTPA) with hybrid iterative reconstruction on 100-kV CT.

OBJECTIVES: To evaluate dose reduction and image quality of 80-kV CT pulmonary angiography (CTPA) reconstructed with knowledge model-based iterative reconstruction (IMR), and compared with 100-kV CTPA with hybrid iterative reconstruction (iDose4). MATERIALS AND METHODS: One hundred and fifty-one patients were prospectively investigated for pulmonary embolism; a study group of 76 patients underwent low-kV setting (80 kV, automated mAs) CTPA study, while a control group of 75 patients underwent standard CTPA protocol (100 kV; automated mAs); all patients were examined on 256 MDCT scanner (Philips iCTelite). Study group images were reconstructed using IMR while the control group ones with iDose4. CTDIvol, DLP, and ED were evaluated. Region of interests placed in the main pulmonary vessels evaluated vascular enhancement (HU); signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. RESULTS: Compared to iDose4-CTPA, low-kV IMR-CTPA presented lower CTDIvol (6.41 ± 0.84 vs 9.68 ± 3.5 mGy) and DLP (248.24 ± 3.2 vs 352.4 ± 3.59 mGy × cm), with ED of 3.48 ± 1.2 vs 4.93 ± 1.8 mSv. Moreover, IMR-CTPA showed higher values of attenuation (670.91 ± 9.09 HU vs 292.61 ± 15.5 HU) and a significantly higher SNR (p < 0.0001) and CNR (p < 0.0001).The subjective image quality of low-kV IMR-CTPA was also higher compared with iDose4-CTPA (p < 0.0001). CONCLUSIONS: Low-dose CTPA (80 kV and automated mAs modulation) reconstructed with IMR represents a feasible protocol for the diagnosis of pulmonary embolism in the emergency setting, achieving high image quality with low noise, and a significant dose reduction within adequate reconstruction times(≤ 120 s).

Diagnostic efficacy of model-based iterative reconstruction algorithm in an assessment of coronary artery in comparison with standard hybrid-Iterative reconstruction algorithm: dose reduction and image quality.

PURPOSE: To evaluate the image quality and radiation dose exposure of low-dose coronary CTA (cCTA) study, reconstructed with the new model-based iterative reconstruction algorithm (IMR), compared with standard hybrid-iterative reconstruction (iDose4) cCTA in patients with suspected coronary artery disease. MATERIALS AND METHODS: Ninety-eight patients with an indication for coronary CT study were prospectively enrolled. Fifty-two patients (study group) underwent 256-MDCT low-dose cCTA (80 kV; automated-mAs; 60 mL of CM, 350 mgL/mL) with prospective ECG-triggering acquisition and IMR. A control group of 46 patients underwent 256-MDCT standard prospective ECG-gated protocol (100 kV; automated-mAs; 70 mL of CM, 400 mgL/mL; iDose4). Subjective and objective image quality (attenuation value, SD, SNR and CNR) were evaluated by two radiologists subjectively. Radiation dose exposure was quantified as DLP, CTDIvol and ED. RESULTS: Mean values of mAs were significantly lower for IMR-cCTA (167 ± 62 mAs) compared to iDose-cCTA (278 ± 55 mAs), p < 0.001. With a significant reduction of 38% in radiation dose exposure (DLP: IMR-cCTA 91.7 ± 26 mGy cm vs. iDose-cCTA 148.6 ± 35 mGy cm; p value < 0.001), despite the use of different CM, we found higher mean attenuation values of the coronary arteries in IMR group compared to iDose4 (mean density in LAD: 491HU IMR-cCTA vs. 443HU iDose-cCTA; p = 0.03). We observed a significant higher value of SNR and CNR in study group due to a lower noise level. Qualitative analysis did not reveal any significant differences between the two groups (p = 0.23). CONCLUSIONS: Low-dose cCTA study combined with IMR reconstruction allows to correctly evaluate coronary arteries disease, offering high-quality images and significant radiation dose exposure reduction (38%), as compared to standard cCTA protocol.

Symmetric polarization-insensitive directional couplers fabricated by femtosecond laser writing.

We study analytically the polarization behaviour of directional couplers composed of birefringent waveguides, showing that they can induce polarization transformations that depend on the specific input-output path considered. On the basis of this study, we propose and demonstrate experimentally, by femtosecond laser writing, directional couplers that yield a polarization-independent power splitting and, at the same time, preserve the polarization state of the propagating light. More in detail, we devise two different approaches to realize such devices: the first one is based on local birefringence engineering by additional refractive index modification tracks, while the second one exploits ultra-low birefringence waveguides (b = 1.2 × 10-6), obtained by thermal annealing.

Particle statistics affects quantum decay and Fano interference.

Quantum mechanical decay, Fano interference, and bound states with energy in the continuum are ubiquitous phenomena in different areas of physics. Here we experimentally demonstrate that particle statistics strongly affects quantum mechanical decay in a multiparticle system. By considering propagation of two-photon states in engineered photonic lattices, we simulate quantum decay of two noninteracting particles in a multilevel Fano-Anderson model. Remarkably, when the system sustains a bound state in the continuum, fractional decay is observed for bosonic particles, but not for fermionic ones. Complete decay in the fermionic case arises because of the Pauli exclusion principle, which forbids the bound state to be occupied by the two fermions. Our experiment indicates that particle statistics can tune many-body quantum decay from fractional to complete.

Comparative evaluation of CT-based and respiratory-gated PET/CT-based planning target volume (PTV) in the definition of radiation treatment planning in lung cancer: preliminary results.

PURPOSE: The aim of this study was to compare planning target volume (PTV) defined on respiratory-gated positron emission tomography (PET)/CT (RG-PET/CT) to PTV based on ungated free-breathing CT and to evaluate if RG-PET/CT can be useful to personalize PTV by tailoring the target volume to the lesion motion in lung cancer patients. METHODS: Thirteen lung cancer patients (six men, mean age 70.0 years, 1 small cell lung cancer, 12 non-small cell lung cancer) who were candidates for radiation therapy were prospectively enrolled and submitted to RG-PET/CT. Ungated free-breathing CT images obtained during a PET/CT study were visually contoured by the radiation oncologist to define standard clinical target volumes (CTV1). Standard PTV (PTV1) resulted from CTV1 with the addition of 1-cm expansion of margins in all directions. RG-PET/CT images were contoured by the nuclear medicine physician and radiation oncologist according to a standardized institutional protocol for contouring gated images. Each CT and PET image of the patient's respiratory cycle phases was contoured to obtain the RG-CT-based CTV (CTV2) and the RG-PET/CT-based CTV (CTV3), respectively. RG-CT-based and RG-PET/CT-based PTV (PTV2 and PTV3, respectively) were then derived from gated CTVs with a margin expansion of 7-8 mm in head to feet direction and 5 mm in anterior to posterior and left to right direction. The portions of gated PTV2 and PTV3 geometrically not encompassed in PTV1 (PTV2 out PTV1 and PTV3 out PTV1) were also calculated. RESULTS: Mean ± SD CTV1, CTV2 and CTV3 were 30.5 ± 33.2, 43.1 ± 43.2 and 44.8 ± 45.2 ml, respectively. CTV1 was significantly smaller than CTV2 and CTV3 (p = 0.017 and 0.009 with Student's t test, respectively). No significant difference was found between CTV2 and CTV3. Mean ± SD of PTV1, PTV2 and PTV3 were 118.7 ± 94.1, 93.8 ± 80.2 and 97.0 ± 83.9 ml, respectively. PTV1 was significantly larger than PTV2 and PTV3 (p = 0.038 and 0.043 with Student's t test, respectively). No significant difference was found between PTV2 and PTV3. Mean ± SD values of PTV2 out PTV1 and PTV3 out PTV1 were 12.8 ± 25.4 and 14.3 ± 25.9 ml, respectively. The percentage values of PTV2 out PTV1 and PTV3 out PTV1 were not lower than 10 % of PTV1 in 6/13 cases (46.2 %) and than 20 % in 3/13 cases (23.1 %). CONCLUSION: Our preliminary data showed that RG-PET/CT in lung cancer can affect not only the volume of PTV but also its shape, as demonstrated by the assessment of gated PTVs outside standard PTV. The use of a gating technique is thus crucial for better delineating PTV by tailoring the target volume to the lesion motion in lung cancer patients.

Dosimetric evaluation of a 256-slice computed tomography scanner.

PURPOSE: This study evaluated the effectiveness of patient dose reduction tools on a 256-slice computed tomography scanner (Brilliance iCT, Philips). MATERIALS AND METHODS: The performance of the Brilliance iCT scanner was described in terms of cumulative dose and dose-normalised contrast-to-noise ratio (CNRD). The efficiency of automatic tube current modulation (Z-Dom and D-Dom), shaping filters (SmartShape and IntelliBeam) and asymmetric collimator (Eclipse) was evaluated using appropriate phantoms. RESULTS: The scattered radiation contribution from the peripheral regions to the cumulative dose is not negligible. The CNRD is 20 % better compared to a traditional 16-slice scanner, with a dose reduction of 40 %. The application of shaping filters decreases the dose in the peripheral regions. The application of D-Dom and Z-Dom modulations reduces the current-time product (mAs) values by 23 and 18 %, respectively, but they are not yet integrated. The over-ranging effect is not negligible, despite the use of an Eclipse asymmetric collimator. CONCLUSIONS: Brilliance iCT dose reduction tools are efficient, but should be analysed carefully and used correctly.

General rules for bosonic bunching in multimode interferometers.

We perform a comprehensive set of experiments that characterize bosonic bunching of up to three photons in interferometers of up to 16 modes. Our experiments verify two rules that govern bosonic bunching. The first rule, obtained recently, predicts the average behavior of the bunching probability and is known as the bosonic birthday paradox. The second rule is new and establishes a n!-factor quantum enhancement for the probability that all n bosons bunch in a single output mode, with respect to the case of distinguishable bosons. In addition to its fundamental importance in phenomena such as Bose-Einstein condensation, bosonic bunching can be exploited in applications such as linear optical quantum computing and quantum-enhanced metrology.

Safety and effectiveness of prilocaine for spinal anesthesia in day surgery setting: a retrospective study on a sample of 3291 patients.

Spinal anesthesia is considered safe and reliable for most surgical procedures involving the lower part of the body, but its use in the ambulatory setting requires drugs with rapid onset and regression of the motor and sensory block-like prilocaine.The purpose of this study is to retrospectively analyze data from 3291 procedures recorded in our institutional database, to better define the safety profile of spinal prilocaine and the incidence of complications and side effects.All clinical data, prospectively collected from 2011 to 2019 in an Italian tertiary hospital, of patients treated with spinal anesthesia performed with 40 mg of hyperbaric 2% prilocaine, according to our internal protocol of day surgery, were analyzed.Surgical procedures included saphenectomy (28.5%, n = 937), knee arthroscopy (26.8%, n = 882), proctologic surgery (15.16%, n = 499), and inguinal canal surgery (14.9%, n = 491).Anesthesia-related complication was represented by urinary retention (1.09%, n = 36), lipotimia (0.75%, n = 25), and postoperative nausea (0.33%, n = 11); arrhythmic events were uncommon (0.18%, n = 6). One case of persistent hypotension and 2 cases of persistent hypertension were reported.Persistent motor or sensory block (lasting more than 5 h) was experienced by 7 patients. One patient (0.03%), who underwent knee arthroscopy, experienced pelvic pain lasting for 6 h, compatible with a transient neurological symptom.Proctologic surgery was a factor associated with unplanned admission due to anesthesia-related complications (OR = 4.9; 95% CI: 2-14%).The number of complications related to the method was low as well as the need for hospitalization. This drug is valid and safe for the most performed day surgery procedures; however, further trials are needed to investigate the incidence of complications in the days following the procedure.

Experimental certification of contextuality, coherence, and dimension in a programmable universal photonic processor.

Quantum superposition of high-dimensional states enables both computational speed-up and security in cryptographic protocols. However, the exponential complexity of tomographic processes makes certification of these properties a challenging task. In this work, we experimentally certify coherence witnesses tailored for quantum systems of increasing dimension using pairwise overlap measurements enabled by a six-mode universal photonic processor fabricated with a femtosecond laser writing technology. In particular, we show the effectiveness of the proposed coherence and dimension witnesses for qudits of dimensions up to 5. We also demonstrate advantage in a quantum interrogation task and show it is fueled by quantum contextuality. Our experimental results testify to the efficiency of this approach for the certification of quantum properties in programmable integrated photonic platforms.

Two-particle bosonic-fermionic quantum walk via integrated photonics.

Quantum walk represents one of the most promising resources for the simulation of physical quantum systems, and has also emerged as an alternative to the standard circuit model for quantum computing. Here we investigate how the particle statistics, either bosonic or fermionic, influences a two-particle discrete quantum walk. Such an experiment has been realized by exploiting polarization entanglement to simulate the bunching-antibunching feature of noninteracting bosons and fermions. To this scope a novel three-dimensional geometry for the waveguide circuit is introduced, which allows accurate polarization independent behavior, maintaining remarkable control on both phase and balancement.

Inadvertent intra-arterial catheterisation using ultrasound guidance and endocavitary electrocardiography in a paediatric patient.

Venous access in small infants is difficult and central venous catheter placed into the brachiocephalic vein is often the preferred approach. Ultrasound guided vein cannulation is standard practice and endocavitary electrocardiography is a reliable catheter tip location method. We report a not immediately recognised 2 month old case of inadvertent intra-arterial catheterisation with a 3 Fr - 8 cm catheter during right innominate vein cannulation under ultrasound guidance. Endocavitary electrocardiography showed an increased amplitude P wave with a low P/R wave ratio but further insertion of the catheter resulted in a reduction of the P wave amplitude. At ultrasound re-evaluation of the innominate vein, the catheter seemed to be inside the vessel into the proximal part of the vein, but distally appeared to surpass the vein to get into the brachiocephalic artery at the level of the bifurcation of the right common carotid artery and the right subclavian artery. Cardiac ultrasound from the suprasternal notch view identified the catheter into the aortic arch. Contrast-enhanced CT scan with 3D reconstruction confirmed the intra-arterial catheterisation and showed that the innominate vein was shifted and partially compressed but not transfixed by the catheter. The catheter was non-surgically removed uneventfully. During innominate vein cannulation the catheter cannot always be visualised into the distal tract of the vein and the maximal P wave may have a low P/R ratio; a chest X-ray can identify intra-arterial but false negative results are possible. We recommend always using a real time ultrasound tip navigation and location protocol, like the Neo-ECHOTIP protocol, to confirm the correct position of the guidewire and the catheter. If the catheter cannot be identified inside the venous system, we suggest systematically visualising the aortic arch from the suprasternal notch view and the aortic root from the parasternal view to identify arterial malposition.

Three-dimensional Mach-Zehnder interferometer in a microfluidic chip for spatially-resolved label-free detection.

Ultrafast laser writing of waveguides in glasses is a very flexible and simple method for direct on-chip integration of photonic devices. In this work we present a monolithic optofluidic device in fused silica providing label-free and spatially-resolved sensing in a microfluidic channel. A Mach-Zehnder interferometer is inscribed with the sensing arm orthogonally crossing the microfluidic channel and the reference arm passing over it. The interferometer is integrated either with a microchannel fabricated by femtosecond laser technology or into a commercial lab-on-chip for capillary electrophoresis. The device layout, made possible by the unique three-dimensional capabilities of the technique, enables label-free sensing of samples flowing in the microchannel with spatial resolution of about 10 microm and limit of detection down to 10(-4) RIU.

Polarization entangled state measurement on a chip.

The emerging strategy to overcome the limitations of bulk quantum optics consists of taking advantage of the robustness and compactness achievable by integrated waveguide technology. Here we report the realization of a directional coupler, fabricated by femtosecond laser waveguide writing, acting as an integrated beam splitter able to support polarization-encoded qubits. This maskless and single step technique allows us to realize circular transverse waveguide profiles which are able to support the propagation of gaussian modes with any polarization state. Using this device, we demonstrate quantum interference with polarization-entangled states and singlet state projection.

Editorial for the Special Issue on Femtosecond Laser Micromachining for Photonics Applications.

Femtosecond laser pulses have proven, in the recent years, their formidable potential as a micromachining tool applicable to a variety of materials [...].

Integrated Optofluidic Chip for Oscillatory Microrheology.

We propose and demonstrate an on-chip optofluidic device allowing active oscillatory microrheological measurements with sub-µL sample volume, low cost and high flexibility. Thanks to the use of this optofluidic microrheometer it is possible to measure the viscoelastic properties of complex fluids in the frequency range 0.01-10 Hz at different temperatures. The system is based on the optical forces exerted on a microbead by two counterpropagating infrared laser beams. The core elements of the optical part, integrated waveguides and an optical modulator, are fabricated by fs-laser writing on a glass substrate. The system performance is validated by measuring viscoelastic solutions of aqueous worm-like micelles composed by Cetylpyridinium Chloride (CPyCl) and Sodium Salicylate (NaSal).

Model observers for Low Contrast Detectability evaluation in dynamic angiography: A feasible approach.

PURPOSE: To evaluate the feasibility of spatio-temporal generalisation of mathematical methods for protocol optimisation in interventional radiology. MATERIALS AND METHODS: Two model observers were considered:Furthermore, Low Contrast Detectability (LCD) was evaluated with a generalised statistical method by taking into account the noise integration capability of the human eye. A series of two alternative force choices (2AFC) experiments performed by four observers were used to evaluate the reliability of the proposed models. The evaluation of the mathematical methods was performed by comparing their results to the human observer performances in two steps: 1. Firstly, a series of simulated images were used to tune the models 2. In the second phase, tuned models were applied both to simulated images and actual images obtained with a commercial phantom to evaluate detectability scores. RESULTS: Evaluation with simulated images shows a good agreement with 2AFC results (RMSE < 10%). Phantom-based evaluations show a general decrease of such agreement, characterized by an RMSE lower than 16%. CONCLUSIONS: The agreement with human observer experiments supports the feasibility of the proposed generalisations. Thus, they could be introduced in quality control programmes for a deeper protocol-characterisation or for clinical protocol-optimization when dynamic images are involved.

Postoperative analgesia and early functional recovery after day-case anterior cruciate ligament reconstruction: a randomized trial on local anesthetic delivery methods for continuous infusion adductor canal block.

BACKGROUND: This study assessed the effects of different local anesthetic delivery techniques for continuous adductor canal block, after arthroscopic day-case anterior cruciate ligament reconstruction (ACLR). METHODS: We enrolled 80 patients to randomly receive a ropivacaine 0.2% infusion 6 mL per hour through an adductor canal catheter by an electronic pump as follow: intermittent automatic bolus (intermittent group, N.=40) versus continuous infusion (continuous group, N.=40). Patient controlled bolus was 4 mL, lock out 20 minutes. Primary endpoint was postoperative pain by a numerical rating scale (NRS), secondary endpoints were rescue local anesthetic dose, opioid consumption, and physical performance at 72 h. A P<0.05 was considered significant. RESULTS: No difference was found between the groups in NRS, opioid consumption, and physical performance at 72 h. The intermittent group required significantly less local anesthetic than continuous group throughout the postoperative period; the median [IQR (range)] at 24 h was 149 [140-164 (140-227)] mL in the intermittent group versus 165 [147-210 (140-280)] mL in the continuous group (P=0.004). At 48 h it was 295 [284-310 (280-367)] mL in the intermittent group versus 308 [296-367 (284-500)] mL in the continuous group (P=0.002), while at 72 h it was 432 [426-450 (320-528)] mL in the intermittent group and 452 [436-487 (412-671)] mL in the continuous group respectively (P<0.001). CONCLUSIONS: Intermittent boluses did not provide superior analgesia over continuous infusion for adductor canal block after outpatient ACLR, but significantly decreased the local anesthetic consumption. Both techniques are suitable for the early functional recovery.