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The advent of multichannel ground-penetrating radar systems capable of acquiring multiview, multistatic, and multifrequency data is offering new possibilities to improve subsurface imaging performance. However, this raises the need for reconstruction approaches capable of handling such sophisticated configurations and the resulting increase in the data volume. Therefore, the challenge lies in identifying proper measurement configurations that balance image quality with the complexity and duration of data acquisition. As a contribution to this topic, the present paper focuses on a measurement system working in reflection mode and composed of an array of antennas, consisting of a transmitting antenna and several receiving antennas, whose spatial offset is comparable to the probing wavelength. Therefore, for each position of the transmitting antenna, a single-view/multistatic configuration is considered. The imaging task is solved by adopting a linear microwave tomographic approach, which provides a qualitative reconstruction of the investigated scenario. In particular, a 3D inverse scattering problem is tackled for an isotropic, homogeneous, lossless, and non-magnetic medium under the Born approximation, considering both single- and multi-frequency data. A preliminary analysis, referring to a 3D free-space reference scenario, is performed in terms of the spectral content of the scattering operator and the system’s point spread function. Finally, an experimental validation under laboratory conditions is presented in order to verify the expected imaging capability of the inversion approach.

Radar imaging from unmanned aerial vehicles (UAVs) is a dynamic research topic attracting huge interest due to its practical fallouts. In this context, this article provides a comprehensive review of the current state of the art and challenges related to UAV-based ground-penetrating radar (GPR) imaging systems. First, a description of the available prototypes is provided in terms of radar technology, UAV platforms, and navigation control devices. Afterward, the paper addresses the main issues affecting the performance of UAV-based GPR imaging systems. such as the control of the UAV platform during the flight to collect high-quality data, the necessity to provide accurate platform position information in terms of probing wavelength, and the mitigation of clutter and other electromagnetic disturbances. A description of the major applicative areas for UAV GPR systems is reported with the aim to show their potential. Furthermore, the main signal-processing approaches currently adopted are detailed and two experimental tests are also reported to prove the actual imaging capabilities. Finally, open challenges and future perspectives regarding this promising technology are discussed.

The paper proposes an analytical study regarding airborne radar imaging performances and accounts for a down-looking radar system moving along parallel lines far, in terms of probing wavelength, from the investigated domain and collecting multi-frequency and multi-monostatic data. The imaging problem is formulated in a constant depth plane by exploiting the Born approximation. Hence, a linear inverse scattering problem is faced by considering both the Adjoint and the Truncated Singular Value Decomposition reconstruction schemes. Analytical and simulated results are provided to state how the achievable performances depend on the measurement configuration. These results are of practical usefulness because, in operative conditions, it is unfeasible to plan a flight grid made up by a high number of closely (in terms of probing wavelength) spaced lines. Hence, the understanding of how the availability of under-sampled data affects the radar imaging allows for a trade-off between operative data collection constrains and reliable reconstructions of the scenario under test.

The present manuscript faces the problem of performing high-resolution Unmanned Aerial Vehicle (UAV) radar imaging in sounder modality, i.e., into the vertical plane defined by the along-tack and the nadir directions. Data are collected by means of a light and compact UAV radar prototype; flight trajectory information is provided by two positioning estimation techniques: standalone Global Positioning System (GPS) and Carrier based Differential Global Positioning System (CDGPS). The radar imaging is formulated as a linear inverse scattering problem and a motion compensation (MoCo) procedure, accounting for GPS or CDGPS positioning, is adopted. The implementation of the imaging scheme, which is based on the Truncated Singular Value Decomposition, is made efficient by the Shift and Zoom approach. Two independent flight tests involving different kind of targets are considered to test the imaging strategy. The results show that the CDGPS supports suitable imaging performance in all the considered test cases. On the other hand, satisfactory performance is also possible by using standalone GPS when the meter-level positioning error exhibits small variations during the radar integration time.

This paper deals with the imaging problem from data collected by means of a microwave photonics-based distributed radar network. The radar network is leveraged on a centralized architecture, which is composed of one central unit (CU) and two transmitting and receiving dual-band remote radar peripherals (RPs), it is capable of collecting monostatic and multistatic phase-coherent data. The imaging is herein formulated as a linear inverse scattering problem and solved in a regularized way through the truncated singular value decomposition inversion scheme. Specifically, two different imaging schemes based on an incoherent fusion of the tomographic images or a fully coherent data processing are herein developed and compared. Experimental tests carried out in a port scenario for imaging both a stationary and a moving target are reported to validate the imaging approach.

This paper deals with 3D and 2D linear inverse scattering approaches based on the Born approximation, and investigates how the model dimensionality influences the imaging performance. The analysis involves dielectric objects hosted in a homogenous and isotropic medium and a multimonostatic/multifrequency measurement configuration. A theoretical study of the spatial resolution is carried out by exploiting the singular value decomposition of 3D and 2D scattering operators. Reconstruction results obtained from synthetic data generated by using a 3D full-wave electromagnetic simulator are reported to support the conclusions drawn from the analysis of resolution limits. The presented analysis corroborates that 3D and 2D inversion approaches have almost identical imaging performance, unless data are severely corrupted by the noise.

This paper deals with a feasibility study assessing the reconstruction capabilities of a small Multicopter-Unmanned Aerial Vehicle (M-UAV) based radar system, whose flight positions are determined by using the Carrier-Phase Differential GPS (CDGPS) technique. The paper describes the overall radar imaging system in terms of both hardware devices and data processing strategy for the case of a single flight track. The data processing is cast as the solution of an inverse scattering problem and is able to provide focused images of on surface targets. In particular, the reconstruction is approached through the adjoint of the functional operator linking the unknown contrast function to the scattered field data, which is computed by taking into account the actual flight positions provided by the CDGPS technique. For this inverse problem, we provide an analysis of the reconstruction capabilities by showing the effect of the radar parameters, the flight altitude and the spatial offset between target and flight path on the resolution limits. A measurement campaign is carried out to demonstrate the imaging capabilities in controlled conditions. Experimental results referred to two surveys performed on the same scene but at two different UAV altitudes verify the consistency of these results with the theoretical resolution analysis.

This work is aimed at showing the present capabilities and future potentialities of an imaging radar system that can be mounted onboard flexible aerial platforms, such as helicopters or small airplanes, and may operate in the UHF and VHF frequency bands as Sounder and as Synthetic Aperture Radar (SAR). More specifically, the Sounder operates at 165 MHz, whereas the SAR may operate either at 450 MHz or at 860 MHz. In the work, we present the first results relevant to a set of Sounder and SAR data collected by the radar during a helicopter-borne campaign conducted in 2018 over a desert area in Erfoud, Morocco, just after the conclusion of a system upgrading procedure. In particular, a first analysis of the focusing capabilities of the Sounder mode and of the polarimetric and interferometric capabilities of the SAR mode is conducted. The overall system, originally developed by CO.RI.S.T.A. according to a ASI funding set up in 2010, has been upgraded in the frame of a contract signed in 2015 between ASI and different private and public Italian Research Institutes and Universities, namely CO.RI.S.T.A., IREA-CNR, Politecnico di Milano and University of Trento.

To evaluate the effectiveness of belimumab in different joint and skin phenotypes of systemic lupus erythematosus (SLE). The BeRLiSS-JS 2.0 is a decade-long observational study including adult SLE patients from 14 Italian Centers treated with belimumab (intravenous/subcutaneous) stratified by articular (nondeforming nonerosive arthritis -NDNE-, Jaccoud's arthropathy, Rhupus) and cutaneous phenotypes (acute -ACLE-, subacute -SCLE-, and chronic cutaneous lupus erythematosus -CCLE-, and nonspecific manifestations). Outcome variables measured every 6 months up to 36 months included Disease Activity Score-28 joints (DAS28) and Cutaneous Lupus Erythematosus Disease Area and Severity Index (CLASI) scores, remission rates (DAS28<2.6; CLASI-A=0), and prednisone intake (mg/day). Of 443 patients, 221 (49.9%) had NDNE, 30 (6.8%) Jaccoud's arthropathy, 21 (4.7%) rhupus, 112 (25.3%) had ACLE, 54 (12.2%) SCLE, and 18 (4.1%) CCLE. At 6 months a significant decrease of DAS28 was observed in NDNE ( ) and by CLASI-A in ACLE and SCLE (both ). Non-specific cutaneous manifestations did not improve significantly. CLASI-D scores remained stable over 36 months. Remission rates were higher in NDNE and ACLE patients (at 6 months: NDNE 59.6%, Jaccoud's 18.8%, rhupus 30.3% - p=0.002; at 18 months: ACLE 75.9%, SCLE 56.4%, CCLE 33.3% - p=0.018). Daily prednisone dosage decreased in all organ-specific phenotypes, but more pronouncedly in patients with NDNE, ACLE, and SCLE. Higher baseline CLASI-A and DAS28 and CLASI-D were associated with lower remission rates. Treatment with belimumab was associated with reduced disease activity and increased remission especially in NDNE and ACLE patients. Glucocorticoid-sparing effect was also found.

ObjectiveTo assess the effectiveness of belimumab (BEL) in improving anaemia, thrombocytopenia, lymphopenia and leucopenia in patients with SLE.MethodsThe BeRLiSS (Belimumab in Real Life Setting Study) 2.0 cohort included patients with SLE from 14 Italian referral centres treated with BEL for active joint or skin involvement, based on physician judgement, between June 2013 and May 2024. Clinical and laboratory parameters were recorded at baseline and every 6 months. Patients were eligible if they had baseline haematological abnormalities defined according to British Isles Lupus Assessment Group (BILAG) (grade C or higher): haemoglobin (Hb) ≤10.9 g/dL, platelets (Plts) ≤149×109/L, lymphocytes (Lym) ≤1.0×109/L or leucocytes (Leuc) ≤3.0×109/L. Follow-up data up to month 48 were available for 33 patients with anaemia, 20 with thrombocytopenia, 44 with lymphopenia and 18 with leucopenia.ResultsAt baseline, 76 patients had anaemia, 44 thrombocytopenia, 107 lymphopenia and 53 leucopenia. Hb levels increased significantly from 9.9±0.6 g/dL to 11.7±1.4 g/dL at month 48 (p<0.001). Platelet counts rose from 110.2±38.1×109/L to 176.6±88.7×109/L (p=0.004), Lym counts from 0.72±0.21×109/L to 1.14±0.45×109/L (p<0.001) and leucocyte counts from 2.437±0.533×109/L to 4.732±1.897×109/L at 48 months (p<0.001). Improvement in Hb (p=0.97), Plts (p=0.12), Lym (p=0.86) and Leuc (p=0.73) was similar regardless of the use of concomitant immunosuppressants. Glucocorticoid (GC) doses decreased significantly across all manifestations, except for leucopenia: anaemia (12.9±12.1 to 3.6±4.9 mg/day, p=0.003), thrombocytopenia (10.8±9.6 to 4.4±5.5 mg/day, p=0.004), lymphopenia (10.6±8.6 to 3.1±3.2 mg/day, p<0.001). Proportion of GC users declined over 48 months: anaemia 96.1–60.7%, thrombocytopenia 93.1–80%, lymphopenia 96.3–70.3% and leucopenia 95.3–80%.ConclusionIn this real-world cohort, BEL treatment was associated with improvement in anaemia, thrombocytopenia, lymphopenia and leucopenia with over half of patients achieving normalisation of blood counts. Haematological responses were similar regardless of concomitant immunosuppressive therapy, supporting the role of BEL as a therapeutic option for haematological abnormalities in SLE.