To improve vessel contrast in high-resolution susceptibility-based brain venography, an automatic phase contrast enhancing procedure is proposed, based on a new phase mask filter suitable for maximizing contrast of venous MR signals. The effectiveness of the new approach was assessed both on digital phantoms and on acquired MR human brain images, and then compared with venographic results of phase masking methods in recent literature. The digital phantom consisted of a simulated MR dataset with given signal-to-noise ratios (SNRs), while real human data were collected by scanning healthy volunteers with a 3.0-T MR system and a 3D gradient echo pulse sequence. The new phase mask (NM) was more effective than the conventional mask (CM) both on the digital phantoms and on the acquired MR images. A quantitative comparison based on phantom venograms indicates how this phase enhancement can lead to a significant increase in the contrast-to-noise ratio (CNR) for all considered phase values as well as for all vessel sizes of clinical interest. Likewise, the in vivo brain venograms reveal a better depiction of the smallest venous vessels and the enhancement of many details undetectable in conventional venograms.

Aim of this work was to carry out a first clinical validation of a new ultrasound (US)-based approach to bone densitometry of lumbar spine. A total of 290 female patients were enrolled for this study (45-75 years of age, body mass index (BMI)<40 kg/m(2)) and all of them underwent two different diagnostic investigations: a lumbar DXA (dual-energy X-ray absorptiometry) and an US scan of the same vertebras, performed with an echographic device configured for the acquisition of both echographic images and unfiltered radiofrequency signals. US data analysis was carried out through an innovative algorithm, whose main features include: a) measurements are always performed on a specific region of interest of the vertebra, identified on the basis of both morphologic and spectral characteristics; b) analysis takes into account patient BMI; c) the algorithm is integrated with a reference database containing model acquisitions for different combinations of patient age, sex and BMI. Accuracy of final algorithm output, represented by the same diagnostic parameters of a DXA investigation, was evaluated through a direct comparison with DXA results. For 84.5% of the patients US diagnosis (osteoporotic, osteopenic, healthy) coincided with the corresponding DXA one and this accuracy level was not appreciably influenced by patient age nor by BMI. The proposed approach represents the first US method for osteoporosis diagnosis which is directly applicable on spine and has the potential to be effectively used for population mass screenings.

Vertebral morphometry is a commonclinically-used method for vertebral fracture detection andclassification, based on height measurements of vertebralbodies in radiographic images. This method is quantitativeand does not require specific operator skills, but its actualaccuracy is affected by errors made during the timeconsumingmanual or semi-automatic measurements. In thispaper, we propose an innovative fully automatic approach tovertebral morphometry. A novel algorithm, based on a localphase symmetry measure and an "Active Shape Model",was implemented and tested on lateral X-ray radiographs of50 patients. Thoracic and lumbar vertebral bodies in eachimage were independently segmented and measured by boththe automatic algorithm and an experienced radiologist,whose manually-obtained results were assumed as theground truth. The algorithm showed reasonably low errorrates regarding both vertebral localization and morphometricmeasurements with a sensitivity of 86.5% and a perfectspecificity of 100%, because no false positive were present.Furthermore, its performance did not appreciably worsen onpoor quality images, emphasizing a significant potential fora prompt translation into clinical routine.

We investigated the possible clinical feasibility and accuracy of an innovative ultrasound (US) method for diagnosis of osteoporosis of the spine. A total of 342 female patients (aged 51-60 y) underwent spinal dual X-ray absorptiometry and abdominal echographic scanning of the lumbar spine. Recruited patients were subdivided into a reference database used for US spectral model construction and a study population for repeatability and accuracy evaluation. US images and radiofrequency signals were analyzed via a new fully automatic algorithm that performed a series of spectral and statistical analyses, providing a novel diagnostic parameter called the osteoporosis score (O.S.). If dual X-ray absorptiometry is assumed to be the gold standard reference, the accuracy of O.S.-based diagnoses was 91.1%, with k = 0.859 (p < 0.0001). Significant correlations were also found between O.S.-estimated bone mineral densities and corresponding dual X-ray absorptiometry values, with r(2) values up to 0.73 and a root mean square error of 6.3%-9.3%. The results obtained suggest that the proposed method has the potential for future routine application in US-based diagnosis of osteoporosis. (C) 2015 World Federation for Ultrasound in Medicine & Biology.

Current imaging methods for catheter position monitoring during minimally invasive surgery do not provide an effective support to surgeons, often resulting in the choice of more invasive procedures. This study was conducted to demonstrate the feasibility of non-ionizing monitoring of endovascular devices through embedded quantitative ultrasound (QUS) methods, providing catheter self-localization with respect to selected anatomical structures. QUS-based algorithms for real-time automatic tracking of device position were developed and validated on in vitro and ex vivo phantoms. A trans-esophageal ultrasound probe was adapted to simulate an endovascular device equipped with an intravascular ultrasound probe. B-mode images were acquired and processed in real time by means of a new algorithm for accurate measurement of device position. After off-line verification, automatic position calculation was found to be correct in 96% and 94% of computed frames in the in vitro and ex vivo phantoms, respectively. The average errors of distance measurements (bias +/- 2SD) in a 41-step 10-cm-long parabolic pathway were 0.76 +/- 3.75 mm or 0.52 +/- 3.20 mm, depending on algorithm implementations. Our results showed the effectiveness of QUS-based tracking algorithms for real-time automatic calculation and display of endovascular system position. The method, validated for the case of an endoclamp balloon catheter, can be easily extended to most endovascular surgical systems.

Prototypal software algorithms for advanced spectral analysis of echographic images were developed to perform automatic detection of simulated tumor masses at two different pathological stages. Previously published works documented the possibility of characterizing macroscopic variation of mechanical properties of tissues through elastographic techniques, using different imaging modalities, including ultrasound (US); however, the accuracy of US-based elastography remains affected by the variable manual modality of the applied compression and several attempts are under investigation to overcome this limitation. Quantitative US (QUS), such as Fourier- and wavelet-based analyses of the RF signal associated with the US images, has been developed to perform a microscopic-scale tissue-type imaging offering new solutions for operator-independent examinations. Because materials able to reproduce the harmonic behavior of human liver can be realized, in this study, tissue-mimicking structures were US imaged and the related RF signals were analyzed using wavelet transform through an in-house-developed algorithm for tissue characterization. The classification performance and reliability of the procedure were evaluated on two different tumor stiffnesses (40 and 130 kPa) and with two different applied compression levels (0 and 3.5 N). Our results demonstrated that spectral components associated with different levels of tissue stiffness within the medium exist and can be mapped onto the original US images independently of the applied compressive forces. This wavelet-based analysis was able to identify different tissue stiffness with satisfactory average sensitivity and specificity: respectively, 72.01% ± 1.70% and 81.28% ± 2.02%.

The clinical significance of osteoporosis liesin the relevant occurrence of fractures. Osteoporosis affectsabout 200 million people in the world and is responsible for8.9 million fractures each year worldwide. Hip fractures area major public health burden, from both social andeconomic point of view, since they represent one of the mostimportant causes of morbidity, disability, decreased qualityof life and mortality for the elderly population. It has beendemonstrated that bone mineral density (BMD)measurements on lumbar spine or proximal femur,standardly evaluated by dual-energy X-ray absorptiometry(DXA) examinations, are the most reliable available tool topredict the general risk of osteoporotic fractures. However,DXA, bearing X-ray related issues, is inadequate forpopulation screening purposes and early diagnosis. In thepresent work, we present a new ultrasound (US)-basedmethod and evaluate its performance for the prediction ofosteoporotic fractures. We enrolled 40 women with recentnon-vertebral osteoporotic fractures (frail subjects) and 44controls without fracture history (non-frail subjects): thissample was used to compare the discriminatory power of thenovel US methodology applied on spine with lumbar DXAby building the corresponding Receiver OperatingCharacteristic (ROC) curves. Obtained results showed thatthe new proposed US parameter (named Fragility Score,F.S.) is suitable for population screening purposes, since itsArea Under the Curve (AUC) was the same of DXAmeasuredBMD (0.77) but it was coupled with a bettersensitivity (83% vs 68%) in identifying patients at high riskof osteoporotic fracture.

Halloysite Nanotubes (HNTs) are nanomaterials composed of double layered aluminosilicate minerals with a predominantly hollow tubular structure in submicron range. HNTs are characterized by a wide range of applications in anticancer therapy, sustained agent delivery, being particularly interesting because of their tunable release rates and fast adsorption rates. However systematic investigations of their acoustic properties are still poorly documented. This paper shows a quantitative assessment of the effectiveness of HNTs as scatterers at conventional ultrasonic frequencies (5.7 -7 MHz) in low range of concentrations (1.5-5 mg/mL). Different samples of HNT (diameter: 40-50 nm; length: 0.5 to 2 microns, empty lumen diameter: 15-20 nm) containing agarose gel were imaged through a commercially available echographic system and acquired data were processed through a dedicated prototypal platform in order to extract the average ultrasonic signal amplitude associated to the considered sample. Relationships have been established among backscatter, HNT concentration and the employed echographic frequency. Our results demonstrated that improvement in image backscatter could be achieved incrementing HNT concentration, determining a non-linear signal enhancement due to the fact that they are poly-disperse in length. On the other hand the effect of different echographic frequencies used was almost constant at all concentrations, specifically using higher values of echographic frequency allows yielding a signal enhanced of a factor 1.75±0.26. © 2013 IEEE.

Labor progression is routinely assessed through transvaginal digital inspections, meaning that the clinical decisions taken during the most delicate phase of pregnancy are subjective and scarcely supported by technological devices. In response to such inadequacies, we combined intrapartum echographic acquisitions with advanced tracking algorithms in a new method for noninvasive, quantitative, and automatic monitoring of labor. Aim of this work is the preliminary clinical validation and accuracy evaluation of our automatic algorithm in assessing progression angle (PA) and fetal head station (FHS). A cohort of 10 parturients underwent conventional labor management, with additional translabial echographic examinations after each uterine contraction. PA and FHS were evaluated by our automatic algorithm on the acquired images. Additionally, an experienced clinical sonographer, blinded regarding the algorithm results, quantified on the same acquisitions of the two parameters through manual contouring, which were considered as the standard reference in the evaluation of automatic algorithm and routine method accuracies. The automatic algorithm (mean error +/- 2SD) provided a global accuracy of 0.9 +/- 4.0 mm for FHS and 4 degrees +/- 9 degrees for PA, which is far above the diagnostic ability shown by the routine method, and therefore it resulted in a reliable method for earlier identification of abnormal labor patterns in support of clinical decisions.

Halloysite clay Nanotubes (HNTs) are nanomaterials composed of double layered aluminosilicate minerals with a hollow tubular structure in the submicron range. They are characterized by a wide range of applications in anticancer therapy as agent delivery. In this work we aim to investigate the automatic detection features of HNTs through advanced quantitative ultrasound imaging employing different concentrations (3-5 mg/mL) at clinical conventional frequency, i.e. 7 MHz. Different tissue mimicking samples of HNT containing agarose gel were imaged through a commercially available echographic system, that was opportunely combined with ultrasound signal analysis research platform for extracting the raw ultrasound radiofrequency (RF) signals. Acquired data were stored and analyzed by means of an in-house developed algorithm based on wavelet decomposition, in order to identify the specific spectrum contribution of the HNTs and generate corresponding image mapping. Sensitivity and specificity of the HNT detection were quantified. Average specificity (94.36%) was very high with reduced dependency on HNT concentration, while sensitivity showed a proportional increase with concentration with an average of 46.78%. However, automatic detection performances are currently under investigation for further improvement taking into account image enhancement and biocompatibility issues.

Quantitative ultrasound (QUS) methods forosteoporosis diagnosis potentially provide information aboutthe bone quality and its elastic properties. In this context, anovel ultrasound-based method for spinal and femoraldensitometry was developed by our research group. In orderto maximize its accuracy, it is very important to properlydetect the bone interfaces that will be analyzed as regions ofinterest (ROIs). A fully automatic segmentation algorithmwas developed to select lumbar vertebral interfaces inechographic images and its actual accuracy was assessed inthe present work by means of a visual checking carried outby an expert operator. Abdominal US scans of lumbar spine(from L1 to L4) were performed on 100 female subjects(60.5±3.0 years old) with different ranges of body massindex (BMI) (25.8±4.6 kg/m2). During each US scan, 100frames of radiofrequency (RF) data were stored on a PChard disk for offline analysis. The operator scanned eachvertebra, moving the probe to the next vertebra after 20seconds. For each acquired RF data frame, the implementedalgorithm generated a sectorial echographic image and, if avertebral interface was detected, it was highlighted on thesaved image. The validation procedure was performed by anexpert operator previously trained to detect the "optimal"vertebral interfaces for osteoporosis diagnosis. Resultsshowed that the segmentation algorithm had a highspecificity (93.4%), which reached its maximum on subjectswith BMI < 25 kg/m2 (94.2%), thus avoiding the selectionof false vertebral interfaces and allowing a good accuracy ofosteoporosis diagnosis.

Aim of this study was to perform a detailed clinical validation of a novel fully automatic method for vertebralmorphometry. About 80 spine lateral radiographs were evaluated both automatically, by the proposed algorithm, andmanually, by an experienced radiologist. The following metrics were used for algorithm performance assessment:sensitivity and specificity in vertebra detection; errors in the localisation of characteristic points of vertebral border;errors in the measurement of six diagnostic parameters; level of agreement and correlation between manual andautomatic morphometric measurements; overall accuracy of automatic diagnoses with respect to manual ones.Obtained results showed a very good performance in vertebra detection (sensitivity = 89.1% and specificity = 100.0%).Average errors in the localisation of vertebral characteristic points were always smaller than 3 mm (range 0.85-2.79mm),causing relative errors in diagnostic parameter values ranging from -5.01 to +6.10%. Bland-Altman analysis documenteda mean error in automatic measurements of diagnostic ratios of 0.01 ± 0.18 (bias ± 2 SDs), while Pearson's correlationcoefficient resulted r = 0.71 (p < 0.001). Finally, an optimal diagnostic coincidence (92.8%) was found between automaticand manual diagnoses. Therefore, the adopted method has a potential for an effective employment in clinical routinefor reliable diagnosis of vertebral fractures.

Osteoporosis and overweight/obesityconstitute major worldwide public health burdens that areassociated with aging. The gold standard for osteoporosisdiagnosis is currently represented by bone mineral density(BMD) measurement through dual-energy X-rayabsorptiometry (DXA). However, DXA cannot be used forearly diagnosis through population mass screenings due toionizing radiation employment. Because of this, generally,only people considered at high risk of fracture (underweightwomen after the menopause) undergo to osteoporosisscreening. In fact, a significant risk factor for fracture is thelow body mass index (BMI), while the tendency tooverweight or obesity delays osteoporosis onset.Nevertheless, a high proportion of women after themenopause develop intra-abdominal adiposity, which leadsto metabolic disorders and osteoporosis. This paperdescribes the diagnostic accuracy of a novel ultrasound(US)-based method to perform spinal densitometry. Theproposed innovative methodology is based on a combinedanalysis of both echographic images and "raw"radiofrequency US signals. The diagnostic output isrepresented by the same parameters provided by DXA(BMD, T-score, Z-score). The efficiency of the proposedmethodology was evaluated on a cohort of 280 overweightor obese (BMI > 25 kg/m2) female patients in the age range45-65 years. For 81.4% of the patients, US diagnosis(osteoporotic, osteopenic, healthy) was the same of thecorresponding DXA one, showing the high accuracy of theproposed US technique, especially in the youngest patients(86.4% of correct diagnoses in the age range 45-50 y). Agood correlation was also found between the diagnosticparameters provided by both US and DXA methods: allobtained values of Pearson coefficient (r) were within theinterval 0.66-0.76 (p<0.001). Then, this new non-ionizingapproach to spinal bone densitometry has the potential forbeing extremely useful for early osteoporosis diagnosisthrough population mass screenings.

Multimodal contrast agents (CAs) allow theenhancement of medical images acquired through differenttechniques by employing a single contrast injection, withsignificant benefits for diagnostic outcome. The present study isfocused on the characterization of the magnetic behavior of anovel CA class, consisting of silica (Si) nanoparticles (NPs)covered by either superparamagnetic iron oxide (SPIO) NPs orFePt-IO nanocrystals and designed to be detected through bothultrasound and magnetic resonance imaging (MRI). The usemultimodal nanoparticles as negative MRI contrast agents couldopen up new perspectives for the development of novel tools fornanomedicine, combining different non-ionizing techniques fortargeted imaging of specific diseased cells. In this work, wesimulated the MRI signal of a blood vessel in presence of the newbimodal CAs and compared it with the response of thesuperparamagnetic NPs alone. The performed numericalsimulations showed that the magnetic response of the novel nanocomposites,in terms of signal magnitude, was similar to that ofthe conventional superparamagnetic NPs for values of echo time(TE) shorter than 0.4 ms, while for longer TE values it was evenbetter, showing a stronger vessel enhancement leading to aneasier detection of the smaller vessels. Therefore, the testedbimodal NPs have the potential for an effective employment asMRI CAs.

Currently, osteoporosis is mainly diagnosedthrough dual-energy X-ray absorptiometry (DXA). However,DXA cannot be used for early diagnoses through populationmass screenings because of issues related to ionizingradiation employment. This paper describes the diagnosticaccuracy of a novel ultrasound (US)-based method toperform spinal densitometry without employing X-rays. Theproposed innovative methodology is based on a combinedanalysis of both echographic images and "raw"radiofrequency US signals. The diagnostic output isrepresented by the same parameters of DXA (bone mineraldensity (BMD), T-score, Z-score). The actual effectivenessof the proposed methodology was evaluated on a cohort of350 normal-weight or underweight (body mass index (BMI)< 25 kg/m2) female patients in the age range 45-65 years bya direct comparison with DXA assumed as gold standard.The accuracy of US-based diagnoses ranged from amaximum of 90.5% to a minimum of 74.1%, correspondingto the youngest and oldest patient age category, respectively,with an average of 84.9%. A good correlation was alsofound between US-estimated BMD and DXA related values(r=0.69, p<0.001). Obtained results demonstrated the highaccuracy of the proposed US approach to spinal bonedensitometry compared with DXA. This technique has thepotential to become a useful and effective tool in clinicalpractice improving the current approach to osteoporosisdiagnosis.

Purpose: To evaluate the diagnostic performance of gold nanorod (GNR)-enhanced optoacoustic imaging employing a conventional echographic device and to determine the most effective operative configuration in order to assure optoacoustic effectiveness, nanoparticle stability, and imaging procedure safety.Methods: The most suitable laser parameters were experimentally determined in order to assure nanoparticle stability during the optoacoustic imaging procedures. The selected configuration was then applied to a novel tissue-mimicking phantom, in which GNR solutions covering a wide range of low concentrations (25-200 pM) and different sample volumes (50-200 ?L) were exposed to pulsed laser irradiation. GNR-emitted optoacoustic signals were acquired either by a couple of single-element ultrasound probes or by an echographic transducer. Off-line analysis included: (a) quantitative evaluation of the relationships between GNR concentration, sample volume, phantom geometry, and amplitude of optoacoustic signals propagating along different directions; (b) echographic detection of "optoacoustic spots," analyzing their intensity, spatial distribution, and clinical exploitability. MTT measurements performed on two different cell lines were also used to quantify biocompatibility of the synthesized GNRs in the adopted doses.Results: Laser irradiation at 30 mJ/cm2 for 20 seconds resulted in the best compromise among the requirements of effectiveness, safety, and nanoparticle stability. Amplitude of GNR-emitted optoacoustic pulses was proportional to both sample volume and concentration along each considered propagation direction for all the tested boundary conditions, providing an experimental confirmation of isotropic optoacoustic emission. Average intensity of echographically detected spots showed similar behavior, emphasizing the presence of an "ideal" GNR concentration (100 pM) that optimized optoacoustic effectiveness. The tested GNRs also exhibited high biocompatibility over the entire considered concentration range.Conclusion: An optimal configuration for GNR-enhanced optoacoustic imaging was experimentally determined, demonstrating in particular its feasibility with a conventional echographic device. The proposed approach can be easily extended to quantitative performance evaluation of different contrast agents for optoacoustic imaging.

Successful employment of multimodal molecular imaging for cancer targeting entails the development of safe nanoparticle contrast agents (NPCAs), detects at least by two nonionizing imaging techniques. This paper presents a quantitative assessment of the effectiveness of both pure silica nanospheres (SiNSs) and composite silica/superparamagnetic NPCAs as scatterers for low-frequency diagnostic ultrasound (US) (3 MHz) in very low range of concentrations (1.5-5 mg/mL). Iron oxide (IO) and FePt-IO nanocrystals are employed for SiNS magnetic coating. Different samples of NPCA-containing agarose gel are US imaged through a commercially available system and acquired data are processed through a dedicated prototypal platform to extract image backscatter information and perform evaluation of the image gray level. The pure silica NPCAs confirms recent reports for higher concentrations at higher frequencies. The FePt-IO- coated NPCAs show similar behavior, although with lower values of image backscatter, with a marked effectiveness peak for 330-nm SiNSs, particularly useful for tumor targeting purposes. Finally, the IO-coated SiNSs presented a marked lowering of US enhancement potential and a peak efficiency for a particle diameter of 660 nm. The extent of US backscatter reduction is found to be a function of the number of magnetic nanoparticles per mL of NPCA-containing gel and decreased with increasing NPCA concentrations. These results broadened our knowledge of dual-mode molecular imaging of deep tumors, employing US, and magnetic resonance techniques for the accurate, safe and early detection of cancer cells located in internal organs.

Nanosized particles are receiving increasingattention as future contrast agents (CAs) forultrasound (US) molecular imaging, possibly decoratedon its surface with biological recognition agentsfor targeted delivery and deposition of therapeutics. Inparticular, silica nanospheres (SiNSs) have beendemonstrated to be feasible in terms of contrastenhancement on conventional US systems. In thiswork, we evaluated the cytotoxicity of SiNSs on breastcancer (MCF-7) and HeLa (cervical cancer) cellsemploying NSs with sizes ranging from 160 to 330 nmand concentration range of 1.5-5 mg/mL. Cell viabilitywas evaluated in terms of size, dose and timedependence, performing the MTT reduction assaywith coated and uncoated SiNSs. Whereas uncoatedSiNSs caused a variable significant decrease in cellviability on both cell lines mainly depending on sizeand exposure time, PEGylated SiNSs (SiNSs-PEG)exhibit a high level of biocompatibility. In fact, after72-h incubation, viability of both cell types was abovethe cutoff value of 70 % at concentration up to 5 mg/mL. We also investigated the acoustical behavior ofcoated and uncoated SiNSs within conventionaldiagnostic US fields in order to determine a suitableconfiguration, in terms of particle size and concentration,for their employment as targetable CAs. Ourresults indicate that the employment of SiNSs withdiameters around 240 nm assures the most effectivecontrast enhancement even at the lowest testedconcentration, coupled with the possibility of targetingall tumor tissues, being the SiNSs still in a size rangewhere reticuloendothelial system trapping effect isrelatively low.

An adaptive initialization method was developed to produce fully automatic processing frameworks based on graph-cut and gradient flow active contour algorithms. This method was applied to abdominal Computed Tomography (CT) images for segmentation of liver tissue and hepatic tumours. 25 anonymized datasets were randomly collected from several radiology centres without specific request on acquisition parameter settings nor patient clinical situation as inclusion criteria. Resulting automatic segmentations of liver tissue and tumours were compared to their reference standard delineations manually performed by a specialist. Segmentation accuracy has been assessed through the following evaluation framework: dice similarity coefficient (DSC), false negative ratio (FNR), false positive ratio (FPR) and processing time. Regarding liver surfaces, graph-cuts achieved a DSC of 95.49% (FPR=2.35% and FNR=5.10%), while active contours reached a DSC of 96.17% (FPR=3.35% and FNR=3.87%). The analyzed datasets presented 52 tumours: graph-cut algorithm detected 48 tumours with a DSC of 88.65%, while active contour algorithm detected only 44 tumours with a DSC of 87.10%. In addition, in terms of time performances, less time was requested for graph-cut algorithm with respect to active contour one. The implemented initialization method allows fully automatic segmentation leading to superior overall performances of graph-cut algorithm in terms of accuracy and processing time. The initialisation method here presented resulted suitable and reliable for two different segmentation techniques and could be further extended.

Aim of the present work was to evaluate the performance of a novel fully automatic algorithm for 3D segmentation and volumetric reconstruction of liver vessel network from contrast-enhanced computed tomography (CECT) datasets acquired during routine clinical activity. Three anonymized CECT datasets were randomly collected and were automatically analyzed by the new vessel segmentation algorithm, whose parameter configuration had been previously optimized on a phantom model. The same datasets were also manually segmented by an experienced operator that was blind with respect to algorithm outcome. Automatic segmentation accuracy was quantitatively assessed for both single 2D slices and 3D reconstruction of the vessel network, accounting manual segmentation results as the reference "ground truth". Adopted evaluation framework included the following two groups of calculations: 1) for 3D vessel network, sensitivity in vessel detection was quantified as a function of both vessel diameter and vessel order; 2) for vessel images on 2D slices, dice similarity coefficient (DSC), false positive ratio (FPR), false negative ratio (FNR), Bland-Altman plots and Pearson correlation coefficients were used to judge the correctness of single pixel classifications. Automatic segmentation resulted in a 3D vessel detection sensitivity of 100% for vessels larger than 1 mm in diameter, 64.6% for vessels in the range 0.5-1.0 mm and 27.8% for smaller vessels. An average area overlap of 99.1% was obtained between automatically and manually segmented vessel sections, with an average difference of 0.53 mm(2). The corresponding average values of FPR and FNR were 1.8% and 1.6%, respectively. Therefore, the tested method showed significant robustness and accuracy in automatic extraction of the liver vessel tree from CECT datasets. Although further verification studies on larger patient populations are required, the described algorithm has an exciting potential for supporting liver surgery planning and intraoperative resection guidance.

Photoacoustic (PA) imaging is based on the detection of ultrasound signals emitted by physiological targets that underwent a pulsed laser irradiation. Gold nanoparticles are being currently studied by several research groups as potential molecular contrast agents for PA imaging. Aim of this paper was to test whether a highly biocompatible PEG (polyethylene glycol) coating can improve the stability of gold nanorods (GNRs) under laser irradiation and their effectiveness as contrast agents for PA imaging with respect to uncoated GNRs. Uncoated GNRs and PEG-coated GNRs were synthesized with the same size (48x7 nm) and very similar absorption spectra (main peak at 1055 nm). GNR stability was evaluated as a function of both laser fluence (range 40-100 mJ/cm2) and exposure duration (30-60 s), monitoring optical and morphological GNR changes. PAeffectiveness was then tested using a custom-designed phantom which allowed laser irradiation of GNR solutions of variable concentration contained in a tissue-mimicking hydrogel and acquisition of the corresponding PA signals through a clinically-available ultrasound device. Obtained results showed that absorption spectrum of uncoated GNRs was significantly deteriorated after laser exposure already in the mildest adopted conditions (30-s exposure to 40-mJ/cm2 laser), while PEG-coated GNRs always resulted much more stable, with negligible peakintensity decrements in the mildest irradiation conditions. TEM analysis confirmed the higher morphological stability of PEG-coated GNRs, which also resulted more effective as PA contrast enhancers, since their PA signal intensity was always significantly higher than the corresponding value measured for uncoated GNRs.

The aim of the present work was to demonstrate the possibility of selective detection of nanoparticle contrast agents (NPCAs) on diagnostic echographic images by exploiting the second harmonic component they introduce in the spectra of corresponding ultrasound signals, as a consequence of nonlinear distortion during ultrasound propagation. We employed silica nanospheres (SiNSs) of variable diameter (160 nm, 330 nm, and 660 nm) dispersed in different volume concentrations (range 0.07-0.8%) in agarose gel samples that were automatically scanned through a digital ecograph using narrow-band ultrasound pulses at 6.6 MHz and variable mechanical index (MI range 0.2-0.6). In the first part of the study, the intensity peaks of four different spectral components of the backscattered signal were considered: fundamental (detected in correspondence of the incident ultrasound frequency), subharmonic (detected at half of the fundamental frequency), ultra harmonic (detected at 1.5 times the fundamental frequency), and second harmonic (detected at twice the fundamental frequency). Subsequently, based on the experimental results of the first part of the study and on our recently reported findings, the focus was moved to a detailed comparison between subharmonic and second harmonic trend, which were determined as a function of nanoparticle composition, sample concentration, and MI. The experiments were also repeated on different agarose samples, containing SiNSs covered by an outer shell of smaller magnetic nanoparticles, made of either iron oxide (IO) or FePt-IO nanocrystals. Obtained results show that this new ultrasound-based method for NPCA imaging has a detection sensitivity similar to that of our previously introduced subharmonic-based technique in the presence of 330-nm SiNSs, but performs significantly better in the detection of both the types of "dual mode" NPCAs. The fact that the reported detection method was optimized for identification of 330-nm SiNSs (a sort of "ideal" size for the development of novel tumor-targeting NPCAs) and that the magnetically coated particles are detectable also through magnetic resonance imaging makes the presented second harmonic ultrasound method a valuable solution for the introduction of new protocols for multimodal molecular diagnoses employing only nonionizing radiations.

The aim of this study is to assess the accuracy of a novel ultrasound (US) approach for lumbar spine densitometry on overweight and obese women of variable age through a clinical validation study. The US method was originally developed in women with body mass index (BMI) < 25 kg/m2. In this study, 382 female patients were recruited (45-80 years, BMI > 25 kg/m2) and underwent dual X-ray absorptiometry (DXA) of lumbar spine (L1-L4) and an US scan of the same vertebrae L1-L4, performed with a dedicated device providing both echographic images and 'raw' radiofrequency signals. Acquired US data were analysed through a novel automatic algorithm that performed a series of spectral and statistical analyses to calculate bone mineral density employing an innovative method. Diagnostic accuracy of US investigations was quantitatively assessed through a direct comparison with DXA results. The average agreement between US and DXA diagnoses was acceptable for patients aged 45-65 years (81.5%), while a slight decrement was observed for older patients (69.6%), which can be partially due to a decrease in DXA accuracy because of age-related degenerations. The adopted method has a potential for early osteoporosis diagnosis in people younger than 65 years, independent of their BMI.

The aim of the present work is to assess the effects of different laser fluence and exposure time values on the signal enhancement obtained using of Gold Nanorods (AuNRs) as contrast agent for optoacoustic imaging. In fact, until now, extremely few relevant studies have assessed the optoacoustic behavior of AuNRs under repeatable experimental conditions. A dedicated experimental set-up was developed in order to quantify the contribution of independent parameters to the optoacoustic signal (OAS) produced by 100-mu l solution of AuNR at different concentrations (50, 100 and 200 pM), deposited in a custom-designed tissue-mimicking phantom and irradiated by an appropriate Near Infrared (NIR) light source at variable working conditions in order to generate plasmonic resonance in the AuNRs. Analysis of the OAS recorded by a single-channel ultrasound (US) probe allowed the identification of the optimal and maximum duration of laser exposure, determined through a quantitative analysis of the progressive degradation of the signal emitted by AuNRs under irradiation and at different laser fluence levels. Similarly the effect of rising AuNR concentrations on OAS characteristics was verified, finding a direct proportionality between signal amplitude and AuNR concentration. We found the optimal and maximum laser exposure duration, in order to preserve the AuNR optoacoustic efficiency, were respectively equal to 20 s and 60 s for laser fluence up to 50 mJ/cm(2). Furthermore, the OAS generated upon laser irradiation of AuNRs was found directly proportional to the concentration employed and the optimal concentration of 200 pM was identified.

Halloysite nanotubes (HNTs) are nanomaterials composed of double layered aluminosilicate minerals characterized by a wide range of medical applications. Nonetheless, systematic investigations of their imaging potential are still poorly documented. This paper shows a parametric assessment of the effectiveness of HNTs as scatterers for safe ultrasound (US)-based molecular imaging. Quantitative evaluation of average signal enhancement produced by HNTs with varying set up configuration was performed. The influence of different levels of power (20%, 50%, and 80%) of the signal emitted by clinical equipment was determined, to assess the efficacy of different HNT concentrations (1.5, 3, and 5 mg/mL) at conventional ultrasonic frequencies (5.7-7 MHz), even in case of specific limitation regarding US mechanical interaction with target tissues. Different samples of HNT containing agarose gel were imaged through a commercially available echographic system and acquired data were processed through a dedicated prototypal platform to extract the average ultrasonic signal amplitude. The rate of signal enhancement achieved by different concentration values was quantified and the contribution of frequency increment was separately evaluated. Despite influencing the level of mechanical excitation on HNTs and tissues, our results demonstrated how increasing the power of the emitted signal negatively affected the measured backscatter. Conversely, noticeable improvements in signal backscatter could be achieved incrementing HNT concentration and the echographic frequency employed; specifically the signal enhancement over the used concentration range could be improved by averagely 20%, corresponding to 4.86 ± 0.80 (a.u.), when employing the higher value of echographic frequency. © 2013 IEEE.

Early and accurate diagnosis of tumors requires the combined adoption of different imaging modalities with molecular sensitivity. A successful employment of multimodal molecular imaging is related to the development of smart fully-biodegradable nanoparticle contrast agents (NPCAs), detectable by at least two non-ionizing imaging techniques and suitably sized for tumor targeting. After a short overview of recent findings obtained by our research group in the development and characterization of novel NPCAs, this paper shows for the first time a quantitative assessment of the effectiveness of both a pure silica NPCA and a composite silica/superparamagnetic NPCA as scatterers of low-frequency diagnostic ultrasound (3 MHz) in very low volume concentrations (0.1-0.2%). The pure silica NPCA confirmed the behavior recently reported for higher concentrations at higher frequencies. The composite NPCA followed the same behavior, showing a marked effectiveness peak for a particle diameter of 330 nm, which represents a particularly useful size for tumor targeting purposes. These results open new exciting perspectives for dual-mode molecular imaging of deep tumors, combining ultrasound and magnetic resonance techniques for the accurate, safe and early detection of cancer cells located in internal organs.

The knowledge of ultrasound contrast agent (UCA) behaviour is continuously improving, mainly thanks to "invitro" measurements performed by means of specific phantoms, mimicking the acoustic properties of severalhuman body districts. For such purposes, it is necessary to develop experimental setups able to minimisechemical and physical effects due to environmental conditions. In this paper we discuss the design of a newtissue-mimicking phantom, specifically evaluating the sound-absorption properties of three synthetic materials(Polyurethane, Airex©, ethylene vinyl acetate (EVA©)) laid on the bottom of the phantom. Our goal is toestablish the best material to use in order to minimise the artefacts within the tissue-mimicking matrix.Polyurethane showed the best sound-absorbent behaviour for every tested ultrasound frequency, so itsemployment in covering the bottom of tissue-mimicking phantoms is suggested in order to allow experimentalinvestigations of acoustic properties of different UCAs without additional aspects due to environmentalboundary conditions.

Nowadays the decision between Caesarean Sections (CS), natural or operative child delivery is taken upon interpretation of manually measured anatomical parameters and recorded fetal heart rate, exposing the clinical staff and patients to human errors and determining the continuously rising rate of CS above the ideal 15% recommended by the World Health Organization. This study introduces a new method for non-invasive, quantitative and automatic monitoring of childbirth labor progression. We combined an ultrasound system with a real-time tracking algorithm in order to automatically measure labor progression parameters, like head station, head position, progression angle, based on patient specific anatomical references [Patent no. PCT/EP2009/008321]. A 2D digital echograph connected to a PC for real-time image processing was employed to measure fetal head station (FHS) and progression angle (PA). A quantitative validation study was carried out on a birth simulator, consisting of fetal and maternal mannequins immersed in water. Then, a preliminary intrapartum B-mode imaging study was conducted on patients by means of the developed methods and corresponding algorithms. In the birth simulator, the automatic identification was correct in 98% of the computed images providing high visual reliability for the operator. The average errors (expressed as bias +/- SD) were 0.8 +/- 1.9 mm for FHS and 3 degrees +/- 4 degrees for the PA. Accuracies improve of about 30% by reducing the frame-rate to be processed, i.e. from 1 fps to 0.2 fps, which is still suitable for the purpose. The methodology has been successfully validated in preliminary intrapartum echographic monitoring.

Effective prevention and management of osteoporosis would require suitable methods for population screenings and early diagnosis. Current clinically-available diagnostic methods are mainly based on the use of either X-rays or ultrasound (US). All X-ray based methods provide a measure of bone mineral density (BMD), but it has been demonstrated that other structural aspects of the bone are important in determining fracture risk, such as mechanical features and elastic properties, which cannot be assessed using densitometric techniques. Among the most commonly used techniques, dual X-ray absorptiometry (DXA) is considered the current "gold standard" for osteoporosis diagnosis and fracture risk prediction. Unfortunately, as other X-ray based techniques, DXA has specific limitations (e.g., use of ionizing radiation, large size of the equipment, high costs, limited availability) that hinder its application for population screenings and primary care diagnosis. This has resulted in an increasing interest in developing reliable pre-screening tools for osteoporosis such as quantitative ultrasound (QUS) scanners, which do not involve ionizing radiation exposure and represent a cheaper solution exploiting portable and widely available devices. Furthermore, the usefulness of QUS techniques in fracture risk prediction has been proven and, with the last developments, they are also becoming a more and more reliable approach for assessing bone quality. However, the US assessment of osteoporosis is currently used only as a pre-screening tool, requiring a subsequent diagnosis confirmation by means of a DXA evaluation. Here we illustrate the state of art in the early diagnosis of this "silent disease" and show up recent advances for its prevention and improved management through early diagnosis.

Fetal malformations are very frequent in industrialized countries. Although advanced maternal age may affect pregnancy outcome adversely, 80%-90% of fetal malformations occur in the absence of a specific risk factor for parents. The only effective approach for prenatal screening is currently represented by an ultrasound scan. However, ultrasound methods present two important limitations: the substantial absence of quantitative parameters and the dependence on the sonographer experience. In recent years, together with the improvement in transducer technology, quantitative and objective sonographic markers highly predictive of fetal malformations have been developed. These markers can be detected at early gestation (11-14 wk) and generally are not pathological in themselves but have an increased incidence in abnormal fetuses. Thus, prenatal ultrasonography during the second trimester of gestation provides a "genetic sonogram", including, for instance, nuchal translucency, short humeral length, echogenic bowel, echogenic intracardiac focus and choroid plexus cyst, that is used to identify morphological features of fetal Down's syndrome with a potential sensitivity of more than 90%. Other specific and sensitive markers can be seen in the case of cardiac defects and skeletal anomalies. In the future, sonographic markers could limit even more the use of invasive and dangerous techniques of prenatal diagnosis (amniocentesis, etc.).

Aim of the present work was, first, to demonstrate feasibility and usefulness of subharmonic imaging of silica nanospheres (SiNSs) at diagnostic ultrasound (US) frequencies and, second, to investigate the acoustic effectiveness of a new class of multimodal nanocomposite contrast agents, towards dual mode investigations combining US and magnetic resonance imaging (MRI). We employed SiNSs of variable diameter (160 nm, 330 nm and 660 nm) dispersed in different volume concentrations (range 0.07-0.8%) in agarose gel samples that were automatically scanned through a digital ecograph using narrow-band US pulses, varying both frequency (range 5-10 MHz) and mechanical index (MI range 0.2-0.6). Raw radiofrequency data were acquired and off-line processed, in order to study the behaviour of fundamental and subharmonic component as a function of incident frequency, MI, SiNS size and concentration. The experiments were also repeated on different agarose samples, containing SiNSs covered by an outer shell of smaller magnetic nanoparticles, made of either iron oxide (FeO) or FePt-FeO nanocrystals. Obtained results show that the highest sensitivity of subharmonic intensity to nanoparticle presence was always found for 330-nm SiNSs, that can be effectively detected at very low volume concentrations (0.07%) by employing a low MI (0.2). These properties were maintained by SiNSs even after a coverage by an outer magnetic shell, so representing a valuable candidate for tasks of dual mode molecular imaging.

Aim of this work was to investigate the effect ofultrasound incident frequency on the echographic contrastenhancement power of an experimental drug delivery agent,halloysite clay nanotubes (HNTs), and to determine a suitableconfiguration in terms of both insonification frequency andparticle concentration for an effective employment as targetedcontrast agent. Various HNT concentrations (range 0.25-3.00mg/mL) were dispersed in custom-designed tissue-mimickingphantoms and exposed to different ultrasound frequencies (7-11MHz) through a conventional clinically-available echographicdevice. Off-line analysis included the evaluation of bothamplitude of backscattered ultrasound signals and imagebrightness. Amplitude of HNT-backscattered signals showed alinear increase with particle concentration, while imagebrightness enhancement was limited by logarithmic compressioneffects. On the other hand, backscatter amplitude showedsignificant increments with increasing ultrasound frequency upto 10 MHz, then showing a concentration-dependent behaviorwithout further enhancements. Overall, the most effectiveresponse was found when a 10-MHz ultrasound frequency wasemployed to insonify HNTs at a concentration of 1.5 mg/mL. Inconclusion, the present study optimized the combination ofincident ultrasound frequency and HNT concentration, in orderto obtain an echographic image enhancement suitable for medicalapplications. Future dedicated studies will assess the feasibility ofautomatic detection of HNTs within echographic images andtheir possible employment as theranostic agents.

Aim of this study was to perform a detailed clinical validation of a new fully automatic algorithm for vertebral interface segmentation in echographic images. Abdominal echographic scans of lumbar vertebrae L1-L4 were carried out on 150 female subjects with variable age and body mass index (BMI). Acquired datasets were automatically processed by the algorithm and the accuracy of the obtained segmentations was then evaluated by three independent experienced operators. Obtained results showed a very good specificity in vertebra detection (93.3%), coupled with a reasonable sensitivity (68.1%), representing a suitable compromise between the detection of a sufficient number of vertebrae for reliable diagnoses and the limitation of the corresponding computation time. Importantly, there was only a minimum presence of 'false vertebrae' detected (2.8%), resulting in a very low influence on subsequent diagnostic analyses. Furthermore, the algorithm was specifically tuned to provide an improved sensitivity (up to 73.1%) with increasing patient BMI, to keep a suitable number of correctly detected vertebrae even when the acquisition was intrinsically more difficult because of the augmented thickness of abdominal soft tissues. The proposed algorithm will represent an essential added value for developing echographic methods for the diagnosis of osteoporosis on lumbar vertebrae.

An apparatus (10) for measuring one or more labor progress parameters (25) as the dilation of the endocervical canal (8), the rotation and the position of the head (4) of the foetus (3) during the descent, the duration and the intensity of the uterine contractions, other morphological and physiological parameters, without introducing foreign objects into the body of a pregnant woman (2) and independently from the sensitivity of the operator. The apparatus (10) comprises automatic means for tracking, in a sequence of ultrasound images (11,12) that are obtained by an ultrasound probe (1), one or more regions of interest (ROI, 21), that may be both two-dimensional or three-dimensional and are centred about anatomic reference points (28) that define said parameters selected in a reference image by a displaying unit (14). The tracking means comprises: a) a means for calculating a function (f) at the pixels of the ROI of the reference image and of images preferably sampled among the images of the sequence, b) a means for calculating iteratively at the positions of the ROI in subsequent images, by a means of comparison between the values of the function (f) calculated in the pixels of the ROI of a current image and the values of the function (f) calculated in the pixels of the ROI of a subsequent ultrasound image; c) a means for comparing each position of the ROI with the position of the ROI in the reference image and for calculating the labor progress parameter responsive to said comparison. The new position of the region of interest may be defined as a domain in which a predetermined object function assumes a minimum value.