A Novel Ultrasound Robot with Force/torque Measurement and Control for Safe and Efficient Scanning.

Medical ultrasound is of increasing importance in medical diagnosis and intraoperative assistance and possesses great potential advantages when integrated with robotics. However, some concerns, including the operation efficiency, operation safety, image quality, and comfort of patients, remain after introducing robotics into medical ultrasound. In this paper, an ultrasound robot integrating a force control mechanism, force/torque measurement mechanism, and online adjustment method, is proposed to overcome the current limitations. The ultrasound robot can measure operating forces and torques, provide adjustable constant operating forces, eliminate great operating forces introduced by accidental operations, and achieve various scanning depths based on clinical requirements. The proposed ultrasound robot would potentially facilitate sonographers to find the targets quickly, improve operation safety and efficiency, and decrease patients' discomfort. Simulations and experiments were carried out to evaluate the performance of the ultrasound robot. Experimental results show that the proposed ultrasound robot is able to detect operating force in the z-direction and torques around the x- and y- directions with errors of 3.53% F.S., 6.68% F.S., and 6.11% F.S., respectively, maintain the constant operating force with errors of less than 0.57N, and achieve various scanning depths for target searching and imaging. This proposed ultrasound robot has good performance and would potentially be used in medical ultrasound.

SAPM: Self-Adaptive Parallel Manipulator with Pose and Force Adjustment for Robotic Ultrasonography.

Robotic ultrasonography potentially acts as an essential aid to medical diagnosis. To overcome the limitations in robotic ultrasonography, in this paper, we proposed a novel self-adaptive parallel manipulator (SAPM) that can automatically adjust the ultrasound (US) probe pose to adapt to various contours of scanned areas, provide approximate constant operating forces/torques, achieve mechanical measurement, and cushion undesired produced forces. A novel parallel adjustment mechanism is proposed to attain automatic pose adjustment with 3 degrees of freedom (DOFs). This mechanism enables the US probe to adapt to different scanned areas and to perform the scanning with approximate constant forces and torques. Besides, we present a mechanical measurement and safety protection method that can be integrated into the SAPM and used as operation status monitoring and early warning during scanning procedures by capturing operating forces and torques. Experiments were carried out to calibrate the measurement and buffer units and evaluate the performance of the SAPM. Experimental results show the ability of the SAPM to provide 3-DoFs motion and operating force/torque measurement and automatically adjust the US probe pose to capture US images of equally good quality compared to a manual sonographer scan. Moreover, it has characteristics similar to soft robots that could significantly improve operation safety, and could be extended to some other engineering or medical applications.

Identification of a six-gene prognostic signature for oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC) is one of the most common types of malignancies worldwide, and its morbidity and mortality have increased in the near term. Consequently, the purpose of the present study was to identify the notable differentially expressed genes (DEGs) involved in their pathogenesis to obtain new biomarkers or potential therapeutic targets for OSCC. The gene expression profiles of the microarray datasets GSE85195, GSE23558, and GSE10121 were obtained from the Gene Expression Omnibus (GEO) database. After screening the DEGs in each GEO dataset, 249 DEGs in OSCC tissues were obtained. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology pathway enrichment analysis was employed to explore the biological functions and pathways of the above DEGs. A protein-protein interaction network was constructed to obtain a central gene. The corresponding total survival information was analyzed in patients with oral cancer from The Cancer Genome Atlas (TCGA). A total of six candidate genes (CXCL10, OAS2, IFIT1, CCL5, LRRK2, and PLAUR) closely related to the survival rate of patients with oral cancer were identified, and expression verification and overall survival analysis of six genes were performed based on TCGA database. Time-dependent receiver operating characteristic curve analysis yields predictive accuracy of the patient's overall survival. At the same time, the six genes were further verified by quantitative real-time polymerase chain reaction using samples obtained from the patients recruited to the present study. In conclusion, the present study identified the prognostic signature of six genes in OSCC for the first time via comprehensive bioinformatics analysis, which could become potential prognostic markers for OCSS and may provide potential therapeutic targets for tumors.

Development and preliminary testing of a prior knowledge-based visual navigation system for cardiac ultrasound scanning.

Purpose: Ultrasound is widely used to diagnose disease and guide surgery because it is versatile, inexpensive and radiation-free. However, image acquisition is dependent on the operation of a professional sonographer, which is a difficult skill to learn for a wider range of non-sonographers. Methods: We propose a prior knowledge-based visual navigation method to obtain three important standard ultrasound views of the heart, based on the sonographer's skill learning and augmented reality prompts. The key information about the probe movement was captured using vision-based tracking and normalisation methods on 14 volunteers, based on a professional sonographer's practice. An augmented reality-based navigation method was then proposed to guide operators with no ultrasound experience to find standard views of the heart in a second set of three volunteers. Results: Through quantitative analysis and qualitative scoring, the results showed that the proposed method can effectively guide non-sonographers to obtain standard views with diagnostic value. Conclusion: It is believed that the method proposed in this paper has clear application value in primary care, and expansion of the data will allow the accuracy of the navigation to be further improved.

Bibliometric analysis of lupus nephritis in children from 1999 to 2022: A review.

Lupus nephritis (LN) is a complication of systemic lupus erythematosus and a damaging disease of the kidney. The injury of LN in children is more serious than that in adults. However, the literature in this field is numerous and complex, which brings great challenges for researchers to extract information. The purpose of this study is to carry out bibliometric analysis and visualization of published literatures, and identify current research hotspots and future research trends in this field. Literature was retrieved from the Web Of Science database from 1999 to 2022. The literature was analyzed and visualized using Citespace 6.1.R6, VOSviewer 1.6.18, and Microsoft Excel 2019. A total of 1059 articles were included in this study. In the past 13 years, an increase in the number of publications every year. Brunner HI is the author with the highest number of published and cited papers in this field, followed by Wenderfer SE. The United States and China are the countries with the highest number of published papers. University Toronto is the most productive institution, followed by University Cincinnati. The most prolific journal was Pediatric nephrology (IF 2.67), followed by lupus (IF 2.21). Lupus was cited the most, followed by Pediatric nephrology. The keyword burst showed the earliest and longest burst was antiphospholipid antibody, validation/risk/rituximab/safety is the current research hotspot. The article with the highest number of citations was Hochberg MC 1997 published in Arthritis Rheum. This study provides valuable information summary for the field of LN in children, which is helpful to strengthen the cooperation among countries, institutions and authors, and promote the research in the field of LN in children.

Repair of buccal mucosa and floor of mouth defects using keystone design perforator island flap.

OBJECTIVE: To assess the feasibility of utilizing the keystone design perforator island flap (KDPIF) for the repair of small to medium-sized defects in the buccal mucosa and floor of mouth (cT1-2 stage tumor). STUDY DESIGN: We conducted a retrospective analysis of eight patients who underwent KDPIF to address oral defects at the Affiliated Hospital of Qingdao University between June 2021 and September 2022. Patient information, including medical history, defect site, flap size, operative time, hospital stay, complications, and postoperative recovery of oral function, was comprehensively evaluated. RESULTS: Eight patients (6 females and 2 males) underwent reconstruction using KDPIF. The mean operation time was 58.5 minutes (55-63 minutes), with an average length of stay of 3.5 days (3-5 days). None of the 8 cases (100%) exhibited flap splitting necrosis or infection. Moreover, no scar contracture was observed, and oral functions, including the degree of opening, type of opening, tongue mobility, speech function, and swallowing function, were successfully restored. One patient (12.5%) experienced bleeding from the incision on the first postoperative day, but following compression, hemostasis was achieved, and the incision healed well. CONCLUSIONS: KDPIF demonstrates technical feasibility and suitability for repairing small to medium-sized buccal mucosa and floor of mouth defects (cT1-2).

A preliminary study on the application of bone marrow stromal cell sheet on the formation of functional tissue-engineered bone in dogs.

PURPOSE: The aim of this study was to construct functional tissue-engineered bone in dogs using cell sheet engineering, a new technique to gain and transfer seed cells. MATERIALS AND METHODS: Demineralized bone matrixes, prepared from homologous bone, were coated with recombinant human bone morphogenetic protein-2. Bone marrow stromal cells (BMSCs) were isolated and subcultured. Osteogenic-induced BMSCs were incubated in a temperature-responsive culture dish to form the BMSC sheet. The complex of demineralized bone matrix, recombinant human bone morphogenetic protein-2, and BMSCs wrapped with BMSC sheets was implanted around the blood vessels of the latissimus dorsi muscle in the experimental side, and the same complex without BMSC sheets was implanted around the blood vessels of the latissimus dorsi muscle on the other side as a control. At 4, 8, 12, and 16 weeks after implantation, the implants were removed for radiographic evaluation, descriptive histologic observation, and histologic quantitative analysis. RESULTS: Radiographic analysis showed that the optical density of the tissue-engineered bone on the 2 sides increased with time. However, the optical density of the experimental side was significantly greater than that of the control side at the same points. Sixteen weeks after implantation, mature lamellar bone was formed in the experimental side, with red bone marrow in the bone marrow cavity. In contrast, the control side exhibited significantly less lamellar bone. Histologic quantitative analysis showed that the experimental side exhibited significantly more bone per area compared with the control side. CONCLUSION: BMSC sheet engineering may be useful to construct functional tissue-engineered bone.

Diffuse Large B-cell Lymphoma (Leg Type) Originating in the Skin of the Right Cheek Region: A Case Report and Literature Review.

Primary diffuse cutaneous large B-cell lymphoma, leg type (PCDLBCL-LT), usually affecting one or both lower legs, with a 5-year disease-free survival rate of less than 60%. Solitary facial lesions are extremely rare. Our report is about a 93-year-old woman whose clinical examination revealed a 4 cm × 5 cm × 3 cm mass with a soft texture and smooth margins on the right side of her cheek. Immunohistochemical analyses were consistent with a diagnosis of PCDLBCL-LT. The surgical method for this patient was: extensive resection of the tumor and repair of the defect with an adjacent flap. Neither local recurrence nor systemic invasion was observed during postoperative follow-up (8 months). The clinician must be very careful when making a correct diagnosis based on the clinical and immunohistochemical findings of PCDLBCL-LT. For this type of PCDLBCL-LT isolated in 1 site without invasion of the rest of the body, extensive surgical resection may result in a favorable prognosis.

Using MaxEnt Model to Predict the Potential Distribution of Three Potentially Invasive Scarab Beetles in China.

A hot topic in recent years is the prediction of the potential distribution of possible invasive insects. China is facing a great challenge due to invasive insects. Scarab beetles are a highly diverse group, and many of them are well-known invasive insects. Here, in order to prevent the invasion of scarab beetles in China, we screened the invasive insects globally and obtained a preliminary database of quarantine or invasive scarab beetles. From the obtained database, we selected the top five species (Popillia japonica, Heteronychus arator, Oryctes monoceros, Oryctes boas and Amphimallon majale) to discuss and analyzed the potential distribution of three species that have not invaded China by using the MaxEnt model. The prediction results show that every continent has potential distribution areas for these species. Specifically within China, Popillia japonica and Amphimallon majale were mainly concentrated in east central regions and Heteronychus arator and Oryctes boas were mainly distributed in the southwest areas, while Oryctes monoceros has no suitable area. Notably, Yunnan, Hunan, Jiangxi and Zhejiang province had a high risk of invasion. In general, local agriculture, forestry and customs departments in China should pay more attention to monitoring for the prevention of infestation by invasive insects.

Comprehensive Management of a Giant Venous Malformation of the Lip: Vascular Embolization Followed by Surgical Resection and Reconstruction.

Venous malformations often manifest in early childhood and do not spontaneously resolve. Most vein malformations of the lips are typically treated at a young age, with giant arteriovenous malformations being particularly rare. Herein, we introduce the case of a 47-year-old man who presented to our department complaining of a progressive mass on his lower lip. Clinical examination revealed a mass measuring 10 cm × 8 cm × 4 cm in size, characterized by a soft texture and smooth edges. Despite a series of sclerotherapy interventions, the lesion remained unresponsive. Consequently, we performed a preoperative embolization of the malformed vessel using digital angiography, followed by extensive resection of the lesion and repair of the defect using an adjacent flap. The postoperative period was uneventful, and no local recurrence was observed during a 4-year follow-up period. Therefore, we recommend preoperative angioembolization as a valuable approach for addressing large lower lip deformities to enable extensive surgical resection and robust therapeutic outcomes.

Drainage and Orbitofrontal Reconstruction After Removal of a Giant Frontal Sinus Osteoma: A Case Report.

After removal of a large frontal sinus osteoma in this case, the contralateral nasofrontal canal was opened to drain the intraoperative fluid and prevent infection, and the defect in the orbitofrontal area was restored using a titanium mesh designed with 3D printing technology.

Development of Digital Fetal Heart Models with Virtual Ultrasound Function Based on Cardiovascular Casting and Computed Tomography Scan.

Despite recent breakthroughs in diagnosis and treatment, congenital heart defects (CHDs) continue to be the leading cause of death among newborns. Fetal echocardiography is the most effective and non-invasive method for the prenatal diagnosis of CHDs. However, the challenge of obtaining standard views can lead to a low diagnostic accuracy. To explore new methods for training, the combined use of cardiovascular casting, computed tomography (CT) scanning, and virtual ultrasound generation methods was studied to preserve the cardiac structures of a fetus in digital form. The feasibility of the proposed workflow was verified by testing three fetal heart specimens collected after the termination of pregnancy. As a result, the anatomical structures were imaged clearly by a CT scan after cardiovascular casting, and the virtually generated ultrasound images based on the use of the Public software Library for UltraSound imaging research (PLUS) toolkit successfully demonstrated both the standard views and the views with diagnostic values for the visualization of the cardiovascular structures. This solution provides great data extensibility while being simple and cost-effective for end users. Therefore, the proposed method could provide a promising educational system for trainees to understand standard views of fetal echocardiography and the corresponding anatomical correlations.

Masseter Muscle Metastasis of Renal Cell Carcinoma: A Case Report and Literature Review.

BACKGROUND: Patients with renal cell carcinoma are often troubled by metastases, but masseter muscle metastases are particularly rare. CASE PRESENTATION: We reported a 76-year-old male who did not show any recurrence and metastasis after the nephrectomy until 5 years later. The metastatic mass was found with the protrusion of masseter muscle area. Computed tomography and ultrasonography indicated a hypervascular mass, and pathology confirmed the masseter muscle metastasis of renal cell carcinoma. Complete metastasectomy was performed with the preserval of facial function and appearance. No local recurrence or distant metastasis was found in follow-up. CONCLUSION: Our report indicates masseter muscle can be a metastatic site of renal cell carcinoma, regardless of its rarity. Long-term comprehensive surveillance is needed for patients with renal cell carcinoma. Muscle metastases can disguise as benign mass, while multiple imaging and pathology are important in identifying their sources. If possible, complete metastasectomy with function retention is recommended for masseter muscle metastases.

Design of Novel End-effectors for Robot-assisted Swab Sampling to Combat Respiratory Infectious Diseases.

The COVID-19 outbreak has caused the mortality worldwide and the use of swab sampling is a common way of screening and diagnosis. To combat respiratory infectious diseases and assist sampling, robots have been utilized and shown promising potentials. Nonetheless, a safe, patient-friendly, and low-cost swabbing system would be crucial for the practical implementation of robots in hospitals or inspection stations. In this study, we proposed two recyclable and cost-efficient end-effector designs that can be equipped at the distal end of a robot to passively regulate or actively sense the force exerted onto patients. One way is to introduce passive compliant mechanisms with soft material to increase the flexibility of the swabbing system, while the other way is utilizing a force-sensing gripper with embedded optoelectronic sensors to actively sense the force or torque. The proposed designs were modelled computationally and tested experimentally. It is identified that the passive compliant mechanisms can increase the flexibility of the swabbing system when subjected to the lateral force and mitigate the vertical force resulted from buckling. The lateral force range that the force-sensing gripper can detect is 0-0.35 N and the vertical force range causing buckling effect that can be sensed by gripper is 1.5-2.5 N.

Design of a Low-Cost Miniature Robot to Assist the COVID-19 Nasopharyngeal Swab Sampling.

Nasopharyngeal (NP) swab sampling is an effective approach for the diagnosis of coronavirus disease 2019 (COVID-19). Medical staffs carrying out the task of collecting NP specimens are in close contact with the suspected patient, thereby posing a high risk of cross-infection. We propose a low-cost miniature robot that can be easily assembled and remotely controlled. The system includes an active end-effector, a passive positioning arm, and a detachable swab gripper with integrated force sensing capability. The cost of the materials for building this robot is 55 USD and the total weight of the functional part is 0.23kg. The design of the force sensing swab gripper was justified using Finite Element (FE) modeling and the performances of the robot were validated with a simulation phantom and three pig noses. FE analysis indicated a 0.5mm magnitude displacement of the gripper's sensing beam, which meets the ideal detecting range of the optoelectronic sensor. Studies on both the phantom and the pig nose demonstrated the successful operation of the robot during the collection task. The average forces were found to be 0.35N and 0.68N, respectively. It is concluded that the proposed robot is promising and could be further developed to be used in vivo.

Resequencing and SNP discovery of Amur ide (Leuciscus waleckii) provides insights into local adaptations to extreme environments.

Amur ide (Leuciscus waleckii), a Cyprinid species, is broadly distributed in Northeast Asia. Different from its freshwater counterparts, the population in Lake Dali Nor has a strong alkalinity tolerance and can adapt to extremely alkali-saline water with bicarbonate over 50 mmol/L. To uncover the genetic basis of its alkaline adaptation, three populations, including one alkali form from Lake Dali Nor (DL), one freshwater form from its adjacent sister Lake Ganggeng Nor (GG), and one freshwater form from its historical origin, namely, the Songhua River (SH), were analyzed using genome resequencing technology. A total of 679.82 Gb clean data and 38,091,163 high-quality single-nucleotide polymorphism (SNP) loci were detected in the three populations. Nucleotide diversity and population structure analysis revealed that the DL and GG populations have lower nucleotide diversities and different genetic structures than those of the SH population. Selective sweeping showed 21 genes involved in osmoregulatory regulation (DLG1, VIPR1, AKT1, and GNAI1), inflammation and immune responses (DLG1, BRINP1, CTSL, TRAF6, AKT1, STAT3, GNAI1, SEC22b, and PSME4b), and cardiorespiratory development (TRAF6, PSME4b, STAT3, AKT1, and COL9A1) to be associated with alkaline adaption of the DL population. Interestingly, selective pressure (CodeML, MEME, and FEL) methods identified two functional codon sites of VIPR1 to be under positive selection in the DL population. The subsequent 3D protein modeling confirmed that these selected sites will incur changes in protein structure and function in the DL population. In brief, this study provides molecular evidence of population divergence and alkaline adaptation, which will be very useful for revealing the genetic basis of alkaline adaptation in Amur ide.

Iron deficiency and early childhood caries: a systematic review and meta-analysis.

BACKGROUNDS: Previous surveys have found that children with iron deficiency (ID) were likely to suffer from early childhood caries (ECC). We aimed to assess the scientific evidence about whether ID is intrinsically related to ECC. METHODS: The medical subject headings (MeSH) terms and free words were searched on PubMed, Web of Science, Cochrane, China National Knowledge Infrastructure, Wanfang, and the Database for Chinese Technical Periodicals from March 2020 to September 2020. Two researchers independently screened the articles. Data extraction and cross-checking were performed for the studies that met the inclusion criteria. Meta-analysis was performed using the Cochrane Collaboration's Review Manager 5.3 software. RESULTS: After excluding duplication and irrelevant literature, 12 case-control studies were included in the study. The meta-analysis demonstrated that children with ECC were more likely to have ID (odds ratio [OR] = 2.63, 95% confidence interval [CI]: [1.85, 3.73], P < 0.001). There was no statistically significant association found between the level of serum ferritin and ECC (weighted mean difference (WMD) = -5.80, 95% CI: [-11.97, 0.37], P = 0.07). Children with ECC were more likely to have iron-deficiency anemia (OR = 2.74, 95% CI: [2.41,3.11], P < 0.001). The hemoglobin (HGB) levels in the ECC group were significantly lower compared with that in the ECC-free group (WMD = -9.96, 95% CI: [-15.45, -4.46], P = 0.0004). The mean corpuscular volume (MCV) levels in the ECC group were significantly lower compared with that in the ECC-free group (WMD = -3.72, 95% CI: [-6.65, -0.79], P = 0.01). CONCLUSIONS: ID was more prevalent in children with ECC, and the markers of iron status in the ECC group, such as serum ferritin, HGB, and MCV, were relatively lower than the ECC-free group.

Towards Standardized Acquisition with a Dual-probe Ultrasound Robot for Fetal Imaging.

Standardized acquisitions and diagnoses using robots and AI would potentially increase the general usability and reliability of medical ultrasound. Working towards this prospect, this paper presents the recent developments of a standardized acquisition workflow using a novel dual-probe ultrasound robot, for a project known as intelligent Fetal Imaging and Diagnosis (iFIND). The workflow includes an abdominal surface mapping step to obtain a non-parametric spline surface, a rule-based end-point calculation method to position each individual joint, and a motor synchronization method to achieve a smooth motion towards a target point. The design and implementation of the robot are first presented in this paper and the proposed workflow is then explained in detail with simulation and volunteer experiments performed and analyzed. The closed-form analytical solution to the specific motion planning problem has demonstrated a reliable performance controlling the robot to move towards the expected scanning areas and the calculated proximity of the robot to the surface shows that the robot maintains a safe distance while moving around the abdomen. The volunteer study has successfully demonstrated the reliable working and controllability of the robot in terms of acquiring desired ultrasound views. Our future work will focus on improving the motion planning, and on integrating the proposed standardized acquisition workflow with newly- developed ultrasound image processing methods to obtain diagnostic results in an accurate and consistent way.

Design and Integration of a Parallel, Soft Robotic End-Effector for Extracorporeal Ultrasound.

OBJECTIVE: In this work we address limitations in state-of-the-art ultrasound robots by designing and integrating a novel soft robotic system for ultrasound imaging. It employs the inherent qualities of soft fluidic actuators to establish safe, adaptable interaction between ultrasound probe and patient. METHODS: We acquire clinical data to determine the movement ranges and force levels required in prenatal foetal ultrasound imaging and design the soft robotic end-effector accordingly. We verify its mechanical characteristics, derive and validate a kinetostatic model and demonstrate controllability and imaging capabilities on an ultrasound phantom. RESULTS: The soft robot exhibits the desired stiffness characteristics and is able to reach 100% of the required workspace when no external force is present, and 95% of the workspace when considering its compliance. The model can accurately predict the end-effector pose with a mean error of 1.18±0.29 mm in position and 0.92±0.47° in orientation. The derived controller is, with an average position error of 0.39 mm, able to track a target pose efficiently without and with externally applied loads. Ultrasound images acquired with the system are of equally good quality compared to a manual sonographer scan. CONCLUSION: The system is able to withstand loads commonly applied during foetal ultrasound scans and remains controllable with a motion range similar to manual scanning. SIGNIFICANCE: The proposed soft robot presents a safe, cost-effective solution to offloading sonographers in day-to-day scanning routines. The design and modelling paradigms are greatly generalizable and particularly suitable for designing soft robots for physical interaction tasks.

Development and Testing of an Ultrasound-Compatible Cardiac Phantom for Interventional Procedure Simulation Using Direct Three-Dimensional Printing.

Organ phantoms are widely used for evaluating medical technologies, training clinical practitioners, as well as surgical planning. In the context of cardiovascular disease, a patient-specific cardiac phantom can play an important role for interventional cardiology procedures. However, phantoms with complicated structures are difficult to fabricate by conventional manufacturing methods. The emergence of three-dimensional (3D) printing with soft materials provides the opportunity to produce phantoms with complex geometries and realistic properties. In this work, the aim was to explore the use of a direct 3D printing technique to produce multimodal imaging cardiac phantoms and to test the physical properties of the new materials used, namely the Poro-Lay series and TangoPlus. The cardiac phantoms were first modeled using real data segmented from a patient chest computer tomography (CT) scan and then printed with the novel materials. They were then tested quantitatively in terms of stiffness and ultrasound (US) acoustic values and qualitatively with US, CT, and magnetic resonance imaging systems. From the stiffness measurements, Lay-fomm 40 had the closest Young's modulus to real myocardium with an error of 29-54%, while TangoPlus had the largest difference. From the US acoustics measurements, Lay-fomm 40 also demonstrated the closest soft tissue-mimicking properties with both the smallest attenuation and impedance differences. Furthermore, the imaging results show that the phantoms are compatible with multiple imaging modalities and thus have potential to be used for interventional procedure simulation and testing of novel interventional devices. In conclusion, direct 3D printing with Poro-Lay and TangoPlus is a promising method for manufacture of multimodal imaging phantoms with complicated structures, especially for soft patient-specific phantoms.