US Probe Research Articles

Prospective measurement of the width of cerebrospinal fluid spaces by cranial ultrasound in neurologically healthy children aged 0–19 months

BackgroundUltrasound (US) is often the first method used to look for brain or cerebrospinal fluid (CSF) space pathologies. Knowledge of normal CSF width values is essential. Most of the available US normative values were established over 20 years ago, were obtained with older equipment, and cover only part of the age spectrum that can be examined by cranial US. This prospective study aimed to determine the normative values of the widths of the subarachnoid and internal CSF spaces (craniocortical, minimal and maximal interhemispheric, interventricular, and frontal horn) for high-resolution linear US probes in neurologically healthy infants and children aged 0–19 months and assess whether subdural fluid collections can be delineated.MethodsTwo radiologists measured the width of the CSF spaces with a conventional linear probe and an ultralight hockey-stick probe in neurologically healthy children not referred for cranial or spinal US.ResultsThis study included 359 neurologically healthy children (nboys = 178, 49.6%; ngirls = 181, 50.4%) with a median age of 46.0 days and a range of 1–599 days. We constructed prediction plots, including the 5th, 50th, and 95th percentiles, and an interactive spreadsheet to calculate normative values for individual patients. The measurements of the two probes and the left and right sides did not differ, eliminating the need for separate normative values. No subdural fluid collection was detected.ConclusionNormative values for the widths of the subarachnoid space and the internal CSF spaces are useful for evaluating intracranial pathology, especially when determining whether an increase in the subarachnoid space width is abnormal.

Added value of 3D ultrasound image-guided hepatic interventions by X matrix technology

BackgroundImage-guided hepatic interventions are integral to the management of infective and neoplastic liver lesions. Over the past decades, 2D US was used for guidance of hepatic interventions; with the recent advances in US technology, 3D US was used to guide the hepatic interventions. This study aimed to illustrate the added value of 3D image-guided hepatic interventions by X matrix technology.MethodsThis prospective study was performed on 100 patients that were divided into two groups: group A which included 50 patients who were managed by using 2D US probe guidance, and group B which included 50 patients who were managed by using 3D X matrix US probe guidance. Thermal ablation was done for 70 patients; 40 radiofrequency ablation (RFA) (20 by the 2D probe and 20 by the 3D X matrix probe) and 30 microwave ablation (MWA) (15 by the 2D probe and 15 by the 3D X matrix probe). Chemical ablation (PEI) was done for 20 patients (ten by the 2D probe and ten by the 3D X matrix probe). Drainage of hepatic collections and biopsy from undiagnosed hepatic focal lesions were done for ten patients (five by the 2D probe and five by the 3D X matrix probe).ResultsThe efficacy of US-guided hepatic interventions by 3D X matrix probe was higher than the 2D probe but not significantly higher, with a p value of 0.705, 0.5428 for RFA and MWA, respectively, 0.5312 for PEI, and 0.2918 for drainage of hepatic collections and biopsy. The complications related to the use of the 3D X matrix probe were significantly lower than the 2D probe with a p value of 0.003. The timing of the procedure was shorter by the usage of a 3D X matrix probe in comparison with the 2D probe with a p value of 0.08, 0.34 for RFA and PEI and significantly shorter for MWA and drainage of hepatic collection, biopsy with a p value of 0.02, 0.001, respectively.Conclusions3D US-guided hepatic interventions by X matrix probe have better efficacy, less complication, and shorter time of procedure than the 2D US-guided hepatic interventions.

To compare the frequency of first attempt successful ultrasound guided radial artery cannulation by modified short axis out-of-plane technique versus conventional long axis in-plane technique.

Objective: To compare the frequency of first attempt successful ultrasound guided radial artery cannulation by modified short axis out-of-plane technique versus conventional long axis in-plane technique. Study Design: Quasi Experimental Study Setting: Jinnah Hospital, Lahore. Study Period: 1st January 2019 to 30th June 2019. Material & Methods: 180 patients fulfilling the selection criteria were divided in two groups using lottery method. Group modified SA-OOP (short axis out-of-plane) and group LA-IP (long axis in-plane). Modified Allen test was performed in all patients, if positive, procedure was carried out. In modified short axis out of plane approach, a suture was tied on the midpoint of ultrasound probe and perpendicular to the long axis as a guide and then radial artery was viewed by placing US probe on the wrist of patient transversely. The needle was inserted at 30⁰-45⁰ angle into the skin. In long Axis In- Plane approach, radial artery was first viewed by placing US probe transversely on the wrist of patient and then probe was rotated to 90⁰ in clockwise direction to see the artery in longitudinal plane. Then cannula was inserted at 30⁰-45⁰ angle into the skin. Success of first attempt was recorded. Results: The age range was 18-70 years. Mean age of the patients was 46.69 ± 17.35 and 43.68 ± 17.99 years in group LA-IP and SA-OOP, respectively (4). In group LA-IP, 57 patients (63.3%) were male and in group SA-OOP 45 patients (50%) were male while 33 patients (36.7%) of group LA-IP and 45 patients (50%) of group SA-OOP were female. Frequency of first attempt was 64.4% (58 patients) in group LA-IP and in group SA-OOP frequency of first attempt was 53.3% (48 patients). Statistically significant difference was not seen between two groups as p-value is 0.172. Conclusion: There is no difference in frequency of first attempt success in modified short axis out-of-plane ultrasound versus conventional long axis in-plane ultrasound to guide radial artery cannulation.

Innovative AI techniques to aid clinical diagnosis of complex lung pathologies in ultrasound images

Lung ultrasound (LUS) has recently gained increasing interest as a reliable method for point of care (POC) diagnostics and management of lung diseases. LUS is easily accessible, has no radiation-related risks and is portable, so it does not require relocating the patient, minimising the risk of further infection. This research aims to develop efficient and automated methods for lung pathology diagnosis using AI to support clinicians. We have introduced a binary classifier based on a state-of-the-art Swin Transformer to discriminate between LUS clips of healthy patients and patients with interstitial lung disease (ILD). Differently from previous approaches, this is better aligned with the current clinical assessments of ILD since it evaluates LUS clips instead of single frames; and does not require any additional annotations from clinicians, since its training is based only on the already available medical report. Furthermore, we propose an unsupervised deep learning approach (based on a generative adversarial network) to convert in real-time US volumes to MRI-like volumes of the thoracic region. This approach can be used to spatially localise the US probe with respect to the MRI in real-time and gather anatomical contextual information of the imaged region, providing thus guidance to clinicians.

Characterisation of laminarin extracted from brown seaweed Laminaria digitata, using optimized ultrasound- and ultrafiltration-assisted extraction method

The present study reported the extraction and characterisation of laminarin from Laminaria digitata. Hydrochloric acid concentration and extraction time were investigated by central composite design for optimizing extraction conditions. Regarding purification of the supernatant after the extraction process, membrane ultrafiltration was selected over pH shifting, ethanol precipitation and freeze-drying. With the assistance of ultrasound technology in the extraction process, the highest laminarin extraction yield and purity were obtained up to 57.34 ± 1.58 % and 81.10 ± 0.37 %, respectively. The molecular weight of laminarin extracts is in the range of 5.61 to 5.95 kDa. The Fourier-transform infrared spectroscopy (FT-IR) spectral features of the averaged spectra were depicted as absorbance peaks at the wavelengths of 3340 cm−1 and 2922 cm−1, which were related to OH and CH stretching of laminarin. US probe extract showed the highest scavenging capacity of 52.96 % while the HCl conventional extract exhibited the lowest scavenging capacity of 30.82 %. All the optimized laminarin extracts showed higher cytotoxicity in A549, A431, and Caco-2 carcinomas, effectively inducing cancer cell death in a time- and dose-dependent manner, and lower cytotoxicity in BEAS-2B normal human bronchial epithelial cells when compared to commercial laminarin.

Ultrasound Imaging with Flexible Array Transducer for Pancreatic Cancer Radiation Therapy

Pancreatic cancer with less than 10% 3-year survival rate is one of deadliest cancer types and greatly benefits from enhanced radiotherapy. Organ motion monitoring helps spare the normal tissue from high radiation and, in turn, enables the dose escalation to the target that has been shown to improve the effectiveness of RT by doubling and tripling post-RT survival rate. The flexible array transducer is a novel and promising solution to address the limitation of conventional US probes. We proposed a novel shape estimation for flexible array transducer using two sequential algorithms: (i) an optical tracking-based system that uses the optical markers coordinates attached to the probe at specific positions to estimate the array shape in real-time and (ii) a fully automatic shape optimization algorithm that automatically searches for the optimal array shape that results in the highest quality reconstructed image. We conducted phantom and in vivo experiments to evaluate the estimated array shapes and the accuracy of reconstructed US images. The proposed method reconstructed US images with low full-width-at-half-maximum (FWHM) of the point scatters, correct aspect ratio of the cyst, and high-matching score with the ground truth. Our results demonstrated that the proposed methods reconstruct high-quality ultrasound images with significantly less defocusing and distortion compared with those without any correction. Specifically, the automatic optimization method reduced the array shape estimation error to less than half-wavelength of transmitted wave, resulting in a high-quality reconstructed image.

A multimodal user interface for touchless control of robotic ultrasound

PurposePast research contained the investigation and development of robotic ultrasound. In this context, interfaces which allow for interaction with the robotic system are of paramount importance. Few researchers have addressed the issue of developing non-tactile interaction approaches, although they could be beneficial for maintaining sterility during medical procedures. Interaction could be supported by multimodality, which has the potential to enable intuitive and natural interaction. To assess the feasibility of multimodal interaction for non-tactile control of a co-located robotic ultrasound system, a novel human–robot interaction concept was developed.MethodsThe medical use case of needle-based interventions under hybrid computed tomography and ultrasound imaging was analyzed by interviewing four radiologists. From the resulting workflow, interaction tasks were derived which include human–robot interaction. Based on this, characteristics of a multimodal, touchless human–robot interface were elaborated, suitable interaction modalities were identified, and a corresponding interface was developed, which was thereafter evaluated in a user study with eight participants.ResultsThe implemented interface includes voice commands, combined with hand gesture control for discrete control and navigation interaction of the robotic US probe, respectively. The interaction concept was evaluated by the users in the form of a quantitative questionnaire with a average usability. Qualitative analysis of interview results revealed user satisfaction with the implemented interaction methods and potential improvements to the system.ConclusionA multimodal, touchless interaction concept for a robotic US for the use case of needle-based procedures in interventional radiology was developed, incorporating combined voice and hand gesture control. Future steps will include the integration of a solution for the missing haptic feedback and the evaluation of its clinical suitability.

Friday, June 17, 202212:30 PM - 1:30 PM PHSOR01 Presentation Time: 12:30 PM: Characterization of a Novel Multi-Modality Imaging Phantom for Ultrasound Interstitial Needle Guidance for High Dose Rate Gynecological Brachytherapy

<h3>Purpose</h3> To design, manufacture, and validate a realistic female pelvic phantom for multi-modality imaging on CT, MRI, and transrectal ultrasound (TRUS) to guide and track interstitial needles during an HDR gynecological procedure using a commercial needle tracking system. <h3>Materials and Methods</h3> The pelvic phantom was designed using 3D Slicer and Autodesk Fusion360 to model an average uterus from a 50 patient data study¹, a vaginal canal from KleenSpec speculum dimensions, and a rectum to accommodate a BK 8848 endocavity biplane US probe. A 1.5 cm x 3.0 cm x 1.25 cm (WxLxH) half ellipsoid CTV_HR was also designed. Modeled anatomy was Boolean subtracted from rectangular solids to create a negative space mold. An Ultimaker S3 printer was used to print the 3D molds using polylactic acid. Smooth-On Silicone 20T was used as a casting agent for the uterus, cervix, vaginal canal, and rectum based on their similar mechanical properties. A 3D printed box was constructed to house the designed anatomy to provide structural integrity and allow the insertion of a speculum, tandem and ovoid applicator, needles, and TRUS probe. Agarose gelatin with glycerol and cellulose was used as a background medium to surround and support the pelvic anatomy and to allow for US propagation. After manufacturing, the phantom was imaged with CT to identify potential imperfections that might impact its visualization on US images. Following initial CT validation, the tracking system with the endorectal probe was used to image the phantom. US images from a 180 degree sweep were acquired and a 3D US volume was generated that allowed uterus contouring to aid in real-time insertion of 2 needles (Needle1 in CTV_HR, Needle2 in uterus). After insertion, the phantom was imaged with a Siemens Biograph mCT using a slice thickness of 0.6 mm and with a Siemens Skyra 3T MRI using the institutional HDR brachytherapy MR imaging protocol with T1 and T2 weighted sequences. The CTV_HR and uterus were contoured on CT and MR images and their dimensions were checked against the CAD model. <h3>Results</h3> Fig. 1a shows the CAD model for the anatomy (uterus dimensions of 7.87 cm x 4.45 cm, rectum diameter of 2 cm), the encasing box, and the casting mold used to fabricate the phantom. The volumes of the CTV_HR and uterus reconstructed from the CAD model were 3 cm³ and 76.8 cm³, respectively. Figs. 1b-c show sagittal CT and US images of the phantom. The measurements of uterus dimensions (7.87 cm x 4.4 cm) and rectum diameter (2 cm) on the sagittal CT image demonstrated a high degree of fidelity with the CAD model. The uterus volume (77.1 cm³) reconstructed from CT images was also very similar to that from the CAD model. Fig. 1d shows the phantom setup for US imaging using the needle tracking system and BK 8848 endorectal probe. Representative sagittal images through the phantom at the location of the 2 implanted needles are shown in Figs. 1e-h (CT, T1w MRI, T2w MRI, and US, respectively). The overall volumes CTV_HR (3.2 cm³) and uterus (82.9 cm³) reconstructed from the T2w MR images also agreed with those from the CAD model. Fig. 1f shows axial and sagittal images of the 3D US volume from the tracking software (uterus contour in green). The generated volume allowed for intraoperative needle insertion guidance. <h3>Conclusions</h3> The manufactured pelvic phantom allows for accurate visualization with multiple imaging modalities and is conducive to applicator and needle insertion. The phantom is low cost and can be reproducibly manufactured with the 3D molding process. Our initial experiments demonstrate the ability to integrate the phantom with the commercial tracking system for future needle tracking validation studies. 1. Campelo, et al. (2020). Brachytherapy, 19(6), 767-776

Influence of the Field of View on Shear Wave Velocity Estimation

Abstract Tissue elasticity contains important information for physicians in diagnosis and treatment, and, e.g., can help in tumor detection because tumors are stiffer than healthy tissue. Ultrasound shear wave elastography imaging (US-SWEI) can be used to estimate tissue stiffness by measuring the velocity of induced shear waves. Commonly, a linear US probe is used to track shear waves at a high imaging frequency in 2D. Realtime US-SWEI is limited by the required time for data processing. Hence, reducing the imaging field of view (FOV) is beneficial as it decreases the size of the acquired data and thereby the acquisition, transfer and processing time. However, a decrease in the FOV has the disadvantage that shear waves are tracked over a smaller distance and thus, also fewer sampling points are available for velocity estimation. This trade-off between a smaller FOV and thus, a smaller data size, and the accuracy of shear wave velocity estimation is investigated in this work. For this purpose, shear waves were tracked with a linear US probe in gelatin phantoms with four different stiffness values. During data processing, we reduced the FOV virtually from 38.1mm to 2.1mm. It was found that a reduction of the FOV to 4.5mm leads to an overestimation of up to five times larger shear wave velocities but still allows to distinguish between phantoms of different stiffness. However, not all estimated velocity values could be clearly assigned to the correct stiffness value. The smallest studied FOV of 2.1mm was not sufficient for distinguishing between the phantoms anymore.

Saddle block anesthesia with 20 mg prilocaine hydrochloride 2% hyperbaric solution and intravenous fentanyl administration for transperineal MRI/US fusion-guided prostate biopsy

Introduction: MRI-Ultrasound (MRI/US) fusion-guided transperineal prostate biopsy (TPB) is gaining popularity in the diagnostic algorithm of prostate cancer. It is associated with higher pain score than the other methods of prostate biopsy. Effective analgesia is a key point for providing patient comfort and preventing his movement in response to pain with subsequent mismatch of the fused MRI/ US images. The mismatch could lead to inaccurate targeting of suspected cancer lesions. The preferred method of analgesia in an outpatient setting is topical intrarectal administration of lidocaine and periprostatic nerve block, but the pain and the discomfort from the procedure are not completely eliminated. Hypothetically, saddle block anesthesia has an expected better efficacy in relieving the pain from the MRI/US-TPB. Aim: To evaluate the efficacy and safety of saddle block anesthesia in patients undergoing MRI/US-TPB and сomparative analysis between patients who have received and have not received intravenous fentanyl Material and methods: A prospective randomized study was conducted on 12 consecutive patients undergoing MRI/US-TPB. Saddle block anesthesia was performed with 20 mg prilocaine hydrochloride 2% hyperbaric solution to all patients. 6 patients received intravenous fentanyl at a dose of 1mcg/kg (Group 1) and 6 patients did not receive intravenous fentanyl. It was examined: patient’s age, weight, height, BMI and ASA class; duration from the dural puncture to the end of the surgical intervention; taken number of prostate biopsies; presence of intraoperative pain; motor blockage; presence of a difference of more than 20%, before and after saddle block anesthesia, of non-invasively measured blood pressure and heart rate; additional medication; presence of early postoperative complications and recovery time from anesthesia Results: The comparative analysis of the preoperative characteristics of the both groups did not reveal significant statistical difference. There were comparatively similar indicators for surgical intervention and regional anesthesia in both groups. The both anesthesia techniques showed safety profile with hemodynamic stability, without additional medicine administration and lack of early post-anesthesia complications. Pain did not occur during inserting and moving the US probe into the anal canal and puncturing the perineal skin and the underlying tissues. 50% (3) of the patients in Group 2 had pain during the puncture of the prostate gland and biopsy extraction, while in Group 1 - 0% (0) of the patients reported presence of pain. There was a slightly delayed onset of the first postoperative pain in Group 1 - 113.17 ± 15.11 min. compared to Group 2 - 99.83 ± 11.51 min. Conclusion: The saddle block anesthesia with 20 mg prilocaine hydrochloride 2% hyperbaric solution in combination with intravenous fentanyl at a dose of 1 mcg/kg is a safe anesthesia technique, associated with excellent analgesic profile, low incidence of anesthesia-related complications and rapid recovery in patients undergoing MRI/US-TPB. Key words: saddle block, transperineal MRI/US fusion-guided prostate biopsy, prilocaine hydrochloride 2% hyperbaric solution

Ultrasound-Mediated Drug Delivery With a Clinical Ultrasound System: In Vitro Evaluation.

Chemotherapy efficacy is often reduced by insufficient drug uptake in tumor cells. The combination of ultrasound and microbubbles (USMB) has been shown to improve drug delivery and to enhance the efficacy of several drugs in vitro and in vivo, through effects collectively known as sonopermeation. However, clinical translation of USMB therapy is hampered by the large variety of (non-clinical) US set-ups and US parameters that are used in these studies, which are not easily translated to clinical practice. In order to facilitate clinical translation, the aim of this study was to prove that USMB therapy using a clinical ultrasound system (Philips iU22) in combination with clinically approved microbubbles (SonoVue) leads to efficient in vitro sonopermeation. To this end, we measured the efficacy of USMB therapy for different US probes (S5-1, C5-1 and C9-4) and US parameters in FaDu cells. The US probe with the lowest central frequency (i.e. 1.6 MHz for S5-1) showed the highest USMB-induced intracellular uptake of the fluorescent dye SYTOX™ Green (SG). These SG uptake levels were comparable to or even higher than those obtained with a custom-built US system with optimized US parameters. Moreover, USMB therapy with both the clinical and the custom-built US system increased the cytotoxicity of the hydrophilic drug bleomycin. Our results demonstrate that a clinical US system can be used to perform USMB therapy as efficiently as a single-element transducer set-up with optimized US parameters. Therefore, future trials could be based on these clinical US systems, including validated US parameters, in order to accelerate successful translation of USMB therapy.

Minimal invasive percutaneous nephrolithotomy (Mini-PCNL) in children: Ultrasound versus fluoroscopic guidance

Background: Miniaturization of endoscopic instruments in percutaneous nephrolithotomy (PCNL) allowed less invasive procedures with low complication rates, especially in children. This study was conducted to evaluate the safety and efficacy of ultrasonography-guided (USG) versus fluoroscopy-guided (FG) mini-PCNL in children.Materials and methods: This is a retrospective comparative study conducted from June 2015 to June 2020. The sample included 70 children (35 pateints underwent USG mini-PCNL and 35 pateints underwent FG mini-PCNL). They were compared mainly by the patients’ demographic characteristics, procedural information, and post-treatment outcomes. In the USG mini-PCNL group, puncturing was performed using a 3.5 MHz US probe, whereas fluoroscopy was utilized in the FG mini- PCNL group. Results: Both groups were comparable in terms of gender, previous history of failed ESWL, and hydronephrosis grade. The mean stone burden was 15.94 ± 3.69 mm and 19.20 ± 7.41 mm in USG and FG groups, respectively (p = 0.024). The stonefree rate (SFR) was 97.1% in the USG group and 94.3% in the FG group, which was not statistically significant (p = 0.16). Mean operative time in the USG group and FG group was 69.00 ± 13.33 minutes and 63.48 ± 16.90 minutes, respectively. Four (11.4%) patients in the FG group required blood transfusions to restore the hemodynamic state (p = 0.039). Fever was detected in 4 (11.4%) patients in the USG group and 15 (31.4%) patients in the FG group (p = 0.041). Conclusions: In children, mini PCNL under USG is safe and as effective as fluoroscopy.

Concurrent Validity and Reliability of Manual Versus Specific Device Transcostal Measurements for Breathing Diaphragm Thickness by Ultrasonography in Lumbopelvic Pain Athletes.

The use of rehabilitative ultrasound imaging (RUSI) to evaluate diaphragm thickness during breathing in athletes who suffer from non-specific lumbopelvic pain presents some measurement errors. The purpose of this study was to evaluate intra- and inter-sessions, intra- and inter-rater reliabilities, and concurrent validity of diaphragm thickness measurements during breathing using transcostal RUSI with a novel thoracic orthotic device that was used to fix the US probe versus those measurements obtained using manual fixation. A total of 37 athletes with non-specific lumbopelvic pain were recruited. Intra- (same examiner) and inter-rater (two examiners) and intra- (same day) and inter-session (alternate days) reliabilities were analyzed. All measurements were obtained after manual probe fixation and after positioning the thoracic orthotic device to fix the US probe in order to correctly correlate both measurement methods. Both left and right hemi-diaphragm thickness measurements were performed by transcostal RUSI at maximum inspiration, expiration, and the difference between the two parameters during relaxed breathing. Intra-class correlation coefficients (ICC), standard errors of measurement (SEM), minimum detectable changes (MCD), systematic errors, and correlations (r) were assessed. Orthotic device probe fixation showed excellent reliability (ICC = 0.852–0.996, SEM = 0.0002–0.054, and MDC = 0.002–0.072), and most measurements did not show significant systematic errors (p > 0.05). Despite manual probe fixation with a reliability ranging from good to excellent (ICC = 0.714–0.997, SEM = 0.003–0.023, and MDC = 0.008–0.064 cm), several significant systematic measurement errors (p < 0.05) were found. Most significant correlations between both orthotic device and manual probe fixation methods were moderate (r = 0.486–0.718; p < 0.05). Bland–Altman plots indicated adequate agreement between both measurement methods according to the agreement limits. The proposed novel thoracic orthotic device may allow ultrasound probe fixation to provide valid and reliable transcostal RUSI measurements of diaphragmatic thickness during relaxed breathing thus reducing some measurement errors and avoiding systematic measurement errors. It may be advisable to measure diaphragm thickness and facilitate visual biofeedback with respect to diaphragm re-education during normal breathing in athletes with non-specific lumbopelvic pain.

Fusion imaging in brain structure measurements on a fetus phantom, combining real-time ultrasound with magnetic resonance imaging.

ObjectivesTo assess synchronisation of MRI and US in measuring foetus phantom head structures; inter‐method, intra‐ and inter‐observer differences on biparietal diameter (BPD), head diameter, anterio‐posterior head diameter (HAP) and lateral ventricle structures (VS).MethodsFusion Imaging (FI) has been performed by combining MRI and US simultaneously. Axial scans of 1.5 Tesla MRI on a foetus phantom were acquired and uploaded on a US machine (EPIQ 7G, Philips). A PercuNav US tracker allowed the system to recognise and display the position of the transducer. A fetal phantom tracker was used as a phantom reference. Real‐time US of the phantom head was performed by synchronising the uploaded MRI images using different landmarks. Synchronisation has been assessed by taking measurements after rotating the US probe by 90. Measurements were taken by three different observers twice. Differences in measurements between MRI and US, inter‐, intra‐observer differences in all measurements were assessed.ResultsBPD, HAP and VS measurements before rotation were 0.13 ± 0.06 cm, 0.46 ± 0.09 cm and 0.4 ± 0.23 cm (width) and mean 0.6 ± 0.25 cm (length) larger at MRI than at US using any number of landmarks. After US probe rotation VS were 0.3 ± 0.24 cm in width and 0.3 ± 0.27 cm in length. Intra‐ and inter‐observer differences in all measurements were small.ConclusionsFI showed good synchronisation in measurements. BPD, HAP and VS were larger at MRI than US, likely a result of the way images are generated. Intra‐, inter‐observer differences between measurements were small. This can be important when reporting geometric measures from FI.

Challenges and Opportunities of Intraoperative 3D Ultrasound With Neuronavigation in Relation to Intraoperative MRI.

IntroductionNeuronavigation greatly improves the surgeons ability to approach, assess and operate on brain tumors, but tends to lose its accuracy as the surgery progresses and substantial brain shift and deformation occurs. Intraoperative MRI (iMRI) can partially address this problem but is resource intensive and workflow disruptive. Intraoperative ultrasound (iUS) provides real-time information that can be used to update neuronavigation and provide real-time information regarding the resection progress. We describe the intraoperative use of 3D iUS in relation to iMRI, and discuss the challenges and opportunities in its use in neurosurgical practice.MethodsWe performed a retrospective evaluation of patients who underwent image-guided brain tumor resection in which both 3D iUS and iMRI were used. The study was conducted between June 2020 and December 2020 when an extension of a commercially available navigation software was introduced in our practice enabling 3D iUS volumes to be reconstructed from tracked 2D iUS images. For each patient, three or more 3D iUS images were acquired during the procedure, and one iMRI was acquired towards the end. The iUS images included an extradural ultrasound sweep acquired before dural incision (iUS-1), a post-dural opening iUS (iUS-2), and a third iUS acquired immediately before the iMRI acquisition (iUS-3). iUS-1 and preoperative MRI were compared to evaluate the ability of iUS to visualize tumor boundaries and critical anatomic landmarks; iUS-3 and iMRI were compared to evaluate the ability of iUS for predicting residual tumor.ResultsTwenty-three patients were included in this study. Fifteen patients had tumors located in eloquent or near eloquent brain regions, the majority of patients had low grade gliomas (11), gross total resection was achieved in 12 patients, postoperative temporary deficits were observed in five patients. In twenty-two iUS was able to define tumor location, tumor margins, and was able to indicate relevant landmarks for orientation and guidance. In sixteen cases, white matter fiber tracts computed from preoperative dMRI were overlaid on the iUS images. In nineteen patients, the EOR (GTR or STR) was predicted by iUS and confirmed by iMRI. The remaining four patients where iUS was not able to evaluate the presence or absence of residual tumor were recurrent cases with a previous surgical cavity that hindered good contact between the US probe and the brainsurface.ConclusionThis recent experience at our institution illustrates the practical benefits, challenges, and opportunities of 3D iUS in relation to iMRI.

High Contrast Ultrasonic Method With Multi-Spatiotemporal Compounding for Monitoring Catheter-Based Ultrasound Thermal Therapy: Development and Ex Vivo Evaluations.

Changes in ultrasound backscatter energy (CBE) imaging can monitor thermal therapy. Catheter-based ultrasound (CBUS) can treat deep tumors with precise spatial control of energy deposition and ablation zones, of which CBE estimation can be limited by low contrast and robustness due to small or inconsistent changes in ultrasound data. This study develops a multi-spatiotemporal compounding CBE (MST-CBE) imaging approach for monitoring specific to CBUS thermal therapy. Ex vivo thermal ablations were performed with stereotactic positioning of a 180° directional CBUS applicator, temperature monitoring probes, endorectal US probe, and subsequent lesion sectioning and measurement. Five frames of raw radiofrequency data were acquired throughout in 15s intervals. Using window-by-window estimation methods, absolute and positive components of MST-CBE images at each point were obtained by the compounding ratio of squared envelope data within an increasing spatial size in each short-time window. Compared with conventional US, Nakagami, and CBE imaging, the detection contrast and robustness quantified by tissue-modification-ratio improved by 37.2 ± 4.7 (p < 0.001), 37.5 ± 5.2 (p < 0.001), and 6.4 ± 4.0 dB (p < 0.05) in the MST-CBE imaging, respectively. Correlation coefficient and bias between cross-sectional dimensions of the ablation zones measured in tissue sections and estimated from MST-CBE were up to 0.91 (p < 0.001) and -0.02 mm2, respectively. The MST-CBE approach can monitor the detailed changes within target tissues and effectively characterize the dimensions of the ablation zone during CBUS energy deposition. The MST-CBE approach could be practical for improved accuracy and contrast of monitoring and evaluation for CBUS thermal therapy.

Three-dimensional periodontal investigations using a prototype handheld ultrasound scanner with spatial positioning reading sensor

To demonstrate the feasibility of the 3D ultrasound periodontal tissue reconstruction of the lateral area of a porcine mandible using standard 2D ultrasound equipment and spatial positioning reading sensors. Periodontal 3D reconstructions were performed using a free-hand prototype based on a 2D US scanner and a spatial positioning reading sensor. For automated data processing, deep learning algorithms were implemented and trained using semi-automatically seg-mented images by highly specialized imaging professionals. US probe movement analysis showed that non-parallel 2D frames were acquired during the scanning procedure. Comparing 3 different 3D periodontal reconstructions of the same porcine mandible, the accuracy ranged between 0.179 mm and 0.235 mm. The present study demonstrated the diagnostic potential of 3D reconstruction using a free-hand 2D US scanner with spatial positioning readings. The use of auto-mated data processing with deep learning algorithms makes the process practical in the clinical environment for assessment of periodontal soft tissues.

Verification of Guiding Needle Placement by Registered Ultrasound Image During Combined Intracavitary/Interstitial Gynecologic Brachytherapy.

PurposeOur previous research demonstrated that under ideal conditions, rigid registration between MRI images and US images had high accuracy for real-time image guidance. The work presented in this paper focused on the application of the previously established procedures to a new context, including preoperative CT images.Materials and MethodsWe used a template to calibrate the US probe and completed the registration between preoperative CT images and US images. Marker experiments on the accuracy of real-time needle trajectories in CT images were performed using micro electromagnetic sensors. Pelvic phantom experiments were carried out to test the registration accuracy between CT and US images, in addition to registration accuracy between US images and real-time needle trajectories (real-time space model).ResultsThe US probe calibration error in CT images was 0.879 ± 0.149 mm. The difference of registration between US images and CT images was 0.935 ± 0.166 mm in the axial plane (n = 30) and 0.916 ± 0.143 mm in the sagittal plane (n =12). The difference of registration between US images and the needle’s real-time trajectories was 0.951 ± 0.202 mm.ConclusionUnder ideal conditions, rigid registration between CT images and US images had high accuracy for real-time image guidance.

Geometrically variable three-dimensional ultrasound for mechanically assisted image-guided therapy of focal liver cancer tumors.

Image-guided focal ablation procedures are first-line therapy options in the treatment of liver cancer tumors that provide advantageous reductions in patient recovery times and complication rates relative to open surgery. However, extensive physician training is required and image guidance variabilities during freehand therapy applicator placement limit the sufficiency of ablation volumes and the overall potential of these procedures. We propose the use of three-dimensional ultrasound (3D US) to provide guidance and localization of therapy applicators, augmenting current ablation therapies without the need for specialized procedure suites. We have developed a novel scanning mechanism for geometrically variable 3D US images, a mechanical tracking system, and a needle applicator insertion workflow using a custom needle applicator guide for targeted image-guided procedures. A three-motor scanner was designed to use any commercially available US probe to generate accurate, consistent, and geometrically variable 3D US images. The designed scanner was mounted on a counterbalanced stabilizing and mechanical tracking system for determining the US probe orientation, which was assessed using optical tracking. Further exploiting the utility of the motorized scanner, an image-guidance workflow was developed that moved the probe to any identified target within an acquired 3D US image. The complete 3D US guidance system was used to perform mock targeted interventional procedures on a phantom by selecting a target in a 3D US image, navigating to the target, and performing needle insertion using a custom 3D-printed needle applicator guide. Registered postinsertion 3D US images and cone-beam computed tomography (CBCT) images were used to evaluate tip targeting errors when using the motors, tracking system, or mixed navigation approaches. Two 3D US image geometries were investigated to assess the accuracy of a small-footprint tilt approach and a large field-of-view hybrid approach for a total of 48 targeted needle insertions. 3D US image quality was evaluated in a healthy volunteer and compared to a commercially available matrix array US probe. A mean positioning error of 1.85±1.33mm was observed when performing compound joint manipulations with the mechanical tracking system. A combined approach for navigation that incorporated the motorized movement and the in-plane tracking system corrections performed the best with a mean tip error of 3.77±2.27mm and 4.27±2.47mm based on 3D US and CBCT images, respectively. No significant differences were observed between hybrid and tilt image acquisition geometries with all mean registration errors ≤1.2mm. 3D US volunteer images resulted in clear reconstruction of clinically relevant anatomy. A mechanically tracked system with geometrically variable 3D US provides a utility that enables enhanced applicator guidance, placement verification, and improved clinical workflow during focal liver tumor ablation procedures. Evaluations of the tracking accuracy, targeting capabilities, and clinical imaging feasibility of the proposed 3D US system, provided evidence for clinical translation. This system could provide a workflow for improving applicator placement and reducing local cancer recurrence during interventional procedures treating liver cancer and has the potential to be expanded to other abdominal interventions and procedures.

Correction of wavelength-dependent laser fluence in swept-beam spectroscopic photoacoustic imaging with a hand-held probe

Recently, we demonstrated an integrated photoacoustic (PA) and ultrasound (PAUS) system using a kHz-rate wavelength-tunable laser and a swept-beam delivery approach. It irradiates a medium using a narrow laser beam swept at high repetition rate (∼1 kHz) over the desired imaging area, in contrast to the conventional PA approach using broad-beam illumination at a low repetition rate (10−50 Hz). Here, we present a method to correct the wavelength-dependent fluence distribution and demonstrate its performance in phantom studies using a conventional limited view/bandwidth hand-held US probe. We adopted analytic fluence models, extending diffusion theory for the case of a pencil beam obliquely incident on an optically homogenous turbid medium, and developed a robust method to estimate fluence attenuation in the medium using PA measurements acquired from multiple fiber-irradiation positions swept at a kHz rate. We conducted comprehensive simulation tests and phantom studies using well-known contrast-agents to validate the reliability of the fluence model and its spectral corrections.