Volumetric Tracking Research Articles

Deciphering pediatric low-grade glioma trajectories: Deep learning–based volumetrics for patients under surveillance.

2066 Background: Pediatric low-grade gliomas (pLGGs) have heterogeneous clinical presentations and prognoses. Given the morbidity of treatment, some suspected pLGGs, especially those found incidentally, are surveilled without treatment, though the natural histories of these tumors have yet to be systematically studied. We leveraged deep learning and multi-institutional data to methodically analyze longitudinal volumetric trajectories of pLGGs on surveillance, yielding insights into their growth trajectories and clinical implications. Methods: We conducted a pooled, retrospective study of pLGG patients diagnosed between 1992 and 2020 from two sources (Dana-Farber Cancer Institute/Boston Children’s Hospital and the Children's Brain Tumor Network), who were surveilled untreated for at least one-year post-diagnosis and who had linked clinical data and longitudinal MRI available. We applied a validated pLGG deep learning segmentation algorithm to longitudinal T2-weighted MRIs and calculated the 3-dimensional volumes at each timepoint. We evaluated individual tumor trajectories, curve shape, treatment initiation, and risk factors such as age, sex or tumor location for radiographic progression and regression (defined as volumetric change >=25% and <=-25% respectively) with univariable and multivariable logistic regression. Unsupervised time-series K-means and density-based spatial clustering with dynamic time wrapping were conducted to uncover volumetric phenotypes and a hybrid statistical time-series algorithm combining auto-regressive integrated moving average and generalized autoregressive conditional heteroskedasticity was evaluated to predict future volumetric changes. Results: Of 1774 scans from 129 patients (median follow-up of 4.0 years and median age of 13.9 years), baseline tumor median volume was 5.8 cm3 (range: 0.01-108.1), with 33 cortical (25.5%), 21 brainstem (16.2%), and 21 (16.2%) cerebellar locations. At the last follow-up, 33.8% of tumors progressed, 35.8% were stable, and 30.2% had regressed. Treatment was initiated for 46.5% of the tumors, of which 70.4% underwent surgery. Risk factors such as adolescent age, larger baseline volume size, cortical location and symptomatic presentation were most associated with progression ( p<0.05 for each). Clustering revealed three distinct volumetric phenotypes with diverging natural histories, corresponding to progression, stability or regression. The hybrid forecasting showed average root-mean-squared error values of >1 cm3 (std. >0.18 cm3) at training and testing combined. Conclusions: Deep learning auto-segmentation enables longitudinal, volumetric tracking of pLGG, yielding novel insights into the clinical trajectories of untreated tumors on surveillance, allowing a classification into progressors, regressors and stables.

Super-Resolution Ultrasound Imaging for Analysis of Microbubbles Cluster by Acoustic Vortex Tweezers.

Using acoustic vortex tweezers (AVT) to spatially accumulate microbubbles (MBs) shows promise for enhancing drug delivery efficiency and reducing off-target effects. The strong echogenicity of accumulated MBs also improves diagnostics via conventional ultrasound (US) B-mode imaging. However, the annular high-pressure distribution of AVT inhibits MBs inflow at the inlet, reducing MBs collection. The spatial resolution of US B-mode imaging further limits theranostic applications of AVT-mediated MBs accumulation. To address these challenges, we integrated an AVT waveform with volumetric super-resolution imaging (VSRI) to monitor the dynamic growth of MBs cluster during accumulation. We used a 5-MHz 2D array transducer for VSRI, employing plane wave pulses interleaved with accumulating pulses to retain MBs at a flow rate of 0.023-0.047 mL/s in a 3-mm vessel phantom. An asymmetrical AVT waveform (AVT*) was produced by modulating the pressure at the MBs inlet compared to the outlet. The effectiveness was validated in rat cerebral vessels for real-time volumetric tracking of MBs clusters. Microscopy observations showed that AVT* could quickly gather flowing MBs into cluster without repelling them at a flow rate of 0.023 mL/s. Statistical results indicated that microscopic data correlated better with VSRI than with B-mode images, suggesting VSRI suffices to detect the dynamics of AVT*-actuated MBs accumulation in real-time. Additionally, VSRI detected a significant increase in MBs cluster size over time during AVT* in the superior sagittal sinus of the rat brain. These findings demonstrate that the proposed strategy can accumulate the flowing MBs at a desired location and simultaneously observe this phenomenon.

In Vivo Graft Elongation After Arthroscopic Dermal Superior Capsular Reconstruction.

Superior capsular reconstruction (SCR) is a procedure purported to restore stability of the glenohumeral joint after an irreparable rotator cuff tear, but the in vivo behavior of the graft is unknown. Previous work has not evaluated the relationship between graft deformation, kinematics, and healing. To (1) determine regional graft elongation after SCR, (2) determine if graft elongation is related to graft healing, and (3) identify associations between graft elongation and changes in kinematics from presurgery to postsurgery. Case series; Level of evidence, 4. Ten patients who underwent SCR performed abduction and shoulder rotation with the arm at 90° of humerothoracic abduction before and 1 year after surgery while biplane radiographs were collected at 50 images per second. Kinematics was determined with submillimeter accuracy by matching patient-specific digitally reconstructed radiographs of the humerus and scapula to the biplane radiographs using a validated volumetric tracking technique. Graft elongation was calculated using motion of the graft anchors that were identified on postoperative magnetic resonance imaging. Differences in elongation between anterior and posterior regions of the graft, as well as associations between graft elongation, graft healing, and kinematics, were analyzed. Peak graft elongation ranged from a 3% decrease in the anterior region during rotation to up to a 171% increase in the anterior region during abduction and the posterior region during rotation. Grafts that were healed at both anterior anchors reached the intraoperative length at lower abduction angles (60°) than grafts that were not healed at 1 or both of the anterior anchors (87°) (P = .005). The posterior anchor graft origin to insertion distances were 2.1 mm farther apart after surgery compared with before surgery during both abduction and rotation. SCR dermal allografts are stretched well beyond their intraoperative length in vivo. Graft healing appears to be associated with less graft elongation. The posterior portion of the SCR graft does not appear to improve glenohumeral joint stability 1 year after surgery. Improved clinical outcomes after dermal allograft SCR may be because of the spacer effect of the graft rather than improved glenohumeral joint stability 1 year after surgery.

Photon-starved snapshot holography

Digital holography (DH) is a powerful imaging modality that is capable of capturing the object wavefront information, making it very valuable for diverse scientific research applications. Generally, it requires ample illumination to enable good fringe visibility and a sufficient signal-to-noise ratio. As such, in situations such as probing live cells with minimal light interaction and high-speed volumetric tracking in flow cytometry, the holograms generated with a limited photon budget suffer from poor pattern visibility. While it is possible to make use of photon-counting detectors to improve the hologram quality, the long recording procedure coupled with the need for mechanical scanning means that real-time extremely low-light holographic imaging remains a formidable challenge. Here, we develop a snapshot DH that can operate at an ultra-low photon level (less than one photon per pixel). This is achieved by leveraging a quanta image sensor to capture a stack of binary holographic frames and then computationally reconstructing the wavefront through integrating the mathematical imaging model and the data-driven processing, an approach that we termed PSHoloNet. The robustness and versatility of our DH system are demonstrated on both synthetic and experimental holograms with two common DH tasks, namely particle volumetric reconstruction and phase imaging. Our results demonstrate that it is possible to expand DH to the photon-starved regime, and our method will enable more advanced holography applications in various scientific imaging systems.

Fully volumetric tracking of melting fronts in phase change materials with computed tomography

Recent advances in laboratory X-ray computed tomography (XCT) enabled short acquisition times on the order of a few minutes, which enable the investigation of dynamic processes in-situ by time-lapse measurements. These advances open new opportunities for revealing information on the solid-liquid phase transformation occurring in phase changes materials (PCMs), which are a promising solution for designing compact latent thermal energy storage systems (LTES). In this contribution we report results obtained from the XCT System, “LuCi”, recently installed at Lucerne university of Applied Sciences and Arts, where the evolution of the melting process in an ice cube confined within a cylindrical, X-ray transparent sample holder is tracked. Our results indicate that even tiny differences of a few percent in the density of the two different phases can be differentiated in XCT measurements. The high-power X-ray source and a fast X-ray detector of LuCi enable the acquisition of a XCT measurement in a short period (< 1 – 6 minutes). By using proper image processing methods, estimates for the volumetric melting rate, the local melting front velocity, and the tree dimensional (3D) shape of the melting front were obtained from the four-dimensional (4D) imaging data. These results will help to build more efficient thermal energy storage systems in the future, which will support the energy turnaround.

Rapid Volumetric Optoacoustic Tracking of Nanoparticle Kinetics across Murine Organs.

Large-scale visualization of nanoparticle kinetics is essential for optimizing drug delivery and characterizing in vivo toxicity associated with engineered nanomaterials. Real-time tracking of nanoparticulate agents across multiple murine organs is hindered with the currently available whole-body preclinical imaging systems due to limitations in contrast, sensitivity, spatial, or temporal resolution. Herein, we demonstrate rapid volumetric tracking of gold nanoagent kinetics and biodistribution in mice at a suborgan level with single-sweep volumetric optoacoustic tomography (sSVOT). The imaging system accomplishes whole-body three-dimensional scans in less than 1.8 s, further attaining a high spatial resolution of 130 μm and sub-picomolar sensitivity. We visualized the clearance dynamics of purposely synthesized gold nanorods and nanorod clusters, featuring different sizes and surface chemistries as well as their corresponding accumulation within the liver and spleen. The newly discovered capacity to image rapid whole-body kinetics down to suborgan scales opens up new avenues for the development and characterization of diagnostic and therapeutic nanoagents.

3-D Ultrafast Ultrasound Imaging of Microbubbles Trapped Using an Acoustic Vortex.

Increasing the local concentration of microbubbles (MBs) within the blood flow plays a crucial role in several medical applications, but there are few imaging modalities available for volumetric tracking of the aggregated MBs in real time. Here we describe a device integrating acoustic vortex tweezers (AVTs) and ultrasound plane-wave imaging (PWI) to achieve the goal of controlling the spatial distribution of MBs in blood vessels and simultaneously monitoring this process using the same probe. Experiments were conducted using a 5-MHz 2-D array ultrasound probe (with three cycles of excitation at an acoustic pressure of 2000 kPa) and 1.2- [Formula: see text]-diameter MBs at a flow rate of 20 mm/s. The AVT waveform was produced by modulating the repetition frequency of the transmitted pulse asymmetrically (4 and 8 kHz at the inflow and outflow ends, respectively). In order to simultaneously capture MBs and carry out imaging with the same probe, the asymmetric AVT pulse signal and the ultrasound-imaging pulse signal were arranged in a staggered series, and the imaging was carried out using plane-wave pulses at nine angles (-7° to 7°) in compounded PWI (volume rate: 200 Hz). Microscopy observations showed that freely suspended MBs could indeed be gathered by the asymmetric AVT in the flow field to form an MBs cluster with a spot size of about [Formula: see text], which could resist the flow to remain at a fixed location for about 22 s. After the asymmetric AVT signal and the ultrasound-imaging pulse signal were turned on for 1 s, the ultrasound 3-D image showed that the signal intensity of the MB clusters increased by 13.1 dB ± 2.9 dB in relation to the background area. These results show that the proposed strategy can be used to accumulate flowing MBs at a desired location and to simultaneously observe this phenomenon. This tool could be used in the future to improve the outcomes of MB-related treatments for various diseases.

Reduced Movement Variability and Kinematics Changes During a Hand to Head Movement are Associated with Improved Outcome Following Superior Capsular Reconstruction (232)

Objectives:Patients with irreparable rotator cuff tears (RCT) exhibit functional limitations including limited ability to perform functional tasks such as combing their hair. One viable treatment is superior capsular reconstruction (SCR). SCR has been shown to restore stability of the glenohumeral (GH) joint in cadavers1, but its effect on in vivo scapular and humeral motion is unknown. The aims of this study were to determine the effect of SCR on in vivo scapular and humeral kinematics during a functional hand to head motion and to identify associations between shoulder kinematics and patient-reported outcomes (PROs). We hypothesized that moving the hand to the back of the head would be accomplished by using more GH based movement including rotation and abduction, and less scapular motion after SCR, and there would be a positive correlation between kinematics changes and improved PROs.Methods:Ten patients (8M, 2F, age 63 ± 7 years) with irreparable RCT provided informed consent to participate in this prospective IRB-approved study. American Shoulder and Elbow Surgeon (ASES), Disability of the Arm Shoulder and Hand (DASH), and Western Ontario Rotator Cuff Index (WORC) surveys were completed before (PRE) and 1-year (1YR-POST) after SCR. Participants were seated and instructed to move their hand from their lap to the back of their head while synchronized biplane radiographs of the shoulder were collected PRE and 1YR-POST at 50 images/s for 3 separate trials. Six degree of freedom GH and scapular kinematics were determined with sub-millimeter accuracy by matching subject-specific CT-based bone models of the humerus and scapula to the synchronized radiographs using a validated volumetric tracking technique3. The contributions of humeral abduction, plane of elevation and internal/external (I/E) rotation relative to the scapula, as well as scapular upward rotation, protraction, and tilt, were calculated for each subject before and after SCR. Differences in rotational contributions from PRE to POST were evaluated using a paired t-test. Variability in rotational contributions was characterized by the inter-subject standard deviation in rotational component contributions to the movement. Correlations among changes in the contribution of each rotation component and between the contribution of each rotation component and PROs were evaluated with Pearson’s correlation coefficients. Significance was set at p < 0.05 for all tests.Results:No differences in contribution to motion were identified in any of the rotational components from PRE to POST (all p > 0.15, Figure 1). Inter-subject variability in rotational contributions to the movement decreased in 5 of the 6 rotational components from PRE to 1YR-POST (Table 1; Figure 1). The PRE to 1YR POST change in contribution from GH abduction was positively correlated to the change in contribution from GH I/E rotation (Figure 2, R = 0.8, p = 0.001) and negatively correlated to the change in contribution from scapular protraction (Figure 2, R = -0.94, p = 0.001). ASES scores were negatively correlated with abduction contribution PRE (R = -0.65, p = 0.043), and positively correlated with plane of elevation PRE (R = 0.685, p = 0.03). Changes in the plane of elevation contribution were also positively correlated with changes in ASES scores (R = 0.635, p = 0.048).Conclusions:This is the first study to report GH and scapular kinematics when performing the functional task of placing the hand to the back of the head. Changes in contributions to the motion were inconsistent across subjects, making it difficult to find differences from PRE to POST. However, inter-subject variation was reduced following surgery, suggesting the participants’ movement strategy converged toward a more similar and possibly more efficient movement pattern following SCR. Increased contributions of glenohumeral rotation and abduction were offset by decreased scapular protraction and indicates SCR affects the contributions from these three rotations, partially supporting our first hypothesis. In addition, increased GH plane of elevation contribution following surgery was associated with improved ASES scores supporting our second hypothesis. This may be consistent with improved glenohumeral kinematics and efficiency of movement during a functional task following SCR. Future work will investigate GH and scapular kinematics in healthy individuals performing the hand to head movement to determine if movement strategy is closer to healthy after SCR.

MRI-guided cardiac-induced target motion tracking for atrial fibrillation cardiac radioablation

Background and purposeAtrial fibrillation (AF) cardiac radioablation (CR) challenges radiotherapy tracking: multiple small targets close to organs-at-risk undergo rapid differential cardiac contraction and respiratory motion. MR-guidance offers a real-time target tracking solution. This work develops and investigates MRI-guided tracking of AF CR targets with cardiac-induced motion. Materials and methodsA direct tracking method (Trackingdirect) and two indirect tracking methods leveraging population-based surrogacy relationships with the left atria (Trackingindirect_LA) or other target (Trackingindirect_target) were developed. Tracking performance was evaluated using transverse ECG-gated breathhold MRI images from 15 healthy and 10 AF participants. Geometric and volumetric tracking errors were calculated, defined as the difference between the ground-truth and tracked target centroids and volumes respectively. Transverse, breath-hold, noncardiac-gated cine images were acquired at 4 Hz in 5 healthy and 5 AF participants to qualitatively characterize tracking performance on images more comparable to MRILinac acquisitions. ResultsThe average 3D geometric tracking errors for Trackingdirect, Trackingindirect_LA and Trackingindirect_target respectively were 1.7 ± 1.2 mm, 1.6 ± 1.1 mm and 1.9 ± 1.3 mm in healthy participants and 1.7 ± 1.3 mm, 1.5 ± 1.0 mm and 1.7 ± 1.2 mm in AF participants. For Trackingdirect, 88% of analyzed images had 3D geometric tracking errors <3 mm and the average volume tracking error was 1.7 ± 1.3 cc. For Trackingdirect on non-cardiac-gated cine images, tracked targets overlapped organsat-risk or completely missed the target area on 2.2% and 0.08% of the images respectively. ConclusionThe feasibility of non-invasive MRI-guided tracking of cardiac-induced AF CR target motion was demonstrated for the first time, showing potential for improving AF CR treatment efficacy.

Visualization of Three-Dimensional Acoustic Streaming Flow Patterns around an Inclined Triangular Obstruction using Digital In-Line Holographic Micro-Particle Tracking Velocimetry

Acoustic Streaming is a flow phenomenon with many applications in the field of microfluidics, such as micro mixing[1, 2] and particle manipulation[3]. With the manufacturing techniques evolves, more complicated geometries can be designed for microfluidic device and 3-D acoustic streaming patterns may occurs. In this study, 3-D trajectories of particle induced by acoustic streaming around an inclined triangular obstruction in a microchannel were visualized by a volumetric tracking method using Digital Inline Holographic Microscopy (DIHM)[4-6]. The triangular obstruction has a tip angle of 20° and an inclined angle of 30°. The acoustic streaming is created under 12 kHz oscillation of a piezo plate driven by 20V voltage. Illuminated by a 450nm continuous laser, the magnified hologram of the motion of 1.79μm tracer particles was recorded by a low-cost 10X industrial microscope with a machine vision camera of 10 fps (frames per second). Using RayleighSommerfeld back-propagation method[7], particle locations was reconstructed frame by frame and 3-D tracking of individual particles was performed afterwards. The trajectories of each particle were reconstructed to reveal the vortical structure of the acoustic streaming flow. For the current system setup, the measurable range was estimated to be 550×685×840 μm3. The 3-D location reconstruction accuracy was verified with a calibration target and the location sensitivity was found to be linear throughout the measurable range. Reconstruction at different depth locations show that the dick-shaped calibration dots and the spherical polystyrene particles have different intensity profiles. The calibration dots show local minimum of intensity at the correct depth location, while polystyrene particles show local maximum of intensity instead. Resolved particle trajectories show that the acoustic streaming flows cause particles to move with 3-D spiral shaped motions near the side of the triangular obstruction, while particles away from the obstruction shows planar motions.

Motion, and Patient-Reported Outcomes

Objectives:Patients with irreparable rotator cuff tears (RCT) exhibit functional limitations believed to be caused by superior migration of the humerus1,2. One viable treatment is superior capsule reconstruction (SCR). SCR has been shown to restore stability of the glenohumeral (GH) joint in cadavers1, but its effectiveness at controlling in vivo humeral motion is unknown. Outcomes are typically evaluated through standard clinical radiographs to assess acromial-humeral distance (AHD), and patient-reported outcomes (PROs) such as ASES and Visual Analog Scale3. Reported changes in AHD are inconsistent, with some studies reporting an increase in AHD of 2.6 to 3.2 mm4,5, while other studies reported no significant change in AHD after SCR6,7. Additionally, AHD does not account for anterior-posterior translations of the humeral head and clinical radiographs cannot assess dynamic translation of the humerus during arm abduction. The aim of this study was to determine the in vivo effect of SCR on in vivo glenohumeral arthrokinematics during scapular abduction, and to compare these results to PROs. We hypothesized that static and dynamic AHD would increase, humeral head location on the glenoid would be more inferior at corresponding abduction angles after SCR, and changes in humeral head translation or AHD would correlate with increased GH abduction range of motion and improved PROs.Methods:Ten patients (8M, 2F, age 63 ± 7 years) with irreparable RCT provided informed consent to participate in this prospective IRB-approved study. ASES, DASH, and WORC surveys were completed before (PRE) and 1-year (1YR-POST) after SCR. Synchronized biplane radiographs of the shoulder were collected PRE and 1YR-POST at 50 images/s while patients performed 3 trials of scapular plane arm abduction. Biplane radiographs were also collected during a static neutral trial where the participants placed their hand on their lap. Six degree of freedom GH and scapular kinematics were determined with sub-millimeter accuracy by matching subject-specific CT-based bone models of the humerus and scapula to radiographs using a validated volumetric tracking technique8. AHD was calculated as the minimum distance between the acromion and the humerus at 10° increments of GH abduction and averaged throughout the motion. Humeral head translation, defined as the relative translation of the center of the humeral head compared to the center of the glenoid, was calculated at 10° increments of GH abduction and expressed as averages in the superior/inferior (SI) and anterior/posterior (AP) directions. Differences between PRE and 1YR-POST static AHD, average dynamic humeral head location, PROs, and maximum GH abduction were evaluated using a paired t-test. A Pearson correlation was used to determine associations between static AHD and average humeral head location, and both PROs and maximum GH abduction. Significance was set at p < 0.05 for all tests.Results:There was no difference in static AHD from PRE (5.3±1.6mm) to 1YR-POST (4.6±1.6mm) while the average dynamic AHD during GH abduction decreased from 2.7±1.2mm PRE to 2.3±1.0mm 1YR-POST (Figure 1). Static AHD was larger than the average dynamic AHD both PRE and 1YR-POST (Figure 1). The average position of the humeral head during abduction moved 1.5% of the glenoid height superior from PRE to 1YR-POST and 1.7% of the glenoid width anterior from PRE to 1YR-POST (Figure 2). ASES, WORC, and DASH scores significantly improved from PRE to 1YR-POST and maximum GH abduction significantly increased from PRE (78.1±23.1°) to 1YR-POST (93.9±12.3°) (Table 1). Interestingly, there was a positive correlation between the AP humeral head location and DASH score PRE such that a higher DASH score was associated with the humeral head being more anterior (R = 0.767). No other associations were found between either average humeral head locations or AHD and either PROs or maximum GH abduction at both time points as well as the changes in those measures between time points (all R < 0.67).Conclusions:Static AHD, as measured clinically, may not be a good representation of dynamic AHD during scapular abduction given the differences between the static and dynamic AHD measurements at similar abduction angles. Additionally, our in vivo kinematics findings are not consistent with prior results of a cadaver-based biomechanical study of SCR as we found were minute changes in the SI humeral head position, with a 0.4mm more superior humeral head position following SCR. Regardless, patient-reported qualitative outcomes and maximum GH abduction all improved significantly. This suggests clinical outcomes after SCR may be influenced by mechanisms other than restoration of humeral head translation. Future in vivo studies are needed to evaluate the kinematic mechanisms behind improved PROs after SCR.

Graft healing does not influence subjective outcomes and shoulder kinematics after superior capsule reconstruction: a prospective invivo kinematic study.

A viable treatment option for young patients with massive, irreparable rotator cuff tears is arthroscopic superior capsule reconstruction (SCR). SCR theoretically improves shoulder stability and function and decreases pain. However, no prospective studies to date have correlated magnetic resonance imaging (MRI) healing with invivo kinematic data. The purpose of this study was to evaluate the association between graft healing and invivo kinematics, range of motion (ROM), strength, and patient-reported outcomes (PROs). Ten patients (8 men and 2 women; mean age, 63 ± 7 years) with irreparable rotator cuff tears underwent arthroscopic SCR with dermal allograft. Strength was measured with isometric internal rotation and external rotation (ER) at 0° of abduction, ER at 90° of abduction, and scapular-plane abduction, whereas ROM was measured during shoulder flexion, abduction, and ER and internal rotation at 90° of abduction both before and 1 year after SCR. PROs included American Shoulder and Elbow Surgeons, Western Ontario Rotator Cuff Index, and Disabilities of the Arm, Shoulder and Hand surveys that were collected before and 1 year after SCR. Synchronized biplane radiographs were collected at 50 images/s before and 1 year after SCR while patients performed 3 trials of scapular-plane abduction. A validated volumetric tracking technique with submillimeter accuracy determined 6-df glenohumeral and scapular kinematics. The acromiohumeral distance (AHD), humeral head translation, and scapulohumeral rhythm (SHR) were calculated from the invivo kinematics. Healing at 5 locations was evaluated on 1-year postoperative MRI scans: anterior and posterior glenoid, anterior and posterior humerus, and posteriorly along the infraspinatus. Each subject was given a score from 0 to 5 based on number of sites healed. Of the 10 patients, 9 (90%) had complete (n = 4) or partial (n = 5) healing of the graft whereas 1 (10%) had complete failure at the glenoid. No correlation existed between MRI healing and the AHD, SHR, strength, ROM, or PROs. American Shoulder and Elbow Surgeons, Western Ontario Rotator Cuff Index, and Disabilities of the Arm, Shoulder and Hand scores all significantly improved from before to 1 year after SCR regardless of graft healing. The rate of complete or partial graft healing on MRI mimics findings of prior reports in the literature. MRI healing was correlated with humeral head anterior-posterior translation but not with the static and dynamic AHDs, SHR, humeral head superior-inferior translation, ROM, strength, or PROs 1 year after SCR. All PROs improved significantly from before to 1 year after SCR regardless of graft status on MRI. Invivo kinematic changes were small after SCR and not clinically significant, and the data suggest that improvements in clinical and functional outcomes may occur in the absence of full graft healing.

Flash Scanning Volumetric Optoacoustic Tomography for High Resolution Whole‐Body Tracking of Nanoagent Kinetics and Biodistribution

AbstractTracking of biodynamics across entire living organisms is essential for understanding complex biology and disease progression. The presently available small‐animal functional and molecular imaging modalities remain constrained by factors including long image acquisition times, low spatial resolution, limited penetration or poor contrast. Here flash scanning volumetric optoacoustic tomography (fSVOT), a new approach for high‐speed imaging of fast kinetics and biodistribution of optical contrast agents in whole mice that simultaneously provides reference images of vascular and organ anatomy with unrivaled fidelity and contrast, is presented. The imaging protocol employs continuous overfly scanning of a spherical matrix array transducer, accomplishing a 200 µm resolution 3D scan of the whole mouse body within 45 s without relying on signal averaging. This corresponds to an imaging speed gain of more than an order of magnitude compared with existing state‐of‐the‐art implementations of comparable resolution performance. Volumetric tracking and quantification of gold nanoagent and near infrared (NIR)‐II dye kinetics and their differential uptake in various organs are demonstrated. fSVOT thus offers unprecedented capabilities for multiscale imaging of pharmacokinetics and biodistribution with high contrast, resolution, and speed.

Patient-specific PTV margins for liver stereotactic body radiation therapy determined using support vector classification with an early warning system for margin adaptation.

An adaptive planning target volume (PTV) margin strategy incorporating a volumetric tracking error assessment after each fraction is proposed for robotic stereotactic body radiation therapy (SBRT) liver treatments. A supervised machine learning algorithm employing retrospective data, which emulates a dry-run session prior to planning, is used to investigate if motion tracking errors are <2mm, and consequently, planning target volume (PTV) margins can be reduced. A fraction of data collected during the beginning of a treatment course emulates a dry-run session (mock) before planning. Twenty features are calculated using mock data and used for support vector classification (SVC). A treatment course is labeled as Class 1 if the maximum root-mean-square radial tracking error for all remaining fractions is below 2mm, or Class 2 otherwise. We evaluate the classification using fivefold cross-validation, leave-one-out cross-validation, 500 repeated random subsampling cross-validation, and the receiver operating characteristic (ROC) metric. The classification is independently cross-validated on a cohort of 48 treatment plans for other anatomical sites. A per fraction assessment of volumetric tracking errors is performed for the standard 5mm PTV margin (PTVstd ) for courses predicted as Class 2; or for a margin reduced by 2mm (PTVstd-2mm ) for those predicted as Class 1. We perturb the gross tumor volume (GTV) by the tracking errors for each x-ray image acquisition and calculate the fractional GTV voxel occupancy probability (Pi ) inside the PTV for each treatment fraction i. For treatment courses classified as Class 1, an early warning system flags treatment courses having any Pi <0.99, and the subsequent treatments are proposed to be replanned using PTVstd . The classification accuracies are 0.84±0.06 using fivefold cross-validation, and 0.77 when validated using an independent testing set (other anatomical sites). Eighty percent of treatment courses are correctly classified using leave-one-out cross-validation. The sensitivity, precision, specificity, F1 score, and accuracy are 0.81±0.09, 0.85±0.08, 0.80±0.11, 0.83±0.06, and 0.80±0.07, respectively, using 500 repeated random subsampling cross-validation. The area under the curve for the ROC metric is 0.87±0.05. The four most important features for classification are related to standard deviations of motion tracking errors, the linearity between the target location and external LED marker positions, and marker radial motion amplitudes. Eleven of 64 cases predicted to be of Class 1 have 0.96<Pi <0.99 for each treatment fraction, and require replanning using PTVstd . In comparison, the PTVstd always covers the perturbed GTVs with Pi >0.99 for all patients. Support vector classification is proposed for the classification of different motion tracking errors for patient courses based on a mock session before planning for SBRT liver treatments. It is feasible to implement patient-specific PTV margins in the clinic, assisted with an early warning system to flag treatment courses that require replanning using larger PTV margins in an adaptive treatment strategy.

Changes in In Vivo Glenohumeral Joint Contact Patterns After Arthroscopic Superior Capsule Reconstruction

Objectives:Patients with irreparable rotator cuff tears (RCT) exhibit functional limitations believed to be caused by superior migration of the humerus1,2. One viable treatment is superior capsule reconstruction (SCR). SCR has been shown to restore stability of the glenohumeral (GH) joint in cadavers1, but its effectiveness at controlling in vivo humeral motion is unknown. Outcomes are typically evaluated through standard clinical radiographs to assess acromial-humeral distance (AHD), and patient-reported outcomes (PROs) such as ASES and Visual Analog Scale3. Reported changes in AHD are inconsistent, with some studies reporting an increase in AHD of 2.6 to 3.2 mm4,7, while other studies reported no significant change5,6 in AHD after SCR. Scapulohumeral rhythm (SHR), a measure of shoulder motion fluidity, has been reported at 2:1 (glenohumeral to scapulothoracic motion) in healthy individuals9, but the effects of SCR on SHR are unknown. The aim of this study was to determine the effect of SCR on static and dynamic AHD, shoulder function, and patient-reported outcomes. We hypothesized that after SCR, static and dynamic AHD would increase, SHR would approximate that of a healthy shoulder, maximum GH abduction would increase, and PROs would improve.Methods:Ten patients with irreparable RCT provided informed consent prior to receiving human dermal allograft SCR. To date, seven (6M, 1F, age 60 ± 8 years) have returned for 1 year post-operative testing. ASES, DASH, and WORC surveys were completed before (PRE), 6 months (6MO-POST), and 1-year after SCR (1YR-POST). Synchronized biplane radiographs of the shoulder were collected PRE and 1YR-POST at 50 images/s while patients performed 3 trials of scapular plane arm abduction. Six degree of freedom GH and scapular kinematics were determined with sub-millimeter accuracy by matching subject-specific CT-based bone models of the humerus and scapula to radiographs using a validated volumetric tracking technique8. AHD was calculated as the minimum distance between the acromion and the humerus at 5° increments of GH abduction. Scapulohumeral rhythm (SHR) was calculated by finding the average change in glenohumeral abduction per degree of scapular upward rotation during scapular abduction.Differences between PRE and 1YR-POST SHR and static AHD distance were evaluated using a paired t-test with significance set at p < 0.05. Changes in PROs were compared to the minimum clinically important difference (MCID).Results:There was a trend toward decreasing static AHD from PRE to 1YR-POST (average decrease: 1.5±1.6mm (p=0.06), however, dynamic AHD did not change from PRE to 1 YR-POST between 45° and 95° of glenohumeral abduction (all p > 0.11) (Figure 1). There was a trend toward increased SHR from 1.1 ± 0.5 PRE to 1.5 ± 0.3 1YR-POST (p = 0.08) (Figure 2), while the increase in maximum GH abduction during scapular abduction from PRE (76.7°±24.5°) to 1YR-POST (91.8°±14.9°) was not statistically significant (p = 0.14) (Figure 2). ASES, WORC, and DASH scores improved beyond the minimum clinically important difference from PRE to 1YR-POST (Table 1) for all patients.Conclusion:In general, SHR tended to more closely resemble that of a healthy shoulder following SCR. Althoughaverage maximum GH abduction was higher postoperatively than preoperatively, that increase was not statistically significant and may reflect that most patients in our cohort had reasonable preoperative abduction. In contrast to those quantitative measures of shoulder function, patient-reported qualitative outcomes all improved significantly. Conflicting results between static and dynamic AHD during higher glenohumeral abduction angles suggest SCR does not appear to affect AHD in higher abduction angles, though the static AHD suggests there may be a difference at lower abduction angles. Dynamic measurements of AHD at lower abduction angles will be necessary to fully characterize the dynamic changes of AHD following SCR.Figure 1.Patient-reported outcomes. Bolded scores represent changes greater than the minimum clinically important different (MCID) compared to PRE and average contact center locations ± 1 standard deviation throughout scapular plane abdjuction. Black + indicates the glenoid center with anterior (A) and posterior (P) directions indicated on the glenoid.

Volumetric tracking of migratory melanophores during zebrafish development by optoacoustic microscopy

Unveiling mechanisms driving specification, recruitment and regeneration of melanophores is key in understanding melanin-related disorders. This study reports on the applicability of a hybrid focus optoacoustic microscope (HFOAM) for volumetric tracking of migratory melanophores in developing zebrafish. The excellent contrast from highly-absorbing melanin provided by the method is shown to be ideal for label-free dynamic visualization of melanophores in their unperturbed environment. We established safe laser energy levels that enable high-contrast longitudinal tracking of the cells over an extended period of developmental time without causing cell toxicity or pigment bleaching. Owing to its hybrid optical and acoustic resolution, the new imaging technique can be seamlessly applied for noninvasive studies of both optically-transparent larval as well as adult stages of the zebrafish model organism, which is not possible using other optical microscopy methods.

Erratum: High-frame rate four dimensional optoacoustic tomography enables visualization of cardiovascular dynamics and mouse heart perfusion

Functional imaging of mouse models of cardiac health and disease provides a major contribution to our fundamental understanding of the mammalian heart. However, imaging murine hearts presents significant challenges due to their small size and rapid heart rate. Here we demonstrate the feasibility of high-frame-rate, noninvasive optoacoustic imaging of the murine heart. The temporal resolution of 50 three-dimensional frames per second provides functional information at important phases of the cardiac cycle without the use of gating or other motion-reduction methods. Differentiation of the blood oxygenation state in the heart chambers was enabled by exploiting the wavelength dependence of optoacoustic signals. Real-time volumetric tracking of blood perfusion in the cardiac chambers was also evaluated using indocyanine green. Taken together, the newly-discovered capacities offer a unique tool set for in-vivo structural and functional imaging of the whole heart with high spatio-temporal resolution in all three dimensions.

High-frame rate four dimensional optoacoustic tomography enables visualization of cardiovascular dynamics and mouse heart perfusion.

Functional imaging of mouse models of cardiac health and disease provides a major contribution to our fundamental understanding of the mammalian heart. However, imaging murine hearts presents significant challenges due to their small size and rapid heart rate. Here we demonstrate the feasibility of high-frame-rate, noninvasive optoacoustic imaging of the murine heart. The temporal resolution of 50 three-dimensional frames per second provides functional information at important phases of the cardiac cycle without the use of gating or other motion-reduction methods. Differentiation of the blood oxygenation state in the heart chambers was enabled by exploiting the wavelength dependence of optoacoustic signals. Real-time volumetric tracking of blood perfusion in the cardiac chambers was also evaluated using indocyanine green. Taken together, the newly-discovered capacities offer a unique tool set for in-vivo structural and functional imaging of the whole heart with high spatio-temporal resolution in all three dimensions.

Hydrodynamic Trails Produced by Daphnia: Size and Energetics

This study focuses on quantifying hydrodynamic trails produced by freely swimming zooplankton. We combined volumetric tracking of swimming trajectories with planar observations of the flow field induced by Daphnia of different size and swimming in different patterns. Spatial extension of the planar flow field along the trajectories was used to interrogate the dimensions (length and volume) and energetics (dissipation rate of kinetic energy and total dissipated power) of the trails. Our findings demonstrate that neither swimming pattern nor size of the organisms affect the trail width or the dissipation rate. However, we found that the trail volume increases with increasing organism size and swimming velocity, more precisely the trail volume is proportional to the third power of Reynolds number. This increase furthermore results in significantly enhanced total dissipated power at higher Reynolds number. The biggest trail volume observed corresponds to about 500 times the body volume of the largest daphnids. Trail-averaged viscous dissipation rate of the swimming daphnids vary in the range of to and the observed magnitudes of total dissipated power between and , respectively. Among other zooplankton species, daphnids display the highest total dissipated power in their trails. These findings are discussed in the context of fluid mixing and transport by organisms swimming at intermediate Reynolds numbers.

Cervical spine intervertebral kinematics with respect to the head are different during flexion and extension motions

Previous dynamic imaging studies of the cervical spine have focused entirely on intervertebral kinematics while neglecting to investigate the relationship between head motion and intervertebral motion. Specifically, it is unknown if the relationship between head and intervertebral kinematics is affected by movement direction. We tested the hypothesis that there would be no difference in sagittal plane intervertebral angles at identical head orientations during the flexion and extension movements. Nineteen asymptomatic subjects performed continuous head flexion-extension movements while biplane radiographs were collected at 30 images per second. A previously validated model-based volumetric tracking process determined three-dimensional vertebral position with sub-millimeter accuracy throughout the flexion–extension motion. Head movement was recorded at 60Hz using conventional motion analysis and reflective markers. Intervertebral angles were determined at identical head orientations during the flexion and extension movements. Cervical motion segments were in a more extended orientation during flexion and in a more flexed orientation during extension for any given head orientation. The results suggest that static radiographs cannot accurately represent vertebral orientation during dynamic motion. Further, data should be collected during both flexion and extension movements when investigating intervertebral kinematics with respect to global head orientation. Also, in vitro protocols that use intervertebral total range of motion as validation criteria may be improved by assessing model fidelity using continuous intervertebral kinematics in flexion and in extension. Finally, musculoskeletal models of the head and cervical spine should account for the direction of head motion when determining muscle moment arms because vertebral orientations (and therefore muscle attachment sites) are dependent on the direction of head motion.