Internal Organ Motion Research Articles

Features of diagnosis and treatment of a polytrauma victim with predominant closed chest trauma with lung and diaphragm rupture. Clinical case

The article describes a clinical case and presents clinical signs of traumatic rupture of the diaphragm and lung on the background of a wave‑like course of the postoperative period. Open diaphragmatic injuries are more common than closed ones. In this case, the closed chest and abdominal trauma was sustained as a result of a road traffic accident. The injury was combined and severe, with signs of traumatic shock. The location of the diaphragmatic injury was on the right side, which is less common. The severe condition of the patient with respiratory failure (respiratory rate over 30 per minute) was an indication for artificial lung ventilation, which made it impossible to take complaints and anamnesis. The individual spatial topography of the diaphragm depends on the size and location of the abdominal organs, body structure, and depends on the line of examination. The movement of internal organs into the pleural cavity indicates a diaphragmatic rupture, but in this case, the extrahepatic location of the diaphragmatic defect was covered by the liver, the lower lobe of the right lung, and adhesions, which led to the cover­up of the diaphragmatic defect. Increased abdominal size due to polytrauma and mechanical ventilation in case of closed chest and abdominal trauma; increased air discharge through pleural drainage during video laparoscopy or increased abdominal size during video thoracoscopy; clamping of the pleural drainage with a spiral computed tomography of the chest and abdominal organs allows detecting pneumoperitoneum and pneumothorax, which indicates the presence of a defect in the diaphragm and lung. The use of video thoracoscopy, video laparoscopy, and spiral computed tomography does not always provide complete information about the existing damage to the diaphragm, so dynamic observation with control radiological examinations is preferred.

Effect of Different Dose Rates on Dosimetric Parameters and Accuracy of the Pretreatment Quality Assurance During Intensity-modulated Radiotherapy Planning Using Anthropomorphic Phantom

Background: This study investigates the impact of varying dose rates on dosimetric parameters and pretreatment quality assurance (QA) accuracy in intensity-modulated radiotherapy (IMRT) planning using anthropomorphic phantoms. The research explores the dosimetric effects of different dose rates ranging from 100 to 600 monitor units per minute (MU/min) on parameters such as Homogeneity Index (HI), Conformity Index (CI), and dose to organs at risk (OAR). Method: Anthropomorphic phantoms, mimicking human tissues, were employed for simulation. Treatment plans were generated using the Eclipse Treatment Planning System, and dosimetric evaluations were conducted using cumulative dose-volume histograms (DVH). Furthermore, pretreatment patient-specific QA was performed using EPID portal dosimetry and Delta4 dosimetry system. Result: Treatment plans adhere to institutional protocol, ensuring the target receives ≥95% of the prescription dose while meeting OAR constraints. All plans maintain target homogeneity and conformality, keeping maximum doses within the target below 107%. Low dose plans exhibit superior target coverage, conformality, and homogeneity compared to higher doses. However, increased dose rates elevate delivered Monitor Units and maximum doses to critical structures. Gamma passing rates vary with dose rates, with the lowest at 100 MU/min and the highest at 400 MU/min for 1% 1mm criteria. Dosimetric evaluations using Delta 4 and EPID QA methods confirm plan validity across different dose rates. Conclusion: Low dose rate dosimetry is superior to higher rates for target and organ-at-risk (OAR) delivery, albeit prolonging delivery time and affecting internal organ motion. Portal dosimetry offers a faster, more convenient tool for IMRT pretreatment quality assurance (QA). Optimal results are achieved at 400 MU/min, enhancing gamma agreement between calculated and measured portal doses for complex fields. This improvement in QA enhances IMRT treatment delivery quality. However, patient-specific QA using the DELTA4 dosimetry system and ICRU 83 recommendations are insufficient for discussing dosimetric differences relevant to patient treatment.

CT respiratory motion synthesis using joint supervised and adversarial learning

Objective. Four-dimensional computed tomography (4DCT) imaging consists in reconstructing a CT acquisition into multiple phases to track internal organ and tumor motion. It is commonly used in radiotherapy treatment planning to establish planning target volumes. However, 4DCT increases protocol complexity, may not align with patient breathing during treatment, and lead to higher radiation delivery. Approach. In this study, we propose a deep synthesis method to generate pseudo respiratory CT phases from static images for motion-aware treatment planning. The model produces patient-specific deformation vector fields (DVFs) by conditioning synthesis on external patient surface-based estimation, mimicking respiratory monitoring devices. A key methodological contribution is to encourage DVF realism through supervised DVF training while using an adversarial term jointly not only on the warped image but also on the magnitude of the DVF itself. This way, we avoid excessive smoothness typically obtained through deep unsupervised learning, and encourage correlations with the respiratory amplitude. Main results. Performance is evaluated using real 4DCT acquisitions with smaller tumor volumes than previously reported. Results demonstrate for the first time that the generated pseudo-respiratory CT phases can capture organ and tumor motion with similar accuracy to repeated 4DCT scans of the same patient. Mean inter-scans tumor center-of-mass distances and Dice similarity coefficients were 1.97 mm and 0.63, respectively, for real 4DCT phases and 2.35 mm and 0.71 for synthetic phases, and compares favorably to a state-of-the-art technique (RMSim). Significance. This study presents a deep image synthesis method that addresses the limitations of conventional 4DCT by generating pseudo-respiratory CT phases from static images. Although further studies are needed to assess the dosimetric impact of the proposed method, this approach has the potential to reduce radiation exposure in radiotherapy treatment planning while maintaining accurate motion representation. Our training and testing code can be found at https://github.com/cyiheng/Dynagan.

Super-Resolution Neural Network Models Comparison Metod for Brain MRI Images Based on PSNR and SSIM Metrics

The diagnosis of many diseases is largely possible thanks to MRI(Magnetic Resonance Imaging). This technology allows to study internal organs of the patient: the brain, spine, bones, joints, vessels and etc. The resolution of the MRI image is limited due to various factors: movement of the patient during the scan, the continuous movement of internal organs. The higher the quality of the MRI image, the longer it takes to scan. For more accurate diagnostics it is possible to increase resolution of the yielded images. This is achieved by using SISR(Single Image Super Resolution) algorithms, which allow you to obtain images with increased resolution from a single input image. In this paper the idea of the image super-resolution algorithms is presented, various forms of the problem and solutions to it are provided. The advantages of the SISR algorithms are described. The relevance of this task in the field of medical MRI images is explained. Metrics for comparing image quality PSNR and SSIM are given and described. A dataset for testing is presented. The stage of data preparation is described: the principle of selecting images from a set of datasets, converting data into the required format, compressing images to obtain input data for selected neural network models. The PSNR, SSIM metrics of two neural network models mDCSRN and FAWDN are measured on equally prepared input data. The comparison results are presented in the form of images and averaged data for the entire sample is stored in the table.

Role of gastrointestinal ultrasound in image-guided radiation therapy: A review

Radiation therapy is one of the main modalities for cancer treatment. New radiotherapy techniques provide conformal radiation dose distribution and need higher accuracy in treatment delivery. Internal organ motions and displacements between and within the radiotherapy treatment fraction affect and weaken the reproducibility of delivering the planned irradiation to the target position. Image-guided radiation therapy (IGRT) can be used as a critical technology to improve patient positioning accuracy and reduce uncertainties in tumor target definition during treatment delivery. Ultrasound, a non-invasive imaging technique, is one of the important modalities in IGRT for accurate pre-treatment patient positioning and fiducial marker placement. The current study purposed to summarize recent advancements in ultrasound applications, techniques, and possible use in radiotherapy for cancers located in the abdomen and pelvic regions. We hope to give the readers a comprehensive understanding of the emerging clinical ultrasound-based IGRT applications and techniques.

Batteryless, Wireless, and Secure SoC for Implantable Strain Sensing

The past few years have witnessed a growing interest in wireless and batteryless implants, due to their potential in long-term biomedical monitoring of in-body conditions such as internal organ movements, bladder pressure, and gastrointestinal health. Early proposals for batteryless implants relied on inductive near-field coupling and ultrasound harvesting, which require direct contact between the external power source and the human body. To overcome this near-field challenge, recent research has investigated the use of RF backscatter in wireless micro-implants because of its ability to communicate with wireless receivers that are placed at a distance outside the body ( 0.5 m), allowing a more seamless user experience. Unfortunately, existing far-field backscatter designs remain limited in their functionality: they cannot perform biometric sensing or secure data transmission; they also suffer from degraded harvesting efficiency and backscatter range due to the impact of variations in the surrounding tissues. In this paper, we present the design of a batteryless, wireless and secure system-on-chip (SoC) implant for in-body strain sensing. The SoC relies on four features: 1) employing a reconfigurable in-body rectenna which can operate across tissues adapting its backscatter bandwidth and center frequency; 2) designing an energy efficient 1.37 mmHg strain sensing front-end with an efficiency of 5.9 mmHg·nJ/conversion; 3) incorporating an AES-GCM security engine to ensure the authenticity and confidentiality of sensed data while sharing the ADC with the sensor interface for an area efficient random number generation; 4) implementing an over-the-air closed-loop wireless programming scheme to reprogram the RF front-end to adapt for surrounding tissues and the sensor front-end to achieve faster settling times below 2 s.

Perovskite Piezoelectric-Based Flexible Energy Harvesters for Self-Powered Implantable and Wearable IoT Devices

In the ongoing fourth industrial revolution, the internet of things (IoT) will play a crucial role in collecting and analyzing information related to human healthcare, public safety, environmental monitoring and home/industrial automation. Even though conventional batteries are widely used to operate IoT devices as a power source, these batteries have a drawback of limited capacity, which impedes broad commercialization of the IoT. In this regard, piezoelectric energy harvesting technology has attracted a great deal of attention because piezoelectric materials can convert electricity from mechanical and vibrational movements in the ambient environment. In particular, piezoelectric-based flexible energy harvesters can precisely harvest tiny mechanical movements of muscles and internal organs from the human body to produce electricity. These inherent properties of flexible piezoelectric harvesters make it possible to eliminate conventional batteries for lifetime extension of implantable and wearable IoTs. This paper describes the progress of piezoelectric perovskite material-based flexible energy harvesters for self-powered IoT devices for biomedical/wearable electronics over the last decade.

Unexpected Movement of the Esophagus across the Aorta

Tumor regression throughout treatment would induce organ movement, but little is known of this in the esophagus. To achieve successful tumor regression, radiation therapy requires several weeks of radiation to be delivered accurately to the tumor. Usually, a 5–10 mm margin is allowed for set-up error and internal organ motion. Our case exhibited an unexpectedly large movement of the esophagus across the aorta with tumor regression that extended outside the margin and thus outside the radiotherapy field. These movements may affect subsequent invasive procedures or treatment during cancer therapy. After the unexpected large movement of the esophagus due to tumor regression, we revised the radiotherapy plan to reflect the new esophageal position. This implied that regular imaging and close monitoring are required during treatment of esophageal cancer.

Towards range-guidance in proton therapy to detect organ motion-induced dose degradations

Introduction. Internal organ motion and deformations may cause dose degradations in proton therapy (PT) that are challenging to resolve using conventional image-guidance strategies. This study aimed to investigate the potential of range guidance using water-equivalent path length (WEPL) calculations to detect dose degradations occurring in PT. Materials and methods. Proton ranges were estimated using WEPL calculations. Field-specific isodose surfaces in the planning CT (pCT), from robustly optimised five-field proton plans (opposing lateral and three posterior/posterior oblique beams) for locally advanced prostate cancer patients, were used as starting points. WEPLs to each point on the field-specific isodoses in the pCT were calculated. The corresponding range for each point was found in the repeat CTs (rCTs). The spatial agreement between the resulting surfaces in the rCTs (hereafter referred to as iso-WEPLs) and the isodoses re-calculated in rCTs was evaluated for different dose levels and Hausdorff thresholds (2–5 mm). Finally, the sensitivity and specificity of detecting target dose degradation (V95% < 95%) using spatial agreement measures between the iso-WEPLs and isodoses in the pCT was evaluated. Results. The spatial agreement between the iso-WEPLs and isodoses in the rCTs depended on the Hausdorff threshold. The agreement was 65%–88% for a 2 mm threshold, 83%–96% for 3 mm, 90%–99% for 4 mm, and 94%–99% for 5 mm, across all fields and isodose levels. Minor differences were observed between the different isodose levels investigated. Target dose degradations were detected with 82%–100% sensitivity and 75%–80% specificity using a 2 mm Hausdorff threshold for the lateral fields. Conclusion. Iso-WEPLs were comparable to isodoses re-calculated in the rCTs. The proposed strategy could detect target dose degradations occurring in the rCTs and could be an alternative to a fully-fledged dose re-calculation to detect anatomical variations severely influencing the proton range.

Normal Tissue Risk Estimation Using Biological Knowledge-Based Fuzzy Logic in Volumetric Modulated Arc Therapy of Prostate Cancer: Rectum.

Objective:Most radiotherapy patients with prostate cancer are treated with volumetric modulated arc therapy (VMAT). Advantages of VMAT may be limited by daily treatment uncertainties such as setup errors, internal organ motion, and deformation. The position and shape of prostate target as well as normal organ, i.e., rectum volume around the target, may change during the course of treatment. The aim of the present work is to estimate rectal toxicity estimation using a novel two-level biological knowledge-based fuzzy logic method. Both prostate and rectal internal motions as well as setup uncertainties are considered without compromising target dose distribution in the present study.Materials and Methods:The Mamdani-type fuzzy logic framework was considered in two levels. The prostate target volume changes from minimum to maximum during the course of treatment. In the first level, the fuzzy logic was applied for determining biological acceptable target margin using tumor control probability and normal tissue complication probability (NTCP) parameters based on prostate target motion limits, and then, fuzzy margin was derived. The output margin of first-level fuzzy logic was compared to currently used margins. In second-level fuzzy, rectal volume variation with weekly analysis of cone-beam computed tomography (CBCT) was considered. The biological parameter (NTCP) was calculated corresponding to rectal subvolume variation with weekly CBCT image analysis. Using irradiated volume versus organ risk relationship from treatment planning, the overlapped risk volumes were estimated. Fuzzy rules and membership function were used based on setup errors, asymmetrical nature of organ motion, and limitations of normal tissue toxicity in Mamdani-type Fuzzy Inference System.Results:For total displacement, standard errors of prostate ranging from 0 to 5 mm range were considered in the present study. In the first level, fuzzy planning target volume (PTV) margin was found to be similar or up to 0.5 mm bigger than the conventional margin, but taking the modeling uncertainty into account resulted in a good match between the calculated fuzzy PTV margin and conventional margin formulations under error 0–5 mm standard deviation (SD) range. With application of fuzzy margin obtained from first-level fuzzy, overlapped rectal volumes and corresponding NTCP values were fuzzified in second-level fuzzy using rectal volume variations. The final risk factor (RF) of rectum was qualitatively assessed and found clinically acceptable for each fractional volume of irradiated to total volume and relevant NTCP values. The reason may be at 5 mm SD displacement error range, NTCP values would be within acceptable limit without compromising the tumor dose distribution though the confounding factors such as organ motion, deformation of rectum, and in-house image matching protocols exist.Conclusion:A new approach of two-level fuzzy logic may be suitable to estimate possible organ-at-risk (OAR) toxicity biologically without compromising tumor volume that includes both prostate target and OAR rectum deformation even at displacement standard errors of prostate ranging from 0 to 5 mm range which was considered in the present study. Using proposed simple and fast method, there is an interplay between volume-risk relationship and NTCP of OARs to judge real-time normal organ risk level or alter the treatment margins, particularly concern to individual factors such as comorbidities, genetic predisposition, and other lifestyle choices even at high displacement errors >5 mm SD range.

Synergistic motion compensation strategies for positron emission tomography when acquired simultaneously with magnetic resonance imaging.

Subject motion in positron emission tomography (PET) is a key factor that degrades image resolution and quality, limiting its potential capabilities. Correcting for it is complicated due to the lack of sufficient measured PET data from each position. This poses a significant barrier in calculating the amount of motion occurring during a scan. Motion correction can be implemented at different stages of data processing either during or after image reconstruction, and once applied accurately can substantially improve image quality and information accuracy. With the development of integrated PET-MRI (magnetic resonance imaging) scanners, internal organ motion can be measured concurrently with both PET and MRI. In this review paper, we explore the synergistic use of PET and MRI data to correct for any motion that affects the PET images. Different types of motion that can occur during PET-MRI acquisitions are presented and the associated motion detection, estimation and correction methods are reviewed. Finally, some highlights from recent literature in selected human and animal imaging applications are presented and the importance of motion correction for accurate kinetic modelling in dynamic PET-MRI is emphasized.This article is part of the theme issue ‘Synergistic tomographic image reconstruction: part 2’.

On the descending connections of the visual hillock

At present, it seems more or less established the interruption of the fibers of the loop layer in the visual hillock. This proves the anatomical aspect of the relationship of visual hillocks to the sensitivity function, which is confirmed by both the newest pathological observations, especially Dejerine's, and experimental work. But the same cannot be said about the centrifugal connections of the visual hillock, which until now have remained little understood, despite the fact that the meaning of visual hillocks as centers of involuntary movements (mimic and movements of internal organs) was proved for the first time by me, and after that the authors in a whole series of experiments and observations. Some authors, like Probst, even deny completely on the basis of their research the existence of descending connections of the visual hillock, although it is absolutely impossible to agree already in the form of experimental data, which put outside doubt not only the sensitive, but also the motor function of the vision.

Technical Note: Cumulative dose modeling for organ motion management in MRI-guided radiation therapy.

To develop a method for continuous online dose accumulation during irradiation in MRI-guided radiation therapy (MRgRT) and to demonstrate its application in evaluating the impact of internal organ motion on cumulative dose. An intensity-modulated radiation therapy (IMRT) treatment plan is partitioned into its unique apertures. Dose for each planned aperture is calculated using Monte Carlo dose simulation on each phase of a four-dimensional computed tomography (4D-CT) dataset. Deformable image registration is then performed both (a) between each frame of a cine-MRI acquisition obtained during treatment and a reference frame, and (b) between each volume of the 4D-CT phases and a reference phase. These registrations are used to associate each cine image with a 4D-CT phase. Additionally, for each 4D-CT phase, the deformation vector field (DVF) is used to warp the pre-calculated dose volumes per aperture onto the reference CT dataset. To estimate the dose volume delivered during each frame of the cine-MRI acquisition, we retrieve the pre-calculated warped dose volume for the delivered aperture on the associated 4D-CT phase and adjust it by a rigid translation to account for baseline drift and instances where motion on the cine image exceeds the amplitude observed between 4D-CT phases. The proposed dose accumulation method is retrospectively applied to a liver cancer case previously treated on an MRgRT platform. Cumulative dose estimated for free-breathing and respiration-gated delivery is compared against dose calculated on static anatomy. In this sample case, the target minimum dose and varied by as much as 5% and 7%, respectively. We demonstrate a technique suitable for continuous online dose accumulation during MRgRT. In contrast to other approaches, dose is pre-calculated per aperture and phase and then retrieved based on a mapping scheme between cine MRI and 4D-CT datasets, aiming at reducing the computational burden for potential real-time applications.

Pelvic organ motion and dosimetric implications during horizontal patient rotation for prostate radiation therapy.

Gantry-free radiation therapy systems utilizing patient rotation would be simpler and more cost effective than the conventional gantry-based systems. Such a system could enable the expansion of radiation therapy to meet global demand and reduce capital costs. Recent advances in adaptive radiation therapy could potentially be applied to correct for gravitational deformation during horizontal patient rotation. This study aims to quantify the pelvic organ motion and the dosimetric implications of horizontal rotation for prostate intensity-modulated radiation therapy (IMRT) treatments. Eight human participants who previously received prostate radiation therapy were imaged in a clinical magnetic resonance imaging (MRI) scanner using a bespoke patient rotation system (PRS). The patients were imaged every 45 degrees during a full roll rotation (0-360 degrees). Whole pelvic bone, prostate, rectum, and bladder motion were compared to the supine position using dice similarity coefficient (DSC) and mean absolute surface distance (MASD). Prostate centroid motion was compared in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) direction prior to and following pelvic bone-guided rigid registration. Seven-field prostate IMRT treatment plans were generated for each patient rotation angles under three adaption scenarios: No plan adaption, rigid planning target volume (PTV)-guided alignment to the prostate, and plan re-optimization. Prostate, rectum, and bladder doses were compared for each adaption scenario. Pelvic bone motion within the PRS of up to 53mm relative to the supine position was observed for some participants. Internal organ motion was greatest at the 180-degree PRS couch angle (prone), with prostate centroid motion range<2mm LR, 0mm to 14mm SI, and -11mm to 4mm AP. Rotation with no adaption of the treatment plan resulted in an underdose to the PTV -- in some instances up to 75% (D95%: 78±0.3Gy at supine to 20±15.0Gy at the 225-degree PRS couch angle). Bladder dose was reduced during the rotation by up to 98% (V60Gy: 15.0±9.4% supine to 0.3±0.5% at the 225-degree PRS couch angle). In some instances, the rectum dose increased during rotation (V60Gy: 20.0±4.5% supine to 25.0±15.0% at the 135-degree PRS couch angle). Rigid PTV-guided alignment resulted in PTV coverage which, though statistically lower (P<0.05 for all D95% values), was within 1Gy of the supine plans. Plan re-optimization resulted in a statistically equivalent PTV coverage compared to the supine plans (P>0.05 for all D95% metrics and all within ±0.4Gy). For both rigid PTV-guided alignment and plan re-optimization, rectum dose volume metrics were reduced compared to the supine position between the 90- and 225-degree PRS couch angles (P<0.05). Bladder dose volume metrics were not impacted by rotation. Pelvic bone and internal organ motion are present during patient rotation. Rigid PTV-guided alignment to the prostate will be a requirement if prostate IMRT is to be safely delivered using patient rotation. Plan re-optimization for each PRS couch angle to account for anatomical deformations further improves the PTV coverage.

Analysis of Correlation Between Breast Surface Position and Internal Organ Deformation Using Deep-Inspiration Breath Holding for Left-Sided Breast Irradiation

An increased risk of cardiac toxicity and radiation pneumonitis is related to the mean dose of radiation to the heart and lungs during left-sided breast irradiation. The deep-inspiration breath holding (DIBH) technique was investigated with focus on reducing the radiation dose to the heart and its substructures, such as the left anterior descending coronary artery (LAD). Three-dimensional surface-imaging systems have been used to facilitate image-guided breast radiotherapy. However, internal organ position during DIBH depends on the compliance of the patient. Previous research has shown that relative craniocaudal distance changes during inspiration and expiration normalized to the mean distance in quiet breathing was maximum 44.3% ± 4% and minimum 4% ± 5%. We investigated positional correlations between limited breast surface position and internal organs and evaluated the effect of doses in left-sided breast irradiation with the DIBH technique. In this study, breast surface position was measured using an infrared range finder and the heart position was retrospectively measured using CT data. Five patients who had undergone left-sided lumpectomy practiced DIBH during CT. Simultaneously, breast surface distance (BSD) was monitored by a range finder continually during CT acquisition. The range finder was attached to the CT couch and measured the distance from one point of the breast surface to the scanner. CT with voluntary DIBH and free breathing in the treatment position was performed three times in each patient. To measure heart distances (HD), the maximum distance from the LAD to the chest wall (lateral edge of the lung) was calculated in each CT image and associated with the location to the corresponding BSD. Each free-breathing CT image was deformed to each DIBH CT image, and the deformation vector field (DVF), which was associated with the HD and the BSD, was calculated. Moreover, we evaluated dosimetric effects of variations of internal organ deformation by the voluntary DIBH. Compared with the mean BSD during free breathing, mean BSD during DIBH was reduced by 12 mm and the reproducibility was shown to be stable at approximately ± 0.2～3.9 mm. The mean HD was increased by 5.4 ± 2.4 mm. The correlation coefficient between BSD and HD during DIBH was 0.23, which indicated a weak positive correlation. According to the results of DVF, the heart and diaphragm positions moved forward toward the front caudal side; however, the variation in HD and internal organ motion depended on the characteristics of each patient. Moreover, in cases of abdominal breathing, breast surface motion was significantly small and no correlation between BSD and HD was observed. However, dosimetric errors of target and normal tissue were small, suggesting that DIBH irradiation while monitoring BSD is feasible. Correlations among BSD, HD, and internal organ motion were weak and depended on patient characteristics and respiratory method.

Triboelectric nanogenerator for healthcare and biomedical applications

• A summarized view of the fundamentals of the triboelectric nanogenerator (TENG) is presented. • Promising applications in different biomedical and healthcare sectors are discussed in detail. • Future perspectives and challenges for the commercialization of TENG based healthcare devices are provided. Triboelectric nanogenerator (TENG) can convert various types of mechanical energy into electricity via coupling of contact electrification and electrostatic induction. The wide range of materials, device designs, high output power are few of the TENG advantages. The human body and internal organ motions can serve as an excellent energy source for TENG based self-powered healthcare applications. This review highlights the past 7-year development in TENG based biomedical and healthcare devices. A summary of TENG applications, including drug delivery, neural prosthesis, cell modulation, circulatory system, microbial disinfection, gene transfection, hair regeneration, biodegradable electronics, is presented. However, miniaturization, long-term stability, encapsulation, and in-vivo performance are the challenges that need to be addressed before any clinical trials. In the future, overcoming the problems will make TENG as an alternative power source for the biomedical and healthcare applications.

Reliability of strain elastography using in vivo compression in the assessment of the uterine cervix during pregnancy.

Objective To determine the reproducibility of the mean strain value in various cervical areas and new elastographic parameters for measuring cervical stiffness evaluated by strain elastography using in vivo compression generated by internal organ movement. Methods A prospective observational study (140 singleton pregnant women; 15-33 weeks of gestation) was performed at two tertiary centers. Cervical strain was evaluated using E-cervix™ elastography. The mean strain levels of various cervical areas [internal os (IOS), external os (EOS) and endocervical area] and several new parameters [i.e. the ratio of the strain level of IOS and EOS, elasticity contrast index (ECI), and hardness ratio] were assessed twice by two independent examiners. The inter-observer and intra-observer variances were calculated using the intraclass correlation coefficient (ICC) with a 95% confidence interval (CI). Bland-Altman (B-A) analysis was also performed. Results The median gestational age was 24.0 weeks, and the mean cervical length (CL) was 3.8 cm. The intra-observer and inter-observer ICCs of the mean strain levels of the specified cervical area and new elastographic parameters were statistically significant (P < 0.001, all); the intra-observer ICC was 0.639-0.725, and the inter-observer ICC was 0.538-0.718. Conclusion The reproducibility of elastographic parameter measurements using in vivo compression is improvable.

Accelerated Dynamic Magnetic Resonance Imaging Using Learned Representations: A New Frontier in Biomedical Imaging

Dynamic magnetic resonance imaging (MRI) can be used to scan a wide range of dynamic processes within the body, including the motion of internal organs, tissue-level nuclear magnetic resonance (NMR) relaxation, and dynamic contrast enhancement (DCE) of dye agents. The ability of MRI to safely provide unique soft-tissue contrast and comprehensive functional information has made dynamic MRI central to a number of imaging exams for cardiac, interventional, vocal tract, cancer, and gastrointestinal applications, among others. Unfortunately, MRI is a notoriously slow imaging modality due to fundamental physical and physiological limitations. These limitations result in tradeoffs between spatial and temporal resolutions, spatial coverage, and the signal-to-noise ratio and have made dynamic MRI a challenging technical goal.

MR-MOTUS: model-based non-rigid motion estimation for MR-guided radiotherapy using a reference image and minimal k-space data

Time-resolved motion estimation from MRI data has received an increasing amount of interest due to the advent of the MR-Linac. The combination of an MRI scanner and a linear accelerator enables radiation plan adaptation based on internal organ motion estimated from MRI data. However, time-resolved estimation of this motion from MRI data still remains a challenge. In light of this application, we propose MR-MOTUS, a framework to estimate non-rigid 3D motion from minimal k-space data. MR-MOTUS consists of two main components: (1) a signal model that explicitly relates the k-space signal of a deforming object to non-rigid motion-fields and a reference image, and (2) model-based reconstructions of the non-rigid motion-fields directly from k-space data. Using an a priori available reference image and the fact that internal body motion exhibits a high level of spatial correlation, we represent the motion-fields in a low-dimensional space and reconstruct them from minimal k-space data that can be acquired very rapidly. The signal model is validated through numerical experiments with a digital 3D phantom and motion-fields are reconstructed from retrospectively undersampled in vivo head and abdomen data using various undersampling strategies. A comparison is made with state-of-the-art image registration performed on images reconstructed from the same undersampled data. Results show that MR-MOTUS reconstructs in vivo 3D rigid head motion from 474-fold retrospectively downsampled k-space data, and in vivo non-rigid 3D respiratory motion from 63-fold retrospectively undersampled k-space data. Preliminary results on prospectively undersampled data acquired with a 2D golden angle acquisition during free-breathing demonstrate the practical feasibility of the method.

The importance of mesorectum motion in determining PTV margins in rectal cancer patients treated with neoadjuvant radiotherapy.

New precision radiotherapy (RT) techniques reduce the uncertainties in localizing soft and moving tumors. However, there are still many uncontrollable internal organ movements. In our study, patients who underwent neoadjuvant chemoradiotherapy (NA-CRT) for rectal cancer were evaluated to determine inter-fraction mesorectum motion and dosimetric changes. Fourteen patients treated with NA-CRT for rectal cancer between 2014 and 2016 were included in the analysis. The mesorectum and clinical target volume (CTV) were delineated on planning computed tomography (CT) and cone-beam CT (CB-CT) scans. After planning with a volumetric modulated arc therapy (VMAT) plan, re-planning was performed on all CB-CTs. Finally, the volumetric and dosimetric changes of PTV and mesorectum were evaluated in all CB-CTs compared with the initial CT and VMAT plans. The geometrical center of mesorectum volume in CB-CTs had moved 1 (0.2–6.6), 1.6 (0.2–3.8) and 1.6 (0–4.9) mm in the x, y and z-axis respectively compared with the initial CT. The dosimetric parameters of PTV including D2, D95 and D98 on CB-CT showed a median 47.19 (46.70–47.80), 45.05 (44.18–45.68) and 44.69 (43.83–45.48) Gy and median 1% (1–2), 0% (0–2) and 1% (0–2) dosimetric change compared with the initial VMAT plan. In our study, we have shown that the mesorectum has moved up to 20 mm in the lateral and anterior–posterior direction and almost 10 mm in the superior/inferior direction during RT, causing a median of ~2% change in dosimetric parameters. Therefore, these movements must be considered in determining PTV margins to avoid dosimetric changes.