Dr Nguyen is an early career researcher and lecturer in Biomedical Engineering at University Technology Sydney (UTS). She currently holds an Australian National Health and Medical Research Council (NHMRC) fellowship, a Cancer Institute New South Wales Fellowship and a Cancer Australia grant, totalling $1.2M in funding. Dr Nguyen is instrumental as the lead technology developer in two multi-institutional radiotherapy clinical trials: TROG 15.01 SPARK trial and TROG 17.03 LARK trial.
Since joining the ACRF Image-X Institute in late 2015, Dr Nguyen has authored and co-authored 15 high impact research papers in the field of medical physics. Her scientific career to date produced more than 20 journals in total with an i-index of 7 (Google Scholar). Two articles were mentioned in the editorials of Radiotherapy and Oncology and became the featured articles of their issues. In the past 3 years, Dr Nguyen has authored and contributed to >20 abstracts at AAPM Annual Meetings, with the majority being oral presentations.
Currently, Dr Nguyen leads the real-time tumour tracking division within the Image-X Institute and UTS, innovating biomedical engineering technologies to improve cancer targeting accuracy and translating her research to improve patient care practice. Her collaborators include international partners such as the Aarhus University Hospital and Memorial Sloan Kettering Cancer Centre, and domestic clinical partners such Northern Sydney Cancer Care Centre, Westmead Hospital and Peter MacCallum Cancer Centre.
Member of the American Association of Physicists in Medicine.
Member of the European Society of Radiation Oncology
Member of the Trans-Tasman Radiation Oncology Group
Can supervise: YES
- Real-time X-ray imaging
- Real-time beam adaptation
- Radiation Oncology
- Biomedical instrumentation design
- Biomedical signal processing
- Medical Imaging
- Biomedical instrumentation
- Biomedical signal processing
- Biomedical imaging
- Deep learning in medical imaging
Alnaghy, S, Kyme, A, Caillet, V, Doan, TN, O'Brien, R, Booth, JT & Keall, PJ 2019, 'A six-degree-of-freedom robotic motion system for quality assurance of real-time image-guided radiotherapy', PHYSICS IN MEDICINE AND BIOLOGY, vol. 64, no. 10.View/Download from: UTS OPUS or Publisher's site
Hewson, EA, Nguyen, DT, O’Brien, R, Kim, JH, Montanaro, T, Moodie, T, Greer, PB, Hardcastle, N, Eade, T, Kneebone, A, Hruby, G, Hayden, AJ, Turner, S, Siva, S, Tai, KH, Hunter, P, Sams, J, Poulsen, PR, Booth, JT, Martin, J & Keall, PJ 2019, 'The accuracy and precision of the KIM motion monitoring system used in the multi-institutional TROG 15.01 Stereotactic Prostate Ablative Radiotherapy with KIM (SPARK) trial', Medical Physics, vol. 46, no. 11, pp. 4725-4737.View/Download from: Publisher's site
© 2019 American Association of Physicists in Medicine Purpose: Kilovoltage intrafraction monitoring (KIM) allows for real-time image guidance for tracking tumor motion in six-degrees-of-freedom (6DoF) on a standard linear accelerator. This study assessed the geometric accuracy and precision of KIM used to guide patient treatments in the TROG 15.01 multi-institutional Stereotactic Prostate Ablative Radiotherapy with KIM trial and investigated factors affecting accuracy and precision. Methods: Fractions from 44 patients with prostate cancer treated using KIM-guided SBRT were analyzed across four institutions, on two different linear accelerator models and two different beam models (6 MV and 10 MV FFF). The geometric accuracy and precision of KIM was assessed from over 33 000 images (translation) and over 9000 images (rotation) by comparing the real-time measured motion to retrospective kV/MV triangulation. Factors potentially affecting accuracy, including contrast-to-noise ratio (CNR) of kV images and incorrect marker segmentation, were also investigated. Results: The geometric accuracy and precision did not depend on treatment institution, beam model or motion magnitude, but was correlated with gantry angle. The centroid geometric accuracy and precision of the KIM system for SABR prostate treatments was 0.0 ± 0.5, 0.0 ± 0.4 and 0.1 ± 0.3 mm for translation, and −0.1 ± 0.6°, −0.1 ± 1.4° and −0.1 ± 1.0° for rotation in the AP, LR and SI directions respectively. Centroid geometric error exceeded 2 mm for 0.05% of this dataset. No significant relationship was found between large geometric error and CNR or marker segmentation correlation. Conclusions: This study demonstrated the ability of KIM to locate the prostate with accuracy below other uncertainties in radiotherapy treatments, and the feasibility for KIM to be implemented across multiple institutions.
Keall, PJ, Nguyen, DT, O'Brien, R, Zhang, P, Bertholet, J & Poulsen, PR 2019, 'In Reply to Dahele and Verbakel', International Journal of Radiation Oncology Biology Physics, vol. 103, no. 1, pp. 283-284.View/Download from: UTS OPUS or Publisher's site
Mylonas, A, Keall, PJ, Booth, JT, Shieh, C-C, Eade, T, Poulsen, PR & Doan, TN 2019, 'A deep learning framework for automatic detection of arbitrarily shaped fiducial markers in intrafraction fluoroscopic images', MEDICAL PHYSICS, vol. 46, no. 5, pp. 2286-2297.View/Download from: UTS OPUS or Publisher's site
Wolf, J, Nicholls, J, Hunter, P, Nguyen, DT, Keall, P & Martin, J 2019, 'Dosimetric impact of intrafraction rotations in stereotactic prostate radiotherapy: A subset analysis of the TROG 15.01 SPARK trial.', Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, vol. 136, pp. 143-147.View/Download from: UTS OPUS or Publisher's site
BACKGROUND AND PURPOSE:Accurate delivery of radiotherapy is critical to achieve optimal treatment outcomes. Interfraction translational IGRT is now standard, and intrafraction motion management is becoming accessible. Some platforms can report both translational and rotational movements in real time. This study aims to quantify the dosimetric impact of observed intrafraction rotation of the prostate measured using monitoring software. MATERIALS AND METHODS:A dose grid resampling algorithm was used to model the dosimetric impact of prostate rotations for 20 patients on a SBRT prostate clinical trial. Translations were corrected before and during treatment, but rotations were not. Real time rotation data were acquired using KIM and a cumulative histogram analysis performed. Prostate volumes were rotated by the range of observed angles and used to calculate DVH data. RESULTS:The pitch axis had a higher range of observed rotations resulting in only 7 patients spending at least 90% of the beam on time across all fractions within rotation angles resulting in PTV D95% ≥36 Gy in this axis. The yaw and roll axes saw 17 and 15 patients respectively achieving this criterion. All but one of 20 patients exceeded CTV D98% ≥36 Gy for all observed rotation angles. CONCLUSIONS:Current CTV-PTV margins do not result in compromised CTV dose coverage due to inter and intrafraction prostate rotations in the absence of other uncertainties. Reduced PTV dosing is due to the extremely conformal treatment delivery but is unlikely to be clinically deleterious. Prostate standard IGRT should continue to focus on correcting any observed translational movements. Margin reduction could be explored in conjunction with other uncertainties.
Keall, PJ, Doan, TN, O'Brien, R, Caillet, V, Hewson, E, Poulsen, PR, Bromley, R, Bell, L, Eade, T, Kneebone, A, Martin, J & Booth, JT 2018, 'The first clinical implementation of real-time image-guided adaptive radiotherapy using a standard linear accelerator', RADIOTHERAPY AND ONCOLOGY, vol. 127, no. 1, pp. 6-11.View/Download from: UTS OPUS or Publisher's site
Keall, PJ, Doan, TN, O'Brien, R, Zhang, P, Happersett, L, Bertholet, J & Poulsen, PR 2018, 'Review of Real-Time 3-Dimensional Image Guided Radiation Therapy on Standard-Equipped Cancer Radiation Therapy Systems: Are We at the Tipping Point for the Era of Real-Time Radiation Therapy?', INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, vol. 102, no. 4, pp. 922-931.View/Download from: Publisher's site
Kim, J-H, Nguyen, DT, Booth, JT, Huang, C-Y, Fuangrod, T, Poulsen, P, O'Brien, R, Caillet, V, Eade, T, Kneebone, A & Keall, P 2018, 'The accuracy and precision of Kilovoltage Intrafraction Monitoring (KIM) six degree-of-freedom prostate motion measurements during patient treatments.', Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, vol. 126, no. 2, pp. 236-243.View/Download from: UTS OPUS or Publisher's site
BACKGROUND AND PURPOSE:To perform a quantitative analysis of the accuracy and precision of Kilovoltage Intrafraction Monitoring (KIM) six degree-of-freedom (6DoF) prostate motion measurements during treatments. MATERIAL AND METHODS:Real-time 6DoF prostate motion was acquired using KIM for 14 prostate cancer patients (377 fractions). KIM outputs the 6DoF prostate motion, combining 3D translation and 3D rotational motion information relative to its planning position. The corresponding groundtruth target motion was obtained post-treatment based on kV/MV triangulation. The accuracy and precision of the 6DoF KIM motion estimates were calculated as the mean and standard deviation differences compared with the ground-truth. RESULTS:The accuracy ± precision of real-time 6DoF KIM-measured prostate motion were 0.2 ± 1.3° for rotations and 0.1 ± 0.5 mm for translations, respectively. The magnitude of KIM-measured motion was well-correlated with the magnitude of ground-truth motion resulting in Pearson correlation coefficients of ≥0.88 in all DoF. CONCLUSIONS:The results demonstrate that KIM is capable of providing the real-time 6DoF prostate target motion during patient treatments with an accuracy ± precision of within 0.2 ± 1.3° and 0.1 ± 0.5 mm for rotation and translation, respectively. As KIM only requires a single X-ray imager, which is available on most modern cancer radiotherapy devices, there is potential for widespread adoption of this technology.
Liu, PZY, Nguyen, DT, Feain, I, O'Brien, R, Keall, PJ & Booth, JT 2018, 'Technical Note: Real-time image-guided adaptive radiotherapy of a rigid target for a prototype fixed beam radiotherapy system.', Medical physics, vol. 45, no. 10, pp. 4660-4666.View/Download from: UTS OPUS or Publisher's site
PURPOSE:Fixed beam radiotherapy systems utilize couch movement and rotation instead of gantry rotation in order to simplify linear accelerator design. We investigate the ability to deliver fixed beam treatments with the same level of clinical accuracy as conventional (rotating beam) treatments using real-time image guidance to maintain this accuracy in the presence of rigid target motion. METHODS:A prototype fixed beam radiotherapy system was built using a standard linac with the beam fixed in the vertical position and a computer controlled rotation stage that rotated a rigid phantom about the superior-inferior axis. Kilovoltage Intrafraction Monitoring (KIM) and real-time beam adaptation with MLC tracking was applied to a five-field IMRT treatment plan with motion introduced to the phantom. The same IMRT treatment was also delivered with real-time adaptation using the conventional rotating beam geometry. Film dosimetry was used to measure the dose delivered with a fixed beam compared to a rotating beam, as well as to compare treatments delivered with and without real-time adaptation. RESULTS:The dose distributions were found to be equivalent between the fixed beam and rotating beam geometry for real-time adaptive radiotherapy using KIM and MLC tracking beam adaptation. Gamma analysis on the films showed agreement >98% using a 2%/2 mm criteria with adaptation for static shifts and periodic motion. CONCLUSIONS:Fixed beam treatments with real-time beam adaptation are dosimetrically equivalent to conventional treatments with a rotating beam, even in the presence of rigid target motion. This suggests that, for a rigid target, the high clinical accuracy of real-time adaptive radiotherapy can be achieved with simpler beam geometry.
Montanaro, T, Nguyen, DT, Keall, PJ, Booth, J, Caillet, V, Eade, T, Haddad, C & Shieh, C-C 2018, 'A comparison of gantry-mounted x-ray-based real-time target tracking methods.', Medical physics, vol. 45, no. 3, pp. 1222-1232.View/Download from: UTS OPUS or Publisher's site
Most modern radiotherapy machines are built with a 2D kV imaging system. Combining this imaging system with a 2D-3D inference method would allow for a ready-made option for real-time 3D tumor tracking. This work investigates and compares the accuracy of four existing 2D-3D inference methods using both motion traces inferred from external surrogates and measured internally from implanted beacons.Tumor motion data from 160 fractions (46 thoracic/abdominal patients) of Synchrony traces (inferred traces), and 28 fractions (7 lung patients) of Calypso traces (internal traces) from the LIGHT SABR trial (NCT02514512) were used in this study. The motion traces were used as the ground truth. The ground truth trajectories were used in silico to generate 2D positions projected on the kV detector. These 2D traces were then passed to the 2D-3D inference methods: interdimensional correlation, Gaussian probability density function (PDF), arbitrary-shape PDF, and the Kalman filter. The inferred 3D positions were compared with the ground truth to determine tracking errors. The relationships between tracking error and motion magnitude, interdimensional correlation, and breathing periodicity index (BPI) were also investigated.Larger tracking errors were observed from the Calypso traces, with RMS and 95th percentile 3D errors of 0.84-1.25 mm and 1.72-2.64 mm, compared to 0.45-0.68 mm and 0.74-1.13 mm from the Synchrony traces. The Gaussian PDF method was found to be the most accurate, followed by the Kalman filter, the interdimensional correlation method, and the arbitrary-shape PDF method. Tracking error was found to strongly and positively correlate with motion magnitude for both the Synchrony and Calypso traces and for all four methods. Interdimensional correlation and BPI were found to negatively correlate with tracking error only for the Synchrony traces. The Synchrony traces exhibited higher interdimensional correlation than the Calypso traces especially in the anterior-poster...
Nguyen, DT, Booth, JT, Caillet, V, Hardcastle, N, Briggs, A, Haddad, C, Eade, T, O'Brien, R & Keall, PJ 2018, 'An augmented correlation framework for the estimation of tumour translational and rotational motion during external beam radiotherapy treatments using intermittent monoscopic x-ray imaging and an external respiratory signal.', Physics in medicine and biology, vol. 63, no. 20, pp. 205003-205003.View/Download from: UTS OPUS or Publisher's site
Increasing evidence shows that intrafraction tumour motion monitoring must include both six degrees of freedom (6DoF): 3D translations and 3D rotations. Existing real-time algorithms for 6DoF target motion estimation require continuous intrafraction fluoroscopic imaging at high frequency, thereby exposing patients to additional high imaging dose. This paper presents the first method capable of 6DoF motion monitoring using intermittent 2D kV imaging and a continuous external respiratory signal. Our approach is to optimise a state-augmented linear correlation model between an external signal and internal 6DoF motion. In standard treatments, the model can be built using information obtained during pre-treatment cone beam CT (CBCT). Real-time 6DoF tumor motion can then be estimated using just the external signal. Intermittent intrafraction kV images are used to update the model parameters, accounting for changes in correlation and baseline shifts. The method was evaluated in silico using data from 6 lung SABR patients, with the internal tumour motion recorded with electromagnetic beacons and the external signal from a bellows belt. Projection images from CBCT (10 Hz) and intermittent kV images were simulated by projecting the 3D Calypso beacon positions onto an imager. IMRT and VMAT treatments were simulated with increasing imaging update intervals: 0.1 s, 1 s, 3 s, 10 s and 30 s. For all the tested clinical scenarios, translational motion estimates with our method had sub-mm accuracy (mean) and precision (standard deviation) while rotational motion estimates were accurate to <[Formula: see text] and precise to [Formula: see text]. Motion estimation errors increased as the imaging update interval increased. With the largest imaging update interval (30 s), the errors were [Formula: see text] mm, [Formula: see text] mm and [Formula: see text] mm for translation in the left-right, superior-inferior and anterior-posterior directions, respectively, and [Formula: see text...
Keall, P, Doan, TN, O'Brien, R, Booth, J, Greer, P, Poulsen, P, Gebski, V, Kneebone, A & Martin, J 2017, 'Stereotactic prostate adaptive radiotherapy utilising kilovoltage intrafraction monitoring: the TROG 15.01 SPARK trial', BMC CANCER, vol. 17.View/Download from: Publisher's site
Kim, J-H, Nguyen, DT, Huang, C-Y, Fuangrod, T, Caillet, V, O'Brien, R, Poulsen, P, Booth, J & Keall, P 2017, 'Quantifying the accuracy and precision of a novel real-time 6 degree-of-freedom kilovoltage intrafraction monitoring (KIM) target tracking system', PHYSICS IN MEDICINE AND BIOLOGY, vol. 62, no. 14, pp. 5744-5759.View/Download from: Publisher's site
Legge, K, Doan, N, Ng, JA, Wilton, L, Richardson, M, Booth, J, Keall, P, O'Connor, DJ, Greer, P & Martin, J 2017, 'Real-time intrafraction prostate motion during linac based stereotactic radiotherapy with rectal displacement', JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, vol. 18, no. 6, pp. 130-136.View/Download from: Publisher's site
Legge, K, Greer, PB, Keall, PJ, Booth, JT, Arumugam, S, Moodie, T, Nguyen, DT, Martin, J, O'Connor, DJ & Lehmann, J 2017, 'Technical note: TROG 15.01 SPARK trial multi-institutional imaging dose measurement', Journal of Applied Clinical Medical Physics, vol. 18, no. 5, pp. 358-363.View/Download from: Publisher's site
© 2017 American Association of Physicists in Medicine. Purpose: The Trans-Tasman Radiation Oncology Group (TROG) 15.01 Stereotactic Prostate Adaptive Radiotherapy utilizing Kilovoltage intrafraction monitoring (SPARK) trial is a multicenter trial using Kilovoltage Intrafraction Monitoring (KIM) to monitor prostate position during the delivery of prostate radiation therapy. KIM increases the accuracy of prostate radiation therapy treatments and allows for hypofractionation. However, an additional imaging dose is delivered to the patient. A standardized procedure to determine the imaging dose per frame delivered using KIM was developed and applied at four radiation therapy centers on three different types of linear accelerator. Methods: Dose per frame for kilovoltage imaging in fluoroscopy mode was measured in air at isocenter using an ion chamber. Beam quality and dose were determined for a Varian Clinac iX linear accelerator, a Varian Trilogy, four Varian Truebeams and one Elekta Synergy at four different radiation therapy centers. The imaging parameters used on the Varian machines were 125 kV, 80 mA, and 13 ms. The Elekta machine was measured at 120 kV, 80 mA, and 12 ms. Absorbed doses to the skin and the prostate for a typical SBRT prostate treatment length were estimated according to the IPEMB protocol. Results: The average dose per kV frame to the skin was 0.24 ± 0.03 mGy. The average estimated absorbed dose to the prostate for all five treatment fractions across all machines measured was 39.9 ± 2.6 mGy for 1 Hz imaging, 199.7 ± 13.2 mGy for 5 Hz imaging and 439.3 ± 29.0 mGy for 11 Hz imaging. Conclusions: All machines measured agreed to within 20%. Additional dose to the prostate from using KIM is at most 1.3% of the prescribed dose of 36.25 Gy in five fractions delivered during the trial.
Nguyen, DT, Bertholet, J, Kim, J-H, O'Brien, R, Booth, JT, Poulsen, PR & Keall, PJ 2017, 'An interdimensional correlation framework for real-time estimation of six degree of freedom target motion using a single x-ray imager during radiotherapy.', Physics in medicine and biology, vol. 63, no. 1, pp. 015010-015010.View/Download from: UTS OPUS or Publisher's site
Increasing evidence suggests that intrafraction tumour motion monitoring needs to include both 3D translations and 3D rotations. Presently, methods to estimate the rotation motion require the 3D translation of the target to be known first. However, ideally, translation and rotation should be estimated concurrently. We present the first method to directly estimate six-degree-of-freedom (6DoF) motion from the target's projection on a single rotating x-ray imager in real-time. This novel method is based on the linear correlations between the superior-inferior translations and the motion in the other five degrees-of-freedom. The accuracy of the method was evaluated in silico with 81 liver tumour motion traces from 19 patients with three implanted markers. The ground-truth motion was estimated using the current gold standard method where each marker's 3D position was first estimated using a Gaussian probability method, and the 6DoF motion was then estimated from the 3D positions using an iterative method. The 3D position of each marker was projected onto a gantry-mounted imager with an imaging rate of 11 Hz. After an initial 110° gantry rotation (200 images), a correlation model between the superior-inferior translations and the five other DoFs was built using a least square method. The correlation model was then updated after each subsequent frame to estimate 6DoF motion in real-time. The proposed algorithm had an accuracy (±precision) of -0.03 ± 0.32 mm, -0.01 ± 0.13 mm and 0.03 ± 0.52 mm for translations in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions respectively; and, 0.07 ± 1.18°, 0.07 ± 1.00° and 0.06 ± 1.32° for rotations around the LR, SI and AP axes respectively on the dataset. The first method to directly estimate real-time 6DoF target motion from segmented marker positions on a 2D imager was devised. The algorithm was evaluated using 81 motion traces from 19 liver patients and was found to have sub-mm and ...
Nguyen, DT, O'Brien, R, Kim, J-H, Huang, C-Y, Wilton, L, Greer, P, Legge, K, Booth, JT, Poulsen, PR, Martin, J & Keall, PJ 2017, 'The first clinical implementation of a real-time six degree of freedom target tracking system during radiation therapy based on Kilovoltage Intrafraction Monitoring (KIM)', RADIOTHERAPY AND ONCOLOGY, vol. 123, no. 1, pp. 37-42.View/Download from: Publisher's site
Sadr, N, Huvanandana, J, Doan, TN, Kalra, C, McEwan, A & de Chazal, P 2016, 'Reducing false arrhythmia alarms in the ICU using multimodal signals and robust QRS detection', PHYSIOLOGICAL MEASUREMENT, vol. 37, no. 8, pp. 1340-1354.View/Download from: Publisher's site
Bhaskaran, A, Barry, MAT, Al Raisi, SI, Chik, W, Doan, TN, Pouliopoulos, J, Nalliah, C, Hendricks, R, Thomas, S, McEwan, AL, Kovoor, P & Thiagalingam, A 2015, 'Magnetic guidance versus manual control: comparison of radiofrequency lesion dimensions and evaluation of the effect of heart wall motion in a myocardial phantom', JOURNAL OF INTERVENTIONAL CARDIAC ELECTROPHYSIOLOGY, vol. 44, no. 1, pp. 1-8.View/Download from: Publisher's site
Bhaskaran, A, Chik, W, Nalliah, C, Pouliopoulos, J, Barry, T, Doan, TN, Midekin, C, Samanta, R, Farraha, M, Thomas, S, Kovoor, P & Thiagalingam, A 2015, 'Observations on Attenuation of Local Electrogram Amplitude and Circuit Impedance During Atrial Radiofrequency Ablation: An In vivo Investigation Using a Novel Direct Endocardial Visualization Catheter', JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, vol. 26, no. 11, pp. 1250-1256.View/Download from: Publisher's site
Chik, WWB, Kosobrodov, R, Bhaskaran, A, Barry, MAT, Doan, TN, Pouliopoulos, J, Byth, K, Sivagangabalan, G, Thomas, SP, Ross, DL, Mcewan, A, Kovoor, P & Thiagalingam, A 2015, 'Acoustic Signal Emission Monitoring as a Novel Method to Predict Steam Pops During Radiofrequency Ablation: Preliminary Observations', JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, vol. 26, no. 4, pp. 440-447.View/Download from: Publisher's site
Gargiulo, GD, Cohen, G, McEwan, AL, Oh, TI, Mohamed, A, Tapson, J, Nguyen, DT, van Schaik, A & Wabnitz, A 2012, 'Active electrode design suitable for simultaneous EIT and EEG', ELECTRONICS LETTERS, vol. 48, no. 25.View/Download from: Publisher's site
Muurholm, CG, Ravkilde, T, Skouboe, S, Eade, T, Nguyen, DT, Booth, J, Keall, PJ & Poulsen, PR 2019, 'Dose reconstruction including dynamic six-degree of freedom motion during prostate radiotherapy', Journal of Physics: Conference Series.View/Download from: Publisher's site
© Published under licence by IOP Publishing Ltd. An in-house developed program for real-time reconstruction of motion-induced dose errors, DoseTracker, was extended to handle rotational target motion in addition to the previously implemented translational motion, and applied offline for prostate VMAT treatments. For translational motion, the motion-induced errors of DoseTracker were in good agreement with ground truth dose reconstructions performed in a commercial treatment planning system. For rotational motion, no ground truth was available, but DoseTracker showed that the VMAT dose is highly robust against static interfractional rotations but quite sensitive to dynamic intrafraction rotations due to interplay effects between target motion and machine motion.
Nguyen, DT, Bhaskaran, A, Chik, W, Barry, MA, Pouliopoulos, J, Kosobrodov, R, Jin, C, Oh, TI, Thiagalingam, A & McEwan, AL 2015, 'Perfusion redistribution after a pulmonary-embolism-like event with contrast enhanced EIT', PHYSIOLOGICAL MEASUREMENT, IOP PUBLISHING LTD, pp. 1297-1309.View/Download from: Publisher's site
Sadr, N, Huvanandana, J, Nguyen, DT, Kalra, C, McEwan, A & De Chazal, P 2015, 'Reducing false arrhythmia alarms in the ICU by Hilbert QRS detection', Computing in Cardiology, pp. 1173-1176.View/Download from: Publisher's site
© 2015 CCAL. In this study, we develop algorithms that reduce the arrhythmia false alarms in the ICU by processing the four signals of Photoplethysmography (PPG), arterial blood pressure (ABP), ECG Lead II, and Augmented right arm ECG. Our algorithms detect five arrhythmias including asystole, extreme bradycardia, extreme tachycardia, ventricular tachycardia (VT), and ventricular flutter or fibrillation (VF). Real time algorithm is provided. Our processing proceeded as follows. Firstly, preprocessing was applied to the ECG signals by two median filters in order to remove the baseline wander and high-frequency noise. Then a Hilbert-transform based QRS detector algorithm was used to detect R waves from the ECG signals. Following this, RR intervals were calculated from the available ECG signals. Pulse onset points of the pulsatile signals (PPG and ABP) were also detected and the signal quality index (SQI) of the four signals was measured. The ECG based RR intervals were combined with the pulsatile signal based RR intervals using the algorithms provided by the CinC2015 competition organizers. The combined RR intervals were thresholded at the clinically important values for the five arrhythmias. Template matching was used to detect ventricular tachycardia (VT) and power spectrum of ECG signals and identifYing the VF frequency components employed to investigate ventricular fibrillation. Our highest overall result was a 98% True Positive Rate (TPR), 66% True Negative Rate (TNR) with a score of 74.03% for the retrospective algorithm. For the realtime algorithm, we achieved a 98% TPR, 65% TNR and a score of 69.92%.
Doan, TN, Thiagalingam, A, Bhaskaran, A, Barry, MA, Pouliopoulos, J, Jin, C & McEwan, AL 2014, 'Electrical Impedance Tomography for Assessing Ventilation/Perfusion Mismatch for Pulmonary Embolism Detection without Interruptions in Respiration', 2014 36TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), 36th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC), IEEE, Chicago, IL, pp. 6068-6071.
Farraha, M, Nguyen, DT, Barry, MA, Lu, J, McEwan, AL & Pouliopoulos, J 2014, 'Investigating the utility of in vivo bio-impedance spectroscopy for the assessment of post-ischemic myocardial tissue', 2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC 2014, pp. 1111-1114.View/Download from: Publisher's site
© 2014 IEEE. Increased myocardial structural heterogeneity in response to ischemic injury following myocardial infarction (MI) is purported as the mechanism of ventricular arrhythmogenesis. Current modalities for in vivo assessment of structural heterogeneity for identification of arrhythmogenic substrate are limited due to the complex nature of the structural microenvironment post-MI. We investigated the utility of in vivo bio-impedance spectroscopy (BIS) in a large post-infarct animal model for differentiation between normal and infarcted tissue. We also investigated the quantitative effects of adipose and collagen on BIS assessment of myocardium. The results indicate that the degree of myocardial injury following chronic post-infarction remodeling could be reliably quantified (performed in triplicates) using BIS. Furthermore, the presence of intramyocardial adipose tissue that develops in conjunction with collagen within the infarct zone had a greater and significant influence on BIS then collagen tissue alone. These preliminary results indicate a potential role of BIS for quantitative assessment and characterization of complex arrhythmogenic substrates in ischemic cardiomyopathy.
McEwan, A, Wi, H, Nguyen, DT, Jones, P, Lam, V, Hawthorne, WJ, Barry, MA & Oh, TI 2014, 'Development of electrical impedance tomography of microwave ablation', Proceedings of SPIE - The International Society for Optical Engineering.View/Download from: Publisher's site
In this study we assess the feasibility of electrical impedance tomography (EIT) to track the temperature changes during ablation in an ex-vivo ovine liver and in-vivo porcine model. 208 tetrapolar electrical impedance measurements were obtained at 30 frame/s from a 16 electrode EIT system. In the porcine model ventilation artefact was removed by low pass filtering and successful ablation related impedance change image sequences were reconstructed from four of nine liver ablations. This study indicates feasibility of the technique but was limited in the porcine model due to electrode difficulties and the difficulty in positioning the microwave applicator under ultrasound. EIT is more convenient and lower cost than other temperature monitoring methods such as MRI but spatial resolution is constrained by the relatively low number of independent measurements and ill posed reconstruction problem. Future improvements include the use of an internal electrode that could be in practice located on the microwave applicator to provide the reconstruction algorithm with improved prior information and local information of conductivity changes due to ablation.
Nguyen, DT, Jin, C, Thiagalingam, A & McEwan, A 2013, 'A computer simulation study on the applicability of 3D electrical impedance tomography for pulmonary perfusion defect imaging', IFMBE Proceedings, pp. 967-970.View/Download from: Publisher's site
Electrical Impedance Tomography (EIT) has many advantages as a medical imaging modality. It is non-invasive, radiation-free and portable. This technique could be used for the diagnosis of pulmonary embolism, which up to now does no have a satisfactory solution. However, the current resolution of EIT is very low, rendering its sensitivity for perfusion defects not yet suitable for clinical application. This paper presents a simplified computer simulated model using 3D EIT to image the perfusion defects. A FEM mesh of 122 880 elements is used to solve the forward voltages using algorithms built-in to EIDORS, an open source software for EIT. The EIT system simulated has 4 rings of 16 electrodes, excited in adjacent patterns. The resulting voltage measurements with added white noise at 24 dB are reconstructed on a coarser mesh of 7680 elements. The results show that 3D EIT can image perfusion defects as small as 5% of a lung volume in the upper lung regions. Larger defects are observable from the reconstructed images in all regions of the lung. Although the study is simple and therefore suffers from several drawbacks, the results are encouraging for future application of this technique in perfusion defect imaging. © 2013 Springer-Verlag.
Nguyen, DT, Kosobrodov, R, Barry, MA, Chik, W, Jin, C, Oh, TI, Thiagalingam, A & McEwan, A 2013, 'Electrode-Skin contact impedance: In vivo measurements on an ovine model', XV INTERNATIONAL CONFERENCE ON ELECTRICAL BIO-IMPEDANCE (ICEBI) & XIV CONFERENCE ON ELECTRICAL IMPEDANCE TOMOGRAPHY (EIT), 15th International Conference on Electrical Bio-Impedance (ICEBI) / 14th Conference on Electrical Impedance Tomography (EIT), IOP PUBLISHING LTD, Inst Bioprozess & Analysenmesstechnik, Heilbad Heiligenstadt, GERMANY.View/Download from: Publisher's site
Nguyen, DT, Kosobrodov, R, Barry, MA, Chik, W, Pouliopoulos, J, Oh, TI, Thiagalingam, A & McEwan, A 2013, 'Preliminary Results on Different Impedance Contrast Agents for Pulmonary Perfusion Imaging with Electrical Impedance Tomography', XV INTERNATIONAL CONFERENCE ON ELECTRICAL BIO-IMPEDANCE (ICEBI) & XIV CONFERENCE ON ELECTRICAL IMPEDANCE TOMOGRAPHY (EIT), 15th International Conference on Electrical Bio-Impedance (ICEBI) / 14th Conference on Electrical Impedance Tomography (EIT), IOP PUBLISHING LTD, Inst Bioprozess & Analysenmesstechnik, Heilbad Heiligenstadt, GERMANY.View/Download from: Publisher's site
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