Anand P Santhanam

Anand P Santhanam
University of California, Los Angeles | UCLA · Department of Radiation Oncology

PhD

About

148
Publications
11,179
Reads
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1,094
Citations
Introduction
Anand P Santhanam currently works at the Department of Radiation Oncology, University of California, Los Angeles. Anand does research in Computer Graphics, Human-computer Interaction and Software Engineering. Their current project is focused on human organ motion and physiology modeling for normal, diseased and injured conditions.
Additional affiliations
July 2016 - present
University of California, Los Angeles
Position
  • Professor (Associate)
November 2010 - June 2016
University of California, Los Angeles
Position
  • Professor (Assistant)
August 2008 - November 2010
University of Central Florida
Position
  • Research faculty

Publications

Publications (148)
Conference Paper
This study investigates the effects of different pathological conditions of human trachea on flow distribution in the tracheo-bronchial tree (TBT) of human airways. Pathological conditions including hereditary Left Pulmonary Artery Sling (LPAS) and Chronic Obstructive Pulmonary Disease (COPD) often cause stenosis in the tracheal airway while a wide...
Article
Purpose: To examine the use of multiple fast-helical free breathing CT (FHFBCT) scans for ventilation measurement METHODS: Ten patients were scanned 25 times in alternating directions using a FHFBCT protocol. Simultaneously, an abdominal pneumatic bellows was used as a real-time breathing surrogate. Regions-of-interest (ROIs) were selected from th...
Article
Purpose: Fast helical free-breathing CT (FHFBCT) scans are widely used for 5DCT and 5D Cone Beam imaging protocols. For quantitative analysis of lung physiology and function, it is important to segment the lung lobes in these scans. Since the 5DCT protocols use up to 25 FHFBCT scans, it is important that this segmentation task be automated. In thi...
Article
PurposeComputational fluid dynamics (CFD) of lung airflow during normal and pathophysiological breathing provides insight into regional pulmonary ventilation. By integrating CFD methods with 4D lung imaging workflows, regions of normal pulmonary function can be spared during treatment planning. To facilitate the use of CFD simulations in a clinical...
Article
Purpose: To quantify the use of anterior torso skin surface position measurement as a breathing surrogate. Methods: Fourteen patients were scanned 25 times in alternating directions using a free-breathing low-mA fast helical CT protocol. Simultaneously, an abdominal pneumatic bellows was used as a real-time breathing surrogate. The imaged diaphr...
Article
Purpose: Lung biomechanical models are important for understanding and characterizing lung anatomy and physiology. A key parameter of biomechanical modeling is the underlying tissue elasticity distribution. While human lung elasticity estimations do not have ground truths, model consistency checks can and should be employed to gauge the stability...
Article
Lung elastography aims at measuring the lung parenchymal tissue elasticity for applications ranging from diagnostic purposes to biomechanically-guided deformations. Characterizing the lung tissue elasticity requires 4D lung motion as an input, which is currently estimated by deformably registering 4DCT datasets. Since 4DCT imaging is widely used on...
Article
Purpose: Elastography using CT is a promising methodology that can provide patient-specific regional distributions of lung biomechanical properties. The purpose of this paper is to investigate the feasibility of performing elastography using simulated lower dose CT scans. Methods: A cohort of 8 patient CT image pairs were acquired with a tube cu...
Conference Paper
Adaptive Radiotherapy(ART)is an effective procedure for the treatment of cancer. Technical complications and delays in retrieving, and registering on-board image datasets from the treatment system with the planning CT has rendered the ARTworkflow to be limited to a few patients. In this paper, we present an approach for improving the quality of the...
Article
Electron density maps must be accurately estimated to achieve valid dose calculation in MR-only radiotherapy. The goal of this study is to assess whether two deep learning models, the conditional generative adversarial network (cGAN) and the cycle-consistent generative adversarial network (cycleGAN), can generate accurate abdominal synthetic CT (sC...
Article
Purpose: To develop and demonstrate the efficacy of a novel head-and-neck multimodality image registration technique using deep-learning based cross-modality synthesis. Methods and materials: 25 head-and-neck patients received MR and CT (CTaligned ) scans on the same day with the same immobilization. 5-fold cross validation was used with all of...
Preprint
Electron density maps must be accurately estimated to achieve valid dose calculation in MR-only radiotherapy. The goal of this study is to assess whether two deep learning models, the conditional generative adversarial network (cGAN) and the cycle-consistent generative adversarial network (cycleGAN), can generate accurate abdominal synthetic CT (sC...
Article
Purpose: In-house software is commonly employed to implement new imaging and therapy techniques before commercial solutions are available. Risk analysis methods, as detailed in the TG-100 report of the American Association of Physicists in Medicine, provide a framework for quality management of processes but offer little guidance on software desig...
Article
Purpose To develop and evaluate a multishot diffusion‐prepared (DP) magnitude‐stabilized balanced steady‐state free precession (bSSFP) diffusion imaging sequence with improved geometric fidelity. Methods A signal spoiler (magnitude stabilizer; MS) was implemented in a DP‐bSSFP diffusion sequence. Effects of magnitude stabilizers with respect to ph...
Preprint
Full-text available
Augmented Reality (AR) systems add visual information to the world by using advanced display techniques. The advances in miniaturization and reduced costs make some of these systems feasible for applications in a wide set of fields. We present a potential component of the cyber infrastructure for the operating room of the future; a distributed AR b...
Article
Objectives:: Lung tissue elasticity is an effective spatial representation for Chronic Obstructive Pulmonary Disease phenotypes and pathophysiology. We investigated a novel imaging biomarker based on the voxel-by-voxel distribution of lung tissue elasticity. Our approach combines imaging and biomechanical modeling to characterize tissue elasticity...
Article
Liver diseases, such as liver cancer and cirrhosis, are commonly associated with changes in the biomechanical properties of liver tissue. Functional imaging techniques such as elastography have shown great promise in measuring the biomechanical properties of liver tissue; however, current liver elastography techniques require additional equipment t...
Article
Breathing motion modeling requires observation of tissues at sufficiently distinct respiratory states for proper 4D characterization. This work proposes a method to improve sampling of the breathing cycle with limited imaging dose. We designed and tested a prospective free-breathing acquisition protocol with a simulation using datasets from 5 pati...
Article
Purpose: Lung diseases are commonly associated with changes in lung tissue's biomechanical properties. Functional imaging techniques, such as elastography, have shown great promise in measuring tissue's biomechanical properties, which could expand the utility and effectiveness of radiotherapy treatment planning. We present a novel methodology for...
Article
Objective: To evaluate variations in intra- and inter-fractional tumor motion, and the effect on ITV contour accuracy, using deformable image registration of real-time 2D-sagital cine-mode MRI acquired during lung SBRT treatments. Methods: Five lung tumor patients underwent free breathing SBRT treatments on the ViewRay system, with dose prescrib...
Article
A biomechanical model of human lung is developed and used to investigate the effect of gravity on lung deformation. The lung is assumed to behave as a poro-elastic medium with spatially dependent elastic property. Finite element analysis is performed on a three-dimensional (3D) lung geometry reconstructed from a four-dimensional Computed Tomography...
Article
Purpose A critical step in adaptive radiotherapy (ART) workflow is deformably registering the simulation CT with the daily or weekly volumetric imaging. Quantifying the deformable image registration accuracy under these circumstances is a complex task due to the lack of known ground-truth landmark correspondences between the source data and target...
Article
A tandem of particle-based computational methods is adapted to simulate injury and hemorrhage in the human body. In order to ensure anatomical fidelity, a three-dimensional model of a targeted portion of the human body is reconstructed from a dense sequence of CT scans of an anonymized patient. Skin, bone and muscular tissue are distinguished in th...
Article
PurposeIn this paper, a multi-GPU cloud-based server (MGCS) framework is presented for dose calculations, exploring the feasibility of remote computing power for parallelization and acceleration of computationally and time intensive radiotherapy tasks in moving toward online adaptive therapies. Methods An analytical model was developed to estimate...
Article
Full-text available
A biomechanical model is developed and validated for breathing-induced deformation of human lung. Specifically, a subject-specific poro-elastic lung model is used to predict the displacement over the breathing cycle and compared with displacement derived from high resolution image registration. The lung geometry is derived from four-dimensional com...
Article
Full-text available
High-speed scanning in optical coherence tomography (OCT) often comes with either compromises in image quality, the requirement for post-processing of the acquired images, or both. We report on distortion-free OCT volumetric imaging with a dual-axis micro-electro-mechanical system (MEMS)-based handheld imaging probe. In the context of an imaging pr...
Article
Purpose:Patient safety hazards such as a wrong patient/site getting treated can lead to catastrophic results. The purpose of this project is to automatically detect potential patient safety hazards during the radiotherapy setup and alert the therapist before the treatment is initiated. Methods:We employed a set of co-located and co-registered 3D ca...
Conference Paper
Purpose:To evaluate the effect of inter- and intra-fractional tumor motion on the error in four-dimensional computed tomography (4DCT) maximal intensity projection (MIP)–based lung tumor internal target volumes (ITV), using deformable image registration of real-time 2D-sagital cine-mode MRI acquired during lung SBRT treatments. Methods:Five lung tu...
Article
Purpose:Clinical deformable image registration (DIR) accuracy is difficult to quantify, making validation and verification manual and time consuming. It has also been seen that DIR accuracy can be improved by patient and site specific optimization. We previously investigated a cost function to parameterize image similarity metrics (ISMs) and provid...
Article
Purpose:The purpose of this project is to derive high precision elastography measurements from 4DCT lung scans to facilitate the implementation of elastography in a radiotherapy context. Methods:4DCT scans of the lungs were acquired, and breathing stages were subsequently registered to each other using an optical flow DIR algorithm. The displacemen...
Article
Purpose:On-board MRI provides superior soft-tissue contrast, allowing patient alignment using tumor or nearby critical structures. This study aims to study H&N MRI-guided IGRT to analyze inter-fraction patient setup variations using soft-tissue targets and design appropriate CTV-to-PTV margin and clinical implication. Methods:282 MR images for 10 H...
Conference Paper
Breast radiation therapy is typically delivered to the patient in either supine or prone position. Each of these positioning systems has its limitations in terms of tumor localization, dose to the surrounding normal structures, and patient comfort. We envision developing a pneumatically controlled breast immobilization device that will enable the b...
Conference Paper
Deformable image registration (DIR) is an important step in radiotherapy treatment planning. An optimal input registration parameter set is critical to achieve the best registration performance with the specific algorithm. Methods In this paper, we investigated a parameter optimization strategy for Optical-flow based DIR of the 4DCT lung anatomy. A...
Article
Purpose: Breast elastography is a critical tool for improving the targeted radiotherapy treatment of breast tumors. Current breast radiotherapy imaging protocols only involve prone and supine CT scans. There is a lack of knowledge on the quantitative accuracy with which breast elasticity can be systematically measured using only prone and supine C...
Article
Purpose: Radiation therapy simulations solely based on MRI have advantages compared to CT-based approaches. One feature readily available from computed tomography(CT) that would need to be reproduced with MR is the ability to compute digitally reconstructedradiographs(DRRs) for comparison against on-board radiographs commonly used for patient posit...
Article
Cardio-vascular blood flow simulations are essential in understanding the blood flow behavior during normal and disease conditions. To date, such blood flow simulations have only been done at a macro scale level due to computational limitations. In this paper, we present a GPU based large scale solver that enables modeling the flow even in the smal...
Article
3D kinect camera systems are essential for real-time imaging of 3D treatment space that consists of both the patient anatomy as well as the treatment equipment setup. In this paper, we present the technical details of a 3D treatment room monitoring system that employs a scalable number of calibrated and coregistered Kinect v2 cameras. The monitorin...
Article
Fast, robust, nondestructive 3D imaging is needed for the characterization of microscopic tissue structures across various clinical applications. A custom microelectromechanical system (MEMS)-based 2D scanner was developed to achieve, together with a multi-level GPU architecture, 55 kHz fast-axis A-scan acquisition in a Gabor-domain optical coheren...
Conference Paper
The effect of gravity is considered on biomechanical modeling of human lung deformation for radiotherapy application. The lung is assumed to behave as a poro-elastic medium with spatially dependent property. Finite element simulation is performed on a three-dimensional (3D) lung geometry reconstructed from four-dimensional computed tomography (4DCT...
Conference Paper
Fast, robust, nondestructive 3D imaging is needed for characterization of microscopic structures in industrial and clinical applications. A custom micro-electromechanical system (MEMS)-based 2D scanner system was developed to achieve 55 kHz A-scan acquisition in a Gabor-domain optical coherence microscopy (GD-OCM) instrument with a novel multilevel...
Article
Human lungs undergo breathing-induced deformation in the form of inhalation and exhalation. Modeling human lung dynamics is numerically complicated by the lack of information on the accurate lung elastic behavior and the fluid-structure interactions between air and the lung tissue. This paper presents a mathematical method to integrate deformation...
Article
Modeling human lung dynamics is critical in quantitatively representing the subject specific 4D tumor motion. However, the process is numerically complicated by fluid-structure interactions (FSI) between air and the visco-elastic lung tissue and the lack of information on the anisotropic lung elasticity. We present a mathematical method to couple i...
Article
To employ a multi-3D camera system for patient and treatment equipment tracking using the Kinect v2 camera system. The system has two cameras, a color camera (RGB) and a time-of-flight infrared camera (IR). The IR is used to measure the distances between the camera and the subject for each IR pixel producing a point cloud of fraxels (fragment pixel...
Article
Purpose: To propose and test a cost function, which parameterizes image similarity metrics (ISMs) to provide a robust quantification of deformable image registration (DIR) accuracy. The gold standard for quantitatively assessing registration accuracy is manually placed landmarks. However, placing landmarks are time consuming, user dependent, and s...
Article
To model fast-moving heart surface motion as a function of cardiac-phase in order to compensate for the lack of cardiac-gating in evaluating accurate dose to coronary structures. Ten subjects were prospectively imaged with a breath-hold, cardiac-gated MRI protocol to determine heart surface motion. Radial and planar views of the heart were resample...
Article
Purpose: Breast elastography is a critical tool for improving the targeted radiotherapy treatment of breast tumors. Current breast radiotherapyimaging protocols only involve prone and supine CT scans. There is a lack of knowledge on the quantitative accuracy with which breast elasticity can be systematically measured using only prone and supine CT...
Article
The purpose of this study was to systematically monitor anatomic variations and their dosimetric consequences during intensity modulated radiation therapy (IMRT) for head and neck (H&N) cancer by using a graphics processing unit (GPU)-based deformable image registration (DIR) framework. Eleven IMRT H&N patients undergoing IMRT with daily megavoltag...
Article
Purposes: To improve normal tissue sparing for head-and-neck (H&N) image-guided radiotherapy (IGRT) by employing treatment plans with tighter margins for CTV 2 and 3, and documenting the delivered dose throughout the entire treatment course. Methods: Ten H&N cases treated with simultaneous integrated boost on a TomoTherapy unit (Accuray Inc.) were...
Article
To assess the feasibility of radiation therapy treatment planning 4-dimensional computed tomography (4DCT) and deep-inspiration breath-hold (DIBH) CT to accurately contour the left anterior descending artery (LAD), a primary indicator of radiation-induced cardiac toxicity for patients undergoing radiation therapy. Ten subjects were prospectively im...
Conference Paper
Full-text available
We have developed a cellular resolution imaging modality, Gabor-Domain Optical Coherence Microscopy, which combines the high lateral resolution of confocal microscopy with the high sectioning capability of optical coherence tomography to image deep layers in tissues with high-contrast and volumetric resolution of 2 μm. A novelty of the custom micro...
Article
Purpose: Validating the usage of deformable image registration (dir) for daily patient positioning is critical for adaptive radiotherapy (RT) applications pertaining to head and neck (HN) radiotherapy. The authors present a methodology for generating biomechanically realistic ground-truth data for validating dir algorithms for HN anatomy by (a) de...
Article
Purpose: Real-time adaptive planning and treatment has been infeasible due in part to its high computational complexity. There have been many recent efforts to utilize graphics processing units (GPUs) to accelerate the computational performance and dose accuracy in radiation therapy. Data structure and memory access patterns are the key GPU factor...
Article
To develop an automated framework for 3D deformable image registration (DIR), register the pre-treatment CT scans to the planning CT scan and to quantify systematically the DIR accuracy using a biomechanical head and neck (BH&N) model for head and neck adaptive radiation therapy (ART).
Article
Full-text available
Gabor-domain optical coherence microscopy (GD-OCM) is a volumetric high-resolution technique capable of acquiring three-dimensional (3-D) skin images with histological resolution. Real-time image processing is needed to enable GD-OCM imaging in a clinical setting. We present a parallelized and scalable multi-graphics processing unit (GPU) computing...
Article
Purpose: Traditional radiation therapy of cancer is heavily dependent on CT. CT provides excellent depiction of the bones but lacks good soft tissue contrast, which makes contouring difficult. Often, MRIs are fused with CT to take advantage of its superior soft tissue contrast. Such an approach has drawbacks. It is desirable to perform treatment si...
Article
Purposes: To systematically monitor anatomic variations and their dosimetric consequences during head-and-neck (H'N) radiation therapy using a GPU-based deformable image registration (DIR) framework. Methods: Eleven H'N IMRT patients comprised the subject population. The daily megavoltage CT and weekly kVCT scans were acquired for each patient. The...
Article
Purpose: Deformable image registration (DIR) plays a pivotal role in head and neck adaptive radiotherapy but a systematic validation of DIR algorithms has been limited by a lack of quantitative high-resolution groundtruth. We address this limitation by developing a GPU-based framework that provides a systematic DIR validation by generating (a) mode...
Article
Purpose: To develop a GPU-based framework that can generate highresolution and patient-specific biomechanical models from a given simulation CT and contoured structures, optimized to run at interactive speeds, for addressing adaptive radiotherapy objectives. Method: A Massspring-damping (MSD) model was generated from a given simulation CT. The mode...
Article
Purpose: To investigate the feasibility of improved normal tissue sparing for head-and-neck (H'N) image-guided radiotherapy (IGRT) by employing tighter CTV-to-PTV margins for target level II/III though a GPU-based deformable image registration and dose accumulation framework. Methods: Ten H'N simultaneous integrated boost cases treated on TomoThera...
Conference Paper
Full-text available
A PMMA based plastic optical fibre sensor for use in real time radiotherapy dosimetry is presented. The optical fibre tip is coated with a scintillation material, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb), which fluoresces when exposed to ionising radiation (X-Ray). The emitted visible light signal penetrates the sensor optical fibre and prop...
Article
The aim of this paper is to enable a simulation tool for cardiovascular blood flow in order to better understand normal and hemorrhage conditions. A second order partial differential model for cardiovascular blood flow is employed. The individual components of the model is represented as an RLC circuit representation. Injury behavior is simulated b...
Article
Full-text available
The aim of this paper is to model and visualize cardiovascular deformations in order to better understand vascular movements inside the lung and heart caused by abnormal cardiac conditions. The modeling was performed in two steps: first step involved modeling the cardiac output taking into account of the heart rate and preload blood volume, contrac...