Digitization and 3D Modelling: A Revolutionary Technology for Medicine and Surgery
Dr. Anne Agur
Division of Physical Medicine and Rehabilitation, Department of Medicine, Faculty of Medicine, University of Toronto
Department of Occupational Science & Occupational Therapy, Faculty of Medicine, University of Toronto
Department of Physical Therapy, Faculty of Medicine, University of Toronto
Division of Biomedical Communications, Institute of Communications and Culture, University of Toronto at Mississauga
The Wilson Centre, Faculty of Medicine, University of Toronto
Institute of Medical Science, University of Toronto
By: Valera Castanov
Photo provided by Dr. Agur
One of Canada’s largest musculoskeletal laboratories is located in the basement of the Medical Sciences Building at the University of Toronto. This lab focuses on cutting edge research dealing with digitization and three-dimensional (3D) modelling of human anatomical structures. The goal is to construct volumetric models of blood vessels, nerves, connective tissues, and particularly, muscular and skeletal elements. These volumetric models can then be digitally constructed/deconstructed and analyzed in 3D space to elucidate important tissue properties and functional characteristics. This novel technology was pioneered in the musculoskeletal laboratory and has since been employed in numerous labs across North America. Digitization and 3D modelling are actively being used to improve medical and surgical diagnostic, treatment, and rehabilitation techniques.
At the heart of the laboratory driving this research and innovation is the world-renowned anatomist, Dr. Anne Agur. She is the author of Grant’s Atlas of Anatomy, a textbook that is used not only across Canadian and American medical schools, but also around the globe. Dr. Agur is a leader in anatomical research and education, and she has agreed to discuss the ground-breaking work that her laboratory is currently focusing on and shed some light on the novel digitization and 3D modelling technology that her team has developed.
“Until recently, there was no reliable way to accurately capture the 3D architecture of fiber bundles of muscles, connective tissues, or nerve branching patterns at a sub-millimetre resolution,” Dr. Agur began. “However, our research team was able to overcome this challenge with the development of the digitization and 3D modelling methodology, which enabled the capture of the architecture of anatomical structures as in situ and the construction of volumetric anatomical models at a detail not previously possible.”
Dr. Agur continued: “To date, the majority of anatomical studies were observational in nature, and once the dissection was complete, there was no way to reassemble the anatomical structure to further investigate its architecture. Moreover, as previous studies involved two-dimensional (2D) observations, it was difficult to visualize and analyze the complex volumetric architecture of structures—for example, the intricate 3D nerve branching pattern within a muscle’s volume.”
The development of digitization and 3D modelling technology changed the paradigm of approaching human anatomy from a purely observational perspective, and provided a way to not only capture the architecture of anatomical structures as in situ, but also to analyze them through construction and deconstruction of individual anatomical elements post-dissection. The models allow researchers to observe anatomical structures from different angles and perspectives to understand their spatial organization, as well as volumetric computation of various structural and functional characteristics.
This novel methodology involves capturing Cartesian plane (X, Y, Z) coordinates along the full extent of muscle fiber bundles, nerves, blood vessels, connective tissues and skeletal elements. The stylus end of a digitizer is used to trace each anatomical element from start to finish, and Cartesian coordinates are stored along the full extent of the tracing. These data points are then imported into a modelling computer software and reconstructed into comprehensive 3D models. These models can then be joined with other elements to form complete structures. For example, in order to construct a model of a whole muscle, all of its fiber bundles and tendons have to be digitized, reconstructed in 3D, and digitally assembled. Models of nerves and blood vessels can be used to study their branching patterns and determine the anatomical regions that they supply. Models of fiber bundles and intramuscular connective tissue elements can be used to study muscle architecture as related to function.
“Importantly, our research group is a part of a multi-disciplinary and a multi-laboratory international collaboration with the goal of constructing the first dynamic 3D model of a human being at a fiber bundle level, which digitization and 3D modelling technology has made possible. It is a very exciting and ambitious task” Dr. Agur remarked. Last year, one of Dr. Agur’s PhD graduates completed the digitization and 3D modelling of all of the musculoaponeurotic and skeletal elements of the lower limb, generating close to 60,000 digital anatomical elements and over 500,000 data points. This is the most in-depth and highest-resolution analysis of the human lower limb musculature to date.
“Digitization and 3D modelling methodology is being used to gain a detailed understanding of the human anatomy and physiology, which can then be translated to the fields of medicine and surgery,” Dr. Agur explained. For instance, detailed knowledge of a muscle’s volumetric architecture, neurovascular supply, and functional characteristics can be used to plan surgeries, such as muscle flaps and tendon transfers, guide intramuscular botulin toxin injections to treat post-stroke spasticity, and develop rehabilitation protocols to target a specific anatomical area to reverse pathology and regain normal function of that region. Furthermore, muscle’s 3D architecture, including that of its intramuscular partitions, can help inform probe/electrode placement in ultrasound and electromyography studies and diagnostic procedures. Digitization and 3D modelling are actively utilized in research studies by anesthesiologists studying the branching patterns of nerves that supply joint capsules. Knowing detailed branching patterns of sensory nerves can help guide denervation procedures to help patients with chronic joint pain.
Dr. Agur is currently collaborating with anesthesiologists, orthopedic surgeons, physiatrists, physiotherapists, occupational therapists, and biomechanical engineers, along with other professionals and researchers in a multitude of fields. They share a common goal to further understand the anatomy, physiology, and biomechanics of the human body through digitization and 3D modelling, and to translate these findings to their clinical practice.
One of the lab’s endeavours is optimizing the incorporation of volumetric musculoaponeurotic architecture (obtained using digitization and 3D modelling) into patient-specific magnetic resonance imaging (MRI) muscle volume shells. This will help construct dynamic finite element musculoskeletal models capable of higher-fidelity simulation of in-vivo muscle dynamics. Presently available models primarily use idealized muscle fiber bundle templates to fill muscle volumes, which have been shown to lead to differences of 10-20% in the predicted muscle force and contracted geometries when compared to models that were based on in situ 3D architectural data. In the near future, Dr. Agur and her team hope to develop an efficient method of registering 3D architectural data to MRI-obtained surface scans to construct patient-specific models that could facilitate diagnosis, treatment and rehabilitation.
“Overall, digitization and 3D modelling is a truly novel and innovative technology, that will continue to further contribute to our understanding of human anatomy and the development of improved medical and surgical approaches,” Dr. Agur concluded.