🤖Medical Robotics Unit 6 – Image-Guided Surgery and Planning

Key Concepts and Terminology

• Image-guided surgery (IGS) involves using medical imaging to plan, navigate, and monitor surgical procedures
• Surgical planning utilizes preoperative imaging data (CT, MRI) to create a detailed map of the surgical site and identify critical structures
• Registration is the process of aligning preoperative images with the patient's anatomy in the operating room
• Fiducial markers are artificial landmarks placed on the patient or surgical instruments to aid in registration and tracking
• Stereotactic surgery employs a 3D coordinate system to precisely locate and target specific areas within the body
• Augmented reality (AR) overlays virtual images or information onto the surgeon's view of the real world
  • AR can provide real-time guidance and visualization of anatomical structures during surgery
• Intraoperative imaging refers to imaging modalities used during surgery (fluoroscopy, ultrasound) to provide real-time updates and guidance
• Robotic systems in IGS enhance precision, dexterity, and visualization, allowing for minimally invasive procedures

Imaging Modalities for Surgical Planning

• Computed Tomography (CT) uses X-rays to create detailed cross-sectional images of the body
  • CT is often used for bony structures and can provide high-resolution images for surgical planning
• Magnetic Resonance Imaging (MRI) utilizes strong magnetic fields and radio waves to generate images of soft tissues
  • MRI is excellent for visualizing soft tissue contrast and can be used for planning surgeries involving the brain, spine, or musculoskeletal system
• Positron Emission Tomography (PET) detects the distribution of a radioactive tracer in the body to assess metabolic activity
  • PET can be combined with CT (PET-CT) to provide both functional and anatomical information for surgical planning in oncology
• Ultrasound uses high-frequency sound waves to create real-time images of internal structures
  • Ultrasound is often used for intraoperative guidance due to its portability and lack of ionizing radiation
• Functional MRI (fMRI) measures brain activity by detecting changes in blood flow
  • fMRI can be used to map critical brain functions (language, motor) for planning neurosurgical procedures
• Diffusion Tensor Imaging (DTI) is an MRI technique that visualizes the direction and integrity of white matter tracts in the brain
  • DTI can be used to plan surgical trajectories that minimize damage to critical white matter pathways

Image Registration Techniques

• Rigid registration assumes that the imaged object is a rigid body and only requires translation and rotation to align images
  • Rigid registration is often used for bony structures or when the patient's position is fixed (stereotactic frames)
• Non-rigid (deformable) registration accounts for local deformations and changes in the shape of the imaged object
  • Non-rigid registration is necessary when dealing with soft tissues that can deform during surgery (brain shift)
• Point-based registration uses corresponding landmarks (fiducial markers) in the preoperative images and the patient's anatomy to align the two coordinate systems
• Surface-based registration aligns images by matching the surfaces of anatomical structures (skin, bone) between the preoperative images and the patient
• Intensity-based registration optimizes the alignment of images based on the similarity of pixel intensities between the two images
• Hybrid registration techniques combine different approaches (point-based, surface-based, intensity-based) to improve accuracy and robustness
• Intraoperative registration updates the alignment between preoperative images and the patient's anatomy during surgery to account for changes (tissue deformation, resection)

Surgical Navigation Systems

• Optical tracking systems use cameras to detect the position of infrared markers attached to surgical instruments or the patient
  • Optical tracking provides high accuracy and real-time updates but requires a line of sight between the cameras and markers
• Electromagnetic (EM) tracking systems use a magnetic field generator and sensors to track the position and orientation of instruments
  • EM tracking does not require line of sight but can be affected by metal objects in the operating room
• Robotic navigation systems integrate robotic arms with tracking systems to provide precise instrument positioning and guidance
  • Robotic navigation can enhance dexterity, reduce tremor, and allow for minimally invasive approaches
• Augmented reality (AR) navigation overlays preoperative images or virtual models onto the surgeon's view of the surgical field
  • AR navigation can provide intuitive guidance and visualization of critical structures during surgery
• Intraoperative imaging-based navigation uses real-time imaging (fluoroscopy, ultrasound) to update the navigation system during surgery
• Hybrid navigation systems combine multiple tracking technologies (optical, EM) or imaging modalities to improve accuracy and reliability

Intraoperative Imaging and Real-Time Updates

• Fluoroscopy uses continuous X-ray imaging to provide real-time visualization of surgical instruments and anatomy
  • Fluoroscopy is commonly used in orthopedic and spinal surgeries for instrument placement and alignment
• Intraoperative CT (iCT) allows for the acquisition of CT images during surgery to update the navigation system and assess surgical progress
  • iCT can be used to verify implant placement or resection margins and to update registration in case of tissue deformation
• Intraoperative MRI (iMRI) provides real-time MRI imaging during surgery, enabling the surgeon to visualize soft tissues and adapt the surgical plan
  • iMRI is particularly useful in neurosurgery for tumor resection and updating navigation in case of brain shift
• Intraoperative ultrasound (iUS) offers real-time imaging of soft tissues without ionizing radiation
  • iUS can be used for guidance during liver, kidney, or prostate surgeries and to assess the completeness of tumor resection
• Cone-beam CT (CBCT) is a compact, mobile CT scanner that can be used intraoperatively to acquire 3D images
  • CBCT is often integrated with navigation systems in orthopedic and spinal surgeries for instrument placement and alignment
• Real-time image fusion combines intraoperative imaging with preoperative images to provide a comprehensive and updated view of the surgical site
  • Image fusion can help compensate for anatomical changes during surgery and enhance the accuracy of navigation

Robotic Systems in Image-Guided Surgery

• Robotic systems in IGS aim to enhance precision, dexterity, and visualization while minimizing invasiveness
• Surgical robots can be classified as active (autonomous or semi-autonomous control) or passive (surgeon-controlled) systems
• Active robotic systems execute pre-planned tasks or assist the surgeon in performing specific actions
  • Examples include the ROBODOC system for hip and knee replacement and the CyberKnife system for radiosurgery
• Passive robotic systems, also known as telemanipulators, allow the surgeon to remotely control the robot's movements
  • The da Vinci Surgical System is a widely used passive robotic system for minimally invasive procedures in various specialties (urology, gynecology, general surgery)
• Robot-assisted surgery can provide benefits such as increased precision, tremor filtration, and improved ergonomics for the surgeon
• Robotic systems can be integrated with image guidance and navigation technologies to further enhance accuracy and visualization
  • Examples include the Mazor X system for spinal surgery and the Neuromate robot for stereotactic neurosurgery
• Challenges in robotic IGS include the high cost of systems, the learning curve for surgeons, and the need for specialized training and maintenance

Clinical Applications and Case Studies

• Neurosurgery: IGS is widely used in neurosurgery for brain tumor resection, epilepsy surgery, and deep brain stimulation (DBS)
  • Case study: Use of iMRI and neuronavigation for glioma resection, resulting in increased extent of resection and improved patient outcomes
• Orthopedic surgery: IGS is applied in orthopedic procedures such as joint replacement, spinal fusion, and trauma surgery
  • Case study: Use of robot-assisted navigation for pedicle screw placement in spinal fusion, demonstrating increased accuracy and reduced radiation exposure
• ENT and maxillofacial surgery: IGS is used for sinus surgery, skull base surgery, and orthognathic procedures
  • Case study: Use of AR navigation for mandibular reconstruction, enabling precise planning and execution of osteotomies and implant placement
• Cardiac surgery: IGS is employed in minimally invasive valve repair, coronary artery bypass grafting (CABG), and catheter-based interventions
  • Case study: Use of robotic assistance and image guidance for minimally invasive mitral valve repair, resulting in reduced morbidity and faster recovery
• Urologic surgery: IGS is applied in procedures such as prostatectomy, partial nephrectomy, and pyeloplasty
  • Case study: Use of the da Vinci system for robot-assisted laparoscopic prostatectomy, demonstrating improved functional outcomes and reduced complications
• Gynecologic surgery: IGS is used for hysterectomy, myomectomy, and endometriosis treatment
  • Case study: Use of robot-assisted laparoscopy for complex endometriosis surgery, enabling precise dissection and preservation of fertility

Challenges and Future Directions

• Technical challenges include the need for improved image registration algorithms, real-time tracking systems, and data integration
• Workflow integration of IGS systems into the operating room requires collaboration between surgeons, engineers, and support staff
• Training and education are essential for the safe and effective use of IGS technologies
  • Simulation-based training and virtual reality platforms can help surgeons acquire the necessary skills
• Validation and assessment of the clinical impact of IGS technologies through well-designed studies and registries
• Development of advanced visualization techniques, such as 3D printing and holographic displays, to enhance surgical planning and guidance
• Integration of artificial intelligence (AI) and machine learning algorithms to improve image analysis, surgical planning, and intraoperative decision support
• Expansion of telesurgery and remote collaboration using IGS platforms, enabling expert guidance and training across distances
• Addressing ethical and legal considerations related to the use of IGS technologies, such as data privacy, liability, and access to care