The Versa-HD Hexapod is an advanced radiotherapy system that integrates a high-definition linear accelerator (Versa HD) with a robotic, six-degree-of-freedom patient positioning table (Hexapod). It represents the convergence of high-speed radiation delivery and sub-millimeter robotic targeting. While traditional radiation therapy machines can effectively treat general areas, they often struggle with the microscopic complexities of irregularly shaped tumors located near critical organs.
The primary problem this technology solves is “geometric uncertainty.” In standard radiotherapy, a patient lies on a table that can typically move in three or four directions (up/down, left/right, in/out). However, the human body is not a rigid box; a patient might be slightly tilted, or their internal anatomy might rotate minutely compared to the planning scan. If the treatment table cannot correct these rotational errors, the radiation beam might miss the edge of the tumor or strike healthy tissue. The Versa-HD Hexapod eliminates this margin of error. By moving in six distinct dimensions including pitch, roll, and yaw the system aligns the patient’s anatomy with the radiation beam to within sub-millimeter accuracy, allowing for the safe delivery of ablative, high-dose radiation (stereotactic radiosurgery) to targets previously considered too risky to treat.
How the Versa-HD Hexapod Works?
The system operates through a synchronized workflow known as Image-Guided Radiation Therapy (IGRT), where the machine “sees,” “adjusts,” and “treats” in a seamless loop.
The High-Definition Beam (Agility MLC)
The “HD” in Versa-HD refers to the high-definition beam shaping capability.
- Multi-Leaf Collimator (MLC): Inside the head of the machine are 160 distinct tungsten leaves (the Agility MLC). These leaves move independently at high speeds.
- Beam Sculpting: As the machine rotates around the patient, these leaves constantly shift to shape the radiation beam, blocking healthy tissue while keeping the tumor exposed. They can create complex, non-geometric shapes that match the tumor’s profile exactly, even as the machine moves.
The 6D Robotic Correction (Hexapod)
The defining mechanical feature is the Hexapod treatment table. Standard tables correct for translation (X, Y, Z axes). The Hexapod corrects for rotation.
- Imaging Verification: Before treatment begins, the machine takes a 3D Cone Beam CT (CBCT) scan of the patient on the table.
- The Calculation: The software overlays this live image with the original planning scan. It identifies exactly how the patient is positioned differently perhaps the hips are rotated 0.5 degrees to the left, or the chin is tilted 1 degree up.
- 6-Degree Adjustment: The robotic table automatically adjusts in six dimensions:
- Lateral: Left/Right
- Longitudinal: Head/Foot
- Vertical: Up/Down
- Pitch: Tilting forward/backward (like a nodding head)
- Roll: Tilting side-to-side (like a boat)
- Yaw: Rotating on the central axis (like a spinning top)
This robotic micro-adjustment aligns the tumor perfectly with the machine’s isocenter.
High Dose Rate Delivery (FFF Mode)
Once aligned, the Versa HD utilizes “Flattening Filter Free” (FFF) technology. By removing a physical filter used in older machines, the system allows for a much higher flow of radiation (dose rate). This enables the delivery of massive therapeutic doses in a fraction of the time required by conventional machines.
Clinical Advantages and Patient Benefits
The Versa-HD Hexapod shifts the paradigm from standard fractionation to “hypofractionation” delivering higher doses in fewer sessions with greater safety.
Extreme Precision (Stereotactic Capability)
The combination of the Agility beam-shaping and Hexapod table correction allows for Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiotherapy (SBRT).
- Target Accuracy: The system achieves accuracy often within 0.1 millimeters.
- Healthy Tissue Sparing: Because the alignment is so precise, oncologists can drastically reduce the “safety margins” (the extra tissue treated around a tumor). This spares adjacent critical structures such as the optic nerve in brain treatments or the spinal cord in spine treatments from unnecessary radiation.
Reduced Treatment Times
- Speed: The high dose rate (FFF mode) combined with fast leaf speeds means complex treatments that used to take 20 to 30 minutes can now be completed in 5 to 10 minutes.
- Motion Management: Faster treatment reduces the chance of the patient moving voluntarily (shifting on the table) or involuntarily (digestion, bladder filling) during the beam-on time, ensuring the plan remains accurate from start to finish.
Improved Success Rates
- Tumor Control: The ability to safely escalate the dose (give more radiation) directly correlates with higher rates of tumor destruction (local control), particularly in radio-resistant tumors.
- Fewer Sessions: Patients who previously required 30 to 40 daily sessions (standard fractionation) may now be eligible for courses of just 1 to 5 sessions (SBRT), significantly reducing the logistical burden of cancer treatment.
Targeted Medical Fields and Applications
This technology is the workhorse of the Radiation Oncology department, specifically utilized for complex cases requiring the highest degree of geometric conformity.
Neuro-Oncology (Brain Tumors)
- Multiple Metastases: The system allows for the treatment of multiple brain metastases in a single session using a single isocenter, sparing the patient from whole-brain radiation and preserving cognitive function.
- Acoustic Neuromas & Meningiomas: Used to treat benign tumors near the hearing nerves or brainstem where surgical removal carries high risks of paralysis.
Thoracic and Abdominal Oncology
- Lung Cancer: It effectively treats early-stage lung cancer or lung metastases. The system tracks the tumor and the Hexapod corrects for baseline shifts, often serving as a non-invasive alternative to lung surgery.
- Liver and Pancreas: These tumors are notoriously difficult to treat due to their proximity to the stomach and bowel. The Versa-HD Hexapod allows for ablative doses to the tumor while strictly blocking dose to the sensitive GI tract.
Spinal Oncology
- Spine Metastases: When cancer spreads to the spine, it causes severe pain and risks fracture. The system delivers “spine radiosurgery,” essentially carving the tumor away from the spinal cord using radiation, often relieving pain faster and more durably than standard radiation.
Urology (Prostate Cancer)
- Extreme Hypofractionation: Clinicians use the system to deliver the entire course of prostate cancer treatment in just 5 days (SBRT), compared to the traditional 8 weeks, with comparable cure rates and low toxicity.
The Patient Experience
The treatment process is non-invasive, painless, and relatively quick, resembling a sophisticated X-ray appointment rather than a surgical procedure.
Preparation and Setup
- Immobilization: Upon entering the treatment room (often called the “vault”), the patient lies on the Hexapod table. Customized immobilization devices such as a thermoplastic face mask for brain patients or a body mold for lung patients are used to ensure consistent positioning.
- The “Pre-Flight” Check: Once the staff leaves the room, the machine rotates around the patient to take a CBCT scan. This takes about 60 seconds.
The Robotic Adjustment
- Remote Correction: The patient may feel the table move slightly beneath them. This is the Hexapod performing its 6-dimensional correction based on the imaging results. It might tilt slightly or rotate a fraction of an inch. This movement is smooth and controlled.
The Treatment Delivery
- Quiet Operation: The Versa HD rotates silently around the patient. The only sound is a rhythmic buzzing or humming when the beam is active.
- No Sensation: The patient feels nothing no heat, no burning, and no electricity. The radiation is invisible.
- Duration: The actual “beam-on” time is often only a few minutes. Including setup and imaging, the entire slot is typically 15 to 20 minutes. The patient is then free to leave and resume daily activities immediately.
Safety and Precision Standards
The Versa-HD Hexapod operates within a rigorous safety framework designed to prevent geographic misses and overdose.
4D Motion Management
For tumors that move with breathing (like in the lung or liver), the system utilizes 4D-CT planning.
- Gating and Tracking: The machine understands the patient’s breathing cycle. It can be programmed to turn the beam on only when the tumor is in the correct position (e.g., full exhale) and turn it off instantly if the tumor moves out of range. This ensures the radiation beam is not “chasing” a moving target but rather waiting for it.
Collision Detection Systems
Because the machine and the table move in complex orbits close to the patient, the system is equipped with sensitive capacitive sensors.
- Safety Halo: These sensors create an invisible safety field around the patient. If the machine head gets too close to the patient or the table, the motion stops instantly to prevent physical contact.
Dosimetric Verification
Before the patient ever starts their course of treatment, the medical physics team performs a “QA” (Quality Assurance) run. They deliver the patient’s specific plan to a phantom (a device that measures radiation) on the Hexapod table to verify that the dose distribution calculated by the computer matches exactly what the machine delivers in the real world.
