TOMOTHERAPY:
HELICAL RADIATION THERAPY
A complete guide to tomotherapy โ helical IMRT delivered as the radiation source spirals continuously around the patient, with daily CT imaging built in. Particularly suited for long, complex, or multiple targets including head and neck cancers, whole-spine treatment, and total marrow irradiation.
analyticsAt a Glance
- check_circleTomotherapy rotates the radiation source in a continuous spiral while the couch moves through โ delivering IMRT from every angle in a helical pattern.
- check_circleBuilt-in daily CT imaging (mega-voltage CT) acquired immediately before each session โ position verification without a separate imaging system.
- check_circleParticularly suited for long targets (whole spine, extended field), complex shapes, and total marrow irradiation before stem cell transplant.
- check_circleAvailable at major Chinese cancer centres including Fudan University and NCC Beijing, and at leading Indian private hospitals.
What Is Tomotherapy?
Tomotherapy is a specialised form of IMRT in which the radiation source sits on a ring gantry and rotates continuously around the patient while the treatment couch slowly carries them through the opening โ producing a spiral (helical) dose delivery. The name comes from tomo (slice), the same root as CT scan, reflecting this CT-scanner-like geometry.
โThink of a standard radiation machine as a torch shining from a few fixed directions. Tomotherapy is a continuous ring of light that spirals around the target, switching tiny segments on and off thousands of times to wrap the dose tightly around the tumour.โ
Helical Delivery โ The Key Differentiator
As the ring rotates and the couch advances, the beam arrives continuously from all angles in a spiral pattern. A binary MLC โ leaves that snap fully open or shut โ creates thousands of beamlets. This helical approach is particularly powerful for long targets (whole spine, neck, abdomen) that would require many separate fields on a conventional machine.
Built-In Daily CT Imaging
Because tomotherapy shares the ring-gantry geometry of a CT scanner, it can acquire a megavoltage CT image of the patient immediately before treatment โ without a separate imaging system. This built-in daily imaging verifies position and enables adaptive replanning when anatomy changes significantly.
Radixact โ Modern Platform
Accuray's current-generation Radixact system succeeds the original TomoTherapy H series and adds the Synchrony respiratory tracking system for motion management. Patients do not need to hold their breath for lung, liver, and upper abdominal targets. Major Chinese centres have invested in Radixact as part of advanced radiation infrastructure build-outs.
TomoDirect Mode
Alongside helical delivery, tomotherapy systems offer TomoDirect โ a fixed-angle delivery mode for simpler targets such as post-mastectomy chest wall or simple bony metastases. This flexibility on a single platform allows teams to use the optimal technique for each clinical situation.
Where Tomotherapy Offers the Greatest Advantage
Tomotherapy is not automatically superior to VMAT or IMRT for all cancers. It offers the most distinctive advantage for specific clinical situations where its helical geometry solves problems that fixed-beam techniques cannot.
Head and Neck Cancer โ Complex Bilateral Targets
Head and neck cancer requires simultaneous high-dose treatment of primary tumour and bilateral cervical lymph nodes while protecting the spinal cord, parotid glands, larynx, and swallowing muscles. Tomotherapy's continuous helical delivery from every angle enables the most complex dose sculpting for these challenging geometries.
Total Marrow Irradiation (TMI) Before Stem Cell Transplant
TMI treats the entire bone marrow โ skull, spine, pelvis, femora, ribs, sternum โ while sparing lungs, kidneys, and liver. This cannot be practically achieved with conventional TBI (total body irradiation) or standard IMRT field arrangements. Tomotherapy's helical delivery over the whole body makes TMI feasible. It may reduce toxicity compared to conventional TBI conditioning.
Whole-Spine and Extended-Field Treatments
Craniospinal irradiation (CSI) for medulloblastoma and spinal tumours traditionally requires multiple field junctions โ each a potential source of dose inhomogeneity. Tomotherapy treats the entire craniospinal axis in a single continuous plan, eliminating field junctions and providing more homogeneous dose across a long treatment volume.
Multiple Simultaneous Targets
For oligometastatic disease with several lesions at different sites, or for tumours with complex surrounding nodal regions, tomotherapy's helical delivery can treat all volumes in a single plan โ dosimetrically optimising the whole treatment simultaneously rather than managing separate fields.
Tomotherapy vs VMAT vs IMRT: Key Differences
The right choice depends on tumour location, target length and complexity, and centre expertise.
| Feature | Tomotherapy | VMAT (Arc IMRT) | Static IMRT |
|---|---|---|---|
| Delivery method | Helical (continuous spiral rotation + couch advance) | Continuous arc (gantry rotation, fixed couch) | Fixed beam angles (step-and-shoot or sliding window) |
| Best for long targets | Excellent โ no field junctions | Challenging for very long targets | Multiple separate fields required |
| Session time | 5-30 min depending on target length | 2-5 min (fast) | 10-20 min |
| Built-in daily imaging | Yes โ MVCT CT on the treatment machine | CBCT on linac (separate system) | CBCT on linac (separate system) |
| Motion management | Synchrony on Radixact (respiratory tracking) | Standard gating/tracking on linac | Standard gating/tracking on linac |
| Availability | Less common than VMAT โ select specialist centres | Most well-equipped linac centres globally | All modern linac centres |
Key Numbers
- 360ยฐBeam Angles UsedHelical delivery from all angles simultaneously โ maximum conformality for complex targets.
- Whole bodyTotal Marrow Irradiation Treatment FieldTreating entire bone marrow skeleton while sparing lungs, kidneys, liver โ only practical on tomotherapy.
- 0 junctionsField Junctions โ Craniospinal Axisvs 2-3 field junctions with conventional CSI โ eliminating a major source of dose heterogeneity.
- 5-30 minPer-Session TimeShorter for simple targets; longer for whole-body or extended-field treatments.
Related Guides in the Radiation Therapy Library
Explore related radiation therapy techniques.
Frequently Asked Questions
About Tomotherapy
Is tomotherapy better than VMAT?
Not universally. Tomotherapy offers specific advantages for long or complex targets (whole spine, head and neck with extensive nodal volumes, total marrow irradiation) where its helical delivery produces superior dose distributions. For most common cancer indications treated with standard field sizes, modern VMAT on a conventional linac achieves comparable dose distributions with shorter session times and greater equipment availability. The right technique depends on the specific clinical situation.
Is tomotherapy available in China?
Yes. Major Chinese cancer centres including Fudan University Shanghai Cancer Center, National Cancer Center Beijing, and several other leading institutions have invested in tomotherapy and Radixact systems. China's radiation oncology infrastructure has grown substantially and includes current-generation equipment at leading centres โ often at 70-85% lower cost than equivalent treatment in the United States.
What is total marrow irradiation and why does it need tomotherapy?
Total marrow irradiation (TMI) targets the entire bone marrow skeleton โ including the skull, spine, ribs, pelvis, and femoral heads โ while sparing the lungs, kidneys, and liver. This is used as conditioning before stem cell transplant, as an alternative to or in addition to conventional total body irradiation. It cannot practically be delivered with standard IMRT field arrangements. Tomotherapy's helical delivery over the entire body length makes TMI feasible and allows the complex organ-sparing constraints to be met.
How CancerFax Helps
CancerFax is a specialist cancer access and patient-navigation platform. We help patients and families understand their options, organise medical records, coordinate hospital communication, and support cross-border treatment planning where appropriate.
We help collect and organise reports, scans, pathology, biomarker results, and treatment history for structured case review.
We communicate with hospitals or trial teams to assess whether a case may be suitable for further screening.
We support appointment coordination, document submission, translation, and direct communication with international departments.
For international patients, we help with practical coordination โ travel planning, hospital admission guidance, and local support.
If this option is not suitable, we help explore other relevant treatments, clinical trials, or advanced care pathways.
From inquiry through to follow-up, our coordinators provide a single point of contact for the family.
CancerFax does not guarantee treatment access, eligibility, or clinical outcome. Our role is to help patients access accurate information, structured review, and appropriate specialist pathways.
Is Tomotherapy the Right Technique for Your Cancer?
Upload your medical reports and imaging โ our radiation oncology team will review your case and advise on whether tomotherapy or another technique is most appropriate for your specific tumour and treatment goals.
This content is for informational purposes only and does not constitute medical advice. All treatment decisions must be made in consultation with a qualified radiation oncologist.