Somvilai Mayurasakorn, MD.
Division of Therapeutic Radiology and Oncology,
Faculty of Medicine, Chiang Mai University
Imaging techniques for IGRT
Imaging techniques for IGRT
• Based on boney landmarks
• Reported outcomes of
EPID - based IGRT are
IJROBP2000; 46:400-506
Imaging techniques for IGRT
Real-Time Tumor Tracking (RTRT)
Imaging techniques for IGRT
Volumetric X-ray imaging
• Kilovoltage fan-beam CT (kV CT)
• Kilovoltage cone-beam CT (kV CBCT)
• Megavoltage cone-beam CT (MV CBCT)
• Megavoltage fan-beam CT (MV CT)
• Korreman S, Rasch C, McNair H et al. The European Society of Therapeutic Radiology and Oncology–
European Institute of Radiotherapy (ESTRO–EIR) report on 3D CT-based in-room image guidance systems:
A practical and technical review and guide.Radiotherapy and Oncology 2010; 94:129–144
Helical Tomotherapy
• Concept for Helical Tomotherapy : Since 1993
• Idea proposed by Thomas Rockwell Mackie
• Research/Prototype (Univ. of Wisconsin)
• First commercial unit installation at Wisconsin
Helical Tomotherapy
• Helical - radiation rotating around the patient
while couch is translating
– The patient is moved through the machine as a
radiation source rotates through 360°
• Tomotherapy – patient is irradiated “slice by
Helical Tomotherapy
• A Highly Integrated Platform For IMRT & IGRT
• Integrated solution for the combination of
Helical Tomotherapy
Benefits from IGRT
• Use of imaging (MVCT) immediately before or
during treatment
• To ensure that the patient and tumor are in
the correct position
Allows the correction of both random and
systematic components of set-up errors
Increasing the accuracy of treatment delivery
Helical Tomotherapy
Benefits from IMRT
Characterised by steep dose gradients
Delivering higher doses to the tumor
Maintaining acceptable doses to critical OAR
Allow for dose escalation
Helical Tomotherapy
Helical tomotherapy
• Fixed- gantry
• Arc radiation therapy
• Slice therapy
• Correction of both random
and systematic components
of set-up errors
– Step and shoot
– dynamic
The patient is moved through the treatment unit
while the radiation source rotates
around the patient
Palma et al. Cancer Treatment Reviews 2010;36 :393–399
Helical Tomotherapy
Potential advantages of arc therapies
over standard IMRT
Improved dose distributions
Using arc techniques
 The target can be treated from all angles
 Negating the issue of beam angle selection
when using fixed beams
Palma et al. Cancer Treatment Reviews 2010;36 :393–399
Quality Depends on Number of Beams
1 Beam
5 Beams
11 Beams
17 Beams
25 Beams
51 Beams
NPC patient
Comparisons of isodose
A dosimetric gain in CI and
HI of PTV and sparing of
OARs was significantly
obtained in HT versus SaSIMRT
T.-F. Lee et al. Radiotherapy and Oncology 89 (2008) 89–96
IMRT and HT: The comparison of isodose distributions of PTV and OARs
Lee et al. Radiation Oncology 2010 5:58
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