Somvilai Mayurasakorn, MD.Division of Therapeutic Radiology and Oncology,

Faculty of Medicine, Chiang Mai University

Imaging techniques for IGRT

Imaging techniques for IGRT

On-line EPID IGRT

• Based on boney landmarks

• Reported outcomes of EPID - based IGRT are favorable

IJROBP2000; 46:400-506

Imaging techniques for IGRT

Real-Time Tumor Tracking (RTRT)CyberKnife

Imaging techniques for IGRT

• 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

(~2002)

• 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 slice”

Helical Tomotherapy

• A Highly Integrated Platform For IMRT & IGRT• Integrated solution for the combination of

IGRT and IMRT

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 positionAllows 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

IMRT• Fixed- gantry

– Step and shoot– dynamic

Helical tomotherapy• Arc radiation therapy• Slice therapy• Correction of both random

and systematic components of set-up errors

Helical Tomotherapy

The patient is moved through the treatment unit while the radiation source rotatesaround the patient

Palma et al. Cancer Treatment Reviews 2010;36 :393–399

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

Helical Tomotherapy

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 distributions

A dosimetric gain in CI and HI of PTV and sparing of OARs was significantly obtained in HT versus SaS-IMRT

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