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Research Papers

A Novel Translational Total Body Irradiation Technique

[+] Author and Article Information
Derek W. Brown

Department of Medical Physics, Tom Baker Cancer Centre, Calgary, AB, Canada T2N 4N2; Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada T2N 1N4; Department of Radiation Oncology, University of Calgary, Calgary, AB, Canadaderek.brown@albertahealthservices.ca

Kurt Knibutat, Nathan Edmonds, Daniel Tom, Leo Moriarty, Peter Hanson, Mona Udowicz, Alana Hudson

Department of Medical Physics, Tom Baker Cancer Centre, Calgary, AB, Canada

Amjad Hussain

Department of Medical Physics, Tom Baker Cancer Centre, Calgary, AB, Canada; Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada

Jose Eduardo Villarreal-Barajas

Department of Medical Physics, Tom Baker Cancer Centre, Calgary, AB, Canada; Department of Physics and Astronomy, University of Calgary, Calgary, AB, Canada; Department of Radiation Oncology, University of Calgary, Calgary, AB, Canada

J. Med. Devices 4(3), 031003 (Aug 31, 2010) (6 pages) doi:10.1115/1.4001864 History: Received March 05, 2010; Revised May 11, 2010; Published August 31, 2010; Online August 31, 2010

A novel translating bed total body irradiation treatment delivery technique that employs dynamically shaped beams is presented. The patient is translated along the floor on a moving bed through a stationary radiation beam and the shape of the radiation beam is changed dynamically as the patient is moved through it, enabling compensation for local variations in patient thickness and tissue density. We demonstrate that the use of dynamically shaped beams results in greatly improved dose homogeneity compared with standard techniques, which use a single static beam shape. Along a representative dose profile through the lungs of a mock-human body, the maximum range of dose deviation from the average is 5.6% (from +2.7% to 2.9%) for the dynamic beam technique compared with 12.8% (from +3.6% to 9.2%) for the static beam technique. A novel, dual-interlock system that prevents bed motion when the radiation beam is stopped and stops the radiation beam when the bed motor is stopped has also been developed. The dual-interlock not only enhances the safety of the treatment but also ensures accuracy in the delivery of the treatment.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic representation of the translating bed total body irradiation treatment technique. The patient is translated through a stationary radiation beam. The size and shape of the radiation beam and the speed with which the patient is translated through it determine the radiation dose the patient receives.

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Figure 2

Schematic representation of a multileaf collimator used to shape a radiation beam. There are 120 leaves, 60 on each bank. The motion of each leaf is computer controlled and leaves can be moved dynamically during treatment.

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Figure 3

Mechanical design of the translating bed TBI system

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Figure 4

Flow diagram illustrating the processes involved in initiating and monitoring the translating bed motion

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Figure 5

Schematic representation of the process through which photons deposit energy in, and cause damage to, biological tissue

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Figure 6

Normalized dose deposition as a function of depth in water. The dashed line shows measurements acquired with a distance of 176 cm between the source of radiation and the water surface, the same as that used for translating bed TBI treatments. The solid line shows measurements acquired under identical conditions but with a 1.3 cm thick piece of acrylic in the path of the radiation beam. Measurements were acquired in a stationary a water tank with a 6 MV photon beam.

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Figure 7

Calculated dose maps for static opposed photon beams (a) and dynamically modulated opposed photon beams (b). Calculated dose is displayed in color wash with lower doses in blue and higher doses in red. Dose homogeneity is greatly improved using dynamically modulated beams.

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Figure 8

Dose profiles taken along the horizontal center (dashed lines in Fig. 7) for static opposed photon beams (black) and dynamically modulated opposed photon beams (gray). Profiles are normalized to the average dose along the plateau.

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