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Integrated System for Delivery of Conformal and Intensity Modulated Radiation Therapy

IP.com Disclosure Number: IPCOM000210427D
Original Publication Date: 2011-Sep-05
Included in the Prior Art Database: 2011-Sep-05
Document File: 2 page(s) / 83K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

During radiotherapy treatments, the parallelism of x-ray beams is important to achieve a good x-ray image without affecting other healthy parts of the patient’s body. There exist different possibilities to guarantee parallelism of x-ray beams. Today, collimators and hereby mostly MultiLeaf Collimators (MLC) are used within conformal and intensity modulated radiotherapy. Modulation by a MLC is achieved by altering the shape of the open radiation field as a function of time. This results in inaccuracies due to imperfect leaf positioning and timing synchronization. The treatment delivery time is typically really long since the leaf speed is limited. Besides a global optimum leaf sequence that minimizes treatment time is hard to find. There exists also a leakage between adjacent leafs and leaf ends of closed leaf pairs. Further, the beam penumbra is relatively large. The spatial resolution of a MLC is limited by the leaf width, both in terms of the ability to provide radiation beams that conform to the shape of the target, as well as the resolution of the deliverable intensity pattern. In addition MLCs are complex electromechanical devices that are typically the most costly single component of a delivery system. MLCs also incur high service costs and may require frequent calibration. MLC control electronics may be sensitive to scattered beam radiation and this may decrease reliability and increase service costs. For fast-rotating delivery systems, friction between leaves due to large and varying centripetal forces are likely to result in complicated leaf dynamics that may be difficult to control.

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Integrated System for Delivery of Conformal and Intensity Modulated Radiation Therapy

Idea: Dr. Iwan Kawrakow, DE-Heidelberg; Jonathan Maltz, US-Concord, California

During radiotherapy treatments, the parallelism of x-ray beams is important to achieve a good x-ray image without affecting other healthy parts of the patient's body. There exist different possibilities to guarantee parallelism of x-ray beams. Today, collimators and hereby mostly MultiLeaf Collimators (MLC) are used within conformal and intensity modulated radiotherapy. Modulation by a MLC is achieved by altering the shape of the open radiation field as a function of time. This results in inaccuracies due to imperfect leaf positioning and timing synchronization.

The treatment delivery time is typically really long since the leaf speed is limited. Besides a global optimum leaf sequence that minimizes treatment time is hard to find. There exists also a leakage between adjacent leafs and leaf ends of closed leaf pairs. Further, the beam penumbra is relatively large. The spatial resolution of a MLC is limited by the leaf width, both in terms of the ability to provide radiation beams that conform to the shape of the target, as well as the resolution of the deliverable intensity pattern. In addition MLCs are complex electromechanical devices that are typically the most costly single component of a delivery system. MLCs also incur high service costs and may require frequent calibration. MLC control electronics may be sensitive to scattered beam radiation and this may decrease reliability and increase service costs. For fast-rotating delivery systems, friction between leaves due to large and varying centripetal forces are likely to result in complicated leaf dynamics that may be difficult to control.

Before using MLCs, the use of so called modulator blocks was common. Modulator blocks have the advantage to provide lower leakage and sharper beam penumbra. They are also not sensitive to the effects of gantry motion. Nevertheless, their usage has been almost completely discontinued after the introduction of MLCs, because of many difficulties for practical application. As one of these difficulties the lack of integration between the treatment planning system and the machine producing the modulator blocks can be mentioned. Besides, the difficulty of storing and transporting the modulator blocks to the treatment room is a problem as well. Also, the need to manually attach each block to the radiation delivery device, which leads to long treatment times because a different block is needed for each radiation beam, has to be mentioned.

In the following, an integrated system for delivering conformal or intensity modulated radiation therapy using modulating blocks is proposed. Hereby, blocks can be prepared, stored, retrieved, and placed in the beam path automatically, witho...