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A Volumetric Measurement Based Approach for Accurate Phase Determination of Breathing Cycle for Breath Gated Radiotherapy for Lung Cancer

IP.com Disclosure Number: IPCOM000196317D
Original Publication Date: 2010-Jun-10
Included in the Prior Art Database: 2010-Jun-10
Document File: 2 page(s) / 106K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

During radiotherapy of cancer cells the tumor has to be tracked as it changes its position because of the patient's breathing cycle and minor movements. Various techniques to track tumor motion have been developed and applied before. Earliest approaches dealing with this problem basically boil down to asking the patient to be steady either through abdominal compression, shallow breathing or holding the breath. These approaches require patient compliance, provide not much reliability and require active participation by the therapist to monitor any deviations. More recently, in gated radiation therapy where the radiotherapy beam is turned on at the appropriate breathing phase has been applied to solve this technical problem. Typically this strategy involves taking the CT (Computer Tomography) image of the patient at the end of the inhalation or exhalation cycle. For example, before or after an object is placed on the stomach of the patient and its height is tracked. When the height matches the position at the desired phase, the beam is turned on for a specific duration. However, this technique increases the treatment time significantly and measurement errors decrease the accuracy. Other approaches for gated radiotherapy based on two X-rays, the utilization of opto-electronic devices or the attachment of markers are in development.

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A Volumetric Measurement Based Approach for Accurate Phase Determination of Breathing Cycle for Breath Gated Radiotherapy for Lung Cancer

Idea: Amit Kale, Ph.D., IN-Bangalore; Vipin Gupta, IN-Bangalore; Manivannan Sundarapandian, IN- Bangalore

During radiotherapy of cancer cells the tumor has to be tracked as it changes its position because of the patient's breathing cycle and minor movements. Various techniques to track tumor motion have been developed and applied before. Earliest approaches dealing with this problem basically boil down to asking the patient to be steady either through abdominal compression, shallow breathing or holding the breath. These approaches require patient compliance, provide not much reliability and require active participation by the therapist to monitor any deviations.

More recently, in gated radiation therapy where the radiotherapy beam is turned on at the appropriate breathing phase has been applied to solve this technical problem. Typically this strategy involves taking the CT (Computer Tomography) image of the patient at the end of the inhalation or exhalation cycle. For example, before or after an object is placed on the stomach of the patient and its height is tracked. When the height matches the position at the desired phase, the beam is turned on for a specific duration. However, this technique increases the treatment time significantly and measurement errors decrease the accuracy. Other approaches for gated radiotherapy based on two X-rays, the utilization of opto-electronic devices or the attachment of markers are in development.

In the following a novel technique for breath gated radiotherapy is proposed which determines the breathing phase by three dimensional tracking of a plurality of fiducials via optical means. These aiming points are tattooed on the skin or simply stick on the skin. The points contain high resolution corners which facilitate accurate depth estimation. Using image processing, the points of interest are found in two camera images. Subsequently, the correspondence between these points is established via epipolar constraint calculations and the metric 3D reconstruction is carried out with this information.

These points along with the reference tumor location from CT transferred to a stereo camera refe...