Analysis of Respiratory Motion in Chest Organs: During External Beam Radiotherapy (original) (raw)
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Analysis and evaluation of periodic physiological organ motion in radiotherapy treatments
Radiotherapy and Oncology, 2004
Background and purpose: A system for the detection, measurement and analysis of the periodic physiological organ motion during radiotherapy treatment is proposed and clinically tested in this paper. Material and methods: The procedure is based on the acquisition of fluoroscopic sequences, followed by an automatic detection of the movement using cross-correlations with matched filters. Results: The system generates a probability density function (PDF) of finding a mobile organ in a position at a certain time. The maximum path of the mobile structures can be determined to define the planning target volume (PTV) without ambiguities. Conclusions: Physiological movements can be accurately included in the daily planning routine, which is not essentially modified, without needing previous patient training.
Prediction of Motion of Chest Organs during Radiotherapy Using Image Registration Technique
Registration of image using MatLab image processing program and its comparison with wavelets is being discussed in this paper. As science is growing and new and sophisticated instruments are being developed day by day, biomedical instruments to diagnose the patient are also available in wide varieties to take image of the infected external or internal body organs. Due to respiration, many tumours in the thorax and abdomen may move as much as 3 cm peak-to-peaks during radiation treatment. To mitigate motion-induced irradiation of normal lung tissue, clinics have employed external markers to gate the treatment beam. This technique assumes that the correlation between the organs position in inspiration phase and expiration phase positions remains constant interfractionally and intra-fractionally. In this work, a study has been performed to assess the validity of this correlation assumption for internal organs based gated radiotherapy, by measuring the displacement of different chest organs motion within a gating window. The results discovered significant repositioning errors of organs during respiration even in highly controlled conditions, affecting particularly chest organs relatively far from the skin. The outcome of the experimental application of it confirms its potential as a tool for internal organs motion and automatic detection of any errors caused by breasting or other unpredictable movements. The results allow the radiation oncologist to take suitable countermeasures in case of significant errors (body contour is equally (3.17+0.23 mm), for left lung displacement reading (2.56+0.99 mm) and right lung is (2.42+0.77 mm). In addition, the use of the image registration technique for automatic position control is envisaged.
International Journal of Radiation Oncology*Biology*Physics, 2010
Purpose: To evaluate the effectiveness of the stereotactic body frame (SBF), with or without a diaphragm press or a breathing cycle monitoring device (Abches), in controlling the range of lung tumor motion, by tracking the realtime position of fiducial markers. Methods and Materials: The trajectories of gold markers in the lung were tracked with the real-time tumortracking radiotherapy system. The SBF was used for patient immobilization and the diaphragm press and Abches were used to actively control breathing and for self-controlled respiration, respectively. Tracking was performed in five setups, with and without immobilization and respiration control. The results were evaluated using the effective range, which was defined as the range that includes 95% of all the recorded marker positions in each setup. Results: The SBF, with or without a diaphragm press or Abches, did not yield effective ranges of marker motion which were significantly different from setups that did not use these materials. The differences in the effective marker ranges in the upper lobes for all the patient setups were less than 1mm. Larger effective ranges were obtained for the markers in the middle or lower lobes. Conclusion: The effectiveness of controlling respiratory-induced organ motion by using the SBF+diaphragm press or SBF + Abches patient setups were highly dependent on the individual patient reaction to the use of these materials and the location of the markers. They may be considered for lung tumors in the lower lobes, but are not necessary for tumors in the upper lobes.
The management of respiratory motion in radiation oncology report of AAPM Task Group 76
Medical Physics, 2006
This document is the report of a task group of the Radiation Therapy Committee of the AAPM and has been prepared primarily to advise medical physicists involved in the external-beam radiation therapy of patients with thoracic, abdominal and pelvic tumors that move due to respiratory motion. The purpose of this report is to describe the magnitude of respiratory motion, discuss radiotherapy-specific problems caused by respiratory motion, explain techniques that explicitly manage respiratory motion during radiotherapy and give recommendations in the application of these techniques for patient care, including quality assurance (QA) guidelines for these devices. The major recommendations of this report are that tumor motion should be measured (when possible) for each patient for whom respiratory motion is a concern. If motion is greater than 5 mm, and a method of respiratory motion management is available, and the patient can tolerate the procedure, respiratory motion management technology should be used. Knowledge in the field of respiratory motion in radiation oncology is continually growing. This report is intended to reflect the current state of the scientific understanding and technical methodology in imaging, treatment planning and radiation delivery for radiation oncology patients with tumors affected by respiratory motion.
Acta Oncologica, 2013
Purpose . To investigate the stability of target motion amplitude and motion directionality throughout full stereotactic body radiotherapy (SBRT) treatments of tumors in the liver. Material and methods. Ten patients with gold markers implanted in the liver received 11 courses of 3-fraction SBRT on a conventional linear accelerator. A four-dimensional computed tomography (4DCT) scan was obtained for treatment planning. The time-resolved marker motion was determined throughout full treatment fi eld delivery using the kV and MV imagers of the accelerator. The motion amplitude and motion directionality of all individual respiratory cycles were determined using principal component analysis (PCA). The variations in motion amplitude and directionality within the treatment courses and the difference from the motion in the 4DCT scan were determined. Results. The patient mean ( Ϯ 1 standard deviation) peak-to-peak 3D motion amplitude of individual respiratory cycles during a treatment course was 7.9 Ϯ 4.1 mm and its difference from the 4DCT scan was Ϫ 0.8 Ϯ 2.5 mm (max, 6.6 mm). The mean standard deviation of 3D respiratory cycle amplitude within a treatment course was 2.0 Ϯ 1.6 mm. The motion directionality of individual respiratory cycles on average deviated 4.6 Ϯ 1.6 ° from the treatment course mean directionality. The treatment course mean motion directionality on average deviated 7.6 Ϯ 6.5 ° from the directionality in the 4DCT scan. A single patient-specifi c oblique direction in space explained 97.7 Ϯ 1.7% and 88.3 Ϯ 10.1% of all positional variance (motion) throughout the treatment courses, excluding and including baseline shifts between treatment fi elds, respectively. Conclusion. Due to variable breathing amplitudes a single 4DCT scan was not always representative of the mean motion amplitude during treatment. However, the motion was highly directional with a fairly stable direction throughout treatment, indicating a potential for more optimal individualized motion margins aligned to the preferred direction of motion.
International Journal of Radiation Oncology*Biology*Physics, 2004
Purpose: The purpose of this study is to investigate the correlation between the respiratory waveform measured using a respiratory sensor and three-dimensional (3D) tumor motion. Methods and Materials: A laser displacement sensor (LDS: KEYENCE LB-300) that measures distance using infrared light was used as the respiratory sensor. This was placed such that the focus was in an area around the patient's navel. When the distance from the LDS to the body surface changes as the patient breathes, the displacement is detected as a respiratory waveform. To obtain the 3D tumor motion, a biplane digital radiography unit was used. For the tumor in the lung, liver, and esophagus of 26 patients, the waveform was compared with the 3D tumor motion. The relationship between the respiratory waveform and the 3D tumor motion was analyzed by means of the Fourier transform and a cross-correlation function. Results: The respiratory waveform cycle agreed with that of the cranial-caudal and dorsal-ventral tumor motion. A phase shift observed between the respiratory waveform and the 3D tumor motion was principally in the range 0.0 to 0.3 s, regardless of the organ being measured, which means that the respiratory waveform does not always express the 3D tumor motion with fidelity. For this reason, the standard deviation of the tumor position in the expiration phase, as indicated by the respiratory waveform, was derived, which should be helpful in suggesting the internal margin required in the case of respiratory gated radiotherapy. Conclusion: Although obtained from only a few breathing cycles for each patient, the correlation between the respiratory waveform and the 3D tumor motion was evident in this study. If this relationship is analyzed carefully and an internal margin is applied, the accuracy and convenience of respiratory gated radiotherapy could be improved by use of the respiratory sensor. Thus, it is expected that this procedure will come into wider use.
Novel breathing motion model for radiotherapy
International Journal of …, 2005
Purpose: An accurate model of breathing motion under quiet respiration is desirable to obtain the most accurate and conformal dose distributions for mobile lung cancer lesions. On the basis of recent lung motion measurements and the physiologic functioning of the lungs, we have determined that the motion of lung and lung tumor tissues can be modeled as a function of five degrees of freedom, the position of the tissues at a user-specified reference breathing phase, tidal volume and its temporal derivative airflow (tidal volume phase space). Time is an implicit variable in this model. Methods and Materials: To test this hypothesis, a mathematical model of motion was developed that described the motion of objects p in the lungs as linear functions of tidal volume and airflow. The position of an object was described relative to its position P ជ 0 at the reference tidal volume and zero airflow, and the motion of the object was referenced to this position. Hysteresis behavior was hypothesized to be caused by pressure imbalances in the lung during breathing and was, in this model, a function of airflow. The motion was modeled as independent tidal volume and airflow displacement vectors, with the position of the object at time t equal to the vector sum r ជ P (t) ϭ r ជ v (t) ϩ r ជ f (t) where r ជ v (t) and r ជ f (t) were displacement vectors with magnitudes approximated by linear functions of the tidal volume and airflow. To test this model, we analyzed five-dimensional CT scans (CT scans acquired with simultaneous real-time monitoring of the tidal volume) of 4 patients. The scans were acquired throughout the lungs, but the trajectories were analyzed in the couch positions near the diaphragm. A template-matching algorithm was implemented to identify the positions of the points throughout the 15 scans. In total, 76 points throughout the 4 patients were tracked. The lateral motion of these points was minimal; thus, the model was described in two spatial dimensions, with a total of six parameters necessary to describe the 30 degrees of freedom inherent in the 15 positions. Results: For the 76 evaluated points, the average discrepancy (the distance between the measured and prediction positions) of the 15 locations for each tracked point was 0.75 ؎ 0.25 mm, with an average maximal discrepancy of 1.55 ؎ 0.54 mm. The average discrepancy was also tabulated as a fraction of the breathing motion. Discrepancies of <10% and 15% of the overall motion occurred in 73% and 95% of the tracked points, respectively. Conclusion: The motion tracking algorithms are being improved and automated to provide more motion data to test the models. This may allow a measurement of the motion-fitting parameters throughout the lungs. If the parameters vary smoothly, interpolation may be possible, yielding a continuous mathematical model of the breathing motion throughout the lungs. The utility of the model will depend on its stability as a function of time. If the model is only robust during the measurement session, it may be useful for determining lung function. If it is robust for weeks, it may be useful for treatment planning and gating of lung treatments. The use of tidal volume phase space for characterizing breathing motion appears to have provided, for the first time, the potential for a patient-specific mathematical model of breathing motion.