Intrafractional gastric motion and interfractional stomach deformity during radiation therapy.
ABSTRACT To evaluate intrafractional gastric motion and interfractional variability of the stomach shape during radiation therapy (RT) for gastric lymphoma.
For 11 patients with gastric lymphomas, we undertook fluoroscopic examinations at the time of the simulation, and once a week during RT to evaluate inter- and intrafractional gastric variations. We recorded anteroposterior and left to right X-ray images at inhale and exhale in each examination. We gave coordinates based on the bony landmarks in each patient, and identified the most superior, inferior, lateral, ventral, and dorsal points of the stomach on each film. The interfractional motion was assessed as the distance between a point at inhale and the corresponding point at exhale. We also analyzed interfractional variation based on each point measured.
The intrafractional gastric motion was 11.7+/-8.3, 11.0+/-7.1, 6.5+/-6.5, 3.4+/-2.3, 7.1+/-8.2, 6.6+/-5.8mm (mean+/-SD) for the superior, inferior, right, left, ventral and dorsal points, respectively, which was significantly different between each point. The interfractional variability of stomach filling was -2.9+/-14.4, -6.0+/-13.4, 9.3+/-22.0mm for the superior-inferior (SI), lateral (LAT), and ventro-dorsal (VD) directions, respectively, and the differences of variabilities were also statistically significant. Thus, the appropriate treatment margins calculated from both systematic and random errors are 30.3, 41.0, and 50.8mm for the SI, LAT, and ventro-dorsal directions, respectively.
Both intrafractional gastric motion and interfractional variability of the stomach shape were considerable during RT. We recommend regular verification of gastric movement and shape before and during RT to individualize treatment volume.
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ABSTRACT: To determine which method of internal target volume (ITV) definition based on a respiration correlated CT (RCCT) allows optimal tumor coverage. A free breathing CT (CT(fb)) and an RCCT scan were acquired in 41 lung cancer patients. For 12 patients with a motion >7 mm in any direction, a detailed analysis was made. The RCCT scan was used to measure tumor motion and to reconstruct a CT at 10 phases (CT(10ph)), amongst which the half ventilation CT (CT(hv)). By averaging the CT(10ph), a slow CT (CT(slow)) was reconstructed. Based on those scans ITVs were delineated and treatments were planned, where for the ITV(hv) an internal margin of (motion amplitude)/4 was used. The treatment plans for the ITVs were projected on the 10 respiration phases. Doses were calculated and averaged over the 10 phases to estimate the actual CTV coverage. The 3D motion was on average 8.1+/-1.0 mm (1 SD) for all patients; no statistical difference was found between lower and upper lobe tumors. The ITV(slow) was the smallest volume on average (142+/-38 cm(3)), followed by the ITV(hv) (160+/-40 cm(3)), the ITV(10ph) (161+/-41 cm(3)) and the ITV(fb) (250+/-63 cm(3)). Mean CTV doses were between 95% and 107% of the prescribed dose for nearly all patients and treatment plans. Analysis of the CTV coverage suggested that underdosage may occur when the CT(slow) is used and a geographic miss occurred using the CT(fb), due to uncorrect localization of the average tumor position. The CT(hv) seems to be the optimal dataset for delineation, using an adequate anisotropic internal margin of (motion amplitude)/4.Radiotherapy and Oncology 10/2006; 81(1):73-80. · 4.52 Impact Factor
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ABSTRACT: To assess the correlation of respiratory volume and abdominal displacement with tumor motion as seen with X-ray fluoroscopy. Measurements throughout the patient's treatment course allowed an assessment of the interfractional reproducibility of this correlation. Data were acquired from 11 patients; 5 were studied over multiple days. Measurements of respiratory volume by spirometry and abdominal displacement by a real-time position tracking system were correlated to simultaneously acquired X-ray fluoroscopy measurements of superior-inferior tumor displacement. The linear correlation coefficient was computed for each data acquisition. The phase relationship between the surrogate and tumor signals was estimated through cross-correlation delay analysis. Correlation coefficients ranged from very high to very low (0.99-0.39, p < 0.0001). The correlation between tumor displacement and respiratory volume was higher and more reproducible from day to day than between tumor displacement and abdominal displacement. A nonzero phase relationship was observed in nearly all patients (-0.65 to +0.50 s). This relationship was observed to vary over inter- and intrafractional time scales. Only 1 of 5 patients studied over multiple days had a consistent relationship between tumor motion and either surrogate. Respiratory volume has a more reproducible correlation with tumor motion than does abdominal displacement. If forming a tumor-surrogate prediction model from a limited series of observations, the use of surrogates to guide treatment might result in geographic miss.International Journal of Radiation OncologyBiologyPhysics 12/2004; 60(4):1298-306. · 4.52 Impact Factor
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ABSTRACT: The aim of this work was to quantify the ability to predict intrafraction diaphragm motion from an external respiration signal during a course of radiotherapy. The data obtained included diaphragm motion traces from 63 fluoroscopic lung procedures for 5 patients, acquired simultaneously with respiratory motion signals (an infrared camera-based system was used to track abdominal wall motion). During these sessions, the patients were asked to breathe either (i) without instruction, (ii) with audio prompting, or (iii) using visual feedback. A statistical general linear model was formulated to describe the relationship between the respiration signal and diaphragm motion over all sessions and for all breathing training types. The model parameters derived from the first session for each patient were then used to predict the diaphragm motion for subsequent sessions based on the respiration signal. Quantification of the difference between the predicted and actual motion during each session determined our ability to predict diaphragm motion during a course of radiotherapy. This measure of diaphragm motion was also used to estimate clinical target volume (CTV) to planning target volume (PTV) margins for conventional, gated, and proposed four-dimensional (4D) radiotherapy. Results from statistical analysis indicated a strong linear relationship between the respiration signal and diaphragm motion (p<0.001) over all sessions, irrespective of session number (p=0.98) and breathing training type (p=0.19). Using model parameters obtained from the first session, diaphragm motion was predicted in subsequent sessions to within 0.1 cm (1 sigma) for gated and 4D radiotherapy. Assuming a 0.4 cm setup error, superior-inferior CTV-PTV margins of 1.1 cm for conventional radiotherapy could be reduced to 0.8 cm for gated and 4D radiotherapy. The diaphragm motion is strongly correlated with the respiration signal obtained from the abdominal wall. This correlation can be used to predict diaphragm motion, based on the respiration signal, to within 0.1 cm (1 sigma) over a course of radiotherapy.Medical Physics 05/2003; 30(4):505-13. · 2.91 Impact Factor