Effects of cardiac motion on dose distribution during stereotactic arrhythmia radioablation treatment: A simulation and phantom study

Figures

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  FIGURE 1. Overview of the self‐made cardiac dynamic platform used in this study. (a) Side view of the platform. (b) Method of adjusting motion cycles. A direct current (DC) motor speed control pulse width modulation (PWM) circuit could adjust the duty cycle and modify the rotation speed (motion cycles) of a motor (fast or slow). (c) Method of adjusting motion amplitudes. Adjusting the angle of a joint could modify the motion amplitudes (small or large).

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  FIGURE 2. Set of measuring phantoms. (a) Radiochromic films were cut into special shapes. (b) Rectangular end‐to‐end (E2E) Ballcube II cassette in which a set of orthogonal films was inserted. (c) 12 cm diameter hemispherical dome phantom that enclosed the ballcube cassette.

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  FIGURE 3. Overview of the platforms and phantoms placement. (a) Anterior side view of the 2D cardiac motion layout. The cardiac dynamic platform was inclined 35° to the right from the superior–inferior direction. (b) Right side view of the platforms and phantoms. The phantoms were placed on the stage of the cardiac dynamic platform. Infrared markers, which were used for respiratory motion tracking, were attached to the surrogate platform of the CIRS dynamic platform.

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  FIGURE 4. Methods of analysis. (a) and (b): Centroid analysis. (a), (c), (d), and (e): Dose profile analysis. (a) An irradiated film. (b) An end‐to‐end (E2E) Film Analysis software. This software can measure the error in the centroid from the difference between the centroid of the thresholded irradiation distribution and the film center which is same to the centroid of planned distribution. (c) A cropped and dose‐transformed distribution from the irradiated film. The white solid arrow indicates the location 3 mm away from the film center slit, where the dose profile was measured. (d) A distance between 80% isodose lines shown on the dose profile (the blue solid line). (e) An isodose point. This point was calculated using a linear approximation from two points (the red points) adjacent to the 80% isodose. The distance between 80% isodose line was calculated from this isodose point and another isodose point.

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  FIGURE 5. Correlation errors in the superior–inferior and left–right directions. (a) and (b) Correlation errors in 1D cardiac motion layout and 2D cardiac motion layout, respectively. The blue square plots indicate the correlation errors without cardiac motion. The red circle plots indicate the correlation errors with cardiac motion. These plots show the correlation errors for all model points of three repetitions under same conditions.

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  FIGURE 6. Dose profile analysis in the superior–inferior direction. (a) Analyzed location of the dose profile on dose distribution (the white arrow). (b), (c), and (d) Dose profile of no‐motion tracking in 1D cardiac motion layout, respiratory motion tracking in 1D, or 2D cardiac motion layout, respectively. The blue dotted line indicates the average of the profile without cardiac motion. The red solid line indicates the average of the profile with cardiac motion. The black no‐fill symbol indicates the dose profile calculated by the treatment planning system (TPS).