University of Florida Research Foundation, Incorporated

Jonathan Gang Li

Sartaj Kumar Sahni

Sanjay Ranka

Srijit Kamath

Chihray Liu

Guanghua Yan

Bo Lu

Jatinder Palta

Jantinder Palta

An ambiguity-free optical tracking system () includes a position sensor unit (), a control box (), a computer () and software. The position sensor unit includes two cameras (and) that track a plurality of individual infra-red reflecting markers () affixed on a patient's skin. Coordinates of the cameras in a coordinate system of the cameras are determined as part of a system calibration process by intentionally creating ambiguous markers with two true markers. Using this information, an ambiguity elimination algorithm automatically identifies and eliminates ambiguous markers. A recursive backtracking algorithm builds a one-to-one correspondence between reference markers and markers optically observed during treatment. By utilizing a concept of null markers, the backtracking algorithm deals with missing, misplaced and occluded markers.

Ambiguity-free optical tracking system

A patient safety system (PSS) () uses optical tracking in a linear accelerator treatment room to prevent gross setup errors. A patient () undergoes a computed tomography (CT) treatment-simulation scan while a CT ball bearing (BB) is on patient's surface. The CT BB is replaced with an infrared reflective marker (IRRM) () before radiotherapy treatment starts. Coordinates of the CT BB relative to an isocenter of the treatment room are used as reference for tracking. The coordinate system of an optical tracking system is converted to a coordinate system of the treatment room. The PSS evaluates setup accuracy for a radiotherapy session by comparing real-time position of the single IRRM determined by the optical tracking technology with a predicted reference position, and displays results on a graphical user interface. The PSS stops radiation when a deviation between real-time coordinates and predicted coordinates of the IRRM () exceeds a predefined threshold.

Prevention of setup errors in radiotherapy

A method and associated systemfor delivering intensity-modulated radiation therapy (IMRT) uses variable feathering field splitting for intensity modulated fields of large size. A processor controls a beam-shaping device that splits the radiation beam into a plurality of radiation fields delivered to a patient. The processor in cooperation with the beam-shaping device implements a variable feathering method which includes providing an intensity matrix for the treatment of a patient, the intensity matrix having a plurality of rows and columns for spanning a prescribed radiation field including a prescribed field width. The prescribed width is compared to a maximum field width provided by the radiation treatment system. The intensity matrix is split into a plurality of spatially overlapping intensity submatrices by variably feathering the intensity matrix when the prescribed width exceeds the maximum field width, Radiotherapy is then provided to the patient using a leaf sequencing method to generate the submatrices.

Variable feathering field splitting for intensity modulated fields of large size

A method of delivering intensity modulated radiation therapy (IMRT) is disclosed. An intensity profile for the treatment of a patient is provided which spans a prescribed field width and includes a discrete profile having intensity values at each of a plurality of sample points bounded by the prescribed width. The prescribed width is compared to a maximum field width provided by the radiation treatment system. The intensity profile is split into a plurality of intensity profile portions, each having respective widths less than the maximum width if the prescribed width is greater than the maximum width. The prescribed field is also divided into a plurality of different profile portion split arrangements. A monitor unit (MU) efficiency is calculated for each of the arrangements. One of the arrangements is selected for delivery by the system using a leaf sequencing method.

Field splitting for intensity modulated fields of large size

A method of delivering radiation treatment using multi-leaf collimation includes the step of providing a radiation fluence map which includes an intensity profile. The fluence map is converted into a preliminary leaf sequence, wherein the preliminary leaf sequence minimizes machine on-time and is generated without leaf movement constraints. The leaf movement constraint is imposed on the preliminary leaf sequence. At least one constraint elimination algorithm is then applied, the algorithm adjusting the preliminary leaf sequence to minimize violations of the constraint while providing the desired fluence map and minimized radiation on-time. The method can be applied to SMLC and DLMC systems, and can include adjustment for the tongue-and-groove effect.

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Gainesville, FL, United States of America

Jonathan Gang Li