TSG LAKSH Simulation System for Radiotherapy is intended to be used by radiotherapy department of hospitals to simulate patient setup for treatment with external beams. Photon or electron beams of any energy may be simulated. Treatment units of different manufacturers may be used. Treatment unit parameters such as isocentric height, range of beam sizes available, beam modifiers like wedges, blocks, MLCs, etc. are customized by maintaining a library. It interfaces with other equipment for imaging, dose calculation and dose delivery through DICOM 3.0 message exchange protocol.

Simulation for design of Beams
LAKSH Simulation System for Radiotherapy assists doctors and medical physicists to simulate patient setup for design of beams in accordance with intended treatment. When used with a treatment planning system, it assists doctors and medical physicists to arrive at treatment prescription that adequately covers target volume without exceeding dose to the healthy critical organs. Patient and its structures of interest such as target volume and critical organs are reconstructed from CT image dataset of patient volume of interest. Beams from a linear accelerator are similarly reconstructed in relative positions. Position of beams on patient is visualized using software tools, that provide view of patient and its internal organs through radiation beam (Beam Eye View), general view making a beam visible by changing its opacity (Physician’s Eye View), and general view as a 3D scene. Other objects such as couch, gantry, collimator, beam modifiers, etc. may also be included in the reconstructed view of patient setup for treatment with a beam. Opacity and colors may be dynamically modified, so also the view direction. Image based on rendered scene is displayed interactively for assisting a user in evaluating patient setup.

Visualization on DRRs
Additional tools include visualization of Digitally Reconstructed Radiograph (DRR) in the direction of a beam, other forms of radiographs corrected with enhanced view of specified internal structures, coronal, sagital and transverse cut views, view of superimposed dose envelope, point dose in the imaged volume of patient, etc. Tools are available to contour internal structures and patient surface. Auto-contouring based on Hounsfield numbers of voxels provide convenience in segmenting patient and internal structure objects.

Patient is imaged in a treatment position on a DICOM compliant CT scan machine using a flat top along with immobilization devices. Radio-opaque reference marks are placed on the immobilization device to provide reference points for reproducing position of patient on couch of a linear accelerator to correctly align radiation beams. CT image data is acquired in a network through DICOM message exchange procedure.

Results of simulation consist of patient image objects as acquired from CT scan machine, DRRs, DICOM RT objects describing structure set of patient structures of interest, and beam objects. These objects are transferred to treatment planning system for dose calculations. Virtual Simulation system may also receive these objects from treatment planning system for visualization of beam setup. Patient setup instructions are displayed / printed for accepted plan of beams. Patient is setup by reference to the reference marks on the patient immobilization mask using field optics of linear accelerator and computerized console for movement of gantry, collimator and patient couch.

LAKSH Simulation System for Radiotherapy consists of computer software and hardware items and interfaces to CT scan machine. Treatment planning system and linear accelerator. Image data from MRI machine may also be used with certain limitations

DICOMTALKS - Network with DICOM Source VSW22
Receive Images - Negotiates association with DICOM source for receiving DICOM images containing CT / MRI / US / Radiograph images. Negotiates association with DICOM source for an agreed transfer syntax for patient data. Receive images and save the images in a database. Show the contents of database with selection and search capability Show Images - Display images from a series with multiple images on a display screen. Size of any image may be increased / decreased by dragging the border of the image box with mouse. Image may be magnified to full screen. Display of Window Center (WC) and Window Width (WW) for conversion of pixel data to gray scale. Display of pixel value (original value and current gray value), coordinates and distance of the fixed point from the point currently under the mouse cursor. User may dynamically change the position of fixed point used for distance measurement. Window Center (WC) and Window Width (WW) settings may be changed dynamically by dragging the mouse horizontally and vertically on the image. This allows the user to discern structures-of-interest which require different window settings. Window settings with values pre-set to allow visualization of specific organs for CT is provided through click of a button. Specific images from the series may be deleted.

Segmentation of structures
Using auto-contouring function, user may create external contours of the skin for each section. Auto-contouring function allows certain regions to be excluded, like air gaps, to create acceptable contours. Internal structures of interest may be similarly created using auto-contouring function. Manual contouring function by tracing with the mouse cursor is provided for those structures / external skin, not responding to auto-contouring. Editing of contours allowed corrections to make the segmentation acceptable. Segmentation data is saved with the image. This data is made available to Treatment Planning software along with the image data. This saves considerable time of 3D planning and makes planning more reliable and convenient.

Beam Library Interface
A library is created for each energy of photon or electron available for treatment. Energy, Isocenter distance, collimator distance, source size, limits for the beam size, name of the unit, limits for asymmetric jaw movements, etc. are stored. Data for MLC of the unit as per DICOM model is maintained in the library. Data of only one set of MLC is currently supported.

Interface with Treatment Planning System VSW26
Interface support is for ASHA Treatment Planning System or any other system with DICOM RT support. Objects may be imported or exported to treatment planning system. DICOM objects of External Beam Plan Data is sent to the computer of Treatment Planning System are transferred through “push” model of Composite objects store. SOP Classes supported are: RT Dose Storage 1.2.840.10008.5.1.4.1.1.481.2, RT Image Storage 1.2.840.10008.5.1.4.1.1.481.1, RT Plan Storage 1.2.840.10008.5.1.4.1.1.481.5, and RT Structure Set Storage 1.2.840.10008.5.1.4.1.1.481.3 Network and cabling is customized to the installation requirement. Physical network supporting Transmission Control Program / Internet Protocol shall be provided by the hospital. Support for customized formats for External Beam Plan Data is available on request. Desired format shall be provided by the user.

Interface with Linear Accelerator VSW11
Interface support is available for Linear Accelerators with computerized console. Linear Accelerator should support DICOM message exchange for RT objects. DICOM objects of External Beam Plan Data is sent to the computer of Linear Accelerator console through “push” model of Composite objects store. SOP Classes supported are: RT Dose Storage 1.2.840.10008.5.1.4.1.1.481.2, RT Image Storage 1.2.840.10008.5.1.4.1.1.481.1, RT Plan Storage 1.2.840.10008.5.1.4.1.1.481.5, and RT Structure Set Storage 1.2.840.10008.5.1.4.1.1.481.3 Network and cabling is customized to the installation requirement. Physical network supporting Transmission Control Program / Internet Protocol shall be provided by the hospital. Support for customized formats for External Beam Plan Data is available on request. Desired format shall be provided by the user.

Patient Setup for Treatment VSW14
Reference Mark on CT / MRI Image Data Set - CT / MRI image data set of the volume of interest is required for virtual simulation. This data set is the same as required for RT planning, with the addition of radio-opaque marks on the fixation mask of the patient. At lease two radio-opaque marks are required which should be visible to the technologist while setting the patient for treatment. These marks should also be visible on the image data displayed on the computer screen. A “Reference Mark” should be placed on the fixation mask near the middle of the target volume. A “Verification Mark” may be placed towards the longitudinal edge of the target volume. Additional verification marks may be placed if desired. Patient Setup - Patient is with respect to the “Reference Mark” setup for field marking. The Setup is verified with respect to the “Verification Mark”. Detailed setup instruction are displayed / printed.