Acquisition Protocol
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ROSA® Acquisition Protocol If you have any questions, please contact Medtech Customer Service. This acquisition protocol (MRI, CT scan, DTI, PET scan, X-Ray images) has to be followed for image acquisition of a patient undergoing a surgery assisted with the ROSA device.
3D Exams Imaging system
Recommended settings
Modality : CT, MR, PT (mandatory) When using PET-CT exams for planning, first load the CT exam then load the PET exam. Both exams shall have been acquired within the same reference. MRI acquisition 3T and 7T can only be used for exam fusions. Avoid using it as reference exam for laser registration due to image distortion.
Patient orientation : Prone or supine position Contrast agents authorized Table height must remain constant during acquisition
For registration with fiducial markers, include all skin or bone fiducials. For surface matching registration, do not cover the nose and the forehead. External elements (eg. noise and light isolation, strap, etc.) shall not cover the nose and the forehead area, to avoid any skin deformation or imaging degradation. For registration with stereotactic frame, include frame fiducials Do not include table, head clamp or external device in the field. Define the Field of View (FOV) in the Region Of Interest (ROI) to improve the spatial resolution.
Acquisition field
Do not use special characters in patient name Format supported (mandatory): o DICOM 3.0, DICOMDIR o Implicit VR Endian, Explicit VR Little Endian, Explicit VR Big Endian o JPEG Baseline, JPEG Lossless, JPEG-LS-Lossless, JPEG-LS-Lossy Avoid Lossy compressed format, which may impact image quality. Acquisition orientation: o non-tilted, non curved, slices parallel to each other (mandatory) o axial acquisition for registration with stereotactic frame, preferably axial or coronal acquisition for other registration methods. Pixel size, image size, acquisition orientation and table height must remain constant during acquisition Number of slices must be ranging between 40 and 512 o If number of slices inferior to 40, it may impact efficiency of automatic fusion o If number of slices superior to 512, it may impact device latency Slice thickness preferably constant and recommended between 0.6 and 0.8mm. When superior to 1.25mm, the device accuracy is not guaranteed. Contiguous slices : avoid gap and overlap between slices o In case of gap in the acquisition, the software will perform an interpolation which may impact device accuracy. o In case of overlap, the system will ignore the overlapping data which may impact device accuracy. Grayscale pixel data : Monochrome2 (mandatory) Image bit depth: signed and unsigned 8 bits, 16 bits. o In case of bit depth on 32bits, the software will truncate the data bit depth from 32 to 16 bits. Do not import derived series.
Maximum image resolution of 512x512 pixels. Images with higher resolution will be downscaled at import. All slices with same resolution (mandatory)
Acquisition properties
Resolution
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ROSA® Acquisition Protocol Warning about the image quality The accuracy of the registration computation carried out with the ROSA™ device depends on the quality of 3D reconstruction of patient’s face. The areas of the forehead, nose, eyes, temples and ears should be complete and smooth. Those areas should not include any holes and noise as illustrated on the figure. When imaging with markers it’s important to respect a number of markers and a correct positioning on the patient’s head. A minimum of 5 markers must be used for registration. The markers have to be located as illustrated on the figure. The markers must be distributed over the patient's head non-symmetrically and should not be placed in the same plane. It is recommended to place the fiducials near the area of interest and to avoid areas of the head that might move during the procedure.
Placement recommendation for 7 fiducials and for 5 fiducials • Do not use an image acquired with a Gantry tilt.
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ROSA® Acquisition Protocol 2D X-Ray acquisitions Imaging system
Modality: XA, RF, CR (mandatory)
Recommended setting
Contrast agents authorized
Acquisition field
Include all radio-opaque markers of ROSA X-Ray calibration pattern Do not include table, head clamp or external device in the field.
Format supported: DICOM 3.0, JPEG (mandatory) For DICOM 3.0 format : - Implicit VR Endian, Explicit VR Little Endian, Explicit VR Big Endian, JPEG Baseline, JPEG Lossless, JPEG-LS-Lossless, JPEG-LS-Lossy Avoid lossy compressed format, which may impact image quality.
Acquisition properties
- Grayscale pixel data (DICOM format): Monochrome2 - Image bit depth: signed and unsigned 8 bits, 16 bits. In case of bit depth on 32bits, the software will truncate the data bit depth from 32 to 16 bits. For JPEG format: - Pixel encoding: 8 bits, gray level color palette (mandatory)
DTI Exams Imaging system
Acquisition field
Philips Acquiva Number of gradients = 16 As well as the mandatory fields for a MRI or a CT, the following fields must be completed: - Modality : MR - Protocol Name : DTI_medium_iso SENSE - Diffusion Gradient Orientation
PET SCAN Exams
In addition to the mandatory fields for MRI or CT, the following fields must be filled: - Modality : PT
The PT image must be accompanied by a CT acquired in the same referential.
Acquisition field
Other
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