CArmDRR

MacroModule

genre	Projection
author	MeVis Medical Solutions AG
package	MeVisLab/Standard
definition	CArmDRR.def
see also	DRR, DRRLUT
keywords	c-arm, digitally, reconstructed, radiograph, mip

Purpose

The module CArmDRR provides a C-Arm device specific interface for the module DRR and creates a 2D DRR (Digitally Reconstructed Radiograph) projection of a 3D CT dataset with C-Arm device specific settings.

Usage

This module projects 2D radiographs from 3D datasets by simulating an x-ray beam passing through the 3D voxel cube for each pixel of the output image (“ray casting”). The beam path starts at a “source” and ends at a “detector”. Any voxels that are passed on the way from the source to the detector affect the resulting output image pixel. The type of effect can be selected by the Ray Casting Processing Mode parameter.

• Mean extinction projection: this projection is generated by adding up all voxels passed by the beam and dividing the sum by the number of voxels.
• Maximum extinction projection: this projection uses the highest voxel value found in the beam path as value for the resulting pixel.
• LUT based processing mode: this projection simulates a beam that starts with the intensity 1 and is attenuated by every voxel it passes. The attenuation coefficient of each voxel is defined in an internal look-up table (LUT) an can be modified by some paramters.

By default, the center of the 3D voxel cube is aligned with the center of the source-detector line. This setup can be changed with the Input Image Settings parameters.

Tips

The CArmDRR is intended to work only on CT images. Use a DicomTagModify module to modify the DICOM tag (0008,0060) Modality and set it to CT to get other images working with this module.

Windows

DRR

Input Fields

inImage

name: inImage, type: Image

3D-CT-Image to generate DRR from.

Output Fields

outImage

name: outImage, type: Image

DRR generated from input.

Parameter Fields

Field Index

Apply: Trigger	In Image Offset Reference to: Enum	Ray Casting Beam Resampling: Enum
Auto Apply: Bool	inImageValid: Bool	Ray Casting Processing Mode: Enum
Beam Shape: Integer	Maximum X-Ray Energy In keV: Integer	Resolution Lock Mode: Enum
C-Arm Diameter in mm: Integer	Minimum X-Ray Energy In keV: Integer	Skew: Integer
dontAutoCalcImageSize: Bool	Mode: Enum	Snap In Image To Detector: Bool
Drop Window Center: Integer	Out Image Bits per Pixel: Integer	Tilt: Integer
Drop Window Maximum Height: Double	Out Image Dimension in mm: Vector2	X-Ray Energy in keV: Integer
Image Laterality: String	Out Image Dimension in Pixels: Vector2
In Image Offset in mm: Vector3	Out Image Resolution in lppmm: Float

Visible Fields

Ray Casting Beam Resampling

name: beamResamplingMode, type: Enum, default: Fast - Nearest Neighbour

Defines how the input image voxels are collected that are part of a single beam.

Values:

Title	Name
Fast - Nearest Neighbour	Fast - Nearest Neighbour
Exact - Siddon	Exact - Siddon

Ray Casting Processing Mode

name: processingMode, type: Enum, default: LUT Based Projection

Defines how each passed voxel has an effect on the resulting projected value.

Values:

Title	Name
Mean Extinction Projection	Mean Extinction Projection
Maximum Extinction Projection	Maximum Extinction Projection
LUT Based Projection	LUT Based Projection

Out Image Bits per Pixel

name: outImageBitsPerPixel, type: Integer, default: 12, minimum: 1, maximum: 16

Sets the gray value depth in bits per pixel.

Resolution Lock Mode

name: resolutionLockMode, type: Enum, default: Lock pixel size when resolution changes

Defines which unit shall be left unchanged if the resolution changes.

Values:

Title	Name
pixel size when resolution changes	Lock pixel size when resolution changes
mm size when resolution changes	Lock mm size when resolution changes

C-Arm Diameter in mm

name: cArmDiameter_in_mm, type: Integer, default: 1000

Sets the distance between the beam source and the beam detector in mm.

Tilt

name: tilt, type: Integer, default: 0, minimum: -180, maximum: 180

Sets the rotation of the beam around the z-axis of the 3D input image in degree (+/- 180° rotation).

A positive angle indicates a counter-clockwise rotation and a positive angle indicates a clockwise rotation.

Skew

name: skew, type: Integer, default: 0, minimum: -45, maximum: 45

Sets the rotation of the beam path around the x-axis of the 3D input image in degree.

This parameter is limited to +/- 45°.

Currently disabled.

In Image Offset in mm

name: inImageOffsetIn_mm, type: Vector3, default: 0 0 176

Sets the dislocation in mm of the rotation center which is in the input image’s center by default.

Affects In Image Offset Reference to.

In Image Offset Reference to

name: inImageOffsetMode, type: Enum, default: Beam Path

Defines how the In Image Offset in mm is interpreted.

Values:

Title	Name	Description
World	World	The offset takes effect in direction of the input image’s main axes.
Beam Path	Beam Path	The offset takes effect relative to the beam path. Hint: this option dislocates the output image independetly from the beam path settings. A 100 mm offset in x-direction in this mode mode always pushes the output image 100mm to the right, regardless what beam path rotation is selected. A 100 mm offset in World mode causes different positions of the output image depending on the beam path, because the input image might move out of the beam path.

Snap In Image To Detector

name: inImageSnapToDetector, type: Bool, default: TRUE

If checked, the In Image Offset Reference to is set to Beam and values are being calculated automatically.

The x and y offsets are set to zero (thus adjusting them in image centered to the beam path) and the z offset is calculated with a result that moves the input image as close as possible to the detector without subtending it.

Checking this option makes the Mode available.

Mode

name: inImageSnapToDetectorMode, type: Enum, default: Constant In Image Radius Distance

Defines the mode for automatic parameter calculation.

Values:

Title	Name	Description
Constant In Image Radius Distance	Constant In Image Radius Distance	The distance to the detector is calculated based on the radius (= the maximum distance from the center to the edge) of the input image. This results in a constant distance of the in image center to the detector, regardless of the projection angle. This mode is ideal to get a series comparable images, because there is no angle related perspective distortion.
Minimum Distance	Minimum Distance	The distance from the input image to the detector plane is calculated to the smallest possible value. It depends on the angle of the projection.

Auto Apply

name: autoApply, type: Bool, default: FALSE

If checked, all changes to any field computes the output image anew.

Apply

name: apply, type: Trigger

If pressed, the output image is computed anew.

Image Laterality

name: imageLaterality, type: String, default: U

Sets the laterality of the image with a DICOM tag.

Minimum X-Ray Energy In keV

name: minimumXRayEnergy, type: Integer, default: 60

Sets the minimum X-ray energy for calculating the drop window.

Maximum X-Ray Energy In keV

name: maximumXRayEnergy, type: Integer, default: 160

Sets the maximum X-ray energy for calculating the drop window.

X-Ray Energy in keV

name: XRayEnergy, type: Integer, default: 60, minimum: :field:`minimumXRayEnergy`, maximum: :field:`maximumXRayEnergy`

Sets the simulated X-ray energy in keV.

The closer the X-ray energy in keV value is to the Minimum X-Ray Energy In keV, the steeper the descent of the drop will be. The closer it is to the Maximum X-Ray Energy In keV, the more gently the descent will be (until it disappears completely when energy = max energy):

Graph color	Energy
Yellow	60 keV
Red	90 keV
Blue	160 keV

(Min energy = 60 keV, max energy = 160 keV, drop window center = 1300, drop window max height = 0.2)

Drop Window Center

name: dropWindowCenter, type: Integer, default: 1300

Sets the center in x-direction of the drop window.

The value should be near to the first voxel values for bone tissue. It is scaled automatically when the Out Image Bits per Pixel parameter is changed.

Drop Window Maximum Height

name: dropWindowMaxHeight, type: Double, default: 0.2, minimum: 0, maximum: 1

Sets the limit of the drop window’s height to a maximum value.

The actual drop window height is calculated based on the energy settings (Minimum X-Ray Energy In keV and Maximum X-Ray Energy In keV).

Beam Shape

name: beamShape, type: Integer, default: 0

Defines the shape of the beam. Can be parallel or cone shaped.

Out Image Dimension in Pixels

name: outImageDimension_inPixels, type: Vector2, default: 128 128

Sets the output image’s extent in pixel.

Out Image Dimension in mm

name: outImageDimension_in_mm, type: Vector2, default: 800 800

Sets the output image’s extent in mm.

Out Image Resolution in lppmm

name: outImageResolution_in_lppmm, type: Float, default: 0.079999998

Sets the output image’s extent in lppmm (line pairs per mm, 1 lppmm = 2 pixel per mm).

Hidden Fields

inImageValid

name: inImageValid, type: Bool, default: FALSE

dontAutoCalcImageSize

name: dontAutoCalcImageSize, type: Bool, default: FALSE